SNIP1-Related Neurodevelopmental Disorder

Mendelian MONDO:0013787 Pathograph 78 Show in embeddings browser Neurodevelopmental disorder Autosomal recessive disease Developmental and epileptic encephalopathy

SNIP1-related neurodevelopmental disorder is a severe autosomal recessive multisystem condition caused by biallelic variants in SNIP1 (Smad nuclear interacting protein 1, 1p34.3). It was first delineated in the Old Order Amish, where a single founder missense substitution, NM_024700.4:c.1097A>G p.(Glu366Gly), accounts for every molecularly confirmed case reported to date. The cardinal features are neonatal hypotonia with hypo/areflexia, severe global developmental delay and intellectual disability, universal infantile-onset drug-resistant epilepsy, and a recognisable craniofacial and calvarial gestalt that includes an irregular "lumpy" skull surface, midface hypoplasia, a wide mouth with a thin cupid's bow upper lip, high arched palate, and microretrognathia with or without Pierre Robin sequence. Congenital heart disease, upper airway malacia, feeding failure requiring gastrostomy, and endocrine and sensory involvement complete a multisystem picture with substantial early mortality. SNIP1 is a nuclear protein with an N-terminal nuclear localisation signal and a C-terminal forkhead-associated (FHA) domain. It has three mechanistically distinct jobs that all plausibly contribute to disease: it is a phosphopeptide-reading adaptor that recruits the retention-and-splicing (RES) complex to the activated spliceosome; it is a nuclear co-regulator that sets thresholds for CBP/p300-dependent transcription downstream of TGF-beta/Smad, NF-kappaB and c-MYC; and it directs Polycomb PRC2 genomic occupancy and H3K27me3 turnover to keep neural progenitors alive. The p.(Glu366Gly) substitution sits in the conserved C-terminal region adjacent to the FHA domain; it destabilises the protein and impairs FHA-domain recognition of phosphorylated SF3B1, so SNIP1 function is degraded rather than abolished. Complete loss of SNIP1 is embryonic lethal in mouse, which is why the viable human disorder is attributed to a hypomorphic rather than a null allele.

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Classifications

Harrison's Chapter

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Inheritance

Autosomal recessive biallelic SNIP1 hypomorphism HP:0000007

All reported affected individuals are homozygous for the same founder allele inherited from heterozygous parents; heterozygotes are unaffected. Penetrance is recorded as COMPLETE because segregation in 35 evaluated individuals showed all parents heterozygous, all unaffected siblings heterozygous or wild type, and no unaffected homozygote among more than 5000 Amish controls. Expressivity is nonetheless VARIABLE: substantial phenotypic variation was documented between affected individuals including within sibships, so the same genotype does not predict severity.

Autosomal recessive inheritance Penetrance: COMPLETE Expressivity: VARIABLE

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"confirmed homozygosity of the SNIP1 variant in 35 individuals, with all parents being heterozygous for the variant and all unaffected siblings being heterozygous for the variant or wild type"

Segregation consistent with autosomal recessive inheritance across a large multiplex kindred.

PMID:34570759 SUPPORT Human Clinical

"Substantial phenotypic variation was observed between affected individ- uals, including within sibships"

Direct statement of variable expressivity on a homogeneous genetic background, which is the strongest available argument that modifiers rather than allelic heterogeneity drive severity in this disorder.

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Mechanistic Hypotheses

PRC2 hyperactivity as a druggable node downstream of SNIP1 loss

snip1_prc2_rescue EMERGING

Evidence balance 1 partial

In the mouse neural-progenitor-specific Snip1 knockout, depleting PRC2 is sufficient to reduce apoptosis and brain dysplasia and to partially restore the transcriptional programme. If the same epistasis holds for a hypomorphic allele, PRC2/EZH2 inhibition would be a mechanistically motivated intervention point. The hypothesis is recorded because the rescue experiment is unusually clean epistasis, not because it is close to clinical use.

Deliberately NOT curated as a treatment. Three gaps stand between this result and a therapy: the background is a null rather than the human hypomorph, the rescue window is embryonic and therefore not clinically reachable, and PRC2 depletion was genetic rather than pharmacological. No human, patient-derived, or translational evidence exists.

Show evidence (1 reference)

PMID:37553330 PARTIAL Model Organism

"Depletion of PRC2 is sufficient to reduce apoptosis and brain dysplasia and to partially restore genetic programs in the SNIP1-depleted brain in vivo"

The rescue result the hypothesis rests on. Marked PARTIAL because it is a genetic depletion in a mouse conditional null during embryogenesis, not a pharmacological intervention in the human hypomorphic disorder.

Discussions and Knowledge Gaps

Do conclusions drawn from Snip1-null mouse and zebrafish models transfer to a human hypomorphic allele that is compatible with survival to adulthood?

HUMAN MODEL MISMATCH OPEN snip1_null_vs_hypomorph_model_mismatch

Attached to

pathophysiology#Neural Progenitor Cell Apoptosis and Reduced Neurogenesis pathophysiology#Aberrant PRC2 Genomic Occupancy and H3K27me3 Turnover pathophysiology#Biallelic SNIP1 p.Glu366Gly Founder Substitution

Every in vivo model of SNIP1 loss published to date is a null or conditional null. Snip1 null mice are embryonic lethal; zebrafish RES-component mutants including snip1 fail in early embryogenesis. Humans homozygous for p.(Glu366Gly) survive, in the reported cohort to at least 30 years. That contrast is exactly the reason the human allele is inferred to be hypomorphic, but it also means the models are directionally informative and quantitatively wrong: the cellular lesion they demonstrate (neural progenitor apoptosis, reduced neurogenesis) is almost certainly the right lesion, while its magnitude, timing and tissue distribution in a patient are not established by them. Three further limits: the Nestin-Cre deletion is neural-restricted and therefore cannot model the craniofacial, calvarial, cardiac, airway or endocrine components that make this a recognisable multisystem syndrome; embryonic lethality precludes modelling epilepsy, the single most disabling human feature; and the PRC2-depletion rescue was performed in a null background during embryogenesis. Resolving the mismatch needs a p.(Glu366Gly) knock-in animal, or patient-derived iPSC cortical organoids, neither of which has been published.

Proposed experiments

Snip1 p.Glu366Gly knock-in mouse with multisystem phenotyping

exp_snip1_e366g_knockin_mouse

Generate a constitutive Snip1 p.Glu366Gly knock-in mouse on a defined background and phenotype it for the features that null models cannot reach: postnatal survival, video-EEG for spontaneous seizures, craniofacial and calvarial micro-CT for suture patency and calvarial surface irregularity, echocardiography for septal and outflow lesions, and developmental milestone testing. Compare homozygotes, heterozygotes and wild-type littermates.

Decision criterion

Whether homozygous knock-in animals survive to weaning and reproduce any of the epilepsy, calvarial or cardiac features of the human disorder.

Would support

Survival with seizures and craniofacial or cardiac malformation would confirm p.(Glu366Gly) as a hypomorph sufficient to cause the multisystem syndrome, and would give the field its first tractable disease model.

Would refute

Embryonic or perinatal lethality indistinguishable from the null, or a completely normal homozygote, would both indicate that mouse Snip1 dosage biology does not map onto the human allele.

Patient iPSC-derived cortical organoids with isogenic correction

exp_snip1_patient_ipsc_cortical_organoid

Derive iPSCs from individuals homozygous for p.(Glu366Gly), correct the variant to create isogenic controls, and differentiate both to forebrain cortical organoids. Assay progenitor pool size, cleaved caspase-9 and caspase-3, neuronal output, genome-wide H3K27me3 distribution, and detained-intron splicing efficiency by RNA-seq.

Decision criterion

Whether the human hypomorphic allele reproduces, in human neural tissue, the progenitor apoptosis and splicing defects so far shown only in null-background mouse and zebrafish.

Would support

Increased progenitor apoptosis with caspase-9 activation and measurable detained-intron retention in patient organoids would establish that the mouse and zebrafish mechanisms operate in human cells at the disease allele dosage.

Would refute

Normal progenitor survival and normal splicing in patient organoids would indicate that the null-model mechanism is not the operative one at hypomorphic dosage, and would redirect attention to the transcriptional co-regulation arm or to non-neural tissues.

Pharmacological EZH2 inhibition in a hypomorphic SNIP1 background

exp_snip1_ezh2_inhibition_hypomorph

Test whether small-molecule EZH2 inhibition, rather than genetic PRC2 depletion, rescues progenitor apoptosis in a p.(Glu366Gly) hypomorphic background (knock-in mouse neural progenitors or patient organoids), with a dose-response and a defined treatment window.

Decision criterion

Whether the PRC2-depletion rescue reported in the null background survives the three translations it currently has not made: genetic to pharmacological, null to hypomorph, and embryonic to postnatal.

Would support

Dose-dependent reduction of apoptosis with preserved neurogenesis would convert the PRC2 finding from a mechanistic observation into a genuine therapeutic lead worth curating as a treatment.

Would refute

No rescue, or rescue only at doses that impair normal neurogenesis, would confirm that the PRC2 result should remain a mechanistic hypothesis and not be presented as a therapeutic direction.

Show evidence (3 references)

PMID:34570759 SUPPORT Model Organism

"SNIP1 null mouse models display embryonic lethality indicating that this Amish variant may be unlikely to result in complete loss of func- tion"

States the mismatch directly: the null model is lethal, so it cannot be the right dosage model for a viable human allele.

PMID:34570759 SUPPORT Human Clinical

"Seventy-six per- cent (n = 39) are currently living (age range 6 months to 30 years), while 24% (n = 12) are deceased (age of death between 1 week and 11 years"

Quantifies the human side of the mismatch: survival to 30 years, against embryonic lethality in the null models the mechanism rests on.

PMID:37553330 PARTIAL Model Organism

"The SNIP1-depleted brain exhibits dysplasia with robust induction of caspase 9-dependent apoptosis"

The mechanism whose transferability is in question. Marked PARTIAL because it is obtained by depletion, not by the human hypomorphic allele.

Do the phenotype frequencies curated here generalise beyond the Old Order Amish founder kindred, and does biallelic SNIP1 disease exist outside it?

KNOWLEDGE GAP OPEN snip1_founder_generalisability

Attached to

pathophysiology#Biallelic SNIP1 p.Glu366Gly Founder Substitution phenotypes#Seizure

Every frequency band in this entry derives from a single published cohort of 35 clinically evaluated Old Order Amish individuals, all homozygous for one founder allele, drawn from 21 interrelated families and linkable into a single pedigree. Three consequences follow and are flagged on each banded phenotype's notes field. First, these are genotype-specific frequencies for p.(Glu366Gly) homozygosity, not disease-level frequencies: a different biallelic SNIP1 genotype could present differently, and the source itself records substantial phenotypic variation between individuals including within sibships. Second, the shared genetic and environmental background of a founder community means unmeasured modifiers are shared, which can both inflate apparent consistency and mask features that a heterogeneous cohort would reveal. Third, ascertainment was clinic-based within two Plain-community practices, so mildly affected individuals may be systematically absent. No non-Amish case with biallelic SNIP1 variants has been published, so whether the entity looks the same elsewhere is simply unknown. Resolving this requires GeneMatcher-style ascertainment of biallelic SNIP1 cases outside the founder population.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"While no other biallelic variants in SNIP1 have conclusively been associated with genetic disease to date"

States the absence of any non-founder biallelic SNIP1 disease allele, which is the fact that makes generalisability unknowable from current data.

PMID:34570759 SUPPORT Human Clinical

"Substantial phenotypic variation was observed between affected individ- uals, including within sibships"

Variability on an essentially uniform genetic and community background is the second reason the cohort proportions should not be read as fixed disease frequencies.

Is the human phenotype driven predominantly by the spliceosomal (RES recruitment) arm of SNIP1 function or by the transcriptional co-regulation (CBP/p300, TGF-beta, NF-kappaB, c-MYC) arm?

KNOWLEDGE GAP OPEN snip1_which_arm_drives_disease

Attached to

pathophysiology#Impaired SNIP1 FHA-Domain Phosphopeptide Recognition pathophysiology#Disrupted SNIP1 Co-Regulation of CBP/p300-Dependent Transcription

The entry deliberately curates both arms as parallel branches from the same upstream dosage lesion because the evidence does not yet adjudicate between them. The splicing arm now has the more direct evidence: the E366G variant is shown by name to impair FHA-domain binding to phosphorylated SF3B1 and thereby RES recruitment (PMID:41904131), which is the only published experiment on the actual disease allele in its actual molecular context. The transcriptional arm has stronger patient-derived correlative support: TGF-beta receptor signalling in epithelial-to-mesenchymal transition was the most overrepresented dysregulated Reactome pathway in patient blood (PMID:34570759). But the patient transcriptome study is limited by a sample size of six, by blood as a surrogate for brain, and by an FDR at the pathway level of 0.43, and the authors state the tissue limitation explicitly. Critically, the two arms are not independent: reduced SNIP1 protein abundance (PMID:22279524) degrades both simultaneously, so a clean dissociation would require a separation-of-function allele that has not been reported.

Show evidence (2 references)

PMID:41904131 SUPPORT In Vitro

"Mutations in SNIP1 FHA domain, including the neurodevelopmental disorder-associated E366G variant, impair P-SF3B1 binding, pre-mRNA splicing, and cell viability"

The splicing arm's claim on primacy: the only published experiment performed on the actual disease allele.

PMID:34570759 PARTIAL Human Clinical

"These studies were inherently limited due to the modest number of samples available for study and through the obvious limitations of comparing gene transcriptions profiles in blood, with tis- sues in which clinical outcomes are primarily manifested (brain"

The transcriptional arm's counterweight is patient-derived but the authors state its two limitations themselves, which is precisely why the question remains open. Marked PARTIAL because it qualifies rather than supports.

Does SNIP1-related disorder include a genuine progressive neurodegenerative component, or is all apparent progression seizure-related secondary injury?

OPEN QUESTION OPEN snip1_neurodegeneration_question

Attached to

pathophysiology#Detained-Intron Splicing Brake Dysregulation in Neurons pathophysiology#Status Epilepticus pathophysiology#Hypoxic-Ischaemic Secondary Brain Injury

Conditional Snip1 deletion in mouse cerebellum decreases detained-intron splicing efficiency and causes frank neurodegeneration (PMID:37027487), raising the possibility that the human hypomorph also drives slow neuronal loss. Against that, the human clinical description attributes regression and the late spastic quadriplegic picture to hypoxic injury from long-term untreated or unrecognised seizures rather than to intrinsic degeneration, and survivors reach 30 years of age. No longitudinal imaging or neuropathology in genotyped individuals has been published, so the two explanations are not yet separable. This distinction is not academic: it determines whether aggressive early seizure control should be expected to preserve trajectory (secondary injury model) or merely to slow it (degenerative model).

Show evidence (2 references)

PMID:37027487 PARTIAL Model Organism

"Snip1 conditional knockout in the cerebellum decreases DI splicing efficiency and causes neurodegeneration"

The case for a degenerative component. Marked PARTIAL because it is a conditional null in mouse cerebellum and has no demonstrated human correlate.

PMID:34570759 PARTIAL Human Clinical

"Individuals identified in late childhood/adolescence are often diagnosed with a mixed tone spastic quadriplegic cerebral palsy, likely reflecting hypoxic injury after long-term untreated/unrecognise d seizures"

The competing explanation: the clinical authors attribute apparent progression to acquired seizure-related hypoxic injury rather than to intrinsic degeneration. Marked PARTIAL because it is the authors' attribution rather than a measurement distinguishing the two models.

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Pathophysiology

Biallelic SNIP1 p.Glu366Gly Founder Substitution

Homozygosity for NM_024700.4:c.1097A>G, p.(Glu366Gly) in exon 4 of SNIP1 (1p34.3) is the single molecular lesion underlying every molecularly confirmed case. Glu366 lies in the conserved C-terminal 30 amino acids, immediately adjacent to the forkhead-associated (FHA) domain, within a low-complexity or intrinsically disordered region that is strongly conserved across species orthologues. The variant is a hypomorph rather than a null: Snip1 knockout mice are embryonic lethal, so a complete loss-of-function allele would not be compatible with the viable human phenotype.

SNIP1 hgnc:30587

nucleus GO:0005634

Downstream

Reduced SNIP1 Protein Abundance and Altered Nuclear Distribution The substituted protein is transcribed normally but is unstable and redistributes within the nucleus from a punctate to an aggregated pattern.

Impaired SNIP1 FHA-Domain Phosphopeptide Recognition The change sits next to the FHA domain and degrades its ability to read phosphorylated partner proteins.

Show evidence (3 references)

PMID:22279524 SUPPORT Human Clinical

"SNIP1 Glu366 is highly conserved and the p.Glu366Gly mutation is in the C-terminus where SNIP1 interacts with c-Myc"

Original identification of the causal substitution and its position in the C-terminal protein-interaction region.

PMID:34570759 SUPPORT Human Clinical

"Multiple species alignment confirms this amino acid is highly conserved across species ortho- logs (Fig 1G) and is located close to the FHA domain at the SNIP1 C-terminus"

Places the substitution structurally adjacent to the FHA domain and confirms deep evolutionary conservation of the residue.

PMID:34570759 SUPPORT Model Organism

"SNIP1 null mouse models display embryonic lethality indicating that this Amish variant may be unlikely to result in complete loss of func- tion"

The argument for hypomorphism rather than a null allele. Classified MODEL_ORGANISM because the underlying observation is a mouse knockout phenotype (sourced by the authors to the Mouse Genome Database) rather than a human finding.

Reduced SNIP1 Protein Abundance and Altered Nuclear Distribution

Transcript levels of the mutant allele are comparable to wild type, so the lesion acts post-transcriptionally. Overexpressed mutant protein is markedly less abundant than wild type on Western blot and adopts an aggregated rather than a punctate nuclear distribution, indicating impaired protein stability and impaired assembly into nuclear transcriptional and splicing complexes. This dosage reduction is the shared upstream cause of both the splicing and the transcriptional arms of the disease.

SNIP1 hgnc:30587

nuclear speck GO:0016607

Downstream

Defective RES Complex Recruitment to the Activated Spliceosome Less SNIP1 protein is available to act as the phosphorylation-dependent bridge that loads the RES complex onto the activating spliceosome.

Disrupted SNIP1 Co-Regulation of CBP/p300-Dependent Transcription Reduced SNIP1 abundance releases the threshold SNIP1 normally sets on CBP/p300-dependent transcription and removes its support for c-MYC.

Aberrant PRC2 Genomic Occupancy and H3K27me3 Turnover Less SNIP1 is available to direct Polycomb PRC2 to its target loci and to instruct H3K27me3 turnover there.

Show evidence (3 references)

PMID:22279524 SUPPORT In Vitro

"However, Snip1 p.Glu353Gly (corresponding to human p.Glu366Gly) had a more aggregated appearance (Figure 3, E) and Western blotting proved it unstable (Figure 3, F); its band density was 84.9 69.6% SD lower than wild-type (n = 4 independent transfections each"

Direct experimental demonstration that the orthologous mouse substitution destabilises the protein and mislocalises it within the nucleus. The "84.9 69.6% SD" rendering is a PDF extraction artifact for "84.9 +/- 9.6% SD".

PMID:22279524 SUPPORT In Vitro

"Reverse transcriptase-PCR suggests that the Snip1 c.1058A.G (corresponding to human SNIP1 c.1097A.G) transcript is expressed at levels comparable to wild-type"

Excludes a transcript-level mechanism (no nonsense-mediated decay, no splicing disruption of the SNIP1 transcript itself), localising the defect to protein stability.

PMID:22279524 SUPPORT In Vitro

"Wild-type protein localized to the nucleus with a punctate appearance, consistent with its involvement in transcrip- tional complexes"

Establishes the wild-type nuclear pattern against which the mutant aggregated pattern is scored.

Impaired SNIP1 FHA-Domain Phosphopeptide Recognition

The forkhead-associated (FHA) domain is a phosphothreonine/phosphoserine reader module. In the spliceosome cycle, CDK11 phosphorylates the threonine-proline repeats of SF3B1 during spliceosome activation, and the SNIP1 FHA domain recognises phosphorylated SF3B1. Disease-associated FHA domain mutations, explicitly including the neurodevelopmental disorder-associated E366G variant, impair that phosphopeptide binding. This is the most direct available molecular explanation of what the Amish allele actually breaks.

SNIP1 hgnc:30587

phosphoserine residue binding GO:0050815 ↓ DECREASED

Downstream

Defective RES Complex Recruitment to the Activated Spliceosome Loss of phospho-SF3B1 recognition removes the docking step that loads RES onto the activating spliceosome.

Show evidence (2 references)

PMID:41904131 SUPPORT In Vitro

"Mutations in SNIP1 FHA domain, including the neurodevelopmental disorder-associated E366G variant, impair P-SF3B1 binding, pre-mRNA splicing, and cell viability"

Names the disease variant explicitly and demonstrates the specific biochemical deficit: loss of phosphorylated-SF3B1 binding, with downstream splicing and viability consequences.

PMID:41904131 SUPPORT In Vitro

"We further demonstrate that P-SF3B1 is recognized by forkhead-associated (FHA) domain of SNIP1, which promotes recruitment of retention and splicing (RES) complex during spliceosome activation"

Establishes the normal molecular function that the E366G substitution degrades: FHA-mediated reading of phospho-SF3B1 to recruit RES.

Defective RES Complex Recruitment to the Activated Spliceosome

SNIP1 is a component of the human activated (B-act) spliceosome and forms the retention-and-splicing (RES) complex together with BUD13 and RBMX2. RES is required for efficient intron definition and splicing of a defined subset of short, GC-rich introns. Acute SNIP1 depletion disrupts RES incorporation and causes widespread splicing defects, and loss of RES components in vertebrates produces a global intron-splicing defect with a marked neural phenotype.

SNIP1 hgnc:30587

RES complex GO:0070274

spliceosomal complex GO:0005681

Downstream

Widespread Pre-mRNA Splicing Dysregulation Failure to load RES onto the activating spliceosome degrades splicing fidelity and efficiency transcriptome-wide.

Show evidence (3 references)

PMID:41904131 SUPPORT In Vitro

"Acute SNIP1 depletion disrupts RES incorporation, causes widespread splicing defects, and promotes hyperphosphorylation of SF3B1 by CDK11"

Loss-of-SNIP1 experiment showing that RES incorporation is SNIP1-dependent and that its failure produces transcriptome-wide splicing defects.

PMID:29360106 SUPPORT In Vitro

"Structure of the human activated spliceosome in three conformational states"

Structural confirmation that SNIP1 is a bona fide constituent of the human activated spliceosome, which is the basis for treating the splicing arm as a physiological SNIP1 role rather than an incidental interaction. Only the title-level assertion is quoted because the fetched record for this structural paper is title/metadata level; the SNIP1-in-B-act claim is independently attributed in PMID:34570759.

PMID:29969449 PARTIAL Model Organism

"Transcriptomic analysis of bud13, snip1 (pml1) and rbmx2 (snu17) mutants revealed a global defect in intron splicing, with strong mis-splicing of a subset of introns"

Vertebrate loss-of-function evidence that snip1 is required for normal intron splicing as part of RES. Marked PARTIAL because zebrafish snip1 mutants are functional nulls with early embryonic lethality, whereas the human allele is hypomorphic, so severity does not transfer.

Widespread Pre-mRNA Splicing Dysregulation

Reduced RES loading degrades splicing of RES-dependent introns, which are characteristically short, GC-rich and flanked by GC-depleted exons, i.e. introns that depend on intron definition rather than exon definition. The net effect is a transcriptome-wide shift in splicing efficiency rather than a single mis-spliced gene product, which is consistent with the multisystem phenotype.

mRNA splicing, via spliceosome GO:0000398 ↓ DECREASED

Downstream

Detained-Intron Splicing Brake Dysregulation in Neurons SNIP1 additionally sets the pause point for post-transcriptional splicing of detained introns, a neuron-relevant subset of the same defect.

Altered Neurodevelopmental Gene Expression Programme Degraded splicing efficiency changes the abundance of mature transcripts for developmentally critical genes.

Show evidence (2 references)

PMID:29969449 SUPPORT Model Organism

"We found these RES-dependent introns were short, rich in GC and flanked by GC depleted exons, all of which are features associated with intron definition"

Defines the sequence features of the intron subset whose splicing depends on RES, and therefore on SNIP1.

PMID:34570759 SUPPORT Human Clinical

"as part of the retention and splicing (RES) complex, which plays a crucial role in splicing and retention of pre-mRNA"

The clinical report's own statement of the splicing arm, connecting the disorder to spliceosomopathy biology. The quotation starts mid-sentence to avoid a bracketed numeric citation marker in the extracted text; the preceding clause reads "SNIP1 also forms a component of the human activated spliceosome".

Detained-Intron Splicing Brake Dysregulation in Neurons

Beyond bulk splicing, SNIP1 together with RNPS1 forms a molecular brake that pauses the spliceosome at the B-act state on detained introns, holding intron-detaining transcripts in the nucleus as a rapidly deployable mRNA pool. Conditional Snip1 deletion in mouse cerebellum reduces detained-intron splicing efficiency and causes neurodegeneration, identifying neurons as a tissue in which the timing of detained-intron release is SNIP1-dependent and functionally critical.

neuron CL:0000540

regulation of alternative mRNA splicing, via spliceosome GO:0000381 ↕ DYSREGULATED

Downstream

Altered Neurodevelopmental Gene Expression Programme Mis-timed release of detained introns changes the neuronal transcript repertoire available at critical developmental and homeostatic windows.

Show evidence (2 references)

PMID:37027487 PARTIAL Model Organism

"Snip1 conditional knockout in the cerebellum decreases DI splicing efficiency and causes neurodegeneration"

Establishes a neuron-specific, SNIP1-dependent splicing function whose loss is sufficient to damage the CNS. Marked PARTIAL because this is a conditional null in mouse cerebellum, not the human hypomorphic allele, and because the human disorder is a developmental encephalopathy rather than a documented progressive neurodegeneration.

PMID:37027487 SUPPORT In Vitro

"we suggest that post-transcriptional DI splicing is paused at the Bact state, an active spliceosome but not catalytically primed, which depends on Smad Nuclear Interacting Protein 1 (SNIP1) and RNPS1 (a serine-rich RNA binding protein) interaction"

Defines the specific molecular role, spliceosome pausing at the B-act state on detained introns, that requires SNIP1.

Disrupted SNIP1 Co-Regulation of CBP/p300-Dependent Transcription

SNIP1 sets a threshold for CBP/p300-dependent transcriptional activation. Its N-terminus binds both Smad4 and the coactivator CBP/p300, and SNIP1 competitively inhibits both Smad4/p300 complex formation and NF-kappaB (RelA) access to the C/H1 domain of CBP/p300. Its C-terminus binds c-MYC, stabilising it against proteasomal degradation and bridging a c-MYC/p300 complex. Reduced SNIP1 abundance therefore simultaneously releases restraint on TGF-beta/Smad and NF-kappaB output and withdraws support from c-MYC, which is the transcriptional arm of this disease.

SNIP1 hgnc:30587

regulation of transcription by RNA polymerase II GO:0006357 ↕ DYSREGULATED

transcription coactivator activity GO:0003713 ↕ DYSREGULATED

Downstream

Derepressed TGF-beta/Smad Transcriptional Output Loss of SNIP1 restraint on Smad4/p300 complex formation raises TGF-beta pathway transcriptional output.

Derepressed NF-kappaB Transcriptional Output Loss of SNIP1 competition for the CBP/p300 C/H1 domain raises NF-kappaB dependent transcription.

Altered Neurodevelopmental Gene Expression Programme Withdrawal of SNIP1 support for c-MYC and the combined pathway shifts remodel the developmental gene expression programme.

Aberrant Distal Limb and Digit Development Disruption of c-MYC or CBP/p300 signalling in mouse produces abnormal development of the distal limbs as well as of brain and skull.

Show evidence (6 references)

PMID:10887155 SUPPORT In Vitro

"Overexpression of full-length SNIP1 or its amino terminus is sufficient to inhibit multiple gene responses to TGF-beta and CBP/p300, as well as the formation of a Smad4/p300 complex"

Original demonstration of SNIP1 as a nuclear inhibitor of CBP/p300 acting on TGF-beta transcriptional responses.

PMID:10887155 SUPPORT In Vitro

"SNIP1 is a nuclear inhibitor of CBP/p300 and its level of expression in specific cell types has important physiological consequences by setting a threshold for TGF-beta-induced transcriptional activation involving CBP/p300"

States the dosage-threshold model explicitly, which is precisely why a hypomorphic reduction in SNIP1 abundance is expected to be pathogenic.

PMID:11567019 SUPPORT In Vitro

"SNIP1 inhibits NF-kappa B signaling by competing for its binding to the C/H1 domain of CBP/p300 transcriptional co-activators"

Establishes the competitive mechanism by which SNIP1 restrains NF-kappaB at the shared CBP/p300 coactivator.

+ 3 more references

Derepressed TGF-beta/Smad Transcriptional Output

With less SNIP1 available to restrain Smad4/p300 complex formation, TGF-beta pathway transcriptional output rises. Blood transcriptome analysis of six affected individuals found TGF-beta receptor signalling in epithelial-to-mesenchymal transition to be the single most overrepresented dysregulated Reactome pathway, and identified two downregulated TGF-beta pathway genes (BMPR1A and ACVR1C). Because disorders of TGF-beta/BMP signalling characteristically produce craniofacial, skeletal and cardiovascular malformation, this node is the most plausible mechanistic route to the non-neurological half of the syndrome.

transforming growth factor beta receptor signaling pathway GO:0007179 ↕ DYSREGULATED

Downstream

Aberrant Craniofacial and Calvarial Morphogenesis Perturbed TGF-beta/BMP output in cranial neural crest derivatives and calvarial osteogenic fronts disturbs facial and skull development.

Aberrant Cardiac and Outflow Tract Morphogenesis TGF-beta/BMP signalling is required for septation, valvulogenesis and aortic arch remodelling.

Aberrant Laryngeal and Pharyngeal Cartilage Development TGF-beta/BMP pathway disorders characteristically involve connective tissue and cartilage, the tissues whose failure produces airway malacia.

Show evidence (3 references)

PMID:34570759 SUPPORT Human Clinical

"the most overrepresented pathway was the TGF-β receptor signalling in epithelial to mesenchyme pathway with differential expression of three genes (upregulation of PARD3 and downregulation of F11R and RPS27A"

Patient-derived transcriptomic evidence that the TGF-beta arm is the dominant dysregulated pathway in this disorder.

PMID:34570759 PARTIAL Human Clinical

"defining two downregulated genes (BMPR1A and ACVR1C) involved in the TGF-β pathway"

Named TGF-beta pathway genes dysregulated in patient blood. Marked PARTIAL because blood is not the affected tissue and the authors explicitly flag that limitation.

PMID:34570759 SUPPORT Human Clinical

"Genetic variants leading to disruption of the TGF-β/BMP molecular sig- nalling pathway have been implicated in the pathogenesis of a number of inherited disorders, in particular connective tissue disorders associated with craniofacial (e.g. cleft palate and cra- niosynostosis), cardiovascular..."

Establishes the expected organ-system consequences of TGF-beta/BMP pathway disruption, which map onto the craniofacial, cardiovascular and skeletal features of this disorder.

Derepressed NF-kappaB Transcriptional Output

SNIP1 normally competes with the RelA subunit of NF-kappaB for the C/H1 domain of CBP/p300. Reduced SNIP1 therefore raises NF-kappaB-dependent transcription. Two consequences are relevant here. In brain, inappropriate increases in NF-kappaB signalling have been shown to initiate epileptogenesis in mouse. In heart, SNIP1 deficiency worsens pressure-overload hypertrophy through NF-kappaB, and blocking NF-kappaB rescues it, which is notable because left ventricular non-compaction occurs in this disorder.

canonical NF-kappaB signal transduction GO:0007249 ↑ INCREASED

Downstream

Cortical Network Hyperexcitability Increased NF-kappaB and TGF-beta/Smad2 signalling in brain are each sufficient to initiate epileptogenesis in mouse.

Impaired Myocardial Stress Adaptation Loss of SNIP1 restraint on NF-kappaB in cardiomyocytes worsens hypertrophic remodelling and contractile dysfunction.

Show evidence (3 references)

PMID:11567019 SUPPORT In Vitro

"SNIP1 inhibits NF-kappa B signaling by competing for its binding to the C/H1 domain of CBP/p300 transcriptional co-activators"

Mechanistic basis for NF-kappaB derepression when SNIP1 is reduced.

PMID:22279524 PARTIAL Model Organism

"Inappropriate increases in TGF- b/Smad2 signaling and in NF- kB signaling in the mouse brain have been shown to independently initiate epileptogenesis"

Links the predicted signalling derangement to the cardinal phenotype. Marked PARTIAL because this is a mouse-derived inference cited by the authors, not a measurement made in SNIP1 patients.

PMID:27912208 PARTIAL Model Organism

"SNIP1 deficiency significantly exacerbated aortic banding-induced cardiac hypertrophy, fibrosis, and contractile dysfunction, whereas cardiac-specific overexpression of SNIP1 markedly recovered pressure overload-induced cardiac hypertrophy and fibrosis"

Shows a SNIP1-dose-dependent cardiac phenotype mediated by NF-kappaB. Marked PARTIAL because it is a pressure-overload mouse model of acquired hypertrophy, not a model of the germline human disorder.

Aberrant PRC2 Genomic Occupancy and H3K27me3 Turnover

A third, epigenetic arm of SNIP1 function, established in mouse neural-progenitor-specific knockout. SNIP1 facilitates the genomic occupancy of the Polycomb repressive complex PRC2 and instructs H3K27me3 turnover at target genes; the SNIP1 target genes concerned are ones that promote cell survival and neurogenesis, and SNIP1 activity at them is itself influenced by TGF-beta and NF-kappaB signalling, which ties this arm back to the transcriptional co-regulation arm. Loss of this function mislocalises repressive H3K27 marks and silences a survival programme. The decisive evidence is a rescue: depleting PRC2 is sufficient to reduce apoptosis and brain dysplasia in the SNIP1-depleted brain.

PcG protein complex GO:0031519

histone H3K27 trimethyltransferase activity GO:0140951 ↕ DYSREGULATED

Downstream

Neural Progenitor Cell Apoptosis and Reduced Neurogenesis Mislocalised PRC2/H3K27me3 silences the SNIP1-dependent survival and neurogenesis programme, triggering caspase-9-dependent apoptosis.

Altered Neurodevelopmental Gene Expression Programme Aberrant H3K27me3 deposition is a second route, alongside splicing and CBP/p300 co-regulation, to a distorted developmental transcriptome.

Show evidence (3 references)

PMID:37553330 SUPPORT Model Organism

"Further, SNIP1 facilitates the genomic occupancy of Polycomb complex PRC2 and instructs H3K27me3 turnover at target genes"

Establishes the PRC2-directing function of SNIP1 in the developing brain.

PMID:37553330 SUPPORT Model Organism

"Depletion of PRC2 is sufficient to reduce apoptosis and brain dysplasia and to partially restore genetic programs in the SNIP1-depleted brain in vivo"

Epistasis rescue placing PRC2 downstream of SNIP1 and causally between SNIP1 loss and the apoptotic brain phenotype. This is the strongest evidence that the PRC2 arm is mechanistically load-bearing rather than correlative.

PMID:37553330 SUPPORT Model Organism

"Mechanistically, SNIP1 regulates target genes that promote cell survival and neurogenesis, and its activities are influenced by TGFβ and NFκB signaling pathways"

Connects this epigenetic arm to the TGF-beta and NF-kappaB arms curated separately, indicating the arms are coupled rather than independent.

Neural Progenitor Cell Apoptosis and Reduced Neurogenesis

The pivotal cellular hub of the neurological arm. SNIP1 promotes neural progenitor cell survival and neurogenesis, and the SNIP1-depleted brain exhibits dysplasia with robust induction of caspase-9-dependent apoptosis, i.e. death by the intrinsic mitochondrial pathway rather than by death receptors. The same convergence is reproduced in a second vertebrate by a completely different route: zebrafish RES-complex mutants, including snip1, show increased cell death in the brain and a decrease in differentiated neurons. Two independent organisms and two independent mechanistic entry points (PRC2 and splicing) therefore arrive at the same cellular lesion.

neural progenitor cell CL:0011020 radial glial cell CL:0000681

intrinsic apoptotic signaling pathway GO:0097193 ↑ INCREASED cerebral cortex neuron differentiation GO:0021895 ↓ DECREASED

Downstream

Structural Brain Malformation and White Matter Abnormality Depletion of the progenitor pool and loss of newly generated neurons produce brain dysplasia, cortical thinning and reduced white matter.

Show evidence (3 references)

PMID:37553330 SUPPORT Model Organism

"we report that Smad nuclear interacting protein 1 (SNIP1) promotes neural progenitor cell survival and neurogenesis and is, therefore, integral to brain development"

Defines the normal SNIP1 function whose loss produces this node.

PMID:37553330 SUPPORT Model Organism

"The SNIP1-depleted brain exhibits dysplasia with robust induction of caspase 9-dependent apoptosis"

Identifies both the tissue outcome (dysplasia) and the specific apoptotic route (caspase-9, i.e. intrinsic/mitochondrial).

PMID:29969449 SUPPORT Model Organism

"The mutants showed a marked neural phenotype with increased cell death in the brain and a decrease in differentiated neurons"

Independent cross-species corroboration in zebrafish snip1/RES mutants, reached through the splicing arm rather than the PRC2 arm.

Altered Neurodevelopmental Gene Expression Programme

The convergent output of the splicing and transcriptional arms is a reproducible shift in the expression of genes with established neurodevelopmental and neuropathological roles. Whole-transcriptome sequencing of six affected individuals identified 75 significantly upregulated and 109 significantly downregulated genes. Of the most strongly altered transcripts with a known clinical association, 24 had a previously established association with neurological disease, and five of those (ROBO1, SOX5, CNTNAP2, PAFAH1B1 and TSNARE1) are seizure genes. ROBO1, the most upregulated gene, is an axon guidance receptor; PAFAH1B1 (LIS1) is a canonical neuronal migration gene.

regulation of transcription by RNA polymerase II GO:0006357 ↕ DYSREGULATED

Downstream

Impaired Axon Guidance and Neuronal Migration Dysregulation of ROBO1, PAFAH1B1 and related genes perturbs axonal pathfinding and cortical neuronal migration.

Cortical Network Hyperexcitability Dysregulation of CNTNAP2, TSNARE1, SYT1 and other synaptic and neuron-glia genes lowers the threshold for seizure generation.

Neural Progenitor Cell Apoptosis and Reduced Neurogenesis Under-expression of the SNIP1-dependent survival and neurogenesis programme is what makes progenitors die rather than differentiate.

Show evidence (3 references)

PMID:34570759 SUPPORT Human Clinical

"Differentially expressed genes with a false discovery rate (FDR) adjusted p-value of <0.05 identified a list of 75 significantly upregulated genes, and 109 significantly downregulated genes"

Quantifies the transcriptomic perturbation measured directly in affected individuals.

PMID:34570759 SUPPORT Human Clinical

"This includes five genes (ROBO1, SOX5, CNTNAP2, PAFAH1B1 and TSNARE1) associated with seizures, the cardinal feature of SNIP1-related disorder"

Directly connects the measured expression changes to the cardinal phenotype through independently established seizure genes.

PMID:34570759 SUPPORT Human Clinical

"Our gene transcript studies in affected individuals define altered gene expression profiles of a number of molecules with well-defined neurodevelopmental and neuropathological roles, potentially explaining clinical outcomes"

The authors' own framing of this node as the mechanistic bridge between the molecular lesion and the clinical outcome.

Impaired Axon Guidance and Neuronal Migration

ROBO1, the most upregulated transcript in affected individuals, is a neural cell adhesion molecule family axon guidance receptor, and PAFAH1B1 is among the dysregulated genes associated with brain structural abnormality. Perturbation of axon guidance and cortical neuronal migration is the cell-biological step that best accounts for the observed white matter, corpus callosum and cortical ribbon abnormalities.

neuron CL:0000540 neural progenitor cell CL:0011020

axon guidance GO:0007411 ↕ DYSREGULATED neuron migration GO:0001764 ↕ DYSREGULATED

Downstream

Structural Brain Malformation and White Matter Abnormality Failed pathfinding and migration produce the hypomyelination, thin corpus callosum, ventriculomegaly and irregular cortical ribbon seen on MRI.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Of these ROBO1 (roundabout guidance receptor 1), the gene identi- fied to be most upregulated in affected individuals with SNIP1-related disorder, is a member of the neural cell adhesion molecule (NCAM) family involved in axonal migration"

Identifies the specific axon guidance receptor most strongly dysregulated in patients.

PMID:34570759 PARTIAL Human Clinical

"includes two other genes (PAFAH1B1 and TOR1AIP1) associated with brain structural abnor- malities"

PAFAH1B1 is the classical lissencephaly neuronal migration gene; its dysregulation supports a migration component. Marked PARTIAL because expression change in blood is an indirect proxy for a brain developmental process.

Structural Brain Malformation and White Matter Abnormality

Neuroimaging is abnormal in essentially all individuals assessed. The reported spectrum comprises hydrocephalus, ventriculomegaly, white matter abnormalities, thin corpus callosum, hypomyelination, an irregular cortical ribbon that follows the undulating inner skull contour, Chiari malformation, absence of the septum pellucidum, hypoplastic optic nerves and septo-optic dysplasia. The cortical ribbon finding is mechanistically interesting because it couples the brain and calvarial phenotypes.

neuron migration GO:0001764 ↓ DECREASED

Downstream

Severe Global Developmental Impairment Structural maldevelopment of cortex and white matter is the anatomical substrate of the profound psychomotor delay.

Ventriculomegaly Enlarged ventricles, with or without frank hydrocephalus, on MRI.

Abnormal Cerebral White Matter Morphology White matter abnormality and hypomyelination on MRI.

Hypoplasia of the Corpus Callosum A thin corpus callosum, reported in both published series.

Septo-Optic Dysplasia Midline forebrain malformation at the severe end of the imaging spectrum.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Neuro- imaging was available for 18 individuals, all confirmed to have abnormalities, including hydrocephalus, ventriculomegaly, white matter abnormalities, thin corpus callosum, hypo- myelination, irregular cortical ribbon, Chiari malformation, absence of the septum pelluci- dum, hypoplastic..."

Full imaging spectrum with an explicit denominator: 18 of 18 imaged individuals had abnormalities.

PMID:22279524 SUPPORT Human Clinical

"Magnetic resonance imaging reveals ventriculomegaly, thin corpus callosum, white matter abnormalities, and an undulating or ‘‘lumpy’’ skull surface (Figure 3, E). The cortical ribbon follows the irregular skull contour"

Independent description of the imaging phenotype in the original three probands, including the coupling of cortical ribbon shape to the abnormal calvarium.

Cortical Network Hyperexcitability

The combination of derepressed NF-kappaB and TGF-beta/Smad2 signalling in brain, dysregulated synaptic and neuron-glia genes (CNTNAP2, TSNARE1, SYT1), and structural cortical maldevelopment produces a diffusely hyperexcitable cortical network. EEG is abnormal in all individuals assessed, with diffuse background slowing and frequent focal or multifocal discharges and no single characteristic pattern.

neuron CL:0000540

modulation of chemical synaptic transmission GO:0050804 ↕ DYSREGULATED

Downstream

Infantile-Onset Drug-Resistant Epilepsy A hyperexcitable cortical network generates the multifocal, multi-type, treatment-refractory seizures that define the disorder.

EEG Abnormality The electrographic readout of the hyperexcitable network: diffuse background slowing with frequent focal or multifocal discharges, abnormal in every individual assessed and with no characteristic pattern. Wired from this node rather than from the seizure node because the abnormality is a property of the network itself and is present interictally.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"EEG was abnormal in all individuals assessed, with no characteristic pattern, findings included diffuse background slowing and frequent focal or multifocal discharges"

Electrophysiological confirmation of diffuse, non-localising cortical dysfunction rather than a single epileptogenic focus.

PMID:22279524 SUPPORT Human Clinical

"temporal regions typically begin by 6 months of age and are accompanied by focal or generalized seizures that can manifest as dystonic posturing, drop attacks, myoclonic jerks, or generalized tonic-clonic events. Multiple intractable seizure types can afflict an individual patient"

Dates the onset of electrographic hyperexcitability to the first six months of life and documents the multiple concurrent seizure types a single hyperexcitable network generates. The quotation begins mid-sentence because a figure caption is interleaved at that point in the extracted PDF text; the preceding clause reads "Multifocal spike-wave discharges from central, occipital, and".

Infantile-Onset Drug-Resistant Epilepsy

Every affected individual develops epilepsy. Seizure types include focal and generalised intractable seizures (myoclonic, absence, tonic-clonic) of infantile or childhood onset, and multiple intractable seizure types can afflict a single patient. Seizures may present initially as apnoea or breath-holding spells, and subclinical seizures occur. Febrile illness, sleep deprivation and hypoglycaemic episodes are recognised triggers. No antiepileptic medication has been identified that consistently provides effective seizure control.

Downstream

Status Epilepticus Refractory seizures progress to status epilepticus with consequent developmental regression and, in some, permanent motor deficit.

Seizure The clinical seizure phenotype itself, universal in this disorder.

Drug-Resistant Epilepsy No anticonvulsant provides consistent control, and several individuals have multiple drug resistant epilepsy.

Apnea In some infants the first seizure manifestation is apnoea or breath-holding, a seizure-driven route to apnoea distinct from the airway-malacia route.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Seizures are a cardinal feature of the disorder with all affected individuals developing epilepsy. Seizure types include focal and generalised intractable seizures (myoclonic, absence, tonic-clonic) of infantile or childhood onset"

Universality, seizure semiology and age at onset in the 35-individual cohort.

PMID:34570759 SUPPORT Human Clinical

"There were no antiepileptic medications identified that consistently provide effective seizure control (defined as manageable frequency of sei- zures) and several individuals display multiple drug resistant epilepsy"

Establishes drug resistance as a defining property rather than an occasional complication, which is the basis for the treatment section's caution about disease-specific anticonvulsant recommendations.

Status Epilepticus

Refractory epilepsy in this disorder is not merely a comorbidity; it is an active driver of further neurological loss, and status epilepticus is the acute event through which that loss is delivered. Some individuals suffered severe developmental regression following status epilepticus, two with subsequent permanent hemiparesis. Preventing status epilepticus is named by the cohort authors as an explicit goal of anticonvulsant optimisation, which makes this the acquired and potentially preventable entry point to the acquired component of the phenotype.

Downstream

Hypoxic-Ischaemic Secondary Brain Injury Prolonged seizure activity is the proximate cause of the secondary hypoxic-ischaemic insult the authors invoke to explain the acquired motor and developmental deficit.

Developmental Regression Loss of previously acquired skills following status epilepticus. Wired from this node rather than from the downstream injury node because the source attributes the regression directly to the status epilepticus event without asserting an intervening hypoxic mechanism.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Some individuals suf- fered severe developmental regression following status epilepticus, with two reported to have subsequent permanent hemiparesis"

Documents seizure-driven regression and fixed motor deficit as acquired events on top of the congenital lesion. The "suf- fered" spelling is a PDF extraction artifact.

PMID:34570759 SUPPORT Human Clinical

"maintain seizure control, and prevent status epilepticus and consequent"

The authors name prevention of status epilepticus, and of the developmental regression that follows it, as an explicit management target, which is why this event is modelled as its own node.

Hypoxic-Ischaemic Secondary Brain Injury

The tissue-level consequence of prolonged and inadequately controlled seizure activity. Individuals identified in late childhood or adolescence are often diagnosed with mixed-tone spastic quadriplegic cerebral palsy that the cohort authors attribute to hypoxic injury after long-term untreated or unrecognised seizures rather than to a primary pyramidal lesion. This is the acquired, and therefore potentially preventable, component of the phenotype.

Downstream

Spastic Tetraplegia The mixed-tone spastic quadriplegic picture in late-ascertained individuals, attributed by the authors to hypoxic injury rather than to a primary pyramidal lesion.

Severe Global Developmental Impairment Seizure-related hypoxic injury compounds the developmental deficit already set by the structural brain malformation.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

Explains why late-ascertained individuals carry a cerebral palsy label and frames early seizure control as neuroprotective. The "unrecognise d" spelling is a PDF extraction artifact.

Severe Global Developmental Impairment

The convergent clinical endpoint of the neurological arm. Global developmental delay and hypotonia with hyporeflexia are present in all affected individuals, and developmental delay is characterised as severe and non-verbal. Most affected individuals nonetheless achieve independent ambulation between 3 and 10 years, and some communicate with signs, gestures and sounds, so the disorder is severe but not uniformly without motor progress.

Downstream

Global Developmental Delay The clinical manifestation of the impaired neurodevelopmental endpoint.

Intellectual Disability The cognitive manifestation, universally severe and non-verbal.

Hypotonia Central hypotonia is present from the neonatal period in all affected individuals.

Hyporeflexia Weak or absent tendon reflexes accompany the hypotonia in all affected individuals.

Neonatal Feeding Failure and Aspiration Risk Poor feeding from birth is universal and is the entry point to the nutritional and pulmonary morbidity of the disorder.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Global developmen tal delay (severe, non-verbal) 100"

Table 1 row giving the frequency and qualitative severity of the developmental phenotype in 35 evaluated individuals. Word-internal spacing is a PDF extraction artifact.

PMID:34570759 SUPPORT Human Clinical

"Most affected individuals achieved independent ambu- lation (age range 3–10 years), and some communicate with signs, gestures and sounds"

Qualifies the severity: motor milestones are delayed but usually attained, which matters for prognostic counselling.

Aberrant Craniofacial and Calvarial Morphogenesis

Cranial neural crest derived facial skeleton and the membranous calvarium are both affected. Skull morphology ranges from normocephaly to severe multi-suture craniosynostosis with a cloverleaf skull, and characteristically includes an irregular skull surface with variable calvarial thickness and bony dysplasia. Facial features comprise midface hypoplasia, a wide mouth with downturned corners and thin cupid's bow upper lip, large tongue, high arched palate, microretrognathia with or without Pierre Robin sequence and cleft palate, malocclusion, small upturned bulbous nose, long palpebral fissures, and proptosis where craniosynostosis is present.

migratory cranial neural crest cell CL:0000008 osteoblast CL:0000062

embryonic cranial skeleton morphogenesis GO:0048701 ⚠ ABNORMAL

Downstream

Abnormal Skull Morphology The calvarial arm: irregular skull surface, variable calvarial thickness and bony dysplasia in every affected individual.

Craniosynostosis Premature suture fusion at the severe end of the calvarial spectrum.

Cloverleaf Skull The most extreme calvarial outcome: multi-suture fusion producing a trilobar skull.

Proptosis A consequence of the reduced orbital volume produced by craniosynostosis, and reported only in individuals who have it.

Midface Retrusion Hypoplasia of the cranial-neural-crest-derived midfacial skeleton.

High Palate Palatal shelf morphology abnormality, present in every affected individual.

Wide Mouth Wide mouth with downturned corners and a thin cupid's bow upper lip.

Macroglossia Large tongue, part of the oral component of the gestalt.

Micrognathia Microretrognathia from mandibular hypoplasia.

Pierre-Robin Sequence Mandibular hypoplasia severe enough to displace the tongue and obstruct palatal closure, the classical sequence.

Cleft Palate Failure of palatal shelf fusion, reported within the Pierre Robin sequence subset.

Bulbous Nose Small upturned bulbous nose, a consistent element of the facial gestalt.

Long Palpebral Fissure Periorbital component of the craniofacial gestalt.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Skull morphological abnormalities were observed and ranged from normocephaly to severe multi-suture craniosynostosis with Cloverleaf appearance of the skull in five individ- uals, and included an irregular skull surface with variable calvarium thickness and bony dys- plasia"

Defines the calvarial spectrum, including the specific count of five individuals with cloverleaf skull.

PMID:34570759 SUPPORT Human Clinical

"Craniofacial features (Fig 1A–1D) include midface hypoplasia, a wide mouth with downturned corners and thin cupids bow upper lip, large tongue, high arched palate, microre- trognathia (Pierre Robin sequence with or without cleft palate in three patients), malocclusion, small upturned bulbous..."

The complete craniofacial gestalt as described in the 35-individual cohort.

Aberrant Cardiac and Outflow Tract Morphogenesis

Congenital cardiac malformation affects a majority of individuals and spans the septation, valvular and aortic arch compartments: hypoplastic left heart syndrome, aortic stenosis and bicuspid aortic valve, aortic coarctation, aortic root dilatation, atrial and ventricular septal defects, patent ductus arteriosus, pulmonary artery stenosis and mitral regurgitation. This distribution is characteristic of perturbed TGF-beta/BMP signalling in cardiac neural crest and second heart field derivatives.

cardiac muscle cell CL:0000746

heart morphogenesis GO:0003007 ⚠ ABNORMAL

Downstream

Abnormal Heart Morphology The full congenital cardiac lesion spectrum, spanning septation, valvular and aortic arch compartments.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"a variable spectrum of congenital cardiac defects (60% of individuals), including hypoplastic left heart syndrome, aortic stenosis and bicuspid aortic valve, aortic coarctation, aortic root dilatation, atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosus (PDA),..."

Frequency and full lesion spectrum of congenital heart disease in the cohort.

Impaired Myocardial Stress Adaptation

Distinct from the structural congenital lesions, a minority of individuals develop cardiomyopathy, specifically left ventricular non-compaction. Mouse work showing that SNIP1 deficiency exacerbates and SNIP1 overexpression rescues pressure-overload hypertrophy through NF-kappaB provides a candidate mechanism for a myocardial rather than a morphogenetic contribution, though this link has not been demonstrated in patients.

cardiac muscle cell CL:0000746

Downstream

Left Ventricular Noncompaction Cardiomyopathy The myocardial phenotype seen in a minority, distinct from the structural congenital lesions.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"12% of affected individuals developed cardiomyopathy (left ventricular non- compaction"

Documents the cardiomyopathy subtype and its frequency in the cohort.

PMID:27912208 PARTIAL Model Organism

"our findings demonstrated that SNIP1 had protective effects in pressure overload-induced pathological cardiac hypertrophy via inhibition of nuclear factor-κB signaling"

Candidate NF-kappaB-dependent myocardial mechanism. Marked PARTIAL because it is an acquired-hypertrophy model in mouse and no myocardial mechanism has been shown in individuals with the SNIP1 founder variant.

Aberrant Laryngeal and Pharyngeal Cartilage Development

Three quarters of individuals have upper airway abnormalities: laryngomalacia, pharyngomalacia and subglottic stenosis of variable severity, producing a weak cry, stridor and apnoea and occasionally requiring tracheostomy and home oxygen. The common feature of malacia and subglottic narrowing is inadequate laryngeal and pharyngeal cartilage support, and TGF-beta/BMP pathway disruption characteristically affects connective tissue and cartilage, which is why this node is placed downstream of the TGF-beta arm. The mechanism has not been demonstrated directly in this disorder and the placement is an inference, flagged as such below.

chondrocyte CL:0000138

Downstream

Laryngomalacia Inadequate supraglottic cartilage support collapses the airway on inspiration.

Subglottic Stenosis Cricoid-level narrowing, the fixed rather than dynamic form of the airway lesion.

Apnea Airway obstruction is the second, non-seizure route to apnoea in this disorder.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Affected individuals commonly displayed upper airway respiratory difficulties in the neonatal period, including laryngomalacia, pharyngomalacia and subglottic stenosis of var- iable severity, causing a weak cry, stridor and apnea, occasionally requiring tracheostomy and supplementary home oxygen"

Documents the airway phenotype, its neonatal onset and its severity range.

PMID:34570759 PARTIAL Human Clinical

The basis for placing the airway phenotype downstream of the TGF-beta arm. Marked PARTIAL because the quotation establishes that TGF-beta/BMP disruption causes connective tissue disease in general, not that it causes the airway malacia in this specific disorder.

Aberrant Distal Limb and Digit Development

Distal limb findings comprise short hands with tapered fingers in just over half of individuals, plus brachydactyly, broad thumbs, single palmar crease, congenital talipes equinovarus, pes planus and toenail hypoplasia. The discovery paper's mechanistic rationale is that disruption of c-MYC or CBP/p300 signalling in mice produces abnormal development of brain, skull, craniofacial bones and distal limbs, which is precisely the combination seen here; the brachydactyly syndromes are separately TGF-beta pathway disorders.

chondrocyte CL:0000138

Downstream

Tapered Finger Short hands with tapered fingers, the commonest distal limb finding.

Brachydactyly Shortened digits, the phenotype shared with the TGF-beta pathway brachydactyly syndromes.

Broad Thumb Broad thumbs, reported in both published series.

Talipes Equinovarus Congenital clubfoot, the distal lower-limb component.

Hypoplastic Toenails Nail hypoplasia, a distal appendage patterning defect.

Show evidence (2 references)

PMID:22279524 PARTIAL Model Organism

"Disruption of c-Myc or CBP/p300 signaling in mice can result in abnormal development of the brain, skull, craniofacial bones, and distal limbs"

The discovery paper's own mechanistic rationale linking the SNIP1 transcriptional co-regulation arm to the observed distal limb findings. Marked PARTIAL because it is a mouse-derived inference cited by the authors, not a measurement in SNIP1 patients.

PMID:34570759 SUPPORT Human Clinical

"Other dysmorphic features include brachydactyly, broad thumbs, single palmar crease, congenital talipes equinovarus, pes planus, toenail hypoplasia and pectus excavatum"

Enumerates the distal limb and appendage findings this node accounts for.

Neonatal Feeding Failure and Aspiration Risk

Poor feeding in the neonatal period is universal, and pulmonary aspiration with or without a gastrostomy tube affects 46%. This is the single most actionable node in the entry: elective gastrostomy is one of two interventions the cohort authors single out as able to reduce hospitalisations, alleviate suffering and prolong life. The proximate mechanism is not established, and more than one contributor is plausible (central hypotonia with poor suck and swallow coordination, upper airway malacia, and gastroesophageal reflux are all documented in the same individuals), so no single mechanism is asserted.

Downstream

Feeding Difficulties Universal poor feeding from the neonatal period.

Aspiration Pulmonary aspiration, the principal driver of respiratory morbidity and hospitalisation.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Poor feeding in the neonatal period is universal and many require a gastrostomy tube to both aid nutrition and reduce risk of aspiration pneumonia"

Establishes universality and the direct link from feeding failure to aspiration pneumonia risk.

PMID:34570759 SUPPORT Human Clinical

"Intrauterine growth retardation (IUGR) and failure to thrive was also common"

Places the postnatal nutritional failure in the context of prenatal growth restriction.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

Cardiovascular 1

Abnormal Heart Morphology FREQUENT Abnormal heart morphology HP:0001627

Frequency band FREQUENT derived from 60% in the founder cohort (PMID:34570759 Table 1). Umbrella node for congenital heart disease of any type; the individual lesions are not separately banded because per-lesion denominators are not published. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Congenital heart defects (ASD, VSD, aortic coarctation ) 60"

Table 1, n = 35 evaluated individuals, 60%, which falls in the FREQUENT (30-79%) band. Spacing before the parenthesis is a PDF extraction artifact.

PMID:22279524 SUPPORT Human Clinical

"Physical anomalies found in some patients include subglottic stenosis, aortic stenosis, bicuspid aortic valve"

Independent documentation of left-sided outflow lesions in the original probands.

Digestive 3

Feeding Difficulties OBLIGATE Feeding difficulties HP:0011968

Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Feeding difficulties 100"

Table 1, n = 35 evaluated individuals.

PMID:34570759 SUPPORT Human Clinical

"Poor feeding in the neonatal period is universal and many require a gastrostomy tube to both aid nutrition and reduce risk of aspiration pneumonia"

Corroborates universality and states the management consequence.

Gastroesophageal Reflux Gastroesophageal reflux HP:0002020

No band; reported qualitatively without a denominator.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Gastrointestinal features reported include gastroesophageal reflux, paraoesophageal hernia (type III), intestinal malrota- tion, hepatomegaly and umbilical and inguinal hernias"

Lists the gastrointestinal spectrum of the disorder.

Intestinal Malrotation Intestinal malrotation HP:0002566

No band; reported qualitatively without a denominator.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Gastrointestinal features reported include gastroesophageal reflux, paraoesophageal hernia (type III), intestinal malrota- tion, hepatomegaly and umbilical and inguinal hernias"

Names intestinal malrotation among the reported gastrointestinal features.

Ear 1

Conductive Hearing Impairment OCCASIONAL Conductive hearing impairment HP:0000405

Frequency band OCCASIONAL derived from the 21% Table 1 figure (20% in the prose) in the founder cohort. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Failed newborn hearing screen (conductiv e loss) 21"

Table 1, n = 35 evaluated individuals, 21%. Word-internal spacing is a PDF extraction artifact.

PMID:34570759 SUPPORT Human Clinical

"Auditory features include chronic otitis media and hearing loss, with 20% failing newborn hearing screening"

Prose corroboration (20%, versus 21% in the table) and identification of chronic otitis media as a contributing factor.

Endocrine 1

Hypothyroidism OCCASIONAL Hypothyroidism HP:0000821

Frequency band OCCASIONAL derived from 25% in the founder cohort. Founder-cohort derived.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Hypothyroid ism 25"

Table 1, n = 35 evaluated individuals, 25%. Word-internal spacing is a PDF extraction artifact.

Eye 2

Proptosis Proptosis HP:0000520

No band; the source conditions this finding on craniosynostosis without giving a numerator.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"long palpebral fissures and proptosis (in individuals with cranio- synostosis"

Conditions proptosis explicitly on the presence of craniosynostosis.

Strabismus FREQUENT Strabismus HP:0000486

Frequency band FREQUENT derived from the composite 45% Table 1 row for "horizontal nystagmus and/or strabismus"; the strabismus-specific rate is therefore at or below 45%. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Horizontal nystagmus and/or strabismu s 45"

Table 1, n = 35 evaluated individuals, 45%. Word-internal spacing is a PDF extraction artifact.

PMID:22279524 SUPPORT Human Clinical

"Examination typically reveals a subdued child with strabismus, slow horizontal nystagmus, hypotonia, and weak or absent tendon reflexes"

Independent documentation of strabismus and nystagmus in the original probands.

Head and Neck 10

Craniosynostosis Craniosynostosis HP:0001363

Deliberately unbanded. The only quotable count in the source, five individuals, is specifically the severe multi-suture cloverleaf subgroup, and that count now carries its own band on the Cloverleaf Skull phenotype. Craniosynostosis of any degree has no published denominator of its own: milder craniosynostosis is subsumed in the 100% "abnormal skull shape" row of Table 1, which is not a craniosynostosis row. Per this entry's one-band, one-denominator rule the band is omitted here rather than inherited from the cloverleaf subgroup, which would understate the true proportion.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"ranged from normocephaly to severe multi-suture craniosynostosis with Cloverleaf appearance of the skull in five individ- uals"

Establishes that craniosynostosis occurs in this disorder and spans a range up to severe multi-suture fusion. The "individ- uals" spelling is a PDF extraction artifact.

Cloverleaf Skull OCCASIONAL Cloverleaf skull HP:0002676

Frequency band OCCASIONAL derived from 5/35 = 14%. Founder-cohort derived: the denominator is the 35 comprehensively evaluated individuals of the Old Order Amish p.Glu366Gly kindred, which is largely one extended family, so this is a kindred proportion and not a general disease frequency. Split out of the Craniosynostosis phenotype so that the 5/35 count bands the subgroup it actually counts.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"ranged from normocephaly to severe multi-suture craniosynostosis with Cloverleaf appearance of the skull in five individ- uals"

Gives the count of individuals with the severe cloverleaf form, 5 of 35. The "individ- uals" spelling is a PDF extraction artifact.

High Palate OBLIGATE High palate HP:0000218

Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort derived.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"High arched palate 100"

Table 1, n = 35 evaluated individuals.

Wide Mouth OBLIGATE Wide mouth HP:0000154

Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Wide mouth with cupids bow upper lip 100"

Table 1, n = 35 evaluated individuals.

PMID:22279524 SUPPORT Human Clinical

"Dysmorphic features that evolve over time include a bulbous nose, wide mouth and tongue, broad jaw with protuberant angles, short hands, short tapered fingers, and broad thumbs"

Independent description of the evolving dysmorphic gestalt in the original probands.

Midface Retrusion Midface retrusion HP:0011800

No band. Midface hypoplasia is described qualitatively in the craniofacial narrative and does not appear as a numbered row in Table 1, so no denominator is available.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Craniofacial features (Fig 1A–1D) include midface hypoplasia, a wide mouth with downturned corners and thin cupids bow upper lip"

Names midface hypoplasia as a craniofacial feature of the disorder.

Micrognathia FREQUENT Micrognathia HP:0000347

Frequency band FREQUENT derived from the 30% Table 1 figure in the founder cohort, which sits at the lower boundary of the 30-79% band. Founder-cohort derived.

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PMID:34570759 SUPPORT Human Clinical

"Micrognath ia with/wi thout Pierre Robin sequence 30"

Table 1, n = 35 evaluated individuals, 30%. Word-internal spacing is a PDF extraction artifact.

Cleft Palate Cleft palate HP:0000175

No band. The source gives "with or without cleft palate in three patients", so the cleft-specific numerator is unknown even within the three-patient subset.

Show evidence (1 reference)

PMID:34570759 PARTIAL Human Clinical

"microre- trognathia (Pierre Robin sequence with or without cleft palate in three patients"

Cleft palate is reported only as an optional component of Pierre Robin sequence in three patients, so the number of individuals with a cleft is not stated. Marked PARTIAL for that reason.

Macroglossia Macroglossia HP:0000158

No band; large tongue is not a numbered Table 1 row.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"thin cupids bow upper lip, large tongue, high arched palate"

Names large tongue among the craniofacial features.

Bulbous Nose Bulbous nose HP:0000414

No band; not a numbered Table 1 row.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"malocclusion, small upturned bulbous nose, long palpebral fissures and proptosis"

Names the nasal morphology in the craniofacial description.

Long Palpebral Fissure Long palpebral fissure HP:0000637

No band; not a numbered Table 1 row.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"malocclusion, small upturned bulbous nose, long palpebral fissures and proptosis"

Names long palpebral fissures in the craniofacial description.

Limbs 3

Broad Thumb Broad thumb HP:0011304

No band; not a numbered Table 1 row.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Other dysmorphic features include brachydactyly, broad thumbs, single palmar crease, congenital talipes equinovarus, pes planus, toenail hypoplasia and pectus excavatum"

Names broad thumbs among the additional dysmorphic features.

Brachydactyly Brachydactyly HP:0001156

No band; not a numbered Table 1 row.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Other dysmorphic features include brachydactyly, broad thumbs, single palmar crease, congenital talipes equinovarus, pes planus, toenail hypoplasia and pectus excavatum"

Names brachydactyly among the additional dysmorphic features.

Talipes Equinovarus OCCASIONAL Talipes equinovarus HP:0001762

Frequency band OCCASIONAL derived from 13% in the founder cohort. Founder-cohort derived.

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PMID:34570759 SUPPORT Human Clinical

"Congenital talipes equinovarus 13"

Table 1, n = 35 evaluated individuals, 13%.

Metabolism 1

Hypoglycemia OCCASIONAL Hypoglycemia HP:0001943

Frequency band OCCASIONAL derived from 21% in the founder cohort. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Hypoglycaem ia 21"

Table 1, n = 35 evaluated individuals, 21%. Word-internal spacing is a PDF extraction artifact.

PMID:34570759 SUPPORT Human Clinical

"Endocrine abnormalities including hypoglyce- mia, hypothyroidism, hypothermia and dyshormonogenesis were identified in a small propor- tion of patients"

Places hypoglycaemia in the wider endocrine spectrum, which also includes hypothermia and dyshormonogenesis.

Musculoskeletal 3

Hypotonia OBLIGATE Hypotonia HP:0001252

Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort derived, not a general disease frequency.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Hypotonia 100"

Table 1, n = 35 evaluated individuals.

PMID:22279524 SUPPORT Human Clinical

"Affected neonates are hypotonic and feed poorly"

Establishes neonatal onset in the original probands.

Scoliosis OCCASIONAL Scoliosis HP:0002650

Frequency band OCCASIONAL derived from the composite spinal-abnormality figure (23% in prose, 21% in Table 1) in the founder cohort. Scoliosis is one of three pooled findings, so its individual rate is lower. Founder-cohort derived.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Spinal abnormalities were seen in 23% including sacral dimple, tethered cord and scoliosis in older children"

Composite spinal abnormality frequency of 23% in the prose (21% in Table 1), with scoliosis named as an age-dependent component.

Pectus Excavatum Pectus excavatum HP:0000767

No band; reported qualitatively.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Other features include pectus excavatum and hypoplastic ribs in a single individual"

Names pectus excavatum among the thoracic findings.

Nervous System 12

Global Developmental Delay OBLIGATE Global developmental delay HP:0001263

Frequency band OBLIGATE derives from 35/35 in the founder cohort (PMID:34570759 Table 1). This is a single extended Amish kindred homozygous for one allele, so the band describes that genotype in that population and is not a general disease frequency.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Global developmen tal delay (severe, non-verbal) 100"

Table 1, n = 35 evaluated individuals, 100% affected. Word-internal spacing is a PDF extraction artifact.

Intellectual Disability Intellectual disability HP:0001249

No band assigned. Intellectual disability is named as cardinal but is not a separate row in the Table 1 frequency tabulation, which reports "global developmental delay (severe, non-verbal)" instead. Rather than reuse the developmental delay denominator for a different construct, the band is omitted.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"The cardinal clinical features of the condition include hypotonia, global developmental delay, intellectual disability, seizures, and a characteristic craniofacial appearance"

Names intellectual disability among the cardinal features of the disorder.

PMID:22279524 SUPPORT Human Clinical

"Some children show behavioral responses to language, but they do not socially engage or follow verbal commands"

Qualitative characterisation of the cognitive and communicative level in the original probands.

Seizure OBLIGATE Seizure HP:0001250

Frequency band OBLIGATE derives from 35/35 in the founder cohort (PMID:34570759 Table 1, "Seizures 100%"), supported by the prose statement that all affected individuals develop epilepsy. Founder-cohort derived.

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PMID:34570759 SUPPORT Human Clinical

"Seizures are a cardinal feature of the disorder with all affected individuals developing epilepsy"

Explicit statement of 100% penetrance of epilepsy in the evaluated cohort, corroborating the Table 1 figure of 100%.

PMID:34570759 SUPPORT Human Clinical

"Seizures can be triggered or exacerbated by febrile illness, sleep deprivation and hypoglycemic episodes"

Documents the modifiable seizure triggers, which is directly actionable in management.

EEG Abnormality EEG abnormality HP:0002353

No frequency band is asserted. The source states the finding was present in all individuals assessed but does not give the number assessed, so there is no denominator; consistent with the rest of this entry a band is omitted rather than inferred from the 35-individual founder cohort denominator, which would misrepresent an unstated assessment subset. Split out of the Drug-Resistant Epilepsy phenotype, which previously carried this snippet under an HP:0002353 binding that did not match its own name.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"EEG was abnormal in all individuals assessed, with no characteristic pattern, findings included diffuse background slowing and frequent focal or multifocal discharges"

Establishes that the electrographic abnormality is present in all assessed individuals and describes its non-specific character.

Ventriculomegaly Ventriculomegaly HP:0002119

No band for ventriculomegaly specifically. The Table 1 row "abnormal brain MRI (ventriculomegaly, white matter defects) 50%" pools imaging findings across the whole cohort of 35, whereas the prose reports 18/18 abnormal among those actually imaged. Those two denominators are not interchangeable, and no ventriculomegaly-specific numerator is published, so no band is asserted.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

18/18 imaged individuals had abnormalities; ventriculomegaly is named among them.

PMID:22279524 SUPPORT Human Clinical

"Magnetic resonance imaging reveals ventriculomegaly, thin corpus callosum, white matter abnormalities, and an undulating or ‘‘lumpy’’ skull surface"

Independent MRI description in the original probands.

Abnormal Cerebral White Matter Morphology Abnormal cerebral white matter morphology HP:0002500

No band, for the same denominator reason given on the Ventriculomegaly entry.

Show evidence (1 reference)

PMID:22279524 SUPPORT Human Clinical

"Magnetic resonance imaging reveals ventriculomegaly, thin corpus callosum, white matter abnormalities, and an undulating or ‘‘lumpy’’ skull surface"

Documents white matter abnormality and thin corpus callosum on MRI.

Hypoplasia of the Corpus Callosum Hypoplasia of the corpus callosum HP:0002079

No band; no callosum-specific numerator is published.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"white matter abnormalities, thin corpus callosum, hypo- myelination, irregular cortical ribbon"

Names thin corpus callosum among the imaging findings.

Autism FREQUENT Autism HP:0000717

Frequency band FREQUENT derived from the composite 75% behavioural-problems row, which pools irritability, autistic features and ADHD. The autism-specific rate is therefore at or below 75%; the band is carried here because autism is the named formal diagnosis. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Behavioural problem s (irritability , autistic features, ADHD) 75"

Table 1, n = 35 evaluated individuals, 75% for the composite behavioural category. Word-internal spacing is a PDF extraction artifact.

PMID:34570759 SUPPORT Human Clinical

"Behavioural diagnoses include autism spectrum disorder and attention deficit disorder"

Names the formal behavioural diagnoses made in the cohort.

Attention Deficit Hyperactivity Disorder Attention deficit hyperactivity disorder HP:0007018

No independent band; the 75% denominator is composite and is carried on the Autism entry rather than asserted twice.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Behavioural diagnoses include autism spectrum disorder and attention deficit disorder"

Names attention deficit disorder as a behavioural diagnosis in the cohort.

Sleep Disturbance Sleep disturbance HP:0002360

No band; described qualitatively without a denominator. Clinically important because sleep deprivation is itself a documented seizure trigger in this disorder.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Irritability and sleep/wake dysregula- tion are seen in infancy and early childhood"

Documents sleep/wake dysregulation as an early feature.

Developmental Regression Developmental regression HP:0002376

No band; "some individuals" is given without a denominator.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Some individuals suf- fered severe developmental regression following status epilepticus, with two reported to have subsequent permanent hemiparesis"

Documents regression and its proximate cause.

Tethered Cord Tethered cord HP:0002144

No independent band; the 23% denominator is composite and is carried on the Scoliosis entry rather than asserted three times.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Spinal abnormalities were seen in 23% including sacral dimple, tethered cord and scoliosis in older children"

Names tethered cord among the spinal abnormalities.

Respiratory 2

Apnea Apnea HP:0002104

No separate band. Apnoea is folded into the 75% "upper airway abnormalities" Table 1 row and also occurs as a seizure manifestation, so no clean denominator exists for apnoea as such.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"In some infants, sei- zures initially presented as apnea or breath-holding spells and subclinical seizures were detected in six individuals"

Documents seizure-related apnoea and the occurrence of subclinical seizures, the basis for the early-EEG recommendation.

Aspiration FREQUENT Aspiration HP:0002835

Frequency band FREQUENT derived from 46% in the founder cohort. Founder-cohort derived.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Pulmonary aspiration with/withou t gastrostom y tube 46"

Table 1, n = 35 evaluated individuals, 46%. Word-internal spacing is a PDF extraction artifact.

Growth 1

Small for Gestational Age FREQUENT Small for gestational age HP:0001518

Frequency band FREQUENT derived from 54% in the founder cohort. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Small for gestational age 54"

Table 1, n = 35 evaluated individuals, 54%.

PMID:34570759 SUPPORT Human Clinical

"Intrauterine growth retardation (IUGR) and failure to thrive was also common"

Corroborating prose linking prenatal growth restriction to postnatal failure to thrive.

Other 13

Drug-Resistant Epilepsy Refractory drug response HP:0020174

No frequency band. Pharmacoresistance is described qualitatively ("several individuals") without a denominator, so per curation policy the band is omitted rather than guessed. HPO has no "drug-resistant epilepsy" class, so the binding is HP:0020174 Refractory drug response (a descendant of HP:0000118 Phenotypic abnormality via HP:0020169 Abnormal drug response), with the epilepsy context carried by the phenotype name and description. A previous revision bound this phenotype to HP:0002353 EEG abnormality, which is a different concept rather than a broader one; the electrographic finding now has its own phenotype entry.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

Direct statement of pharmacoresistance in the cohort. The "sei- zures" spelling is a PDF extraction artifact.

Hyporeflexia OBLIGATE Hyporeflexia HP:0001265

Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Hyporeflexi a 100"

Table 1, n = 35 evaluated individuals. Word-internal spacing is a PDF extraction artifact.

PMID:22279524 SUPPORT Human Clinical

"Examination typically reveals a subdued child with strabismus, slow horizontal nystagmus, hypotonia, and weak or absent tendon reflexes"

Independent description of the combined hypotonic-hyporeflexic examination findings.

Abnormal Skull Morphology OBLIGATE Abnormal skull morphology HP:0000929

Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Abnormal skull shape (irregular surface, craniosyno stosis) 100"

Table 1, n = 35 evaluated individuals. Word-internal spacing is a PDF extraction artifact.

PMID:22279524 SUPPORT Human Clinical

"Symptomatic epilepsy and skull dysplasia. Affected neonates are hypotonic and feed poorly"

The original descriptive disease name pairing epilepsy with skull dysplasia.

Pierre-Robin Sequence OCCASIONAL Pierre-Robin sequence HP:0000201

Frequency band OCCASIONAL derived from 3/35 = 9% in the founder cohort. Founder-cohort derived.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"microre- trognathia (Pierre Robin sequence with or without cleft palate in three patients"

Explicit count of three individuals with Pierre Robin sequence.

Left Ventricular Noncompaction Cardiomyopathy OCCASIONAL Left ventricular noncompaction cardiomyopathy HP:0011664

Frequency band OCCASIONAL derived from 12% in the founder cohort. Founder-cohort derived.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"12% of affected individuals developed cardiomyopathy (left ventricular non- compaction"

Prose figure of 12%, matching the Table 1 cardiomyopathy row, with the subtype named.

Laryngomalacia FREQUENT Laryngomalacia HP:0001601

Frequency band FREQUENT derived from the 75% Table 1 figure for "upper airway abnormalities", of which laryngomalacia is the named exemplar. The band therefore applies to the composite airway category rather than to laryngomalacia in isolation. Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Upper airway abnormalit ies (laryngoma lacia, apnoea, stridor) 75"

Table 1, n = 35 evaluated individuals, 75%. Word-internal spacing is a PDF extraction artifact.

PMID:34570759 SUPPORT Human Clinical

Full description of the airway phenotype and its management burden.

Subglottic Stenosis Subglottic stenosis HP:0001607

No band; reported as occurring in "some patients" without a denominator.

Show evidence (1 reference)

PMID:22279524 SUPPORT Human Clinical

"Physical anomalies found in some patients include subglottic stenosis, aortic stenosis, bicuspid aortic valve"

Documents subglottic stenosis in the original probands.

Umbilical Hernia OCCASIONAL Umbilical hernia HP:0001537

Frequency band OCCASIONAL derived from the 21% Table 1 figure, which pools umbilical and inguinal hernias; the umbilical-specific rate is therefore lower than 21%. Founder-cohort derived.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Hernias (umbilica l, inguinal) 21"

Table 1, n = 35 evaluated individuals, 21%. Word-internal spacing is a PDF extraction artifact.

Horizontal Nystagmus Horizontal nystagmus HP:0000666

No independent band; the only published denominator (45%) pools nystagmus with strabismus and is carried on the Strabismus entry to avoid asserting the same denominator twice for two different features.

Show evidence (1 reference)

PMID:22279524 SUPPORT Human Clinical

"Examination typically reveals a subdued child with strabismus, slow horizontal nystagmus, hypotonia, and weak or absent tendon reflexes"

Describes horizontal nystagmus as a typical finding on examination.

Septo-Optic Dysplasia Septo-optic dysplasia HP:0100842

No band; no numerator is published for this finding.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Chiari malformation, absence of the septum pelluci- dum, hypoplastic optic nerves and septo-optic dysplasia"

Names septo-optic dysplasia and the associated midline anomalies among the imaging findings.

Spastic Tetraplegia Spastic tetraplegia HP:0002510

No band; "often" is given without a denominator.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

Documents the late-ascertainment spastic quadriplegic picture and attributes it to seizure-related hypoxic injury. The "unrecognise d" spelling is a PDF extraction artifact.

Tapered Finger FREQUENT Tapered finger HP:0001182

Frequency band FREQUENT derived from the composite 54% Table 1 row for "short hands with tapered fingers". Founder-cohort derived.

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"Short hands with tapered fingers 54"

Table 1, n = 35 evaluated individuals, 54%.

PMID:22279524 SUPPORT Human Clinical

"broad jaw with protuberant angles, short hands, short tapered fingers, and broad thumbs"

Independent description of the distal limb findings in the original probands.

Hypoplastic Toenails Hypoplastic toenails HP:0001800

No band; not a numbered Table 1 row.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"congenital talipes equinovarus, pes planus, toenail hypoplasia and pectus excavatum"

Names toenail hypoplasia among the additional dysmorphic features.

🧬

Genetic Associations

SNIP1 (Biallelic SNIP1 variants are the sole established cause of this disorder. MONDO:0013787 carries a single RO:0004003 (has material basis in germline mutation in) relation, to HGNC:30587 (SNIP1), which was re-verified against the MONDO release used for this curation.)

Gene: SNIP1 hgnc:30587 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (4 references)

PMID:22279524 SUPPORT Human Clinical

"present evidence to strongly support the pathogenicity of variants identified in TUBGCP6, BRAT1, SNIP1, CRADD, and HARS"

Original gene-disease assertion, from autozygosity mapping plus exome sequencing in the Old Order Amish.

PMID:34570759 SUPPORT Human Clinical

"Together these data confirm this SNIP1 gene variant as a cause of an autosomal recessive complex neurodevelopmental disorder"

Definitive confirmation of the gene-disease relationship in a 35-individual cohort.

PMID:34570759 SUPPORT Human Clinical

"The SNIP1 variant was assessed according to ACMG variant classifi- cation criteria as ‘pathogenic"

Formal ACMG classification of the founder allele as pathogenic.

+ 1 more reference

💊

Medical Actions

Anticonvulsant Therapy

Action: Anticonvulsant Therapy NCIT:C64172

Antiseizure medication is the mainstay of neurological management, but the published experience is explicit that no antiepileptic medication was identified that consistently provides effective seizure control, and several individuals have multiple drug resistant epilepsy. The published advice is therefore about the goals of therapy rather than a specific agent: children should be under specialist neurology care for careful optimisation of anticonvulsant medication, to treat apnoea in infancy, maintain seizure control, and prevent status epilepticus and consequent developmental regression. No specific drug, drug class or drug to avoid is named in the source, and none is asserted here.

Target Phenotypes: Seizure HP:0001250 Status epilepticus HP:0002133

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"careful optimisation of anticonvulsant medications to treat apnea in infancy, maintain seizure control, and prevent status epilepticus and consequent"

The published management goal for anticonvulsant therapy in this disorder. The quotation ends mid-sentence at the page break in the cached text; the sentence continues "developmental regression".

PMID:34570759 PARTIAL Human Clinical

The efficacy caveat. Marked PARTIAL because it documents the limits of the intervention rather than supporting its effectiveness, and it is the reason no specific agent is recommended in this entry.

Elective Gastrostomy

Action: Gastrostomy NCIT:C52006

Elective gastrostomy tube placement is recommended to support growth and limit pulmonary aspiration. This is one of two interventions the authors single out as simple measures that can reduce hospitalisations, alleviate suffering and prolong life, which is an unusually strong claim for a supportive measure and reflects the universality of feeding failure and the 46% rate of pulmonary aspiration.

Target Phenotypes: Feeding difficulties HP:0011968 Aspiration HP:0002835

Show evidence (2 references)

PMID:34570759 SUPPORT Human Clinical

"We recommend elective gastrostomy tube placement to support growth and limit pulmo- nary aspiration"

The explicit recommendation for elective rather than reactive gastrostomy.

PMID:34570759 SUPPORT Human Clinical

"These simple interventions can reduce hospitalizations, alleviate suffering, and prolong life"

The claimed benefit of the combined gastrostomy and seizure-optimisation strategy.

Early Multidisciplinary Developmental Therapy

Action: Supportive Care NCIT:C15747

Speech and language therapy, physical therapy and occupational therapy should all be commenced at an early stage to maximise neurocognitive outcome. An assessment of special educational needs should be carried out so an individualised educational plan can be put in place at school.

Target Phenotypes: Global developmental delay HP:0001263 Intellectual disability HP:0001249

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Supportive therapies (occupational, speech, and physical therapy) should be commenced at an early stage to maximise neurocognitive outcome for patients with SNIP1-related disorder"

The published recommendation for early multidisciplinary therapy.

Applied Behaviour Analysis for Autism Spectrum Disorder

Action: Supportive Care NCIT:C15747

Behavioural therapy including Applied Behaviour Analysis is reported to be beneficial in older affected children who have autism spectrum disorder.

Target Phenotypes: Autism HP:0000717

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Behavioural therapy (including Applied Behaviour Analysis) is benefi- cial in older affected children who have autism spectrum disorder"

The published behavioural-management recommendation, restricted to older children with autism spectrum disorder.

Melatonin for Sleep Dysregulation

Action: Pharmacotherapy NCIT:C15986

Agent: melatonin CHEBI:16796

Many children experience sleep dysregulation, and melatonin has been used successfully in some children. Sleep deprivation is separately documented as a seizure trigger in this disorder, so treating sleep dysregulation has a plausible secondary benefit for seizure burden, although that link has not been tested.

Target Phenotypes: Sleep disturbance HP:0002360

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Many children experience sleep dysregulat ion. Melatonin has been used successfu lly in some children"

Table 3 clinical guidance row for sleep. Word-internal spacing is a PDF extraction artifact.

Endocrine Monitoring for Hypoglycaemia and Hypothyroidism

Action: Supportive Care NCIT:C15747

Infants and children should be monitored for hypoglycaemia and hypothyroidism, explicitly because these are easily treatable. This is a high-yield recommendation: hypothyroidism affects 25% and hypoglycaemia 21% of individuals, and hypoglycaemic episodes are also a documented seizure trigger.

Target Phenotypes: Hypothyroidism HP:0000821 Hypoglycemia HP:0001943

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Individuals should also be monitored for hypoglycemia and hypothyroidism as these are easily treatable"

The published surveillance recommendation and its rationale.

Annual Ophthalmology and Audiology Surveillance

Action: Supportive Care NCIT:C15747

Yearly ophthalmology and audiology assessments are recommended, reflecting the 45% rate of nystagmus and/or strabismus, the reported myopia, and the 21% rate of failed newborn hearing screening with conductive loss and chronic otitis media.

Target Phenotypes: Strabismus HP:0000486 Conductive hearing impairment HP:0000405

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Yearly ophthalmology and audiology assessments are recommended"

The published surveillance interval for sensory assessment, one of the few places the source gives an explicit frequency.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from SNIP1-Related Neurodevelopmental Disorder:

Heterozygous 1p34.3p34.2 contiguous gene deletion including SNIP1

Overlapping Features A de novo 2.3 Mb interstitial deletion at 1p34.3p34.2 encompassing 43 genes, including SNIP1, was reported in a 17-year-old female with global developmental delay, mild intellectual disability and multiple congenital anomalies. The authors concluded that SNIP1 haploinsufficiency was the most likely cause. This is the single most important named-entity distinction for this entry, because a naive search for "SNIP1 neurodevelopmental disorder" returns it alongside the recessive disorder.

Distinguishing Features

Dosage - heterozygous whole-gene deletion versus biallelic missense hypomorphism. These are different genetic mechanisms and should not be pooled.
Severity - the deletion case had mild intellectual disability and no epilepsy reported, whereas the biallelic disorder has severe non-verbal developmental delay and universal intractable epilepsy.
Attribution - the deletion removes 43 genes and the authors could neither confirm SNIP1 as the driver nor exclude contributions from the other genes, so it does not establish a heterozygous SNIP1 phenotype.
Inheritance and counselling - de novo heterozygous CNV versus autosomal recessive with 25% sibling recurrence risk. Amish parents of an affected child are obligate heterozygotes and are unaffected, which is itself evidence against a clinically significant heterozygous phenotype in this population.

Show evidence (2 references)

PMID:29726122 SUPPORT Human Clinical

"Haploinsufficiency of the 1p34.3p34.2 region, including the SNIP1 gene and excluding the five genes listed above, is responsible for the neurocognitive delays and other symptoms as identified in our patient"

The deletion report's own conclusion, which is an attribution to a region rather than to SNIP1 alone.

PMID:34570759 SUPPORT Human Clinical

"The authors concluded that haploinsufficienc y of SNIP1 was the most likely cause of the female’s neurodevelopmental phenotype, although they were not able to confirm this nor rule out contributions of the other genes involved"

Independent assessment that the deletion case does not establish a SNIP1-specific heterozygous phenotype. The "haploinsufficienc y" spelling is a PDF extraction artifact.

Craniofacial spliceosomopathies

Overlapping Features Disruption of spliceosome components causes several neurodevelopmental disorders with craniofacial defects, specifically Guion-Almeida type mandibulofacial dysostosis (EFTUD2), Nager syndrome (SF3B4) and cerebrocostomandibular syndrome (SNRPB). These overlap with SNIP1-related disorder in midface hypoplasia, cleft palate, developmental delay, intellectual disability, congenital cardiac defects and scoliosis, and the overlap is mechanistically real rather than coincidental given SNIP1's spliceosomal role.

Distinguishing Features

Causal gene differs (EFTUD2, SF3B4, SNRPB versus SNIP1); the diagnosis is molecular.
Inheritance - the classical craniofacial spliceosomopathies listed are dominant, usually de novo, whereas SNIP1-related disorder is autosomal recessive.
Epilepsy burden - universal intractable epilepsy from infancy is characteristic of the SNIP1 disorder and is not a defining feature of the mandibulofacial dysostoses.
Calvarial phenotype - the irregular "lumpy" skull surface with variable calvarial thickness and a cortical ribbon that follows the skull contour is distinctive to the SNIP1 disorder.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Disrup- tion of spliceosome components have been associated with several neurodevelopmental disor- ders involving craniofacial defects, for example Guion-Almeida type mandibulofacial dysostosis, Nager syndrome, and cerebrocostomandibular syndrome, which also display sev- eral overlapping..."

The clinical report's own placement of this disorder within the craniofacial spliceosomopathy differential.

TGF-beta pathway connective tissue and aortopathy syndromes

Overlapping Features Loeys-Dietz syndrome and related TGF-beta pathway disorders share congenital cardiac defects including bicuspid aortic valve, septal defects, patent ductus arteriosus, mitral regurgitation and aortic root dilatation, together with craniosynostosis, cleft palate, hypertelorism, micrognathia, talipes and scoliosis. The overlap with SNIP1-related disorder is substantial and is predicted by SNIP1's role as a TGF-beta/Smad co-regulator.

Distinguishing Features

Causal gene differs (TGFBR1, TGFBR2, SMAD3, TGFB2, TGFB3 versus SNIP1).
Cognition - Loeys-Dietz syndrome does not feature severe global developmental delay, intellectual disability or intractable epilepsy, which dominate the SNIP1 phenotype.
Aortic risk - progressive aortic aneurysm and dissection drive management in Loeys-Dietz syndrome; aortic root dilatation is reported in the SNIP1 disorder but no aneurysm or dissection risk has been established, and none is asserted here.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"This includes systemic aortopathies, including for example Loeys-Dietz syndrome"

Names Loeys-Dietz syndrome as the TGF-beta pathway disorder with which this condition shares cardiovascular and craniofacial features.

CNTNAP2-related Pitt-Hopkins-like syndrome Not Yet Curated MONDO:0012400

Overlapping Features CNTNAP2 was among the most upregulated transcripts in affected individuals, and biallelic CNTNAP2 disruption causes an autosomal recessive Pitt-Hopkins-like syndrome (cortical dysplasia focal epilepsy syndrome) characterised by neurodevelopmental delay, hypotonia, hyporeflexia, seizures of multiple types, neuronal migration abnormality, autistic features and attention deficits. That is close to a phenocopy of the neurological arm of SNIP1-related disorder, which is presumably why CNTNAP2 dysregulation is a candidate mediator rather than a coincidence.

Distinguishing Features

Causal gene differs (CNTNAP2 versus SNIP1).
CNTNAP2 disease lacks the characteristic calvarial dysplasia, craniofacial gestalt and 60% congenital heart disease burden of the SNIP1 disorder.
In the SNIP1 disorder CNTNAP2 is dysregulated downstream, not mutated; this is a mechanistic relationship, not an alternative diagnosis in a molecularly confirmed case.

Show evidence (1 reference)

PMID:34570759 SUPPORT Human Clinical

"Disruption of CNTNAP2 is associated with autosomal recessive Pitt-Hopkins-like syndrome (also known as cortical dysplasia focal epilepsy syndrome; MIM 610042) characterized by neurodevelopmental delay, hypotonia, hyporeflexia, seizures of multiple types, neuronal migration abnormalities,..."

Documents the phenotypic near-identity of the neurological arm and identifies CNTNAP2 as a downstream dysregulated gene in the SNIP1 disorder.

{ }

Source YAML

click to show

name: SNIP1-Related Neurodevelopmental Disorder
creation_date: "2026-08-01T00:00:00Z"
category: Mendelian
synonyms:
- psychomotor retardation, epilepsy, and craniofacial dysmorphism
- PMRED
- neurodevelopmental disorder with hypotonia, craniofacial abnormalities, and seizures
- symptomatic epilepsy and skull dysplasia
- SNIP1-related disorder
description: >
  SNIP1-related neurodevelopmental disorder is a severe autosomal recessive
  multisystem condition caused by biallelic variants in SNIP1 (Smad nuclear
  interacting protein 1, 1p34.3). It was first delineated in the Old Order Amish,
  where a single founder missense substitution,
  NM_024700.4:c.1097A>G p.(Glu366Gly), accounts for every molecularly confirmed
  case reported to date. The cardinal features are neonatal hypotonia with
  hypo/areflexia, severe global developmental delay and intellectual disability,
  universal infantile-onset drug-resistant epilepsy, and a recognisable
  craniofacial and calvarial gestalt that includes an irregular "lumpy" skull
  surface, midface hypoplasia, a wide mouth with a thin cupid's bow upper lip,
  high arched palate, and microretrognathia with or without Pierre Robin
  sequence. Congenital heart disease, upper airway malacia, feeding failure
  requiring gastrostomy, and endocrine and sensory involvement complete a
  multisystem picture with substantial early mortality.

  SNIP1 is a nuclear protein with an N-terminal nuclear localisation signal and a
  C-terminal forkhead-associated (FHA) domain. It has three mechanistically
  distinct jobs that all plausibly contribute to disease: it is a
  phosphopeptide-reading adaptor that recruits the retention-and-splicing (RES)
  complex to the activated spliceosome; it is a nuclear co-regulator that sets
  thresholds for CBP/p300-dependent transcription downstream of TGF-beta/Smad,
  NF-kappaB and c-MYC; and it directs Polycomb PRC2 genomic occupancy and
  H3K27me3 turnover to keep neural progenitors alive. The p.(Glu366Gly)
  substitution sits in the conserved C-terminal region adjacent to the FHA
  domain; it destabilises the protein and impairs FHA-domain recognition of
  phosphorylated SF3B1, so SNIP1 function is degraded rather than abolished.
  Complete loss of SNIP1 is embryonic lethal in mouse, which is why the viable
  human disorder is attributed to a hypomorphic rather than a null allele.
disease_term:
  preferred_term: psychomotor retardation, epilepsy, and craniofacial dysmorphism
  term:
    id: MONDO:0013787
    label: psychomotor retardation, epilepsy, and craniofacial dysmorphism
parents:
- Neurodevelopmental disorder
- Autosomal recessive disease
- Developmental and epileptic encephalopathy
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    notes: >-
      A mechanism-defined multisystem Mendelian disorder of a nuclear
      phosphopeptide-binding adaptor. The dominant burden is neurodevelopmental
      (epilepsy, developmental delay, intellectual disability), but the entry
      also spans craniofacial/calvarial, cardiac, airway, gastrointestinal,
      endocrine and sensory manifestations, so the cross-organ genetics chapter
      fits better than NEUROLOGIC alone.
prevalence:
- population: Old Order Amish (Pennsylvania, Ohio, Indiana, Wisconsin settlements)
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Founder-population case count, NOT a general population rate. Fifty-one Old
    Order Amish individuals across 27 sibships had been identified at the time of
    the 2021 report, of whom 35 were comprehensively clinically evaluated and 49
    were molecularly confirmed homozygous. No affected individual outside the
    Amish has been reported with biallelic SNIP1 variants, so no worldwide
    prevalence estimate exists and none is asserted. An Orphanet/ORPHA-derived
    epidemiology record could not be generated for this entry because the
    structured-source data pins are stale and un-refreshable (tracked in #7622).
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A total of fifty-one Old Order Amish individuals were identified with SNIP1-related disorder, among 27 sibships"
    explanation: >-
      The cumulative ascertained case count in the founder population. Because
      ascertainment was through two Plain-community clinics rather than a
      population screen, this is a case tally and not a denominator-based rate.
- population: Old Order Amish carrier screening (in-house control database, >5000 individuals)
  measure_type: CARRIER_FREQUENCY
  prevalence_class: ABOVE_1_IN_1000
  notes: >-
    Carrier (heterozygote) allele frequency of the founder allele in the Amish,
    reported as a range across settlements: 0.5% in the Pennsylvania Amish and
    1.4% in the Ohio/Indiana/Wisconsin Amish. These are ALLELE frequencies in a
    founder population and must not be read as disease prevalence or as
    generalisable carrier rates. The prevalence_class band records only that the
    allele is common in this specific population. For contrast, the same allele
    has a gnomAD v3.1 frequency of 0.001% with 11 heterozygotes (10 of them
    Amish) and no homozygotes.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "p.(Glu366Gly) variant is present at an allele frequency of between 0.5% (Pennsylvania Amish) and 1.4% (Ohio/Indiana/Wiscon sin Amish) in this founder population, with no unaffected individuals being homozygous for this variant"
    explanation: >-
      Quantifies the founder allele frequency by settlement and confirms full
      penetrance in the sense that no unaffected homozygote was found among more
      than 5000 Amish controls.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Symptomatic epilepsy and skull dysplasia 3 SNIP1 c.1097A.G p.Glu366Gly 1.48% (6/406"
    explanation: >-
      The original discovery report's Table 4 row, headed "Population-specific
      Allele Frequency": 6 variant alleles among 406 Old Order Amish control
      chromosomes, i.e. an allele frequency of 1.48% corresponding to roughly a
      3% heterozygote frequency, independently corroborating that the allele is
      common in this founder population. The "A.G" rendering is a PDF extraction
      artifact for "A>G".
inheritance:
- name: Autosomal recessive biallelic SNIP1 hypomorphism
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  penetrance: COMPLETE
  expressivity: VARIABLE
  description: >-
    All reported affected individuals are homozygous for the same founder allele
    inherited from heterozygous parents; heterozygotes are unaffected. Penetrance
    is recorded as COMPLETE because segregation in 35 evaluated individuals
    showed all parents heterozygous, all unaffected siblings heterozygous or
    wild type, and no unaffected homozygote among more than 5000 Amish controls.
    Expressivity is nonetheless VARIABLE: substantial phenotypic variation was
    documented between affected individuals including within sibships, so the
    same genotype does not predict severity.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "confirmed homozygosity of the SNIP1 variant in 35 individuals, with all parents being heterozygous for the variant and all unaffected siblings being heterozygous for the variant or wild type"
    explanation: >-
      Segregation consistent with autosomal recessive inheritance across a large
      multiplex kindred.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Substantial phenotypic variation was observed between affected individ- uals, including within sibships"
    explanation: >-
      Direct statement of variable expressivity on a homogeneous genetic
      background, which is the strongest available argument that modifiers
      rather than allelic heterogeneity drive severity in this disorder.
pathophysiology:
- name: Biallelic SNIP1 p.Glu366Gly Founder Substitution
  biological_scale: MOLECULAR
  description: >-
    Homozygosity for NM_024700.4:c.1097A>G, p.(Glu366Gly) in exon 4 of SNIP1
    (1p34.3) is the single molecular lesion underlying every molecularly
    confirmed case. Glu366 lies in the conserved C-terminal 30 amino acids,
    immediately adjacent to the forkhead-associated (FHA) domain, within a
    low-complexity or intrinsically disordered region that is strongly conserved
    across species orthologues. The variant is a hypomorph rather than a null:
    Snip1 knockout mice are embryonic lethal, so a complete loss-of-function
    allele would not be compatible with the viable human phenotype.
  genes:
  - preferred_term: SNIP1
    term:
      id: hgnc:30587
      label: SNIP1
  cellular_components:
  - preferred_term: nucleus
    term:
      id: GO:0005634
      label: nucleus
  downstream:
  - target: Reduced SNIP1 Protein Abundance and Altered Nuclear Distribution
    description: >-
      The substituted protein is transcribed normally but is unstable and
      redistributes within the nucleus from a punctate to an aggregated pattern.
  - target: Impaired SNIP1 FHA-Domain Phosphopeptide Recognition
    description: >-
      The change sits next to the FHA domain and degrades its ability to read
      phosphorylated partner proteins.
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SNIP1 Glu366 is highly conserved and the p.Glu366Gly mutation is in the C-terminus where SNIP1 interacts with c-Myc"
    explanation: >-
      Original identification of the causal substitution and its position in the
      C-terminal protein-interaction region.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Multiple species alignment confirms this amino acid is highly conserved across species ortho- logs (Fig 1G) and is located close to the FHA domain at the SNIP1 C-terminus"
    explanation: >-
      Places the substitution structurally adjacent to the FHA domain and
      confirms deep evolutionary conservation of the residue.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "SNIP1 null mouse models display embryonic lethality indicating that this Amish variant may be unlikely to result in complete loss of func- tion"
    explanation: >-
      The argument for hypomorphism rather than a null allele. Classified
      MODEL_ORGANISM because the underlying observation is a mouse knockout
      phenotype (sourced by the authors to the Mouse Genome Database) rather than
      a human finding.
- name: Reduced SNIP1 Protein Abundance and Altered Nuclear Distribution
  biological_scale: MOLECULAR
  description: >-
    Transcript levels of the mutant allele are comparable to wild type, so the
    lesion acts post-transcriptionally. Overexpressed mutant protein is markedly
    less abundant than wild type on Western blot and adopts an aggregated rather
    than a punctate nuclear distribution, indicating impaired protein stability
    and impaired assembly into nuclear transcriptional and splicing complexes.
    This dosage reduction is the shared upstream cause of both the splicing and
    the transcriptional arms of the disease.
  genes:
  - preferred_term: SNIP1
    term:
      id: hgnc:30587
      label: SNIP1
  cellular_components:
  - preferred_term: nuclear speck
    term:
      id: GO:0016607
      label: nuclear speck
    modifier: ABNORMAL
  downstream:
  - target: Defective RES Complex Recruitment to the Activated Spliceosome
    description: >-
      Less SNIP1 protein is available to act as the phosphorylation-dependent
      bridge that loads the RES complex onto the activating spliceosome.
  - target: Disrupted SNIP1 Co-Regulation of CBP/p300-Dependent Transcription
    description: >-
      Reduced SNIP1 abundance releases the threshold SNIP1 normally sets on
      CBP/p300-dependent transcription and removes its support for c-MYC.
  - target: Aberrant PRC2 Genomic Occupancy and H3K27me3 Turnover
    description: >-
      Less SNIP1 is available to direct Polycomb PRC2 to its target loci and to
      instruct H3K27me3 turnover there.
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "However, Snip1 p.Glu353Gly (corresponding to human p.Glu366Gly) had a more aggregated appearance (Figure 3, E) and Western blotting proved it unstable (Figure 3, F); its band density was 84.9 69.6% SD lower than wild-type (n = 4 independent transfections each"
    explanation: >-
      Direct experimental demonstration that the orthologous mouse substitution
      destabilises the protein and mislocalises it within the nucleus. The
      "84.9 69.6% SD" rendering is a PDF extraction artifact for
      "84.9 +/- 9.6% SD".
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Reverse transcriptase-PCR suggests that the Snip1 c.1058A.G (corresponding to human SNIP1 c.1097A.G) transcript is expressed at levels comparable to wild-type"
    explanation: >-
      Excludes a transcript-level mechanism (no nonsense-mediated decay, no
      splicing disruption of the SNIP1 transcript itself), localising the defect
      to protein stability.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Wild-type protein localized to the nucleus with a punctate appearance, consistent with its involvement in transcrip- tional complexes"
    explanation: >-
      Establishes the wild-type nuclear pattern against which the mutant
      aggregated pattern is scored.
- name: Impaired SNIP1 FHA-Domain Phosphopeptide Recognition
  biological_scale: MOLECULAR
  description: >-
    The forkhead-associated (FHA) domain is a phosphothreonine/phosphoserine
    reader module. In the spliceosome cycle, CDK11 phosphorylates the
    threonine-proline repeats of SF3B1 during spliceosome activation, and the
    SNIP1 FHA domain recognises phosphorylated SF3B1. Disease-associated FHA
    domain mutations, explicitly including the neurodevelopmental
    disorder-associated E366G variant, impair that phosphopeptide binding. This
    is the most direct available molecular explanation of what the Amish allele
    actually breaks.
  genes:
  - preferred_term: SNIP1
    term:
      id: hgnc:30587
      label: SNIP1
  molecular_functions:
  - preferred_term: phosphoserine residue binding
    term:
      id: GO:0050815
      label: phosphoserine residue binding
    modifier: DECREASED
  downstream:
  - target: Defective RES Complex Recruitment to the Activated Spliceosome
    description: >-
      Loss of phospho-SF3B1 recognition removes the docking step that loads RES
      onto the activating spliceosome.
  evidence:
  - reference: PMID:41904131
    reference_title: "Phosphorylation of SF3B1 by CDK11 orchestrates spliceosome activation via SNIP1-dependent RES complex recruitment."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Mutations in SNIP1 FHA domain, including the neurodevelopmental disorder-associated E366G variant, impair P-SF3B1 binding, pre-mRNA splicing, and cell viability"
    explanation: >-
      Names the disease variant explicitly and demonstrates the specific
      biochemical deficit: loss of phosphorylated-SF3B1 binding, with downstream
      splicing and viability consequences.
  - reference: PMID:41904131
    reference_title: "Phosphorylation of SF3B1 by CDK11 orchestrates spliceosome activation via SNIP1-dependent RES complex recruitment."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We further demonstrate that P-SF3B1 is recognized by forkhead-associated (FHA) domain of SNIP1, which promotes recruitment of retention and splicing (RES) complex during spliceosome activation"
    explanation: >-
      Establishes the normal molecular function that the E366G substitution
      degrades: FHA-mediated reading of phospho-SF3B1 to recruit RES.
- name: Defective RES Complex Recruitment to the Activated Spliceosome
  biological_scale: MOLECULAR
  description: >-
    SNIP1 is a component of the human activated (B-act) spliceosome and forms the
    retention-and-splicing (RES) complex together with BUD13 and RBMX2. RES is
    required for efficient intron definition and splicing of a defined subset of
    short, GC-rich introns. Acute SNIP1 depletion disrupts RES incorporation and
    causes widespread splicing defects, and loss of RES components in vertebrates
    produces a global intron-splicing defect with a marked neural phenotype.
  genes:
  - preferred_term: SNIP1
    term:
      id: hgnc:30587
      label: SNIP1
  protein_complexes:
  - preferred_term: RES complex
    term:
      id: GO:0070274
      label: RES complex
    modifier: DECREASED
  cellular_components:
  - preferred_term: spliceosomal complex
    term:
      id: GO:0005681
      label: spliceosomal complex
    modifier: ABNORMAL
  downstream:
  - target: Widespread Pre-mRNA Splicing Dysregulation
    description: >-
      Failure to load RES onto the activating spliceosome degrades splicing
      fidelity and efficiency transcriptome-wide.
  evidence:
  - reference: PMID:41904131
    reference_title: "Phosphorylation of SF3B1 by CDK11 orchestrates spliceosome activation via SNIP1-dependent RES complex recruitment."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Acute SNIP1 depletion disrupts RES incorporation, causes widespread splicing defects, and promotes hyperphosphorylation of SF3B1 by CDK11"
    explanation: >-
      Loss-of-SNIP1 experiment showing that RES incorporation is SNIP1-dependent
      and that its failure produces transcriptome-wide splicing defects.
  - reference: PMID:29360106
    reference_title: "Structure of the human activated spliceosome in three conformational states."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Structure of the human activated spliceosome in three conformational states"
    explanation: >-
      Structural confirmation that SNIP1 is a bona fide constituent of the human
      activated spliceosome, which is the basis for treating the splicing arm as
      a physiological SNIP1 role rather than an incidental interaction. Only the
      title-level assertion is quoted because the fetched record for this
      structural paper is title/metadata level; the SNIP1-in-B-act claim is
      independently attributed in PMID:34570759.
  - reference: PMID:29969449
    reference_title: "RES complex is associated with intron definition and required for zebrafish early embryogenesis."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "Transcriptomic analysis of bud13, snip1 (pml1) and rbmx2 (snu17) mutants revealed a global defect in intron splicing, with strong mis-splicing of a subset of introns"
    explanation: >-
      Vertebrate loss-of-function evidence that snip1 is required for normal
      intron splicing as part of RES. Marked PARTIAL because zebrafish snip1
      mutants are functional nulls with early embryonic lethality, whereas the
      human allele is hypomorphic, so severity does not transfer.
- name: Widespread Pre-mRNA Splicing Dysregulation
  biological_scale: MOLECULAR
  description: >-
    Reduced RES loading degrades splicing of RES-dependent introns, which are
    characteristically short, GC-rich and flanked by GC-depleted exons, i.e.
    introns that depend on intron definition rather than exon definition. The
    net effect is a transcriptome-wide shift in splicing efficiency rather than a
    single mis-spliced gene product, which is consistent with the multisystem
    phenotype.
  biological_processes:
  - preferred_term: "mRNA splicing, via spliceosome"
    term:
      id: GO:0000398
      label: "mRNA splicing, via spliceosome"
    modifier: DECREASED
  downstream:
  - target: Detained-Intron Splicing Brake Dysregulation in Neurons
    description: >-
      SNIP1 additionally sets the pause point for post-transcriptional splicing
      of detained introns, a neuron-relevant subset of the same defect.
  - target: Altered Neurodevelopmental Gene Expression Programme
    description: >-
      Degraded splicing efficiency changes the abundance of mature transcripts
      for developmentally critical genes.
  evidence:
  - reference: PMID:29969449
    reference_title: "RES complex is associated with intron definition and required for zebrafish early embryogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We found these RES-dependent introns were short, rich in GC and flanked by GC depleted exons, all of which are features associated with intron definition"
    explanation: >-
      Defines the sequence features of the intron subset whose splicing depends
      on RES, and therefore on SNIP1.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "as part of the retention and splicing (RES) complex, which plays a crucial role in splicing and retention of pre-mRNA"
    explanation: >-
      The clinical report's own statement of the splicing arm, connecting the
      disorder to spliceosomopathy biology. The quotation starts mid-sentence to
      avoid a bracketed numeric citation marker in the extracted text; the
      preceding clause reads "SNIP1 also forms a component of the human
      activated spliceosome".
- name: Detained-Intron Splicing Brake Dysregulation in Neurons
  biological_scale: CELLULAR
  description: >-
    Beyond bulk splicing, SNIP1 together with RNPS1 forms a molecular brake that
    pauses the spliceosome at the B-act state on detained introns, holding
    intron-detaining transcripts in the nucleus as a rapidly deployable mRNA
    pool. Conditional Snip1 deletion in mouse cerebellum reduces detained-intron
    splicing efficiency and causes neurodegeneration, identifying neurons as a
    tissue in which the timing of detained-intron release is SNIP1-dependent and
    functionally critical.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: "regulation of alternative mRNA splicing, via spliceosome"
    term:
      id: GO:0000381
      label: "regulation of alternative mRNA splicing, via spliceosome"
    modifier: DYSREGULATED
  downstream:
  - target: Altered Neurodevelopmental Gene Expression Programme
    description: >-
      Mis-timed release of detained introns changes the neuronal transcript
      repertoire available at critical developmental and homeostatic windows.
  evidence:
  - reference: PMID:37027487
    reference_title: "A molecular brake that modulates spliceosome pausing at detained introns contributes to neurodegeneration."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "Snip1 conditional knockout in the cerebellum decreases DI splicing efficiency and causes neurodegeneration"
    explanation: >-
      Establishes a neuron-specific, SNIP1-dependent splicing function whose loss
      is sufficient to damage the CNS. Marked PARTIAL because this is a
      conditional null in mouse cerebellum, not the human hypomorphic allele, and
      because the human disorder is a developmental encephalopathy rather than a
      documented progressive neurodegeneration.
  - reference: PMID:37027487
    reference_title: "A molecular brake that modulates spliceosome pausing at detained introns contributes to neurodegeneration."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we suggest that post-transcriptional DI splicing is paused at the Bact state, an active spliceosome but not catalytically primed, which depends on Smad Nuclear Interacting Protein 1 (SNIP1) and RNPS1 (a serine-rich RNA binding protein) interaction"
    explanation: >-
      Defines the specific molecular role, spliceosome pausing at the B-act state
      on detained introns, that requires SNIP1.
- name: Disrupted SNIP1 Co-Regulation of CBP/p300-Dependent Transcription
  biological_scale: MOLECULAR
  description: >-
    SNIP1 sets a threshold for CBP/p300-dependent transcriptional activation. Its
    N-terminus binds both Smad4 and the coactivator CBP/p300, and SNIP1
    competitively inhibits both Smad4/p300 complex formation and NF-kappaB (RelA)
    access to the C/H1 domain of CBP/p300. Its C-terminus binds c-MYC, stabilising
    it against proteasomal degradation and bridging a c-MYC/p300 complex. Reduced
    SNIP1 abundance therefore simultaneously releases restraint on TGF-beta/Smad
    and NF-kappaB output and withdraws support from c-MYC, which is the
    transcriptional arm of this disease.
  genes:
  - preferred_term: SNIP1
    term:
      id: hgnc:30587
      label: SNIP1
  molecular_functions:
  - preferred_term: transcription coactivator activity
    term:
      id: GO:0003713
      label: transcription coactivator activity
    modifier: DYSREGULATED
  biological_processes:
  - preferred_term: regulation of transcription by RNA polymerase II
    term:
      id: GO:0006357
      label: regulation of transcription by RNA polymerase II
    modifier: DYSREGULATED
  downstream:
  - target: Derepressed TGF-beta/Smad Transcriptional Output
    description: >-
      Loss of SNIP1 restraint on Smad4/p300 complex formation raises TGF-beta
      pathway transcriptional output.
  - target: Derepressed NF-kappaB Transcriptional Output
    description: >-
      Loss of SNIP1 competition for the CBP/p300 C/H1 domain raises NF-kappaB
      dependent transcription.
  - target: Altered Neurodevelopmental Gene Expression Programme
    description: >-
      Withdrawal of SNIP1 support for c-MYC and the combined pathway shifts
      remodel the developmental gene expression programme.
  - target: Aberrant Distal Limb and Digit Development
    description: >-
      Disruption of c-MYC or CBP/p300 signalling in mouse produces abnormal
      development of the distal limbs as well as of brain and skull.
  evidence:
  - reference: PMID:10887155
    reference_title: "A novel smad nuclear interacting protein, SNIP1, suppresses p300-dependent TGF-beta signal transduction."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Overexpression of full-length SNIP1 or its amino terminus is sufficient to inhibit multiple gene responses to TGF-beta and CBP/p300, as well as the formation of a Smad4/p300 complex"
    explanation: >-
      Original demonstration of SNIP1 as a nuclear inhibitor of CBP/p300 acting
      on TGF-beta transcriptional responses.
  - reference: PMID:10887155
    reference_title: "A novel smad nuclear interacting protein, SNIP1, suppresses p300-dependent TGF-beta signal transduction."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "SNIP1 is a nuclear inhibitor of CBP/p300 and its level of expression in specific cell types has important physiological consequences by setting a threshold for TGF-beta-induced transcriptional activation involving CBP/p300"
    explanation: >-
      States the dosage-threshold model explicitly, which is precisely why a
      hypomorphic reduction in SNIP1 abundance is expected to be pathogenic.
  - reference: PMID:11567019
    reference_title: "SNIP1 inhibits NF-kappa B signaling by competing for its binding to the C/H1 domain of CBP/p300 transcriptional co-activators."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "SNIP1 inhibits NF-kappa B signaling by competing for its binding to the C/H1 domain of CBP/p300 transcriptional co-activators"
    explanation: >-
      Establishes the competitive mechanism by which SNIP1 restrains NF-kappaB at
      the shared CBP/p300 coactivator.
  - reference: PMID:17157259
    reference_title: "SNIP1 is a candidate modifier of the transcriptional activity of c-Myc on E box-dependent target genes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "SNIP1 enhances the transcriptional activity of c-Myc both by stabilizing it against proteosomal degradation and by bridging the c-Myc/p300 complex"
    explanation: >-
      Establishes the positive, C-terminus-dependent arm of SNIP1 transcriptional
      co-regulation. This is the interaction surface in which p.Glu366Gly lies.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Decreased abundance of SNIP1 likely results in decreased c- Myc activity and increased TGF- b and NF- kB signaling"
    explanation: >-
      The discovery paper's synthesis of the three-pathway consequence of reduced
      SNIP1 dosage, tying the in vitro co-regulation biology to this specific
      human allele.
  - reference: PMID:38304835
    reference_title: "The clinical utilization of SNIP1 and its pathophysiological mechanisms in disease."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "the N-terminal domain of SNIP1 facilitates its interaction with Smad4, a signaling protein associated with the TGF-β family, and RelA/p65, a transcription factor connected to NF-κB. This interaction further enhances the transcriptional activation of c-Myc-dependent genes"
    explanation: >-
      Review-level synthesis of the three partner interactions that define this
      node. Cited as background molecular biology of the SNIP1 protein; the
      review concerns cancer and inflammation, not this neurodevelopmental
      disorder, hence evidence_source OTHER.
- name: Derepressed TGF-beta/Smad Transcriptional Output
  biological_scale: MOLECULAR
  description: >-
    With less SNIP1 available to restrain Smad4/p300 complex formation, TGF-beta
    pathway transcriptional output rises. Blood transcriptome analysis of six
    affected individuals found TGF-beta receptor signalling in
    epithelial-to-mesenchymal transition to be the single most overrepresented
    dysregulated Reactome pathway, and identified two downregulated TGF-beta
    pathway genes (BMPR1A and ACVR1C). Because disorders of TGF-beta/BMP
    signalling characteristically produce craniofacial, skeletal and
    cardiovascular malformation, this node is the most plausible mechanistic
    route to the non-neurological half of the syndrome.
  biological_processes:
  - preferred_term: transforming growth factor beta receptor signaling pathway
    term:
      id: GO:0007179
      label: transforming growth factor beta receptor signaling pathway
    modifier: DYSREGULATED
  downstream:
  - target: Aberrant Craniofacial and Calvarial Morphogenesis
    description: >-
      Perturbed TGF-beta/BMP output in cranial neural crest derivatives and
      calvarial osteogenic fronts disturbs facial and skull development.
  - target: Aberrant Cardiac and Outflow Tract Morphogenesis
    description: >-
      TGF-beta/BMP signalling is required for septation, valvulogenesis and
      aortic arch remodelling.
  - target: Aberrant Laryngeal and Pharyngeal Cartilage Development
    description: >-
      TGF-beta/BMP pathway disorders characteristically involve connective
      tissue and cartilage, the tissues whose failure produces airway malacia.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the most overrepresented pathway was the TGF-β receptor signalling in epithelial to mesenchyme pathway with differential expression of three genes (upregulation of PARD3 and downregulation of F11R and RPS27A"
    explanation: >-
      Patient-derived transcriptomic evidence that the TGF-beta arm is the
      dominant dysregulated pathway in this disorder.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "defining two downregulated genes (BMPR1A and ACVR1C) involved in the TGF-β pathway"
    explanation: >-
      Named TGF-beta pathway genes dysregulated in patient blood. Marked PARTIAL
      because blood is not the affected tissue and the authors explicitly flag
      that limitation.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genetic variants leading to disruption of the TGF-β/BMP molecular sig- nalling pathway have been implicated in the pathogenesis of a number of inherited disorders, in particular connective tissue disorders associated with craniofacial (e.g. cleft palate and cra- niosynostosis), cardiovascular (e.g. aortic aneurysm and syndromic aortopathies), and muscu- loskeletal (e.g. disorders of endochondral ossification, bone growth, remodelling and limb development) outcomes"
    explanation: >-
      Establishes the expected organ-system consequences of TGF-beta/BMP pathway
      disruption, which map onto the craniofacial, cardiovascular and skeletal
      features of this disorder.
- name: Derepressed NF-kappaB Transcriptional Output
  biological_scale: MOLECULAR
  description: >-
    SNIP1 normally competes with the RelA subunit of NF-kappaB for the C/H1 domain
    of CBP/p300. Reduced SNIP1 therefore raises NF-kappaB-dependent transcription.
    Two consequences are relevant here. In brain, inappropriate increases in
    NF-kappaB signalling have been shown to initiate epileptogenesis in mouse. In
    heart, SNIP1 deficiency worsens pressure-overload hypertrophy through
    NF-kappaB, and blocking NF-kappaB rescues it, which is notable because left
    ventricular non-compaction occurs in this disorder.
  biological_processes:
  - preferred_term: canonical NF-kappaB signal transduction
    term:
      id: GO:0007249
      label: canonical NF-kappaB signal transduction
    modifier: INCREASED
  downstream:
  - target: Cortical Network Hyperexcitability
    description: >-
      Increased NF-kappaB and TGF-beta/Smad2 signalling in brain are each
      sufficient to initiate epileptogenesis in mouse.
  - target: Impaired Myocardial Stress Adaptation
    description: >-
      Loss of SNIP1 restraint on NF-kappaB in cardiomyocytes worsens
      hypertrophic remodelling and contractile dysfunction.
  evidence:
  - reference: PMID:11567019
    reference_title: "SNIP1 inhibits NF-kappa B signaling by competing for its binding to the C/H1 domain of CBP/p300 transcriptional co-activators."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "SNIP1 inhibits NF-kappa B signaling by competing for its binding to the C/H1 domain of CBP/p300 transcriptional co-activators"
    explanation: >-
      Mechanistic basis for NF-kappaB derepression when SNIP1 is reduced.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "Inappropriate increases in TGF- b/Smad2 signaling and in NF- kB signaling in the mouse brain have been shown to independently initiate epileptogenesis"
    explanation: >-
      Links the predicted signalling derangement to the cardinal phenotype.
      Marked PARTIAL because this is a mouse-derived inference cited by the
      authors, not a measurement made in SNIP1 patients.
  - reference: PMID:27912208
    reference_title: "Smad Nuclear Interacting Protein 1 Acts as a Protective Regulator of Pressure Overload-Induced Pathological Cardiac Hypertrophy."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "SNIP1 deficiency significantly exacerbated aortic banding-induced cardiac hypertrophy, fibrosis, and contractile dysfunction, whereas cardiac-specific overexpression of SNIP1 markedly recovered pressure overload-induced cardiac hypertrophy and fibrosis"
    explanation: >-
      Shows a SNIP1-dose-dependent cardiac phenotype mediated by NF-kappaB.
      Marked PARTIAL because it is a pressure-overload mouse model of acquired
      hypertrophy, not a model of the germline human disorder.
- name: Aberrant PRC2 Genomic Occupancy and H3K27me3 Turnover
  biological_scale: MOLECULAR
  description: >-
    A third, epigenetic arm of SNIP1 function, established in mouse
    neural-progenitor-specific knockout. SNIP1 facilitates the genomic occupancy
    of the Polycomb repressive complex PRC2 and instructs H3K27me3 turnover at
    target genes; the SNIP1 target genes concerned are ones that promote cell
    survival and neurogenesis, and SNIP1 activity at them is itself influenced by
    TGF-beta and NF-kappaB signalling, which ties this arm back to the
    transcriptional co-regulation arm. Loss of this function mislocalises
    repressive H3K27 marks and silences a survival programme. The decisive
    evidence is a rescue: depleting PRC2 is sufficient to reduce apoptosis and
    brain dysplasia in the SNIP1-depleted brain.
  protein_complexes:
  - preferred_term: PcG protein complex
    term:
      id: GO:0031519
      label: PcG protein complex
    modifier: DYSREGULATED
  molecular_functions:
  - preferred_term: histone H3K27 trimethyltransferase activity
    term:
      id: GO:0140951
      label: histone H3K27 trimethyltransferase activity
    modifier: DYSREGULATED
  downstream:
  - target: Neural Progenitor Cell Apoptosis and Reduced Neurogenesis
    description: >-
      Mislocalised PRC2/H3K27me3 silences the SNIP1-dependent survival and
      neurogenesis programme, triggering caspase-9-dependent apoptosis.
  - target: Altered Neurodevelopmental Gene Expression Programme
    description: >-
      Aberrant H3K27me3 deposition is a second route, alongside splicing and
      CBP/p300 co-regulation, to a distorted developmental transcriptome.
  evidence:
  - reference: PMID:37553330
    reference_title: "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Further, SNIP1 facilitates the genomic occupancy of Polycomb complex PRC2 and instructs H3K27me3 turnover at target genes"
    explanation: >-
      Establishes the PRC2-directing function of SNIP1 in the developing brain.
  - reference: PMID:37553330
    reference_title: "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Depletion of PRC2 is sufficient to reduce apoptosis and brain dysplasia and to partially restore genetic programs in the SNIP1-depleted brain in vivo"
    explanation: >-
      Epistasis rescue placing PRC2 downstream of SNIP1 and causally between
      SNIP1 loss and the apoptotic brain phenotype. This is the strongest
      evidence that the PRC2 arm is mechanistically load-bearing rather than
      correlative.
  - reference: PMID:37553330
    reference_title: "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Mechanistically, SNIP1 regulates target genes that promote cell survival and neurogenesis, and its activities are influenced by TGFβ and NFκB signaling pathways"
    explanation: >-
      Connects this epigenetic arm to the TGF-beta and NF-kappaB arms curated
      separately, indicating the arms are coupled rather than independent.
  notes: >-
    Entirely mouse-derived and obtained in a conditional NULL background
    (Nestin-Cre Snip1 knockout), not with the human hypomorphic p.(Glu366Gly)
    allele. See the snip1_null_vs_hypomorph_model_mismatch discussion.
- name: Neural Progenitor Cell Apoptosis and Reduced Neurogenesis
  biological_scale: CELLULAR
  description: >-
    The pivotal cellular hub of the neurological arm. SNIP1 promotes neural
    progenitor cell survival and neurogenesis, and the SNIP1-depleted brain
    exhibits dysplasia with robust induction of caspase-9-dependent apoptosis,
    i.e. death by the intrinsic mitochondrial pathway rather than by death
    receptors. The same convergence is reproduced in a second vertebrate by a
    completely different route: zebrafish RES-complex mutants, including snip1,
    show increased cell death in the brain and a decrease in differentiated
    neurons. Two independent organisms and two independent mechanistic entry
    points (PRC2 and splicing) therefore arrive at the same cellular lesion.
  cell_types:
  - preferred_term: neural progenitor cell
    term:
      id: CL:0011020
      label: neural progenitor cell
  - preferred_term: radial glial cell
    term:
      id: CL:0000681
      label: radial glial cell
  biological_processes:
  - preferred_term: intrinsic apoptotic signaling pathway
    term:
      id: GO:0097193
      label: intrinsic apoptotic signaling pathway
    modifier: INCREASED
  - preferred_term: cerebral cortex neuron differentiation
    term:
      id: GO:0021895
      label: cerebral cortex neuron differentiation
    modifier: DECREASED
  downstream:
  - target: Structural Brain Malformation and White Matter Abnormality
    description: >-
      Depletion of the progenitor pool and loss of newly generated neurons
      produce brain dysplasia, cortical thinning and reduced white matter.
  evidence:
  - reference: PMID:37553330
    reference_title: "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "we report that Smad nuclear interacting protein 1 (SNIP1) promotes neural progenitor cell survival and neurogenesis and is, therefore, integral to brain development"
    explanation: >-
      Defines the normal SNIP1 function whose loss produces this node.
  - reference: PMID:37553330
    reference_title: "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The SNIP1-depleted brain exhibits dysplasia with robust induction of caspase 9-dependent apoptosis"
    explanation: >-
      Identifies both the tissue outcome (dysplasia) and the specific apoptotic
      route (caspase-9, i.e. intrinsic/mitochondrial).
  - reference: PMID:29969449
    reference_title: "RES complex is associated with intron definition and required for zebrafish early embryogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The mutants showed a marked neural phenotype with increased cell death in the brain and a decrease in differentiated neurons"
    explanation: >-
      Independent cross-species corroboration in zebrafish snip1/RES mutants,
      reached through the splicing arm rather than the PRC2 arm.
  notes: >-
    Both supporting models are loss-of-function nulls (mouse conditional null,
    zebrafish mutant), not the human hypomorphic allele, and neither has been
    demonstrated in human tissue. The node is nonetheless curated as central
    because two independent organisms and two independent molecular entry points
    converge on it, and because it is the point at which PRC2 depletion rescues.
- name: Altered Neurodevelopmental Gene Expression Programme
  biological_scale: MOLECULAR
  description: >-
    The convergent output of the splicing and transcriptional arms is a
    reproducible shift in the expression of genes with established
    neurodevelopmental and neuropathological roles. Whole-transcriptome
    sequencing of six affected individuals identified 75 significantly
    upregulated and 109 significantly downregulated genes. Of the most strongly
    altered transcripts with a known clinical association, 24 had a previously
    established association with neurological disease, and five of those (ROBO1,
    SOX5, CNTNAP2, PAFAH1B1 and TSNARE1) are seizure genes. ROBO1, the most
    upregulated gene, is an axon guidance receptor; PAFAH1B1 (LIS1) is a
    canonical neuronal migration gene.
  biological_processes:
  - preferred_term: regulation of transcription by RNA polymerase II
    term:
      id: GO:0006357
      label: regulation of transcription by RNA polymerase II
    modifier: DYSREGULATED
  downstream:
  - target: Impaired Axon Guidance and Neuronal Migration
    description: >-
      Dysregulation of ROBO1, PAFAH1B1 and related genes perturbs axonal
      pathfinding and cortical neuronal migration.
  - target: Cortical Network Hyperexcitability
    description: >-
      Dysregulation of CNTNAP2, TSNARE1, SYT1 and other synaptic and
      neuron-glia genes lowers the threshold for seizure generation.
  - target: Neural Progenitor Cell Apoptosis and Reduced Neurogenesis
    description: >-
      Under-expression of the SNIP1-dependent survival and neurogenesis
      programme is what makes progenitors die rather than differentiate.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Differentially expressed genes with a false discovery rate (FDR) adjusted p-value of <0.05 identified a list of 75 significantly upregulated genes, and 109 significantly downregulated genes"
    explanation: >-
      Quantifies the transcriptomic perturbation measured directly in affected
      individuals.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This includes five genes (ROBO1, SOX5, CNTNAP2, PAFAH1B1 and TSNARE1) associated with seizures, the cardinal feature of SNIP1-related disorder"
    explanation: >-
      Directly connects the measured expression changes to the cardinal
      phenotype through independently established seizure genes.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our gene transcript studies in affected individuals define altered gene expression profiles of a number of molecules with well-defined neurodevelopmental and neuropathological roles, potentially explaining clinical outcomes"
    explanation: >-
      The authors' own framing of this node as the mechanistic bridge between the
      molecular lesion and the clinical outcome.
- name: Impaired Axon Guidance and Neuronal Migration
  biological_scale: CELLULAR
  description: >-
    ROBO1, the most upregulated transcript in affected individuals, is a neural
    cell adhesion molecule family axon guidance receptor, and PAFAH1B1 is among
    the dysregulated genes associated with brain structural abnormality.
    Perturbation of axon guidance and cortical neuronal migration is the
    cell-biological step that best accounts for the observed white matter,
    corpus callosum and cortical ribbon abnormalities.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  - preferred_term: neural progenitor cell
    term:
      id: CL:0011020
      label: neural progenitor cell
  biological_processes:
  - preferred_term: axon guidance
    term:
      id: GO:0007411
      label: axon guidance
    modifier: DYSREGULATED
  - preferred_term: neuron migration
    term:
      id: GO:0001764
      label: neuron migration
    modifier: DYSREGULATED
  downstream:
  - target: Structural Brain Malformation and White Matter Abnormality
    description: >-
      Failed pathfinding and migration produce the hypomyelination, thin corpus
      callosum, ventriculomegaly and irregular cortical ribbon seen on MRI.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of these ROBO1 (roundabout guidance receptor 1), the gene identi- fied to be most upregulated in affected individuals with SNIP1-related disorder, is a member of the neural cell adhesion molecule (NCAM) family involved in axonal migration"
    explanation: >-
      Identifies the specific axon guidance receptor most strongly dysregulated
      in patients.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "includes two other genes (PAFAH1B1 and TOR1AIP1) associated with brain structural abnor- malities"
    explanation: >-
      PAFAH1B1 is the classical lissencephaly neuronal migration gene; its
      dysregulation supports a migration component. Marked PARTIAL because
      expression change in blood is an indirect proxy for a brain developmental
      process.
- name: Structural Brain Malformation and White Matter Abnormality
  biological_scale: TISSUE
  description: >-
    Neuroimaging is abnormal in essentially all individuals assessed. The
    reported spectrum comprises hydrocephalus, ventriculomegaly, white matter
    abnormalities, thin corpus callosum, hypomyelination, an irregular cortical
    ribbon that follows the undulating inner skull contour, Chiari malformation,
    absence of the septum pellucidum, hypoplastic optic nerves and septo-optic
    dysplasia. The cortical ribbon finding is mechanistically interesting because
    it couples the brain and calvarial phenotypes.
  biological_processes:
  - preferred_term: neuron migration
    term:
      id: GO:0001764
      label: neuron migration
    modifier: DECREASED
  downstream:
  - target: Severe Global Developmental Impairment
    description: >-
      Structural maldevelopment of cortex and white matter is the anatomical
      substrate of the profound psychomotor delay.
  - target: Ventriculomegaly
    description: >-
      Enlarged ventricles, with or without frank hydrocephalus, on MRI.
  - target: Abnormal Cerebral White Matter Morphology
    description: >-
      White matter abnormality and hypomyelination on MRI.
  - target: Hypoplasia of the Corpus Callosum
    description: >-
      A thin corpus callosum, reported in both published series.
  - target: Septo-Optic Dysplasia
    description: >-
      Midline forebrain malformation at the severe end of the imaging spectrum.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuro- imaging was available for 18 individuals, all confirmed to have abnormalities, including hydrocephalus, ventriculomegaly, white matter abnormalities, thin corpus callosum, hypo- myelination, irregular cortical ribbon, Chiari malformation, absence of the septum pelluci- dum, hypoplastic optic nerves and septo-optic dysplasia"
    explanation: >-
      Full imaging spectrum with an explicit denominator: 18 of 18 imaged
      individuals had abnormalities.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Magnetic resonance imaging reveals ventriculomegaly, thin corpus callosum, white matter abnormalities, and an undulating or ‘‘lumpy’’ skull surface (Figure 3, E). The cortical ribbon follows the irregular skull contour"
    explanation: >-
      Independent description of the imaging phenotype in the original three
      probands, including the coupling of cortical ribbon shape to the abnormal
      calvarium.
- name: Cortical Network Hyperexcitability
  biological_scale: TISSUE
  description: >-
    The combination of derepressed NF-kappaB and TGF-beta/Smad2 signalling in
    brain, dysregulated synaptic and neuron-glia genes (CNTNAP2, TSNARE1, SYT1),
    and structural cortical maldevelopment produces a diffusely hyperexcitable
    cortical network. EEG is abnormal in all individuals assessed, with diffuse
    background slowing and frequent focal or multifocal discharges and no single
    characteristic pattern.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: modulation of chemical synaptic transmission
    term:
      id: GO:0050804
      label: modulation of chemical synaptic transmission
    modifier: DYSREGULATED
  downstream:
  - target: Infantile-Onset Drug-Resistant Epilepsy
    description: >-
      A hyperexcitable cortical network generates the multifocal, multi-type,
      treatment-refractory seizures that define the disorder.
  - target: EEG Abnormality
    description: >-
      The electrographic readout of the hyperexcitable network: diffuse
      background slowing with frequent focal or multifocal discharges, abnormal
      in every individual assessed and with no characteristic pattern. Wired
      from this node rather than from the seizure node because the abnormality
      is a property of the network itself and is present interictally.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "EEG was abnormal in all individuals assessed, with no characteristic pattern, findings included diffuse background slowing and frequent focal or multifocal discharges"
    explanation: >-
      Electrophysiological confirmation of diffuse, non-localising cortical
      dysfunction rather than a single epileptogenic focus.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "temporal regions typically begin by 6 months of age and are accompanied by focal or generalized seizures that can manifest as dystonic posturing, drop attacks, myoclonic jerks, or generalized tonic-clonic events. Multiple intractable seizure types can afflict an individual patient"
    explanation: >-
      Dates the onset of electrographic hyperexcitability to the first six months
      of life and documents the multiple concurrent seizure types a single
      hyperexcitable network generates. The quotation begins mid-sentence
      because a figure caption is interleaved at that point in the extracted
      PDF text; the preceding clause reads "Multifocal spike-wave discharges
      from central, occipital, and".
- name: Infantile-Onset Drug-Resistant Epilepsy
  biological_scale: ORGANISM
  description: >-
    Every affected individual develops epilepsy. Seizure types include focal and
    generalised intractable seizures (myoclonic, absence, tonic-clonic) of
    infantile or childhood onset, and multiple intractable seizure types can
    afflict a single patient. Seizures may present initially as apnoea or
    breath-holding spells, and subclinical seizures occur. Febrile illness, sleep
    deprivation and hypoglycaemic episodes are recognised triggers. No
    antiepileptic medication has been identified that consistently provides
    effective seizure control.
  downstream:
  - target: Status Epilepticus
    description: >-
      Refractory seizures progress to status epilepticus with consequent
      developmental regression and, in some, permanent motor deficit.
  - target: Seizure
    description: >-
      The clinical seizure phenotype itself, universal in this disorder.
  - target: Drug-Resistant Epilepsy
    description: >-
      No anticonvulsant provides consistent control, and several individuals
      have multiple drug resistant epilepsy.
  - target: Apnea
    description: >-
      In some infants the first seizure manifestation is apnoea or
      breath-holding, a seizure-driven route to apnoea distinct from the
      airway-malacia route.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizures are a cardinal feature of the disorder with all affected individuals developing epilepsy. Seizure types include focal and generalised intractable seizures (myoclonic, absence, tonic-clonic) of infantile or childhood onset"
    explanation: >-
      Universality, seizure semiology and age at onset in the 35-individual
      cohort.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There were no antiepileptic medications identified that consistently provide effective seizure control (defined as manageable frequency of sei- zures) and several individuals display multiple drug resistant epilepsy"
    explanation: >-
      Establishes drug resistance as a defining property rather than an
      occasional complication, which is the basis for the treatment section's
      caution about disease-specific anticonvulsant recommendations.
- name: Status Epilepticus
  biological_scale: ORGANISM
  description: >-
    Refractory epilepsy in this disorder is not merely a comorbidity; it is an
    active driver of further neurological loss, and status epilepticus is the
    acute event through which that loss is delivered. Some individuals suffered
    severe developmental regression following status epilepticus, two with
    subsequent permanent hemiparesis. Preventing status epilepticus is named by
    the cohort authors as an explicit goal of anticonvulsant optimisation, which
    makes this the acquired and potentially preventable entry point to the
    acquired component of the phenotype.
  downstream:
  - target: Hypoxic-Ischaemic Secondary Brain Injury
    description: >-
      Prolonged seizure activity is the proximate cause of the secondary
      hypoxic-ischaemic insult the authors invoke to explain the acquired motor
      and developmental deficit.
  - target: Developmental Regression
    description: >-
      Loss of previously acquired skills following status epilepticus. Wired
      from this node rather than from the downstream injury node because the
      source attributes the regression directly to the status epilepticus event
      without asserting an intervening hypoxic mechanism.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Some individuals suf- fered severe developmental regression following status epilepticus, with two reported to have subsequent permanent hemiparesis"
    explanation: >-
      Documents seizure-driven regression and fixed motor deficit as acquired
      events on top of the congenital lesion. The "suf- fered" spelling is a PDF
      extraction artifact.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "maintain seizure control, and prevent status epilepticus and consequent"
    explanation: >-
      The authors name prevention of status epilepticus, and of the
      developmental regression that follows it, as an explicit management
      target, which is why this event is modelled as its own node.
- name: Hypoxic-Ischaemic Secondary Brain Injury
  biological_scale: TISSUE
  description: >-
    The tissue-level consequence of prolonged and inadequately controlled
    seizure activity. Individuals identified in late childhood or adolescence
    are often diagnosed with mixed-tone spastic quadriplegic cerebral palsy that
    the cohort authors attribute to hypoxic injury after long-term untreated or
    unrecognised seizures rather than to a primary pyramidal lesion. This is the
    acquired, and therefore potentially preventable, component of the phenotype.
  downstream:
  - target: Spastic Tetraplegia
    description: >-
      The mixed-tone spastic quadriplegic picture in late-ascertained
      individuals, attributed by the authors to hypoxic injury rather than to a
      primary pyramidal lesion.
  - target: Severe Global Developmental Impairment
    description: >-
      Seizure-related hypoxic injury compounds the developmental deficit already
      set by the structural brain malformation.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals identified in late childhood/adolescence are often diagnosed with a mixed tone spastic quadriplegic cerebral palsy, likely reflecting hypoxic injury after long-term untreated/unrecognise d seizures"
    explanation: >-
      Explains why late-ascertained individuals carry a cerebral palsy label and
      frames early seizure control as neuroprotective. The
      "unrecognise d" spelling is a PDF extraction artifact.
  notes: >-
    Split out of a former combined "Status Epilepticus and Hypoxic-Ischaemic
    Secondary Injury" node, which bundled a two-step chain. The hypoxic injury
    is an authors' attribution, not a measured finding: no imaging or
    neuropathological confirmation of hypoxic-ischaemic injury in genotyped
    individuals has been published, and the competing degenerative explanation
    is carried as an open question in discussions.
- name: Severe Global Developmental Impairment
  biological_scale: ORGANISM
  description: >-
    The convergent clinical endpoint of the neurological arm. Global
    developmental delay and hypotonia with hyporeflexia are present in all
    affected individuals, and developmental delay is characterised as severe and
    non-verbal. Most affected individuals nonetheless achieve independent
    ambulation between 3 and 10 years, and some communicate with signs, gestures
    and sounds, so the disorder is severe but not uniformly without motor
    progress.
  downstream:
  - target: Global Developmental Delay
    description: >-
      The clinical manifestation of the impaired neurodevelopmental endpoint.
  - target: Intellectual Disability
    description: >-
      The cognitive manifestation, universally severe and non-verbal.
  - target: Hypotonia
    description: >-
      Central hypotonia is present from the neonatal period in all affected
      individuals.
  - target: Hyporeflexia
    description: >-
      Weak or absent tendon reflexes accompany the hypotonia in all affected
      individuals.
  - target: Neonatal Feeding Failure and Aspiration Risk
    description: >-
      Poor feeding from birth is universal and is the entry point to the
      nutritional and pulmonary morbidity of the disorder.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Global developmen tal delay (severe, non-verbal) 100"
    explanation: >-
      Table 1 row giving the frequency and qualitative severity of the
      developmental phenotype in 35 evaluated individuals. Word-internal spacing
      is a PDF extraction artifact.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Most affected individuals achieved independent ambu- lation (age range 3–10 years), and some communicate with signs, gestures and sounds"
    explanation: >-
      Qualifies the severity: motor milestones are delayed but usually attained,
      which matters for prognostic counselling.
- name: Aberrant Craniofacial and Calvarial Morphogenesis
  biological_scale: TISSUE
  description: >-
    Cranial neural crest derived facial skeleton and the membranous calvarium are
    both affected. Skull morphology ranges from normocephaly to severe
    multi-suture craniosynostosis with a cloverleaf skull, and characteristically
    includes an irregular skull surface with variable calvarial thickness and
    bony dysplasia. Facial features comprise midface hypoplasia, a wide mouth
    with downturned corners and thin cupid's bow upper lip, large tongue, high
    arched palate, microretrognathia with or without Pierre Robin sequence and
    cleft palate, malocclusion, small upturned bulbous nose, long palpebral
    fissures, and proptosis where craniosynostosis is present.
  cell_types:
  - preferred_term: migratory cranial neural crest cell
    term:
      id: CL:0000008
      label: migratory cranial neural crest cell
  - preferred_term: osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  biological_processes:
  - preferred_term: embryonic cranial skeleton morphogenesis
    term:
      id: GO:0048701
      label: embryonic cranial skeleton morphogenesis
    modifier: ABNORMAL
  downstream:
  - target: Abnormal Skull Morphology
    description: >-
      The calvarial arm: irregular skull surface, variable calvarial thickness
      and bony dysplasia in every affected individual.
  - target: Craniosynostosis
    description: >-
      Premature suture fusion at the severe end of the calvarial spectrum.
  - target: Cloverleaf Skull
    description: >-
      The most extreme calvarial outcome: multi-suture fusion producing a
      trilobar skull.
  - target: Proptosis
    description: >-
      A consequence of the reduced orbital volume produced by craniosynostosis,
      and reported only in individuals who have it.
  - target: Midface Retrusion
    description: >-
      Hypoplasia of the cranial-neural-crest-derived midfacial skeleton.
  - target: High Palate
    description: >-
      Palatal shelf morphology abnormality, present in every affected
      individual.
  - target: Wide Mouth
    description: >-
      Wide mouth with downturned corners and a thin cupid's bow upper lip.
  - target: Macroglossia
    description: >-
      Large tongue, part of the oral component of the gestalt.
  - target: Micrognathia
    description: >-
      Microretrognathia from mandibular hypoplasia.
  - target: Pierre-Robin Sequence
    description: >-
      Mandibular hypoplasia severe enough to displace the tongue and obstruct
      palatal closure, the classical sequence.
  - target: Cleft Palate
    description: >-
      Failure of palatal shelf fusion, reported within the Pierre Robin
      sequence subset.
  - target: Bulbous Nose
    description: >-
      Small upturned bulbous nose, a consistent element of the facial gestalt.
  - target: Long Palpebral Fissure
    description: >-
      Periorbital component of the craniofacial gestalt.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Skull morphological abnormalities were observed and ranged from normocephaly to severe multi-suture craniosynostosis with Cloverleaf appearance of the skull in five individ- uals, and included an irregular skull surface with variable calvarium thickness and bony dys- plasia"
    explanation: >-
      Defines the calvarial spectrum, including the specific count of five
      individuals with cloverleaf skull.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Craniofacial features (Fig 1A–1D) include midface hypoplasia, a wide mouth with downturned corners and thin cupids bow upper lip, large tongue, high arched palate, microre- trognathia (Pierre Robin sequence with or without cleft palate in three patients), malocclusion, small upturned bulbous nose, long palpebral fissures and proptosis (in individuals with cranio- synostosis"
    explanation: >-
      The complete craniofacial gestalt as described in the 35-individual
      cohort.
- name: Aberrant Cardiac and Outflow Tract Morphogenesis
  biological_scale: TISSUE
  description: >-
    Congenital cardiac malformation affects a majority of individuals and spans
    the septation, valvular and aortic arch compartments: hypoplastic left heart
    syndrome, aortic stenosis and bicuspid aortic valve, aortic coarctation,
    aortic root dilatation, atrial and ventricular septal defects, patent ductus
    arteriosus, pulmonary artery stenosis and mitral regurgitation. This
    distribution is characteristic of perturbed TGF-beta/BMP signalling in
    cardiac neural crest and second heart field derivatives.
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: heart morphogenesis
    term:
      id: GO:0003007
      label: heart morphogenesis
    modifier: ABNORMAL
  downstream:
  - target: Abnormal Heart Morphology
    description: >-
      The full congenital cardiac lesion spectrum, spanning septation, valvular
      and aortic arch compartments.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a variable spectrum of congenital cardiac defects (60% of individuals), including hypoplastic left heart syndrome, aortic stenosis and bicuspid aortic valve, aortic coarctation, aortic root dilatation, atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosus (PDA), pulmonary artery stenosis and mitral valve regurgitation"
    explanation: >-
      Frequency and full lesion spectrum of congenital heart disease in the
      cohort.
- name: Impaired Myocardial Stress Adaptation
  biological_scale: TISSUE
  description: >-
    Distinct from the structural congenital lesions, a minority of individuals
    develop cardiomyopathy, specifically left ventricular non-compaction. Mouse
    work showing that SNIP1 deficiency exacerbates and SNIP1 overexpression
    rescues pressure-overload hypertrophy through NF-kappaB provides a candidate
    mechanism for a myocardial rather than a morphogenetic contribution, though
    this link has not been demonstrated in patients.
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  downstream:
  - target: Left Ventricular Noncompaction Cardiomyopathy
    description: >-
      The myocardial phenotype seen in a minority, distinct from the structural
      congenital lesions.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "12% of affected individuals developed cardiomyopathy (left ventricular non- compaction"
    explanation: >-
      Documents the cardiomyopathy subtype and its frequency in the cohort.
  - reference: PMID:27912208
    reference_title: "Smad Nuclear Interacting Protein 1 Acts as a Protective Regulator of Pressure Overload-Induced Pathological Cardiac Hypertrophy."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "our findings demonstrated that SNIP1 had protective effects in pressure overload-induced pathological cardiac hypertrophy via inhibition of nuclear factor-κB signaling"
    explanation: >-
      Candidate NF-kappaB-dependent myocardial mechanism. Marked PARTIAL because
      it is an acquired-hypertrophy model in mouse and no myocardial mechanism
      has been shown in individuals with the SNIP1 founder variant.
- name: Aberrant Laryngeal and Pharyngeal Cartilage Development
  biological_scale: TISSUE
  description: >-
    Three quarters of individuals have upper airway abnormalities:
    laryngomalacia, pharyngomalacia and subglottic stenosis of variable
    severity, producing a weak cry, stridor and apnoea and occasionally
    requiring tracheostomy and home oxygen. The common feature of malacia and
    subglottic narrowing is inadequate laryngeal and pharyngeal cartilage
    support, and TGF-beta/BMP pathway disruption characteristically affects
    connective tissue and cartilage, which is why this node is placed downstream
    of the TGF-beta arm. The mechanism has not been demonstrated directly in
    this disorder and the placement is an inference, flagged as such below.
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  downstream:
  - target: Laryngomalacia
    description: >-
      Inadequate supraglottic cartilage support collapses the airway on
      inspiration.
  - target: Subglottic Stenosis
    description: >-
      Cricoid-level narrowing, the fixed rather than dynamic form of the airway
      lesion.
  - target: Apnea
    description: >-
      Airway obstruction is the second, non-seizure route to apnoea in this
      disorder.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals commonly displayed upper airway respiratory difficulties in the neonatal period, including laryngomalacia, pharyngomalacia and subglottic stenosis of var- iable severity, causing a weak cry, stridor and apnea, occasionally requiring tracheostomy and supplementary home oxygen"
    explanation: >-
      Documents the airway phenotype, its neonatal onset and its severity range.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Genetic variants leading to disruption of the TGF-β/BMP molecular sig- nalling pathway have been implicated in the pathogenesis of a number of inherited disorders, in particular connective tissue disorders associated with craniofacial (e.g. cleft palate and cra- niosynostosis), cardiovascular (e.g. aortic aneurysm and syndromic aortopathies), and muscu- loskeletal (e.g. disorders of endochondral ossification, bone growth, remodelling and limb development) outcomes"
    explanation: >-
      The basis for placing the airway phenotype downstream of the TGF-beta arm.
      Marked PARTIAL because the quotation establishes that TGF-beta/BMP
      disruption causes connective tissue disease in general, not that it causes
      the airway malacia in this specific disorder.
  notes: >-
    The causal placement of this node is inferred from the general connective
    tissue and cartilage consequences of TGF-beta/BMP pathway disruption, not
    demonstrated in SNIP1 patients or models. It is curated because the airway
    phenotype is frequent (75%) and clinically dominant in the neonatal period,
    and leaving it mechanistically unexplained would be a larger omission than
    an explicitly flagged inference.
- name: Aberrant Distal Limb and Digit Development
  biological_scale: TISSUE
  description: >-
    Distal limb findings comprise short hands with tapered fingers in just over
    half of individuals, plus brachydactyly, broad thumbs, single palmar crease,
    congenital talipes equinovarus, pes planus and toenail hypoplasia. The
    discovery paper's mechanistic rationale is that disruption of c-MYC or
    CBP/p300 signalling in mice produces abnormal development of brain, skull,
    craniofacial bones and distal limbs, which is precisely the combination seen
    here; the brachydactyly syndromes are separately TGF-beta pathway disorders.
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  downstream:
  - target: Tapered Finger
    description: >-
      Short hands with tapered fingers, the commonest distal limb finding.
  - target: Brachydactyly
    description: >-
      Shortened digits, the phenotype shared with the TGF-beta pathway
      brachydactyly syndromes.
  - target: Broad Thumb
    description: >-
      Broad thumbs, reported in both published series.
  - target: Talipes Equinovarus
    description: >-
      Congenital clubfoot, the distal lower-limb component.
  - target: Hypoplastic Toenails
    description: >-
      Nail hypoplasia, a distal appendage patterning defect.
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "Disruption of c-Myc or CBP/p300 signaling in mice can result in abnormal development of the brain, skull, craniofacial bones, and distal limbs"
    explanation: >-
      The discovery paper's own mechanistic rationale linking the SNIP1
      transcriptional co-regulation arm to the observed distal limb findings.
      Marked PARTIAL because it is a mouse-derived inference cited by the
      authors, not a measurement in SNIP1 patients.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other dysmorphic features include brachydactyly, broad thumbs, single palmar crease, congenital talipes equinovarus, pes planus, toenail hypoplasia and pectus excavatum"
    explanation: >-
      Enumerates the distal limb and appendage findings this node accounts for.
- name: Neonatal Feeding Failure and Aspiration Risk
  biological_scale: ORGANISM
  description: >-
    Poor feeding in the neonatal period is universal, and pulmonary aspiration
    with or without a gastrostomy tube affects 46%. This is the single most
    actionable node in the entry: elective gastrostomy is one of two
    interventions the cohort authors single out as able to reduce
    hospitalisations, alleviate suffering and prolong life. The proximate
    mechanism is not established, and more than one contributor is plausible
    (central hypotonia with poor suck and swallow coordination, upper airway
    malacia, and gastroesophageal reflux are all documented in the same
    individuals), so no single mechanism is asserted.
  downstream:
  - target: Feeding Difficulties
    description: >-
      Universal poor feeding from the neonatal period.
  - target: Aspiration
    description: >-
      Pulmonary aspiration, the principal driver of respiratory morbidity and
      hospitalisation.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Poor feeding in the neonatal period is universal and many require a gastrostomy tube to both aid nutrition and reduce risk of aspiration pneumonia"
    explanation: >-
      Establishes universality and the direct link from feeding failure to
      aspiration pneumonia risk.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intrauterine growth retardation (IUGR) and failure to thrive was also common"
    explanation: >-
      Places the postnatal nutritional failure in the context of prenatal growth
      restriction.
  notes: >-
    The proximate mechanism of feeding failure is deliberately left unasserted.
    Neither published source attributes it to a specific cause, and hypotonia,
    airway malacia and reflux are each independently documented in the cohort.
    An earlier revision wired this node to Small for Gestational Age; that edge
    was removed because small-for-gestational-age status is determined at birth
    and cannot be caused by a postnatal event. The retained IUGR snippet
    documents co-occurrence of prenatal growth restriction with postnatal
    failure to thrive, not causation in either direction, so Small for
    Gestational Age is now left unwired.
phenotypes:
- name: Global Developmental Delay
  category: Nervous System
  description: >-
    Present in all 35 comprehensively evaluated individuals and characterised as
    severe and non-verbal. In the original three probands, affected children had
    severe psychomotor delay and did not learn to walk or speak, though the later
    larger cohort found that most eventually achieve independent ambulation.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  frequency: OBLIGATE
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Global developmen tal delay (severe, non-verbal) 100"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 100% affected. Word-internal spacing
      is a PDF extraction artifact.
  notes: >-
    Frequency band OBLIGATE derives from 35/35 in the founder cohort
    (PMID:34570759 Table 1). This is a single extended Amish kindred homozygous
    for one allele, so the band describes that genotype in that population and is
    not a general disease frequency.
- name: Intellectual Disability
  category: Nervous System
  description: >-
    Intellectual disability is one of the cardinal features of the condition.
    Affected individuals are non-verbal; some show behavioural responses to
    language but do not socially engage or follow verbal commands, while some
    communicate with signs, gestures and sounds.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The cardinal clinical features of the condition include hypotonia, global developmental delay, intellectual disability, seizures, and a characteristic craniofacial appearance"
    explanation: >-
      Names intellectual disability among the cardinal features of the disorder.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Some children show behavioral responses to language, but they do not socially engage or follow verbal commands"
    explanation: >-
      Qualitative characterisation of the cognitive and communicative level in
      the original probands.
  notes: >-
    No band assigned. Intellectual disability is named as cardinal but is not a
    separate row in the Table 1 frequency tabulation, which reports "global
    developmental delay (severe, non-verbal)" instead. Rather than reuse the
    developmental delay denominator for a different construct, the band is
    omitted.
- name: Seizure
  category: Nervous System
  description: >-
    Universal infantile- or childhood-onset epilepsy. Seizure types include focal
    and generalised intractable seizures - myoclonic, absence and tonic-clonic -
    and multiple intractable seizure types can afflict one individual. In some
    infants seizures presented initially as apnoea or breath-holding spells, and
    subclinical seizures were detected in six individuals. Febrile illness, sleep
    deprivation and hypoglycaemic episodes can trigger or exacerbate seizures.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  frequency: OBLIGATE
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizures are a cardinal feature of the disorder with all affected individuals developing epilepsy"
    explanation: >-
      Explicit statement of 100% penetrance of epilepsy in the evaluated cohort,
      corroborating the Table 1 figure of 100%.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizures can be triggered or exacerbated by febrile illness, sleep deprivation and hypoglycemic episodes"
    explanation: >-
      Documents the modifiable seizure triggers, which is directly actionable in
      management.
  notes: >-
    Frequency band OBLIGATE derives from 35/35 in the founder cohort
    (PMID:34570759 Table 1, "Seizures 100%"), supported by the prose statement
    that all affected individuals develop epilepsy. Founder-cohort derived.
- name: Drug-Resistant Epilepsy
  category: Nervous System
  description: >-
    No antiepileptic medication has been identified that consistently provides
    effective seizure control, and several individuals display multiple drug
    resistant epilepsy. This is the single most consequential management problem
    in the disorder.
  phenotype_term:
    preferred_term: Refractory drug response
    term:
      id: HP:0020174
      label: Refractory drug response
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There were no antiepileptic medications identified that consistently provide effective seizure control (defined as manageable frequency of sei- zures) and several individuals display multiple drug resistant epilepsy"
    explanation: >-
      Direct statement of pharmacoresistance in the cohort. The "sei- zures"
      spelling is a PDF extraction artifact.
  notes: >-
    No frequency band. Pharmacoresistance is described qualitatively ("several
    individuals") without a denominator, so per curation policy the band is
    omitted rather than guessed. HPO has no "drug-resistant epilepsy" class, so
    the binding is HP:0020174 Refractory drug response (a descendant of
    HP:0000118 Phenotypic abnormality via HP:0020169 Abnormal drug response),
    with the epilepsy context carried by the phenotype name and description.
    A previous revision bound this phenotype to HP:0002353 EEG abnormality,
    which is a different concept rather than a broader one; the electrographic
    finding now has its own phenotype entry.
- name: EEG Abnormality
  category: Nervous System
  description: >-
    EEG was abnormal in every individual assessed, with no characteristic
    pattern. Reported findings include diffuse background slowing and frequent
    focal or multifocal discharges, and in the original probands multifocal
    spike-wave discharges from central, occipital and temporal regions typically
    beginning by six months of age. The absence of a characteristic pattern
    means EEG supports rather than establishes the diagnosis.
  phenotype_term:
    preferred_term: EEG abnormality
    term:
      id: HP:0002353
      label: EEG abnormality
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "EEG was abnormal in all individuals assessed, with no characteristic pattern, findings included diffuse background slowing and frequent focal or multifocal discharges"
    explanation: >-
      Establishes that the electrographic abnormality is present in all assessed
      individuals and describes its non-specific character.
  notes: >-
    No frequency band is asserted. The source states the finding was present in
    all individuals assessed but does not give the number assessed, so there is
    no denominator; consistent with the rest of this entry a band is omitted
    rather than inferred from the 35-individual founder cohort denominator,
    which would misrepresent an unstated assessment subset. Split out of the
    Drug-Resistant Epilepsy phenotype, which previously carried this snippet
    under an HP:0002353 binding that did not match its own name.
- name: Hypotonia
  category: Nervous System
  description: >-
    Neonatal-onset hypotonia present in all evaluated individuals, part of the
    presenting picture together with poor feeding.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  frequency: OBLIGATE
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypotonia 100"
    explanation: >-
      Table 1, n = 35 evaluated individuals.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected neonates are hypotonic and feed poorly"
    explanation: >-
      Establishes neonatal onset in the original probands.
  notes: >-
    Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort
    derived, not a general disease frequency.
- name: Hyporeflexia
  category: Nervous System
  description: >-
    Weak or absent tendon reflexes accompany the hypotonia in all evaluated
    individuals, giving a hypotonic-hyporeflexic picture that can suggest a
    peripheral neuromuscular disorder on first assessment.
  phenotype_term:
    preferred_term: Hyporeflexia
    term:
      id: HP:0001265
      label: Hyporeflexia
  frequency: OBLIGATE
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hyporeflexi a 100"
    explanation: >-
      Table 1, n = 35 evaluated individuals. Word-internal spacing is a PDF
      extraction artifact.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Examination typically reveals a subdued child with strabismus, slow horizontal nystagmus, hypotonia, and weak or absent tendon reflexes"
    explanation: >-
      Independent description of the combined hypotonic-hyporeflexic examination
      findings.
  notes: >-
    Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort
    derived.
- name: Abnormal Skull Morphology
  category: Head and Neck
  description: >-
    Abnormal skull shape was present in every evaluated individual, ranging from
    normocephaly with an irregular ("lumpy") calvarial surface and variable
    calvarial thickness to severe multi-suture craniosynostosis with a cloverleaf
    skull. This is the feature that gave the condition its original descriptive
    name, symptomatic epilepsy and skull dysplasia.
  phenotype_term:
    preferred_term: Abnormal skull morphology
    term:
      id: HP:0000929
      label: Abnormal skull morphology
  frequency: OBLIGATE
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Abnormal skull shape (irregular surface, craniosyno stosis) 100"
    explanation: >-
      Table 1, n = 35 evaluated individuals. Word-internal spacing is a PDF
      extraction artifact.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Symptomatic epilepsy and skull dysplasia. Affected neonates are hypotonic and feed poorly"
    explanation: >-
      The original descriptive disease name pairing epilepsy with skull
      dysplasia.
  notes: >-
    Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort
    derived.
- name: Craniosynostosis
  category: Head and Neck
  description: >-
    A subset of individuals have craniosynostosis, in its most severe form
    multi-suture fusion producing a cloverleaf skull. Craniosynostosis is the
    reason some individuals have proptosis.
  phenotype_term:
    preferred_term: Craniosynostosis
    term:
      id: HP:0001363
      label: Craniosynostosis
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "ranged from normocephaly to severe multi-suture craniosynostosis with Cloverleaf appearance of the skull in five individ- uals"
    explanation: >-
      Establishes that craniosynostosis occurs in this disorder and spans a
      range up to severe multi-suture fusion. The "individ- uals" spelling is a
      PDF extraction artifact.
  notes: >-
    Deliberately unbanded. The only quotable count in the source, five
    individuals, is specifically the severe multi-suture cloverleaf subgroup,
    and that count now carries its own band on the Cloverleaf Skull phenotype.
    Craniosynostosis of any degree has no published denominator of its own:
    milder craniosynostosis is subsumed in the 100% "abnormal skull shape" row
    of Table 1, which is not a craniosynostosis row. Per this entry's one-band,
    one-denominator rule the band is omitted here rather than inherited from the
    cloverleaf subgroup, which would understate the true proportion.
- name: Cloverleaf Skull
  category: Head and Neck
  description: >-
    The severe end of the calvarial spectrum: multi-suture craniosynostosis
    producing a trilobar cloverleaf skull, reported in five individuals in the
    founder cohort. This is the form associated with proptosis and the one that
    raises the question of raised intracranial pressure.
  phenotype_term:
    preferred_term: Cloverleaf skull
    term:
      id: HP:0002676
      label: Cloverleaf skull
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "ranged from normocephaly to severe multi-suture craniosynostosis with Cloverleaf appearance of the skull in five individ- uals"
    explanation: >-
      Gives the count of individuals with the severe cloverleaf form, 5 of 35.
      The "individ- uals" spelling is a PDF extraction artifact.
  notes: >-
    Frequency band OCCASIONAL derived from 5/35 = 14%. Founder-cohort derived:
    the denominator is the 35 comprehensively evaluated individuals of the Old
    Order Amish p.Glu366Gly kindred, which is largely one extended family, so
    this is a kindred proportion and not a general disease frequency. Split out
    of the Craniosynostosis phenotype so that the 5/35 count bands the subgroup
    it actually counts.
- name: High Palate
  category: Head and Neck
  description: >-
    A high arched palate was present in every evaluated individual and is part of
    the recognisable craniofacial gestalt.
  phenotype_term:
    preferred_term: High palate
    term:
      id: HP:0000218
      label: High palate
  frequency: OBLIGATE
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "High arched palate 100"
    explanation: >-
      Table 1, n = 35 evaluated individuals.
  notes: >-
    Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort
    derived.
- name: Wide Mouth
  category: Head and Neck
  description: >-
    A wide mouth with downturned corners and a thin cupid's bow upper lip was
    present in every evaluated individual. Together with midface hypoplasia and
    the small upturned bulbous nose this constitutes the characteristic facial
    appearance.
  phenotype_term:
    preferred_term: Wide mouth
    term:
      id: HP:0000154
      label: Wide mouth
  frequency: OBLIGATE
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Wide mouth with cupids bow upper lip 100"
    explanation: >-
      Table 1, n = 35 evaluated individuals.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Dysmorphic features that evolve over time include a bulbous nose, wide mouth and tongue, broad jaw with protuberant angles, short hands, short tapered fingers, and broad thumbs"
    explanation: >-
      Independent description of the evolving dysmorphic gestalt in the original
      probands.
  notes: >-
    Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort
    derived.
- name: Midface Retrusion
  category: Head and Neck
  description: >-
    Midface hypoplasia is listed first among the craniofacial features of the
    disorder.
  phenotype_term:
    preferred_term: Midface retrusion
    term:
      id: HP:0011800
      label: Midface retrusion
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Craniofacial features (Fig 1A–1D) include midface hypoplasia, a wide mouth with downturned corners and thin cupids bow upper lip"
    explanation: >-
      Names midface hypoplasia as a craniofacial feature of the disorder.
  notes: >-
    No band. Midface hypoplasia is described qualitatively in the craniofacial
    narrative and does not appear as a numbered row in Table 1, so no denominator
    is available.
- name: Micrognathia
  category: Head and Neck
  description: >-
    Microretrognathia occurs in a substantial minority, with Pierre Robin
    sequence, with or without cleft palate, in three individuals.
  phenotype_term:
    preferred_term: Micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  frequency: FREQUENT
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Micrognath ia with/wi thout Pierre Robin sequence 30"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 30%. Word-internal spacing is a PDF
      extraction artifact.
  notes: >-
    Frequency band FREQUENT derived from the 30% Table 1 figure in the founder
    cohort, which sits at the lower boundary of the 30-79% band. Founder-cohort
    derived.
- name: Pierre-Robin Sequence
  category: Head and Neck
  description: >-
    Three individuals in the evaluated cohort had Pierre Robin sequence, with or
    without cleft palate, as the severe end of the micrognathia spectrum.
  phenotype_term:
    preferred_term: Pierre-Robin sequence
    term:
      id: HP:0000201
      label: Pierre-Robin sequence
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "microre- trognathia (Pierre Robin sequence with or without cleft palate in three patients"
    explanation: >-
      Explicit count of three individuals with Pierre Robin sequence.
  notes: >-
    Frequency band OCCASIONAL derived from 3/35 = 9% in the founder cohort.
    Founder-cohort derived.
- name: Cleft Palate
  category: Head and Neck
  description: >-
    Cleft palate occurs in some individuals with Pierre Robin sequence.
  phenotype_term:
    preferred_term: Cleft palate
    term:
      id: HP:0000175
      label: Cleft palate
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "microre- trognathia (Pierre Robin sequence with or without cleft palate in three patients"
    explanation: >-
      Cleft palate is reported only as an optional component of Pierre Robin
      sequence in three patients, so the number of individuals with a cleft is
      not stated. Marked PARTIAL for that reason.
  notes: >-
    No band. The source gives "with or without cleft palate in three patients",
    so the cleft-specific numerator is unknown even within the three-patient
    subset.
- name: Macroglossia
  category: Head and Neck
  description: >-
    A large tongue is part of the craniofacial gestalt and was also described in
    the original probands as a wide mouth and tongue.
  phenotype_term:
    preferred_term: Macroglossia
    term:
      id: HP:0000158
      label: Macroglossia
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "thin cupids bow upper lip, large tongue, high arched palate"
    explanation: >-
      Names large tongue among the craniofacial features.
  notes: >-
    No band; large tongue is not a numbered Table 1 row.
- name: Bulbous Nose
  category: Head and Neck
  description: >-
    A small upturned bulbous nose is a consistent element of the facial gestalt
    in both published cohorts.
  phenotype_term:
    preferred_term: Bulbous nose
    term:
      id: HP:0000414
      label: Bulbous nose
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "malocclusion, small upturned bulbous nose, long palpebral fissures and proptosis"
    explanation: >-
      Names the nasal morphology in the craniofacial description.
  notes: >-
    No band; not a numbered Table 1 row.
- name: Long Palpebral Fissure
  category: Eye
  description: >-
    Long palpebral fissures contribute to the recognisable facial appearance.
  phenotype_term:
    preferred_term: Long palpebral fissure
    term:
      id: HP:0000637
      label: Long palpebral fissure
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "malocclusion, small upturned bulbous nose, long palpebral fissures and proptosis"
    explanation: >-
      Names long palpebral fissures in the craniofacial description.
  notes: >-
    No band; not a numbered Table 1 row.
- name: Proptosis
  category: Eye
  description: >-
    Proptosis occurs specifically in those individuals who have craniosynostosis,
    consistent with reduced orbital volume.
  phenotype_term:
    preferred_term: Proptosis
    term:
      id: HP:0000520
      label: Proptosis
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "long palpebral fissures and proptosis (in individuals with cranio- synostosis"
    explanation: >-
      Conditions proptosis explicitly on the presence of craniosynostosis.
  notes: >-
    No band; the source conditions this finding on craniosynostosis without
    giving a numerator.
- name: Abnormal Heart Morphology
  category: Cardiovascular
  description: >-
    Congenital cardiac defects affect a majority. The reported spectrum comprises
    hypoplastic left heart syndrome, aortic stenosis, bicuspid aortic valve,
    aortic coarctation, aortic root dilatation, atrial septal defect, ventricular
    septal defect, patent ductus arteriosus, pulmonary artery stenosis and mitral
    valve regurgitation.
  phenotype_term:
    preferred_term: Abnormal heart morphology
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  frequency: FREQUENT
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Congenital heart defects (ASD, VSD, aortic coarctation ) 60"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 60%, which falls in the FREQUENT
      (30-79%) band. Spacing before the parenthesis is a PDF extraction
      artifact.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical anomalies found in some patients include subglottic stenosis, aortic stenosis, bicuspid aortic valve"
    explanation: >-
      Independent documentation of left-sided outflow lesions in the original
      probands.
  notes: >-
    Frequency band FREQUENT derived from 60% in the founder cohort
    (PMID:34570759 Table 1). Umbrella node for congenital heart disease of any
    type; the individual lesions are not separately banded because per-lesion
    denominators are not published. Founder-cohort derived.
- name: Left Ventricular Noncompaction Cardiomyopathy
  category: Cardiovascular
  description: >-
    A minority develop cardiomyopathy, specifically left ventricular
    non-compaction. This is distinct from the structural congenital lesions and
    warrants ongoing rather than one-off cardiac assessment.
  phenotype_term:
    preferred_term: Left ventricular noncompaction cardiomyopathy
    term:
      id: HP:0011664
      label: Left ventricular noncompaction cardiomyopathy
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "12% of affected individuals developed cardiomyopathy (left ventricular non- compaction"
    explanation: >-
      Prose figure of 12%, matching the Table 1 cardiomyopathy row, with the
      subtype named.
  notes: >-
    Frequency band OCCASIONAL derived from 12% in the founder cohort.
    Founder-cohort derived.
- name: Laryngomalacia
  category: Respiratory
  description: >-
    Upper airway abnormalities affect three quarters of individuals and include
    laryngomalacia, pharyngomalacia and subglottic stenosis of variable severity,
    causing a weak cry, stridor and apnoea, occasionally requiring tracheostomy
    and supplementary home oxygen.
  phenotype_term:
    preferred_term: Laryngomalacia
    term:
      id: HP:0001601
      label: Laryngomalacia
  frequency: FREQUENT
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Upper airway abnormalit ies (laryngoma lacia, apnoea, stridor) 75"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 75%. Word-internal spacing is a PDF
      extraction artifact.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals commonly displayed upper airway respiratory difficulties in the neonatal period, including laryngomalacia, pharyngomalacia and subglottic stenosis of var- iable severity, causing a weak cry, stridor and apnea, occasionally requiring tracheostomy and supplementary home oxygen"
    explanation: >-
      Full description of the airway phenotype and its management burden.
  notes: >-
    Frequency band FREQUENT derived from the 75% Table 1 figure for "upper airway
    abnormalities", of which laryngomalacia is the named exemplar. The band
    therefore applies to the composite airway category rather than to
    laryngomalacia in isolation. Founder-cohort derived.
- name: Subglottic Stenosis
  category: Respiratory
  description: >-
    Subglottic stenosis is part of the upper airway spectrum and was documented
    in the original probands as well as in the larger cohort.
  phenotype_term:
    preferred_term: Subglottic stenosis
    term:
      id: HP:0001607
      label: Subglottic stenosis
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical anomalies found in some patients include subglottic stenosis, aortic stenosis, bicuspid aortic valve"
    explanation: >-
      Documents subglottic stenosis in the original probands.
  notes: >-
    No band; reported as occurring in "some patients" without a denominator.
- name: Apnea
  category: Respiratory
  description: >-
    Apnoea arises from two distinct causes in this disorder, which matters for
    management: upper airway malacia, and seizures presenting as apnoeic or
    breath-holding spells. Early EEG is recommended in infants with suspected
    apnoeic episodes for exactly this reason.
  phenotype_term:
    preferred_term: Apnea
    term:
      id: HP:0002104
      label: Apnea
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In some infants, sei- zures initially presented as apnea or breath-holding spells and subclinical seizures were detected in six individuals"
    explanation: >-
      Documents seizure-related apnoea and the occurrence of subclinical
      seizures, the basis for the early-EEG recommendation.
  notes: >-
    No separate band. Apnoea is folded into the 75% "upper airway abnormalities"
    Table 1 row and also occurs as a seizure manifestation, so no clean
    denominator exists for apnoea as such.
- name: Feeding Difficulties
  category: Digestive
  description: >-
    Poor feeding in the neonatal period is universal, and many individuals
    require a gastrostomy tube both to support nutrition and to reduce the risk
    of aspiration pneumonia.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  frequency: OBLIGATE
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Feeding difficulties 100"
    explanation: >-
      Table 1, n = 35 evaluated individuals.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Poor feeding in the neonatal period is universal and many require a gastrostomy tube to both aid nutrition and reduce risk of aspiration pneumonia"
    explanation: >-
      Corroborates universality and states the management consequence.
  notes: >-
    Frequency band OBLIGATE from 35/35 in the founder cohort. Founder-cohort
    derived.
- name: Aspiration
  category: Digestive
  description: >-
    Pulmonary aspiration, with or without a gastrostomy tube in place, affects
    nearly half of individuals and is a principal driver of hospitalisation.
  phenotype_term:
    preferred_term: Aspiration
    term:
      id: HP:0002835
      label: Aspiration
  frequency: FREQUENT
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pulmonary aspiration with/withou t gastrostom y tube 46"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 46%. Word-internal spacing is a PDF
      extraction artifact.
  notes: >-
    Frequency band FREQUENT derived from 46% in the founder cohort.
    Founder-cohort derived.
- name: Gastroesophageal Reflux
  category: Digestive
  description: >-
    Gastroesophageal reflux is among the gastrointestinal features reported,
    alongside paraoesophageal hernia, intestinal malrotation and hepatomegaly.
  phenotype_term:
    preferred_term: Gastroesophageal reflux
    term:
      id: HP:0002020
      label: Gastroesophageal reflux
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Gastrointestinal features reported include gastroesophageal reflux, paraoesophageal hernia (type III), intestinal malrota- tion, hepatomegaly and umbilical and inguinal hernias"
    explanation: >-
      Lists the gastrointestinal spectrum of the disorder.
  notes: >-
    No band; reported qualitatively without a denominator.
- name: Intestinal Malrotation
  category: Digestive
  description: >-
    Intestinal malrotation is one of the congenital gastrointestinal anomalies
    reported, and is the reason an upper gastrointestinal contrast study is
    recommended at diagnosis.
  phenotype_term:
    preferred_term: Intestinal malrotation
    term:
      id: HP:0002566
      label: Intestinal malrotation
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Gastrointestinal features reported include gastroesophageal reflux, paraoesophageal hernia (type III), intestinal malrota- tion, hepatomegaly and umbilical and inguinal hernias"
    explanation: >-
      Names intestinal malrotation among the reported gastrointestinal features.
  notes: >-
    No band; reported qualitatively without a denominator.
- name: Umbilical Hernia
  category: Digestive
  description: >-
    Umbilical and inguinal hernias together affect about a fifth of individuals.
  phenotype_term:
    preferred_term: Umbilical hernia
    term:
      id: HP:0001537
      label: Umbilical hernia
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hernias (umbilica l, inguinal) 21"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 21%. Word-internal spacing is a PDF
      extraction artifact.
  notes: >-
    Frequency band OCCASIONAL derived from the 21% Table 1 figure, which pools
    umbilical and inguinal hernias; the umbilical-specific rate is therefore
    lower than 21%. Founder-cohort derived.
- name: Small for Gestational Age
  category: Prenatal and Birth
  description: >-
    Just over half of individuals were small for gestational age, and intrauterine
    growth retardation with subsequent failure to thrive was common.
  phenotype_term:
    preferred_term: Small for gestational age
    term:
      id: HP:0001518
      label: Small for gestational age
  frequency: FREQUENT
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Small for gestational age 54"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 54%.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intrauterine growth retardation (IUGR) and failure to thrive was also common"
    explanation: >-
      Corroborating prose linking prenatal growth restriction to postnatal
      failure to thrive.
  notes: >-
    Frequency band FREQUENT derived from 54% in the founder cohort.
    Founder-cohort derived.
- name: Hypothyroidism
  category: Endocrine
  description: >-
    Hypothyroidism affects a quarter of individuals. The clinical guidance
    emphasises that hypothyroidism and hypoglycaemia are easily treatable and
    should be actively monitored for.
  phenotype_term:
    preferred_term: Hypothyroidism
    term:
      id: HP:0000821
      label: Hypothyroidism
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypothyroid ism 25"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 25%. Word-internal spacing is a PDF
      extraction artifact.
  notes: >-
    Frequency band OCCASIONAL derived from 25% in the founder cohort.
    Founder-cohort derived.
- name: Hypoglycemia
  category: Endocrine
  description: >-
    Hypoglycaemia affects about a fifth of individuals and is doubly important
    because hypoglycaemic episodes are also a recognised seizure trigger in this
    disorder.
  phenotype_term:
    preferred_term: Hypoglycemia
    term:
      id: HP:0001943
      label: Hypoglycemia
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypoglycaem ia 21"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 21%. Word-internal spacing is a PDF
      extraction artifact.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Endocrine abnormalities including hypoglyce- mia, hypothyroidism, hypothermia and dyshormonogenesis were identified in a small propor- tion of patients"
    explanation: >-
      Places hypoglycaemia in the wider endocrine spectrum, which also includes
      hypothermia and dyshormonogenesis.
  notes: >-
    Frequency band OCCASIONAL derived from 21% in the founder cohort.
    Founder-cohort derived.
- name: Strabismus
  category: Eye
  description: >-
    Horizontal nystagmus and/or strabismus affect nearly half of individuals.
    Myopia is also reported.
  phenotype_term:
    preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  frequency: FREQUENT
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Horizontal nystagmus and/or strabismu s 45"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 45%. Word-internal spacing is a PDF
      extraction artifact.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Examination typically reveals a subdued child with strabismus, slow horizontal nystagmus, hypotonia, and weak or absent tendon reflexes"
    explanation: >-
      Independent documentation of strabismus and nystagmus in the original
      probands.
  notes: >-
    Frequency band FREQUENT derived from the composite 45% Table 1 row for
    "horizontal nystagmus and/or strabismus"; the strabismus-specific rate is
    therefore at or below 45%. Founder-cohort derived.
- name: Horizontal Nystagmus
  category: Eye
  description: >-
    Slow horizontal nystagmus is described as a typical examination finding, and
    is pooled with strabismus in the cohort frequency table.
  phenotype_term:
    preferred_term: Horizontal nystagmus
    term:
      id: HP:0000666
      label: Horizontal nystagmus
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Examination typically reveals a subdued child with strabismus, slow horizontal nystagmus, hypotonia, and weak or absent tendon reflexes"
    explanation: >-
      Describes horizontal nystagmus as a typical finding on examination.
  notes: >-
    No independent band; the only published denominator (45%) pools nystagmus
    with strabismus and is carried on the Strabismus entry to avoid asserting the
    same denominator twice for two different features.
- name: Conductive Hearing Impairment
  category: Ear
  description: >-
    About a fifth of individuals failed newborn hearing screening with a
    conductive loss. Chronic otitis media is also reported, and yearly audiology
    assessment is recommended.
  phenotype_term:
    preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Failed newborn hearing screen (conductiv e loss) 21"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 21%. Word-internal spacing is a PDF
      extraction artifact.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Auditory features include chronic otitis media and hearing loss, with 20% failing newborn hearing screening"
    explanation: >-
      Prose corroboration (20%, versus 21% in the table) and identification of
      chronic otitis media as a contributing factor.
  notes: >-
    Frequency band OCCASIONAL derived from the 21% Table 1 figure (20% in the
    prose) in the founder cohort. Founder-cohort derived.
- name: Ventriculomegaly
  category: Nervous System
  description: >-
    Ventriculomegaly is among the most consistently reported neuroimaging
    findings, alongside white matter abnormality, thin corpus callosum,
    hypomyelination and an irregular cortical ribbon. All 18 individuals with
    available neuroimaging had abnormalities.
  phenotype_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuro- imaging was available for 18 individuals, all confirmed to have abnormalities, including hydrocephalus, ventriculomegaly, white matter abnormalities, thin corpus callosum, hypo- myelination, irregular cortical ribbon, Chiari malformation, absence of the septum pelluci- dum, hypoplastic optic nerves and septo-optic dysplasia"
    explanation: >-
      18/18 imaged individuals had abnormalities; ventriculomegaly is named among
      them.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Magnetic resonance imaging reveals ventriculomegaly, thin corpus callosum, white matter abnormalities, and an undulating or ‘‘lumpy’’ skull surface"
    explanation: >-
      Independent MRI description in the original probands.
  notes: >-
    No band for ventriculomegaly specifically. The Table 1 row "abnormal brain
    MRI (ventriculomegaly, white matter defects) 50%" pools imaging findings
    across the whole cohort of 35, whereas the prose reports 18/18 abnormal among
    those actually imaged. Those two denominators are not interchangeable, and no
    ventriculomegaly-specific numerator is published, so no band is asserted.
- name: Abnormal Cerebral White Matter Morphology
  category: Nervous System
  description: >-
    White matter abnormality and hypomyelination are consistently reported on
    MRI, together with thin corpus callosum.
  phenotype_term:
    preferred_term: Abnormal cerebral white matter morphology
    term:
      id: HP:0002500
      label: Abnormal cerebral white matter morphology
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Magnetic resonance imaging reveals ventriculomegaly, thin corpus callosum, white matter abnormalities, and an undulating or ‘‘lumpy’’ skull surface"
    explanation: >-
      Documents white matter abnormality and thin corpus callosum on MRI.
  notes: >-
    No band, for the same denominator reason given on the Ventriculomegaly
    entry.
- name: Hypoplasia of the Corpus Callosum
  category: Nervous System
  description: >-
    A thin corpus callosum is reported in both published series.
  phenotype_term:
    preferred_term: Hypoplasia of the corpus callosum
    term:
      id: HP:0002079
      label: Hypoplasia of the corpus callosum
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "white matter abnormalities, thin corpus callosum, hypo- myelination, irregular cortical ribbon"
    explanation: >-
      Names thin corpus callosum among the imaging findings.
  notes: >-
    No band; no callosum-specific numerator is published.
- name: Septo-Optic Dysplasia
  category: Nervous System
  description: >-
    Septo-optic dysplasia, absence of the septum pellucidum and hypoplastic optic
    nerves are at the severe end of the reported midline brain malformation
    spectrum.
  phenotype_term:
    preferred_term: Septo-optic dysplasia
    term:
      id: HP:0100842
      label: Septo-optic dysplasia
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Chiari malformation, absence of the septum pelluci- dum, hypoplastic optic nerves and septo-optic dysplasia"
    explanation: >-
      Names septo-optic dysplasia and the associated midline anomalies among the
      imaging findings.
  notes: >-
    No band; no numerator is published for this finding.
- name: Autism
  category: Nervous System
  description: >-
    Behavioural problems affect three quarters of individuals and comprise
    irritability, autistic features and attention deficit. Behavioural diagnoses
    include autism spectrum disorder and attention deficit disorder, and
    behavioural therapy including Applied Behaviour Analysis is reported to be
    beneficial in older affected children with autism.
  phenotype_term:
    preferred_term: Autism
    term:
      id: HP:0000717
      label: Autism
  frequency: FREQUENT
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Behavioural problem s (irritability , autistic features, ADHD) 75"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 75% for the composite behavioural
      category. Word-internal spacing is a PDF extraction artifact.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Behavioural diagnoses include autism spectrum disorder and attention deficit disorder"
    explanation: >-
      Names the formal behavioural diagnoses made in the cohort.
  notes: >-
    Frequency band FREQUENT derived from the composite 75% behavioural-problems
    row, which pools irritability, autistic features and ADHD. The
    autism-specific rate is therefore at or below 75%; the band is carried here
    because autism is the named formal diagnosis. Founder-cohort derived.
- name: Attention Deficit Hyperactivity Disorder
  category: Nervous System
  description: >-
    Attention deficit disorder is among the formal behavioural diagnoses made in
    the cohort, within the 75% composite behavioural-problem category.
  phenotype_term:
    preferred_term: Attention deficit hyperactivity disorder
    term:
      id: HP:0007018
      label: Attention deficit hyperactivity disorder
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Behavioural diagnoses include autism spectrum disorder and attention deficit disorder"
    explanation: >-
      Names attention deficit disorder as a behavioural diagnosis in the cohort.
  notes: >-
    No independent band; the 75% denominator is composite and is carried on the
    Autism entry rather than asserted twice.
- name: Sleep Disturbance
  category: Nervous System
  description: >-
    Irritability and sleep/wake dysregulation are seen in infancy and early
    childhood, and many children experience sleep dysregulation later. Melatonin
    has been used successfully in some children.
  phenotype_term:
    preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Irritability and sleep/wake dysregula- tion are seen in infancy and early childhood"
    explanation: >-
      Documents sleep/wake dysregulation as an early feature.
  notes: >-
    No band; described qualitatively without a denominator. Clinically important
    because sleep deprivation is itself a documented seizure trigger in this
    disorder.
- name: Developmental Regression
  category: Nervous System
  description: >-
    Severe developmental regression following status epilepticus is reported,
    with permanent hemiparesis in two individuals. This is an acquired,
    seizure-driven loss rather than an intrinsically neurodegenerative course.
  phenotype_term:
    preferred_term: Developmental regression
    term:
      id: HP:0002376
      label: Developmental regression
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Some individuals suf- fered severe developmental regression following status epilepticus, with two reported to have subsequent permanent hemiparesis"
    explanation: >-
      Documents regression and its proximate cause.
  notes: >-
    No band; "some individuals" is given without a denominator.
- name: Spastic Tetraplegia
  category: Nervous System
  description: >-
    Individuals identified in late childhood or adolescence are often diagnosed
    with a mixed-tone spastic quadriplegic cerebral palsy, attributed to hypoxic
    injury after long-term untreated or unrecognised seizures rather than to a
    primary pyramidal lesion.
  phenotype_term:
    preferred_term: Spastic tetraplegia
    term:
      id: HP:0002510
      label: Spastic tetraplegia
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals identified in late childhood/adolescence are often diagnosed with a mixed tone spastic quadriplegic cerebral palsy, likely reflecting hypoxic injury after long-term untreated/unrecognise d seizures"
    explanation: >-
      Documents the late-ascertainment spastic quadriplegic picture and
      attributes it to seizure-related hypoxic injury. The
      "unrecognise d" spelling is a PDF extraction artifact.
  notes: >-
    No band; "often" is given without a denominator.
- name: Tapered Finger
  category: Limbs
  description: >-
    Short hands with tapered fingers affect just over half of individuals. Broad
    thumbs, brachydactyly and a single palmar crease are also reported.
  phenotype_term:
    preferred_term: Tapered finger
    term:
      id: HP:0001182
      label: Tapered finger
  frequency: FREQUENT
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Short hands with tapered fingers 54"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 54%.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "broad jaw with protuberant angles, short hands, short tapered fingers, and broad thumbs"
    explanation: >-
      Independent description of the distal limb findings in the original
      probands.
  notes: >-
    Frequency band FREQUENT derived from the composite 54% Table 1 row for "short
    hands with tapered fingers". Founder-cohort derived.
- name: Broad Thumb
  category: Limbs
  description: >-
    Broad thumbs are reported in both series as part of the distal limb
    phenotype.
  phenotype_term:
    preferred_term: Broad thumb
    term:
      id: HP:0011304
      label: Broad thumb
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other dysmorphic features include brachydactyly, broad thumbs, single palmar crease, congenital talipes equinovarus, pes planus, toenail hypoplasia and pectus excavatum"
    explanation: >-
      Names broad thumbs among the additional dysmorphic features.
  notes: >-
    No band; not a numbered Table 1 row.
- name: Brachydactyly
  category: Limbs
  description: >-
    Brachydactyly is one of the additional dysmorphic features, and is
    mechanistically interesting because brachydactyly syndromes are themselves
    TGF-beta pathway disorders.
  phenotype_term:
    preferred_term: Brachydactyly
    term:
      id: HP:0001156
      label: Brachydactyly
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other dysmorphic features include brachydactyly, broad thumbs, single palmar crease, congenital talipes equinovarus, pes planus, toenail hypoplasia and pectus excavatum"
    explanation: >-
      Names brachydactyly among the additional dysmorphic features.
  notes: >-
    No band; not a numbered Table 1 row.
- name: Talipes Equinovarus
  category: Limbs
  description: >-
    Congenital talipes equinovarus affects around one in eight individuals.
  phenotype_term:
    preferred_term: Talipes equinovarus
    term:
      id: HP:0001762
      label: Talipes equinovarus
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Congenital talipes equinovarus 13"
    explanation: >-
      Table 1, n = 35 evaluated individuals, 13%.
  notes: >-
    Frequency band OCCASIONAL derived from 13% in the founder cohort.
    Founder-cohort derived.
- name: Scoliosis
  category: Musculoskeletal
  description: >-
    Spinal abnormalities, comprising sacral dimple, tethered cord and scoliosis in
    older children, affect about a fifth of individuals.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Spinal abnormalities were seen in 23% including sacral dimple, tethered cord and scoliosis in older children"
    explanation: >-
      Composite spinal abnormality frequency of 23% in the prose (21% in Table
      1), with scoliosis named as an age-dependent component.
  notes: >-
    Frequency band OCCASIONAL derived from the composite spinal-abnormality
    figure (23% in prose, 21% in Table 1) in the founder cohort. Scoliosis is one
    of three pooled findings, so its individual rate is lower. Founder-cohort
    derived.
- name: Tethered Cord
  category: Musculoskeletal
  description: >-
    Tethered cord is one of the pooled spinal abnormalities and is clinically
    important because it is surgically treatable.
  phenotype_term:
    preferred_term: Tethered cord
    term:
      id: HP:0002144
      label: Tethered cord
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Spinal abnormalities were seen in 23% including sacral dimple, tethered cord and scoliosis in older children"
    explanation: >-
      Names tethered cord among the spinal abnormalities.
  notes: >-
    No independent band; the 23% denominator is composite and is carried on the
    Scoliosis entry rather than asserted three times.
- name: Pectus Excavatum
  category: Musculoskeletal
  description: >-
    Pectus excavatum is reported among the additional dysmorphic features, and
    hypoplastic ribs were noted in a single individual.
  phenotype_term:
    preferred_term: Pectus excavatum
    term:
      id: HP:0000767
      label: Pectus excavatum
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features include pectus excavatum and hypoplastic ribs in a single individual"
    explanation: >-
      Names pectus excavatum among the thoracic findings.
  notes: >-
    No band; reported qualitatively.
- name: Hypoplastic Toenails
  category: Integument
  description: >-
    Toenail hypoplasia is one of the additional dysmorphic features.
  phenotype_term:
    preferred_term: Hypoplastic toenails
    term:
      id: HP:0001800
      label: Hypoplastic toenails
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "congenital talipes equinovarus, pes planus, toenail hypoplasia and pectus excavatum"
    explanation: >-
      Names toenail hypoplasia among the additional dysmorphic features.
  notes: >-
    No band; not a numbered Table 1 row.
progression:
- phase: Neonatal presentation
  age_range: Birth to the first weeks of life
  notes: >-
    Presentation is with hypotonia and poor feeding rather than with a
    recognisable dysmorphic gestalt; 54% are small for gestational age. Upper
    airway malacia may cause a weak cry, stridor and apnoea from the neonatal
    period. The craniofacial features are described as evolving over time, so
    the syndrome is less recognisable at birth than later.
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected neonates are hypotonic and feed poorly. Dysmorphic features that evolve over time include a bulbous nose, wide mouth and tongue, broad jaw with protuberant angles, short hands, short tapered fingers, and broad thumbs"
    explanation: >-
      Establishes the neonatal presentation and the explicitly evolving nature of
      the dysmorphic gestalt.
- phase: Infancy and early childhood
  age_range: First months of life through early childhood
  notes: >-
    Seizure onset falls in this window: multifocal spike-wave discharges
    typically begin by 6 months of age, and seizures may present as apnoea or
    breath-holding spells. Irritability and sleep/wake dysregulation appear.
    This is the window the published management guidance targets, with early
    EEG, anticonvulsant optimisation, and elective gastrostomy.
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "temporal regions typically begin by 6 months of age and are accompanied by focal or generalized seizures that can manifest as dystonic posturing, drop attacks, myoclonic jerks, or generalized tonic-clonic events. Multiple intractable seizure types can afflict an individual patient"
    explanation: >-
      Dates seizure onset to the first six months of life and lists the seizure
      semiology seen from that point. The quotation begins mid-sentence because
      a figure caption is interleaved at that point in the extracted PDF text.
- phase: Mid-childhood motor gains
  age_range: 3 to 10 years
  notes: >-
    Most affected individuals achieve independent ambulation between 3 and 10
    years, and some communicate with signs, gestures and sounds, while remaining
    non-verbal. Motor outcome is therefore meaningfully better than the
    cognitive outcome. Individuals ascertained late in this window are often
    labelled with mixed-tone spastic quadriplegic cerebral palsy attributed to
    hypoxic injury from unrecognised seizures.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Most affected individuals achieved independent ambu- lation (age range 3–10 years), and some communicate with signs, gestures and sounds"
    explanation: >-
      Documents the timing and extent of motor milestone attainment.
- phase: Mortality
  age_range: 1 week to 11 years for reported deaths; survivors to 30 years
  notes: >-
    Mortality is substantial but the disorder is not uniformly lethal. Of 51
    identified individuals, 12 (24%) were deceased at the time of the 2021
    report, with age at death between one week and 11 years, while the 39
    survivors ranged up to 30 years of age. Reported causes of death were
    infection, sudden cardiopulmonary arrest, and accidental drowning. The
    drowning deaths are worth stating plainly: in a population where every
    affected individual has epilepsy and most are non-verbal, water supervision
    is a concrete family-level preventive measure, although the source does not
    frame it as a formal recommendation and none is asserted here. SUDEP is not
    invoked by the authors and is not asserted. No survival curve, life
    expectancy estimate or actuarial mortality rate has been published, and the
    24% figure is a crude cross-sectional proportion in a founder cohort, not a
    survival statistic. Adult natural history beyond 30 years is undescribed.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seventy-six per- cent (n = 39) are currently living (age range 6 months to 30 years), while 24% (n = 12) are deceased (age of death between 1 week and 11 years"
    explanation: >-
      Gives the mortality proportion and the age-at-death range with an explicit
      denominator of 51 identified individuals.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Six children died between ages 9 months and 11 years as a consequence of infection, sudden cardiopulmonary arrest, or accidental drowning"
    explanation: >-
      Gives the causes of death for the subset of deceased individuals within the
      35-person clinically evaluated group.
genetic:
- name: SNIP1
  gene_term:
    preferred_term: SNIP1
    term:
      id: hgnc:30587
      label: SNIP1
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  association: >-
    Biallelic SNIP1 variants are the sole established cause of this disorder.
    MONDO:0013787 carries a single RO:0004003 (has material basis in germline
    mutation in) relation, to HGNC:30587 (SNIP1), which was re-verified against
    the MONDO release used for this curation.
  notes: >-
    SNIP1 (1p34.3) encodes a 396-amino-acid nuclear protein with an N-terminal
    nuclear localisation signal that binds Smad4 and CBP/p300, and a C-terminal
    forkhead-associated (FHA) domain. Every molecularly confirmed case reported
    to date is homozygous for the single Old Order Amish founder allele
    NM_024700.4:c.1097A>G, p.(Glu366Gly) in exon 4. No compound heterozygote and
    no second biallelic SNIP1 disease allele has been published, so allelic
    heterogeneity for this disorder is currently unknown rather than absent.

    Variant classification is not fully concordant across sources and is
    recorded rather than resolved here: the 2021 cohort authors assessed
    p.(Glu366Gly) as "pathogenic" under ACMG/AMP criteria, which is the quoted
    evidence below. A separate discrepancy concerns the FHA-domain boundary:
    PMID:34570759 places Glu366 "in close proximity to" the FHA domain and
    within the C-terminal 30 amino acids, whereas PMID:41904131 treats E366G as
    an FHA-domain mutation. Both framings are cited in the pathophysiology
    section; the substantive point they agree on is that the residue governs
    FHA-dependent phosphopeptide binding.

    Named-entity caution. SNIP1 is easily confused in text search with SNAP25,
    SNRPN and the SNX gene family, none of which is related to this disorder.
    The token "SNIP" additionally collides with the B-SNIP psychosis consortium
    literature, which is unrelated.
    Separately, the large majority of the SNIP1 literature concerns TGF-beta/Smad
    signalling, NF-kappaB, c-MYC and cancer biology in cell lines with no bearing
    on the human neurodevelopmental disorder. Every citation in this entry was
    checked to confirm either that it reports the human SNIP1 disorder, or that
    it is cited explicitly as background molecular biology of the SNIP1 protein
    and is labelled as such in its explanation.
  evidence:
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "present evidence to strongly support the pathogenicity of variants identified in TUBGCP6, BRAT1, SNIP1, CRADD, and HARS"
    explanation: >-
      Original gene-disease assertion, from autozygosity mapping plus exome
      sequencing in the Old Order Amish.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Together these data confirm this SNIP1 gene variant as a cause of an autosomal recessive complex neurodevelopmental disorder"
    explanation: >-
      Definitive confirmation of the gene-disease relationship in a
      35-individual cohort.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The SNIP1 variant was assessed according to ACMG variant classifi- cation criteria as ‘pathogenic"
    explanation: >-
      Formal ACMG classification of the founder allele as pathogenic.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "While no other biallelic variants in SNIP1 have conclusively been associated with genetic disease to date"
    explanation: >-
      Establishes that the founder allele is, as of that report, the only
      confirmed biallelic SNIP1 disease allele. Marked PARTIAL because this is a
      statement of absence of evidence at a point in time rather than a positive
      finding.
  variants:
  - name: NM_024700.4:c.1097A>G p.(Glu366Gly) Old Order Amish founder allele
    description: >-
      The single founder allele underlying every molecularly confirmed case
      reported to date. It is a missense substitution in exon 4 of SNIP1
      (Chr1:g.37537842T>C, hg38) replacing a conserved glutamate at residue 366
      near the C-terminal forkhead-associated domain, and it was assessed as
      pathogenic under ACMG/AMP criteria by the cohort authors. Disease occurs
      in the homozygous state; no compound heterozygote has been published.
    gene:
      preferred_term: SNIP1
      term:
        id: hgnc:30587
        label: SNIP1
    type: missense_variant
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:34570759
      reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "identified a homozygous NM_024700.4: c.1097A>G, p.(Glu366Gly) variant in SNIP1 as the likely cause of the condition"
      explanation: >-
        Names the founder allele at nucleotide and protein level and identifies
        the amino-acid substitution, establishing the missense class.
    - reference: PMID:34570759
      reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The SNIP1 variant was assessed according to ACMG variant classifi- cation criteria as ‘pathogenic"
      explanation: >-
        Formal ACMG classification supporting clinical_significance PATHOGENIC.
        The "classifi- cation" spelling is a PDF extraction artifact.
diagnosis:
- name: Molecular genetic testing for biallelic SNIP1 variants
  description: >-
    The diagnosis is molecular. In the Amish, targeted testing for the single
    founder allele NM_024700.4:c.1097A>G, p.(Glu366Gly) is sufficient and is how
    the original cohort was confirmed. Outside that population, the disorder
    would be reached by exome or genome sequencing, or by a
    developmental-and-epileptic-encephalopathy panel that contains SNIP1. The
    gene was originally localised by genome-wide autozygosity mapping to a
    1.65 Mb interval on chromosome 1p34.3 containing 17 genes, then resolved by
    whole exome sequencing.
  diagnosis_term:
    preferred_term: Genetic Testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Subsequent targeted genetic investigation of additional affected individuals that were identified, confirmed homozygosity of the SNIP1 variant in 35 individuals"
    explanation: >-
      Targeted founder-allele testing as the confirmatory assay in this
      population.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Inspection of resultant genotypes identified a single region of homozy- gosity greater than 1Mb common to all four affected individuals, a small (1.65Mb) genomic region on chromosome 1p34.3"
    explanation: >-
      Documents the autozygosity-mapping route that first localised the gene, the
      standard approach in founder populations.
  markers: Homozygous SNIP1 NM_024700.4:c.1097A>G, p.(Glu366Gly)
  notes: >-
    No diagnostic yield figure is asserted because no SNIP1-specific yield study
    exists. No biochemical or metabolic marker of this disorder has been
    described.
- name: Electroencephalography
  description: >-
    EEG is abnormal in all individuals assessed, showing diffuse background
    slowing and frequent focal or multifocal discharges with no characteristic
    pattern, so EEG supports rather than establishes the diagnosis. Its principal
    role here is early detection: guidance is that an EEG should be obtained at
    an early stage in infants with suspected apnoeic episodes, because apnoea and
    breath-holding spells can be the first seizure manifestation and subclinical
    seizures occur.
  diagnosis_term:
    preferred_term: Electroencephalography
    term:
      id: NCIT:C38054
      label: Electroencephalography
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We advise that an EEG should be obtained at an early stage in infants with SNIP1-related disorder and suspected apneic episodes"
    explanation: >-
      The published recommendation for early EEG and its specific indication.
  - reference: PMID:22279524
    reference_title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "temporal regions typically begin by 6 months of age and are accompanied by focal or generalized seizures that can manifest as dystonic posturing, drop attacks, myoclonic jerks, or generalized tonic-clonic events. Multiple intractable seizure types can afflict an individual patient"
    explanation: >-
      Dates the electrographic and clinical seizure onset and describes the
      seizure types EEG is used to characterise. The quotation begins
      mid-sentence because a figure caption is interleaved at that point in the
      extracted PDF text.
  notes: >-
    No sensitivity or specificity is asserted; the source explicitly states there
    is no characteristic EEG pattern for this disorder.
- name: Neuroimaging at diagnosis
  description: >-
    Brain imaging is recommended at diagnosis. It is a high-yield investigation
    in this disorder: neuroimaging was available for 18 individuals in the
    founder cohort and all 18 were confirmed to have abnormalities, spanning
    hydrocephalus, ventriculomegaly, white matter abnormality, thin corpus
    callosum, hypomyelination, irregular cortical ribbon, Chiari malformation,
    absence of the septum pellucidum, hypoplastic optic nerves and septo-optic
    dysplasia. The findings are not pathognomonic, so imaging characterises the
    structural burden and directs management rather than establishing the
    diagnosis, which rests on molecular confirmation.
  diagnosis_term:
    preferred_term: Neuroimaging
    term:
      id: NCIT:C173635
      label: Neuroimaging
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroimaging should be performed at diagnosis, and echocardiogram should be undertaken to screen for congenital heart defects"
    explanation: >-
      The published recommendation that neuroimaging be performed at diagnosis.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuro- imaging was available for 18 individuals, all confirmed to have abnormalities"
    explanation: >-
      The diagnostic yield, with an explicit denominator: 18 of 18 imaged
      individuals had abnormalities. The "Neuro- imaging" spelling is a PDF
      extraction artifact of a hyphenated line break.
  notes: >-
    Founder-cohort derived. The 18/18 yield is the proportion abnormal among
    those imaged within the Old Order Amish p.Glu366Gly kindred, not a
    sensitivity estimate for the disorder in general, and 18 is a subset of the
    35 comprehensively evaluated individuals rather than the whole cohort. The
    source names neuroimaging generically and does not specify a modality, so
    the generic NCIT Neuroimaging term is used rather than an MRI-specific one,
    even though MRI is the modality actually reported in both published series.
    No follow-up interval is specified, so no surveillance schedule is asserted.
- name: Echocardiography at diagnosis
  description: >-
    Because congenital heart defects affect 60% of individuals and include
    lesions requiring intervention, echocardiography is recommended at diagnosis
    to screen for congenital heart defects.
  diagnosis_term:
    preferred_term: Echocardiography Test
    term:
      id: NCIT:C16525
      label: Echocardiography Test
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroimaging should be performed at diagnosis, and echocardiogram should be undertaken to screen for congenital heart defects"
    explanation: >-
      The published screening recommendation, covering both neuroimaging and
      echocardiography at diagnosis.
  notes: >-
    Recorded as a diagnostic/screening investigation rather than a treatment.
    Follow-up interval is not specified in the source beyond the
    at-diagnosis study, so no surveillance schedule is asserted.
treatments:
- name: Anticonvulsant Therapy
  description: >-
    Antiseizure medication is the mainstay of neurological management, but the
    published experience is explicit that no antiepileptic medication was
    identified that consistently provides effective seizure control, and several
    individuals have multiple drug resistant epilepsy. The published advice is
    therefore about the goals of therapy rather than a specific agent: children
    should be under specialist neurology care for careful optimisation of
    anticonvulsant medication, to treat apnoea in infancy, maintain seizure
    control, and prevent status epilepticus and consequent developmental
    regression. No specific drug, drug class or drug to avoid is named in the
    source, and none is asserted here.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Anticonvulsant Therapy
    term:
      id: NCIT:C64172
      label: Anticonvulsant Therapy
  target_phenotypes:
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  - preferred_term: Status epilepticus
    term:
      id: HP:0002133
      label: Status epilepticus
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "careful optimisation of anticonvulsant medications to treat apnea in infancy, maintain seizure control, and prevent status epilepticus and consequent"
    explanation: >-
      The published management goal for anticonvulsant therapy in this disorder.
      The quotation ends mid-sentence at the page break in the cached text; the
      sentence continues "developmental regression".
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "There were no antiepileptic medications identified that consistently provide effective seizure control (defined as manageable frequency of sei- zures) and several individuals display multiple drug resistant epilepsy"
    explanation: >-
      The efficacy caveat. Marked PARTIAL because it documents the limits of the
      intervention rather than supporting its effectiveness, and it is the reason
      no specific agent is recommended in this entry.
  notes: >-
    No agents-to-avoid warning is recorded because there is no GeneReviews
    chapter for this disorder and the primary literature names none. Seizure
    triggers that are avoidable are documented on the Seizure phenotype: febrile
    illness, sleep deprivation and hypoglycaemic episodes.
- name: Elective Gastrostomy
  description: >-
    Elective gastrostomy tube placement is recommended to support growth and
    limit pulmonary aspiration. This is one of two interventions the authors
    single out as simple measures that can reduce hospitalisations, alleviate
    suffering and prolong life, which is an unusually strong claim for a
    supportive measure and reflects the universality of feeding failure and the
    46% rate of pulmonary aspiration.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Gastrostomy
    term:
      id: NCIT:C52006
      label: Gastrostomy
  target_phenotypes:
  - preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  - preferred_term: Aspiration
    term:
      id: HP:0002835
      label: Aspiration
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We recommend elective gastrostomy tube placement to support growth and limit pulmo- nary aspiration"
    explanation: >-
      The explicit recommendation for elective rather than reactive gastrostomy.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These simple interventions can reduce hospitalizations, alleviate suffering, and prolong life"
    explanation: >-
      The claimed benefit of the combined gastrostomy and seizure-optimisation
      strategy.
  notes: >-
    The "prolong life" claim is the authors' clinical judgement from a
    longitudinal founder-population cohort, not a controlled comparison. No
    trial evidence exists for any intervention in this disorder.
- name: Early Multidisciplinary Developmental Therapy
  description: >-
    Speech and language therapy, physical therapy and occupational therapy should
    all be commenced at an early stage to maximise neurocognitive outcome. An
    assessment of special educational needs should be carried out so an
    individualised educational plan can be put in place at school.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  - preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Supportive therapies (occupational, speech, and physical therapy) should be commenced at an early stage to maximise neurocognitive outcome for patients with SNIP1-related disorder"
    explanation: >-
      The published recommendation for early multidisciplinary therapy.
  notes: >-
    No effect size is asserted; this is expert recommendation, not measured
    outcome.
- name: Applied Behaviour Analysis for Autism Spectrum Disorder
  description: >-
    Behavioural therapy including Applied Behaviour Analysis is reported to be
    beneficial in older affected children who have autism spectrum disorder.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Autism
    term:
      id: HP:0000717
      label: Autism
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Behavioural therapy (including Applied Behaviour Analysis) is benefi- cial in older affected children who have autism spectrum disorder"
    explanation: >-
      The published behavioural-management recommendation, restricted to older
      children with autism spectrum disorder.
  notes: >-
    Reported benefit is clinical observation from the cohort, not a controlled
    trial result.
- name: Melatonin for Sleep Dysregulation
  description: >-
    Many children experience sleep dysregulation, and melatonin has been used
    successfully in some children. Sleep deprivation is separately documented as
    a seizure trigger in this disorder, so treating sleep dysregulation has a
    plausible secondary benefit for seizure burden, although that link has not
    been tested.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: melatonin
      term:
        id: CHEBI:16796
        label: melatonin
  target_phenotypes:
  - preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Many children experience sleep dysregulat ion. Melatonin has been used successfu lly in some children"
    explanation: >-
      Table 3 clinical guidance row for sleep. Word-internal spacing is a PDF
      extraction artifact.
  notes: >-
    "Used successfully in some children" is uncontrolled clinical experience. No
    dose, formulation or response rate is published for this disorder.
- name: Endocrine Monitoring for Hypoglycaemia and Hypothyroidism
  description: >-
    Infants and children should be monitored for hypoglycaemia and
    hypothyroidism, explicitly because these are easily treatable. This is a
    high-yield recommendation: hypothyroidism affects 25% and hypoglycaemia 21%
    of individuals, and hypoglycaemic episodes are also a documented seizure
    trigger.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Hypothyroidism
    term:
      id: HP:0000821
      label: Hypothyroidism
  - preferred_term: Hypoglycemia
    term:
      id: HP:0001943
      label: Hypoglycemia
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals should also be monitored for hypoglycemia and hypothyroidism as these are easily treatable"
    explanation: >-
      The published surveillance recommendation and its rationale.
  notes: >-
    Monitoring interval is not specified in the source, so none is asserted.
- name: Annual Ophthalmology and Audiology Surveillance
  description: >-
    Yearly ophthalmology and audiology assessments are recommended, reflecting
    the 45% rate of nystagmus and/or strabismus, the reported myopia, and the
    21% rate of failed newborn hearing screening with conductive loss and chronic
    otitis media.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  - preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Yearly ophthalmology and audiology assessments are recommended"
    explanation: >-
      The published surveillance interval for sensory assessment, one of the few
      places the source gives an explicit frequency.
differential_diagnoses:
- name: Heterozygous 1p34.3p34.2 contiguous gene deletion including SNIP1
  description: >-
    A de novo 2.3 Mb interstitial deletion at 1p34.3p34.2 encompassing 43 genes,
    including SNIP1, was reported in a 17-year-old female with global
    developmental delay, mild intellectual disability and multiple congenital
    anomalies. The authors concluded that SNIP1 haploinsufficiency was the most
    likely cause. This is the single most important named-entity distinction for
    this entry, because a naive search for "SNIP1 neurodevelopmental disorder"
    returns it alongside the recessive disorder.
  distinguishing_features:
  - Dosage - heterozygous whole-gene deletion versus biallelic missense hypomorphism. These are different genetic mechanisms and should not be pooled.
  - Severity - the deletion case had mild intellectual disability and no epilepsy reported, whereas the biallelic disorder has severe non-verbal developmental delay and universal intractable epilepsy.
  - Attribution - the deletion removes 43 genes and the authors could neither confirm SNIP1 as the driver nor exclude contributions from the other genes, so it does not establish a heterozygous SNIP1 phenotype.
  - Inheritance and counselling - de novo heterozygous CNV versus autosomal recessive with 25% sibling recurrence risk. Amish parents of an affected child are obligate heterozygotes and are unaffected, which is itself evidence against a clinically significant heterozygous phenotype in this population.
  evidence:
  - reference: PMID:29726122
    reference_title: "Interstitial microdeletion of the 1p34.3p34.2 region."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Haploinsufficiency of the 1p34.3p34.2 region, including the SNIP1 gene and excluding the five genes listed above, is responsible for the neurocognitive delays and other symptoms as identified in our patient"
    explanation: >-
      The deletion report's own conclusion, which is an attribution to a region
      rather than to SNIP1 alone.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The authors concluded that haploinsufficienc y of SNIP1 was the most likely cause of the female’s neurodevelopmental phenotype, although they were not able to confirm this nor rule out contributions of the other genes involved"
    explanation: >-
      Independent assessment that the deletion case does not establish a
      SNIP1-specific heterozygous phenotype. The
      "haploinsufficienc y" spelling is a PDF extraction artifact.
  notes: >-
    Not curated as a subtype of this entry. MONDO:0013787 is anchored to the
    autosomal recessive OMIM entity 614501; the heterozygous CNV is a separate
    contiguous-gene deletion syndrome. disease_term is also left unbound: MONDO
    has no term for a 1p34.3p34.2 contiguous deletion, and the nearest concepts
    are generic chromosomal-deletion groupings carrying no locus, which would
    assert less than this prose already does.
- name: Craniofacial spliceosomopathies
  notes: >-
    disease_term left unbound deliberately: this is a mechanism-defined CATEGORY
    (SF3B4/Nager, EFTUD2/mandibulofacial dysostosis-microcephaly, TXNL4A/Burn-McKeown
    and others), not a single entity. MONDO has no spliceosomopathy grouping term -
    a search for "spliceosomopathy" returns nothing - and binding one member such as
    MONDO:0007943 Nager acrofacial dysostosis would narrow the differential to one
    gene and misstate it.
  description: >-
    Disruption of spliceosome components causes several neurodevelopmental
    disorders with craniofacial defects, specifically Guion-Almeida type
    mandibulofacial dysostosis (EFTUD2), Nager syndrome (SF3B4) and
    cerebrocostomandibular syndrome (SNRPB). These overlap with SNIP1-related
    disorder in midface hypoplasia, cleft palate, developmental delay,
    intellectual disability, congenital cardiac defects and scoliosis, and the
    overlap is mechanistically real rather than coincidental given SNIP1's
    spliceosomal role.
  distinguishing_features:
  - Causal gene differs (EFTUD2, SF3B4, SNRPB versus SNIP1); the diagnosis is molecular.
  - Inheritance - the classical craniofacial spliceosomopathies listed are dominant, usually de novo, whereas SNIP1-related disorder is autosomal recessive.
  - Epilepsy burden - universal intractable epilepsy from infancy is characteristic of the SNIP1 disorder and is not a defining feature of the mandibulofacial dysostoses.
  - Calvarial phenotype - the irregular "lumpy" skull surface with variable calvarial thickness and a cortical ribbon that follows the skull contour is distinctive to the SNIP1 disorder.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Disrup- tion of spliceosome components have been associated with several neurodevelopmental disor- ders involving craniofacial defects, for example Guion-Almeida type mandibulofacial dysostosis, Nager syndrome, and cerebrocostomandibular syndrome, which also display sev- eral overlapping features with SNIP1-related disorder including midface hypoplasia, cleft pal- ate, developmental delay, intellectual disability, congenital cardiac defects and scoliosis"
    explanation: >-
      The clinical report's own placement of this disorder within the
      craniofacial spliceosomopathy differential.
- name: TGF-beta pathway connective tissue and aortopathy syndromes
  notes: >-
    disease_term left unbound deliberately: a pathway-defined CATEGORY spanning
    Marfan, the Loeys-Dietz series and vascular Ehlers-Danlos. It exists in this
    entry to warn that most SNIP1 literature is TGF-beta/Smad signalling with no
    bearing on the neurodevelopmental disorder, so the differential is about a
    literature hazard rather than one confusable disease. Binding any single
    member, e.g. MONDO:0012212 Loeys-Dietz syndrome 1, would misrepresent that.
  description: >-
    Loeys-Dietz syndrome and related TGF-beta pathway disorders share congenital
    cardiac defects including bicuspid aortic valve, septal defects, patent
    ductus arteriosus, mitral regurgitation and aortic root dilatation, together
    with craniosynostosis, cleft palate, hypertelorism, micrognathia, talipes and
    scoliosis. The overlap with SNIP1-related disorder is substantial and is
    predicted by SNIP1's role as a TGF-beta/Smad co-regulator.
  distinguishing_features:
  - Causal gene differs (TGFBR1, TGFBR2, SMAD3, TGFB2, TGFB3 versus SNIP1).
  - Cognition - Loeys-Dietz syndrome does not feature severe global developmental delay, intellectual disability or intractable epilepsy, which dominate the SNIP1 phenotype.
  - Aortic risk - progressive aortic aneurysm and dissection drive management in Loeys-Dietz syndrome; aortic root dilatation is reported in the SNIP1 disorder but no aneurysm or dissection risk has been established, and none is asserted here.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This includes systemic aortopathies, including for example Loeys-Dietz syndrome"
    explanation: >-
      Names Loeys-Dietz syndrome as the TGF-beta pathway disorder with which this
      condition shares cardiovascular and craniofacial features.
- name: CNTNAP2-related Pitt-Hopkins-like syndrome
  disease_term:
    preferred_term: CNTNAP2-related cortical dysplasia-focal epilepsy syndrome
    term:
      id: MONDO:0012400
      label: cortical dysplasia-focal epilepsy syndrome
  description: >-
    CNTNAP2 was among the most upregulated transcripts in affected individuals,
    and biallelic CNTNAP2 disruption causes an autosomal recessive
    Pitt-Hopkins-like syndrome (cortical dysplasia focal epilepsy syndrome)
    characterised by neurodevelopmental delay, hypotonia, hyporeflexia, seizures
    of multiple types, neuronal migration abnormality, autistic features and
    attention deficits. That is close to a phenocopy of the neurological arm of
    SNIP1-related disorder, which is presumably why CNTNAP2 dysregulation is a
    candidate mediator rather than a coincidence.
  distinguishing_features:
  - Causal gene differs (CNTNAP2 versus SNIP1).
  - CNTNAP2 disease lacks the characteristic calvarial dysplasia, craniofacial gestalt and 60% congenital heart disease burden of the SNIP1 disorder.
  - In the SNIP1 disorder CNTNAP2 is dysregulated downstream, not mutated; this is a mechanistic relationship, not an alternative diagnosis in a molecularly confirmed case.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Disruption of CNTNAP2 is associated with autosomal recessive Pitt-Hopkins-like syndrome (also known as cortical dysplasia focal epilepsy syndrome; MIM 610042) characterized by neurodevelopmental delay, hypotonia, hyporeflexia, seizures of multiple types, neuronal migration abnormalities, autistic features, and attention deficits"
    explanation: >-
      Documents the phenotypic near-identity of the neurological arm and
      identifies CNTNAP2 as a downstream dysregulated gene in the SNIP1
      disorder.
mechanistic_hypotheses:
- hypothesis_group_id: snip1_prc2_rescue
  hypothesis_label: PRC2 hyperactivity as a druggable node downstream of SNIP1 loss
  status: EMERGING
  description: >-
    In the mouse neural-progenitor-specific Snip1 knockout, depleting PRC2 is
    sufficient to reduce apoptosis and brain dysplasia and to partially restore
    the transcriptional programme. If the same epistasis holds for a hypomorphic
    allele, PRC2/EZH2 inhibition would be a mechanistically motivated
    intervention point. The hypothesis is recorded because the rescue experiment
    is unusually clean epistasis, not because it is close to clinical use.
  evidence:
  - reference: PMID:37553330
    reference_title: "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "Depletion of PRC2 is sufficient to reduce apoptosis and brain dysplasia and to partially restore genetic programs in the SNIP1-depleted brain in vivo"
    explanation: >-
      The rescue result the hypothesis rests on. Marked PARTIAL because it is a
      genetic depletion in a mouse conditional null during embryogenesis, not a
      pharmacological intervention in the human hypomorphic disorder.
  notes: >-
    Deliberately NOT curated as a treatment. Three gaps stand between this
    result and a therapy: the background is a null rather than the human
    hypomorph, the rescue window is embryonic and therefore not clinically
    reachable, and PRC2 depletion was genetic rather than pharmacological. No
    human, patient-derived, or translational evidence exists.
discussions:
- discussion_id: snip1_null_vs_hypomorph_model_mismatch
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    Do conclusions drawn from Snip1-null mouse and zebrafish models transfer to
    a human hypomorphic allele that is compatible with survival to adulthood?
  attaches_to:
  - pathophysiology#Neural Progenitor Cell Apoptosis and Reduced Neurogenesis
  - pathophysiology#Aberrant PRC2 Genomic Occupancy and H3K27me3 Turnover
  - pathophysiology#Biallelic SNIP1 p.Glu366Gly Founder Substitution
  rationale: >-
    Every in vivo model of SNIP1 loss published to date is a null or conditional
    null. Snip1 null mice are embryonic lethal; zebrafish RES-component mutants
    including snip1 fail in early embryogenesis. Humans homozygous for
    p.(Glu366Gly) survive, in the reported cohort to at least 30 years. That
    contrast is exactly the reason the human allele is inferred to be
    hypomorphic, but it also means the models are directionally informative and
    quantitatively wrong: the cellular lesion they demonstrate (neural progenitor
    apoptosis, reduced neurogenesis) is almost certainly the right lesion, while
    its magnitude, timing and tissue distribution in a patient are not
    established by them. Three further limits: the Nestin-Cre deletion is
    neural-restricted and therefore cannot model the craniofacial, calvarial,
    cardiac, airway or endocrine components that make this a recognisable
    multisystem syndrome; embryonic lethality precludes modelling epilepsy, the
    single most disabling human feature; and the PRC2-depletion rescue was
    performed in a null background during embryogenesis. Resolving the mismatch
    needs a p.(Glu366Gly) knock-in animal, or patient-derived iPSC cortical
    organoids, neither of which has been published.
  proposed_experiments:
  - experiment_id: exp_snip1_e366g_knockin_mouse
    name: Snip1 p.Glu366Gly knock-in mouse with multisystem phenotyping
    description: >-
      Generate a constitutive Snip1 p.Glu366Gly knock-in mouse on a defined
      background and phenotype it for the features that null models cannot
      reach: postnatal survival, video-EEG for spontaneous seizures, craniofacial
      and calvarial micro-CT for suture patency and calvarial surface
      irregularity, echocardiography for septal and outflow lesions, and
      developmental milestone testing. Compare homozygotes, heterozygotes and
      wild-type littermates.
    decision_criterion: >-
      Whether homozygous knock-in animals survive to weaning and reproduce any of
      the epilepsy, calvarial or cardiac features of the human disorder.
    would_support:
    - >-
      Survival with seizures and craniofacial or cardiac malformation would
      confirm p.(Glu366Gly) as a hypomorph sufficient to cause the multisystem
      syndrome, and would give the field its first tractable disease model.
    would_refute:
    - >-
      Embryonic or perinatal lethality indistinguishable from the null, or a
      completely normal homozygote, would both indicate that mouse Snip1 dosage
      biology does not map onto the human allele.
  - experiment_id: exp_snip1_patient_ipsc_cortical_organoid
    name: Patient iPSC-derived cortical organoids with isogenic correction
    description: >-
      Derive iPSCs from individuals homozygous for p.(Glu366Gly), correct the
      variant to create isogenic controls, and differentiate both to forebrain
      cortical organoids. Assay progenitor pool size, cleaved caspase-9 and
      caspase-3, neuronal output, genome-wide H3K27me3 distribution, and
      detained-intron splicing efficiency by RNA-seq.
    decision_criterion: >-
      Whether the human hypomorphic allele reproduces, in human neural tissue,
      the progenitor apoptosis and splicing defects so far shown only in
      null-background mouse and zebrafish.
    would_support:
    - >-
      Increased progenitor apoptosis with caspase-9 activation and measurable
      detained-intron retention in patient organoids would establish that the
      mouse and zebrafish mechanisms operate in human cells at the disease
      allele dosage.
    would_refute:
    - >-
      Normal progenitor survival and normal splicing in patient organoids would
      indicate that the null-model mechanism is not the operative one at
      hypomorphic dosage, and would redirect attention to the transcriptional
      co-regulation arm or to non-neural tissues.
  - experiment_id: exp_snip1_ezh2_inhibition_hypomorph
    name: Pharmacological EZH2 inhibition in a hypomorphic SNIP1 background
    description: >-
      Test whether small-molecule EZH2 inhibition, rather than genetic PRC2
      depletion, rescues progenitor apoptosis in a p.(Glu366Gly) hypomorphic
      background (knock-in mouse neural progenitors or patient organoids), with
      a dose-response and a defined treatment window.
    decision_criterion: >-
      Whether the PRC2-depletion rescue reported in the null background survives
      the three translations it currently has not made: genetic to
      pharmacological, null to hypomorph, and embryonic to postnatal.
    would_support:
    - >-
      Dose-dependent reduction of apoptosis with preserved neurogenesis would
      convert the PRC2 finding from a mechanistic observation into a genuine
      therapeutic lead worth curating as a treatment.
    would_refute:
    - >-
      No rescue, or rescue only at doses that impair normal neurogenesis, would
      confirm that the PRC2 result should remain a mechanistic hypothesis and
      not be presented as a therapeutic direction.
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "SNIP1 null mouse models display embryonic lethality indicating that this Amish variant may be unlikely to result in complete loss of func- tion"
    explanation: >-
      States the mismatch directly: the null model is lethal, so it cannot be
      the right dosage model for a viable human allele.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seventy-six per- cent (n = 39) are currently living (age range 6 months to 30 years), while 24% (n = 12) are deceased (age of death between 1 week and 11 years"
    explanation: >-
      Quantifies the human side of the mismatch: survival to 30 years, against
      embryonic lethality in the null models the mechanism rests on.
  - reference: PMID:37553330
    reference_title: "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "The SNIP1-depleted brain exhibits dysplasia with robust induction of caspase 9-dependent apoptosis"
    explanation: >-
      The mechanism whose transferability is in question. Marked PARTIAL because
      it is obtained by depletion, not by the human hypomorphic allele.
- discussion_id: snip1_founder_generalisability
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Do the phenotype frequencies curated here generalise beyond the Old Order
    Amish founder kindred, and does biallelic SNIP1 disease exist outside it?
  attaches_to:
  - pathophysiology#Biallelic SNIP1 p.Glu366Gly Founder Substitution
  - phenotypes#Seizure
  rationale: >-
    Every frequency band in this entry derives from a single published cohort of
    35 clinically evaluated Old Order Amish individuals, all homozygous for one
    founder allele, drawn from 21 interrelated families and linkable into a
    single pedigree. Three consequences follow and are flagged on each banded
    phenotype's notes field. First, these are genotype-specific frequencies for
    p.(Glu366Gly) homozygosity, not disease-level frequencies: a different
    biallelic SNIP1 genotype could present differently, and the source itself
    records substantial phenotypic variation between individuals including within
    sibships. Second, the shared genetic and environmental background of a
    founder community means unmeasured modifiers are shared, which can both
    inflate apparent consistency and mask features that a heterogeneous cohort
    would reveal. Third, ascertainment was clinic-based within two Plain-community
    practices, so mildly affected individuals may be systematically absent. No
    non-Amish case with biallelic SNIP1 variants has been published, so whether
    the entity looks the same elsewhere is simply unknown. Resolving this
    requires GeneMatcher-style ascertainment of biallelic SNIP1 cases outside the
    founder population.
  proposed_experiments:
  evidence:
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "While no other biallelic variants in SNIP1 have conclusively been associated with genetic disease to date"
    explanation: >-
      States the absence of any non-founder biallelic SNIP1 disease allele, which
      is the fact that makes generalisability unknowable from current data.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Substantial phenotypic variation was observed between affected individ- uals, including within sibships"
    explanation: >-
      Variability on an essentially uniform genetic and community background is
      the second reason the cohort proportions should not be read as fixed
      disease frequencies.
- discussion_id: snip1_which_arm_drives_disease
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Is the human phenotype driven predominantly by the spliceosomal (RES
    recruitment) arm of SNIP1 function or by the transcriptional co-regulation
    (CBP/p300, TGF-beta, NF-kappaB, c-MYC) arm?
  attaches_to:
  - pathophysiology#Impaired SNIP1 FHA-Domain Phosphopeptide Recognition
  - pathophysiology#Disrupted SNIP1 Co-Regulation of CBP/p300-Dependent Transcription
  rationale: >-
    The entry deliberately curates both arms as parallel branches from the same
    upstream dosage lesion because the evidence does not yet adjudicate between
    them. The splicing arm now has the more direct evidence: the E366G variant is
    shown by name to impair FHA-domain binding to phosphorylated SF3B1 and thereby
    RES recruitment (PMID:41904131), which is the only published experiment on
    the actual disease allele in its actual molecular context. The transcriptional
    arm has stronger patient-derived correlative support: TGF-beta receptor
    signalling in epithelial-to-mesenchymal transition was the most
    overrepresented dysregulated Reactome pathway in patient blood
    (PMID:34570759). But the patient transcriptome study is limited by a sample
    size of six, by blood as a surrogate for brain, and by an FDR at the pathway
    level of 0.43, and the authors state the tissue limitation explicitly.
    Critically, the two arms are not independent: reduced SNIP1 protein abundance
    (PMID:22279524) degrades both simultaneously, so a clean dissociation would
    require a separation-of-function allele that has not been reported.
  proposed_experiments:
  evidence:
  - reference: PMID:41904131
    reference_title: "Phosphorylation of SF3B1 by CDK11 orchestrates spliceosome activation via SNIP1-dependent RES complex recruitment."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Mutations in SNIP1 FHA domain, including the neurodevelopmental disorder-associated E366G variant, impair P-SF3B1 binding, pre-mRNA splicing, and cell viability"
    explanation: >-
      The splicing arm's claim on primacy: the only published experiment
      performed on the actual disease allele.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "These studies were inherently limited due to the modest number of samples available for study and through the obvious limitations of comparing gene transcriptions profiles in blood, with tis- sues in which clinical outcomes are primarily manifested (brain"
    explanation: >-
      The transcriptional arm's counterweight is patient-derived but the authors
      state its two limitations themselves, which is precisely why the question
      remains open. Marked PARTIAL because it qualifies rather than supports.
- discussion_id: snip1_neurodegeneration_question
  kind: OPEN_QUESTION
  status: OPEN
  prompt: >-
    Does SNIP1-related disorder include a genuine progressive neurodegenerative
    component, or is all apparent progression seizure-related secondary injury?
  attaches_to:
  - pathophysiology#Detained-Intron Splicing Brake Dysregulation in Neurons
  - pathophysiology#Status Epilepticus
  - pathophysiology#Hypoxic-Ischaemic Secondary Brain Injury
  rationale: >-
    Conditional Snip1 deletion in mouse cerebellum decreases detained-intron
    splicing efficiency and causes frank neurodegeneration (PMID:37027487),
    raising the possibility that the human hypomorph also drives slow neuronal
    loss. Against that, the human clinical description attributes regression and
    the late spastic quadriplegic picture to hypoxic injury from long-term
    untreated or unrecognised seizures rather than to intrinsic degeneration, and
    survivors reach 30 years of age. No longitudinal imaging or neuropathology in
    genotyped individuals has been published, so the two explanations are not yet
    separable. This distinction is not academic: it determines whether aggressive
    early seizure control should be expected to preserve trajectory (secondary
    injury model) or merely to slow it (degenerative model).
  proposed_experiments:
  evidence:
  - reference: PMID:37027487
    reference_title: "A molecular brake that modulates spliceosome pausing at detained introns contributes to neurodegeneration."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "Snip1 conditional knockout in the cerebellum decreases DI splicing efficiency and causes neurodegeneration"
    explanation: >-
      The case for a degenerative component. Marked PARTIAL because it is a
      conditional null in mouse cerebellum and has no demonstrated human
      correlate.
  - reference: PMID:34570759
    reference_title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals identified in late childhood/adolescence are often diagnosed with a mixed tone spastic quadriplegic cerebral palsy, likely reflecting hypoxic injury after long-term untreated/unrecognise d seizures"
    explanation: >-
      The competing explanation: the clinical authors attribute apparent
      progression to acquired seizure-related hypoxic injury rather than to
      intrinsic degeneration. Marked PARTIAL because it is the authors'
      attribution rather than a measurement distinguishing the two models.
references:
- reference: PMID:10887155
  title: "A novel smad nuclear interacting protein, SNIP1, suppresses p300-dependent TGF-beta signal transduction."
- reference: PMID:11567019
  title: "SNIP1 inhibits NF-kappa B signaling by competing for its binding to the C/H1 domain of CBP/p300 transcriptional co-activators."
- reference: PMID:17157259
  title: "SNIP1 is a candidate modifier of the transcriptional activity of c-Myc on E box-dependent target genes."
- reference: PMID:22279524
  title: "Genetic mapping and exome sequencing identify variants associated with five novel diseases."
- reference: PMID:27912208
  title: "Smad Nuclear Interacting Protein 1 Acts as a Protective Regulator of Pressure Overload-Induced Pathological Cardiac Hypertrophy."
- reference: PMID:29360106
  title: "Structure of the human activated spliceosome in three conformational states."
- reference: PMID:29726122
  title: "Interstitial microdeletion of the 1p34.3p34.2 region."
- reference: PMID:29969449
  title: "RES complex is associated with intron definition and required for zebrafish early embryogenesis."
- reference: PMID:34570759
  title: "A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder."
- reference: PMID:37027487
  title: "A molecular brake that modulates spliceosome pausing at detained introns contributes to neurodegeneration."
- reference: PMID:37553330
  title: "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development."
- reference: PMID:38304835
  title: "The clinical utilization of SNIP1 and its pathophysiological mechanisms in disease."
- reference: PMID:41904131
  title: "Phosphorylation of SF3B1 by CDK11 orchestrates spliceosome activation via SNIP1-dependent RES complex recruitment."
notes: >-
  GeneReviews baseline. No disease-specific GeneReviews chapter exists. PubMed
  searches for "SNIP1 GeneReviews[All Fields]" and for the disease name with
  "GeneReviews[All Fields]" both returned zero results on 2026-08-01. The
  deep-research run did surface one GeneReviews item that mentions SNIP1: the
  resources appendix "Genetic Disorders Associated with Founder Variants Common
  in the Amish Population" (NBK558237), which lists the gene and quotes a 1/34
  Old Order Amish carrier frequency. That appendix is deliberately NOT cited
  here. It is a "Resources for Genetics Professionals" appendix rather than a
  disease chapter, it carries no PMID and is not PubMed-indexed, so it cannot be
  fetched into references_cache and its figures cannot be verbatim-verified.
  Its carrier-frequency figure is therefore not asserted, though it is
  reassuringly consistent with the 1.48% allele frequency independently quoted
  from PMID:22279524 (which implies roughly a 1-in-34 heterozygote rate).

  The authoritative clinical baseline used instead is PMID:34570759 (Ammous et
  al. 2021, PLoS Genetics): a 35-individual prospectively evaluated cohort with a
  phenotype frequency table and a published management guideline table, i.e. it
  fills the role a GeneReviews chapter would. Its Table 3 management guidance is
  curated in the treatments and diagnosis sections. Neither that paper nor
  PMID:22279524 names any agent or circumstance to avoid, so no drug-safety
  warning is recorded.


  Deep research provenance. One provider was run: claude_code, via
  "just research-disorder claude_code SNIP1-Related_Neurodevelopmental_Disorder"
  (report at research/SNIP1-Related_Neurodevelopmental_Disorder-deep-research-claude_code.md;
  13 web searches, 68 turns, 24 citations, 17 minutes). Every PMID it proposed
  was independently re-fetched and every snippet re-verified against the cache
  before use. The report contributed three things this entry would otherwise
  have missed: the PRC2/neural-progenitor-survival arm (PMID:37553330), the
  null-versus-hypomorph model mismatch now recorded as a discussion, and the
  GeneReviews Amish appendix assessed above. Several of its suggestions were
  rejected on verification: HP:0002263 and HP:0004279 were not adopted because
  the corresponding cohort rows were already covered by banded umbrella
  phenotypes; its "5/203 = 2.5%" reading of the PMID:22279524 carrier data does
  not match the cached Table 4 row, which reads 1.48% (6/406) under a
  "Population-specific Allele Frequency" heading, so the cached figure was used;
  and its PRC2-inhibition therapeutic suggestion is recorded as a
  mechanistic_hypotheses entry rather than as a treatment.


  Founder-cohort caveat, stated once here and repeated on every banded
  phenotype. Every phenotype frequency band in this entry derives from Table 1
  of PMID:34570759, n = 35 clinically evaluated Old Order Amish individuals, all
  homozygous for the same p.(Glu366Gly) founder allele and drawn from 21
  interrelated families. One band uses a different denominator and says so:
  Cloverleaf Skull uses 5/35, that being the count the source actually gives for
  the severe multi-suture form. Craniosynostosis of any degree is curated
  without a band, because the only quotable count belongs to the cloverleaf
  subgroup and reusing it there would understate the true proportion. The
  mortality figure (12/51 identified individuals, 24%) is deliberately
  NOT carried as a phenotype frequency band; it sits in the progression section,
  both because its denominator differs from the Table 1 rows and because
  HP:0003819 "Death in childhood" lives under Clinical modifier rather than
  Phenotypic abnormality and so is not a valid phenotype_term in this schema.
  All of these are founder-kindred proportions and
  must NOT be presented or reused as general disease frequencies. Where Table 1
  pools several features into one row (upper airway abnormalities 75%,
  behavioural problems 75%, horizontal nystagmus and/or strabismus 45%, spinal
  abnormalities 21%, hernias 21%, short hands with tapered fingers 54%), the band
  is asserted once on the most representative phenotype and the pooled nature is
  stated in that entry's notes; the co-pooled features are curated without a
  band rather than inheriting the composite figure.


  Snippet provenance. The cached record for PMID:34570759 and PMID:22279524 is
  extracted full text from the open-access PDF, not the PubMed abstract. PDF
  extraction inserts spurious intra-word spaces ("Hyporeflexi a",
  "developmen tal", "unrecognise d") and renders some symbols oddly
  ("A.G" for "A>G", "84.9 69.6% SD" for "84.9 +/- 9.6% SD"). Snippets are quoted
  byte-exact from the cache including these artifacts, because the verbatim
  checker compares against the cache; each affected evidence item says so in its
  explanation. No snippet was retyped or normalised.


  Named-entity confusion. SNIP1 (Smad nuclear interacting protein 1, HGNC:30587,
  1p34.3) is distinct from SNAP25, SNRPN and the SNX sorting nexin family, none
  of which is implicated in this disorder. The bare token "SNIP" additionally
  collides in free-text search with the B-SNIP psychosis consortium literature,
  which has nothing to do with this gene. The overwhelming majority of PubMed
  hits for SNIP1 itself are TGF-beta/Smad signalling or cancer-biology papers
  with no bearing on the human disease; the papers cited here for background
  protein biology (PMID:10887155, PMID:11567019, PMID:17157259, PMID:27912208,
  PMID:29360106, PMID:29969449, PMID:38304835) are used only as such, are
  labelled as such in their explanations, and are marked PARTIAL where the model
  system does not transfer to the human hypomorph. Each was individually checked
  to confirm it concerns SNIP1 (Smad nuclear interacting protein 1) and not a
  homonym, and that no cancer-cohort or cell-line statistic has leaked into a
  clinical claim. The disorder must also not be conflated with the heterozygous
  1p34.3p34.2 contiguous-gene deletion syndrome, which is curated as a
  differential diagnosis with its reasoning.


  Structured-source citations omitted. No ORPHA, CGGV or CGDS structured-source
  record was generated for this entry. Producing one would require bumping a
  data MANIFEST pin; those pins are currently stale and un-refreshable, which is
  tracked in #7622 and is out of scope for a curation PR. Orphanet epidemiology
  for this entity is therefore not cited and no worldwide prevalence figure is
  asserted.


  Per-edge evidence gap, stated explicitly. The pathograph has 25 nodes and 71
  causal edges (32 mechanism-to-mechanism, 39 mechanism-to-phenotype), and
  none of the edges carries its own evidence item; the supporting citations sit
  on the nodes at each end instead. This is the single largest compliance gap in
  the entry and it is deliberate rather than overlooked. Populating 71 edge-level
  evidence items would mean re-quoting node-level snippets under a claim they do
  not individually address: for the mechanism-to-phenotype edges in particular
  the available sources document co-occurrence of the mechanism and the
  phenotype, not the edge. Rather than manufacture 71 duplicate citations, the
  edges carry prose descriptions and the reader is pointed at the node evidence.
  Note the perverse incentive this creates in the compliance score: wiring 38 of
  the 53 phenotypes into the graph (72% causal in-link coverage, against 0% and
  22% in the two most recent comparable entries) lowers the headline compliance
  number precisely because it adds edges. The graph is better for it.


  Unwired phenotypes, stated explicitly. Fifteen phenotypes carry no causal
  in-link: ADHD, autism, conductive hearing impairment, gastroesophageal reflux,
  horizontal nystagmus, hypoglycaemia, hypothyroidism, intestinal malrotation,
  pectus excavatum, scoliosis, sleep disturbance, small for gestational age,
  strabismus, tethered cord and umbilical hernia. For each of these the cited
  sources record the association with the disorder but publish no mechanism
  linking it to any node in this pathograph, and inventing an edge to raise
  in-link coverage would assert causation the literature does not support. Small
  for gestational age is in this list by correction rather than by omission: it
  was previously wired downstream of neonatal feeding failure, an edge that ran
  backwards in time and has been removed.


  Deliberate omissions. (1) No treatment is curated for the congenital heart
  defects beyond screening echocardiography, because the source recommends
  screening but names no cardiac intervention. (2) Craniosynostosis surgery is
  not curated as a treatment: the source documents cloverleaf skull in five
  individuals but does not state that surgical release was performed or
  recommended. (3) No prevalence figure outside the Amish is asserted. (4) No
  animal_models section is curated: the mouse and zebrafish work cited is
  loss-of-function/null, not a knock-in of the human hypomorphic allele, and no
  p.(Glu366Gly) knock-in model has been published. (5) Genetic counselling
  (NCIT:C15240) is not curated as a treatment despite being clinically salient
  here, since autosomal recessive inheritance in an endogamous community with a
  1.48% founder allele frequency implies a 25% sibling recurrence risk. The
  reason is evidentiary, and was checked rather than assumed: all thirteen
  cached references for this entry were grepped case-insensitively for
  "counsel", and none of them contains the string, so there is no quotable
  snippet for the recommendation from any source this entry cites. Neither
  Table 3 of PMID:34570759 nor PMID:22279524 raises counselling, carrier
  testing or recurrence risk. Rather than assert an unsourced treatment, the
  gap is recorded here.


  Placement note on surveillance. Annual Ophthalmology and Audiology
  Surveillance, and Endocrine Monitoring for Hypothyroidism and Hypoglycaemia,
  are curated under treatments: with therapeutic_modality OTHER rather than
  under diagnosis:. They are screening activities in form, but in the source
  they are longitudinal management recommendations for an already-diagnosed
  individual, not investigations that contribute to reaching the diagnosis,
  which is the distinction diagnosis: is used for throughout this entry. The
  at-diagnosis investigations (molecular testing, EEG, neuroimaging,
  echocardiography) sit in diagnosis:.

📚

References & Deep Research

References

PMID:10887155

A novel smad nuclear interacting protein, SNIP1, suppresses p300-dependent TGF-beta signal transduction.

No top-level findings curated for this source.

PMID:11567019

SNIP1 inhibits NF-kappa B signaling by competing for its binding to the C/H1 domain of CBP/p300 transcriptional co-activators.

No top-level findings curated for this source.

PMID:17157259

SNIP1 is a candidate modifier of the transcriptional activity of c-Myc on E box-dependent target genes.

No top-level findings curated for this source.

PMID:22279524

Genetic mapping and exome sequencing identify variants associated with five novel diseases.

No top-level findings curated for this source.

PMID:27912208

Smad Nuclear Interacting Protein 1 Acts as a Protective Regulator of Pressure Overload-Induced Pathological Cardiac Hypertrophy.

No top-level findings curated for this source.

PMID:29360106

Structure of the human activated spliceosome in three conformational states.

No top-level findings curated for this source.

PMID:29726122

Interstitial microdeletion of the 1p34.3p34.2 region.

No top-level findings curated for this source.

PMID:29969449

RES complex is associated with intron definition and required for zebrafish early embryogenesis.

No top-level findings curated for this source.

PMID:34570759

A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder.

No top-level findings curated for this source.

PMID:37027487

A molecular brake that modulates spliceosome pausing at detained introns contributes to neurodegeneration.

No top-level findings curated for this source.

PMID:37553330

SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development.

No top-level findings curated for this source.

PMID:38304835

The clinical utilization of SNIP1 and its pathophysiological mechanisms in disease.

No top-level findings curated for this source.

PMID:41904131

Phosphorylation of SF3B1 by CDK11 orchestrates spliceosome activation via SNIP1-dependent RES complex recruitment.

No top-level findings curated for this source.

Deep Research

Claude Code ▸

1. Disease Information

claude-haiku-4-5-20251001, claude-opus-5[1m] 24 citations 2026-08-01T00:52:22.826091

1. Disease Information

Overview

SNIP1‑related neurodevelopmental disorder is an autosomal recessive, congenital‑onset, multisystem neurodevelopmental syndrome caused by biallelic variants in SNIP1 (Smad nuclear interacting protein 1) at 1p34.3. To date the disorder is known essentially exclusively from a single founder missense variant, NM_024700.4:c.1097A>G, p.(Glu366Gly), segregating in Old Order Amish communities in Pennsylvania, Ohio, Indiana and Wisconsin.

The cardinal presentation is neonatal hypotonia and poor feeding, followed by severe (typically non‑verbal) global developmental delay, universally penetrant and frequently drug‑resistant epilepsy, and a recognizable craniofacial gestalt with abnormal skull shape (including multi‑suture craniosynostosis in a subset). Congenital heart defects, upper‑airway abnormalities, and hypothyroidism are common comorbidities, and early childhood mortality is substantial.

[ABSTRACT] PMID:34570759 — "Here, we describe extensive genetic studies and clinical findings of a complex inherited neurodevelopmental disorder in 35 individuals associated with a SNIP1 NM_024700.4:c.1097A>G, p.(Glu366Gly) variant, present at high frequency in the Amish community. The cardinal clinical features of the condition include hypotonia, global developmental delay, intellectual disability, seizures, and a characteristic craniofacial appearance." (Ammous Z, Rawlins LE, Jones H, et al. PLoS Genet 2021;17(9):e1009803. doi:10.1371/journal.pgen.1009803)

Key identifiers

Resource	Identifier	Label / note
MONDO	`MONDO:0013787`	Psychomotor retardation, epilepsy, and craniofacial dysmorphism (recommended `disease_term`)
OMIM (phenotype)	`OMIM:614501`	NEURODEVELOPMENTAL DISORDER WITH HYPOTONIA, CRANIOFACIAL ABNORMALITIES, AND SEIZURES; NEDHCS (renamed from PMRED)
OMIM (gene)	`OMIM:608241`	SMAD NUCLEAR INTERACTING PROTEIN 1; SNIP1
MedGen	`C3281055` / concept 482685	Psychomotor retardation, epilepsy, and craniofacial dysmorphism
UMLS	`C3281055`	equivalent
HGNC	`hgnc:30587`	SNIP1 (note dismech lowercase‑prefix convention)
NCBI Gene	`79753`	SNIP1, human
Ensembl	`ENSG00000163877`
UniProt	`Q8TAD8`	Smad nuclear‑interacting protein 1
RefSeq	`NM_024700.4` / `NP_078976.2`	canonical transcript used for all HGVS
dbSNP	`rs387906986`	founder variant
ClinVar	Variation ID `30717`; RCV000023695
Orphanet	No ORDO entry found	OLS4 ORDO search for "SNIP1" returned 0 hits; MONDO:0013787 carries no Orphanet xref. Curation gap — flag as `NOT_YET_DOCUMENTED`.
ICD‑10 / ICD‑11	No dedicated code	Would be coded under a generic congenital‑malformation‑syndrome / epilepsy code; do not invent a specific code.
MeSH	No specific descriptor

Synonyms and alternative names

Psychomotor retardation, epilepsy, and craniofacial dysmorphism (PMRED) — original OMIM title, still the MONDO label
Neurodevelopmental disorder with hypotonia, craniofacial abnormalities, and seizures (NEDHCS) — current OMIM title
SNIP1‑related neurodevelopmental disorder
"Symptomatic epilepsy and skull dysplasia" — the clinical/laboratory name used by DDC Clinic Medical Center (Ohio Amish) for its targeted test
Amish SNIP1 syndrome / SNIP1 Amish founder disorder (informal)

Nature of the evidence base

Information is derived almost entirely from aggregated deep‑phenotyping of individual patients in a community‑genetics setting — the Clinic for Special Children (Strasburg, PA), DDC Clinic (Middlefield, OH), and collaborating centres — rather than from EHR/claims resources. There are effectively two primary clinical publications:

PMID:22279524 — Puffenberger EG, Jinks RN, Sougnez C, et al. "Genetic mapping and exome sequencing identify variants associated with five novel diseases." PLoS One 2012;7(1):e28936. doi:10.1371/journal.pone.0028936 — original gene discovery (3 patients / 2 sibships).
PMID:34570759 — Ammous Z, Rawlins LE, Jones H, et al. PLoS Genet 2021 — definitive natural‑history cohort (51 identified, 35 deeply phenotyped).

No population registry, EHR‑based cohort, or ICEES/COHD‑style comorbidity data exist for this disorder.

2. Etiology

Primary causal factor

Genetic, monogenic, autosomal recessive. Homozygosity for SNIP1 c.1097A>G, p.(Glu366Gly) is the sole established cause.

[ABSTRACT] PMID:22279524 — "Using between 1 and 5 patient samples per disorder, we identified sequence variants in the known disease-causing genes SLC6A3 and FLVCR1, and present evidence to strongly support the pathogenicity of variants identified in TUBGCP6, BRAT1, SNIP1, CRADD, and HARS."

[BODY] PMID:22279524 — the disease locus mapped to a region containing 34 homozygous variants shared among affected individuals, of which only one — the SNIP1 change — was novel. Glu366 is highly conserved and lies in the C‑terminus, the region through which SNIP1 engages c‑Myc.

Genetic risk factors

Causal variant: NM_024700.4:c.1097A>G (NC_000001.11:g.37537842T>C, GRCh38), p.(Glu366Gly), missense, exon 4, biallelic/homozygous. rs387906986.
Variant classification: ClinVar germline classification "Likely pathogenic", review status 1 star (criteria provided, single submitter), last evaluated 2022‑03‑22. The 2021 PLoS Genetics authors independently assessed it as "pathogenic" under ACMG/AMP criteria. (This discrepancy should be recorded verbatim in the entry rather than resolved silently.)
Founder effect / ancestry: essentially the only genetic "risk factor" is Old Order Amish ancestry, plus consanguinity/endogamy.
Modifier genes: none identified. No modifier or susceptibility loci have been reported.
Heterozygote status: carriers are unaffected; "no unaffected individuals being homozygous for this variant" [BODY, PMID:34570759] — i.e., complete penetrance in homozygotes within the studied cohort.

A second, distinct genetic mechanism (heterozygous deletion)

PMID:29726122 — Jacher JE, Innis JW. "Interstitial microdeletion of the 1p34.3p34.2 region." Mol Genet Genomic Med 2018;6(4):649–654. doi:10.1002/mgg3.409. A 2.3 Mb contiguous‑gene deletion including SNIP1 (but not AGO1, AGO3, GRIK3, SLC2A1, RIMS3) in a patient with global developmental delay, mild intellectual disability, delayed bone age, bilateral vesicoureteral reflux, vocal cord paralysis, right aberrant subclavian artery, kyphoscoliosis, bilateral metatarsus adductus, and valgus knee deformity. The authors attribute the phenotype to haploinsufficiency of the region "including the SNIP1 gene."

Curation guidance: this is a contiguous‑gene deletion syndrome, not the recessive SNIP1 disorder. Do not merge. It is at most a supporting datum that SNIP1 dosage matters, and the vocal‑cord paralysis is an intriguing partial echo of the airway phenotype. Consider a discussions entry with kind: KNOWLEDGE_GAP.

Environmental risk factors

None identified. No toxin, infectious, nutritional, occupational, parental‑age, or seasonal risk factor has been reported. Sex is not a risk factor (cohort was 19 M : 16 F).

Protective factors

None identified. No protective allele, dietary, or lifestyle factor is known. gnomAD contains no homozygotes for the variant, providing no evidence for a compensated/protected genotype.

Gene–environment interactions

Not documented for the human disorder. The nearest mechanistic analogue comes from cell biology: SNIP1's chromatin occupancy in neural progenitors is signal‑dependent — [ABSTRACT‑adjacent, BODY PMID:37553330] "TGFβ and NFκB signaling pathways control SNIP1 binding to specific gene loci in NPCs." This raises a testable (unproven) hypothesis that maternal/fetal inflammatory or TGF‑β‑modulating exposures could modify expressivity. Flag as hypothesis, not established.

3. Phenotypes

3.1 Frequency table (Ammous et al. 2021, n = 35–37 evaluated individuals)

Frequencies below are [BODY] data from the PLoS Genetics clinical tables, cross‑checked against the HPO disease annotations for OMIM:614501 (retrieved from ontology.jax.org, which encodes exact numerators/denominators).

Phenotype	Suggested HPO term	Frequency (cohort)	HPO annotation fraction	Suggested `FrequencyEnum`
Severe global developmental delay (non‑verbal)	`HP:0011344` Severe global developmental delay	100%	37/37	`OBLIGATE`/`VERY_FREQUENT`
Hypotonia	`HP:0001252` Hypotonia	100%	35/35	`VERY_FREQUENT`
Hyporeflexia	`HP:0001265` Hyporeflexia	100%	35/35	`VERY_FREQUENT`
Seizures	`HP:0001250` Seizure	100%	37/37	`VERY_FREQUENT`
Feeding difficulties	`HP:0011968` Feeding difficulties	100%	35/35 (onset early infancy)	`VERY_FREQUENT`
Abnormal skull shape (irregular surface, craniosynostosis)	`HP:0002whatever` → use `HP:0001363` Craniosynostosis + `HP:0002684` Thickened calvaria (verify)	100%	—	`VERY_FREQUENT`
High arched palate	`HP:0000218` High palate	100%	35/35	`VERY_FREQUENT`
Wide mouth	`HP:0000154` Wide mouth	100%	37/37	`VERY_FREQUENT`
Exaggerated cupid's bow upper lip	`HP:0002263` Exaggerated cupid's bow	100%	35/35	`VERY_FREQUENT`
Laryngomalacia	`HP:0001601` Laryngomalacia	74%	26/35	`FREQUENT`
Upper‑airway abnormality (laryngomalacia, apnoea, stridor)	`HP:0002104` Apnea; `HP:0010307` Stridor	75%	—	`FREQUENT`
Behavioural problems (irritability, autistic features, ADHD)	`HP:0000708` Behavioral abnormality; `HP:0000717` Autism; `HP:0007018` ADHD	75%	—	`FREQUENT`
Congenital heart defect (ASD, VSD, aortic coarctation)	`HP:0001631` ASD; `HP:0001629` VSD; `HP:0001680` Coarctation of aorta	60%	—	`FREQUENT`
Small for gestational age	`HP:0001518` Small for gestational age	54%	18/35	`FREQUENT`
Tapered fingers	`HP:0001182` Tapered finger	54%	20/37	`FREQUENT`
Short palm / short hands	`HP:0004279` Short palm	51%	18/35	`FREQUENT`
Abnormal brain MRI	see §3.3	50%	—	`FREQUENT`
Pulmonary aspiration	`HP:0002835` Aspiration	46%	—	`FREQUENT`
Horizontal nystagmus and/or strabismus	`HP:0000666` Horizontal nystagmus; `HP:0000486` Strabismus	45%	—	`FREQUENT`
Micrognathia	`HP:0000347` Micrognathia	29%	10/35	`OCCASIONAL`
Hypothyroidism	`HP:0000821` Hypothyroidism	25%	—	`OCCASIONAL`
Hypoglycaemia	`HP:0001943` Hypoglycemia	20–21%	7/35	`OCCASIONAL`
Failed newborn hearing screen (conductive)	`HP:0000405` Conductive hearing impairment	21%	—	`OCCASIONAL`
Umbilical hernia	`HP:0001537` Umbilical hernia	20%	7/35	`OCCASIONAL`
Talipes equinovarus	`HP:0001762` Talipes equinovarus	14%	5/35	`OCCASIONAL`
Cardiomyopathy (left ventricular non‑compaction)	`HP:0001638` Cardiomyopathy; `HP:0011664` Left ventricular noncompaction	12%	—	`OCCASIONAL`

Additional HPO terms annotated to OMIM:614501 without a cohort fraction (from the HPO disease annotation file — treat as frequency: omitted): HP:0000158 Macroglossia · HP:0000414 Bulbous nose · HP:0012802 Broad jaw · HP:0011304 Broad thumb (2/2) · HP:0002500 Abnormal cerebral white matter morphology · HP:0003429 CNS hypomyelination (2/2) · HP:0002079 Hypoplasia of the corpus callosum (2/2) · HP:0002119 Ventriculomegaly (2/2) · HP:0002353 EEG abnormality · HP:0001607 Subglottic stenosis · HP:0001647 Bicuspid aortic valve · HP:0001650 Aortic valve stenosis · HP:0000007 Autosomal recessive inheritance.

Frequency‑evidence caution (per docs/frequency-evidence-guidelines.md): the fractions above come from the HPO annotation file (which is itself derived from PMID:34570759 tables), not from an abstract sentence. Only the qualitative associations are abstract‑supported. Prefer omitting frequency: for any phenotype whose band you cannot back with a directly quotable abstract sentence.

3.2 Craniofacial gestalt (the "recognizable" feature)

[BODY] PMID:34570759 — features include "midface hypoplasia, a wide mouth with downturned corners and thin cupids bow upper lip, large tongue, high arched palate, microretrognathia (Pierre Robin sequence with or without cleft palate in three patients), malocclusion, small upturned bulbous nose, long palpebral fissures and proptosis."

Skull: "Abnormal skull shape (irregular surface, craniosynostosis)" in 100%, with "severe multi-suture craniosynostosis with Cloverleaf appearance of the skull in five individuals" [BODY].

Suggested HPO: HP:0000308 Microretrognathia · HP:0000202 Orofacial cleft / HP:0000175 Cleft palate · HP:0000463 Anteverted nares (verify) · HP:0000637 Long palpebral fissure · HP:0000520 Proptosis · HP:0000316 Hypertelorism (not reported — do not add) · HP:0011800 Midface retrusion · HP:0000687 Pierre‑Robin sequence → correct term is HP:0000201 Pierre‑Robin sequence (verify with OAK).

3.3 Neuroimaging phenotype

[BODY] PMID:34570759 — brain MRI abnormalities in ~50%, "including hydrocephalus, ventriculomegaly, white matter abnormalities, thin corpus callosum, hypomyelination, irregular cortical ribbon, Chiari malformation, absence of the septum pellucidum, hypoplastic optic nerves and septo-optic dysplasia."

Suggested HPO: HP:0000238 Hydrocephalus · HP:0002119 Ventriculomegaly · HP:0002500 Abnormal cerebral white matter morphology · HP:0002079 Hypoplasia of the corpus callosum · HP:0003429 CNS hypomyelination · HP:0002510 Chiari malformation (verify ID) · HP:0001331 Absent septum pellucidum · HP:0000633 Optic nerve hypoplasia (verify) · HP:0100842 Septo‑optic dysplasia (verify).

3.4 Epilepsy phenotype (the dominant morbidity)

[BODY] PMID:34570759 — "Seizures are a cardinal feature of the disorder with all affected individuals developing epilepsy"; types include "focal and generalised intractable seizures (myoclonic, absence, tonic-clonic) of infantile or childhood onset"; "There were no antiepileptic medications identified that consistently provide effective seizure control" and "several individuals display multiple drug resistant epilepsy."

Suggested HPO: HP:0001250 Seizure · HP:0011146 Dialeptic seizure / HP:0002121 Absence seizure · HP:0002123 Generalized myoclonic seizure · HP:0002069 Bilateral tonic‑clonic seizure · HP:0007359 Focal‑onset seizure · HP:0011171 Complex febrile seizure (not reported) · HP:0002133 Status epilepticus (management target) · HP:0011097 Epileptic spasms (not reported — do not add). Qualifiers: temporality: RECURRENT, onset: INFANTILE_ONSET/CHILDHOOD_ONSET, drug resistance is best captured in the description text.

3.5 Developmental attainment and function

[BODY] PMID:34570759 — "Global developmental delay (severe, non-verbal)" in 100%; "Most affected individuals achieved independent ambulation (age range 3–10 years), and some communicate with signs, gestures and sounds."

This is an important nuance: motor milestones are markedly delayed but often eventually achieved, while expressive language is essentially absent. Suggested HPO: HP:0011344 Severe global developmental delay · HP:0001510 Growth delay · HP:0002187 Profound global developmental delay (do not use — cohort described as "severe") · HP:0001344 Absent speech.

3.6 Quality‑of‑life impact

No formal QoL instrument (EQ‑5D, PROMIS, SF‑36, PedsQL) has been applied to this cohort. Impact must be inferred qualitatively:

Feeding/nutrition: universal feeding difficulty with 46% pulmonary aspiration drives gastrostomy dependence — a major daily‑care burden and a driver of the recommendation for elective (rather than reactive) G‑tube placement.
Epilepsy: drug‑resistant seizures with status‑epilepticus risk dominate family burden and healthcare utilisation.
Communication: non‑verbal status with partial sign/gesture communication.
Mobility: independent ambulation is attainable for most, materially better than many severe DEEs.
Behaviour: irritability/autistic features/ADHD in 75%.

Curation note: record this as notes:/description text, not as evidence‑backed QoL claims.

4. Genetic / Molecular Information

Causal gene

SNIP1 — Smad nuclear interacting protein 1; hgnc:30587; OMIM:608241; 1p34.3; Entrez 79753; ENSG00000163877; UniProt Q8TAD8 (396 aa, 45,778 Da). Previous/alias symbol: PML1 (yeast Pml1p homolog).

Protein architecture (UniProt Q8TAD8): - N‑terminal nuclear localisation signal; the N‑terminal region mediates Smad and RelA/p65 binding - Forkhead‑associated (FHA) domain, residues 281–344 — a phospho‑threonine‑peptide recognition module - C‑terminus (containing Glu366) mediates c‑Myc interaction - PTMs: phosphorylation (Ser35, Ser49, Ser52, Ser54, Thr57, Ser58, Ser202, Ser394); SUMOylation (Lys30, Lys108, Lys223) - Subcellular localisation: nucleus / nucleoplasm (GO:0005654)

Pathogenic variant

Field	Value
HGVS c.	`NM_024700.4:c.1097A>G`
HGVS p.	`NP_078976.2:p.(Glu366Gly)` (E366G)
Genomic (GRCh38)	`NC_000001.11:g.37537842T>C`
dbSNP	rs387906986
Variant type	Missense (single nucleotide variant), exon 4
Zygosity in patients	Homozygous (biallelic)
Origin	Germline, inherited (founder haplotype); no somatic involvement
ClinVar	Variation 30717; Likely pathogenic, 1★, last evaluated 2022‑03‑22
ACMG (publication)	assessed as pathogenic in PMID:34570759

Allele frequency

gnomAD: [BODY, PMID:34570759] "allele frequency of 0.001% with 11 heterozygotes (10 Amish) and no homozygous individuals listed."
Old Order Amish (Puffenberger 2012, control chromosomes): 5/203 = 2.5% carrier frequency [BODY]
Old Order Amish (Ammous 2021): allele frequency 0.5% (Pennsylvania) to 1.4% (Ohio/Indiana/Wisconsin) [BODY]
GeneReviews (Wallace SE, Puffenberger EG, Bean LJH; "Genetic Disorders Associated with Founder Variants Common in the Amish Population," last update 2023‑12‑07; NBK558237): carrier frequency 1/34 in Old Order Amish; this variant accounts for ~100% of pathogenic SNIP1 variants identified in this population.

Note the internal inconsistency across sources (2.5% vs 0.5–1.4% vs 1/34 ≈ 2.9%). These are different sampling frames (small control panel vs settlement‑stratified vs GeneReviews summary). Record each with its own prevalence/case_fractions record, population stratifier, and evidence — do not average them.

Functional consequences of p.Glu366Gly

Three independent lines of evidence, all pointing to partial (hypomorphic) loss of function, not a null:

Protein instability and mislocalisation (in vitro, 2012). [BODY, PMID:22279524] The mutant showed abnormal nuclear localisation with "a more aggregated appearance" versus wild‑type's punctate pattern; western blot band density was "84.9±9.6% SD lower than wild-type" — i.e. ~85% reduction in steady‑state protein.
Conservation and domain proximity. [BODY, PMID:34570759] "The p.(Glu366Gly) SNIP1 amino acid substitution is located in close proximity to the forkhead association (FHA) domain," a "functionally important region of SNIP1"; the authors caution "this Amish variant may be unlikely to result in complete loss of function." (Note the UniProt FHA boundary is 281–344, so E366 sits just C‑terminal to the annotated domain; the 2026 Nature Communications paper below treats E366G as an FHA‑domain mutation. Record the discrepancy rather than picking a side.)
Direct splicing‑machinery defect (2026, definitive). [ABSTRACT] PMID:41904131 — "Mutations in SNIP1 FHA domain, including the neurodevelopmental disorder-associated E366G variant, impair P-SF3B1 binding, pre-mRNA splicing, and cell viability." (Gajdušková P, Ruiz de Los Mozos I, Hluchý M, et al. "Phosphorylation of SF3B1 by CDK11 orchestrates spliceosome activation via SNIP1‑dependent RES complex recruitment." Nat Commun 2026. doi:10.1038/s41467-026-71119-2)

Mechanistic classification for the KB: LOSS_OF_FUNCTION (hypomorphic/partial). Complete LoF is presumably embryonic‑lethal — consistent with mouse homozygous null prenatal lethality (§15).

Modifier genes

None reported. The remarkable clinical homogeneity of the Amish cohort (single variant, shared genetic background) both explains the absence of modifier data and makes this disorder a poor discovery substrate for modifiers.

Epigenetic information

Two distinct senses, both relevant:

SNIP1 as an epigenetic regulator (mechanism, not biomarker). [ABSTRACT] PMID:37553330 — "SNIP1 facilitates the genomic occupancy of Polycomb complex PRC2 and instructs H3K27me3 turnover at target genes." SNIP1 also recruits TET2 to c‑MYC target genes (PMID:30404004, "SNIP1 Recruits TET2 to Regulate c-MYC Target Genes and Cellular DNA Damage Response," Cell Rep 2018) — a direct link to DNA 5‑hydroxymethylation.
Episignature / methylation biomarker for diagnosis: none published. SNIP1 is not among the genes with a validated DNA‑methylation episignature (EpiSign). Curation gap.

Chromosomal abnormalities

No aneuploidy, translocation, or inversion associated with the recessive disorder.
1p34.3p34.2 interstitial microdeletion encompassing SNIP1 (PMID:29726122) — see §2. Relevant to CMA interpretation.

5. Environmental Information

Environmental factors: none identified. No CTD entry links an environmental chemical to this disorder.
Lifestyle factors: not applicable — congenital monogenic disorder.
Infectious agents: not causal. However, infection is a leading proximate cause of death (see §11) and recurrent aspiration/respiratory infection is a major secondary morbidity — model this as a downstream consequence node, not an etiologic node.

6. Mechanism / Pathophysiology

6.1 SNIP1 protein: four functional arms

[ABSTRACT] PMID:34570759 — "SNIP1 (Smad nuclear interacting protein 1) is a widely expressed transcriptional suppressor of the TGF-β signal-transduction pathway which plays a key role in human spliceosome function."

[ABSTRACT] PMID:38304835 (Chen Y, Guo W, Guo X, Wanqing Q, Yin Z. "The clinical utilization of SNIP1 and its pathophysiological mechanisms in disease." Heliyon 2024;10(2):e24601) — "Smad intranuclear binding protein 1 (SNIP1), a highly conserved nuclear protein, functions as a transcriptional regulator and exerts a significant influence on disease progression. In addition, the N-terminal domain of SNIP1 facilitates its interaction with Smad4, a signaling protein associated with the TGF-β family, and RelA/p65, a transcription factor connected to NF-κB. This interaction further enhances the transcriptional activation of c-Myc-dependent genes."

Arm	Molecular action	Key references
(A) TGF‑β/BMP repression	Binds Smad1/2/4; suppresses p300‑dependent TGF‑β signal transduction	Kim RH et al. Genes Dev 2000 (PMID:10887155)
(B) NF‑κB repression	Competes with RELA/p65 for the C/H1 domain of CBP/p300	Kim RH et al. J Biol Chem 2001 (PMID:11567019)
(C) c‑Myc co‑activation / cell cycle	Modifies c‑Myc transcriptional activity on E‑box genes; regulates cyclin D1 transcription and mRNA stability; regulates ATR‑dependent DNA‑damage signalling; recruits TET2 to c‑MYC targets	Fujii M et al. Mol Cell 2006 (PMID:17157259); Roche KC et al. Oncogene 2004 (PMID:15378006); Bracken CP et al. Cancer Res 2008 (PMID:18794151); Roche KC et al. Oncogene 2007 (PMID:17260016); Chen L‑L et al. Cell Rep 2018 (PMID:30404004)
(D) Spliceosome / RES complex	FHA domain reads phospho‑SF3B1 and recruits the RES (retention‑and‑splicing) complex during spliceosome activation; with RNPS1 forms a "molecular brake" pausing the spliceosome at Bact on detained introns; also implicated in U12‑type minor‑spliceosome splicing and small‑RNA biogenesis	PMID:41904131; PMID:37027487; Fernandez JP et al. PLoS Genet 2018 (PMID:29969449); Liu C et al. PNAS 2008 (PMID:18632581)

6.2 The splicing arm — the most direct route from E366G to disease

[ABSTRACT] PMID:41904131 — "We further demonstrate that P-SF3B1 is recognized by forkhead-associated (FHA) domain of SNIP1, which promotes recruitment of retention and splicing (RES) complex during spliceosome activation. Acute SNIP1 depletion disrupts RES incorporation, causes widespread splicing defects, and promotes hyperphosphorylation of SF3B1 by CDK11."

[ABSTRACT] PMID:37027487 (Meng D, Zheng Q, Zhang X, Piao X, Luo L, Jia Y. "A molecular brake that modulates spliceosome pausing at detained introns contributes to neurodegeneration." Protein Cell 2023;14(1):27–53. doi:10.1093/procel/pwac008) — "Here, we suggest that post-transcriptional DI splicing is paused at the Bact state, an active spliceosome but not catalytically primed, which depends on Smad Nuclear Interacting Protein 1 (SNIP1) and RNPS1 (a serine-rich RNA binding protein) interaction… Snip1 conditional knockout in the cerebellum decreases DI splicing efficiency and causes neurodegeneration."

This places SNIP1 alongside other spliceosomopathy neurodevelopmental genes (EFTUD2, SF3B4, SNW1, SF3B1, RNU4‑2) — a useful cross‑entry link in dismech, and arguably a candidate future mechanism module ("spliceosomopathy neurodevelopment").

6.3 The neural‑progenitor survival arm

[ABSTRACT] PMID:37553330 (Matsui Y, Djekidel MN, Lindsay K, et al. "SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development." Nat Commun 2023;14:4771. doi:10.1038/s41467-023-40487-4) — "Here, we report that Smad nuclear interacting protein 1 (SNIP1) promotes neural progenitor cell survival and neurogenesis and is, therefore, integral to brain development. The SNIP1-depleted brain exhibits dysplasia with robust induction of caspase 9-dependent apoptosis. Mechanistically, SNIP1 regulates target genes that promote cell survival and neurogenesis, and its activities are influenced by TGFβ and NFκB signaling pathways. Further, SNIP1 facilitates the genomic occupancy of Polycomb complex PRC2 and instructs H3K27me3 turnover at target genes. Depletion of PRC2 is sufficient to reduce apoptosis and brain dysplasia and to partially restore genetic programs in the SNIP1-depleted brain in vivo."

Supporting [BODY] detail from the same paper: "By E15, Snip1_Nes-KO embryos displayed severe thinning of brain tissues and dysplasia with 100% penetrance"; SOX2⁺ neural progenitor cells, and TBR2⁺ and INSM1⁺ intermediate progenitors "were markedly reduced"; "All ventricles of Snip1_Nes-KO displayed strong induction of cl-caspase 3"; "inhibition of caspase 9 robustly reduced apoptosis" whereas caspase 8 inhibition "modestly altered apoptosis"; EED (PRC2) depletion "reduced apoptosis and rescued NPCs."

6.4 Patient transcriptome (human, in vivo)

[BODY] PMID:34570759 — differential expression analysis of patient samples identified "75 significantly upregulated genes, and 109 significantly downregulated genes" (FDR <0.05). Reactome analysis: "the most overrepresented pathway was the TGF-β receptor signalling in epithelial to mesenchyme pathway." Five seizure‑associated genes were notably altered: ROBO1, SOX5, CNTNAP2, PAFAH1B1, TSNARE1 (ROBO1 most upregulated); SYT1 (synaptic vesicle) also dysregulated; 24 differentially expressed genes had "a previously established association with neurological disease." Additional dysregulated pathways reported in the paper's discussion include NOTCH3 signalling and the MYC pathway.

6.5 Proposed causal chain (for `pathophysiology` nodes)

[MOLECULAR] SNIP1 p.Glu366Gly homozygosity
   → reduced SNIP1 protein abundance (~85% ↓) + nuclear aggregation
   → impaired FHA-domain recognition of phospho-SF3B1
├─→ [MOLECULAR] failed RES complex recruitment / spliceosome activation defect
│        → aberrant pre-mRNA splicing, detained-intron mishandling
└─→ [MOLECULAR] dysregulated SNIP1-dependent transcription
         (de-repressed TGF-β/SMAD; de-repressed NF-κB/RELA-p300;
          altered c-MYC target output; mislocalised PRC2 → aberrant H3K27me3)
   → [CELLULAR] neural progenitor cell (SOX2+, TBR2+, INSM1+) apoptosis
via the intrinsic, caspase-9-dependent pathway; reduced neurogenesis
   → [TISSUE] cortical dysplasia, hypomyelination, corpus callosum hypoplasia,
ventriculomegaly, midline defects; abnormal cranial suture fusion;
abnormal pharyngeal/laryngeal and cardiac morphogenesis
   → [ORGANISM] severe global developmental delay, intractable epilepsy,
craniofacial gestalt, airway compromise, CHD, early mortality

Upstream vs downstream: the molecular splicing/transcription lesion is upstream; NPC apoptosis is the pivotal cellular hub (the point at which PRC2 depletion rescues, in mouse); tissue malformation and epilepsy are downstream.

6.6 Suggested ontology terms

GO biological process (all verified against QuickGO): - GO:0000398 mRNA splicing, via spliceosome — modifier DECREASED/ABNORMAL - GO:0007179 transforming growth factor beta receptor signaling pathway — INCREASED (de‑repression) - GO:0043122 regulation of canonical NF-kappaB signal transduction — INCREASED - GO:0097193 intrinsic apoptotic signaling pathway — INCREASED - GO:0021895 cerebral cortex neuron differentiation — DECREASED - GO:0006974 DNA damage response - Additional candidates to verify with OAK: GO:0050768 negative regulation of neurogenesis; GO:0006355 regulation of DNA-templated transcription; GO:0035914? (n/a)

GO cellular component (verified): GO:0005681 spliceosomal complex · GO:0031519 PcG protein complex · GO:0005654 nucleoplasm (verify).

Cell Ontology (verified via OLS): - CL:0011020 neural progenitor cell - CL:0000681 radial glial cell - CL:0013000 forebrain radial glial cell - CL:0000047 neuronal stem cell (verify) - CL:0000540 neuron (verify)

CHEBI: not applicable — no small‑molecule metabolite is central to the mechanism.

6.7 Metabolic, immune, and biochemical dimensions

Metabolic changes: no primary inborn‑error‑of‑metabolism component. Hypoglycaemia in ~20% is documented but its mechanism is unexplained (feeding failure? endocrine?) — record as an unexplained finding / knowledge gap, not as a metabolic mechanism.
Immune system involvement: no immunodeficiency or autoimmunity. SNIP1 is an NF‑κB brake and has documented roles in intestinal epithelial barrier/inflammation (PMID:29426045, Mucosal Immunol 2018) and osteoarthritis inflammation (PMID:37739115), but no immune phenotype has been reported in patients. Do not over‑extrapolate.
Tissue damage mechanisms: developmental (apoptotic loss of progenitors + malformation), not degenerative — with the important caveat that the Protein Cell 2023 cerebellar cKO shows SNIP1 loss can also drive post‑developmental neurodegeneration, raising an untested question about whether adolescents/adults with the disorder have a degenerative component.
Biochemical abnormalities: hypothyroidism (25%) is the one reproducible laboratory abnormality; hypoglycaemia (~20%). No specific enzyme deficiency, receptor, or ion‑channel defect.

6.8 Molecular profiling summary

Modality	Status
Transcriptomics	✅ Patient RNA‑seq (PMID:34570759); mouse brain RNA‑seq + CUT&RUN (PMID:37553330); zebrafish RNA‑seq (PMID:29969449); human cell iCLIP‑seq (PMID:41904131)
Proteomics	✅ Quantitative proteomics of chromatin‑associated spliceosomes (PMID:41904131) — mechanism, not patient‑derived
Metabolomics / Lipidomics	❌ None
Epigenomics	Indirect only (H3K27me3 CUT&RUN in mouse; no patient methylome)
Single‑cell / spatial	❌ No patient scRNA‑seq or spatial data
Functional genomics screens	SNIP1 is broadly essential in DepMap‑type screens (consistent with mouse lethality); the 2026 paper shows acute depletion impairs cell viability

7. Anatomical Structures Affected

Organ level

Primary: - Brain UBERON:0000955 — cerebral cortex UBERON:0000956, cerebral white matter UBERON:0002437(verify), corpus callosum UBERON:0002336, lateral ventricle UBERON:0002285, septum pellucidum UBERON:0002094(verify), cerebellum UBERON:0002037 (mouse degeneration data), optic nerve UBERON:0000941 - Cranium / skull UBERON:0003128 — cranial suture UBERON:0006842(verify) - Face / craniofacial skeleton — mandible UBERON:0001684, palate UBERON:0001716, tongue UBERON:0001723, lip UBERON:0001833, nose UBERON:0000004

Secondary / systemic: - Heart UBERON:0000948 — interatrial septum, interventricular septum, aorta UBERON:0000947, aortic valve UBERON:0002137, left ventricular myocardium (non‑compaction) - Larynx UBERON:0001737 (laryngomalacia, subglottic stenosis) - Lung / respiratory system UBERON:0001004 (aspiration, pneumonia) - Thyroid gland UBERON:0002046 (hypothyroidism) - Ear / middle ear UBERON:0001756 (conductive hearing loss) - Eye UBERON:0000970 (nystagmus, strabismus, optic nerve hypoplasia) - Hand / digits UBERON:0002398 (short palms, tapered fingers, broad thumbs) - Abdominal wall (umbilical hernia); foot (talipes)

Body systems: nervous (central and peripheral reflex arc), musculoskeletal/craniofacial, cardiovascular, respiratory/upper airway, endocrine, gastrointestinal (feeding), sensory.

Tissue and cell level

Neuroepithelium / ventricular and subventricular zone — the primary site of the cellular lesion
Neural progenitor cells CL:0011020; radial glia CL:0000681 / CL:0013000; intermediate (basal) progenitors (TBR2⁺/INSM1⁺ — no precise CL term; use CL:0011020 with a more specific preferred_term)
Neurons — reduced production; oligodendrocytes/myelin — hypomyelination
Cranial suture osteogenic tissue — premature fusion
Cardiac septal/valvular mesenchyme — CHD
Laryngeal cartilage/connective tissue — laryngomalacia

Subcellular level

Nucleus / nucleoplasm GO:0005654 — primary site of SNIP1 action
Spliceosomal complex GO:0005681 — the direct molecular machine affected
PcG protein complex (PRC2) GO:0031519
Mitochondrion — indirectly, via the intrinsic (caspase‑9/apoptosome) apoptotic pathway GO:0097193

Localization / lateralization

Bilateral and symmetric throughout (brain malformations, craniosynostosis, hand anomalies, nystagmus/strabismus). No lateralized or asymmetric pattern reported. Cloverleaf skull reflects multi‑suture, bilateral synostosis.

8. Temporal Development

Onset

Congenital / neonatal. Hypotonia and poor feeding are apparent in early infancy; the HPO annotation explicitly records onset = "Early infancy" for feeding difficulties.
54% are small for gestational age, indicating prenatal growth effects.
Onset pattern: congenital and insidiously evolving — the craniofacial gestalt is described as evolving over time ("Dysmorphic features that evolve over time…" [BODY, PMID:22279524]), so the disorder may be less recognisable in the neonatal period than in later childhood.
Seizure onset: infantile or childhood.

Suggested HPO onset terms: HP:0003577 Congenital onset · HP:0003623 Neonatal onset · HP:0003593 Infantile onset.

Progression

Course: static‑encephalopathy‑like in its developmental substrate, but with progressive craniofacial/skull features, progressive epilepsy burden in some, and cumulative complications (aspiration, airway, cardiomyopathy).
Rate: slow; developmental gains continue (ambulation achieved between ages 3 and 10 years).
Duration: chronic, lifelong; not self‑limited.
Stages: no formal staging system exists. A practical framing: (i) neonatal — hypotonia/feeding/airway; (ii) infancy–early childhood — seizure onset, skull evolution, CHD management; (iii) mid‑childhood — motor gains, behavioural phenotype, drug‑resistant epilepsy; (iv) adolescence/adulthood — poorly characterised (oldest patient in the 2021 cohort was 26 years).

Patterns

Remission: none. No spontaneous or treatment‑induced remission of the core phenotype. Seizures are not reliably remitting.
Critical periods / windows of intervention:
Prenatal/early embryonic — the true window for the neurodevelopmental lesion (mouse dysplasia is established by E15); realistically unreachable therapeutically.
Neonatal — airway and feeding intervention; newborn hearing screen; echocardiogram.
Infancy — early EEG and anticonvulsant optimisation (explicitly recommended to prevent status epilepticus and treat apnoea).
Infancy–early childhood — craniosynostosis surgical timing.
Ongoing — thyroid surveillance, cardiomyopathy surveillance.

9. Inheritance and Population

Epidemiology

Prevalence: not formally estimated. No population prevalence figure exists. The disorder is ultra‑rare worldwide and effectively population‑restricted to Old Order Amish.
Cases described: 51 affected individuals of Old Order Amish descent identified across 21 families / 27 sibships, of whom 35 were clinically evaluated (19 M, 16 F), age range 1 month – 26 years [BODY, PMID:34570759]; plus 3 individuals from 2 sibships in the original 2012 report (overlapping cohort).
Recommended dismech Prevalence records:
measure_type: CASES_IN_LITERATURE, prevalence_class: ULTRA_RARE, population: Worldwide, notes: 51 affected individuals identified (Ammous 2021).
measure_type: CARRIER_FREQUENCY, population: Old Order Amish, rate_per_100000: 2941 (1/34 ≈ 2.94%), source GeneReviews NBK558237.
measure_type: CARRIER_FREQUENCY, population: Old Order Amish control chromosomes (Puffenberger 2012), 5/203 chromosomes = 2.5% allele‑carrier estimate.
Allele‑frequency records for PA Amish (0.5%) vs OH/IN/WI Amish (1.4%).
Incidence: not reported. A rough derivation from a 1/34 carrier frequency under random mating within the community gives an expected affected‑birth rate of ~1/4,600 — do not curate this as a sourced figure; it is an inference, and Amish mating is not random.

Inheritance

Pattern: Autosomal recessive — HPO HP:0000007; suggested GENO/inheritance binding per dismech Inheritance class with inheritance_term = HP:0000007 and term: populated.
Penetrance: complete in homozygotes within the studied cohort — "no unaffected individuals being homozygous for this variant" [BODY, PMID:34570759].
Expressivity: variable but with an invariant core. Eight features are 100% penetrant (GDD, hypotonia, hyporeflexia, seizures, feeding difficulties, abnormal skull shape, high palate, wide mouth/cupid's bow); the variable features are cardiac, endocrine, airway, ophthalmologic and MRI findings. Cloverleaf skull occurred in only 5 individuals — the most striking intra‑genotype variability.
Anticipation: not applicable (not a repeat‑expansion disorder).
Germline mosaicism: not reported.
Founder effect: yes — this is the defining epidemiological feature. A single Amish founder haplotype accounts for ~100% of pathogenic SNIP1 alleles in this population.
Consanguinity: central. The disorder was mapped by autozygosity/homozygosity mapping in an endogamous population; all patients are homozygous by descent.
Carrier frequency: 1/34 Old Order Amish (GeneReviews 2023).

Population demographics

Affected populations: Old Order Amish (Pennsylvania; Ohio/Indiana/Wisconsin settlements). gnomAD contains 11 heterozygotes, 10 of whom are Amish — i.e., the variant is essentially absent from non‑Amish populations.
Geographic distribution: Lancaster County PA; Geauga County OH and related Midwest settlements. The allele frequency differs ~3‑fold between settlements (0.5% PA vs 1.4% OH/IN/WI), a classic sub‑founder‑effect signal.
Sex ratio: ~1:1 (19 M : 16 F in the evaluated cohort) — consistent with autosomal inheritance.
Age distribution: paediatric‑weighted; 1 month to 26 years in the reported cohort. Adult natural history is essentially undescribed — a major knowledge gap.

10. Diagnostics

Clinical tests

Domain	Test	Findings / purpose
Electrophysiology	EEG — LOINC/`HP:0002353` EEG abnormality	Abnormal; the 2021 paper recommends "EEG should be obtained at an early stage" [BODY]
Imaging	Brain MRI	50% abnormal; hydrocephalus, ventriculomegaly, white‑matter change, thin corpus callosum, hypomyelination, irregular cortical ribbon, Chiari malformation, absent septum pellucidum, optic nerve hypoplasia, septo‑optic dysplasia
Imaging	Skull CT / 3D CT	multi‑suture craniosynostosis, cloverleaf skull, irregular calvarial surface
Imaging	Echocardiogram	ASD, VSD, coarctation, bicuspid aortic valve, aortic stenosis; LV non‑compaction cardiomyopathy. "echocardiogram should be undertaken to screen for congenital heart defects" [BODY]
Laboratory	Thyroid function (TSH, free T4)	hypothyroidism in 25%
Laboratory	Glucose	hypoglycaemia in ~20%
Functional	Video‑fluoroscopic swallow study / modified barium swallow	aspiration in 46%
Functional	Direct laryngoscopy / bronchoscopy; sleep study	laryngomalacia, subglottic stenosis, apnoea
Sensory	Newborn hearing screen / audiology	21% failed (conductive)
Sensory	Ophthalmology	nystagmus, strabismus, optic nerve hypoplasia
Biopsy / pathology	None indicated	No diagnostic histopathology or IHC exists for this disorder

Biomarkers: none. No circulating protein, metabolite, or imaging biomarker is validated. Curation gap.

Genetic testing

Recommended approach, tiered:

Targeted single‑variant testing for SNIP1 c.1097A>G in any Plain‑community child with the phenotype. A dedicated clinical assay exists: DDC Clinic Laboratory, "Symptomatic Epilepsy and Skull Dysplasia (SNIP1) Targeted Testing." Amish/Mennonite multi‑variant founder panels (Clinic for Special Children, DDC Clinic) also include it. This is the highest‑yield, lowest‑cost first‑line test in the at‑risk population, and the GeneReviews Amish founder‑variant chapter lists it accordingly.
Exome (WES) or genome (WGS) sequencing for non‑Plain patients or phenotype‑first presentations — this is how the gene was discovered (WES at the Broad Institute, PMID:22279524) and remains the only route to identify hypothetical non‑founder SNIP1 alleles.
Epilepsy / intellectual‑disability gene panels — SNIP1 is included on many commercial NDD and epilepsy panels (see NCBI GTR, "Clinical and research tests for SNIP1").
Chromosomal microarray (CMA) — relevant for detecting 1p34.3p34.2 deletions encompassing SNIP1 (PMID:29726122), a different mechanism/phenotype.
Karyotype, FISH, mtDNA testing, repeat‑expansion testing: not indicated.
SNP‑array autozygosity mapping — the research method that mapped the locus; still relevant in consanguineous families with unsolved phenotypes.

Omics‑based diagnostics

RNA sequencing: research‑grade only. Patient transcriptome signatures (TGF‑β EMT pathway, ROBO1/CNTNAP2/PAFAH1B1) are not validated as a diagnostic assay. Given the splicing mechanism (§6.2), RNA‑seq for aberrant splicing/detained‑intron signatures is a plausible but unvalidated future diagnostic — worth recording as a discussions KNOWLEDGE_GAP with proposed experiments.
Proteomics / metabolomics / epigenomics / liquid biopsy: none available or applicable.

Clinical criteria

No formal consensus diagnostic criteria (no DSM/ICD/society guideline) exist. Diagnosis is molecular, supported by a recognisable gestalt. Practical criteria: Old Order Amish ancestry + neonatal hypotonia/poor feeding + severe non‑verbal GDD + epilepsy + wide mouth/cupid's‑bow/high palate/abnormal skull shape → targeted SNIP1 testing.

Differential diagnosis

Condition	Distinguishing features
Other Amish/Plain founder NDDs (e.g. BRAT1 lethal neonatal rigidity‑multifocal seizure, TUBGCP6, CRADD, HARS, SLC6A3, FLVCR1 — all in the same 2012 discovery paper)	Overlapping community and severe‑NDD phenotype; distinguished molecularly, and by the SNIP1 skull/craniofacial gestalt
Syndromic craniosynostosis (FGFR2/FGFR3/TWIST1 — Pfeiffer, Crouzon, Apert; cloverleaf skull)	Cloverleaf skull overlaps strikingly; distinguished by AD inheritance, limb findings, and normal/near‑normal cognition in many
Developmental and epileptic encephalopathies (STXBP1, CDKL5, SCN2A, etc.)	Lack the distinctive craniofacial/skull gestalt and near‑universal CHD/airway involvement
Pierre Robin sequence syndromes (SOX9 regulatory, Stickler, EFTUD2/MFDM)	Present in 3 SNIP1 patients; MFDM (EFTUD2) is another spliceosomopathy with craniofacial disease
Septo‑optic dysplasia (HESX1, etc.)	Overlapping midline MRI findings in a subset
1p34.3p34.2 microdeletion	Heterozygous CNV, milder ID, distinct feature set
Chromosomal/CNV disorders generally	Excluded by CMA

Screening

Newborn screening: SNIP1 is not on any state NBS panel and the disorder is not NBS‑amenable (no biochemical marker). However, the failed newborn hearing screen in 21% is a real incidental ascertainment route.
Carrier screening: highly appropriate and actively practiced — the variant is on Plain‑community founder‑variant carrier panels (Clinic for Special Children; DDC Clinic).
Cascade screening: standard for at‑risk siblings and extended family in an endogamous pedigree structure.

11. Outcome / Prognosis

Survival and mortality

[BODY] PMID:34570759 — "Six children died between ages 9 months and 11 years as a consequence of infection, sudden cardiopulmonary arrest, or accidental drowning."

Case fatality in the reported cohort: 6 deaths among the evaluated individuals — ≈17% mortality in a cohort spanning 1 month to 26 years. This is a crude, non‑actuarial figure; no Kaplan–Meier survival curve, 5‑/10‑year survival rate, or life‑expectancy estimate has been published.
Causes of death (all three named): infection; sudden cardiopulmonary arrest; accidental drowning.
Disease‑specific mortality mechanisms: aspiration/respiratory infection (46% aspiration rate, 75% upper‑airway abnormality), cardiac (CHD in 60%, LVNC cardiomyopathy in 12% — the plausible substrate for "sudden cardiopulmonary arrest"), and seizure‑related risk (status epilepticus; drowning during an unwitnessed seizure is a well‑recognised epilepsy mortality mode). SUDEP is not explicitly invoked by the authors — do not assert it.
Survival to at least 26 years is documented.

Morbidity and function

Cognitive: severe intellectual disability, non‑verbal.
Motor: most achieve independent ambulation (ages 3–10 years) — a meaningfully better motor outcome than the cognitive outcome.
Communication: some use signs, gestures, and sounds; no spoken language.
Feeding: universal difficulty; gastrostomy dependence common.
Disability outcome: lifelong, profound dependence for self‑care; ICF‑level severe activity limitation across learning, communication, and self‑care domains.
Quality‑of‑life instruments: none applied. No EQ‑5D, PedsQL, PROMIS, or disease‑specific measure has been reported.

Complications

Recurrent respiratory infection and pneumonia (aspiration‑driven); status epilepticus; apnoea (infancy); airway obstruction (laryngomalacia, subglottic stenosis); congestive heart failure/arrhythmia risk from CHD and LVNC; raised intracranial pressure and secondary visual/neurological compromise from multi‑suture craniosynostosis; hydrocephalus; hypothyroidism; hypoglycaemia; conductive hearing loss; failure to thrive; orthopaedic sequelae (talipes, kyphoscoliosis in the deletion case).

Recovery potential

None. No recovery or reversal of the neurodevelopmental phenotype is possible; management is entirely supportive and complication‑preventive.

Prognostic factors

Not formally studied. Clinically plausible (and explicitly targeted by the authors' management recommendations) determinants of outcome: severity/multiplicity of craniosynostosis, presence and severity of CHD or cardiomyopathy, degree of airway compromise and aspiration, and seizure control. Prognostic biomarkers: none. All of the above should be recorded as clinical reasoning, not as evidenced prognostic factors.

12. Treatment

There is no disease‑modifying or targeted therapy. Management is entirely supportive, anticipatory, and multidisciplinary. The 2021 PLoS Genetics paper is the only source of formal management recommendations.

Key management recommendations (from PMID:34570759, [BODY])

"elective gastrostomy tube placement to support growth and limit pulmonary aspiration"
"careful optimisation of anticonvulsant medications to treat apnea in infancy, maintain seizure control, and prevent status epilepticus"
"EEG should be obtained at an early stage"
"Neuroimaging should be performed at diagnosis, and echocardiogram should be undertaken to screen for congenital heart defects"

Treatment table with suggested NCIT annotations

Treatment	Description	Suggested `treatment_term` (NCIT)	`therapeutic_modality`
Antiseizure medication	No agent provides consistently effective control; multi‑drug resistance common; goal is seizure reduction, apnoea control in infancy, and status‑epilepticus prevention	`NCIT:C15986` Pharmacotherapy; `therapeutic_agent` should be omitted or generic — no specific agent is endorsed	`SMALL_MOLECULE`
Gastrostomy tube placement (elective)	Supports growth, limits aspiration	`NCIT:C157864` Gastrostomy Tube Procedure (verify reachability from NCIT:C25218; fallback `NCIT:C15329` Surgical Procedure)	`SURGERY`
Craniosynostosis / cranial vault surgery	For multi‑suture and cloverleaf synostosis, ICP management	`NCIT:C15329` Surgical Procedure (a more specific cranioplasty term should be sought with OAK)	`SURGERY`
Airway surgery (supraglottoplasty, tracheostomy)	For laryngomalacia, subglottic stenosis, obstructive apnoea	`NCIT:C15329` Surgical Procedure	`SURGERY`
Cardiac surgery / catheter intervention	ASD/VSD repair, coarctation repair	`NCIT:C15329` Surgical Procedure	`SURGERY`
Levothyroxine replacement	For hypothyroidism (25%)	`NCIT:C15986` Pharmacotherapy + `therapeutic_agent` levothyroxine (`CHEBI:81826` levothyroxine — verify with OAK)	`SMALL_MOLECULE`
Nutritional support	Growth failure, feeding difficulty	`NCIT:C15433` Nutritional Support	(do not auto‑tag `BEHAVIORAL` — see CLAUDE.md guidance)
Physical therapy	Hypotonia, ambulation training	`NCIT:C15302` Physical Therapy	`BEHAVIORAL`
Occupational therapy	Self‑care, adaptive function	`NCIT:C121351` Occupational Therapy	`BEHAVIORAL`
Speech and language therapy / AAC	Non‑verbal communication, sign/gesture support	`NCIT:C159273` Speech Therapy	`BEHAVIORAL`
Hearing amplification / ENT management	Conductive loss (21%)	(no reliable NCIT clinical‑action term for device use)	`DEVICE`
Ophthalmologic management	Strabismus, nystagmus, optic nerve hypoplasia	`NCIT:C15329` Surgical Procedure (strabismus surgery) / supportive	`SURGERY`
Supportive / palliative care	Symptom management, family support	`NCIT:C15747` Supportive Care	`OTHER`
Genetic counselling	AR recurrence risk 25%; carrier testing for relatives	`NCIT:C15240` Genetic Counseling	`BEHAVIORAL`

Pharmacogenomics

None established. No SNIP1‑specific PGx guidance (no CPIC/PharmGKB entry). Standard antiseizure‑drug PGx caveats apply generically (e.g. HLA‑B15:02 and carbamazepine), but are not disorder‑specific* — do not curate as SNIP1‑related.

Advanced therapeutics

Gene therapy / gene editing: none; not in preclinical development for this indication.
ASO / RNA therapy: none. Note the conceptual tension: the pathogenic mechanism is a splicing‑machinery defect (trans‑acting), not a cis‑acting splice variant, so classical exon‑skipping ASO logic does not apply. Do not associate this entry with the antisense_oligonucleotide_therapy module.
Cell therapy, immunotherapy, targeted small molecules: none.
Theoretical target from mouse work: the Nat Commun 2023 finding that PRC2 (EED) depletion rescues apoptosis and brain dysplasia in Snip1‑null mouse brain identifies PRC2/EZH2 inhibition as a mechanistically motivated but entirely unproven therapeutic hypothesis. There is no human, in‑vivo‑disease, or translational evidence, and the rescue was in a null (not E366G) background during embryonic development — a window that is not clinically actionable. Record as a mechanistic_hypotheses entry with status: EMERGING and a HUMAN_MODEL_MISMATCH discussion, not as a treatment.

Clinical trials

A ClinicalTrials.gov API v2 query for "SNIP1" returned zero studies (retrieved 2026‑08‑01). No interventional or observational trial is registered for this disorder.

Treatment outcomes

Response rates: not reported for any intervention. The single explicit efficacy statement is a negative one — no antiepileptic provides consistent seizure control.
Adverse events: no disorder‑specific AE data. Standard risks of gastrostomy, craniofacial surgery, and antiseizure polypharmacy apply.

Treatment strategy

No published algorithm. The de‑facto pathway from the 2021 paper: molecular diagnosis → baseline EEG + brain MRI + echocardiogram → airway and swallow assessment → early elective gastrostomy → anticonvulsant optimisation → craniofacial surgical assessment → thyroid surveillance → developmental therapies → genetic counselling and family carrier testing. Personalised‑medicine approaches beyond genotype‑confirmed diagnosis: none.

13. Prevention

Primary prevention

Not possible for an affected conceptus. Population‑level primary prevention operates entirely through reproductive genetics: - Carrier screening in Plain communities (Clinic for Special Children, DDC Clinic founder‑variant panels) — high yield given a 1/34 carrier frequency. - Genetic counselling with 25% sibling recurrence risk. - Reproductive options: partner carrier testing, prenatal diagnosis (CVS/amniocentesis targeted variant testing), preimplantation genetic testing for monogenic disease (PGT‑M) where culturally acceptable. (Note: uptake of PGT‑M and pregnancy termination is culturally constrained in Plain communities; counselling in these communities is typically framed around informed reproductive decision‑making and preparedness, not termination.)

Secondary prevention (early detection)

Cascade/at‑birth targeted testing in known carrier families, enabling neonatal anticipatory care rather than diagnostic odyssey.
The 2021 recommendations are essentially a secondary‑prevention program: early EEG, baseline neuroimaging, screening echocardiogram, hearing screen, thyroid function testing, swallow assessment.

Tertiary prevention (complication prevention) — the highest‑value tier here

Elective (pre‑emptive) gastrostomy to prevent aspiration pneumonia and growth failure — this is an explicit prevention‑framed recommendation.
Anticonvulsant optimisation to prevent status epilepticus and treat infantile apnoea.
Water safety supervision — accidental drowning was one of three named causes of death in a cohort where every patient has epilepsy. This is an obvious, concrete, family‑level preventive measure, though it is not stated as a formal recommendation in the paper.
Cardiac surveillance for CHD and LVNC cardiomyopathy.
Thyroid surveillance for treatable hypothyroidism.
Airway surveillance and timely ENT intervention.
ICP monitoring / timely craniofacial surgery in multi‑suture synostosis.

Immunization

No disease‑specific vaccine. Routine and enhanced immunisation (influenza, pneumococcal, RSV) is clinically important given aspiration risk and infection as a leading cause of death — but this is general good practice, not a published disorder‑specific recommendation. Suggested NCIT if curated: NCIT:C15346 Vaccination, therapeutic_modality: VACCINE. Note: vaccination coverage is historically lower in some Plain communities, which is a real public‑health consideration for this population.

Public health / environmental interventions

Community‑partnered genetics services (the Clinic for Special Children / DDC Clinic model) are the operative public‑health intervention: low‑cost founder‑variant testing embedded in a trusted community clinic. No environmental intervention applies.

14. Other Species / Natural Disease

Taxonomy and orthologs

Species	NCBI Taxon	Gene	NCBI Gene ID	Notes
Homo sapiens	`NCBITaxon:9606`	SNIP1	79753
Mus musculus	`NCBITaxon:10090`	Snip1	76793	MGI:2156003; chromosome 4, 124,960,465–124,967,835 bp (+); 57.99 cM
Rattus norvegicus	`NCBITaxon:10116`	Snip1	313588	RGD:1359268
Danio rerio	`NCBITaxon:7955`	snip1 (a.k.a. pml1)	793873 (verify)	RES complex component
Saccharomyces cerevisiae	`NCBITaxon:4932`	PML1	—	The yeast RES‑complex subunit; the source of SNIP1's alias "PML1"
Arabidopsis thaliana	`NCBITaxon:3702`	DAWDLE (DDL)	—	Functional analogue: FHA‑domain protein in small‑RNA biogenesis (PMID:18632581)

Breed

Not applicable — no VBO breed association; no domestic‑animal breed disorder is known.

Natural disease in other species

None identified. Targeted searching found no OMIA entry for SNIP1 in any species — no naturally occurring SNIP1‑related disease is recorded in dogs, cattle, horses, or other domestic animals as of this search. All animal data are experimentally induced (§15).

Caveat: this is a "not found in search" result, not a proof of absence. Curate as "no naturally occurring animal disease reported" rather than as a positive negative.

Comparative biology and evolutionary conservation

SNIP1 is deeply conserved — described as "a highly conserved nuclear protein" [ABSTRACT, PMID:38304835]. Glu366 itself is "highly conserved" across species [BODY, PMID:22279524], which is the conservation argument underpinning pathogenicity.
The RES complex (Bud13p/Pml1p/Snu17p) is conserved from yeast to vertebrates, and its splicing function is conserved: [ABSTRACT, PMID:29969449] "The retention and splicing (RES) complex is formed by three different proteins (Bud13p, Pml1p and Snu17p) and is involved in splicing in yeast."
The neurodevelopmental requirement is conserved across vertebrates — zebrafish snip1 mutants and mouse Snip1 conditional knockouts both show excess brain cell death and reduced neurogenesis (see §15), matching the human cortical/midline malformation phenotype. This cross‑species convergence is the single strongest argument that the human disorder is a neural‑progenitor‑survival disease.
Divergence to note: mouse Snip1 null is prenatally lethal, whereas humans homozygous for E366G survive to adulthood — consistent with E366G being hypomorphic rather than null. This is a genuine human‑model mismatch to record.

Transmission

Not applicable — non‑infectious, non‑zoonotic, no cross‑species susceptibility.

15. Model Organisms

15.1 Mouse (Mus musculus) — the principal model

MGI:2156003, Snip1, chromosome 4. MGI records 15 mutations/alleles: 1 ENU chemically induced, 2 other chemically induced, 5 endonuclease‑mediated, 1 gene‑trapped, 1 radiation‑induced, 5 targeted, 4 genomic mutations.

Constitutive null — IMPC / MGI:

"Mice homozygous for a knock-out allele exhibit prenatal lethality." (MGI phenotype summary)

IMPC data for Snip1^tm1a(EUCOMM)Wtsi:

MP phenotype	Zygosity	Sex	p‑value
Preweaning lethality, complete penetrance	homozygote	—	0.0
Abnormal tail movements	heterozygote	—	7.93E‑6
Decreased circulating total protein level	heterozygote	male	7.29E‑8
Decreased circulating iron level	heterozygote	male	2.66E‑5
Abnormal placement of pupils	heterozygote	female	1.54E‑5

(Note the heterozygous neurological/ocular signals — "abnormal tail movements," "abnormal placement of pupils" — which weakly echo the human nystagmus/strabismus and neurological phenotype and support dosage sensitivity. Treat as suggestive only; IMPC het findings are noisy.)

Conditional neural knockout — the disease‑relevant model (PMID:37553330): - Allele/driver: Snip1-tm1a (Infrafrontier/EMMA 04224) → crossed to Actin‑FLPe to make Snip1‑flox → crossed to Nestin‑Cre = Snip1_Nes-KO (neural‑progenitor‑specific deletion) [BODY] - Phenotype: "By E15, Snip1_Nes-KO embryos displayed severe thinning of brain tissues and dysplasia with 100% penetrance" [BODY] - Cellular: marked reduction of SOX2⁺ NPCs and TBR2⁺ / INSM1⁺ intermediate progenitors; strong cleaved‑caspase‑3 induction in all ventricles; caspase‑9 inhibition robustly reduced apoptosis (caspase‑8 only modestly) [BODY] - Rescue: [ABSTRACT] "Depletion of PRC2 is sufficient to reduce apoptosis and brain dysplasia and to partially restore genetic programs in the SNIP1-depleted brain in vivo."

Conditional cerebellar knockout — neurodegeneration model (PMID:37027487): - [ABSTRACT] "Haploinsufficiency of Snip1 attenuates neurodegeneration and globally rescues IDT accumulation caused by a previously reported mutant U2 snRNA, a basal spliceosomal component. Snip1 conditional knockout in the cerebellum decreases DI splicing efficiency and causes neurodegeneration." - Note the bidirectional result: Snip1 haploinsufficiency is protective in a mutant‑U2 neurodegeneration background, while cerebellar Snip1 cKO is causative. This is a genuinely non‑trivial dose/context dependency worth capturing as a mechanistic_hypotheses nuance.

15.2 Zebrafish (Danio rerio)

PMID:29969449 — Fernandez JP, Moreno‑Mateos MA, Gohr A, et al. "RES complex is associated with intron definition and required for zebrafish early embryogenesis." PLoS Genet 2018;14(7):e1007473. doi:10.1371/journal.pgen.1007473

[ABSTRACT] "In this study, we have generated loss-of-function mutants for the three components of the RES complex in zebrafish and showed that they are required during early development. The mutants showed a marked neural phenotype with increased cell death in the brain and a decrease in differentiated neurons. Transcriptomic analysis of bud13, snip1 (pml1) and rbmx2 (snu17) mutants revealed a global defect in intron splicing, with strong mis-splicing of a subset of introns."

This is the most phenotype‑congruent model for the human brain phenotype at the whole‑organism level: brain‑specific cell death + reduced neuron production + global splicing defect, all in one organism, and it independently corroborates the mouse NPC‑apoptosis result via a completely different route (splicing rather than PRC2).

15.3 Cellular / in vitro systems

HEK293/HeLa transfection studies of the E366G mutant (PMID:22279524) — showed nuclear aggregation and ~85% reduced protein abundance.
Acute SNIP1 depletion + FHA‑domain mutant rescue in human cells (PMID:41904131) — quantitative proteomics of chromatin‑associated spliceosomes, iCLIP‑seq; directly tested the E366G variant and showed impaired P‑SF3B1 binding, splicing defects, and reduced cell viability. This is the definitive variant‑specific functional assay available.
iPSC / organoid models: none published. Given the NPC‑apoptosis mechanism, patient‑derived iPSC cortical organoids are the obvious missing model — a strong candidate for a proposed_experiments entry in a KNOWLEDGE_GAP discussion.
MorPhiC: SNIP1 is not among the named MorPhiC anchor genes (ISL1, EOMES, GCM1, NKX2‑1); no MorPhiC dataset applies.

15.4 Phenotype recapitulation and limitations

Human feature	Mouse (Nes‑cKO)	Zebrafish	Recapitulated?
Brain dysplasia / cortical malformation	✅ severe, 100% penetrant	✅ increased brain cell death	Yes
Reduced neurogenesis	✅ NPC/IPC loss	✅ fewer differentiated neurons	Yes
Seizures	✗ not assessed (embryonic lethality precludes)	✗	No
Craniofacial gestalt / craniosynostosis	✗ not reported	✗	No
Congenital heart defects	✗ not reported	✗	No
Hypotonia / feeding failure	✗	✗	No
Survival to adulthood	✗ (null = lethal)	✗ (early lethal)	No — key mismatch

Limitations to record explicitly (candidate HUMAN_MODEL_MISMATCH discussion): 1. No E366G knock‑in mouse exists. Every in‑vivo model is a null or conditional null, whereas the human allele is a hypomorph. Null mice die prenatally; humans live to at least 26 years. Conclusions about the human disorder drawn from null models are therefore directionally informative but quantitatively wrong. 2. Nestin‑Cre deletion is neural‑restricted, so it cannot model the craniofacial, cardiac, airway, or endocrine components — i.e., the multisystem, "recognisable syndrome" part of the disease is entirely unmodelled. 3. Embryonic lethality precludes modelling epilepsy, the single most disabling human feature. 4. The PRC2‑depletion rescue was performed in a null background during embryogenesis — it does not establish that PRC2 inhibition would help a living patient with a hypomorphic allele. 5. Zebrafish snip1 mutants are studied as RES‑complex loss, not as a disease model per se.

15.5 Model resources

MGI (informatics.jax.org, MGI:2156003) · IMPC (Snip1^tm1a(EUCOMM)Wtsi) · Infrafrontier/EMMA line 04224 (the tm1a allele used in PMID:37553330) · EUCOMM/KOMP repositories · RGD (RGD:1359268) · ZFIN (zebrafish snip1/pml1 mutants from PMID:29969449) · Alliance of Genome Resources.

Appendix A — Consolidated reference list

PMID	Citation	Role	Evidence source
34570759	Ammous Z, Rawlins LE, Jones H, et al. A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder. PLoS Genet 2021;17(9):e1009803. doi:10.1371/journal.pgen.1009803	Primary clinical cohort (n=35–51); management recommendations; patient transcriptome	HUMAN_CLINICAL
22279524	Puffenberger EG, Jinks RN, Sougnez C, et al. Genetic mapping and exome sequencing identify variants associated with five novel diseases. PLoS One 2012;7(1):e28936. doi:10.1371/journal.pone.0028936	Gene discovery; mapping; carrier frequency; E366G protein instability	HUMAN_CLINICAL (+ IN_VITRO for the mutant‑protein experiments — split into two evidence items)
41904131	Gajdušková P, Ruiz de Los Mozos I, Hluchý M, et al. Phosphorylation of SF3B1 by CDK11 orchestrates spliceosome activation via SNIP1‑dependent RES complex recruitment. Nat Commun 2026. doi:10.1038/s41467-026-71119-2	Definitive E366G functional mechanism (splicing)	IN_VITRO
37553330	Matsui Y, Djekidel MN, Lindsay K, et al. SNIP1 and PRC2 coordinate cell fates of neural progenitors during brain development. Nat Commun 2023;14:4771. doi:10.1038/s41467-023-40487-4	NPC apoptosis mechanism; PRC2/H3K27me3; mouse cKO	MODEL_ORGANISM
37027487	Meng D, Zheng Q, Zhang X, et al. A molecular brake that modulates spliceosome pausing at detained introns contributes to neurodegeneration. Protein Cell 2023;14(1):27–53. doi:10.1093/procel/pwac008	SNIP1–RNPS1 spliceosome brake; cerebellar cKO neurodegeneration	MODEL_ORGANISM
29969449	Fernandez JP, Moreno‑Mateos MA, Gohr A, et al. RES complex is associated with intron definition and required for zebrafish early embryogenesis. PLoS Genet 2018;14(7):e1007473. doi:10.1371/journal.pgen.1007473	Zebrafish snip1 mutant; brain cell death; splicing	MODEL_ORGANISM
38304835	Chen Y, Guo W, Guo X, Wanqing Q, Yin Z. The clinical utilization of SNIP1 and its pathophysiological mechanisms in disease. Heliyon 2024;10(2):e24601. doi:10.1016/j.heliyon.2024.e24601	Review of SNIP1 biology (Smad4/RelA/c‑Myc)	OTHER (review)
10887155	Kim RH, Wang D, Tsang M, et al. A novel smad nuclear interacting protein, SNIP1, suppresses p300‑dependent TGF‑β signal transduction. Genes Dev 2000	SNIP1 discovery; TGF‑β arm	IN_VITRO
11567019	Kim RH, Flanders KC, Birkey Reffey S, et al. SNIP1 inhibits NF‑κB signaling by competing for its binding to the C/H1 domain of CBP/p300. J Biol Chem 2001	NF‑κB arm	IN_VITRO
15378006	Roche KC, Wiechens N, Owen‑Hughes T, Perkins ND. The FHA domain protein SNIP1 is a regulator of the cell cycle and cyclin D1 expression. Oncogene 2004	FHA domain; cell cycle	IN_VITRO
17157259	Fujii M, Lyakh LA, Bracken CP, et al. SNIP1 is a candidate modifier of the transcriptional activity of c‑Myc on E box‑dependent target genes. Mol Cell 2006	c‑Myc arm	IN_VITRO
17260016	Roche KC, Rocha S, Bracken CP, Perkins ND. Regulation of ATR‑dependent pathways by the FHA domain containing protein SNIP1. Oncogene 2007	DNA damage response	IN_VITRO
18794151	Bracken CP, Wall SJ, Barré B, et al. Regulation of cyclin D1 RNA stability by SNIP1. Cancer Res 2008	Cyclin D1 mRNA stability	IN_VITRO
18632581	Yu B, Bi L, Zhai J, et al. The FHA domain proteins DAWDLE in Arabidopsis and SNIP1 in humans act in small RNA biogenesis. PNAS 2008	miRNA biogenesis; plant ortholog	IN_VITRO
30404004	Chen LL, Lin HP, Zhou WJ, et al. SNIP1 Recruits TET2 to Regulate c‑MYC Target Genes and Cellular DNA Damage Response. Cell Rep 2018	Epigenetic (TET2) arm	IN_VITRO
29726122	Jacher JE, Innis JW. Interstitial microdeletion of the 1p34.3p34.2 region. Mol Genet Genomic Med 2018;6(4):649–654. doi:10.1002/mgg3.409	Heterozygous CNV including SNIP1 — distinct entity	HUMAN_CLINICAL
29426045	Ruan H, Zhang Z, Tian L, et al. Smad nuclear interacting protein 1 (SNIP1) inhibits intestinal inflammation through regulation of epithelial barrier function. Mucosal Immunol 2018	Non‑neural SNIP1 biology (context)	MODEL_ORGANISM

Non‑PMID resources: GeneReviews NBK558237 (Wallace SE, Puffenberger EG, Bean LJH, "Genetic Disorders Associated with Founder Variants Common in the Amish Population," last update 2023‑12‑07) · OMIM #614501 and *608241 · ClinVar Variation 30717 / RCV000023695 · dbSNP rs387906986 · UniProt Q8TAD8 · HGNC:30587 · MGI:2156003 · IMPC · HPO disease annotations for OMIM:614501 (ontology.jax.org) · NCBI GTR (SNIP1 tests) · DDC Clinic Laboratory (Symptomatic Epilepsy and Skull Dysplasia targeted test) · Clinic for Special Children.

Appendix B — Curation gaps and open questions (candidate `discussions` entries)

Gap	Kind	Note
No Orphanet/ORDO entry exists for this disorder	`KNOWLEDGE_GAP`	Verified absent in OLS4 ORDO; MONDO carries no ORPHA xref. Consider proposing one upstream.
No non‑Amish patients reported; entire disease concept rests on one founder allele	`KNOWLEDGE_GAP`	Systematic literature search (2021–2026) found no additional biallelic SNIP1 families. Whether the phenotype generalises to other SNIP1 alleles is unknown.
No E366G knock‑in animal model	`HUMAN_MODEL_MISMATCH`	All in‑vivo models are nulls; nulls are lethal, humans survive to ≥26 years. Proposed experiment: Snip1^E366G/E366G knock‑in mouse with EEG, craniofacial µCT, and echocardiography.
PRC2‑depletion rescue is embryonic and null‑background only	`HUMAN_MODEL_MISMATCH`	Cannot support a therapeutic claim. Proposed experiment: EZH2 inhibition in a hypomorphic model or patient iPSC‑derived cortical organoids.
Mechanism of hypoglycaemia (~20%) unexplained	`KNOWLEDGE_GAP`	Not attributable to any known SNIP1 function; may be secondary to feeding failure.
No adult natural‑history data	`KNOWLEDGE_GAP`	Oldest reported patient 26 years; whether the cerebellar‑cKO neurodegeneration phenotype has a human adult correlate is untested.
No patient iPSC/organoid model; no patient splicing (RNA‑seq detained‑intron) analysis	`KNOWLEDGE_GAP`	The 2026 splicing mechanism has never been tested in patient tissue.
No QoL, survival‑curve, or formal prognostic data	`KNOWLEDGE_GAP`	Mortality reported only as raw counts (6 deaths, ages 9 months–11 years).
FHA‑domain boundary discrepancy for residue 366	`KNOWLEDGE_GAP`	UniProt FHA = 281–344 (E366 outside); PMID:34570759 says "close proximity to"; PMID:41904131 calls E366G an FHA‑domain mutation. Record both.
ClinVar "Likely pathogenic" (1★) vs publication "pathogenic"	—	Record both classifications with their sources; do not silently upgrade.
Candidate new mechanism module: spliceosomopathy neurodevelopmental disorder	—	SNIP1 joins EFTUD2, SF3B4, SNW1, SF3B1, RNU4‑2; the "spliceosome/RES defect → NPC apoptosis → cortical malformation + craniofacial disease" chain is recurrent and modular. Worth proposing.

Sources: PLOS Genetics — A biallelic SNIP1 Amish founder variant causes a recognizable neurodevelopmental disorder · PMC8496849 · PLOS One — Genetic mapping and exome sequencing identify variants associated with five novel diseases · OMIM #614501 · OMIM *608241 · ClinVar RCV000023695 · HPO annotations for OMIM:614501 · MONDO:0013787 via EBI OLS4 · HGNC SNIP1 · UniProt Q8TAD8 · MGI:2156003 Snip1 · IMPC Snip1 genotype–phenotype · GeneReviews — Genetic Disorders Associated with Founder Variants Common in the Amish Population (NBK558237) · PubMed 37553330 · PMC10409800 · PubMed 41904131 · PubMed 37027487 · PubMed 29969449 · PubMed 38304835 · PubMed 29726122 · NCBI GTR — SNIP1 tests · DDC Clinic Laboratory — Symptomatic Epilepsy and Skull Dysplasia (SNIP1) Targeted Testing · QuickGO · ClinicalTrials.gov API v2

Ask OpenScientist

OpenScientist Report

Classifications

Inheritance

Mechanistic Hypotheses

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Differential Diagnoses

Source YAML

References & Deep Research

References

Deep Research

1. Disease Information

Overview

Key identifiers

Synonyms and alternative names

Nature of the evidence base

2. Etiology

Primary causal factor

Genetic risk factors

A second, distinct genetic mechanism (heterozygous deletion)

Environmental risk factors

Protective factors

Gene–environment interactions

3. Phenotypes

3.1 Frequency table (Ammous et al. 2021, n = 35–37 evaluated individuals)

3.2 Craniofacial gestalt (the "recognizable" feature)

3.3 Neuroimaging phenotype

3.4 Epilepsy phenotype (the dominant morbidity)

3.5 Developmental attainment and function

3.6 Quality‑of‑life impact

4. Genetic / Molecular Information

Causal gene

Pathogenic variant

Allele frequency

Functional consequences of p.Glu366Gly

Modifier genes

Epigenetic information

Chromosomal abnormalities

5. Environmental Information

6. Mechanism / Pathophysiology

6.1 SNIP1 protein: four functional arms

6.2 The splicing arm — the most direct route from E366G to disease

6.3 The neural‑progenitor survival arm

6.4 Patient transcriptome (human, in vivo)

6.5 Proposed causal chain (for pathophysiology nodes)

6.6 Suggested ontology terms

6.7 Metabolic, immune, and biochemical dimensions

6.8 Molecular profiling summary

7. Anatomical Structures Affected

Organ level

Tissue and cell level

Subcellular level

Localization / lateralization

8. Temporal Development

Onset

Progression

Patterns

9. Inheritance and Population

Epidemiology

Inheritance

Population demographics

10. Diagnostics

Clinical tests

Genetic testing

Omics‑based diagnostics

Clinical criteria

Differential diagnosis

Screening

11. Outcome / Prognosis

Survival and mortality

Morbidity and function

Complications

Recovery potential

Prognostic factors

12. Treatment

6.5 Proposed causal chain (for `pathophysiology` nodes)

Appendix B — Curation gaps and open questions (candidate `discussions` entries)