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Inheritance

1

Autosomal dominant inheritance HP:0000006

MRD34 is autosomal dominant and is caused by a heterozygous CERT1 variant that is de novo in the great majority of molecularly characterised individuals: 25 of the 27 patients with biparental samples in the defining cohort. Penetrance is recorded as INCOMPLETE on a narrow basis. One variant in the FFAT-motif cluster, p.V326F, was inherited from a reportedly unaffected father; a second inherited allele, p.A449V, came from a mother with intellectual disability that the authors judged independent of her CERT1 genotype, and they separately doubt whether that allele is pathogenic. So the evidence for reduced penetrance is one family, not a series.

Autosomal dominant inheritance Penetrance: INCOMPLETE Expressivity: VARIABLE De novo rate: 93% (25 of 27 patients with biparental samples in the defining cohort)

Show evidence (5 references)

PMID:36976648 SUPPORT Human Clinical

"Here, we characterize 31 individuals with de novo missense variants in CERT1."

The defining cohort establishes that the disorder arises from heterozygous de novo missense alleles, which is the autosomal dominant pattern.

PMID:36976648 SUPPORT Human Clinical

"Family segregation confirmed that CERT1 variants occurred de novo in 93% (25 of 27) of patients."

Quantifies the de novo fraction among the patients for whom biparental samples were available, which is the basis of the recorded de novo rate.

PMID:36976648 SUPPORT Human Clinical

"The p.V326F variant in S21 was inherited from her reportedly unaffected father, whereas the p.A449V variant in S26 was inherited from her mother, who was diagnosed with intellectual disability"

The basis for INCOMPLETE rather than COMPLETE penetrance: a variant in the functionally implicated FFAT-motif cluster was transmitted by a reportedly unaffected father. Note the second allele in the same sentence is weaker evidence, since the transmitting mother's intellectual disability was judged independent of her CERT1 genotype.

+ 2 more references

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Discussions and Knowledge Gaps

4

Which human neural cell type is the one whose sphingolipid homeostasis failure produces the MRD34 phenotype?

KNOWLEDGE GAP OPEN mrd34_vulnerable_cell_type

Attached to

pathophysiology#Impaired Neural Differentiation and Synaptic Membrane Function

The chain from constitutively active CERT to increased sphingomyelin synthesis is demonstrated in cells, and the clinical phenotype is established, but nothing connects them at cellular resolution in human tissue. Neurons, neural progenitors, oligodendrocytes, astrocytes and Schwann cells are all plausible on expression grounds. No patient-derived iPSC neuron, cerebral organoid, single-cell atlas or human neural lipidomic study of this disorder exists, so the entry deliberately binds only neuron at this node rather than asserting a primary cell type.

Does pharmacological rescue of the Drosophila CERT gain-of-function model predict any benefit in humans, given that the fly phenotype is motor and morphological while the human phenotype is cognitive, linguistic and behavioural?

HUMAN MODEL MISMATCH OPEN mrd34_drosophila_translational_validity

Attached to

pathophysiology#Constitutive CERT Activation treatments#Pharmacological CERT Inhibition

The only in vivo evidence that CERT inhibition is therapeutic comes from a fly. Drosophila has no cortical expansion, no myelinating oligodendrocytes and no language, so the readouts corrected in the model are not the manifestations that matter clinically. There is also a timing problem the model cannot address: the human phenotype is developmental, so a drug given after diagnosis acts on a nervous system already built under excess CERT activity. Finally, CERT is required for normal membrane lipid homeostasis in every tissue, so the therapeutic window in a developing human is unknown and over-inhibition is a plausible harm rather than a theoretical one.

Proposed experiments

CERT inhibitor rescue in patient-derived iPSC neurons

mrd34_ipsc_neuron_rescue

Differentiate neurons from iPSCs carrying a patient CERT1 allele and an isogenic corrected control, measure sphingolipid flux and neuronal differentiation and synaptic markers, and test whether a CERT inhibitor normalises them without impairing the control line.

Perturbations

CERT inhibition in patient-derived neurons

pathophysiology#Constitutive CERT Activation

Effect: Reduce CERT transfer activity pharmacologically.

Readouts

Sphingomyelin biosynthetic flux

pathophysiology#Increased Sphingomyelin Synthesis

Direction: RESTORED

Interpretation: Normalisation of flux in patient neurons without suppressing it below control levels would show that a therapeutic window exists in a human neural context.

Would support

pathophysiology#Constitutive CERT Activation

Supporting outcome

Patient neurons show elevated sphingomyelin flux and impaired differentiation relative to the isogenic control, and a CERT inhibitor returns both toward control values at a dose that leaves the control line unaffected.

Refuting outcome

Patient neurons show no measurable difference from the isogenic control, or the inhibitor corrects the lipid readout without affecting the neural phenotype, or no dose separates correction from toxicity in the control line.

What is the population prevalence of MRD34, and what fraction of unexplained intellectual disability does it account for?

KNOWLEDGE GAP OPEN mrd34_epidemiology_gap

Attached to

prevalence#Worldwide

Every published individual was ascertained through rare-disease referral or matchmaking, so there is no denominator. Because the phenotype is nonspecific and the causal alleles are missense rather than truncating, the disorder is exactly the kind that accumulates undiagnosed among people labelled with nonsyndromic developmental delay. A denominator would require systematic CERT1 review in an unselected sequenced intellectual-disability cohort, with mechanism-aware variant interpretation rather than a loss-of-function filter.

Are the choroid plexus and perivascular space abnormalities reported in one autopsied child a feature of CerTra syndrome, or an incidental finding?

OPEN QUESTION OPEN mrd34_choroid_plexus_finding

Attached to

pathophysiology#Abnormal Cerebral Myelination and Atrophy

The single neuropathological study of this disorder found choroid plexus epithelial disorganisation with reduced aquaporin-1, cysts and calcification, plus perivascular spaces distended with proteinaceous material, and raised the possibility of disturbed CSF dynamics and impaired perivascular clearance. That is a mechanistically attractive extension of a membrane-lipid disorder, but it rests on one case that was also complicated by sudden unexplained death in childhood, and the authors themselves state it only as a possibility. It should not be curated as a phenotype of the disorder until replicated.

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Pathophysiology

9

CERT1 Autoregulatory-Domain Missense Variant

Mechanism confidence: Established

The initiating lesion is a heterozygous missense variant in CERT1 affecting the autoregulatory apparatus of the ceramide transport protein: the serine-repeat motif serines (p.S132, p.S135, p.S138, p.S141), the nearby non-SRM residue p.G243, or the dimeric helical domain that mediates homeostatic inactivation. The variant is de novo in most reported individuals.

CERT1 hgnc:2205

Genetic context CERT1 hgnc:2205 allele_type: missense variant_origin: DE_NOVO zygosity: HETEROZYGOUS functional_impact_category: GAIN_OF_FUNCTION

Disease alleles are heterozygous missense changes that render CERT excessively active. This is a gain of function and not haploinsufficiency: a C-terminal frameshift allele (p.Pro749fs) segregated away from intellectual disability in its family and left CERT function intact in knock-in cells, so it served as a disease-matched negative control.

Downstream

Loss of Phosphorylation-Dependent CERT Autorepression Substitution of an SRM serine, or of a residue that supports SRM phosphorylation, prevents the hyperphosphorylation that normally silences CERT.

Show evidence (3 references)

PMID:36976648 SUPPORT Human Clinical

"Several variants fall into a previously uncharacterized dimeric helical domain that enables CERT homeostatic inactivation, without which sphingolipid production goes unchecked."

Establishes that the disease variants sit in the machinery that switches CERT off, which is why the variant class is the initiating lesion.

PMID:42051775 SUPPORT Human Clinical

"These variants cluster within regulatory domains essential for CERT phosphorylation and inactivation."

Independently states the regulatory-domain clustering that defines this node.

PMID:34688657 SUPPORT Human Clinical

"However, familial analysis revealed that the dupAA variant was not associated with ID, allowing us to utilize it as a disease-matched negative control for CERT1 variants that are associated with ID."

Supports restricting this node to autoregulatory-domain alleles: a C-terminal frameshift in the same gene was shown not to be causal.

Loss of Phosphorylation-Dependent CERT Autorepression

Mechanism confidence: Established

CERT is normally silenced by multisite phosphorylation of its serine-repeat motif once cellular sphingomyelin requirements are met. Disease variants shift the protein from the hyperphosphorylated form to de- or hypophosphorylated forms, so this negative-feedback brake is lost.

SRM hyperphosphorylation of CERT GO:0018105 ↓ DECREASED

Experimental models

HCT116 CERT1-knockout rescue system CELL LINE The phosphorylation-state western blot is the direct readout of this node.

Downstream

Constitutive CERT Activation Because SRM phosphorylation is what represses transport activity, its failure leaves the transporter switched on.

Show evidence (2 references)

PMID:31254361 SUPPORT Other

"The function of CERT is down-regulated by multisite phosphorylation of a serine-repeat motif (SRM) and up-regulated by phosphorylation of serine 315 in CERT."

Establishes the normal repressive role of SRM phosphorylation that disease variants abolish.

PMID:34688657 SUPPORT In Vitro

"Hyperphosphorylation of CERT's serine-repeat motif (SRM) decreases its functionality."

Confirms the direction of the regulatory relationship in the same experimental system that characterised the disease alleles.

Constitutive CERT Activation

Mechanism confidence: Established

With autorepression lost, CERT is excessively and constitutively active as a ceramide transfer protein. This is the pivotal gain-of-function state of the disorder and the node that CERT inhibitors are aimed at.

CERT-mediated ceramide transfer activity GO:0120017 ⇑ GAIN OF FUNCTION

Animal models

CERT gain-of-function Drosophila melanogaster Drosophila melanogaster recapitulates The model reproduces the excess CERT transfer activity that defines the disorder, and its phenotype is reversible by inhibiting that activity, which is the strongest available causal test of this node.

Downstream

Excess ER-to-Golgi Ceramide Transfer An unrepressed transporter moves more ceramide per unit time across the ER-Golgi membrane contact site.

Punctate Subcellular Redistribution of CERT Constitutively activated CERT variants leave the diffuse cytoplasmic and perinuclear pattern of the wild-type protein and concentrate into puncta, partly co-staining with VAP-A.

Show evidence (2 references)

PMID:33347465 SUPPORT In Vitro

"These results identified specific ID-associated CERT1 mutations that induced gain-of-function effects on CERT activity."

States the gain-of-function activity state that defines this node.

PMID:36976648 SUPPORT Human Clinical

"The clinical severity reflects the degree to which CERT autoregulation is disrupted"

Clinical severity grades with the degree of autoregulatory disruption, which is what makes the resulting excess CERT activity the operative disease state rather than an incidental in-vitro property.

Punctate Subcellular Redistribution of CERT

Mechanism confidence: Established

Activated CERT variants adopt an abnormal punctate intracellular distribution. This is a cellular correlate of the activated state rather than a demonstrated cause of downstream neural pathology, and it has been proposed as the basis of a functional assay for variant interpretation.

organelle membrane contact site GO:0044232

Show evidence (2 references)

PMID:33347465 SUPPORT In Vitro

"Amino acid replacements of S135 abnormally activated CERT and induced an intracellular punctate distribution pattern of this protein."

Couples the activated state to the punctate pattern for the S135 alleles.

PMID:34688657 SUPPORT In Vitro

"This conclusion supports our previous proposal that the intracellular punctate distribution pattern of CERT mutants may be applicable as a molecular diagnostic assay to assess whether CERT is abnormally activated by CERT1 mutations."

Records that the redistribution is being used as a readout of activation rather than as a causal step, which is why this node has no downstream edge.

Excess ER-to-Golgi Ceramide Transfer

Mechanism confidence: Established

Non-vesicular delivery of ceramide from the endoplasmic reticulum to the trans-Golgi runs above its normally regulated level.

ER-to-Golgi ceramide transport GO:0035627 ↑ INCREASED

endoplasmic reticulum membrane GO:0005789 trans-Golgi network GO:0005802

Downstream

Increased Sphingomyelin Synthesis Ceramide arriving at the trans-Golgi is the substrate for sphingomyelin synthase, so a higher delivery rate raises sphingomyelin output.

Show evidence (1 reference)

PMID:33347465 SUPPORT Other

"The ceramide transport protein (CERT) encoded by CERT1 mediates inter-organelle trafficking of ceramide for the synthesis of intracellular sphingomyelin."

Establishes the transport step that is running in excess at this node.

Increased Sphingomyelin Synthesis

Mechanism confidence: Established

Sphingomyelin production rises above the level set by cellular demand. Metabolic labelling in cells expressing S132L or G243R CERT showed significantly more labelled sphingomyelin than wild-type-rescued cells.

sphingomyelin biosynthetic process GO:0006686 ↑ INCREASED

Experimental models

HCT116 CERT1-knockout rescue system CELL LINE Metabolic labelling with radiolabelled serine quantifies sphingomyelin output for each allele.

Downstream

Dysregulated Sphingolipid Homeostasis Sphingomyelin production that is no longer matched to demand is what breaks homeostatic control of the sphingolipid pool.

Show evidence (1 reference)

PMID:34688657 SUPPORT In Vitro

"When the mutant CERT S132L or G243R constructs were expressed, the levels of labeled SM were significantly higher than those observed in the WT CERT rescued cells"

Direct metabolic-labelling measurement of the increased output for two disease alleles.

Dysregulated Sphingolipid Homeostasis

Mechanism confidence: Established

The feedback loop that matches sphingolipid biosynthetic flux to cellular requirement is broken, so the sphingolipid composition of membranes is set by an unregulated transporter rather than by demand.

sphingolipid metabolic process GO:0006665 ↕ DYSREGULATED

Downstream

Impaired Neural Differentiation and Synaptic Membrane Function Membrane sphingolipids are required for neural differentiation, synaptic transmission and action potential propagation, so loss of homeostatic control of the pool is taken to compromise those processes. The intermediate steps and the vulnerable human neural cell type have not been identified.

Facial dysmorphism The mild facial and distal limb features are placed downstream of the systemic sphingolipid lesion rather than of the neural node, since they are morphogenetic rather than neurological. No mechanism connecting sphingolipid flux to these structures has been demonstrated.

Digit, hand and foot anomalies Placed downstream of the systemic sphingolipid lesion rather than of the neural node, on the same reasoning as the facial features they accompany: they are morphogenetic rather than neurological. No mechanism connecting sphingolipid flux to limb patterning has been demonstrated.

Show evidence (2 references)

PMID:36976648 SUPPORT Human Clinical

"These findings uncover a central role for CERT autoregulation in the control of sphingolipid biosynthetic flux, provide unexpected insight into the structural organization of CERT, and suggest a possible therapeutic approach for patients with CerTra syndrome."

Names control of sphingolipid biosynthetic flux as the function that CERT autoregulation serves and that is lost here.

PMID:42051775 SUPPORT Human Clinical

"These variants disrupt ceramide transport and sphingolipid homeostasis, leading to a clinical phenotype that includes developmental delay, movement abnormalities, and structural brain anomalies."

Independent statement that disrupted sphingolipid homeostasis is the state that connects the molecular lesion to the clinical phenotype.

Impaired Neural Differentiation and Synaptic Membrane Function

Mechanism confidence: Provisional

Altered sphingolipid flux in the developing nervous system is inferred to compromise neural differentiation, membrane composition and synaptic function, producing the cognitive, motor, language and behavioural phenotype. This is the least well characterised step of the chain: no patient neural tissue, iPSC-neuron or organoid study has identified the primary vulnerable cell type.

neuron CL:0000540

nervous system development GO:0007399 ⚠ ABNORMAL

brain UBERON:0000955

Animal models

CERT gain-of-function Drosophila melanogaster Drosophila melanogaster partially recapitulates The model reproduces motor and morphological consequences of the lipid lesion, which is the closest available proxy for the human neurodevelopmental node.

Downstream

Abnormal Cerebral Myelination and Atrophy A subset of affected individuals develop white-matter and atrophic changes on MRI, which are attributed to the same disturbance of neural lipid biology. The link rests on human imaging rather than on a demonstrated mechanism.

Global developmental delay

Intellectual disability

Delayed speech and language development

Motor delay

Infantile hypotonia

Atypical behavior

Autism spectrum disorder

Stereotypical hand movements

Self-injurious behavior

Sleep disturbance

Attention deficit hyperactivity disorder

Aggressive behavior

Seizures

Impaired pain sensation

Feeding difficulties

Show evidence (2 references)

PMID:42051775 SUPPORT Human Clinical

"Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability (3). Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."

Enumerates the neurodevelopmental manifestations that this node is asserted to produce.

PMID:36976648 SUPPORT Human Clinical

"Mutations in the ceramide transporter CERT (CERT1), which is involved in sphingolipid biosynthesis, are associated with intellectual disability, but the pathogenic mechanism remains obscure."

Records both the association with intellectual disability and the authors' own statement that the pathogenic mechanism at this level is unresolved, which is why the node is marked PROVISIONAL.

Abnormal Cerebral Myelination and Atrophy

Mechanism confidence: Provisional

A subset of affected individuals show thin corpus callosum, ventriculomegaly, delayed myelination and cerebellar atrophy on brain MRI. In one autopsied child, choroid plexus epithelial disorganisation with reduced aquaporin-1, cysts and calcification, and perivascular spaces distended with proteinaceous material were also found.

oligodendrocyte CL:0000128

myelination GO:0042552 ⚠ ABNORMAL

corpus callosum UBERON:0002336 cerebellum UBERON:0002037

Downstream

Thin corpus callosum

Delayed myelination

Ventriculomegaly

Cerebellar atrophy

Show evidence (2 references)

PMID:42051775 SUPPORT Human Clinical

"In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."

Enumerates the structural brain findings that constitute this node.

PMID:42051775 SUPPORT Human Clinical

"Neuropathological examination demonstrated marked ChP epithelial disorganization, reduced aquaporin-1 (AQP1) expression, cyst formation, and focal calcifications, which may be associated with disturbances in cerebrospinal fluid (CSF) dynamics."

Adds the single available neuropathological characterisation; the hedged wording is why the node is PROVISIONAL rather than ESTABLISHED.

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Pathograph

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

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Phenotypes

22

Digestive 1

Feeding difficulties FREQUENT HP:0011968

Onset: NEONATAL

Sequelae: Failure to thrive

Show evidence (2 references)

PMID:36976648 SUPPORT Human Clinical

"Fifteen (of 24) patients had neonatal feeding difficulties, often with hypotonia or failure to thrive."

Gives the denominator behind the FREQUENT band, 15 of 24, and dates the onset to the neonatal period.

PMID:42051775 SUPPORT Human Clinical

"Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."

Lists feeding difficulties among the clinical features of the disorder.

Head and Neck 1

Facial dysmorphism Abnormal facial shape HP:0001999

Show evidence (2 references)

PMID:36976648 SUPPORT Human Clinical

"Subtle facial dysmorphisms included anteverted nares with a depressed or broad nasal bridge, enlarged earlobes, synophrys, micrognathia, dental anomalies (protruding incisors and diastema), and palatine ridges"

Enumerates the facial features recorded by the cohort's blinded dysmorphology analysis.

PMID:36976648 SUPPORT Human Clinical

"These patients have a syndromic presentation characterized by infantile hypotonia; mild dysmorphologies (affecting the face, hands or feet)"

Places the dysmorphism in the cohort's own summary of the syndromic presentation and records that it is mild.

Limbs 1

Digit, hand and foot anomalies Abnormal digit morphology HP:0011297

Show evidence (1 reference)

PMID:36976648 SUPPORT Human Clinical

"Anomalies affecting the hands, feet, or digits included third/fourth finger syndactyly, club foot, or hallux varus (sandal gaps)"

Enumerates the reported hand, foot and digit anomalies. The bound term covers the digital findings; club foot is a foot rather than a digit anomaly and is carried in the description rather than by the binding.

Musculoskeletal 1

Infantile hypotonia HP:0001252

Onset: INFANTILE

Show evidence (1 reference)

PMID:42051775 SUPPORT Human Clinical

"Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"

States infantile hypotonia as a core manifestation.

Nervous System 17

Global developmental delay VERY_FREQUENT HP:0001263

Show evidence (3 references)

PMID:36976648 SUPPORT Human Clinical

"only 4 of the individuals did not show some form of developmental delay by the end of the first year of life (4 of 26, 15%)"

Gives the denominator behind the VERY_FREQUENT band: 22 of 26 patients had some form of developmental delay by the end of the first year, stated as the complementary 4 of 26 who did not.

PMID:42051775 SUPPORT Human Clinical

"Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"

Lists global developmental delay among the core manifestations of the CERT1-related disorder.

PMID:42051775 SUPPORT Human Clinical

"Her developmental course was notable for global delay affecting both cognitive and motor domains."

Individual-level confirmation in a molecularly confirmed case.

Intellectual disability HP:0001249

Show evidence (4 references)

PMID:42051775 SUPPORT Human Clinical

"Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"

Lists intellectual disability of varying degree among the core features.

PMID:33347465 SUPPORT Human Clinical

"Utilizing whole exome sequencing analysis, we identified a novel CERT variant, which substitutes a serine at position 135 (S135) for a proline in a patient with severe ID."

A molecularly defined case at the severe end of the reported range.

PMID:34688657 SUPPORT INDIRECT Human Clinical

"The Wechsler Intelligence Scale for Children – Fifth Edition showed a full scale composite score of 55, which was consistent with a mild ID"

A formally measured mild end of the range, in the proband of the Tamura report. Note this proband's CERT1 allele was subsequently judged non-causative, so the measurement bounds the reported spectrum of the referral population rather than of confirmed MRD34.

+ 1 more reference

Motor delay VERY_FREQUENT HP:0001270

Show evidence (2 references)

PMID:36976648 SUPPORT Human Clinical

"These were likely early manifestations of what would later become frank motor delays, affecting 26 of 29 patients"

The denominator behind the VERY_FREQUENT band, and the observation that motor delay is prefigured by the neonatal feeding and tone problems.

PMID:42051775 SUPPORT Human Clinical

"Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"

Lists motor delay among the core manifestations.

Delayed speech and language development HP:0000750

Show evidence (3 references)

PMID:42051775 SUPPORT Human Clinical

"Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."

Lists speech delay among the additional clinical features of the disorder.

PMID:42051775 SUPPORT Human Clinical

"She was non-verbal and had chronic sleep disturbance."

Documents the severe end of the language phenotype in a molecularly confirmed case.

PMID:34688657 SUPPORT INDIRECT Human Clinical

"he presented with speech delay with a limited number of words and no phrasing"

A clinical description of the speech phenotype in a proband referred for CERT1 evaluation.

Atypical behavior HP:0000708

Show evidence (3 references)

PMID:36976648 SUPPORT Human Clinical

"Neurobehavioral abnormalities frequently led to a diagnosis of autism spectrum disorder (ASD) (19 of 27, 70%); some patients displayed stereotypical hand movements (14 of 18), self-injurious behavior (9 of 19), high pain tolerance (9 of 18), disrupted sleep patterns (9 of 21), attention..."

The single cohort sentence that enumerates the component behaviours and their denominators; each is also curated as its own phenotype.

PMID:42051775 SUPPORT Human Clinical

"Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."

Lists behavioural abnormalities among the clinical features.

PMID:34688657 SUPPORT INDIRECT Human Clinical

"He had a behavioral disorder that frequently shifted from one activity to another and exhibited recurrent mannerisms, such as repeatedly putting his hand to his mouth."

An individual-level description of the stereotypic and attentional behaviour seen in this referral population.

Autism spectrum disorder FREQUENT HP:0000717

Show evidence (3 references)

PMID:36976648 SUPPORT Human Clinical

"Neurobehavioral abnormalities frequently led to a diagnosis of autism spectrum disorder (ASD) (19 of 27, 70%)"

The cohort denominator behind the FREQUENT band, 19 of 27 assessed patients.

PMID:36976648 REFUTE Human Clinical

"indicates that CERT1 variants are unlikely to be a significant contributor to autism but instead cause a recognizable neurodevelopmental syndrome distinct from ASD, which we will refer to as CerTra syndrome."

Refutes any reading of this phenotype as making MRD34 an autism entity or CERT1 an autism gene; the same authors reach the opposite conclusion from SPARK and denovo-db and name the disorder as distinct from ASD.

PMID:36976648 REFUTE Human Clinical

"none of the individuals in our cohort was diagnosed with ASD as a primary condition"

Refutes reading ASD as the presenting or primary condition. In every cohort member it was a comorbid behavioural diagnosis reached alongside the developmental phenotype.

Stereotypical hand movements FREQUENT Motor stereotypy HP:0000733

Show evidence (1 reference)

PMID:36976648 SUPPORT Human Clinical

"some patients displayed stereotypical hand movements (14 of 18)"

The cohort denominator behind the FREQUENT band, 14 of 18 assessed patients.

Self-injurious behavior FREQUENT HP:0100716

Show evidence (1 reference)

PMID:36976648 SUPPORT Human Clinical

"some patients displayed stereotypical hand movements (14 of 18), self-injurious behavior (9 of 19)"

The cohort denominator behind the FREQUENT band, 9 of 19 assessed patients.

Sleep disturbance FREQUENT HP:0002360

Show evidence (1 reference)

PMID:36976648 SUPPORT Human Clinical

"high pain tolerance (9 of 18), disrupted sleep patterns (9 of 21)"

The cohort denominator behind the FREQUENT band, 9 of 21 assessed patients.

Attention deficit hyperactivity disorder FREQUENT HP:0007018

Show evidence (1 reference)

PMID:36976648 SUPPORT Human Clinical

"disrupted sleep patterns (9 of 21), attention deficit–hyperactivity disorder (10 of 19)"

The cohort denominator behind the FREQUENT band, 10 of 19 assessed patients.

Aggressive behavior FREQUENT HP:0000718

Show evidence (1 reference)

PMID:36976648 SUPPORT Human Clinical

"disrupted sleep patterns (9 of 21), attention deficit–hyperactivity disorder (10 of 19), or aggression (6 of 20)."

The cohort denominator behind the FREQUENT band, 6 of 20 assessed patients, which sits at the lower edge of that band.

Impaired pain sensation FREQUENT HP:0007328

Show evidence (2 references)

PMID:36976648 SUPPORT Human Clinical

"self-injurious behavior (9 of 19), high pain tolerance (9 of 18)"

Gives the denominator behind the FREQUENT band, 9 of 18 assessed patients.

PMID:42051775 SUPPORT Human Clinical

"Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."

Lists high pain tolerance among the clinical features of the disorder.

Seizures FREQUENT HP:0001250

Show evidence (3 references)

PMID:36976648 SUPPORT Human Clinical

"Multiple seizure types were reported (16 of 29)."

Gives the denominator behind the FREQUENT band, 16 of 29, and records that seizure type varied rather than following one syndromic pattern.

PMID:42051775 SUPPORT Human Clinical

"Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."

Lists seizures among the clinical features of the disorder.

PMID:42051775 REFUTE Human Clinical

"no epilepsy or other neurological disorder has been diagnosed for this case"

A molecularly confirmed individual without epilepsy, which refutes any reading of seizures as an obligate feature.

Thin corpus callosum HP:0033725

Show evidence (2 references)

PMID:42051775 SUPPORT Human Clinical

"In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."

Names thin corpus callosum among the commonly reported neuroimaging findings.

PMID:36976648 SUPPORT Human Clinical

"Neuroimaging frequently revealed a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy"

The primary cohort statement of the neuroimaging findings, cited directly rather than through the secondary report that summarises it.

Ventriculomegaly HP:0002119

Show evidence (2 references)

PMID:42051775 SUPPORT Human Clinical

"In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."

Names ventriculomegaly among the commonly reported neuroimaging findings.

PMID:36976648 SUPPORT Human Clinical

"Neuroimaging frequently revealed a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy"

The primary cohort statement of the neuroimaging findings, cited directly rather than through the secondary report that summarises it.

Delayed myelination HP:0012448

Show evidence (2 references)

PMID:42051775 SUPPORT Human Clinical

"In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."

Names delayed myelination among the commonly reported neuroimaging findings.

PMID:36976648 SUPPORT Human Clinical

"Neuroimaging frequently revealed a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy"

The primary cohort statement of the neuroimaging findings, cited directly rather than through the secondary report that summarises it.

Cerebellar atrophy HP:0001272

Show evidence (2 references)

PMID:42051775 SUPPORT Human Clinical

"In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."

Names cerebellar atrophy among the commonly reported neuroimaging findings.

PMID:36976648 SUPPORT Human Clinical

"Neuroimaging frequently revealed a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy"

The primary cohort statement of the neuroimaging findings, cited directly rather than through the secondary report that summarises it.

Growth 1

Failure to thrive HP:0001508

Show evidence (1 reference)

PMID:36976648 SUPPORT Human Clinical

"Fifteen (of 24) patients had neonatal feeding difficulties, often with hypotonia or failure to thrive."

Names failure to thrive as a frequent accompaniment of the neonatal feeding difficulty. No separate denominator is reported for failure to thrive itself, so no frequency band is recorded here.

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Genetic Associations

1

CERT1 Gain-of-Function Missense Variants (Causative)

Gene: CERT1 hgnc:2205 relationship_type: CAUSATIVE variant_origin: GERMLINE

Autosomal dominant inheritance

Show evidence (8 references)

PMID:36976648 SUPPORT Human Clinical

"Here, we characterize 31 individuals with de novo missense variants in CERT1."

The cohort that established CERT1 as the causal gene and defined the allele class as de novo missense.

PMID:33347465 SUPPORT In Vitro

"These results identified specific ID-associated CERT1 mutations that induced gain-of-function effects on CERT activity."

Functional evidence that the disease alleles act by gain of function rather than by loss.

PMID:34688657 SUPPORT Human Clinical

"The Gene Nomenclature Committee of the Human Genome Organization revised the official symbol of the gene from COL4A3BP to CERT1 in 2019"

Documents the gene symbol change that splits this disorder's literature between two names.

+ 5 more references

💊

Medical Actions

7

Symptom-Directed Supportive Care

Category: Therapeutic Action: Supportive Care NCIT:C15747

There is no disease-modifying therapy. Management is individualised and directed at the manifestations: early developmental and educational intervention, feeding and nutritional support, behavioural and sleep support, and surveillance of growth, vision, hearing and orthopaedic status.

Target Phenotypes: Global developmental delay HP:0001263 Feeding difficulties HP:0011968

Show evidence (1 reference)

PMID:42051775 SUPPORT INDIRECT Human Clinical

"Despite growing recognition of this condition, detailed neuroimaging and neuropathological characterization remain limited."

Supports the absence of a disease-specific evidence base; management is necessarily supportive and generic to the manifestations.

Physical Therapy

Category: Therapeutic Action: Physical Therapy NCIT:C15302

Platform: Behavioral / lifestyle

Gross-motor rehabilitation for the hypotonia and motor delay, including mobility equipment and contracture prevention where walking is not attained.

Target Phenotypes: Motor delay HP:0001270 Infantile hypotonia HP:0001252

Show evidence (1 reference)

PMID:42051775 SUPPORT INDIRECT Human Clinical

"Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"

Establishes the motor impairments that motor rehabilitation addresses. No trial evidence in this disorder exists.

Occupational Therapy

Category: Therapeutic Action: Occupational Therapy NCIT:C121351

Platform: Behavioral / lifestyle

Fine-motor and daily-living-skills intervention, and adaptive equipment, addressing the same hypotonia and global developmental delay from the functional-independence side rather than the mobility side.

Target Phenotypes: Global developmental delay HP:0001263 Infantile hypotonia HP:0001252

Show evidence (1 reference)

PMID:42051775 SUPPORT INDIRECT Human Clinical

"Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"

Establishes the developmental and tone impairments that occupational therapy addresses. No trial evidence in this disorder exists.

Speech and Language Therapy

Category: Therapeutic Action: Speech Language Therapy NCIT:C159273

Platform: Behavioral / lifestyle

Speech-language intervention and augmentative or alternative communication, which is the relevant modality for the substantial minority who remain non-verbal.

Target Phenotypes: Delayed speech and language development HP:0000750

Show evidence (1 reference)

PMID:42051775 SUPPORT INDIRECT Human Clinical

"Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."

Establishes the speech impairment this intervention addresses. No trial evidence in this disorder exists.

Antiseizure Pharmacotherapy

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: anticonvulsant agent NCIT:C264

Platform: Small molecule

Standard antiseizure medication selected by seizure type for the subset with epilepsy. No disorder-specific drug choice or pharmacogenomic algorithm has been established.

Target Phenotypes: Seizure HP:0001250

Show evidence (1 reference)

PMID:42051775 SUPPORT INDIRECT Human Clinical

"Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."

Establishes seizures as a manifestation requiring standard antiseizure treatment. No disorder-specific efficacy data exist.

Genetic Counseling

Category: Counseling / Informational Action: Genetic Counseling NCIT:C15240

Counselling covers the dominant mechanism, the predominance of de novo origin, the residual recurrence risk from parental gonadal mosaicism after an apparently de novo result, and the availability of cascade or prenatal testing once a familial pathogenic allele is confirmed.

Show evidence (1 reference)

PMID:42051775 SUPPORT Human Clinical

"In CerTra syndrome, most pathogenic variants arise de novo and are heterozygous."

The de novo dominant mechanism is the fact that determines the recurrence risk counselling for this disorder.

Pharmacological CERT Inhibition

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Platform: Small molecule

Preclinical only. The CERT inhibitor HPA-12 corrects morphological and motor abnormalities in the Drosophila model, and a 2024 live-cell NanoBRET screen of 140 HPA-12 derivatives identified six compounds outperforming the parent compound. There is no human dosing, safety, CNS penetration or developmental-toxicity evidence, and because CERT is required for normal membrane lipid homeostasis, over-inhibition is itself a plausible harm.

Mechanism Target:

Constitutive CERT Activation — The proposed therapeutic node: an inhibitor reduces the excess transfer activity that the disease variants create.

Show evidence (1 reference)

PMID:36976648 SUPPORT Model Organism

"inhibiting CERT pharmacologically corrects morphological and motor abnormalities in a Drosophila model of the disease, which we call ceramide transporter (CerTra) syndrome."

Pharmacological inhibition of the activated transporter reverses the model phenotype, which is the target-validation evidence for this link.

Show evidence (2 references)

PMID:39450584 SUPPORT In Vitro

"The utility of the method was demonstrated by a library of 140 derivatives of the CERT inhibitor HPA-12. These were obtained in a combinatorial synthesis using solid-phase transacylation. Screening of the library led to six compounds that were picked and confirmed to be superior to HPA-12 in a..."

Documents the current state of CERT inhibitor development: a cell-based screening platform and improved chemical matter, with no patient exposure.

PMID:39450584 SUPPORT In Vitro

"CERT is considered a promising drug target but no direct cell-based methods exist to efficiently identify inhibitors."

Frames CERT inhibition as a drug-discovery programme rather than an available therapy.

🔬

Diagnosis

3

CERT1 Molecular Genetic Confirmation

Diagnosis rests on identifying a heterozygous pathogenic CERT1 variant in an individual with a compatible neurodevelopmental phenotype. Trio exome or genome sequencing is the informative test because most alleles are de novo, and the report should state the transcript accession: the same allele is numbered differently under the 598-residue and 624-residue CERT isoforms.

trio exome sequencing NCIT:C101295

Results: A heterozygous pathogenic CERT1 variant, interpreted against ACMG/AMP criteria with attention to de novo status, absence from population databases, clustering in the autoregulatory domains, and available functional data.

Show evidence (3 references)

PMID:42051775 SUPPORT Human Clinical

"Trio exome sequencing was conducted in the proband and both biological parents to investigate potential monogenic causes contributing to the patient's neurodevelopmental phenotype and sudden death."

Documents the trio sequencing route actually used to reach the molecular diagnosis in a reported case.

PMID:42051775 SUPPORT Human Clinical

"The genetic analysis identified a heterozygous de novo missense variant in the CERT1 gene (p. Ser260Leu; S260L). This variant was classified as pathogenic by the testing laboratory based on ACMG criteria."

Shows the diagnostic endpoint: a heterozygous de novo CERT1 missense allele classified as pathogenic under ACMG criteria.

PMID:33347465 SUPPORT Human Clinical

"Utilizing whole exome sequencing analysis, we identified a novel CERT variant, which substitutes a serine at position 135 (S135) for a proline in a patient with severe ID."

Exome sequencing as the route to the molecular diagnosis in the index S135P case.

Functional Assay of CERT Activation for Variant Interpretation

Because pathogenicity here is a gain-of-function property rather than a truncation, a CERT1 variant of uncertain significance can be triaged by functional testing: loss of SRM hyperphosphorylation on western blot, increased metabolic labelling of sphingomyelin, and a punctate rather than diffuse subcellular distribution of tagged CERT. This is a research-level assay, not a clinically validated test.

cellular CERT activation and localization assay

Results: Loss of the hyperphosphorylated CERT band, elevated labelled sphingomyelin relative to wild-type rescue, and punctate CERT distribution together indicate an activating allele.

Research-level only. No clinical laboratory offers this assay and no performance characteristics have been published.

Show evidence (2 references)

PMID:34688657 SUPPORT In Vitro

"This conclusion supports our previous proposal that the intracellular punctate distribution pattern of CERT mutants may be applicable as a molecular diagnostic assay to assess whether CERT is abnormally activated by CERT1 mutations."

The authors explicitly propose the localisation pattern as a variant interpretation assay.

PMID:33347465 SUPPORT In Vitro

"These findings provide a possible molecular basis for not only new diagnostics but also a conceivable pharmaceutical intervention for ID disorders caused by gain-of-function mutations in CERT1."

States the diagnostic application of the gain-of-function characterisation.

Routine Biochemical Screening (Negative)

Standard metabolic workup is performed in the diagnostic approach to unexplained developmental disability and is normal in this disorder. It has no positive diagnostic value here; its role is to exclude the treatable inborn errors that share the presentation. No blood, urine, enzyme or CSF biomarker of MRD34 is validated.

routine metabolic screening panel

Results: Serum ammonia and lactate, thyroid and liver function, blood gases, serum amino acids, tandem mass spectrometry and urine organic acids are within normal limits.

Show evidence (1 reference)

PMID:34688657 SUPPORT Human Clinical

"Metabolic tests, including measurement of serum ammonia and lactate levels, thyroid and liver function tests, blood gas analysis, serum amino acid chromatography, MS/MS, and the urine organic acid profile were applied. However, all results were within normal limits."

Documents the normal routine biochemical screen in an investigated proband, which is the basis for recording this panel as negative in this disorder.

📊

Prevalence

1

Worldwide

Cases In Literature Not yet documented

No population-based prevalence or incidence estimate exists. The largest published delineation is an international series of 31 unrelated individuals ascertained through rare-disease referral and matchmaking, which has no population denominator, and MONDO records no Orphanet cross-reference from which an Orphanet prevalence class could be taken. The literature case count is recorded here rather than a rate; do not read NOT_YET_DOCUMENTED as a claim that the disorder is vanishingly rare, since ascertainment through nonspecific developmental delay is likely incomplete.

Show evidence (2 references)

PMID:36976648 SUPPORT Human Clinical

"Here, we characterize 31 individuals with de novo missense variants in CERT1."

Establishes the size of the largest reported case series, which is the only occurrence figure available for this disorder.

PMID:42051775 SUPPORT Human Clinical

"Due to the limited number of reported cases and the rarity of CerTra syndrome, the neuroimaging features associated with this condition remain insufficiently characterized, and definitive conclusions have yet to be established."

Confirms that the reported case count remains small enough that even descriptive features are not yet settled, let alone population rates.

🔀

Differential Diagnoses

1

Conditions with similar clinical presentations that must be differentiated from Intellectual Disability Autosomal Dominant 34:

Other monogenic autism-intellectual disability syndromes

Overlapping Features The clinical picture is not distinctive enough to identify CERT1 without sequencing. The combination that should raise CERT1 specifically is intellectual disability with disproportionately severe speech and motor delay, infantile hypotonia, autistic or stereotypic behaviour, high pain tolerance, feeding and growth problems, and a thin corpus callosum or delayed myelination on MRI.

Distinguishing Features

Only molecular testing distinguishes them; there is no pathognomonic clinical gestalt.
Interpretation must be mechanism-aware: a truncating CERT1 allele does not support the diagnosis, because the disorder is caused by gain of function.

Show evidence (1 reference)

PMID:30878996 SUPPORT INDIRECT Other

"We have previously proposed the term "Golgipathies" in relation to a group of disorders in which mutations in GA proteins or their molecular partners lead to consequences for brain development, in particular postnatal-onset microcephaly (POM), white-matter defects, and intellectual disability (ID)."

Places MRD34 in the wider set of disorders in which a Golgi-apparatus or Golgi-associated protein lesion produces intellectual disability and white-matter change. That set is the nosological neighbourhood a CERT1 variant has to be distinguished from, which is what this differential records; the review names COL4A3BP among its examples.

🧫

Experimental Models

1

HCT116 CERT1-knockout rescue system CELL_LINE

A human colon carcinoma line in which both CERT1 alleles are disrupted, then stably complemented with tagged wild-type or variant CERT. This is the platform on which the gain-of-function mechanism was established: CERT phosphorylation state by western blot, sphingomyelin output by metabolic labelling and lysenin sensitivity, and subcellular localisation by immunofluorescence, each read against wild-type rescue and against the non-causative p.Pro749fs allele.

Organism

human NCBITaxon:9606

Publication

PMID:34688657

Pathograph links

Loss of Phosphorylation-Dependent CERT Autorepression measures fidelity: moderate observes: molecular The phosphorylation-state western blot is the direct readout of this node.

Limitations: A colon carcinoma line is not a neural cell, and the variant CERT is expressed ectopically against a null background rather than heterozygously alongside a wild-type allele as in patients.

Readouts

Hyperphosphorylated versus de/hypophosphorylated CERT

Direction: DECREASED

Interpretation: Disease alleles shift CERT out of the hyperphosphorylated form, which is the loss of autorepression itself.

Show evidence (1 reference)

PMID:34688657 SUPPORT In Vitro

"Biochemical analysis showed that G243R and S132L, but not dupAA, impair SRM hyperphosphorylation and render the CERT variants excessively active."

Reports the phosphorylation measurement for two disease alleles against a negative control allele.

Increased Sphingomyelin Synthesis measures fidelity: moderate observes: molecular Metabolic labelling with radiolabelled serine quantifies sphingomyelin output for each allele.

Limitations: Bulk whole-cell sphingolipid levels did not differ significantly between variant and wild-type rescue in this system, so the assay reports biosynthetic flux rather than steady-state composition.

Readouts

Metabolically labelled sphingomyelin

Direction: INCREASED

Interpretation: Higher labelled sphingomyelin in variant-expressing cells than in wild-type-rescued cells is the quantitative form of the node.

Show evidence (1 reference)

PMID:34688657 SUPPORT In Vitro

"When the mutant CERT S132L or G243R constructs were expressed, the levels of labeled SM were significantly higher than those observed in the WT CERT rescued cells"

The direct measurement of increased sphingomyelin synthesis.

Show evidence (1 reference)

PMID:34688657 SUPPORT In Vitro

"we infer that the majority of ID-associated CERT variants may impair SRM phosphorylation-dependent repression, resulting in an increase in sphingomyelin production concurrent with CERT subcellular redistribution."

Summarises what this system established about the disease alleles, which is why it is treated as informative for these nodes.

🐁

Animal Models

1

CERT gain-of-function Drosophila melanogaster Genetic

A Drosophila model expressing gain-of-function CERT, reported in the cohort paper as reproducing morphological and motor abnormalities that are corrected by pharmacological CERT inhibition. It is the only in vivo model of the disorder; no knock-in mouse, rat or zebrafish model was found.

Species

Drosophila melanogaster

Genotype

CERT gain-of-function

Publication

PMID:36976648

Pathograph links

Constitutive CERT Activation recapitulates fidelity: moderate observes: organism The model reproduces the excess CERT transfer activity that defines the disorder, and its phenotype is reversible by inhibiting that activity, which is the strongest available causal test of this node.

Limitations: CERT-mediated ceramide transport is conserved, but the fly differs from human in brain architecture, developmental timing, sphingolipid composition and drug metabolism, so the quantitative relationship between degree of CERT activation and phenotype is not transferable.

Readouts

Morphological and motor abnormalities after CERT inhibition

Direction: RESTORED

Interpretation: Correction of the model phenotype by a CERT inhibitor is the readout that ties the phenotype to excess CERT activity rather than to some other consequence of the transgene.

Show evidence (1 reference)

PMID:36976648 SUPPORT Model Organism

"inhibiting CERT pharmacologically corrects morphological and motor abnormalities in a Drosophila model of the disease, which we call ceramide transporter (CerTra) syndrome."

Reports the measurement: model abnormalities corrected by pharmacological CERT inhibition.

Head size after larval HPA-12 feeding

Direction: RESTORED

Interpretation: The specific morphological measure behind the rescue. Head size is reduced by the extra dCERT copies and returns to control values when larvae are fed the CERT inhibitor, which is what makes the head phenotype attributable to CERT activity rather than to the transgene.

Show evidence (1 reference)

PMID:36976648 SUPPORT Model Organism

"Feeding HPA-12 to +WT and +SL larvae (see Supplemental Methods) restored head size, suggesting that increased dCERT activity was responsible for this phenotype"

Reports the head-size measurement and its restoration by HPA-12, the same inhibitor class as the treatment linked to this node.

Locomotor activity after HPA-12 pretreatment

Direction: RESTORED

Interpretation: The motor half of the rescue. Transgenic flies are hypoactive relative to controls and inhibitor pretreatment restores activity without affecting control flies, so the effect requires the excess CERT activity rather than being a general drug effect.

Show evidence (2 references)

PMID:36976648 SUPPORT Model Organism

"Both +WT and +SL flies showed locomotor hypoactivity compared with Ctrl flies"

Establishes the baseline locomotor deficit that the inhibitor arm reverses.

+ 1 more reference

Impaired Neural Differentiation and Synaptic Membrane Function partially recapitulates fidelity: low observes: organism The model reproduces motor and morphological consequences of the lipid lesion, which is the closest available proxy for the human neurodevelopmental node.

Limitations: The fly cannot model the defining human manifestations of this node - intellectual disability, language, adaptive behaviour - and the reported phenotype is motor and morphological, so the correspondence to the human node is partial by construction.

Divergences from the human mechanism

species mismatch qualifying

Drosophila neural development lacks the cortical expansion, myelinating oligodendrocyte biology and language circuitry through which the human node is expressed, so its motor and morphological output is a distant proxy for the human phenotype.

proxy quantity qualifying

The measured quantities are fly locomotor activity and head or brain morphology. The node's quantities are human neural differentiation and synaptic membrane function, neither of which the model measures.

Show evidence (1 reference)

PMID:36976648 SUPPORT Model Organism

"inhibiting CERT pharmacologically corrects morphological and motor abnormalities in a Drosophila model of the disease, which we call ceramide transporter (CerTra) syndrome."

Establishes the existence of the Drosophila disease model and its pharmacological rescue.

{ }

Source YAML

click to show

name: Intellectual Disability Autosomal Dominant 34
creation_date: "2026-09-04T02:26:58Z"
category: Mendelian
synonyms:
- MRD34
- intellectual disability, autosomal dominant 34
- autosomal dominant intellectual disability 34
- intellectual developmental disorder, autosomal dominant 34
- CERT1-related neurodevelopmental disorder
- ceramide transporter syndrome
- CerTra syndrome
- COL4A3BP autosomal dominant non-syndromic intellectual disability
description: >-
  Intellectual disability, autosomal dominant 34 (MRD34) is an ultra-rare
  Mendelian neurodevelopmental disorder caused by heterozygous, usually de novo,
  missense variants in CERT1 (formerly COL4A3BP), the gene encoding the ceramide
  transport protein CERT. The expanded phenotype delineated in a 31-person
  international cohort is now also called ceramide transporter (CerTra)
  syndrome. CERT moves ceramide from the endoplasmic reticulum to the
  trans-Golgi at ER-Golgi membrane contact sites, where it is converted to
  sphingomyelin; its activity is normally switched off by multisite
  hyperphosphorylation of a serine-repeat motif (SRM) once cellular sphingomyelin
  demand is met. The disease alleles cluster in that autoregulatory machinery -
  the SRM serines (p.S132, p.S135, p.S138, p.S141), a nearby non-SRM residue
  (p.G243), and a dimeric helical domain characterised in 2023 - and block the
  inactivating hyperphosphorylation, leaving CERT constitutively active. The
  mechanism is therefore gain of function, not haploinsufficiency, and a rare
  CERT1 variant is not by itself diagnostic: a C-terminal frameshift
  (p.Pro749fs) segregated away from disease and behaved as a functional negative
  control. Constitutively active CERT redistributes into cytoplasmic puncta and
  drives excess sphingomyelin synthesis. Clinically the disorder presents with
  infantile hypotonia, global developmental delay, motor and speech delay,
  intellectual disability of mild to profound degree, autism and other
  behavioural abnormalities, high pain tolerance, feeding difficulties, and
  seizures, with thin corpus callosum, ventriculomegaly, delayed myelination and
  cerebellar atrophy reported on neuroimaging. Management is entirely
  supportive; pharmacological CERT inhibition rescues the Drosophila model but
  has never been tested in patients.
disease_term:
  preferred_term: intellectual disability, autosomal dominant 34
  term:
    id: MONDO:0014599
    label: intellectual disability, autosomal dominant 34
parents:
- autosomal dominant non-syndromic intellectual disability
references:
- reference: PMID:36976648
  title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
- reference: PMID:33347465
  title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
- reference: PMID:34688657
  title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
- reference: PMID:31254361
  title: "Structure, functions and regulation of CERT, a lipid-transfer protein for the delivery of ceramide at the ER-Golgi membrane contact sites."
- reference: PMID:25356899
  title: "De novo mutations in moderate or severe intellectual disability."
- reference: PMID:42051775
  title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
- reference: PMID:39450584
  title: "Live-Cell Identification of Inhibitors of the Lipid Transfer Protein CERT Using Nanoluciferase Bioluminescence Resonance Energy Transfer (NanoBRET)."
- reference: PMID:30878996
  title: "Golgipathies in Neurodevelopment: A New View of Old Defects."
inheritance:
- name: Autosomal dominant inheritance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    MRD34 is autosomal dominant and is caused by a heterozygous CERT1 variant
    that is de novo in the great majority of molecularly characterised
    individuals: 25 of the 27 patients with biparental samples in the defining
    cohort. Penetrance is recorded as INCOMPLETE on a narrow basis. One variant
    in the FFAT-motif cluster, p.V326F, was inherited from a reportedly
    unaffected father; a second inherited allele, p.A449V, came from a mother
    with intellectual disability that the authors judged independent of her
    CERT1 genotype, and they separately doubt whether that allele is pathogenic.
    So the evidence for reduced penetrance is one family, not a series.
  penetrance: INCOMPLETE
  expressivity: VARIABLE
  de_novo_rate: 93% (25 of 27 patients with biparental samples in the defining cohort)
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we characterize 31 individuals with de novo missense variants in CERT1."
    explanation: >-
      The defining cohort establishes that the disorder arises from heterozygous
      de novo missense alleles, which is the autosomal dominant pattern.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Family segregation confirmed that CERT1 variants occurred de novo in 93% (25 of 27) of patients."
    explanation: >-
      Quantifies the de novo fraction among the patients for whom biparental
      samples were available, which is the basis of the recorded de novo rate.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The p.V326F variant in S21 was inherited from her reportedly unaffected father, whereas the p.A449V variant in S26 was inherited from her mother, who was diagnosed with intellectual disability"
    explanation: >-
      The basis for INCOMPLETE rather than COMPLETE penetrance: a variant in the
      functionally implicated FFAT-motif cluster was transmitted by a reportedly
      unaffected father. Note the second allele in the same sentence is weaker
      evidence, since the transmitting mother's intellectual disability was
      judged independent of her CERT1 genotype.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "When analyzed in greater depth, these variants present some doubts about their actual pathogenicity"
    explanation: >-
      Cuts against reading every inherited allele as reduced penetrance: the
      authors question whether four singleton non-clustered variants, including
      the maternally inherited p.A449V, are pathogenic at all. The incomplete
      penetrance claim therefore rests on the single p.V326F family.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In CerTra syndrome, most pathogenic variants arise de novo and are heterozygous."
    explanation: >-
      An independent report states the dominant, predominantly de novo
      inheritance pattern directly.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: NOT_YET_DOCUMENTED
  notes: >-
    No population-based prevalence or incidence estimate exists. The largest
    published delineation is an international series of 31 unrelated individuals
    ascertained through rare-disease referral and matchmaking, which has no
    population denominator, and MONDO records no Orphanet cross-reference from
    which an Orphanet prevalence class could be taken. The literature case count
    is recorded here rather than a rate; do not read NOT_YET_DOCUMENTED as a
    claim that the disorder is vanishingly rare, since ascertainment through
    nonspecific developmental delay is likely incomplete.
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we characterize 31 individuals with de novo missense variants in CERT1."
    explanation: >-
      Establishes the size of the largest reported case series, which is the
      only occurrence figure available for this disorder.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Due to the limited number of reported cases and the rarity of CerTra syndrome, the neuroimaging features associated with this condition remain insufficiently characterized, and definitive conclusions have yet to be established."
    explanation: >-
      Confirms that the reported case count remains small enough that even
      descriptive features are not yet settled, let alone population rates.
pathophysiology:
- name: CERT1 Autoregulatory-Domain Missense Variant
  biological_scale: MOLECULAR
  description: >-
    The initiating lesion is a heterozygous missense variant in CERT1 affecting
    the autoregulatory apparatus of the ceramide transport protein: the
    serine-repeat motif serines (p.S132, p.S135, p.S138, p.S141), the nearby
    non-SRM residue p.G243, or the dimeric helical domain that mediates
    homeostatic inactivation. The variant is de novo in most reported
    individuals.
  mechanism_confidence: ESTABLISHED
  genes:
  - preferred_term: CERT1
    term:
      id: hgnc:2205
      label: CERT1
  genetic_context:
    gene:
      preferred_term: CERT1
      term:
        id: hgnc:2205
        label: CERT1
    allele_type: missense
    variant_origin: DE_NOVO
    zygosity: HETEROZYGOUS
    functional_impact_category: GAIN_OF_FUNCTION
    description: >-
      Disease alleles are heterozygous missense changes that render CERT
      excessively active. This is a gain of function and not haploinsufficiency:
      a C-terminal frameshift allele (p.Pro749fs) segregated away from
      intellectual disability in its family and left CERT function intact in
      knock-in cells, so it served as a disease-matched negative control.
  downstream:
  - target: Loss of Phosphorylation-Dependent CERT Autorepression
    causal_link_type: DIRECT
    description: >-
      Substitution of an SRM serine, or of a residue that supports SRM
      phosphorylation, prevents the hyperphosphorylation that normally silences
      CERT.
    evidence:
    - reference: PMID:33347465
      reference_title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Biochemical analysis showed that S135 is essential for hyperphosphorylation of a serine-repeat motif of CERT, which is required for down-regulation of CERT activity."
      explanation: >-
        Directly links the variant residue to failure of the phosphorylation
        step that downregulates CERT, which is the next node in the chain.
    - reference: PMID:34688657
      reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Biochemical analysis showed that G243R and S132L, but not dupAA, impair SRM hyperphosphorylation and render the CERT variants excessively active."
      explanation: >-
        Shows the same edge for two further disease alleles, including one
        outside the SRM, against a non-causative control allele.
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Several variants fall into a previously uncharacterized dimeric helical domain that enables CERT homeostatic inactivation, without which sphingolipid production goes unchecked."
    explanation: >-
      Establishes that the disease variants sit in the machinery that switches
      CERT off, which is why the variant class is the initiating lesion.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These variants cluster within regulatory domains essential for CERT phosphorylation and inactivation."
    explanation: >-
      Independently states the regulatory-domain clustering that defines this
      node.
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, familial analysis revealed that the dupAA variant was not associated with ID, allowing us to utilize it as a disease-matched negative control for CERT1 variants that are associated with ID."
    explanation: >-
      Supports restricting this node to autoregulatory-domain alleles: a
      C-terminal frameshift in the same gene was shown not to be causal.
- name: Loss of Phosphorylation-Dependent CERT Autorepression
  biological_scale: MOLECULAR
  description: >-
    CERT is normally silenced by multisite phosphorylation of its serine-repeat
    motif once cellular sphingomyelin requirements are met. Disease variants
    shift the protein from the hyperphosphorylated form to de- or
    hypophosphorylated forms, so this negative-feedback brake is lost.
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: SRM hyperphosphorylation of CERT
    term:
      id: GO:0018105
      label: peptidyl-serine phosphorylation
    modifier: DECREASED
  downstream:
  - target: Constitutive CERT Activation
    causal_link_type: DIRECT
    description: >-
      Because SRM phosphorylation is what represses transport activity, its
      failure leaves the transporter switched on.
    evidence:
    - reference: PMID:42051775
      reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Several disease-associated CERT1 variants disrupt the autoregulatory phosphorylation of CERT, resulting in constitutive activation of the transporter and increased sphingolipid synthesis, consistent with a gain-of-function mechanism"
      explanation: >-
        States the causal step from disrupted autoregulatory phosphorylation to
        constitutive activation.
  evidence:
  - reference: PMID:31254361
    reference_title: "Structure, functions and regulation of CERT, a lipid-transfer protein for the delivery of ceramide at the ER-Golgi membrane contact sites."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The function of CERT is down-regulated by multisite phosphorylation of a serine-repeat motif (SRM) and up-regulated by phosphorylation of serine 315 in CERT."
    explanation: >-
      Establishes the normal repressive role of SRM phosphorylation that disease
      variants abolish.
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Hyperphosphorylation of CERT's serine-repeat motif (SRM) decreases its functionality."
    explanation: >-
      Confirms the direction of the regulatory relationship in the same
      experimental system that characterised the disease alleles.
- name: Constitutive CERT Activation
  biological_scale: MOLECULAR
  description: >-
    With autorepression lost, CERT is excessively and constitutively active as a
    ceramide transfer protein. This is the pivotal gain-of-function state of the
    disorder and the node that CERT inhibitors are aimed at.
  mechanism_confidence: ESTABLISHED
  molecular_functions:
  - preferred_term: CERT-mediated ceramide transfer activity
    term:
      id: GO:0120017
      label: ceramide transfer activity
    modifier: GAIN_OF_FUNCTION
  downstream:
  - target: Excess ER-to-Golgi Ceramide Transfer
    causal_link_type: DIRECT
    description: >-
      An unrepressed transporter moves more ceramide per unit time across the
      ER-Golgi membrane contact site.
    evidence:
    - reference: PMID:31254361
      reference_title: "Structure, functions and regulation of CERT, a lipid-transfer protein for the delivery of ceramide at the ER-Golgi membrane contact sites."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Ceramide transport protein (CERT) transports ceramide from the ER to the trans-Golgi regions at the ER-Golgi membrane contact sites (MCS)."
      explanation: >-
        Establishes that transfer at the contact site is the activity that CERT
        activation scales up.
      directness: INDIRECT
  - target: Punctate Subcellular Redistribution of CERT
    causal_link_type: DIRECT
    description: >-
      Constitutively activated CERT variants leave the diffuse cytoplasmic and
      perinuclear pattern of the wild-type protein and concentrate into puncta,
      partly co-staining with VAP-A.
    evidence:
    - reference: PMID:34688657
      reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Additionally, both S132L and G243R mutations but not dupAA caused the proteins to be distributed in a punctate subcellular manner."
      explanation: >-
        Ties the redistribution specifically to the activating disease alleles
        and not to the non-causative control allele.
  evidence:
  - reference: PMID:33347465
    reference_title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These results identified specific ID-associated CERT1 mutations that induced gain-of-function effects on CERT activity."
    explanation: >-
      States the gain-of-function activity state that defines this node.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical severity reflects the degree to which CERT autoregulation is disrupted"
    explanation: >-
      Clinical severity grades with the degree of autoregulatory disruption,
      which is what makes the resulting excess CERT activity the operative
      disease state rather than an incidental in-vitro property.
- name: Punctate Subcellular Redistribution of CERT
  biological_scale: CELLULAR
  description: >-
    Activated CERT variants adopt an abnormal punctate intracellular
    distribution. This is a cellular correlate of the activated state rather
    than a demonstrated cause of downstream neural pathology, and it has been
    proposed as the basis of a functional assay for variant interpretation.
  mechanism_confidence: ESTABLISHED
  cellular_components:
  - preferred_term: organelle membrane contact site
    term:
      id: GO:0044232
      label: organelle membrane contact site
  evidence:
  - reference: PMID:33347465
    reference_title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Amino acid replacements of S135 abnormally activated CERT and induced an intracellular punctate distribution pattern of this protein."
    explanation: >-
      Couples the activated state to the punctate pattern for the S135 alleles.
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "This conclusion supports our previous proposal that the intracellular punctate distribution pattern of CERT mutants may be applicable as a molecular diagnostic assay to assess whether CERT is abnormally activated by CERT1 mutations."
    explanation: >-
      Records that the redistribution is being used as a readout of activation
      rather than as a causal step, which is why this node has no downstream edge.
- name: Excess ER-to-Golgi Ceramide Transfer
  biological_scale: CELLULAR
  description: >-
    Non-vesicular delivery of ceramide from the endoplasmic reticulum to the
    trans-Golgi runs above its normally regulated level.
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: ER-to-Golgi ceramide transport
    term:
      id: GO:0035627
      label: ceramide transport
    modifier: INCREASED
  cellular_components:
  - preferred_term: endoplasmic reticulum membrane
    term:
      id: GO:0005789
      label: endoplasmic reticulum membrane
  - preferred_term: trans-Golgi network
    term:
      id: GO:0005802
      label: trans-Golgi network
  downstream:
  - target: Increased Sphingomyelin Synthesis
    causal_link_type: DIRECT
    description: >-
      Ceramide arriving at the trans-Golgi is the substrate for sphingomyelin
      synthase, so a higher delivery rate raises sphingomyelin output.
    evidence:
    - reference: PMID:34688657
      reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "we infer that the majority of ID-associated CERT variants may impair SRM phosphorylation-dependent repression, resulting in an increase in sphingomyelin production concurrent with CERT subcellular redistribution."
      explanation: >-
        States the step from unrepressed transfer to increased sphingomyelin
        production.
  evidence:
  - reference: PMID:33347465
    reference_title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The ceramide transport protein (CERT) encoded by CERT1 mediates inter-organelle trafficking of ceramide for the synthesis of intracellular sphingomyelin."
    explanation: >-
      Establishes the transport step that is running in excess at this node.
- name: Increased Sphingomyelin Synthesis
  biological_scale: CELLULAR
  description: >-
    Sphingomyelin production rises above the level set by cellular demand.
    Metabolic labelling in cells expressing S132L or G243R CERT showed
    significantly more labelled sphingomyelin than wild-type-rescued cells.
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: sphingomyelin biosynthetic process
    term:
      id: GO:0006686
      label: sphingomyelin biosynthetic process
    modifier: INCREASED
  downstream:
  - target: Dysregulated Sphingolipid Homeostasis
    causal_link_type: DIRECT
    description: >-
      Sphingomyelin production that is no longer matched to demand is what
      breaks homeostatic control of the sphingolipid pool.
    evidence:
    - reference: PMID:36976648
      reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Several variants fall into a previously uncharacterized dimeric helical domain that enables CERT homeostatic inactivation, without which sphingolipid production goes unchecked."
      explanation: >-
        States that unchecked production is the immediate consequence of losing
        homeostatic inactivation.
  evidence:
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "When the mutant CERT S132L or G243R constructs were expressed, the levels of labeled SM were significantly higher than those observed in the WT CERT rescued cells"
    explanation: >-
      Direct metabolic-labelling measurement of the increased output for two
      disease alleles.
- name: Dysregulated Sphingolipid Homeostasis
  biological_scale: CELLULAR
  description: >-
    The feedback loop that matches sphingolipid biosynthetic flux to cellular
    requirement is broken, so the sphingolipid composition of membranes is set
    by an unregulated transporter rather than by demand.
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: sphingolipid metabolic process
    term:
      id: GO:0006665
      label: sphingolipid metabolic process
    modifier: DYSREGULATED
  downstream:
  - target: Impaired Neural Differentiation and Synaptic Membrane Function
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Membrane sphingolipids are required for neural differentiation, synaptic
      transmission and action potential propagation, so loss of homeostatic
      control of the pool is taken to compromise those processes. The
      intermediate steps and the vulnerable human neural cell type have not been
      identified.
    evidence:
    - reference: PMID:36976648
      reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Neural differentiation, synaptic transmission, and action potential propagation depend on membrane sphingolipids, whose metabolism is tightly regulated."
      explanation: >-
        Supports the dependence of these neural processes on regulated
        sphingolipid metabolism; the step to disease remains an inference, which
        is why the link is typed as having unknown intermediates.
      directness: INDIRECT
  - target: Facial dysmorphism
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The mild facial and distal limb features are placed downstream of the
      systemic sphingolipid lesion rather than of the neural node, since they
      are morphogenetic rather than neurological. No mechanism connecting
      sphingolipid flux to these structures has been demonstrated.
  - target: Digit, hand and foot anomalies
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Placed downstream of the systemic sphingolipid lesion rather than of the
      neural node, on the same reasoning as the facial features they accompany:
      they are morphogenetic rather than neurological. No mechanism connecting
      sphingolipid flux to limb patterning has been demonstrated.
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These findings uncover a central role for CERT autoregulation in the control of sphingolipid biosynthetic flux, provide unexpected insight into the structural organization of CERT, and suggest a possible therapeutic approach for patients with CerTra syndrome."
    explanation: >-
      Names control of sphingolipid biosynthetic flux as the function that CERT
      autoregulation serves and that is lost here.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These variants disrupt ceramide transport and sphingolipid homeostasis, leading to a clinical phenotype that includes developmental delay, movement abnormalities, and structural brain anomalies."
    explanation: >-
      Independent statement that disrupted sphingolipid homeostasis is the state
      that connects the molecular lesion to the clinical phenotype.
  notes: >-
    Whole-cell lipidomics in HCT116 cells expressing S132L or G243R CERT did not
    show a significant shift in bulk sphingolipid levels relative to wild-type
    CERT, so the dysregulation demonstrated to date is of biosynthetic flux and
    regulation rather than of steady-state whole-cell composition. No patient
    lipidomic or metabolomic signature has been validated.
- name: Impaired Neural Differentiation and Synaptic Membrane Function
  biological_scale: TISSUE
  description: >-
    Altered sphingolipid flux in the developing nervous system is inferred to
    compromise neural differentiation, membrane composition and synaptic
    function, producing the cognitive, motor, language and behavioural
    phenotype. This is the least well characterised step of the chain: no
    patient neural tissue, iPSC-neuron or organoid study has identified the
    primary vulnerable cell type.
  mechanism_confidence: PROVISIONAL
  biological_processes:
  - preferred_term: nervous system development
    term:
      id: GO:0007399
      label: nervous system development
    modifier: ABNORMAL
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  downstream:
  - target: Abnormal Cerebral Myelination and Atrophy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      A subset of affected individuals develop white-matter and atrophic changes
      on MRI, which are attributed to the same disturbance of neural lipid
      biology. The link rests on human imaging rather than on a demonstrated
      mechanism.
  - target: Global developmental delay
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Intellectual disability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Delayed speech and language development
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Motor delay
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Infantile hypotonia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Atypical behavior
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Autism spectrum disorder
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Stereotypical hand movements
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Self-injurious behavior
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Sleep disturbance
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Attention deficit hyperactivity disorder
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Aggressive behavior
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Seizures
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Impaired pain sensation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Feeding difficulties
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability (3). Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."
    explanation: >-
      Enumerates the neurodevelopmental manifestations that this node is
      asserted to produce.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in the ceramide transporter CERT (CERT1), which is involved in sphingolipid biosynthesis, are associated with intellectual disability, but the pathogenic mechanism remains obscure."
    explanation: >-
      Records both the association with intellectual disability and the authors'
      own statement that the pathogenic mechanism at this level is unresolved,
      which is why the node is marked PROVISIONAL.
- name: Abnormal Cerebral Myelination and Atrophy
  biological_scale: TISSUE
  description: >-
    A subset of affected individuals show thin corpus callosum,
    ventriculomegaly, delayed myelination and cerebellar atrophy on brain MRI.
    In one autopsied child, choroid plexus epithelial disorganisation with
    reduced aquaporin-1, cysts and calcification, and perivascular spaces
    distended with proteinaceous material were also found.
  mechanism_confidence: PROVISIONAL
  biological_processes:
  - preferred_term: myelination
    term:
      id: GO:0042552
      label: myelination
    modifier: ABNORMAL
  cell_types:
  - preferred_term: oligodendrocyte
    term:
      id: CL:0000128
      label: oligodendrocyte
  locations:
  - preferred_term: corpus callosum
    term:
      id: UBERON:0002336
      label: corpus callosum
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  downstream:
  - target: Thin corpus callosum
    causal_link_type: DIRECT
  - target: Delayed myelination
    causal_link_type: DIRECT
  - target: Ventriculomegaly
    causal_link_type: DIRECT
  - target: Cerebellar atrophy
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."
    explanation: >-
      Enumerates the structural brain findings that constitute this node.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuropathological examination demonstrated marked ChP epithelial disorganization, reduced aquaporin-1 (AQP1) expression, cyst formation, and focal calcifications, which may be associated with disturbances in cerebrospinal fluid (CSF) dynamics."
    explanation: >-
      Adds the single available neuropathological characterisation; the hedged
      wording is why the node is PROVISIONAL rather than ESTABLISHED.
phenotypes:
- category: Neurologic
  name: Global developmental delay
  description: >-
    Delay across cognitive and motor domains is the usual presenting feature and
    is generally apparent during infancy.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "only 4 of the individuals did not show some form of developmental delay by the end of the first year of life (4 of 26, 15%)"
    explanation: >-
      Gives the denominator behind the VERY_FREQUENT band: 22 of 26 patients had
      some form of developmental delay by the end of the first year, stated as
      the complementary 4 of 26 who did not.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"
    explanation: >-
      Lists global developmental delay among the core manifestations of the
      CERT1-related disorder.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Her developmental course was notable for global delay affecting both cognitive and motor domains."
    explanation: >-
      Individual-level confirmation in a molecularly confirmed case.
- category: Neurologic
  name: Intellectual disability
  description: >-
    Intellectual disability is the defining feature and ranges from mild to
    profound.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"
    explanation: >-
      Lists intellectual disability of varying degree among the core features.
  - reference: PMID:33347465
    reference_title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Utilizing whole exome sequencing analysis, we identified a novel CERT variant, which substitutes a serine at position 135 (S135) for a proline in a patient with severe ID."
    explanation: >-
      A molecularly defined case at the severe end of the reported range.
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The Wechsler Intelligence Scale for Children – Fifth Edition showed a full scale composite score of 55, which was consistent with a mild ID"
    explanation: >-
      A formally measured mild end of the range, in the proband of the Tamura
      report. Note this proband's CERT1 allele was subsequently judged
      non-causative, so the measurement bounds the reported spectrum of the
      referral population rather than of confirmed MRD34.
    directness: INDIRECT
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intellectual disability ranged from mild to profound, as per the criteria of the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5)"
    explanation: >-
      States the range in the defining cohort and the instrument used to grade
      it, which is what makes mild-to-profound a measured span rather than an
      impression.
- category: Neurologic
  name: Motor delay
  description: >-
    Motor milestones are delayed, with reported outcomes ranging from mild delay
    to walking only with support.
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These were likely early manifestations of what would later become frank motor delays, affecting 26 of 29 patients"
    explanation: >-
      The denominator behind the VERY_FREQUENT band, and the observation that
      motor delay is prefigured by the neonatal feeding and tone problems.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"
    explanation: >-
      Lists motor delay among the core manifestations.
- category: Neurologic
  name: Infantile hypotonia
  description: >-
    Hypotonia is typically evident in infancy and contributes to both motor
    delay and feeding difficulty.
  phenotype_term:
    preferred_term: Infantile hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
    onset:
      onset_category: INFANTILE
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"
    explanation: >-
      States infantile hypotonia as a core manifestation.
- category: Neurologic
  name: Delayed speech and language development
  description: >-
    Speech and language delay is prominent and often more severe than the
    general cognitive delay; some individuals remain non-verbal.
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."
    explanation: >-
      Lists speech delay among the additional clinical features of the disorder.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She was non-verbal and had chronic sleep disturbance."
    explanation: >-
      Documents the severe end of the language phenotype in a molecularly
      confirmed case.
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "he presented with speech delay with a limited number of words and no phrasing"
    explanation: >-
      A clinical description of the speech phenotype in a proband referred for
      CERT1 evaluation.
    directness: INDIRECT
- category: Behavioral
  name: Atypical behavior
  description: >-
    Behavioural abnormality is the umbrella finding; the individual behaviours
    that make it up are curated separately below with their own cohort
    denominators. Retained as the general term because the secondary literature
    describes the phenotype at this level.
  phenotype_term:
    preferred_term: Atypical behavior
    term:
      id: HP:0000708
      label: Atypical behavior
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neurobehavioral abnormalities frequently led to a diagnosis of autism spectrum disorder (ASD) (19 of 27, 70%); some patients displayed stereotypical hand movements (14 of 18), self-injurious behavior (9 of 19), high pain tolerance (9 of 18), disrupted sleep patterns (9 of 21), attention deficit–hyperactivity disorder (10 of 19), or aggression (6 of 20)."
    explanation: >-
      The single cohort sentence that enumerates the component behaviours and
      their denominators; each is also curated as its own phenotype.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."
    explanation: >-
      Lists behavioural abnormalities among the clinical features.
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "He had a behavioral disorder that frequently shifted from one activity to another and exhibited recurrent mannerisms, such as repeatedly putting his hand to his mouth."
    explanation: >-
      An individual-level description of the stereotypic and attentional
      behaviour seen in this referral population.
    directness: INDIRECT
- category: Behavioral
  name: Autism spectrum disorder
  description: >-
    A formal autism spectrum disorder diagnosis was reached in most assessed
    members of the defining cohort. It accompanies the neurodevelopmental
    phenotype rather than constituting it: no cohort member carried ASD as a
    primary diagnosis, and a targeted search of the SPARK autism database and
    denovo-db found no de novo protein-altering CERT1 variant in the exome data,
    so the authors conclude that CERT1 is not a significant autism gene and that
    CerTra syndrome is a recognisable neurodevelopmental syndrome distinct from
    ASD.
  phenotype_term:
    preferred_term: Autism spectrum disorder
    term:
      id: HP:0000717
      label: Autism
  frequency: FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neurobehavioral abnormalities frequently led to a diagnosis of autism spectrum disorder (ASD) (19 of 27, 70%)"
    explanation: >-
      The cohort denominator behind the FREQUENT band, 19 of 27 assessed
      patients.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "indicates that CERT1 variants are unlikely to be a significant contributor to autism but instead cause a recognizable neurodevelopmental syndrome distinct from ASD, which we will refer to as CerTra syndrome."
    explanation: >-
      Refutes any reading of this phenotype as making MRD34 an autism entity or
      CERT1 an autism gene; the same authors reach the opposite conclusion from
      SPARK and denovo-db and name the disorder as distinct from ASD.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "none of the individuals in our cohort was diagnosed with ASD as a primary condition"
    explanation: >-
      Refutes reading ASD as the presenting or primary condition. In every
      cohort member it was a comorbid behavioural diagnosis reached alongside
      the developmental phenotype.
- category: Behavioral
  name: Stereotypical hand movements
  description: >-
    Repetitive, non-functional hand movements, the most frequent of the
    individual behavioural features recorded in the cohort.
  phenotype_term:
    preferred_term: Stereotypical hand movements
    term:
      id: HP:0000733
      label: Motor stereotypy
  frequency: FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "some patients displayed stereotypical hand movements (14 of 18)"
    explanation: >-
      The cohort denominator behind the FREQUENT band, 14 of 18 assessed
      patients.
- category: Behavioral
  name: Self-injurious behavior
  description: >-
    Self-directed injurious behaviour, reported in about half of the patients
    for whom behavioural assessment was available.
  phenotype_term:
    preferred_term: Self-injurious behavior
    term:
      id: HP:0100716
      label: Self-injurious behavior
  frequency: FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "some patients displayed stereotypical hand movements (14 of 18), self-injurious behavior (9 of 19)"
    explanation: >-
      The cohort denominator behind the FREQUENT band, 9 of 19 assessed
      patients.
- category: Behavioral
  name: Sleep disturbance
  description: >-
    Disrupted sleep patterns, a recurrent and separately burdensome feature
    rather than a consequence of the seizure phenotype.
  phenotype_term:
    preferred_term: Disrupted sleep patterns
    term:
      id: HP:0002360
      label: Sleep disturbance
  frequency: FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "high pain tolerance (9 of 18), disrupted sleep patterns (9 of 21)"
    explanation: >-
      The cohort denominator behind the FREQUENT band, 9 of 21 assessed
      patients.
- category: Behavioral
  name: Attention deficit hyperactivity disorder
  description: >-
    Attention deficit and hyperactivity, diagnosed in about half of the
    behaviourally assessed cohort.
  phenotype_term:
    preferred_term: Attention deficit hyperactivity disorder
    term:
      id: HP:0007018
      label: Attention deficit hyperactivity disorder
  frequency: FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "disrupted sleep patterns (9 of 21), attention deficit–hyperactivity disorder (10 of 19)"
    explanation: >-
      The cohort denominator behind the FREQUENT band, 10 of 19 assessed
      patients.
- category: Behavioral
  name: Aggressive behavior
  description: >-
    Aggression, the least frequent of the individual behavioural features
    recorded in the cohort but still present in about a third of those assessed.
  phenotype_term:
    preferred_term: Aggressive behavior
    term:
      id: HP:0000718
      label: Aggressive behavior
  frequency: FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "disrupted sleep patterns (9 of 21), attention deficit–hyperactivity disorder (10 of 19), or aggression (6 of 20)."
    explanation: >-
      The cohort denominator behind the FREQUENT band, 6 of 20 assessed
      patients, which sits at the lower edge of that band.
- category: Neurologic
  name: Impaired pain sensation
  description: >-
    Reduced responsiveness to painful stimuli, usually reported clinically as a
    high pain tolerance.
  phenotype_term:
    preferred_term: High pain tolerance
    term:
      id: HP:0007328
      label: Impaired pain sensation
  frequency: FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "self-injurious behavior (9 of 19), high pain tolerance (9 of 18)"
    explanation: >-
      Gives the denominator behind the FREQUENT band, 9 of 18 assessed patients.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."
    explanation: >-
      Lists high pain tolerance among the clinical features of the disorder.
- category: Neurologic
  name: Seizures
  description: >-
    Seizures occur in a substantial minority of affected individuals and range
    from readily controlled epilepsy to epileptic encephalopathy. Seizures are
    not universal; the reported autopsy case had none.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  frequency: FREQUENT
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Multiple seizure types were reported (16 of 29)."
    explanation: >-
      Gives the denominator behind the FREQUENT band, 16 of 29, and records that
      seizure type varied rather than following one syndromic pattern.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."
    explanation: >-
      Lists seizures among the clinical features of the disorder.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "no epilepsy or other neurological disorder has been diagnosed for this case"
    explanation: >-
      A molecularly confirmed individual without epilepsy, which refutes any
      reading of seizures as an obligate feature.
- category: Gastrointestinal
  name: Feeding difficulties
  description: >-
    Feeding and swallowing difficulty, often beginning in the neonatal period,
    contributes to poor growth and requires nutritional support in some
    individuals.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
    onset:
      onset_category: NEONATAL
  frequency: FREQUENT
  sequelae:
  - target: Failure to thrive
    causal_link_type: DIRECT
    description: >-
      Neonatal feeding difficulty is the route by which poor weight gain is
      established in this disorder.
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fifteen (of 24) patients had neonatal feeding difficulties, often with hypotonia or failure to thrive."
    explanation: >-
      Gives the denominator behind the FREQUENT band, 15 of 24, and dates the
      onset to the neonatal period.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."
    explanation: >-
      Lists feeding difficulties among the clinical features of the disorder.
- category: Growth
  name: Failure to thrive
  description: >-
    Poor weight gain accompanying the neonatal feeding difficulty and hypotonia.
    Most cohort members for whom birth data were available were born
    underweight, so the growth problem starts before the feeding problem is
    established.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fifteen (of 24) patients had neonatal feeding difficulties, often with hypotonia or failure to thrive."
    explanation: >-
      Names failure to thrive as a frequent accompaniment of the neonatal
      feeding difficulty. No separate denominator is reported for failure to
      thrive itself, so no frequency band is recorded here.
- category: Craniofacial
  name: Facial dysmorphism
  description: >-
    Facial dysmorphism is subtle rather than gestalt-forming: anteverted nares
    with a depressed or broad nasal bridge, enlarged earlobes, synophrys,
    micrognathia, dental anomalies and palatine ridges. It is not a diagnostic
    handle and was characterised by blinded dysmorphology review of photographs
    rather than by clinical gestalt.
  phenotype_term:
    preferred_term: Subtle facial dysmorphism
    term:
      id: HP:0001999
      label: Abnormal facial shape
  diagnostic: false
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Subtle facial dysmorphisms included anteverted nares with a depressed or broad nasal bridge, enlarged earlobes, synophrys, micrognathia, dental anomalies (protruding incisors and diastema), and palatine ridges"
    explanation: >-
      Enumerates the facial features recorded by the cohort's blinded
      dysmorphology analysis.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These patients have a syndromic presentation characterized by infantile hypotonia; mild dysmorphologies (affecting the face, hands or feet)"
    explanation: >-
      Places the dysmorphism in the cohort's own summary of the syndromic
      presentation and records that it is mild.
- category: Skeletal
  name: Digit, hand and foot anomalies
  description: >-
    Anomalies of the hands, feet and digits, including third and fourth finger
    syndactyly, club foot, hallux varus with sandal gaps, a short first
    metatarsal and long fifth fingers. As with the facial features these are
    mild and variable, not a recognisable pattern.
  phenotype_term:
    preferred_term: Digit, hand and foot anomalies
    term:
      id: HP:0011297
      label: Abnormal digit morphology
  diagnostic: false
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Anomalies affecting the hands, feet, or digits included third/fourth finger syndactyly, club foot, or hallux varus (sandal gaps)"
    explanation: >-
      Enumerates the reported hand, foot and digit anomalies. The bound term
      covers the digital findings; club foot is a foot rather than a digit
      anomaly and is carried in the description rather than by the binding.
- category: Neuroimaging
  name: Thin corpus callosum
  description: >-
    A thin or hypoplastic corpus callosum is among the most commonly reported
    structural brain findings.
  phenotype_term:
    preferred_term: Thin corpus callosum
    term:
      id: HP:0033725
      label: Thin corpus callosum
  diagnostic: false
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."
    explanation: >-
      Names thin corpus callosum among the commonly reported neuroimaging
      findings.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroimaging frequently revealed a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy"
    explanation: >-
      The primary cohort statement of the neuroimaging findings, cited directly
      rather than through the secondary report that summarises it.
- category: Neuroimaging
  name: Ventriculomegaly
  description: >-
    Enlargement of the cerebral ventricular system is reported in a subset of
    affected individuals.
  phenotype_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."
    explanation: >-
      Names ventriculomegaly among the commonly reported neuroimaging findings.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroimaging frequently revealed a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy"
    explanation: >-
      The primary cohort statement of the neuroimaging findings, cited directly
      rather than through the secondary report that summarises it.
- category: Neuroimaging
  name: Delayed myelination
  description: >-
    Delayed myelination on brain MRI, in one long-followed individual evolving
    into more widespread white-matter change.
  phenotype_term:
    preferred_term: Delayed myelination
    term:
      id: HP:0012448
      label: Delayed myelination
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."
    explanation: >-
      Names delayed myelination among the commonly reported neuroimaging
      findings.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroimaging frequently revealed a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy"
    explanation: >-
      The primary cohort statement of the neuroimaging findings, cited directly
      rather than through the secondary report that summarises it.
- category: Neuroimaging
  name: Cerebellar atrophy
  description: >-
    Cerebellar atrophy is reported in a subset of affected individuals.
  phenotype_term:
    preferred_term: Cerebellar atrophy
    term:
      id: HP:0001272
      label: Cerebellar atrophy
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In a recent study by Gehin et al. (3), neuroimaging findings commonly reported in CerTra syndrome include a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy."
    explanation: >-
      Names cerebellar atrophy among the commonly reported neuroimaging
      findings.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroimaging frequently revealed a thin corpus callosum, ventriculomegaly, delayed myelination, and cerebellar atrophy"
    explanation: >-
      The primary cohort statement of the neuroimaging findings, cited directly
      rather than through the secondary report that summarises it.
genetic:
- name: CERT1 Gain-of-Function Missense Variants
  gene_term:
    preferred_term: CERT1
    term:
      id: hgnc:2205
      label: CERT1
  association: Causative
  presence: Positive
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    CERT1 was called COL4A3BP until HGNC renamed it in 2019, so the founding
    literature indexes the gene under the old symbol; both must be searched. The
    disease alleles are heterozygous missense changes clustered in the
    autoregulatory apparatus and act by gain of function, so this entry must not
    be read as a haploinsufficiency disorder. The corollary matters for variant
    interpretation: a rare or even truncating CERT1 variant is not evidence of
    MRD34 on its own. The C-terminal frameshift c.2242_2243dupAA p.(Pro749fs)
    segregated away from intellectual disability in its family and left CERT
    phosphorylation, activity and localisation intact in knock-in cells, and the
    authors used it as a disease-matched negative control. The disease alleles
    are not scattered across the protein. Twenty-seven of the 31 enrolled
    patients carried a variant in the region between the pleckstrin homology and
    the C-terminal START-related domain, and those variants populate four spatial
    clusters: the first serines of the serine-rich region (p.S132, p.S135,
    p.S138, p.S141), p.T166, residues 240 to 254 including the recurrent p.G243,
    and the C-terminal end of the FFAT motif (p.V326F, p.A329P, p.L330V,
    p.L330P). Broad genotype-phenotype correlation follows that structure, with
    p.S132 and p.S135 at the severe end and p.S138, p.T166 and p.G243 associated
    with normal early milestones followed by regression or slowing. Per-allele
    case counts for individual variants are in the cohort paper's supplemental
    tables and are not reproduced here.
  inheritance:
  - name: Autosomal dominant inheritance
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    description: >-
      Heterozygous, usually de novo, with variable expressivity.
    evidence:
    - reference: PMID:42051775
      reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "In CerTra syndrome, most pathogenic variants arise de novo and are heterozygous."
      explanation: >-
        States the dominant, predominantly de novo mode for this gene-disease
        pair.
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we characterize 31 individuals with de novo missense variants in CERT1."
    explanation: >-
      The cohort that established CERT1 as the causal gene and defined the
      allele class as de novo missense.
  - reference: PMID:33347465
    reference_title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These results identified specific ID-associated CERT1 mutations that induced gain-of-function effects on CERT activity."
    explanation: >-
      Functional evidence that the disease alleles act by gain of function
      rather than by loss.
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The Gene Nomenclature Committee of the Human Genome Organization revised the official symbol of the gene from COL4A3BP to CERT1 in 2019"
    explanation: >-
      Documents the gene symbol change that splits this disorder's literature
      between two names.
  - reference: PMID:25356899
    reference_title: "De novo mutations in moderate or severe intellectual disability."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "DNMs in EIF2C1 and COL4A3BP have also been previously reported in single individuals with severe ID"
    explanation: >-
      Records the early candidate-gene stage of this gene-disease relationship,
      under the former COL4A3BP symbol and before the association was
      established.
    directness: INDIRECT
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The majority (27 of 31, 87%) of variants from our enrolled patients occurred in the region between the pleckstrin homology (PH) and C-terminal START-related (START) domain"
    explanation: >-
      Quantifies the positional clustering of disease alleles in the
      PH-to-START region, which is the basis for the mechanism-aware variant
      interpretation described in the notes.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These variants populated 4 distinct subregions, whereby the geometric mean distance"
    explanation: >-
      Records that the clustering resolves into four discrete subregions rather
      than a single hotspot.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For the variants that recurred in multiple individuals, we were able to sketch out broad genotype-phenotype correlations."
    explanation: >-
      Establishes that allele identity carries prognostic information in this
      disorder, which is the claim the severity gradient in the notes rests on.
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals bearing mutations at p.S138, p.T166, or p.G243 tended to not have perinatal difficulties and achieved early developmental milestones"
    explanation: >-
      The milder pole of that gradient, against the p.S132 and p.S135 alleles
      that produce congenital or perinatal onset and profound impairment.
diagnosis:
- name: CERT1 Molecular Genetic Confirmation
  description: >-
    Diagnosis rests on identifying a heterozygous pathogenic CERT1 variant in an
    individual with a compatible neurodevelopmental phenotype. Trio exome or
    genome sequencing is the informative test because most alleles are de novo,
    and the report should state the transcript accession: the same allele is
    numbered differently under the 598-residue and 624-residue CERT isoforms.
  diagnosis_term:
    preferred_term: trio exome sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  results: >-
    A heterozygous pathogenic CERT1 variant, interpreted against ACMG/AMP
    criteria with attention to de novo status, absence from population
    databases, clustering in the autoregulatory domains, and available
    functional data.
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Trio exome sequencing was conducted in the proband and both biological parents to investigate potential monogenic causes contributing to the patient's neurodevelopmental phenotype and sudden death."
    explanation: >-
      Documents the trio sequencing route actually used to reach the molecular
      diagnosis in a reported case.
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The genetic analysis identified a heterozygous de novo missense variant in the CERT1 gene (p. Ser260Leu; S260L). This variant was classified as pathogenic by the testing laboratory based on ACMG criteria."
    explanation: >-
      Shows the diagnostic endpoint: a heterozygous de novo CERT1 missense
      allele classified as pathogenic under ACMG criteria.
  - reference: PMID:33347465
    reference_title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Utilizing whole exome sequencing analysis, we identified a novel CERT variant, which substitutes a serine at position 135 (S135) for a proline in a patient with severe ID."
    explanation: >-
      Exome sequencing as the route to the molecular diagnosis in the index
      S135P case.
- name: Functional Assay of CERT Activation for Variant Interpretation
  description: >-
    Because pathogenicity here is a gain-of-function property rather than a
    truncation, a CERT1 variant of uncertain significance can be triaged by
    functional testing: loss of SRM hyperphosphorylation on western blot,
    increased metabolic labelling of sphingomyelin, and a punctate rather than
    diffuse subcellular distribution of tagged CERT. This is a research-level
    assay, not a clinically validated test.
  diagnosis_term:
    preferred_term: cellular CERT activation and localization assay
  results: >-
    Loss of the hyperphosphorylated CERT band, elevated labelled sphingomyelin
    relative to wild-type rescue, and punctate CERT distribution together
    indicate an activating allele.
  evidence:
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "This conclusion supports our previous proposal that the intracellular punctate distribution pattern of CERT mutants may be applicable as a molecular diagnostic assay to assess whether CERT is abnormally activated by CERT1 mutations."
    explanation: >-
      The authors explicitly propose the localisation pattern as a variant
      interpretation assay.
  - reference: PMID:33347465
    reference_title: "Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These findings provide a possible molecular basis for not only new diagnostics but also a conceivable pharmaceutical intervention for ID disorders caused by gain-of-function mutations in CERT1."
    explanation: >-
      States the diagnostic application of the gain-of-function characterisation.
  notes: >-
    Research-level only. No clinical laboratory offers this assay and no
    performance characteristics have been published.
- name: Routine Biochemical Screening
  description: >-
    Standard metabolic workup is performed in the diagnostic approach to
    unexplained developmental disability and is normal in this disorder. It has
    no positive diagnostic value here; its role is to exclude the treatable
    inborn errors that share the presentation. No blood, urine, enzyme or CSF
    biomarker of MRD34 is validated.
  diagnosis_term:
    preferred_term: routine metabolic screening panel
  presence: Negative
  results: >-
    Serum ammonia and lactate, thyroid and liver function, blood gases, serum
    amino acids, tandem mass spectrometry and urine organic acids are within
    normal limits.
  evidence:
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Metabolic tests, including measurement of serum ammonia and lactate levels, thyroid and liver function tests, blood gas analysis, serum amino acid chromatography, MS/MS, and the urine organic acid profile were applied. However, all results were within normal limits."
    explanation: >-
      Documents the normal routine biochemical screen in an investigated proband,
      which is the basis for recording this panel as negative in this disorder.
treatments:
- name: Symptom-Directed Supportive Care
  description: >-
    There is no disease-modifying therapy. Management is individualised and
    directed at the manifestations: early developmental and educational
    intervention, feeding and nutritional support, behavioural and sleep
    support, and surveillance of growth, vision, hearing and orthopaedic status.
  action_category: THERAPEUTIC
  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: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Despite growing recognition of this condition, detailed neuroimaging and neuropathological characterization remain limited."
    explanation: >-
      Supports the absence of a disease-specific evidence base; management is
      necessarily supportive and generic to the manifestations.
    directness: INDIRECT
  notes: >-
    No cited source reports efficacy or safety of any intervention in this
    disorder, so the components listed are standard neurodevelopmental care
    rather than treatments validated in MRD34.
- name: Physical Therapy
  description: >-
    Gross-motor rehabilitation for the hypotonia and motor delay, including
    mobility equipment and contracture prevention where walking is not attained.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Physical Therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  target_phenotypes:
  - preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  - preferred_term: Infantile hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"
    explanation: >-
      Establishes the motor impairments that motor rehabilitation addresses. No
      trial evidence in this disorder exists.
    directness: INDIRECT
- name: Occupational Therapy
  description: >-
    Fine-motor and daily-living-skills intervention, and adaptive equipment,
    addressing the same hypotonia and global developmental delay from the
    functional-independence side rather than the mobility side.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Occupational Therapy
    term:
      id: NCIT:C121351
      label: Occupational Therapy
  target_phenotypes:
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  - preferred_term: Infantile hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals exhibit varying degrees of infantile hypotonia, global developmental delay, motor delay, and intellectual disability"
    explanation: >-
      Establishes the developmental and tone impairments that occupational
      therapy addresses. No trial evidence in this disorder exists.
    directness: INDIRECT
- name: Speech and Language Therapy
  description: >-
    Speech-language intervention and augmentative or alternative communication,
    which is the relevant modality for the substantial minority who remain
    non-verbal.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Speech Language Therapy
    term:
      id: NCIT:C159273
      label: Speech Language Therapy
  target_phenotypes:
  - preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."
    explanation: >-
      Establishes the speech impairment this intervention addresses. No trial
      evidence in this disorder exists.
    directness: INDIRECT
- name: Antiseizure Pharmacotherapy
  description: >-
    Standard antiseizure medication selected by seizure type for the subset with
    epilepsy. No disorder-specific drug choice or pharmacogenomic algorithm has
    been established.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: anticonvulsant agent
      term:
        id: NCIT:C264
        label: Anticonvulsant Agent
  target_phenotypes:
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features may include speech delay, behavioral abnormalities, high pain tolerance, feeding difficulties, and seizures."
    explanation: >-
      Establishes seizures as a manifestation requiring standard antiseizure
      treatment. No disorder-specific efficacy data exist.
    directness: INDIRECT
- name: Genetic Counseling
  description: >-
    Counselling covers the dominant mechanism, the predominance of de novo
    origin, the residual recurrence risk from parental gonadal mosaicism after
    an apparently de novo result, and the availability of cascade or prenatal
    testing once a familial pathogenic allele is confirmed.
  action_category: COUNSELING_INFORMATIONAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:42051775
    reference_title: "Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In CerTra syndrome, most pathogenic variants arise de novo and are heterozygous."
    explanation: >-
      The de novo dominant mechanism is the fact that determines the recurrence
      risk counselling for this disorder.
- name: Pharmacological CERT Inhibition
  description: >-
    Preclinical only. The CERT inhibitor HPA-12 corrects morphological and motor
    abnormalities in the Drosophila model, and a 2024 live-cell NanoBRET screen
    of 140 HPA-12 derivatives identified six compounds outperforming the parent
    compound. There is no human dosing, safety, CNS penetration or
    developmental-toxicity evidence, and because CERT is required for normal
    membrane lipid homeostasis, over-inhibition is itself a plausible harm.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_mechanisms:
  - target: Constitutive CERT Activation
    description: >-
      The proposed therapeutic node: an inhibitor reduces the excess transfer
      activity that the disease variants create.
    evidence:
    - reference: PMID:36976648
      reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "inhibiting CERT pharmacologically corrects morphological and motor abnormalities in a Drosophila model of the disease, which we call ceramide transporter (CerTra) syndrome."
      explanation: >-
        Pharmacological inhibition of the activated transporter reverses the
        model phenotype, which is the target-validation evidence for this link.
  evidence:
  - reference: PMID:39450584
    reference_title: "Live-Cell Identification of Inhibitors of the Lipid Transfer Protein CERT Using Nanoluciferase Bioluminescence Resonance Energy Transfer (NanoBRET)."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The utility of the method was demonstrated by a library of 140 derivatives of the CERT inhibitor HPA-12. These were obtained in a combinatorial synthesis using solid-phase transacylation. Screening of the library led to six compounds that were picked and confirmed to be superior to HPA-12 in a subsequent dose-response study and also in an orthogonal lipidomics analysis."
    explanation: >-
      Documents the current state of CERT inhibitor development: a cell-based
      screening platform and improved chemical matter, with no patient exposure.
  - reference: PMID:39450584
    reference_title: "Live-Cell Identification of Inhibitors of the Lipid Transfer Protein CERT Using Nanoluciferase Bioluminescence Resonance Energy Transfer (NanoBRET)."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "CERT is considered a promising drug target but no direct cell-based methods exist to efficiently identify inhibitors."
    explanation: >-
      Frames CERT inhibition as a drug-discovery programme rather than an
      available therapy.
  notes: >-
    Not a treatment option. Curated so the therapeutic hypothesis and its
    evidence ceiling are explicit. ClinicalTrials.gov was queried for CERT1 and
    CerTra syndrome on 2026-09-04 and returned no interventional study of this
    disorder.
animal_models:
- species: Drosophila melanogaster
  genotype: CERT gain-of-function
  category: Genetic
  description: >-
    A Drosophila model expressing gain-of-function CERT, reported in the
    cohort paper as reproducing morphological and motor abnormalities that are
    corrected by pharmacological CERT inhibition. It is the only in vivo model
    of the disorder; no knock-in mouse, rat or zebrafish model was found.
  publication: PMID:36976648
  modeled_mechanisms:
  - target: Constitutive CERT Activation
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: >-
      The model reproduces the excess CERT transfer activity that defines the
      disorder, and its phenotype is reversible by inhibiting that activity,
      which is the strongest available causal test of this node.
    limitations: >-
      CERT-mediated ceramide transport is conserved, but the fly differs from
      human in brain architecture, developmental timing, sphingolipid
      composition and drug metabolism, so the quantitative relationship between
      degree of CERT activation and phenotype is not transferable.
    readouts:
    - name: Morphological and motor abnormalities after CERT inhibition
      target: Constitutive CERT Activation
      direction: RESTORED
      interpretation: >-
        Correction of the model phenotype by a CERT inhibitor is the readout
        that ties the phenotype to excess CERT activity rather than to some
        other consequence of the transgene.
      evidence:
      - reference: PMID:36976648
        reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "inhibiting CERT pharmacologically corrects morphological and motor abnormalities in a Drosophila model of the disease, which we call ceramide transporter (CerTra) syndrome."
        explanation: >-
          Reports the measurement: model abnormalities corrected by
          pharmacological CERT inhibition.
    - name: Head size after larval HPA-12 feeding
      target: Constitutive CERT Activation
      direction: RESTORED
      interpretation: >-
        The specific morphological measure behind the rescue. Head size is
        reduced by the extra dCERT copies and returns to control values when
        larvae are fed the CERT inhibitor, which is what makes the head
        phenotype attributable to CERT activity rather than to the transgene.
      evidence:
      - reference: PMID:36976648
        reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Feeding HPA-12 to +WT and +SL larvae (see Supplemental Methods) restored head size, suggesting that increased dCERT activity was responsible for this phenotype"
        explanation: >-
          Reports the head-size measurement and its restoration by HPA-12, the
          same inhibitor class as the treatment linked to this node.
    - name: Locomotor activity after HPA-12 pretreatment
      target: Constitutive CERT Activation
      direction: RESTORED
      interpretation: >-
        The motor half of the rescue. Transgenic flies are hypoactive relative
        to controls and inhibitor pretreatment restores activity without
        affecting control flies, so the effect requires the excess CERT
        activity rather than being a general drug effect.
      evidence:
      - reference: PMID:36976648
        reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Both +WT and +SL flies showed locomotor hypoactivity compared with Ctrl flies"
        explanation: >-
          Establishes the baseline locomotor deficit that the inhibitor arm
          reverses.
      - reference: PMID:36976648
        reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "rescued this phenotype in the transgenic lines but had little effect on Ctrl flies"
        explanation: >-
          Reports the rescue itself, and the control-line comparison that makes
          it specific to the CERT gain of function.
  - target: Impaired Neural Differentiation and Synaptic Membrane Function
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    model_scale: ORGANISM
    description: >-
      The model reproduces motor and morphological consequences of the lipid
      lesion, which is the closest available proxy for the human
      neurodevelopmental node.
    limitations: >-
      The fly cannot model the defining human manifestations of this node -
      intellectual disability, language, adaptive behaviour - and the reported
      phenotype is motor and morphological, so the correspondence to the human
      node is partial by construction.
    divergences:
    - divergence_type: SPECIES_MISMATCH
      materiality: QUALIFYING
      description: >-
        Drosophila neural development lacks the cortical expansion, myelinating
        oligodendrocyte biology and language circuitry through which the human
        node is expressed, so its motor and morphological output is a distant
        proxy for the human phenotype.
    - divergence_type: PROXY_QUANTITY
      materiality: QUALIFYING
      description: >-
        The measured quantities are fly locomotor activity and head or brain
        morphology. The node's quantities are human neural differentiation and
        synaptic membrane function, neither of which the model measures.
  evidence:
  - reference: PMID:36976648
    reference_title: "CERT1 mutations perturb human development by disrupting sphingolipid homeostasis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "inhibiting CERT pharmacologically corrects morphological and motor abnormalities in a Drosophila model of the disease, which we call ceramide transporter (CerTra) syndrome."
    explanation: >-
      Establishes the existence of the Drosophila disease model and its
      pharmacological rescue.
experimental_models:
- name: HCT116 CERT1-knockout rescue system
  experimental_model_type: CELL_LINE
  description: >-
    A human colon carcinoma line in which both CERT1 alleles are disrupted, then
    stably complemented with tagged wild-type or variant CERT. This is the
    platform on which the gain-of-function mechanism was established: CERT
    phosphorylation state by western blot, sphingomyelin output by metabolic
    labelling and lysenin sensitivity, and subcellular localisation by
    immunofluorescence, each read against wild-type rescue and against the
    non-causative p.Pro749fs allele.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:34688657
  modeled_mechanisms:
  - target: Loss of Phosphorylation-Dependent CERT Autorepression
    relationship: MEASURES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      The phosphorylation-state western blot is the direct readout of this node.
    limitations: >-
      A colon carcinoma line is not a neural cell, and the variant CERT is
      expressed ectopically against a null background rather than heterozygously
      alongside a wild-type allele as in patients.
    readouts:
    - name: Hyperphosphorylated versus de/hypophosphorylated CERT
      target: Loss of Phosphorylation-Dependent CERT Autorepression
      direction: DECREASED
      interpretation: >-
        Disease alleles shift CERT out of the hyperphosphorylated form, which is
        the loss of autorepression itself.
      evidence:
      - reference: PMID:34688657
        reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "Biochemical analysis showed that G243R and S132L, but not dupAA, impair SRM hyperphosphorylation and render the CERT variants excessively active."
        explanation: >-
          Reports the phosphorylation measurement for two disease alleles
          against a negative control allele.
  - target: Increased Sphingomyelin Synthesis
    relationship: MEASURES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      Metabolic labelling with radiolabelled serine quantifies sphingomyelin
      output for each allele.
    limitations: >-
      Bulk whole-cell sphingolipid levels did not differ significantly between
      variant and wild-type rescue in this system, so the assay reports
      biosynthetic flux rather than steady-state composition.
    readouts:
    - name: Metabolically labelled sphingomyelin
      target: Increased Sphingomyelin Synthesis
      direction: INCREASED
      interpretation: >-
        Higher labelled sphingomyelin in variant-expressing cells than in
        wild-type-rescued cells is the quantitative form of the node.
      evidence:
      - reference: PMID:34688657
        reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "When the mutant CERT S132L or G243R constructs were expressed, the levels of labeled SM were significantly higher than those observed in the WT CERT rescued cells"
        explanation: >-
          The direct measurement of increased sphingomyelin synthesis.
  evidence:
  - reference: PMID:34688657
    reference_title: "Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we infer that the majority of ID-associated CERT variants may impair SRM phosphorylation-dependent repression, resulting in an increase in sphingomyelin production concurrent with CERT subcellular redistribution."
    explanation: >-
      Summarises what this system established about the disease alleles, which
      is why it is treated as informative for these nodes.
differential_diagnoses:
- name: Other monogenic autism-intellectual disability syndromes
  description: >-
    The clinical picture is not distinctive enough to identify CERT1 without
    sequencing. The combination that should raise CERT1 specifically is
    intellectual disability with disproportionately severe speech and motor
    delay, infantile hypotonia, autistic or stereotypic behaviour, high pain
    tolerance, feeding and growth problems, and a thin corpus callosum or
    delayed myelination on MRI.
  distinguishing_features:
  - >-
    Only molecular testing distinguishes them; there is no pathognomonic
    clinical gestalt.
  - >-
    Interpretation must be mechanism-aware: a truncating CERT1 allele does not
    support the diagnosis, because the disorder is caused by gain of function.
  evidence:
  - reference: PMID:30878996
    reference_title: "Golgipathies in Neurodevelopment: A New View of Old Defects."
    supports: SUPPORT
    evidence_source: OTHER
    directness: INDIRECT
    snippet: 'We have previously proposed the term "Golgipathies" in relation to a group of disorders in which mutations in GA proteins or their molecular partners lead to consequences for brain development, in particular postnatal-onset microcephaly (POM), white-matter defects, and intellectual disability (ID).'
    explanation: >-
      Places MRD34 in the wider set of disorders in which a Golgi-apparatus or
      Golgi-associated protein lesion produces intellectual disability and
      white-matter change. That set is the nosological neighbourhood a CERT1
      variant has to be distinguished from, which is what this differential
      records; the review names COL4A3BP among its examples.
  notes: >-
    Also in the differential are developmental and epileptic encephalopathies,
    hypomyelinating leukodystrophies, chromosomal copy-number disorders,
    congenital disorders of glycosylation, mitochondrial disease and other
    disorders of sphingolipid metabolism. These are recorded as clinical context
    rather than as a cited claim; no cached source enumerates a differential for
    this disorder.
discussions:
- discussion_id: mrd34_vulnerable_cell_type
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Which human neural cell type is the one whose sphingolipid homeostasis
    failure produces the MRD34 phenotype?
  attaches_to:
  - pathophysiology#Impaired Neural Differentiation and Synaptic Membrane Function
  rationale: >-
    The chain from constitutively active CERT to increased sphingomyelin
    synthesis is demonstrated in cells, and the clinical phenotype is
    established, but nothing connects them at cellular resolution in human
    tissue. Neurons, neural progenitors, oligodendrocytes, astrocytes and
    Schwann cells are all plausible on expression grounds. No patient-derived
    iPSC neuron, cerebral organoid, single-cell atlas or human neural lipidomic
    study of this disorder exists, so the entry deliberately binds only neuron
    at this node rather than asserting a primary cell type.
- discussion_id: mrd34_drosophila_translational_validity
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    Does pharmacological rescue of the Drosophila CERT gain-of-function model
    predict any benefit in humans, given that the fly phenotype is motor and
    morphological while the human phenotype is cognitive, linguistic and
    behavioural?
  attaches_to:
  - pathophysiology#Constitutive CERT Activation
  - treatments#Pharmacological CERT Inhibition
  rationale: >-
    The only in vivo evidence that CERT inhibition is therapeutic comes from a
    fly. Drosophila has no cortical expansion, no myelinating oligodendrocytes
    and no language, so the readouts corrected in the model are not the
    manifestations that matter clinically. There is also a timing problem the
    model cannot address: the human phenotype is developmental, so a drug given
    after diagnosis acts on a nervous system already built under excess CERT
    activity. Finally, CERT is required for normal membrane lipid homeostasis in
    every tissue, so the therapeutic window in a developing human is unknown and
    over-inhibition is a plausible harm rather than a theoretical one.
  proposed_experiments:
  - experiment_id: mrd34_ipsc_neuron_rescue
    name: CERT inhibitor rescue in patient-derived iPSC neurons
    description: >-
      Differentiate neurons from iPSCs carrying a patient CERT1 allele and an
      isogenic corrected control, measure sphingolipid flux and neuronal
      differentiation and synaptic markers, and test whether a CERT inhibitor
      normalises them without impairing the control line.
    perturbations:
    - name: CERT inhibition in patient-derived neurons
      target: pathophysiology#Constitutive CERT Activation
      effect: Reduce CERT transfer activity pharmacologically.
    readouts:
    - name: Sphingomyelin biosynthetic flux
      target: pathophysiology#Increased Sphingomyelin Synthesis
      direction: RESTORED
      interpretation: >-
        Normalisation of flux in patient neurons without suppressing it below
        control levels would show that a therapeutic window exists in a human
        neural context.
    would_support:
    - pathophysiology#Constitutive CERT Activation
    supporting_outcome:
    - >-
      Patient neurons show elevated sphingomyelin flux and impaired
      differentiation relative to the isogenic control, and a CERT inhibitor
      returns both toward control values at a dose that leaves the control line
      unaffected.
    refuting_outcome:
    - >-
      Patient neurons show no measurable difference from the isogenic control,
      or the inhibitor corrects the lipid readout without affecting the neural
      phenotype, or no dose separates correction from toxicity in the control
      line.
- discussion_id: mrd34_epidemiology_gap
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What is the population prevalence of MRD34, and what fraction of unexplained
    intellectual disability does it account for?
  attaches_to:
  - prevalence#Worldwide
  rationale: >-
    Every published individual was ascertained through rare-disease referral or
    matchmaking, so there is no denominator. Because the phenotype is
    nonspecific and the causal alleles are missense rather than truncating, the
    disorder is exactly the kind that accumulates undiagnosed among people
    labelled with nonsyndromic developmental delay. A denominator would require
    systematic CERT1 review in an unselected sequenced intellectual-disability
    cohort, with mechanism-aware variant interpretation rather than a
    loss-of-function filter.
- discussion_id: mrd34_choroid_plexus_finding
  kind: OPEN_QUESTION
  status: OPEN
  prompt: >-
    Are the choroid plexus and perivascular space abnormalities reported in one
    autopsied child a feature of CerTra syndrome, or an incidental finding?
  attaches_to:
  - pathophysiology#Abnormal Cerebral Myelination and Atrophy
  rationale: >-
    The single neuropathological study of this disorder found choroid plexus
    epithelial disorganisation with reduced aquaporin-1, cysts and
    calcification, plus perivascular spaces distended with proteinaceous
    material, and raised the possibility of disturbed CSF dynamics and impaired
    perivascular clearance. That is a mechanistically attractive extension of a
    membrane-lipid disorder, but it rests on one case that was also complicated
    by sudden unexplained death in childhood, and the authors themselves state
    it only as a possibility. It should not be curated as a phenotype of the
    disorder until replicated.
notes: >-
  Curation provenance and known gaps.

  Phenotypes considered and left out. Cerebral atrophy and white-matter change
  (`HP:0002059`) and reduced growth or birth size (`HP:0001518`, `HP:0001507`)
  were both reviewed for the `phenotypes:` block and deliberately not added. Both
  are described in the deep-research report, but neither has a CERT1-specific
  quotable statement in any reference cached for this entry: the cached
  occurrences of leukodystrophy and cerebral atrophy sit in comparative passages
  about other sphingolipid and Golgi disorders (SPTLC1, ACER3, the golgipathy
  review), and the cached growth wording is in a general de-novo intellectual
  disability cohort paper that does not attribute it to this gene. Citing any of
  them here would attach a quote about a different disease to a CERT1 phenotype.
  Cerebral involvement remains curated at the pathophysiology layer as `Abnormal
  Cerebral Myelination and Atrophy`, and reduced growth remains inside the
  `Failure to thrive` description, until a source that names CERT1 is available.

  Deep research. Built from the Edison/falcon report
  research/Intellectual_Disability_Autosomal_Dominant_34-deep-research-falcon.md,
  which passed `just preflight-dr` against MONDO:0014599 with 27 CERT1 mentions.
  The report cites by author-year key with DOIs and carries no PMIDs, so every
  DOI was resolved to a PMID through the PMC ID converter and cited as a PMID.

  Report-proposed CURIEs that were wrong and had to be corrected. The report's
  own `## Term Validation` section reported all 49 of its CURIEs as resolved and
  flagged none of the three below, because each resolves to a real NCIT term -
  just not the one named. Verified with `runoak -i sqlite:obo:ncit`:
  `NCIT:C15329`, offered as "Physical Therapy", is Surgical Procedure - corrected
  to `NCIT:C15302`; `NCIT:C15337`, offered as "Occupational Therapy", is
  Thoracotomy - the correct term is `NCIT:C121351` (Occupational Therapy), which
  the entry now uses on its own Occupational Therapy treatment; `NCIT:C15345`,
  offered as "Speech Therapy", is Ureterostomy - corrected to `NCIT:C159273`
  (Speech Language Therapy). The report also gave two
  HP terms prose descriptions instead of labels (`HP:0001252` as "Frequently
  infantile, contributing to motor and feeding difficulty", which is Hypotonia;
  `HP:0001999` as "Variable facial, hand, and foot abnormalities", which is
  Abnormal facial shape - the label was re-derived from `cache/hp/terms.csv` and
  the term is now bound, correctly labelled, on the `Facial dysmorphism`
  phenotype); its own term validator did catch those two. Separately,
  `HP:0000708` is now labelled Atypical behavior in HPO, not Behavioral
  abnormality.

  Cohort frequencies, and a correction. The 31-person Gehin cohort
  (PMID:36976648) is cached as `full_text_xml` from PMC, and every per-phenotype
  denominator is quotable prose in the body of that cached record. The first
  version of this entry asserted the opposite: that the reference was cached
  `abstract_only` and that the counts lived only in the paper's tables. That was
  false, and it caused a real omission, because autism spectrum disorder at
  19 of 27 (70 percent) was left out on the strength of it. Both errors are
  corrected. The denominators now curated from the cached body are developmental
  delay 22/26, motor delay 26/29, seizures 16/29, autism spectrum disorder 19/27,
  stereotypical hand movements 14/18, self-injurious behaviour 9/19, high pain
  tolerance 9/18, disrupted sleep 9/21, attention deficit hyperactivity disorder
  10/19, aggression 6/20, neonatal feeding difficulty 15/24, and de novo origin
  in 93 percent (25 of 27). The general rule this entry got wrong: read
  `content_type:` in the cache frontmatter and grep the body before writing any
  note that says a figure cannot be sourced.

  Autism, and what the cohort paper actually concludes about it. ASD is the most
  frequent behavioural diagnosis in the cohort, but Gehin et al. searched the
  SPARK autism database and denovo-db and concluded that CERT1 is not a
  significant contributor to autism, that no individual in their cohort carried
  ASD as a primary diagnosis, and that CerTra syndrome is a neurodevelopmental
  syndrome distinct from ASD. The `Autism spectrum disorder` phenotype therefore
  carries three evidence items: the 19 of 27 denominator as SUPPORT, and both
  author conclusions as REFUTE, so the entry cannot be read as making CERT1 an
  autism gene.

  Report claims that did not survive checking. The report states that no
  disease-specific interventional ClinicalTrials.gov study was identified; that
  was re-checked independently on 2026-09-04 (ClinicalTrials.gov API v2, query
  "CERT1 OR CerTra syndrome") and confirmed - the single hit was an unrelated
  sleep-and-ceramides study in obesity. The report cites Arseni et al. 2018
  (`DOI:10.3390/ijms19051407`, PMID:29738498) as a source for CERT1 synonyms and
  behavioural features; that paper is a review of collagen disorders and appears
  in this report only because CERT1's former symbol was COL4A3BP, so it is not
  cited here. That exclusion was a curator judgement, not a validator finding.
  The one reference the report's own validator flagged as possibly off topic was
  `DOI:10.1002/anie.202413562`, the NanoBRET inhibitor-screening paper
  (PMID:39450584), and that flag was not followed: the paper is squarely on topic
  for CERT inhibitor development and is cited here on the
  `Pharmacological CERT Inhibition` treatment.

  GeneReviews. PubMed was searched for a GeneReviews chapter under "CERT1
  GeneReviews", "(ceramide transporter syndrome OR CerTra) AND GeneReviews" and
  "COL4A3BP AND GeneReviews" on 2026-09-04; all three returned zero results. No
  chapter exists, so there is no GeneReviews-tagged reference and no
  GeneReviews-derived phenotype baseline for this entry.

  Naming. CERT1 was COL4A3BP until 2019, so the founding literature - including
  the Hamdan candidate-gene report cited here - indexes it under the old symbol.
  Searching only "CERT1" misses it.

📚

References & Deep Research

References

8

PMID:36976648

CERT1 mutations perturb human development by disrupting sphingolipid homeostasis.

No top-level findings curated for this source.

PMID:33347465

Intellectual disability-associated gain-of-function mutations in CERT1 that encodes the ceramide transport protein CERT.

No top-level findings curated for this source.

PMID:34688657

Intellectual-disability-associated mutations in the ceramide transport protein gene CERT1 lead to aberrant function and subcellular distribution.

No top-level findings curated for this source.

PMID:31254361

Structure, functions and regulation of CERT, a lipid-transfer protein for the delivery of ceramide at the ER-Golgi membrane contact sites.

No top-level findings curated for this source.

PMID:25356899

De novo mutations in moderate or severe intellectual disability.

No top-level findings curated for this source.

PMID:42051775

Choroid plexus and perivascular space abnormalities in CerTra syndrome: neuroimaging and histological findings.

No top-level findings curated for this source.

PMID:39450584

Live-Cell Identification of Inhibitors of the Lipid Transfer Protein CERT Using Nanoluciferase Bioluminescence Resonance Energy Transfer (NanoBRET).

No top-level findings curated for this source.

PMID:30878996

Golgipathies in Neurodevelopment: A New View of Old Defects.

No top-level findings curated for this source.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Record notes

Curation provenance and known gaps. Phenotypes considered and left out. Cerebral atrophy and white-matter change (`HP:0002059`) and reduced growth or birth size (`HP:0001518`, `HP:0001507`) were both reviewed for the `phenotypes:` block and deliberately not added. Both are described in the deep-research report, but neither has a CERT1-specific quotable statement in any reference cached for this entry: the cached occurrences of leukodystrophy and cerebral atrophy sit in comparative passages about other sphingolipid and Golgi disorders (SPTLC1, ACER3, the golgipathy review), and the cached growth wording is in a general de-novo intellectual disability cohort paper that does not attribute it to this gene. Citing any of them here would attach a quote about a different disease to a CERT1 phenotype. Cerebral involvement remains curated at the pathophysiology layer as `Abnormal Cerebral Myelination and Atrophy`, and reduced growth remains inside the `Failure to thrive` description, until a source that names CERT1 is available. Deep research. Built from the Edison/falcon report research/Intellectual_Disability_Autosomal_Dominant_34-deep-research-falcon.md, which passed `just preflight-dr` against MONDO:0014599 with 27 CERT1 mentions. The report cites by author-year key with DOIs and carries no PMIDs, so every DOI was resolved to a PMID through the PMC ID converter and cited as a PMID. Report-proposed CURIEs that were wrong and had to be corrected. The report's own `## Term Validation` section reported all 49 of its CURIEs as resolved and flagged none of the three below, because each resolves to a real NCIT term - just not the one named. Verified with `runoak -i sqlite:obo:ncit`: `NCIT:C15329`, offered as "Physical Therapy", is Surgical Procedure - corrected to `NCIT:C15302`; `NCIT:C15337`, offered as "Occupational Therapy", is Thoracotomy - the correct term is `NCIT:C121351` (Occupational Therapy), which the entry now uses on its own Occupational Therapy treatment; `NCIT:C15345`, offered as "Speech Therapy", is Ureterostomy - corrected to `NCIT:C159273` (Speech Language Therapy). The report also gave two HP terms prose descriptions instead of labels (`HP:0001252` as "Frequently infantile, contributing to motor and feeding difficulty", which is Hypotonia; `HP:0001999` as "Variable facial, hand, and foot abnormalities", which is Abnormal facial shape - the label was re-derived from `cache/hp/terms.csv` and the term is now bound, correctly labelled, on the `Facial dysmorphism` phenotype); its own term validator did catch those two. Separately, `HP:0000708` is now labelled Atypical behavior in HPO, not Behavioral abnormality. Cohort frequencies, and a correction. The 31-person Gehin cohort (PMID:36976648) is cached as `full_text_xml` from PMC, and every per-phenotype denominator is quotable prose in the body of that cached record. The first version of this entry asserted the opposite: that the reference was cached `abstract_only` and that the counts lived only in the paper's tables. That was false, and it caused a real omission, because autism spectrum disorder at 19 of 27 (70 percent) was left out on the strength of it. Both errors are corrected. The denominators now curated from the cached body are developmental delay 22/26, motor delay 26/29, seizures 16/29, autism spectrum disorder 19/27, stereotypical hand movements 14/18, self-injurious behaviour 9/19, high pain tolerance 9/18, disrupted sleep 9/21, attention deficit hyperactivity disorder 10/19, aggression 6/20, neonatal feeding difficulty 15/24, and de novo origin in 93 percent (25 of 27). The general rule this entry got wrong: read `content_type:` in the cache frontmatter and grep the body before writing any note that says a figure cannot be sourced. Autism, and what the cohort paper actually concludes about it. ASD is the most frequent behavioural diagnosis in the cohort, but Gehin et al. searched the SPARK autism database and denovo-db and concluded that CERT1 is not a significant contributor to autism, that no individual in their cohort carried ASD as a primary diagnosis, and that CerTra syndrome is a neurodevelopmental syndrome distinct from ASD. The `Autism spectrum disorder` phenotype therefore carries three evidence items: the 19 of 27 denominator as SUPPORT, and both author conclusions as REFUTE, so the entry cannot be read as making CERT1 an autism gene. Report claims that did not survive checking. The report states that no disease-specific interventional ClinicalTrials.gov study was identified; that was re-checked independently on 2026-09-04 (ClinicalTrials.gov API v2, query "CERT1 OR CerTra syndrome") and confirmed - the single hit was an unrelated sleep-and-ceramides study in obesity. The report cites Arseni et al. 2018 (`DOI:10.3390/ijms19051407`, PMID:29738498) as a source for CERT1 synonyms and behavioural features; that paper is a review of collagen disorders and appears in this report only because CERT1's former symbol was COL4A3BP, so it is not cited here. That exclusion was a curator judgement, not a validator finding. The one reference the report's own validator flagged as possibly off topic was `DOI:10.1002/anie.202413562`, the NanoBRET inhibitor-screening paper (PMID:39450584), and that flag was not followed: the paper is squarely on topic for CERT inhibitor development and is cited here on the `Pharmacological CERT Inhibition` treatment. GeneReviews. PubMed was searched for a GeneReviews chapter under "CERT1 GeneReviews", "(ceramide transporter syndrome OR CerTra) AND GeneReviews" and "COL4A3BP AND GeneReviews" on 2026-09-04; all three returned zero results. No chapter exists, so there is no GeneReviews-tagged reference and no GeneReviews-derived phenotype baseline for this entry. Naming. CERT1 was COL4A3BP until 2019, so the founding literature - including the Hamdan candidate-gene report cited here - indexes it under the old symbol. Searching only "CERT1" misses it.

Create: Intellectual_Disability_Autosomal_Dominant_34 · 2026-09-04T05:33:56Z · View source

Created the MRD34 (CERT1 / CerTra syndrome) entry de novo from the Edison/falcon deep-research report research/Intellectual_Disability_Autosomal_Dominant_34-deep-research-falcon.md, which passed just preflight-dr against MONDO:0014599 with 27 CERT1 mentions. Modelled the mechanism as gain of function per the CLAUDE.md 'which slot?' rule: functional_impact_category: GAIN_OF_FUNCTION on the pathophysiology GeneticContext for the variant consequence, and modifier: GAIN_OF_FUNCTION on the GO:0120017 ceramide transfer activity node for the pathway activity state. Nine-node pathograph from the CERT1 autoregulatory-domain missense variant through loss of SRM phosphorylation-dependent autorepression, constitutive CERT activation, excess ER-to-Golgi ceramide transfer, increased sphingomyelin synthesis and dysregulated sphingolipid homeostasis to the neurodevelopmental node and the neuroimaging node; the last two are mechanism_confidence PROVISIONAL with INDIRECT_UNKNOWN_INTERMEDIATES edges because no human neural cell type has been implicated. Corrected three report-proposed NCIT CURIEs that resolve but name different concepts and that the report's own Term Validation section reported clean: NCIT:C15329 offered as Physical Therapy is Surgical Procedure (used NCIT:C15302), NCIT:C15337 offered as Occupational Therapy is Thoracotomy (not used), NCIT:C15345 offered as Speech Therapy is Ureterostomy (used NCIT:C159273 Speech Language Therapy). Also used the current HPO label Atypical behavior for HP:0000708. Every term was re-derived via runoak rather than copied from the report. The report cites only by DOI with no PMIDs; each DOI was resolved to a PMID through the PMC ID converter and cited as a PMID, and four further references were found by PubMed search (PMID:34688657 Tamura 2021, PMID:31254361 Hanada 2019, PMID:25356899 Hamdan 2014, PMID:42051775 Li 2026). Deliberately did not curate the Gehin cohort per-phenotype denominators (motor delay 26/29, autism 19/27, seizures 16/29, de novo 25/27) because PMID:36976648 is cached abstract_only and those figures are in the paper's tables; autism is therefore folded into a sourced Atypical behavior phenotype rather than asserted separately, and this gap is recorded in the entry notes. Independently re-checked two report claims: the no-interventional-trial claim was confirmed against the ClinicalTrials.gov API v2, and the off-topic Arseni 2018 collagen review was not cited. PubMed was searched three ways for a GeneReviews chapter (CERT1, CerTra/ceramide transporter syndrome, COL4A3BP) with zero results, so no GeneReviews tag was added. check-snippet-grading initially flagged one Gehin sentence that mixes a human severity finding with a Drosophila rescue result in a single sentence; it was re-quoted in two pieces so the human clause is HUMAN_CLINICAL and the Drosophila clause MODEL_ORGANISM, with no baseline edit. Validation: just validate PASS, just validate-disorders PASS, 73/73 snippets verified, and check-entity-refs, check-causal-targets, check-duplicate-keys, check-qualifier-terms (offline and --online), check-enum-values, check-folded-hyphens, check-snippet-length, check-title-snippets, check-snippet-grading, check-environmental-evidence, check-not4curation and check-term-cache-integrity all clean with no new findings. Deleted stubs/Intellectual_Disability_Autosomal_Dominant_34.yaml.

Falcon ▸

Intellectual Disability, Autosomal Dominant 34 (MRD34): Research Report

Edison Scientific Literature 18 citations 2026-09-03T20:45:40.006858

Intellectual Disability, Autosomal Dominant 34 (MRD34): Research Report

Executive summary

Intellectual disability, autosomal dominant 34 (MRD34) is an ultra-rare Mendelian neurodevelopmental disorder caused primarily by heterozygous gain-of-function variants in CERT1, the gene encoding ceramide transporter 1. The broader phenotype was renamed ceramide transporter (CerTra) syndrome after a 2023 international study characterized 31 unrelated affected individuals. Core manifestations are developmental delay, variable intellectual disability, marked speech and motor impairment, infantile hypotonia, autism or other behavioral abnormalities, seizures, feeding/growth problems, and occasionally abnormal cerebral myelination or atrophy. Most informative cases are caused by de novo missense variants that disrupt CERT autoregulation and sphingolipid homeostasis. There is no approved disease-modifying treatment; CERT inhibition has rescued abnormalities only in a Drosophila model. Epidemiology, long-term survival, validated biomarkers, and formal management guidelines remain unknown. (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb pages 2-3)

The following table summarizes the most actionable knowledge-base fields.

Knowledge-base field	Evidence status	Concise finding	Key evidence
Disease identity	Established disease-level classification	Intellectual disability, autosomal dominant 34 (MRD34); the expanded phenotype is termed ceramide transporter (CerTra) syndrome.	OMIM 616351; MONDO MONDO:0014599. Synonyms include autosomal dominant mental retardation 34 and CERT1-related intellectual disability. (rasika2019golgipathiesinneurodevelopment pages 5-9, OpenTargets Search: Intellectual disability, autosomal dominant 34, gehin2023cert1mutationsperturb pages 2-3)
Gene and locus	Established human genetic evidence	Heterozygous variants in CERT1 (historical symbol COL4A3BP; aliases CERT and GPBP), encoding ceramide transporter 1; locus 5q13; Ensembl ENSG00000113163.	OMIM gene 604677; Open Targets identifies a definitive monoallelic association. (OpenTargets Search: Intellectual disability, autosomal dominant 34, arseni2018fromstructureto pages 19-20)
Inheritance	Established human genetic evidence	Autosomal dominant, usually caused by a de novo heterozygous missense variant. In the largest cohort, 25/27 informative variants (93%) were de novo.	Gehin et al., May 15, 2023, DOI: 10.1172/JCI165019; PMID 36976648. (gehin2023cert1mutationsperturb pages 2-3)
Strongest cohort	Established human cohort evidence	The 2023 study analyzed 31 unrelated individuals with 22 distinct CERT1 missense variants, including 18 reportedly novel variants. Most variants, 27/31 (87%), occurred between the PH and C-terminal START-related domains.	Gehin et al., 2023, DOI: 10.1172/JCI165019. (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb pages 2-3)
Developmental phenotype	Established human cohort evidence	Motor delay occurred in 26/29 evaluable individuals; only 4/26 (15%) lacked developmental delay by the end of the first year. Intellectual disability ranged from mild to profound, with frequent severe speech impairment.	Gehin et al., 2023. (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb media 51f69b9d)
Behavioral phenotype	Established human cohort evidence	Autism spectrum disorder occurred in 19/27 (70%) evaluable individuals. Stereotypies, self-injury, ADHD, anxiety, aggression, sleep disruption, and increased pain tolerance were also reported.	Gehin et al., 2023; earlier reports described anxiety and self-mutilation. (arseni2018fromstructureto pages 19-20, gehin2023cert1mutationsperturb pages 3-5)
Neurologic phenotype	Established human cohort and case evidence	Seizures occurred in 16/29 evaluable individuals. Other findings included infantile hypotonia, thin or hypoplastic corpus callosum, ventriculomegaly, delayed myelination, cerebral or cerebellar atrophy, and leukodystrophy-like changes.	Gehin et al., 2023; Murakami et al., December 21, 2020, DOI: 10.1371/journal.pone.0243980; PMID 33347465. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8, gehin2023cert1mutationsperturb pages 3-5)
Variant hotspots	Established human genetic evidence	Variants cluster at p.S132, p.S135, p.S138, and p.S141 in the serine-repeat motif; p.T166; p.D240, p.G243, p.T247, and p.T251; and p.V326F, p.A329P, p.L330V, and p.L330P near the FFAT motif.	p.S132/p.S135 variants were associated with more severe presentations, although genotype groups were small. (gehin2023cert1mutationsperturb pages 3-5)
Variant-interpretation caution	Established segregation and functional evidence	Not every rare CERT1 variant is causal. c.2242_2243dupAA; p.(Pro749fs) was inherited and did not reproduce abnormal activity in functional testing, so it was judged noncausative in that family.	Tamura et al., October 22, 2021, DOI: 10.1016/j.jbc.2021.101338; PMID 34688657. (tamura2021intellectualdisabilityassociatedmutationsin pages 1-2)
Molecular mechanism	Demonstrated in biochemical and cellular models; clinical consequences partly inferred	CERT transfers ceramide from the endoplasmic reticulum to trans-Golgi contact sites for sphingomyelin synthesis. Disease variants impair phosphorylation-dependent autorepression or another regulatory domain, causing gain of function, excessive ceramide transport, altered sphingolipid flux, and abnormal punctate localization.	Murakami et al., 2020; Tamura et al., 2021; Gehin et al., 2023. (gehin2023cert1mutationsperturb pages 2-3, tamura2021intellectualdisabilityassociatedmutationsin pages 1-2, murakami2020intellectualdisabilityassociatedgainoffunction pages 11-13)
Diagnostic approach	Current clinical-genetics practice; no formal disease-specific criteria	Use an intellectual-disability or neurodevelopmental gene panel, preferably trio WES/WGS, with parental segregation and transcript-specific HGVS reporting. Apply ACMG/AMP criteria and interpret variants using population frequency, clustering, segregation, and functional evidence. MRI and EEG characterize complications but are not diagnostic biomarkers.	Published cohorts used exome sequencing, segregation analysis, ACMG interpretation, neurologic assessment, MRI, and EEG. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8, gehin2023cert1mutationsperturb pages 12-13, tamura2021intellectualdisabilityassociatedmutationsin pages 1-2)
Treatment status	No established disease-modifying human treatment	Care is supportive and individualized: developmental intervention, speech or augmentative communication, occupational and physical therapy, behavioral and sleep support, feeding care, and standard antiseizure treatment when required. No validated genotype-guided therapy or disease-specific interventional trial was identified.	Human reports provide no efficacy or safety evidence for CERT1-directed treatment. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8, gehin2023cert1mutationsperturb pages 12-13, gehin2023cert1mutationsperturb pages 2-3)
Experimental therapy	Preclinical only	The CERT inhibitor HPA-12 corrected locomotor and morphological abnormalities in a Drosophila model. This supports therapeutic plausibility but provides no human efficacy, safety, or dosing evidence.	Gehin et al., 2023. (gehin2023cert1mutationsperturb pages 2-3, gehin2023cert1mutationsperturb pages 10-12)
Model-organism evidence	Experimental Drosophila evidence	CERT gain of function in Drosophila melanogaster caused abnormal head or brain size and locomotor hypoactivity; pharmacologic rescue supports excessive CERT activity as the disease mechanism.	Gehin et al., 2023, DOI: 10.1172/JCI165019; PMID 36976648. (gehin2023cert1mutationsperturb pages 2-3, gehin2023cert1mutationsperturb pages 10-12)
Epidemiology	Major evidence gap	Prevalence, incidence, carrier frequency, founder effects, geographic enrichment, and sex ratio have not been established. Published cases are rare-disease referrals rather than a population-based cohort.	The largest available delineation included 31 unrelated individuals, without a population denominator. (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb pages 2-3)
Prognosis	Major evidence gap	The condition is chronic and lifelong with variable severity. Developmental slowing or regression may occur, and one severely affected adult had progressive leukodystrophy-like MRI changes. Survival, life expectancy, mortality, quality-of-life scores, and prognostic biomarkers remain unknown.	Human cohort and longitudinal single-case observations. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8, gehin2023cert1mutationsperturb pages 3-5)

Table: Concise evidence summary for CERT1-related CerTra syndrome, covering identity, genetics, cohort statistics, phenotype, mechanism, diagnosis, treatment, models, and major knowledge gaps. Evidence is explicitly distinguished as established human, experimental, inferred, or unavailable.

1. Disease information

Definition and identifiers

MRD34 is a syndromic neurodevelopmental disorder in which pathogenic monoallelic CERT1 variants impair intellectual and adaptive development. The 2023 expanded phenotype encompasses neurologic, behavioral, growth, and mild dysmorphic manifestations and is termed CerTra syndrome. (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb pages 2-3)

MONDO: MONDO:0014599.
OMIM phenotype: 616351.
OMIM gene: CERT1/COL4A3BP, 604677.
Gene: CERT1; Ensembl ENSG00000113163; historical symbol COL4A3BP; aliases CERT, GPBP, and STARD11.
Locus: 5q13.
Synonyms: intellectual disability, autosomal dominant 34; autosomal dominant mental retardation 34; MRD34; CERT1-related intellectual disability; CERT1-related neurodevelopmental disorder; ceramide transporter syndrome/CerTra syndrome. (OpenTargets Search: Intellectual disability, autosomal dominant 34, rasika2019golgipathiesinneurodevelopment pages 5-9, arseni2018fromstructureto pages 19-20)
ICD/MeSH: No uniquely specific ICD-10, ICD-11, or MeSH code was established in the retrieved evidence. Coding generally falls under intellectual-developmental disorder, with separate codes for epilepsy, autism, feeding difficulty, and other manifestations.

The evidence is aggregated disease-level evidence assembled from international research cohorts, ClinVar/DECIPHER/GeneMatcher-type resources, and published case reports—not longitudinal EHR-derived population data. The principal cohort consists of highly selected rare-disease referrals and should not be interpreted as population surveillance. (gehin2023cert1mutationsperturb pages 2-3, gehin2023cert1mutationsperturb pages 12-13)

2. Etiology, risks, and protective factors

Causal factor

The initiating cause is usually a germline heterozygous missense variant in CERT1. Of 27 affected individuals with informative parental data in the 2023 cohort, 25 variants were de novo (93%). One variant was inherited from an apparently unaffected father and another from a mother with intellectual disability, indicating possible reduced penetrance, very mild expression, or uncertainty for individual alleles. (gehin2023cert1mutationsperturb pages 2-3)

The best-supported molecular class is gain of function, not simple haploinsufficiency: pathogenic variants impair phosphorylation-dependent or structural autoregulation, leaving CERT excessively active. An arbitrary rare CERT1 variant is therefore insufficient for diagnosis. A C-terminal frameshift, c.2242_2243dupAA; p.(Pro749fs), segregated away from disease and behaved like a negative control in functional experiments. (tamura2021intellectualdisabilityassociatedmutationsin pages 1-2)

Risk, protective, and gene–environment factors

Genetic risk: a pathogenic/likely pathogenic heterozygous CERT1 allele, particularly a de novo missense change in a demonstrated regulatory cluster.
Modifiers: no validated modifier genes, polygenic scores, protective alleles, founder variants, or susceptibility loci are known.
Environmental/lifestyle risks: no toxin, diet, occupation, smoking, alcohol, radiation, or infectious agent is established as causal or penetrance-modifying.
Potential triggers: influenza preceded seizure onset in one patient, but this is temporal case-level evidence and does not establish a gene–infection interaction. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8)
Protective factors: none demonstrated in humans. Pharmacological CERT inhibition is protective only in an experimental fly model. (gehin2023cert1mutationsperturb pages 2-3, gehin2023cert1mutationsperturb pages 10-12)

3. Phenotypes

The strongest frequency estimates come from the 31-person 2023 cohort. Denominators vary because not every characteristic was available for every patient. (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb pages 2-3)

Phenotype	Characterization and frequency	Suggested HPO term
Global developmental delay	Usually apparent during infancy; only 4/26 individuals (15%) lacked developmental delay by the end of year one. Chronic, variable, and sometimes followed by slowing/regression.	HP:0001263
Motor delay	26/29; severity ranged from mild delay to supported walking or persistent immobility.	HP:0001270; HP:0002062 delayed walking
Intellectual disability	Mild to profound. p.S132/p.S135 cases were generally most severe; one p.S135P adult had IQ <35 in childhood.	HP:0001249; HP:0010864 severe ID; HP:0002187 profound ID
Speech/language delay	Common and often severe; meaningful speech may remain absent in profoundly affected patients.	HP:0000750; HP:0001344 absent speech
Autism spectrum disorder	19/27 (70%).	HP:0000717
Behavioral abnormalities	Stereotypies, self-injury, ADHD, anxiety, aggression, sleep disruption, and increased pain tolerance. Frequencies were not consistently supplied.	HP:0000708, HP:0000733, HP:0000716, HP:0000729, HP:0002360, HP:0007328
Seizures/epilepsy	16/29; variable severity. Some recurrent-variant groups had no seizures, whereas severe epileptic encephalopathy occurred in an outlier with p.T166A.	HP:0001250; HP:0001251
Hypotonia	Frequently infantile, contributing to motor and feeding difficulty.	HP:0001252
Feeding difficulty/failure to thrive	Neonatal feeding problems and failure to thrive are especially prominent with p.S132/p.S135 variants.	HP:0011968; HP:0001508
Growth abnormalities	Small size at birth or acquired growth delay in some patients; neither universal nor quantified across all cases.	HP:0001518; HP:0001507
Mild dysmorphism	Variable facial, hand, and foot abnormalities; no single pathognomonic gestalt.	HP:0001999
Neuroimaging abnormalities	Thin/hypoplastic corpus callosum, ventriculomegaly, delayed myelination, cerebral/cerebellar atrophy, or leukodystrophy-like change in subsets.	HP:0002079, HP:0002119, HP:0002410, HP:0002059

The severe p.S132L group was small at birth, had perinatal difficulty and failure to thrive, attained sitting at approximately 3–4 years, and might walk with support at 7–8 years before becoming immobile in late adolescence. p.S138C was associated with milder motor and speech delay and no seizures in two reported individuals. These correlations involve only two to four people per recurrent variant and remain preliminary. (gehin2023cert1mutationsperturb media 51f69b9d, gehin2023cert1mutationsperturb media ad12d9c6, gehin2023cert1mutationsperturb media 91444d58)

Quality-of-life instruments such as EQ-5D, SF-36, or PROMIS have not been reported. Nonetheless, severe limitations in communication, independent mobility, learning, adaptive behavior, feeding, sleep, and seizure control imply substantial lifelong effects on autonomy and caregiver burden. That impact is a clinical inference rather than a measured disease-specific utility estimate. (gehin2023cert1mutationsperturb pages 3-5, murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8)

4. Genetic and molecular information

Gene and variant architecture

The 2023 study reported 31 unrelated individuals, 22 distinct missense variants, and 18 apparently novel variants. Twenty-seven of 31 variants (87%) lay between the N-terminal PH domain and C-terminal START-related domain. Four clusters were emphasized:

The serine-repeat regulatory region: p.S132, p.S135, p.S138, p.S141.
p.T166.
p.D240, p.G243, p.T247, p.T251.
The FFAT-region cluster: p.V326F, p.A329P, p.L330V, p.L330P. (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb media 51f69b9d)

A primary case report identified de novo NM_001130105.1:c.787T>C, p.(Ser263Pro), corresponding to c.403T>C, p.(Ser135Pro) under another transcript/protein isoform. This discrepancy illustrates why clinical reports must state transcript accession and version. The allele was absent from gnomAD and jMorp and was classified as pathogenic under ACMG criteria. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8)

All well-supported disease alleles are constitutional/germline. No somatic CERT1 mechanism is established. The reported pathogenic missense variants are generally absent or extremely rare in population databases; a universal allele-frequency threshold cannot substitute for mechanism-aware interpretation. Open Targets also records a stop-gained allele and several missense records, but database assertions need case-level and segregation review. (OpenTargets Search: Intellectual disability, autosomal dominant 34)

Functional consequence and modifiers

Pathogenic variants cause abnormally increased CERT activity, impaired serine-repeat hyperphosphorylation, altered intracellular localization, or disruption of a newly characterized dimeric helical regulatory domain. S132L, S135 substitutions, and G243R are experimentally supported gain-of-function alleles. No established modifier genes or disease-specific epigenetic signature has been reported. No recurrent pathogenic chromosome-scale deletion, translocation, inversion, or aneuploidy defines MRD34. (gehin2023cert1mutationsperturb pages 2-3, tamura2021intellectualdisabilityassociatedmutationsin pages 1-2, murakami2020intellectualdisabilityassociatedgainoffunction pages 11-13)

5. Environmental information

MRD34 is a primary genetic disorder. No infectious organism, toxic exposure, pollution source, occupational factor, radiation exposure, dietary deficiency, smoking, alcohol use, or exercise pattern has been shown to cause it. General environmental and educational circumstances may affect developmental attainment and quality of life, as in other neurodevelopmental disorders, but no CERT1-specific gene–environment interaction has been demonstrated.

6. Mechanism and pathophysiology

Ordered causal chain

A heterozygous regulatory CERT1 missense variant leads to defective phosphorylation-dependent or structural autoregulation of CERT.
Failed autoregulation results in excessive CERT activation and abnormal punctate localization at ER–Golgi contact machinery.
Excess CERT activity leads to increased nonvesicular transfer of ceramide from the endoplasmic reticulum to the trans-Golgi.
Increased ceramide delivery results in excessive or compositionally skewed sphingomyelin/sphingolipid synthesis and altered lipid homeostasis.
Altered sphingolipid flux is inferred to disrupt membrane composition, organelle communication, neural differentiation, synaptic transmission, action-potential propagation, and/or myelin biology; the precise vulnerable human neural cell type remains unproved.
Neural developmental dysfunction leads to hypotonia, impaired cognition, speech and motor delay, autism-related behavior, and seizures.
Branch: severe or prolonged lipid dysregulation may lead to abnormal myelination and cerebral/cerebellar atrophy; this link is supported by human imaging but remains mechanistically inferred.
Experimental intervention branch: CERT inhibition with HPA-12 reduces excessive CERT activity and results in rescue of morphological and locomotor abnormalities in Drosophila, but has not been tested therapeutically in affected humans. (gehin2023cert1mutationsperturb pages 2-3, tamura2021intellectualdisabilityassociatedmutationsin pages 1-2, gehin2023cert1mutationsperturb pages 10-12, gehin2023cert1mutationsperturb pages 3-5)

CERT normally binds trans-Golgi phosphatidylinositol-4-phosphate through its PH domain, ER VAP proteins through its FFAT motif, and ceramide through its START-related domain. Multisite phosphorylation of the serine-repeat motif downregulates transport when cellular sphingomyelin requirements have been met. The disease therefore represents dysregulated ER–Golgi membrane-contact-site lipid transport, not a conventional lysosomal sphingolipidosis. (rasika2019golgipathiesinneurodevelopment pages 5-9, murakami2020intellectualdisabilityassociatedgainoffunction pages 11-13)

Suggested GO biological processes: ceramide transport (GO:0035627), sphingomyelin biosynthetic process (GO:0006686), sphingolipid metabolic process (GO:0006665), lipid transport (GO:0006869), ER-to-Golgi transport, regulation of protein phosphorylation, nervous-system development (GO:0007399), and myelination (GO:0042552). Suggested cellular components are endoplasmic-reticulum membrane (GO:0005789), Golgi membrane (GO:0000139), trans-Golgi network (GO:0005802), membrane contact site (GO:0044232), and cytosol (GO:0005829).

Candidate Cell Ontology annotations: neuron (CL:0000540), neural progenitor cell (CL:0011020), oligodendrocyte (CL:0000128), astrocyte (CL:0000127), and Schwann cell (CL:0002573). These are biologically plausible targets; the retrieved human studies do not establish one primary cell type.

No disease-specific immune mechanism, oxidative injury cascade, validated transcriptomic signature, patient proteomic biomarker, metabolomic diagnostic panel, single-cell atlas, spatial transcriptomic dataset, organoid study, or human CRISPR screen was established. Lipidomic and biochemical experiments support sphingolipid disequilibrium, but clinical metabolomic validation is lacking. (gehin2023cert1mutationsperturb pages 2-3)

A concise exact abstract quotation from Murakami et al. is: “These results identified specific ID-associated CERT1 mutations that induced gain-of-function effects on CERT activity.” The paper was published December 21, 2020; DOI 10.1371/journal.pone.0243980, PMID 33347465. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8, murakami2020intellectualdisabilityassociatedgainoffunction pages 11-13)

7. Anatomical structures affected

Primary organ/system: central nervous system, especially the developing brain (UBERON:0000955) and cerebral cortex (UBERON:0000956).
White matter/myelin: cerebral white matter (UBERON:0002437), corpus callosum (UBERON:0002336), and cerebellum (UBERON:0002037) may be abnormal on MRI.
Functional neural systems: cognitive, language, motor, behavioral, sensory/pain-processing, and epileptic networks.
Secondary structures: skeletal growth, face, hands, and feet may show mild nonspecific abnormalities; gastrointestinal/oromotor function is implicated by feeding difficulty.
Subcellular structures: ER membrane, trans-Golgi membrane, and ER–Golgi contact sites are directly involved.

Findings are generally bilateral/systemic rather than consistently lateralized. No reproducible unilateral lesion is known. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8, gehin2023cert1mutationsperturb pages 3-5)

8. Temporal development

Onset is congenital or in early infancy. Some infants are small at birth or have perinatal feeding difficulty and hypotonia; others have normal birth parameters and become recognizable through delayed milestones during the first years. p.S132/p.S135 variants tend toward congenital/perinatal severity, whereas p.S138, p.T166, and p.G243 may present with later slowing or regression. (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb media 91444d58)

The disease is chronic and lifelong. Course ranges from relatively stable mild disability to severe developmental impairment, loss of mobility, seizure-associated worsening, or progressive neuroimaging abnormalities. In one woman with p.S135P, delayed myelination and corpus-callosum hypoplasia at age five evolved into frontal-predominant leukodystrophy/general cerebral atrophy by age 23. That single trajectory cannot establish universal neurodegeneration. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8)

No standardized disease stages, remission pattern, or quantified progression rate exists. Early childhood is the probable critical window for developmental intervention and any future lipid-normalizing therapy, but the latter remains an inference.

9. Inheritance and population

Inheritance is autosomal dominant, predominantly de novo. If a parent carries a pathogenic allele, the theoretical transmission probability is 50% per pregnancy, although severity may be unpredictable because expressivity is variable. For an apparently de novo case, recurrence risk is low but not zero because parental germline mosaicism has not been systematically excluded. (gehin2023cert1mutationsperturb pages 2-3, gehin2023cert1mutationsperturb pages 12-13)

Penetrance is not formally quantified. The apparently unaffected father who transmitted p.V326F raises the possibility of reduced penetrance or uncertain pathogenicity, while maternal transmission of p.A449V from a mother with intellectual disability supports variable expressivity. No anticipation, founder effect, consanguinity association, carrier frequency, ethnic enrichment, geographic concentration, or sex-ratio difference is established. (gehin2023cert1mutationsperturb pages 2-3, gehin2023cert1mutationsperturb pages 10-12)

Prevalence and incidence are unknown. The 31-person international cohort has no population denominator and cannot yield cases per 100,000. The condition is likely ultra-rare and underdiagnosed, particularly among individuals previously labeled with nonspecific developmental delay or intellectual disability.

10. Diagnostics

Recommended approach

Establish the neurodevelopmental phenotype using standardized cognitive, adaptive, language, motor, autism, and behavioral assessment.
Perform trio WES/WGS or a comprehensive neurodevelopmental/intellectual-disability panel including CERT1. Trio analysis is particularly informative because most pathogenic alleles are de novo.
Confirm the allele and parental segregation by orthogonal sequencing; report the exact transcript.
Apply ACMG/AMP criteria with attention to population absence, de novo status, regulatory-domain clustering, prior affected individuals, phenotype match, and available functional evidence.
Avoid assuming haploinsufficiency: truncating or C-terminal variants require careful segregation and functional evaluation.
Use brain MRI, EEG, hearing/vision assessment, feeding evaluation, and growth monitoring to define complications—not to confirm the molecular diagnosis. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8, gehin2023cert1mutationsperturb pages 12-13, tamura2021intellectualdisabilityassociatedmutationsin pages 1-2)

Routine ammonia, lactate, thyroid/liver studies, blood gases, amino acids, acylcarnitine/tandem mass spectrometry, and urine organic acids were normal in one investigated patient; no diagnostic blood, urine, enzyme, or CSF biomarker is validated. (tamura2021intellectualdisabilityassociatedmutationsin pages 1-2)

CMA is reasonable early testing for unexplained developmental disability but will generally not detect a single-nucleotide CERT1 gain-of-function allele. Karyotyping and FISH have no disease-specific role unless a chromosomal rearrangement is independently suspected. Mitochondrial DNA and repeat-expansion testing are phenotype-driven differentials, not direct tests for MRD34. RNA sequencing, proteomics, lipidomics, and cellular CERT-localization assays remain research-level tools.

Differential diagnosis

The differential includes other monogenic developmental epileptic encephalopathies, autism–ID syndromes, hypomyelinating/leukodystrophy disorders, cerebral palsy, chromosomal copy-number disorders, congenital disorders of glycosylation, mitochondrial disease, and other sphingolipid-metabolism disorders. CERT1 should be prioritized when ID and severe speech/motor delay coexist with hypotonia, autism/stereotypies, increased pain tolerance, feeding/growth problems, seizures, and a thin corpus callosum or delayed myelination.

No population newborn screen or biochemical carrier screen exists. Cascade sequencing is appropriate after identifying a familial pathogenic variant. Prenatal diagnosis or PGT-M is technically possible once a familial pathogenic allele is established, but no MRD34-specific outcome guideline was identified.

11. Outcome and prognosis

The reported range is broad—from mild ID with delayed milestones to profound disability, absent speech, epilepsy, immobility, and progressive cerebral imaging abnormalities. p.S132/p.S135 variants appear more severe, but recurrent-variant samples are too small for reliable individual prediction. Seizure burden may worsen function in some patients. (gehin2023cert1mutationsperturb media 91444d58, gehin2023cert1mutationsperturb pages 3-5)

No five- or ten-year survival estimates, life expectancy, standardized mortality rate, disease-specific cause-of-death profile, validated prognostic biomarker, recovery percentage, or formal quality-of-life score is available. MRD34 itself has not been shown to shorten lifespan, but absence of evidence should not be interpreted as normal life expectancy. Developmental disability is generally lifelong; therapies may improve function and participation but are not known to reverse the genetic disorder.

12. Treatment and real-world management

There is no approved CERT1-specific therapy and no relevant disease-specific interventional ClinicalTrials.gov study was identified by the tool searches. Current implementation is supportive and phenotype directed:

early developmental and special-education services;
speech-language therapy and augmentative/alternative communication;
physical and occupational therapy, mobility equipment, and contracture prevention;
standard antiseizure medication selected by seizure type;
autism/behavioral assessment and evidence-based behavioral support;
sleep evaluation and treatment;
feeding/swallowing and nutritional support;
hearing, vision, orthopedic, growth, and neurologic surveillance;
family psychosocial support and genetic counseling. (murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8, gehin2023cert1mutationsperturb pages 12-13)

Suggested NCIt concepts include Physical Therapy (C15329), Occupational Therapy (C15337), Speech Therapy (C15345), Supportive Care (C15747), genetic counseling, and anticonvulsant therapy. These are ontology mappings, not MRD34-specific efficacy endorsements.

HPA-12 and other CERT inhibitors are experimental. HPA-12 corrected fly locomotor and morphologic abnormalities, supplying target-validation evidence but no human dose, safety, CNS-penetration, developmental-toxicity, or response-rate data. CERT is fundamental to membrane lipid homeostasis, so over-inhibition could itself be harmful. No gene therapy, CRISPR, ASO, siRNA, mRNA, cell therapy, immunotherapy, surgery, pharmacogenomic algorithm, or validated combination regimen exists. (gehin2023cert1mutationsperturb pages 2-3, gehin2023cert1mutationsperturb pages 10-12, murakami2020intellectualdisabilityassociatedgainoffunction pages 11-13)

A 2024 technology development created a live-cell NanoBRET assay and screened 140 HPA-12 derivatives, identifying six compounds superior in dose-response and orthogonal lipidomic assays. This is a drug-discovery platform, not testing in CerTra patients. DOI: 10.1002/anie.202413562, published November 2024.

13. Prevention

Primary prevention through lifestyle or vaccination is not applicable to a spontaneous Mendelian variant. Reproductive prevention options are nondirective genetic counseling, parental testing, PGT-M, chorionic-villus/amniotic-fluid diagnosis, or donor gametes after a pathogenic familial allele is confirmed. Residual recurrence risk from parental gonadal mosaicism should be discussed even after an apparently de novo result.

Secondary prevention consists of early molecular diagnosis, early developmental intervention, prompt seizure recognition, and early feeding/hearing/vision assessment. Tertiary prevention includes seizure control, aspiration and malnutrition prevention, mobility/contracture management, communication support, behavioral and sleep care, and caregiver support. No vaccine, medication prophylaxis, or population screening program prevents MRD34.

14. Other species and natural disease

No naturally occurring CERT1-associated veterinary counterpart, affected breed, zoonotic transmission, or cross-species infectious susceptibility was identified. Relevant taxa include Homo sapiens (NCBI Taxon 9606) and the experimental fruit fly Drosophila melanogaster (NCBI Taxon 7227). CERT-mediated sphingolipid transport is evolutionarily conserved, permitting mechanistic modeling, but a manipulated fly phenotype is not a naturally occurring animal disease.

15. Model organisms and experimental systems

The principal in vivo disease model is transgenic Drosophila melanogaster expressing gain-of-function CERT. It reproduces abnormal head/brain size and locomotor hypoactivity and is pharmacologically rescuable with HPA-12, supporting causal excess CERT activity. Its limitations are major differences in brain architecture, development, cognition, drug metabolism, and sphingolipid composition; it cannot model human language, adaptive behavior, or the full epilepsy phenotype. (gehin2023cert1mutationsperturb pages 2-3, gehin2023cert1mutationsperturb pages 10-12)

Cellular models expressing S132L, S135 substitutions, or G243R reproduce deficient SRM hyperphosphorylation, excess CERT activity, increased sphingomyelin synthesis, and punctate ER/Golgi-associated localization. The nonsegregating Pro749fs construct behaved as a useful negative control. These systems are suited to variant classification, lipidomics, structure–function analysis, and inhibitor screening but do not reproduce developing human neural circuitry. (tamura2021intellectualdisabilityassociatedmutationsin pages 1-2, murakami2020intellectualdisabilityassociatedgainoffunction pages 11-13)

No validated Cert1 knock-in mouse, rat, zebrafish, patient-derived iPSC-neuron, cerebral-organoid, conditional neural model, or humanized model was established in the retrieved disease-specific evidence.

Evidence appraisal and recent developments

The decisive recent development was Gehin et al., published May 15, 2023 in the Journal of Clinical Investigation (PMID 36976648; DOI 10.1172/JCI165019). It expanded the disorder from isolated cases to 31 unrelated individuals, identified recurrent regulatory clusters, quantified core manifestations, established altered sphingolipid homeostasis, and demonstrated pharmacological rescue in flies. The authors’ central interpretation is that CERT1 mutations “perturb human development by disrupting sphingolipid homeostasis.” (gehin2023cert1mutationsperturb pages 3-5, gehin2023cert1mutationsperturb pages 2-3)

Mechanistic confidence is high that selected variants cause CERT gain of function; confidence is moderate that altered neural sphingolipid homeostasis directly produces every clinical manifestation; and confidence is low regarding variant-specific prognosis, penetrance, population prevalence, and therapeutic translation. The most important next steps are prospective natural-history studies, standardized phenotyping and quality-of-life measurement, patient-cell or iPSC-neuron lipidomics, mammalian knock-in models, CNS pharmacology/toxicology of partial CERT inhibition, and a curated mechanism-aware variant-classification framework.

References

(gehin2023cert1mutationsperturb pages 3-5): Charlotte Gehin, Museer A. Lone, Winston Lee, Laura Capolupo, Sylvia Ho, Adekemi M. Adeyemi, Erica H. Gerkes, Alexander P.A. Stegmann, Estrella López-Martín, Eva Bermejo-Sánchez, Beatriz Martínez-Delgado, Christiane Zweier, Cornelia Kraus, Bernt Popp, Vincent Strehlow, Daniel Gräfe, Ina Knerr, Eppie R. Jones, Stefano Zamuner, Luciano A. Abriata, Vidya Kunnathully, Brandon E. Moeller, Anthony Vocat, Samuel Rommelaere, Jean-Philippe Bocquete, Evelyne Ruchti, Greta Limoni, Marine Van Campenhoudt, Samuel Bourgeat, Petra Henklein, Christian Gilissen, Bregje W. van Bon, Rolph Pfundt, Marjolein H. Willemsen, Jolanda H. Schieving, Emanuela Leonardi, Fiorenza Soli, Alessandra Murgia, Hui Guo, Qiumeng Zhang, Kun Xia, Christina R. Fagerberg, Christoph P. Beier, Martin J. Larsen, Irene Valenzuela, Paula Fernández-Álvarez, Shiyi Xiong, Robert Śmigiel, Vanesa López-González, Lluís Armengol, Manuela Morleo, Angelo Selicorni, Annalaura Torella, Moira Blyth, Nicola S. Cooper, Valerie Wilson, Renske Oegema, Yvan Herenger, Aurore Garde, Ange-Line Bruel, Frederic Tran Mau-Them, Alexis B.R. Maddocks, Jennifer M. Bain, Musadiq A. Bhat, Gregory Costain, Peter Kannu, Ashish Marwaha, Neena L. Champaigne, Michael J. Friez, Ellen B. Richardson, Vykuntaraju K. Gowda, Varunvenkat M. Srinivasan, Yask Gupta, Tze Y. Lim, Simone Sanna-Cherchi, Bruno Lemaitre, Toshiyuki Yamaji, Kentaro Hanada, John E. Burke, Ana Marjia Jakšić, Brian D. McCabe, Paolo De Los Rios, Thorsten Hornemann, Giovanni D’Angelo, and Vincenzo A. Gennarino. Cert1 mutations perturb human development by disrupting sphingolipid homeostasis. Journal of Clinical Investigation, May 2023. URL: https://doi.org/10.1172/jci165019, doi:10.1172/jci165019. This article has 37 citations and is from a highest quality peer-reviewed journal.
(gehin2023cert1mutationsperturb pages 2-3): Charlotte Gehin, Museer A. Lone, Winston Lee, Laura Capolupo, Sylvia Ho, Adekemi M. Adeyemi, Erica H. Gerkes, Alexander P.A. Stegmann, Estrella López-Martín, Eva Bermejo-Sánchez, Beatriz Martínez-Delgado, Christiane Zweier, Cornelia Kraus, Bernt Popp, Vincent Strehlow, Daniel Gräfe, Ina Knerr, Eppie R. Jones, Stefano Zamuner, Luciano A. Abriata, Vidya Kunnathully, Brandon E. Moeller, Anthony Vocat, Samuel Rommelaere, Jean-Philippe Bocquete, Evelyne Ruchti, Greta Limoni, Marine Van Campenhoudt, Samuel Bourgeat, Petra Henklein, Christian Gilissen, Bregje W. van Bon, Rolph Pfundt, Marjolein H. Willemsen, Jolanda H. Schieving, Emanuela Leonardi, Fiorenza Soli, Alessandra Murgia, Hui Guo, Qiumeng Zhang, Kun Xia, Christina R. Fagerberg, Christoph P. Beier, Martin J. Larsen, Irene Valenzuela, Paula Fernández-Álvarez, Shiyi Xiong, Robert Śmigiel, Vanesa López-González, Lluís Armengol, Manuela Morleo, Angelo Selicorni, Annalaura Torella, Moira Blyth, Nicola S. Cooper, Valerie Wilson, Renske Oegema, Yvan Herenger, Aurore Garde, Ange-Line Bruel, Frederic Tran Mau-Them, Alexis B.R. Maddocks, Jennifer M. Bain, Musadiq A. Bhat, Gregory Costain, Peter Kannu, Ashish Marwaha, Neena L. Champaigne, Michael J. Friez, Ellen B. Richardson, Vykuntaraju K. Gowda, Varunvenkat M. Srinivasan, Yask Gupta, Tze Y. Lim, Simone Sanna-Cherchi, Bruno Lemaitre, Toshiyuki Yamaji, Kentaro Hanada, John E. Burke, Ana Marjia Jakšić, Brian D. McCabe, Paolo De Los Rios, Thorsten Hornemann, Giovanni D’Angelo, and Vincenzo A. Gennarino. Cert1 mutations perturb human development by disrupting sphingolipid homeostasis. Journal of Clinical Investigation, May 2023. URL: https://doi.org/10.1172/jci165019, doi:10.1172/jci165019. This article has 37 citations and is from a highest quality peer-reviewed journal.
(rasika2019golgipathiesinneurodevelopment pages 5-9): Sowmyalakshmi Rasika, Sandrine Passemard, Alain Verloes, Pierre Gressens, and Vincent El Ghouzzi. Golgipathies in neurodevelopment: a new view of old defects. Developmental Neuroscience, 40:396-416, Mar 2019. URL: https://doi.org/10.1159/000497035, doi:10.1159/000497035. This article has 60 citations and is from a peer-reviewed journal.
(OpenTargets Search: Intellectual disability, autosomal dominant 34): Open Targets Query (Intellectual disability, autosomal dominant 34, 2 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(arseni2018fromstructureto pages 19-20): Lavinia Arseni, Anita Lombardi, and Donata Orioli. From structure to phenotype: impact of collagen alterations on human health. May 2018. URL: https://doi.org/10.3390/ijms19051407, doi:10.3390/ijms19051407. This article has 250 citations.
(gehin2023cert1mutationsperturb media 51f69b9d): Charlotte Gehin, Museer A. Lone, Winston Lee, Laura Capolupo, Sylvia Ho, Adekemi M. Adeyemi, Erica H. Gerkes, Alexander P.A. Stegmann, Estrella López-Martín, Eva Bermejo-Sánchez, Beatriz Martínez-Delgado, Christiane Zweier, Cornelia Kraus, Bernt Popp, Vincent Strehlow, Daniel Gräfe, Ina Knerr, Eppie R. Jones, Stefano Zamuner, Luciano A. Abriata, Vidya Kunnathully, Brandon E. Moeller, Anthony Vocat, Samuel Rommelaere, Jean-Philippe Bocquete, Evelyne Ruchti, Greta Limoni, Marine Van Campenhoudt, Samuel Bourgeat, Petra Henklein, Christian Gilissen, Bregje W. van Bon, Rolph Pfundt, Marjolein H. Willemsen, Jolanda H. Schieving, Emanuela Leonardi, Fiorenza Soli, Alessandra Murgia, Hui Guo, Qiumeng Zhang, Kun Xia, Christina R. Fagerberg, Christoph P. Beier, Martin J. Larsen, Irene Valenzuela, Paula Fernández-Álvarez, Shiyi Xiong, Robert Śmigiel, Vanesa López-González, Lluís Armengol, Manuela Morleo, Angelo Selicorni, Annalaura Torella, Moira Blyth, Nicola S. Cooper, Valerie Wilson, Renske Oegema, Yvan Herenger, Aurore Garde, Ange-Line Bruel, Frederic Tran Mau-Them, Alexis B.R. Maddocks, Jennifer M. Bain, Musadiq A. Bhat, Gregory Costain, Peter Kannu, Ashish Marwaha, Neena L. Champaigne, Michael J. Friez, Ellen B. Richardson, Vykuntaraju K. Gowda, Varunvenkat M. Srinivasan, Yask Gupta, Tze Y. Lim, Simone Sanna-Cherchi, Bruno Lemaitre, Toshiyuki Yamaji, Kentaro Hanada, John E. Burke, Ana Marjia Jakšić, Brian D. McCabe, Paolo De Los Rios, Thorsten Hornemann, Giovanni D’Angelo, and Vincenzo A. Gennarino. Cert1 mutations perturb human development by disrupting sphingolipid homeostasis. Journal of Clinical Investigation, May 2023. URL: https://doi.org/10.1172/jci165019, doi:10.1172/jci165019. This article has 37 citations and is from a highest quality peer-reviewed journal.
(murakami2020intellectualdisabilityassociatedgainoffunction pages 5-8): Hiroaki Murakami, Norito Tamura, Yumi Enomoto, Kentaro Shimasaki, Kenji Kurosawa, and Kentaro Hanada. Intellectual disability-associated gain-of-function mutations in cert1 that encodes the ceramide transport protein cert. PLoS ONE, 15:e0243980, Dec 2020. URL: https://doi.org/10.1371/journal.pone.0243980, doi:10.1371/journal.pone.0243980. This article has 33 citations and is from a peer-reviewed journal.
(tamura2021intellectualdisabilityassociatedmutationsin pages 1-2): Norito Tamura, Shota Sakai, Loreto Martorell, Roser Colomé, Aya Mizuike, Asako Goto, Juan Darío Ortigoza-Escobar, and Kentaro Hanada. Intellectual-disability-associated mutations in the ceramide transport protein gene cert1 lead to aberrant function and subcellular distribution. Nov 2021. URL: https://doi.org/10.1016/j.jbc.2021.101338, doi:10.1016/j.jbc.2021.101338. This article has 20 citations and is from a domain leading peer-reviewed journal.
(murakami2020intellectualdisabilityassociatedgainoffunction pages 11-13): Hiroaki Murakami, Norito Tamura, Yumi Enomoto, Kentaro Shimasaki, Kenji Kurosawa, and Kentaro Hanada. Intellectual disability-associated gain-of-function mutations in cert1 that encodes the ceramide transport protein cert. PLoS ONE, 15:e0243980, Dec 2020. URL: https://doi.org/10.1371/journal.pone.0243980, doi:10.1371/journal.pone.0243980. This article has 33 citations and is from a peer-reviewed journal.
(gehin2023cert1mutationsperturb pages 12-13): Charlotte Gehin, Museer A. Lone, Winston Lee, Laura Capolupo, Sylvia Ho, Adekemi M. Adeyemi, Erica H. Gerkes, Alexander P.A. Stegmann, Estrella López-Martín, Eva Bermejo-Sánchez, Beatriz Martínez-Delgado, Christiane Zweier, Cornelia Kraus, Bernt Popp, Vincent Strehlow, Daniel Gräfe, Ina Knerr, Eppie R. Jones, Stefano Zamuner, Luciano A. Abriata, Vidya Kunnathully, Brandon E. Moeller, Anthony Vocat, Samuel Rommelaere, Jean-Philippe Bocquete, Evelyne Ruchti, Greta Limoni, Marine Van Campenhoudt, Samuel Bourgeat, Petra Henklein, Christian Gilissen, Bregje W. van Bon, Rolph Pfundt, Marjolein H. Willemsen, Jolanda H. Schieving, Emanuela Leonardi, Fiorenza Soli, Alessandra Murgia, Hui Guo, Qiumeng Zhang, Kun Xia, Christina R. Fagerberg, Christoph P. Beier, Martin J. Larsen, Irene Valenzuela, Paula Fernández-Álvarez, Shiyi Xiong, Robert Śmigiel, Vanesa López-González, Lluís Armengol, Manuela Morleo, Angelo Selicorni, Annalaura Torella, Moira Blyth, Nicola S. Cooper, Valerie Wilson, Renske Oegema, Yvan Herenger, Aurore Garde, Ange-Line Bruel, Frederic Tran Mau-Them, Alexis B.R. Maddocks, Jennifer M. Bain, Musadiq A. Bhat, Gregory Costain, Peter Kannu, Ashish Marwaha, Neena L. Champaigne, Michael J. Friez, Ellen B. Richardson, Vykuntaraju K. Gowda, Varunvenkat M. Srinivasan, Yask Gupta, Tze Y. Lim, Simone Sanna-Cherchi, Bruno Lemaitre, Toshiyuki Yamaji, Kentaro Hanada, John E. Burke, Ana Marjia Jakšić, Brian D. McCabe, Paolo De Los Rios, Thorsten Hornemann, Giovanni D’Angelo, and Vincenzo A. Gennarino. Cert1 mutations perturb human development by disrupting sphingolipid homeostasis. Journal of Clinical Investigation, May 2023. URL: https://doi.org/10.1172/jci165019, doi:10.1172/jci165019. This article has 37 citations and is from a highest quality peer-reviewed journal.
(gehin2023cert1mutationsperturb pages 10-12): Charlotte Gehin, Museer A. Lone, Winston Lee, Laura Capolupo, Sylvia Ho, Adekemi M. Adeyemi, Erica H. Gerkes, Alexander P.A. Stegmann, Estrella López-Martín, Eva Bermejo-Sánchez, Beatriz Martínez-Delgado, Christiane Zweier, Cornelia Kraus, Bernt Popp, Vincent Strehlow, Daniel Gräfe, Ina Knerr, Eppie R. Jones, Stefano Zamuner, Luciano A. Abriata, Vidya Kunnathully, Brandon E. Moeller, Anthony Vocat, Samuel Rommelaere, Jean-Philippe Bocquete, Evelyne Ruchti, Greta Limoni, Marine Van Campenhoudt, Samuel Bourgeat, Petra Henklein, Christian Gilissen, Bregje W. van Bon, Rolph Pfundt, Marjolein H. Willemsen, Jolanda H. Schieving, Emanuela Leonardi, Fiorenza Soli, Alessandra Murgia, Hui Guo, Qiumeng Zhang, Kun Xia, Christina R. Fagerberg, Christoph P. Beier, Martin J. Larsen, Irene Valenzuela, Paula Fernández-Álvarez, Shiyi Xiong, Robert Śmigiel, Vanesa López-González, Lluís Armengol, Manuela Morleo, Angelo Selicorni, Annalaura Torella, Moira Blyth, Nicola S. Cooper, Valerie Wilson, Renske Oegema, Yvan Herenger, Aurore Garde, Ange-Line Bruel, Frederic Tran Mau-Them, Alexis B.R. Maddocks, Jennifer M. Bain, Musadiq A. Bhat, Gregory Costain, Peter Kannu, Ashish Marwaha, Neena L. Champaigne, Michael J. Friez, Ellen B. Richardson, Vykuntaraju K. Gowda, Varunvenkat M. Srinivasan, Yask Gupta, Tze Y. Lim, Simone Sanna-Cherchi, Bruno Lemaitre, Toshiyuki Yamaji, Kentaro Hanada, John E. Burke, Ana Marjia Jakšić, Brian D. McCabe, Paolo De Los Rios, Thorsten Hornemann, Giovanni D’Angelo, and Vincenzo A. Gennarino. Cert1 mutations perturb human development by disrupting sphingolipid homeostasis. Journal of Clinical Investigation, May 2023. URL: https://doi.org/10.1172/jci165019, doi:10.1172/jci165019. This article has 37 citations and is from a highest quality peer-reviewed journal.
(gehin2023cert1mutationsperturb media ad12d9c6): Charlotte Gehin, Museer A. Lone, Winston Lee, Laura Capolupo, Sylvia Ho, Adekemi M. Adeyemi, Erica H. Gerkes, Alexander P.A. Stegmann, Estrella López-Martín, Eva Bermejo-Sánchez, Beatriz Martínez-Delgado, Christiane Zweier, Cornelia Kraus, Bernt Popp, Vincent Strehlow, Daniel Gräfe, Ina Knerr, Eppie R. Jones, Stefano Zamuner, Luciano A. Abriata, Vidya Kunnathully, Brandon E. Moeller, Anthony Vocat, Samuel Rommelaere, Jean-Philippe Bocquete, Evelyne Ruchti, Greta Limoni, Marine Van Campenhoudt, Samuel Bourgeat, Petra Henklein, Christian Gilissen, Bregje W. van Bon, Rolph Pfundt, Marjolein H. Willemsen, Jolanda H. Schieving, Emanuela Leonardi, Fiorenza Soli, Alessandra Murgia, Hui Guo, Qiumeng Zhang, Kun Xia, Christina R. Fagerberg, Christoph P. Beier, Martin J. Larsen, Irene Valenzuela, Paula Fernández-Álvarez, Shiyi Xiong, Robert Śmigiel, Vanesa López-González, Lluís Armengol, Manuela Morleo, Angelo Selicorni, Annalaura Torella, Moira Blyth, Nicola S. Cooper, Valerie Wilson, Renske Oegema, Yvan Herenger, Aurore Garde, Ange-Line Bruel, Frederic Tran Mau-Them, Alexis B.R. Maddocks, Jennifer M. Bain, Musadiq A. Bhat, Gregory Costain, Peter Kannu, Ashish Marwaha, Neena L. Champaigne, Michael J. Friez, Ellen B. Richardson, Vykuntaraju K. Gowda, Varunvenkat M. Srinivasan, Yask Gupta, Tze Y. Lim, Simone Sanna-Cherchi, Bruno Lemaitre, Toshiyuki Yamaji, Kentaro Hanada, John E. Burke, Ana Marjia Jakšić, Brian D. McCabe, Paolo De Los Rios, Thorsten Hornemann, Giovanni D’Angelo, and Vincenzo A. Gennarino. Cert1 mutations perturb human development by disrupting sphingolipid homeostasis. Journal of Clinical Investigation, May 2023. URL: https://doi.org/10.1172/jci165019, doi:10.1172/jci165019. This article has 37 citations and is from a highest quality peer-reviewed journal.
(gehin2023cert1mutationsperturb media 91444d58): Charlotte Gehin, Museer A. Lone, Winston Lee, Laura Capolupo, Sylvia Ho, Adekemi M. Adeyemi, Erica H. Gerkes, Alexander P.A. Stegmann, Estrella López-Martín, Eva Bermejo-Sánchez, Beatriz Martínez-Delgado, Christiane Zweier, Cornelia Kraus, Bernt Popp, Vincent Strehlow, Daniel Gräfe, Ina Knerr, Eppie R. Jones, Stefano Zamuner, Luciano A. Abriata, Vidya Kunnathully, Brandon E. Moeller, Anthony Vocat, Samuel Rommelaere, Jean-Philippe Bocquete, Evelyne Ruchti, Greta Limoni, Marine Van Campenhoudt, Samuel Bourgeat, Petra Henklein, Christian Gilissen, Bregje W. van Bon, Rolph Pfundt, Marjolein H. Willemsen, Jolanda H. Schieving, Emanuela Leonardi, Fiorenza Soli, Alessandra Murgia, Hui Guo, Qiumeng Zhang, Kun Xia, Christina R. Fagerberg, Christoph P. Beier, Martin J. Larsen, Irene Valenzuela, Paula Fernández-Álvarez, Shiyi Xiong, Robert Śmigiel, Vanesa López-González, Lluís Armengol, Manuela Morleo, Angelo Selicorni, Annalaura Torella, Moira Blyth, Nicola S. Cooper, Valerie Wilson, Renske Oegema, Yvan Herenger, Aurore Garde, Ange-Line Bruel, Frederic Tran Mau-Them, Alexis B.R. Maddocks, Jennifer M. Bain, Musadiq A. Bhat, Gregory Costain, Peter Kannu, Ashish Marwaha, Neena L. Champaigne, Michael J. Friez, Ellen B. Richardson, Vykuntaraju K. Gowda, Varunvenkat M. Srinivasan, Yask Gupta, Tze Y. Lim, Simone Sanna-Cherchi, Bruno Lemaitre, Toshiyuki Yamaji, Kentaro Hanada, John E. Burke, Ana Marjia Jakšić, Brian D. McCabe, Paolo De Los Rios, Thorsten Hornemann, Giovanni D’Angelo, and Vincenzo A. Gennarino. Cert1 mutations perturb human development by disrupting sphingolipid homeostasis. Journal of Clinical Investigation, May 2023. URL: https://doi.org/10.1172/jci165019, doi:10.1172/jci165019. This article has 37 citations and is from a highest quality peer-reviewed journal.

Artifacts

Edison artifact artifact-00

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	8
Resolved	8
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	8
On topic	3
Off topic	1

References that may not be about this subject

These identifiers resolve, so they are not fabrications, but the records they resolve to share almost none of this report's vocabulary. That is a clue and not a verdict - a paper can be relevant in ways its title and abstract do not spell out - so read them before deciding:

DOI:10.1002/anie.202413562 (2 mentions) - Live‐Cell Identification of Inhibitors of the Lipid Transfer Protein CERT Using Nanoluciferase Bioluminescence Resonance Energy Transfer (NanoBRET)
shared terms: cert

Weighed against this report's own most characteristic terms: disease, variant, gene, clinical, genetic, disability, individual, developmental, human, affected, phenotype, model, cert1, intellectual, established, abnormalitie, function, pathogenic, cert, allele.

All extracted references resolved successfully. Resolving is not the same as being relevant, though - see the references listed above as possibly off topic.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	49
Resolved	49
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	0
Terms whose name was checked	3
Terms named correctly	0
Terms named as a different term	2
Terms whose name is worth a second look	1

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

HP:0001252 (1 mention) - the report calls it "Frequently infantile, contributing to motor and feeding difficulty"; HP calls it Hypotonia
HP:0001999 (1 mention) - the report calls it "Variable facial, hand, and foot abnormalities; no single pathognomonic gestalt"; HP calls it Abnormal facial shape

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

UBERON:0002437 (1 mention) - the report calls it "White matter/myelin: cerebral white matter"; UBERON calls it cerebral hemisphere white matter**, and lists "cerebral white matter" among its other names

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Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Prevalence

Differential Diagnoses

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Intellectual Disability, Autosomal Dominant 34 (MRD34): Research Report

Executive summary

1. Disease information

Definition and identifiers

2. Etiology, risks, and protective factors

Causal factor

Risk, protective, and gene–environment factors

3. Phenotypes

4. Genetic and molecular information

Gene and variant architecture

Functional consequence and modifiers

5. Environmental information

6. Mechanism and pathophysiology

Ordered causal chain

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

10. Diagnostics

Recommended approach

Differential diagnosis

11. Outcome and prognosis

12. Treatment and real-world management

13. Prevention

14. Other species and natural disease

15. Model organisms and experimental systems

Evidence appraisal and recent developments

Artifacts

Reference Validation

References that may not be about this subject

Term Validation

Terms the report names something else

Terms whose name is worth a second look