Neurodevelopmental Disorder with Severe Motor Impairment and Absent Language

Mendelian MONDO:0060622 Pathograph 17 Show in embeddings browser Neurodevelopmental Disorder

Neurodevelopmental disorder with severe motor impairment and absent language (NEDMIAL; OMIM:617804) is an ultra-rare Mendelian neurodevelopmental disorder caused by rare heterozygous variants in DHX30, which encodes an ATP-dependent DExH-box RNA helicase. The defining 2017 series described twelve unrelated individuals with global developmental delay, intellectual disability, severe speech impairment and gait abnormalities, all carrying de novo missense variants in highly conserved helicase core motifs (HCMs). A 2021 study of 25 further individuals established that the DHX30 allelic spectrum splits into two clinically distinct subtypes keyed to variant class. HCM missense variants produce the classic severe phenotype: they impair ATPase and RNA-unwinding activity and, in addition, confer a detrimental gain of function with respect to stress-granule assembly, which interferes with global translation. Haploinsufficiency and protein-truncating alleles - and a mosaic HCM missense carrier - give a milder course in which affected individuals walk in the second year and acquire some speech. The mechanistic reading is therefore not a simple dosage lesion: the severe phenotype requires the acquired stress-granule property on top of the catalytic loss, which is why halving DHX30 dosage is better tolerated than a catalytically dead protein that still assembles into granules. DHX30 additionally exists as cytoplasmic and more abundant mitochondrially targeted isoforms and contributes to mitoribosomal translation and mitochondrial energy metabolism, but that arm has been characterised only in cancer-cell models and its contribution to the human neurodevelopmental phenotype remains inferred. There is no disease-modifying therapy; care is symptomatic, with augmentative communication reported to reduce frustration-related behaviour.

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1
Definitions
2
Inheritance
8
Pathophys.
14
Phenotypes
3
Gaps
17
Pathograph
1
Genes
3
Medical Actions
2
Subtypes
2
Models
🏷

Classifications

Harrison's Part
NEUROLOGIC
📘

Definitions

1
👪

Inheritance

2
Autosomal dominant, de novo HP:0000006
Nearly all reported probands carry a heterozygous de novo DHX30 variant. Both the 2017 discovery series and the 2021 cohort are dominated by de novo missense alleles, and none of the reported alterations is present in gnomAD v2.1.1.
autosomal dominant inheritance
Show evidence (2 references)
PMID:29100085 SUPPORT Human Clinical
"Here we identified six different de novo missense mutations in DHX30 in twelve unrelated individuals affected by global developmental delay (GDD), intellectual disability (ID), severe speech impairment and gait abnormalities."
Establishes heterozygous de novo missense variants as the mode of inheritance in the defining cohort.
PMID:34145223 SUPPORT Human Clinical
"NEDMIAL is characterized by severely delayed psychomotor development, which causes an autosomal dominant disorder."
Independent statement that the entity is transmitted as an autosomal dominant disorder.
Parental gonadal mosaicism HP:0001442
Recurrence in siblings born to clinically unaffected, test-negative parents has been documented more than once, and is attributed to parental gonadal (germline) mosaicism. This is the main counselling caveat in an otherwise de novo disorder: negative parental testing on blood does not reduce recurrence risk to background. A heterozygous nonsense allele inherited from a mosaic mother has also been reported.
gonadal mosaicism in a clinically unaffected parent
Show evidence (2 references)
PMID:37094863 SUPPORT Human Clinical
"The same variant was confirmed in two siblings but not in their parents, suggesting the possibility of de novo germline mosaicism."
Documents sibling recurrence with negative parental testing, the observation that identifies parental germline mosaicism.
PMID:34020708 SUPPORT Human Clinical
"p.(Arg782Trp) (5 individuals including two half-sisters indicative of gonadal mosaicism)"
Independent instance of gonadal mosaicism inferred from two affected half-sisters carrying the same recurrent HCM allele.
◆

Subtypes

2
Helicase-core-motif missense subtype (severe)
The classic, severe NEDMIAL phenotype, caused by a heterozygous missense variant within one of the highly conserved helicase core motifs. All 19 individuals of this class in the 2021 cohort had global developmental delay, intellectual disability, severe speech impairment and gait abnormalities; fewer than half achieved independent walking and most were non-verbal. The mechanism combines loss of ATPase/helicase activity with a detrimental gain of function in stress-granule assembly.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"All 19 individuals harboring heterozygous missense variants within helicase core motifs (HCMs) have global developmental delay, intellectual disability, severe speech impairment, and gait abnormalities."
Defines the severe subtype by variant class and states its obligate clinical features in the 19-person group.
Haploinsufficiency / protein-truncating subtype (mild)
A milder clinical course seen in individuals carrying alleles that reduce DHX30 dosage or truncate the protein - frameshift, nonsense, whole-gene deletion, or in-frame multi-exon deletion. These individuals walked in the second year of life, had only mild muscular hypotonia, and spoke at least 20 words by age three. A de novo mosaic HCM missense carrier fell into the same milder band, consistent with the severe phenotype requiring a sufficient burden of the mutant protein rather than merely reduced wild-type dosage.
Show evidence (2 references)
PMID:34020708 SUPPORT Human Clinical
"Notably, 4 individuals harboring heterozygous variants resulting either in haploinsufficiency or truncated proteins presented with a milder clinical course, similar to an individual harboring a de novo mosaic HCM missense variant."
Establishes the milder subtype, its variant classes, and the mosaic missense carrier who behaves like it.
PMID:34020708 SUPPORT Human Clinical
"who all learned to walk in the second year of life, had a mild muscular hypotonia and spoke at least 20 words by the age of 3 years"
Gives the specific developmental milestones that distinguish the mild subtype from the severe one.
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Discussions and Knowledge Gaps

3
Does the mitoribosomal-translation and mitochondrial-energy-metabolism function of DHX30, characterised entirely by depleting both isoforms in cancer cell lines, contribute to the human neurodevelopmental phenotype caused by helicase-core-motif missense alleles?
HUMAN MODEL MISMATCH OPEN dhx30_mitochondrial_arm_translational_validity
Attached to
pathophysiology#Impaired Mitochondrial Translation and Energy Metabolism
The mismatch is directional as well as contextual. Every measurement supporting the mitochondrial arm comes from depleting DHX30 in HCT116, U2OS or MCF7 cells - the loss-of-function configuration, which in humans produces the mild subtype. The severe human phenotype is caused by a catalytically dead protein that is still expressed and still assembles into granules. The same study shows the two configurations diverge on the cytoplasmic readout, since depletion raises global translation while the missense variants lower it, so there is a positive reason not to assume the mitochondrial readout transfers either. No mitochondrial measurement has been made in a neuron, an NEDMIAL patient cell, or an HCM-variant-expressing system.
Proposed experiments
Mitochondrial translation and respiration in HCM-variant neural cells
dhx30_mito_readout_in_hcm_variant_neurons
Introduce a recurrent HCM missense allele (for example p.Arg782Trp) into human iPSC-derived neurons or neural progenitors at the endogenous locus, and measure mitoribosomal-transcript translational efficiency, mitochondrial protein synthesis and oxygen consumption rate against isogenic wild-type and DHX30-heterozygous-null controls. Including the heterozygous null arm is what separates a dosage effect from a mutant-protein effect.
Would support
pathophysiology#Impaired Mitochondrial Translation and Energy Metabolism
Would refute
pathophysiology#Impaired Mitochondrial Translation and Energy Metabolism
Supporting outcome
  • HCM-variant neurons show reduced mitoribosome translational efficiency and reduced oxygen consumption relative to isogenic wild-type controls.
Refuting outcome
  • Mitoribosomal translational efficiency and respiration are unchanged in HCM-variant neurons, or are altered only in the heterozygous-null arm, indicating the mitochondrial arm belongs to dosage loss and not to the severe disease mechanism.
What happens to stress-granule dynamics and translational output in human neurons carrying an endogenous DHX30 helicase-core-motif missense variant?
KNOWLEDGE GAP OPEN dhx30_no_patient_derived_neural_model
Attached to
pathophysiology#Global Translation Inhibition pathophysiology#Disrupted Brain Development
The stress-granule and translation phenotypes were established by overexpressing GFP-tagged variant DHX30 in HEK293T and U2OS cells - a kidney line and an osteosarcoma line, at non-physiological levels. The step from the cellular translational lesion to impaired neuronal differentiation and circuit formation is the weakest link in the causal chain and is currently pure inference. No iPSC-derived neuron, organoid, or post-mortem study of an affected individual has been reported.
What is the population prevalence of DHX30-related neurodevelopmental disorder, and what is the natural history into adulthood?
KNOWLEDGE GAP OPEN dhx30_no_natural_history_or_prevalence
Attached to
prevalence#Worldwide phenotypes#Absent speech
All reported individuals come from case series ascertained through diagnostic sequencing, GeneMatcher, and a Facebook family support group, so published feature frequencies are vulnerable to ascertainment bias and there is no denominator. Adult outcome data are limited to isolated reports. This matters practically: the 47% ambulation and 74% non-verbal figures are the numbers families are counselled with, and they derive from 19 people.
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Pathophysiology

8
Heterozygous DHX30 Helicase Core Motif Missense Variant
Mechanism confidence: Established
The severe form of the disorder is initiated by a heterozygous missense substitution in one of the eight highly conserved helicase core motifs of DHX30. These motifs sit within the two RecA-like domains that jointly form the ATP- and RNA-binding surface of an SF2 helicase, so a substitution there is positioned to disrupt ATP binding and hydrolysis, RNA recognition, or the coupling between them. Recurrent alleles include p.(Arg493His), p.(His562Arg), p.(Arg782Trp), p.(Arg785Cys) and p.(Arg785His). None of the reported alterations occurs in gnomAD v2.1.1, and DHX30 is among the most missense-intolerant genes in the human genome.
DHX30 hgnc:16716 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves DHX30 (hgnc:16716). hgnc:16716 is a gene from the HUGO Gene Nomenclature Committee.
Downstream
Loss of DHX30 ATPase and RNA Helicase Activity Substitutions in the ATP- and RNA-binding motifs directly compromise the catalytic cycle of the helicase.
Excess Stress Granule Assembly The mutant proteins acquire an increased propensity to nucleate stress granules, a property that is not explained by loss of catalytic activity alone.
Show evidence (3 references)
PMID:29100085 SUPPORT Human Clinical
"All amino acid changes are located within highly conserved helicase motifs and were found to either impair ATPase activity or RNA recognition in different in vitro assays."
Establishes that the causal substitutions fall inside the conserved helicase motifs and that this is where the functional lesion arises.
PMID:34020708 SUPPORT Human Clinical
"Notably, none of these DHX30 alterations was present in the gnomAD dataset v2.1.1"
Population-database absence of every reported allele supports their causality rather than incidental rarity.
PMID:34020708 SUPPORT Computational
"Within these two core helicase domains, eight highly conserved sequence elements, helicase core motifs (HCMs) play a role in either RNA binding, or ATP binding and hydrolysis."
States the structural role of the motifs the disease variants occupy; this is a sequence/structure classification rather than a measurement.
DHX30 Haploinsufficiency
Mechanism confidence: Established
A separate allelic class - frameshift, nonsense, whole-gene deletion, or in-frame multi-exon deletion - reduces the amount of functional DHX30 produced rather than installing a catalytically dead protein. DHX30 is extremely loss-of-function intolerant in population data (pLI 1, LOEUF 0.04), so this is a real lesion; but clinically it produces the milder subtype, which is the observation that separates dosage loss from the severe HCM missense mechanism.
DHX30 hgnc:16716 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves DHX30 (hgnc:16716). hgnc:16716 is a gene from the HUGO Gene Nomenclature Committee.
Downstream
Global Neurodevelopmental Impairment Reduced DHX30 dosage produces the milder end of the clinical spectrum. The intervening cell-biological steps have not been characterised for this allelic class, which notably does not carry the stress-granule gain of function.
Show evidence (2 references)
PMID:34020708 SUPPORT Human Clinical
"Furthermore, we identified four individuals bearing likely pathogenic loss-of-function variants."
Establishes the existence of a distinct loss-of-function allelic class in the DHX30 disorder.
PMID:34020708 SUPPORT Computational
"according to the gnomAD v2.1.1 dataset DHX30 is, with a probability of being loss-of-function intolerant (pLI) score of 1 and a loss-of-function observed/expected upper bound fraction (LOEUF) score of 0.04, extremely loss-of-function intolerant"
Constraint metrics computed over a population database establish that reduced DHX30 dosage is not tolerated, supporting haploinsufficiency as a genuine disease mechanism.
Loss of DHX30 ATPase and RNA Helicase Activity
Mechanism confidence: Established
DHX30 is an ATP-dependent DExH-box RNA helicase that uses ATP hydrolysis to unwind RNA secondary structure. HCM missense variants were shown, in immunoprecipitated-protein ATPase assays and in a radiolabelled RNA-duplex unwinding assay with recombinant protein, to impair both the ATPase and the helicase activity of the protein. The 2021 study formally established DHX30 as an ATP-dependent RNA helicase, so the activity being lost is a directly measured one rather than an annotation inherited from family membership.
DHX30 hgnc:16716 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves DHX30 (hgnc:16716). hgnc:16716 is a gene from the HUGO Gene Nomenclature Committee.
RNA helicase activity GO:0003724 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased RNA helicase activity (GO:0003724). GO:0003724 is a molecular function from the Gene Ontology. ↓ DECREASED ATP hydrolysis activity GO:0016887 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased ATP hydrolysis activity (GO:0016887). GO:0016887 is a molecular function from the Gene Ontology. ↓ DECREASED
Downstream
Global Translation Inhibition Loss of the ATP-driven unwinding step contributes to the translational defect, but the measured route from mutant protein to reduced translation runs through stress-granule sequestration.
Show evidence (3 references)
PMID:34020708 SUPPORT In Vitro
"Protein variants of DHX30 affect ATPase and helicase activity."
Direct biochemical demonstration that the disease variants reduce both ATPase and helicase activity, from the immunoprecipitated-protein ATPase assay and the recombinant-protein RNA unwinding assay.
PMID:34020708 SUPPORT In Vitro
"For this, we have now formally confirmed that DHX30 possesses ATP-dependent RNA helicase activity."
Establishes the wild-type activity whose loss this node describes, using purified recombinant protein rather than family-membership annotation.
PMID:29100085 SUPPORT In Vitro
"DHX30 is a member of the family of DExH-box helicases, which use ATP hydrolysis to unwind RNA secondary structures."
States the coupling between ATP hydrolysis and duplex unwinding that the disease variants break.
Excess Stress Granule Assembly
Mechanism confidence: Established
This is the node that distinguishes the severe subtype from simple dosage loss. Overexpressed HCM missense DHX30 protein nucleates cytoplasmic stress granules far more readily than wild-type protein, an acquired property that the authors classify as a detrimental gain of function layered on top of the catalytic loss. Wild-type DHX30 is itself an evolutionarily conserved factor in stress-granule assembly, and CRISPR DHX30-deficient HEK293T cells and zebrafish show impaired granule assembly - so the mutant proteins push a normal DHX30 function past its regulatory setpoint rather than doing something DHX30 never does.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
cytoplasmic stress granule assembly GO:0034063 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves cytoplasmic stress granule assembly (GO:0034063), qualified as gain of function. GO:0034063 is a biological process from the Gene Ontology. ⇑ GAIN OF FUNCTION
Animal models
dhx30 CRISPR knockout zebrafish Zebrafish perturbs Losing dhx30 impairs stress-granule assembly, establishing that dhx30 is a conserved positive factor in granule formation. This is the mirror image of the human disease allele, which drives excess granules.
Downstream
Global Translation Inhibition Sequestration of mRNA-protein complexes into stress granules withdraws transcripts from active translation.
Show evidence (2 references)
PMID:29100085 SUPPORT In Vitro
"Moreover, protein variants exhibit an increased propensity to trigger stress granule (SG) formation resulting in global translation inhibition."
Direct cellular demonstration that the disease variants drive excess stress-granule formation and that this is what inhibits translation.
PMID:34020708 SUPPORT In Vitro
"Thus, HCM missense variants might actually result in a detrimental gain-of-function by inducing SG formation with concomitant global translation impairment even without endogenous or exogenous stressors."
The authors' cellular interpretation: the stress-granule gain of function is constitutive, occurring without an applied stressor, which is what makes it a disease mechanism rather than an exaggerated stress response.
Global Translation Inhibition
Mechanism confidence: Established
Cells expressing HCM missense DHX30 show reduced global protein synthesis, measured by puromycin incorporation. This is the cellular endpoint the discovery paper named in its title and is the best-established consequence of the severe-subtype alleles. Note the direction is variant-class specific: depleting DHX30 in cancer cells raises rather than lowers global translation, so translational inhibition here is a property of the mutant protein, not of reduced DHX30 dosage.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
translation GO:0006412 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased translation (GO:0006412). GO:0006412 is a biological process from the Gene Ontology. ↓ DECREASED regulation of translation GO:0006417 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal regulation of translation (GO:0006417). GO:0006417 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Disrupted Brain Development The specific transcripts whose translational failure produces human cortical and cerebellar findings have not been identified, and the step has not been demonstrated in patient-derived neurons, so at least one required intermediate is unknown.
Show evidence (3 references)
PMID:29100085 SUPPORT In Vitro
"Moreover, protein variants exhibit an increased propensity to trigger stress granule (SG) formation resulting in global translation inhibition."
Names global translation inhibition as the measured downstream consequence of the variant-driven stress-granule phenotype.
PMID:34020708 SUPPORT In Vitro
"We have previously shown that the expression of mutant forms of DHX30 induces the formation of stress granules, concomitant with a global down-regulation of translation"
Ties the translational down-regulation directly to the stress-granule phenotype in the same cellular system, which is the upstream node here.
PMID:34503222 SUPPORT INDIRECT In Vitro
"Furthermore, the depletion of both DHX30 isoforms leads to higher global translation but slower proliferation and lower mitochondrial energy metabolism."
Cited to constrain, not to extend, the claim: losing DHX30 raises global translation, which is the opposite direction from the mutant protein. The inference step is that translational inhibition must therefore be a property of the HCM missense allele rather than of reduced DHX30 dosage.
Impaired Mitochondrial Translation and Energy Metabolism
Mechanism confidence: Hypothetical
DHX30 is transcribed from two alternative promoters into a cytoplasmic form and a more abundant mitochondrially targeted form, and it associates with nuclear-encoded mitoribosome transcripts. Depleting both isoforms in colorectal carcinoma cells reduces the translational efficiency of mitoribosome mRNAs and lowers mitochondrial energy metabolism. This node is recorded as a plausible parallel arm rather than an established disease mechanism: every measurement supporting it was made in non-neural cancer cell lines under isoform depletion, which is the loss-of-function configuration, whereas the severe human phenotype is driven by a catalytically dead protein. No mitochondrial readout has been reported in NEDMIAL patient material.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
mitochondrial translation GO:0032543 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased mitochondrial translation (GO:0032543). GO:0032543 is a biological process from the Gene Ontology. ↓ DECREASED
mitochondrion GO:0005739 Gene Ontology (GO) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in mitochondrion (GO:0005739). GO:0005739 is an anatomical location from the Gene Ontology.
Downstream
Disrupted Brain Development A hypothetical contribution. The developing brain is energy-demanding, so a mitoribosomal translation deficit would plausibly affect it, but no step of this route has been demonstrated in a neural system or in patients.
Show evidence (2 references)
PMID:34503222 SUPPORT INDIRECT In Vitro
"The depletion of both DHX30 isoforms in HCT116 cells leads to constitutive changes in polysome-associated mRNAs, enhancing the translation of mRNAs coding for cytoplasmic ribosomal proteins while reducing the translational efficiency of the nuclear-encoded mitoribosome mRNAs."
Establishes the mitoribosomal translation arm of DHX30 biology. Indirect for this disease because it is measured in a colorectal carcinoma line under isoform depletion, not in neurons carrying a disease allele.
PMID:34503222 SUPPORT INDIRECT In Vitro
"Here, we show that DHX30 exhibits a more general function by integrating the activities of its cytoplasmic isoform and of the more abundant mitochondrial one."
Documents the dual-isoform architecture that makes a mitochondrial contribution to the disorder biologically plausible.
Disrupted Brain Development
Mechanism confidence: Provisional
Structural brain anomalies are found on MRI in roughly two-thirds of severe-subtype individuals, and DHX30 is required for central-nervous-system development in mouse, where homozygous deletion is embryonic lethal with early CNS developmental defects. Expressing pathogenic DHX30 variants in zebrafish embryos causes developmental defects. The node is provisional because no consistent human malformation signature exists - MRI may be normal - and because the link from the cellular translational lesion to the tissue phenotype has not been traced in human neural tissue.
neural stem cell CL:0000047 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neural stem cell (CL:0000047). CL:0000047 is a cell type from the Cell Ontology. neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
brain development GO:0007420 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal brain development (GO:0007420). GO:0007420 is a biological process from the Gene Ontology. ⚠ ABNORMAL neuron differentiation GO:0030182 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal neuron differentiation (GO:0030182). GO:0030182 is a biological process from the Gene Ontology. ⚠ ABNORMAL
brain UBERON:0000955 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in brain (UBERON:0000955). UBERON:0000955 is an anatomical location from the Uberon multi-species anatomy ontology.
Animal models
DHX30 variant-expressing zebrafish embryos Zebrafish recapitulates Expressing the human disease alleles causes developmental defects in the embryo, directly connecting the molecular lesion to disturbed development in a vertebrate.
Downstream
Global Neurodevelopmental Impairment Abnormal brain structure and development is the tissue-level substrate of the intellectual disability, motor impairment and absent language observed clinically.
Show evidence (3 references)
PMID:34020708 SUPPORT Human Clinical
"structural brain anomalies in eleven (65%, 11/17)"
Quantifies structural brain involvement in the severe-subtype cohort, establishing the tissue-level abnormality this node describes.
PMID:34145223 SUPPORT Model Organism
"The homozygous deletion of DHX30 leads to early embryonic lethality and causes early developmental defects in the central nervous system in mice"
Establishes a requirement for DHX30 in mammalian CNS development. Graded MODEL_ORGANISM because the observation is a mouse whole-organism result.
PMID:34020708 SUPPORT Model Organism
"These variants impair the ATPase and helicase activity of DHX30, trigger SG formation, interfere with global translation, and cause developmental defects in a zebrafish model."
The human disease alleles themselves produce developmental defects in a vertebrate embryo, linking the molecular lesion to disturbed development.
Global Neurodevelopmental Impairment
Mechanism confidence: Established
The organism-level convergence point: global developmental delay, intellectual disability, severe or absent expressive speech, muscular hypotonia, and severely impaired or absent independent gait. This is the node from which the clinical phenotype layer of this entry is reached, and it is where the two variant-class subtypes differ in degree rather than in kind.
Animal models
dhx30 CRISPR knockout zebrafish Zebrafish partially recapitulates dhx30-deficient larvae show altered sleep-wake activity and reduced social preference, matching the sleep disturbance and autistic features seen in patients.
Show evidence (2 references)
PMID:34020708 SUPPORT Human Clinical
"All 19 individuals harboring heterozygous missense variants within helicase core motifs (HCMs) have global developmental delay, intellectual disability, severe speech impairment, and gait abnormalities."
Enumerates the organism-level clinical features that define the disorder in its severe form.
PMID:34145223 SUPPORT Human Clinical
"The affected patients show muscular hypotonia, feeding difficulties, ataxic gait, or an inability to walk."
Independent restatement of the organism-level motor phenotype.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Neurodevelopmental Disorder with Severe Motor Impairment and Absent Language Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

14
Digestive 1
Feeding difficulties VERY_FREQUENT HP:0011968 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Feeding difficulties (HP:0011968). HP:0011968 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"Additional phenotypic features included muscular hypotonia in eighteen (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen (81%, 13/16), joint hypermobility in fourteen (74%), structural brain anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%), strabismus in..."
Feeding difficulties in 84% of the severe-subtype group, the VERY_FREQUENT band.
Eye 1
Strabismus FREQUENT HP:0000486 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Strabismus (HP:0000486). HP:0000486 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"Additional phenotypic features included muscular hypotonia in eighteen (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen (81%, 13/16), joint hypermobility in fourteen (74%), structural brain anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%), strabismus in..."
Strabismus in 42% of the severe-subtype group, the FREQUENT band.
Head and Neck 1
Microcephaly VERY_FREQUENT HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"Additional phenotypic features included muscular hypotonia in eighteen (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen (81%, 13/16), joint hypermobility in fourteen (74%), structural brain anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%), strabismus in..."
Microcephaly in 81% (13/16 assessed) of the severe-subtype group, the VERY_FREQUENT band.
Musculoskeletal 2
Hypotonia VERY_FREQUENT HP:0001252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Muscular hypotonia, annotated with Hypotonia (HP:0001252). HP:0001252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"Additional phenotypic features included muscular hypotonia in eighteen (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen (81%, 13/16), joint hypermobility in fourteen (74%), structural brain anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%), strabismus in..."
Hypotonia in 95% of the severe-subtype group places it in the VERY_FREQUENT (80-99%) band.
Joint hypermobility FREQUENT HP:0001382 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Joint hypermobility (HP:0001382). HP:0001382 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"Additional phenotypic features included muscular hypotonia in eighteen (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen (81%, 13/16), joint hypermobility in fourteen (74%), structural brain anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%), strabismus in..."
Joint hypermobility in 74% of the severe-subtype group, the FREQUENT (30-79%) band.
Nervous System 9
Global developmental delay OBLIGATE HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Sequelae: Intellectual disability
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"All 19 individuals harboring heterozygous missense variants within helicase core motifs (HCMs) have global developmental delay, intellectual disability, severe speech impairment, and gait abnormalities."
19/19 of the helicase-core-motif missense group, which is why the frequency band is OBLIGATE and why the phenotype is scoped to that subtype rather than to the whole entry.
Intellectual disability OBLIGATE HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249). HP:0001249 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"In more detail, all individuals had an intellectual disability, only nine (47%) learned to walk, all with an ataxic gait."
Explicit statement that intellectual disability was present in all individuals of the severe-subtype group.
Absent speech FREQUENT HP:0001344 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Absent speech (HP:0001344). HP:0001344 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"The majority had no speech (74%), four individuals spoke only single words, and only individual 6, who is mosaic for the de novo p.(Ala734Asp) variant, spoke simple sentences."
74% non-verbal in the severe-subtype group places the frequency in the FREQUENT (30-79%) band.
Motor delay OBLIGATE HP:0001270 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Motor delay (HP:0001270). HP:0001270 is a phenotype from the Human Phenotype Ontology.
Sequelae: Gait ataxia
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"In more detail, all individuals had an intellectual disability, only nine (47%) learned to walk, all with an ataxic gait."
Only 47% of the severe-subtype group learned to walk at all, establishing obligate motor delay in that group.
Gait ataxia FREQUENT HP:0002066 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ataxic gait, annotated with Gait ataxia (HP:0002066). HP:0002066 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"In more detail, all individuals had an intellectual disability, only nine (47%) learned to walk, all with an ataxic gait."
Ataxic gait in 9/19 (47%) of the severe-subtype group - all of those who walk - which is the FREQUENT band. The remainder are non-ambulant rather than normally ambulant.
Abnormal brain morphology FREQUENT HP:0012443 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Structural brain anomaly on MRI, annotated with Abnormal brain morphology (HP:0012443). HP:0012443 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"structural brain anomalies in eleven (65%, 11/17)"
Structural brain anomalies in 65% (11/17 imaged) of the severe-subtype group, the FREQUENT band.
Sleep disturbance FREQUENT HP:0002360 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sleep disturbance (HP:0002360). HP:0002360 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"Additional phenotypic features included muscular hypotonia in eighteen (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen (81%, 13/16), joint hypermobility in fourteen (74%), structural brain anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%), strabismus in..."
Sleep disturbance in 47% of the severe-subtype group, the FREQUENT band.
Autistic behavior FREQUENT HP:0000729 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Autistic behavior (HP:0000729). HP:0000729 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:34020708 SUPPORT Human Clinical
"Additional phenotypic features included muscular hypotonia in eighteen (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen (81%, 13/16), joint hypermobility in fourteen (74%), structural brain anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%), strabismus in..."
Autistic features in 33% (5/15 assessed) of the severe-subtype group, at the lower edge of the FREQUENT band.
PMID:34145223 SUPPORT Human Clinical
"It is also characterized by behavioral abnormalities, such as autistic features, low frustration tolerance, hand-flapping, and stereotypies."
Independent characterisation of the behavioural phenotype, including the specific stereotypies.
Seizure OCCASIONAL HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"Additional phenotypic features included muscular hypotonia in eighteen (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen (81%, 13/16), joint hypermobility in fourteen (74%), structural brain anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%), strabismus in..."
Seizures in 21% of the severe-subtype group, the OCCASIONAL (5-29%) band.
🧬

Genetic Associations

1
DHX30 (DHX30 (DExH-box helicase 30) at 3p21.31 is the single causal gene. Two allelic classes with different functional consequences produce two clinically distinct subtypes. Heterozygous missense variants inside the conserved helicase core motifs cause the severe classic phenotype; recurrent alleles include p.(Arg493His), p.(His562Arg), p.(Arg782Trp), p.(Arg785Cys) and p.(Arg785His). These impair ATPase and RNA-unwinding activity and additionally confer a detrimental gain of function in stress-granule assembly. The severe phenotype therefore requires the mutant protein to be present rather than merely the wild-type dosage to be halved - a mosaic carrier and four haploinsufficient individuals were all mild. No functional_impact_category is recorded here because that slot belongs to a per-variant GeneticContext and this entry does not curate variant-level allele/zygosity detail; the two allelic classes are instead modelled as separate pathophysiology nodes and has_subtypes entries. Causality rests on de novo recurrence across unrelated families, absence from gnomAD v2.1.1, extreme constraint (pLI 1, LOEUF 0.04), biochemical assays of ATPase and helicase activity, stress-granule and puromycin-incorporation assays in cultured cells, and developmental defects in zebrafish embryos expressing the human variants.)
Gene: DHX30 hgnc:16716 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is DHX30 (hgnc:16716). hgnc:16716 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: DE_NOVO
Show evidence (3 references)
PMID:29100085 SUPPORT Human Clinical
"Here we identified six different de novo missense mutations in DHX30 in twelve unrelated individuals affected by global developmental delay (GDD), intellectual disability (ID), severe speech impairment and gait abnormalities."
Establishes the gene-disease relationship through de novo recurrence in twelve unrelated probands.
PMID:34020708 SUPPORT Human Clinical
"DHX30 loss-of-function variants cause a milder phenotype whereas a severe phenotype is caused by HCM missense variants that, in addition to the loss of ATPase and helicase activity, lead to a detrimental gain-of-function with respect to SG formation."
States the allele-class-to-mechanism-to-severity mapping that this genetic record encodes.
PMID:34020708 SUPPORT Computational
"As previously noted, DHX30 is one of the most missense-intolerant genes in the human genome"
Population-constraint evidence that missense variation in DHX30 is strongly selected against, consistent with missense alleles being the severe disease class.
💊

Medical Actions

3
Augmentative and Alternative Communication
Action: augmentative and alternative communication trainingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is augmentative and alternative communication training, annotated with Speech Language Therapy (NCIT:C159273). NCIT:C159273 is a clinical intervention from the NCI Thesaurus. Ontology label: Speech Language Therapy NCIT:C159273
Platform: Behavioral / lifestyle
Tablet, smartphone, and eye-gaze-driven communication systems. Reported by the largest cohort study to substantially reduce frustration-related behaviour in non-verbal individuals - the only intervention in this disorder for which a specific benefit has been described in the primary literature, though the observation is investigator communication with families rather than a controlled study.
Mechanism Target:
MODULATES Global Neurodevelopmental Impairment — Does not alter the underlying lesion; provides an expressive channel that bypasses the absent-speech component of the organism-level phenotype.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"It is worth noting that the individuals highly benefit from communication devices (tablets, smartphones, and eye-driven tablet communication systems) which significantly reduced frustration-related behavior"
Directly reports benefit from augmentative communication devices in this patient group.
Physical Therapy and Motor Rehabilitation
Action: physical therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is physical therapy (NCIT:C15302). NCIT:C15302 is a clinical intervention from the NCI Thesaurus. Ontology label: Physical Therapy NCIT:C15302
Platform: Behavioral / lifestyle
Physiotherapy, positioning and mobility aids for the hypotonia, ataxia and joint hypermobility. Extrapolated from general management of severe neurodevelopmental motor disability; no DHX30-specific outcome data exist.
Mechanism Target:
MODULATES Global Neurodevelopmental Impairment — Symptomatic support of the motor phenotype; does not act on the translational lesion.
Show evidence (1 reference)
PMID:34020708 SUPPORT Human Clinical
"In more detail, all individuals had an intellectual disability, only nine (47%) learned to walk, all with an ataxic gait."
Establishes the severe ambulation deficit and ataxia that motor rehabilitation targets. It does not evaluate physiotherapy, which has no disease-specific trial evidence.
Genetic Counseling
Action: genetic counselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is genetic counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. Ontology label: Genetic Counseling NCIT:C15240
Platform: Behavioral / lifestyle
Counselling centres on recurrence risk. The disorder is usually de novo, but documented parental gonadal mosaicism means that negative parental testing on blood does not reduce recurrence risk to the population background, and sibling recurrence has been reported more than once. Counselling should also convey that variant class predicts severity band.
Show evidence (1 reference)
PMID:37094863 SUPPORT Human Clinical
"The same variant was confirmed in two siblings but not in their parents, suggesting the possibility of de novo germline mosaicism."
The sibling recurrence with negative parental testing is precisely the counselling scenario this entry flags.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
Twelve unrelated individuals in the 2017 defining series, 25 further individuals in the 2021 cohort, plus scattered later case reports. No population-based prevalence or incidence estimate exists; the count reflects reported cases, not an estimated rate. Ascertainment was partly through a Facebook family support group and GeneMatcher, so the reported case series are not population samples.
Show evidence (2 references)
PMID:29100085 SUPPORT Human Clinical
"Here we identified six different de novo missense mutations in DHX30 in twelve unrelated individuals affected by global developmental delay (GDD), intellectual disability (ID), severe speech impairment and gait abnormalities."
Establishes the size of the defining cohort.
PMID:34020708 SUPPORT Human Clinical
"We identified 25 previously unreported individuals, ten of whom carry novel variants, two of which are recurrent, and provide evidence of gonadal mosaicism in one family."
Gives the size of the largest subsequent cohort, supporting an ultra-rare cases-in-literature record.
🐁

Animal Models

2
dhx30 CRISPR knockout zebrafish
A stable CRISPR/Cas9 dhx30 knockout zebrafish line generated to test the consequences of losing dhx30 rather than of expressing a mutant protein. Unlike the mouse null, it is viable and grossly normal, which is what makes it usable for behavioural work.
Species
Zebrafish
Genotype
dhx30 8-bp frameshift deletion (premature stop at amino acid 107), homozygous and heterozygous
Publication
PMID:34020708
Pathograph links
Excess Stress Granule Assembly perturbs fidelity: moderate Losing dhx30 impairs stress-granule assembly, establishing that dhx30 is a conserved positive factor in granule formation. This is the mirror image of the human disease allele, which drives excess granules.
Limitations: This is a loss-of-function model and therefore perturbs the node in the opposite direction from the human severe-subtype variant; it establishes that dhx30 acts on granule assembly, not that patients have too few granules.
Show evidence (1 reference)
PMID:34020708 SUPPORT Model Organism
"Thus, these data show that SG formation is compromised in the homozygous mutants and suggests an evolutionarily conserved role for DHX30 in SG assembly."
The zebrafish-specific result behind the conservation claim: homozygous dhx30 mutants form fewer stress granules, establishing that this model perturbs the node.
Global Neurodevelopmental Impairment partially recapitulates fidelity: low dhx30-deficient larvae show altered sleep-wake activity and reduced social preference, matching the sleep disturbance and autistic features seen in patients.
Limitations: Only the two behavioural domains are reproduced. The model is a null rather than an HCM missense allele, is viable and morphologically normal, and does not reproduce the defining severe motor impairment, absent language, or intellectual disability - which have no zebrafish counterpart in any case.
Readouts
Larval sleep-wake activity over a 24-hour light-dark cycle
Direction: ALTERED
Interpretation: Behavioural correlate of the sleep disturbance reported in about half of severe-subtype patients.
Show evidence (1 reference)
PMID:34020708 SUPPORT Model Organism
"Behavioral characterization of dhx30-deficient zebrafish revealed altered sleep-wake activity and social interaction, partially resembling the human phenotype."
Reports the sleep-wake measurement behind this readout.
Social preference index
Direction: DECREASED
Interpretation: Behavioural correlate of the autistic features and impaired social communication reported in patients.
Show evidence (1 reference)
PMID:34020708 SUPPORT Model Organism
"Behavioral characterization of dhx30-deficient zebrafish revealed altered sleep-wake activity and social interaction, partially resembling the human phenotype."
Reports the social-interaction measurement behind this readout.
Show evidence (1 reference)
PMID:34020708 SUPPORT Model Organism
"Behavioral characterization of dhx30-deficient zebrafish revealed altered sleep-wake activity and social interaction, partially resembling the human phenotype."
The authors' own assessment that the model partially resembles the human phenotype supports treating it as informative for this node.
DHX30 variant-expressing zebrafish embryos
Human DHX30 cDNA carrying each candidate missense variant was expressed in one-cell-stage embryos under a neural promoter and embryos were scored for abnormal development. This is the in vivo arm of the variant-classification workflow, and it tests the mutant protein rather than gene loss.
Species
Zebrafish
Genotype
tuba1a-driven expression of wild-type or HCM-missense human DHX30 cDNA
Publication
PMID:34020708
Pathograph links
Disrupted Brain Development recapitulates fidelity: moderate Expressing the human disease alleles causes developmental defects in the embryo, directly connecting the molecular lesion to disturbed development in a vertebrate.
Limitations: Scored as gross embryonic developmental defects over 1-7 days post fertilisation under overexpression from a heterologous promoter, so neither the dosage nor the specific human cortical and cerebellar findings are modelled.
Show evidence (1 reference)
PMID:34020708 SUPPORT Model Organism
"These variants impair the ATPase and helicase activity of DHX30, trigger SG formation, interfere with global translation, and cause developmental defects in a zebrafish model."
The human disease alleles produce developmental defects in vivo, supporting this model as informative for the development node.
{ }

Source YAML

click to show 
name: Neurodevelopmental Disorder with Severe Motor Impairment and Absent Language
creation_date: '2026-09-02T00:00:00Z'
category: Mendelian
synonyms:
- NEDMIAL
- DHX30-related neurodevelopmental disorder
- DHX30-associated neurodevelopmental disorder
- neurodevelopmental disorder with variable motor and language impairment
description: >-
  Neurodevelopmental disorder with severe motor impairment and absent language
  (NEDMIAL; OMIM:617804) is an ultra-rare Mendelian neurodevelopmental disorder
  caused by rare heterozygous variants in DHX30, which encodes an ATP-dependent
  DExH-box RNA helicase. The defining 2017 series described twelve unrelated
  individuals with global developmental delay, intellectual disability, severe
  speech impairment and gait abnormalities, all carrying de novo missense
  variants in highly conserved helicase core motifs (HCMs). A 2021 study of 25
  further individuals established that the DHX30 allelic spectrum splits into
  two clinically distinct subtypes keyed to variant class. HCM missense variants
  produce the classic severe phenotype: they impair ATPase and RNA-unwinding
  activity and, in addition, confer a detrimental gain of function with respect
  to stress-granule assembly, which interferes with global translation.
  Haploinsufficiency and protein-truncating alleles - and a mosaic HCM missense
  carrier - give a milder course in which affected individuals walk in the second
  year and acquire some speech. The mechanistic reading is therefore not a simple
  dosage lesion: the severe phenotype requires the acquired stress-granule
  property on top of the catalytic loss, which is why halving DHX30 dosage is
  better tolerated than a catalytically dead protein that still assembles into
  granules. DHX30 additionally exists as cytoplasmic and more abundant
  mitochondrially targeted isoforms and contributes to mitoribosomal translation
  and mitochondrial energy metabolism, but that arm has been characterised only
  in cancer-cell models and its contribution to the human neurodevelopmental
  phenotype remains inferred. There is no disease-modifying therapy; care is
  symptomatic, with augmentative communication reported to reduce
  frustration-related behaviour.
disease_term:
  preferred_term: neurodevelopmental disorder with severe motor impairment and absent language
  term:
    id: MONDO:0060622
    label: neurodevelopmental disorder with severe motor impairment and absent language
parents:
- Neurodevelopmental Disorder
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
    evidence:
    - reference: PMID:29100085
      reference_title: De Novo Missense Mutations in DHX30 Impair Global Translation and Cause a Neurodevelopmental Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Here we identified six different de novo missense mutations in DHX30 in
        twelve unrelated individuals affected by global developmental delay
        (GDD), intellectual disability (ID), severe speech impairment and gait
        abnormalities.
      explanation: >-
        Every defining feature of the entity is neurological (developmental
        delay, intellectual disability, speech impairment, gait abnormality),
        placing the entry in the neurologic chapter.
has_subtypes:
- name: HCM missense
  display_name: Helicase-core-motif missense subtype (severe)
  description: >-
    The classic, severe NEDMIAL phenotype, caused by a heterozygous missense
    variant within one of the highly conserved helicase core motifs. All 19
    individuals of this class in the 2021 cohort had global developmental delay,
    intellectual disability, severe speech impairment and gait abnormalities;
    fewer than half achieved independent walking and most were non-verbal. The
    mechanism combines loss of ATPase/helicase activity with a detrimental gain
    of function in stress-granule assembly.
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 19 individuals harboring heterozygous missense variants within
      helicase core motifs (HCMs) have global developmental delay, intellectual
      disability, severe speech impairment, and gait abnormalities.
    explanation: >-
      Defines the severe subtype by variant class and states its obligate
      clinical features in the 19-person group.
- name: Loss of function
  display_name: Haploinsufficiency / protein-truncating subtype (mild)
  description: >-
    A milder clinical course seen in individuals carrying alleles that reduce
    DHX30 dosage or truncate the protein - frameshift, nonsense, whole-gene
    deletion, or in-frame multi-exon deletion. These individuals walked in the
    second year of life, had only mild muscular hypotonia, and spoke at least 20
    words by age three. A de novo mosaic HCM missense carrier fell into the same
    milder band, consistent with the severe phenotype requiring a sufficient
    burden of the mutant protein rather than merely reduced wild-type dosage.
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Notably, 4 individuals harboring heterozygous variants resulting either in
      haploinsufficiency or truncated proteins presented with a milder clinical
      course, similar to an individual harboring a de novo mosaic HCM missense
      variant.
    explanation: >-
      Establishes the milder subtype, its variant classes, and the mosaic
      missense carrier who behaves like it.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      who all learned to walk in the second year of life, had a mild muscular
      hypotonia and spoke at least 20 words by the age of 3 years
    explanation: >-
      Gives the specific developmental milestones that distinguish the mild
      subtype from the severe one.
inheritance:
- name: Autosomal dominant, de novo
  description: >-
    Nearly all reported probands carry a heterozygous de novo DHX30 variant.
    Both the 2017 discovery series and the 2021 cohort are dominated by de novo
    missense alleles, and none of the reported alterations is present in gnomAD
    v2.1.1.
  inheritance_term:
    preferred_term: autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:29100085
    reference_title: De Novo Missense Mutations in DHX30 Impair Global Translation and Cause a Neurodevelopmental Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we identified six different de novo missense mutations in DHX30 in
      twelve unrelated individuals affected by global developmental delay
      (GDD), intellectual disability (ID), severe speech impairment and gait
      abnormalities.
    explanation: >-
      Establishes heterozygous de novo missense variants as the mode of
      inheritance in the defining cohort.
  - reference: PMID:34145223
    reference_title: A Japanese adult and two girls with NEDMIAL caused by de novo missense variants in DHX30.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: NEDMIAL is characterized by severely delayed psychomotor development, which causes an autosomal dominant disorder.
    explanation: >-
      Independent statement that the entity is transmitted as an autosomal
      dominant disorder.
- name: Parental gonadal mosaicism
  description: >-
    Recurrence in siblings born to clinically unaffected, test-negative parents
    has been documented more than once, and is attributed to parental gonadal
    (germline) mosaicism. This is the main counselling caveat in an otherwise de
    novo disorder: negative parental testing on blood does not reduce recurrence
    risk to background. A heterozygous nonsense allele inherited from a mosaic
    mother has also been reported.
  inheritance_term:
    preferred_term: gonadal mosaicism in a clinically unaffected parent
    term:
      id: HP:0001442
      label: Typified by somatic mosaicism
  evidence:
  - reference: PMID:37094863
    reference_title: "DHX30-Associated Neurodevelopmental Disorder with Severe Motor Impairment and Absent Language: First Korean Case in Two Siblings and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The same variant was confirmed in two siblings but not in their parents,
      suggesting the possibility of de novo germline mosaicism.
    explanation: >-
      Documents sibling recurrence with negative parental testing, the
      observation that identifies parental germline mosaicism.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: p.(Arg782Trp) (5 individuals including two half-sisters indicative of gonadal mosaicism)
    explanation: >-
      Independent instance of gonadal mosaicism inferred from two affected
      half-sisters carrying the same recurrent HCM allele.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Twelve unrelated individuals in the 2017 defining series, 25 further
    individuals in the 2021 cohort, plus scattered later case reports. No
    population-based prevalence or incidence estimate exists; the count reflects
    reported cases, not an estimated rate. Ascertainment was partly through a
    Facebook family support group and GeneMatcher, so the reported case series
    are not population samples.
  evidence:
  - reference: PMID:29100085
    reference_title: De Novo Missense Mutations in DHX30 Impair Global Translation and Cause a Neurodevelopmental Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we identified six different de novo missense mutations in DHX30 in
      twelve unrelated individuals affected by global developmental delay
      (GDD), intellectual disability (ID), severe speech impairment and gait
      abnormalities.
    explanation: Establishes the size of the defining cohort.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified 25 previously unreported individuals, ten of whom carry
      novel variants, two of which are recurrent, and provide evidence of
      gonadal mosaicism in one family.
    explanation: >-
      Gives the size of the largest subsequent cohort, supporting an ultra-rare
      cases-in-literature record.
pathophysiology:
- name: Heterozygous DHX30 Helicase Core Motif Missense Variant
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    The severe form of the disorder is initiated by a heterozygous missense
    substitution in one of the eight highly conserved helicase core motifs of
    DHX30. These motifs sit within the two RecA-like domains that jointly form
    the ATP- and RNA-binding surface of an SF2 helicase, so a substitution there
    is positioned to disrupt ATP binding and hydrolysis, RNA recognition, or the
    coupling between them. Recurrent alleles include p.(Arg493His),
    p.(His562Arg), p.(Arg782Trp), p.(Arg785Cys) and p.(Arg785His). None of the
    reported alterations occurs in gnomAD v2.1.1, and DHX30 is among the most
    missense-intolerant genes in the human genome.
  genes:
  - preferred_term: DHX30
    term:
      id: hgnc:16716
      label: DHX30
  evidence:
  - reference: PMID:29100085
    reference_title: De Novo Missense Mutations in DHX30 Impair Global Translation and Cause a Neurodevelopmental Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All amino acid changes are located within highly conserved helicase motifs
      and were found to either impair ATPase activity or RNA recognition in
      different in vitro assays.
    explanation: >-
      Establishes that the causal substitutions fall inside the conserved
      helicase motifs and that this is where the functional lesion arises.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Notably, none of these DHX30 alterations was present in the gnomAD dataset
      v2.1.1
    explanation: >-
      Population-database absence of every reported allele supports their
      causality rather than incidental rarity.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: >-
      Within these two core helicase domains, eight highly conserved sequence
      elements, helicase core motifs (HCMs) play a role in either RNA binding,
      or ATP binding and hydrolysis.
    explanation: >-
      States the structural role of the motifs the disease variants occupy;
      this is a sequence/structure classification rather than a measurement.
  downstream:
  - target: Loss of DHX30 ATPase and RNA Helicase Activity
    causal_link_type: DIRECT
    description: >-
      Substitutions in the ATP- and RNA-binding motifs directly compromise the
      catalytic cycle of the helicase.
  - target: Excess Stress Granule Assembly
    causal_link_type: DIRECT
    description: >-
      The mutant proteins acquire an increased propensity to nucleate stress
      granules, a property that is not explained by loss of catalytic activity
      alone.
- name: DHX30 Haploinsufficiency
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    A separate allelic class - frameshift, nonsense, whole-gene deletion, or
    in-frame multi-exon deletion - reduces the amount of functional DHX30
    produced rather than installing a catalytically dead protein. DHX30 is
    extremely loss-of-function intolerant in population data (pLI 1, LOEUF
    0.04), so this is a real lesion; but clinically it produces the milder
    subtype, which is the observation that separates dosage loss from the
    severe HCM missense mechanism.
  genes:
  - preferred_term: DHX30
    term:
      id: hgnc:16716
      label: DHX30
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Furthermore, we identified four individuals bearing likely pathogenic
      loss-of-function variants.
    explanation: >-
      Establishes the existence of a distinct loss-of-function allelic class in
      the DHX30 disorder.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: >-
      according to the gnomAD v2.1.1 dataset DHX30 is, with a probability of
      being loss-of-function intolerant (pLI) score of 1 and a loss-of-function
      observed/expected upper bound fraction (LOEUF) score of 0.04, extremely
      loss-of-function intolerant
    explanation: >-
      Constraint metrics computed over a population database establish that
      reduced DHX30 dosage is not tolerated, supporting haploinsufficiency as a
      genuine disease mechanism.
  downstream:
  - target: Global Neurodevelopmental Impairment
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Reduced DHX30 dosage produces the milder end of the clinical spectrum.
      The intervening cell-biological steps have not been characterised for this
      allelic class, which notably does not carry the stress-granule gain of
      function.
- name: Loss of DHX30 ATPase and RNA Helicase Activity
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    DHX30 is an ATP-dependent DExH-box RNA helicase that uses ATP hydrolysis to
    unwind RNA secondary structure. HCM missense variants were shown, in
    immunoprecipitated-protein ATPase assays and in a radiolabelled RNA-duplex
    unwinding assay with recombinant protein, to impair both the ATPase and the
    helicase activity of the protein. The 2021 study formally established DHX30
    as an ATP-dependent RNA helicase, so the activity being lost is a directly
    measured one rather than an annotation inherited from family membership.
  genes:
  - preferred_term: DHX30
    term:
      id: hgnc:16716
      label: DHX30
  molecular_functions:
  - preferred_term: RNA helicase activity
    term:
      id: GO:0003724
      label: RNA helicase activity
    modifier: DECREASED
  - preferred_term: ATP hydrolysis activity
    term:
      id: GO:0016887
      label: ATP hydrolysis activity
    modifier: DECREASED
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Protein variants of DHX30 affect ATPase and helicase activity.
    explanation: >-
      Direct biochemical demonstration that the disease variants reduce both
      ATPase and helicase activity, from the immunoprecipitated-protein ATPase
      assay and the recombinant-protein RNA unwinding assay.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: For this, we have now formally confirmed that DHX30 possesses ATP-dependent RNA helicase activity.
    explanation: >-
      Establishes the wild-type activity whose loss this node describes, using
      purified recombinant protein rather than family-membership annotation.
  - reference: PMID:29100085
    reference_title: De Novo Missense Mutations in DHX30 Impair Global Translation and Cause a Neurodevelopmental Disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: DHX30 is a member of the family of DExH-box helicases, which use ATP hydrolysis to unwind RNA secondary structures.
    explanation: >-
      States the coupling between ATP hydrolysis and duplex unwinding that the
      disease variants break.
  downstream:
  - target: Global Translation Inhibition
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Loss of the ATP-driven unwinding step contributes to the translational
      defect, but the measured route from mutant protein to reduced translation
      runs through stress-granule sequestration.
- name: Excess Stress Granule Assembly
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    This is the node that distinguishes the severe subtype from simple dosage
    loss. Overexpressed HCM missense DHX30 protein nucleates cytoplasmic stress
    granules far more readily than wild-type protein, an acquired property that
    the authors classify as a detrimental gain of function layered on top of the
    catalytic loss. Wild-type DHX30 is itself an evolutionarily conserved factor
    in stress-granule assembly, and CRISPR DHX30-deficient HEK293T cells and
    zebrafish show impaired granule assembly - so the mutant proteins push a
    normal DHX30 function past its regulatory setpoint rather than doing
    something DHX30 never does.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: cytoplasmic stress granule assembly
    term:
      id: GO:0034063
      label: cytoplasmic stress granule assembly
    modifier: GAIN_OF_FUNCTION
  evidence:
  - reference: PMID:29100085
    reference_title: De Novo Missense Mutations in DHX30 Impair Global Translation and Cause a Neurodevelopmental Disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Moreover, protein variants exhibit an increased propensity to trigger
      stress granule (SG) formation resulting in global translation inhibition.
    explanation: >-
      Direct cellular demonstration that the disease variants drive excess
      stress-granule formation and that this is what inhibits translation.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Thus, HCM missense variants might actually result in a detrimental
      gain-of-function by inducing SG formation with concomitant global
      translation impairment even without endogenous or exogenous stressors.
    explanation: >-
      The authors' cellular interpretation: the stress-granule gain of function
      is constitutive, occurring without an applied stressor, which is what makes
      it a disease mechanism rather than an exaggerated stress response.
  downstream:
  - target: Global Translation Inhibition
    causal_link_type: DIRECT
    description: >-
      Sequestration of mRNA-protein complexes into stress granules withdraws
      transcripts from active translation.
- name: Global Translation Inhibition
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Cells expressing HCM missense DHX30 show reduced global protein synthesis,
    measured by puromycin incorporation. This is the cellular endpoint the
    discovery paper named in its title and is the best-established consequence
    of the severe-subtype alleles. Note the direction is variant-class specific:
    depleting DHX30 in cancer cells raises rather than lowers global translation,
    so translational inhibition here is a property of the mutant protein, not of
    reduced DHX30 dosage.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: translation
    term:
      id: GO:0006412
      label: translation
    modifier: DECREASED
  - preferred_term: regulation of translation
    term:
      id: GO:0006417
      label: regulation of translation
    modifier: ABNORMAL
  evidence:
  - reference: PMID:29100085
    reference_title: De Novo Missense Mutations in DHX30 Impair Global Translation and Cause a Neurodevelopmental Disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Moreover, protein variants exhibit an increased propensity to trigger
      stress granule (SG) formation resulting in global translation inhibition.
    explanation: >-
      Names global translation inhibition as the measured downstream
      consequence of the variant-driven stress-granule phenotype.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      We have previously shown that the expression of mutant forms of DHX30
      induces the formation of stress granules, concomitant with a global
      down-regulation of translation
    explanation: >-
      Ties the translational down-regulation directly to the stress-granule
      phenotype in the same cellular system, which is the upstream node here.
  - reference: PMID:34503222
    reference_title: DHX30 Coordinates Cytoplasmic Translation and Mitochondrial Function Contributing to Cancer Cell Survival.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: IN_VITRO
    snippet: >-
      Furthermore, the depletion of both DHX30 isoforms leads to higher global
      translation but slower proliferation and lower mitochondrial energy
      metabolism.
    explanation: >-
      Cited to constrain, not to extend, the claim: losing DHX30 raises global
      translation, which is the opposite direction from the mutant protein. The
      inference step is that translational inhibition must therefore be a
      property of the HCM missense allele rather than of reduced DHX30 dosage.
  downstream:
  - target: Disrupted Brain Development
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The specific transcripts whose translational failure produces human
      cortical and cerebellar findings have not been identified, and the step
      has not been demonstrated in patient-derived neurons, so at least one
      required intermediate is unknown.
- name: Impaired Mitochondrial Translation and Energy Metabolism
  biological_scale: CELLULAR
  mechanism_confidence: HYPOTHETICAL
  description: >-
    DHX30 is transcribed from two alternative promoters into a cytoplasmic form
    and a more abundant mitochondrially targeted form, and it associates with
    nuclear-encoded mitoribosome transcripts. Depleting both isoforms in
    colorectal carcinoma cells reduces the translational efficiency of
    mitoribosome mRNAs and lowers mitochondrial energy metabolism. This node is
    recorded as a plausible parallel arm rather than an established disease
    mechanism: every measurement supporting it was made in non-neural cancer
    cell lines under isoform depletion, which is the loss-of-function
    configuration, whereas the severe human phenotype is driven by a
    catalytically dead protein. No mitochondrial readout has been reported in
    NEDMIAL patient material.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  biological_processes:
  - preferred_term: mitochondrial translation
    term:
      id: GO:0032543
      label: mitochondrial translation
    modifier: DECREASED
  evidence:
  - reference: PMID:34503222
    reference_title: DHX30 Coordinates Cytoplasmic Translation and Mitochondrial Function Contributing to Cancer Cell Survival.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: IN_VITRO
    snippet: >-
      The depletion of both DHX30 isoforms in HCT116 cells leads to constitutive
      changes in polysome-associated mRNAs, enhancing the translation of mRNAs
      coding for cytoplasmic ribosomal proteins while reducing the translational
      efficiency of the nuclear-encoded mitoribosome mRNAs.
    explanation: >-
      Establishes the mitoribosomal translation arm of DHX30 biology. Indirect
      for this disease because it is measured in a colorectal carcinoma line
      under isoform depletion, not in neurons carrying a disease allele.
  - reference: PMID:34503222
    reference_title: DHX30 Coordinates Cytoplasmic Translation and Mitochondrial Function Contributing to Cancer Cell Survival.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: IN_VITRO
    snippet: >-
      Here, we show that DHX30 exhibits a more general function by integrating
      the activities of its cytoplasmic isoform and of the more abundant
      mitochondrial one.
    explanation: >-
      Documents the dual-isoform architecture that makes a mitochondrial
      contribution to the disorder biologically plausible.
  downstream:
  - target: Disrupted Brain Development
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      A hypothetical contribution. The developing brain is energy-demanding, so
      a mitoribosomal translation deficit would plausibly affect it, but no step
      of this route has been demonstrated in a neural system or in patients.
- name: Disrupted Brain Development
  biological_scale: TISSUE
  mechanism_confidence: PROVISIONAL
  description: >-
    Structural brain anomalies are found on MRI in roughly two-thirds of
    severe-subtype individuals, and DHX30 is required for central-nervous-system
    development in mouse, where homozygous deletion is embryonic lethal with
    early CNS developmental defects. Expressing pathogenic DHX30 variants in
    zebrafish embryos causes developmental defects. The node is provisional
    because no consistent human malformation signature exists - MRI may be
    normal - and because the link from the cellular translational lesion to the
    tissue phenotype has not been traced in human neural tissue.
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  cell_types:
  - preferred_term: neural stem cell
    term:
      id: CL:0000047
      label: neural stem cell
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: brain development
    term:
      id: GO:0007420
      label: brain development
    modifier: ABNORMAL
  - preferred_term: neuron differentiation
    term:
      id: GO:0030182
      label: neuron differentiation
    modifier: ABNORMAL
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: structural brain anomalies in eleven (65%, 11/17)
    explanation: >-
      Quantifies structural brain involvement in the severe-subtype cohort,
      establishing the tissue-level abnormality this node describes.
  - reference: PMID:34145223
    reference_title: A Japanese adult and two girls with NEDMIAL caused by de novo missense variants in DHX30.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      The homozygous deletion of DHX30 leads to early embryonic lethality and
      causes early developmental defects in the central nervous system in mice
    explanation: >-
      Establishes a requirement for DHX30 in mammalian CNS development. Graded
      MODEL_ORGANISM because the observation is a mouse whole-organism result.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      These variants impair the ATPase and helicase activity of DHX30, trigger
      SG formation, interfere with global translation, and cause developmental
      defects in a zebrafish model.
    explanation: >-
      The human disease alleles themselves produce developmental defects in a
      vertebrate embryo, linking the molecular lesion to disturbed development.
  downstream:
  - target: Global Neurodevelopmental Impairment
    causal_link_type: DIRECT
    description: >-
      Abnormal brain structure and development is the tissue-level substrate of
      the intellectual disability, motor impairment and absent language observed
      clinically.
- name: Global Neurodevelopmental Impairment
  biological_scale: ORGANISM
  mechanism_confidence: ESTABLISHED
  description: >-
    The organism-level convergence point: global developmental delay,
    intellectual disability, severe or absent expressive speech, muscular
    hypotonia, and severely impaired or absent independent gait. This is the
    node from which the clinical phenotype layer of this entry is reached, and
    it is where the two variant-class subtypes differ in degree rather than in
    kind.
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 19 individuals harboring heterozygous missense variants within
      helicase core motifs (HCMs) have global developmental delay, intellectual
      disability, severe speech impairment, and gait abnormalities.
    explanation: >-
      Enumerates the organism-level clinical features that define the disorder
      in its severe form.
  - reference: PMID:34145223
    reference_title: A Japanese adult and two girls with NEDMIAL caused by de novo missense variants in DHX30.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The affected patients show muscular hypotonia, feeding difficulties,
      ataxic gait, or an inability to walk.
    explanation: >-
      Independent restatement of the organism-level motor phenotype.
phenotypes:
- category: Nervous System
  name: Global developmental delay
  subtype: HCM missense
  description: >-
    Global developmental delay is present in every reported individual carrying
    a helicase-core-motif missense variant and was the presenting feature of the
    2017 discovery series. It spans gross motor, fine motor, and speech and
    language domains.
  frequency: OBLIGATE
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 19 individuals harboring heterozygous missense variants within
      helicase core motifs (HCMs) have global developmental delay, intellectual
      disability, severe speech impairment, and gait abnormalities.
    explanation: >-
      19/19 of the helicase-core-motif missense group, which is why the
      frequency band is OBLIGATE and why the phenotype is scoped to that
      subtype rather than to the whole entry.
  sequelae:
  - target: Intellectual disability
    causal_link_type: DIRECT
    description: The cognitive domain of the global delay.
- category: Nervous System
  name: Intellectual disability
  subtype: HCM missense
  description: >-
    Impaired intellectual development is a constant feature of the severe
    subtype and is generally severe. The single mosaic HCM missense carrier had
    only moderate intellectual disability, which is part of the evidence that
    mutant-protein burden sets severity.
  frequency: OBLIGATE
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In more detail, all individuals had an intellectual disability, only nine (47%) learned to walk, all with an ataxic gait.
    explanation: >-
      Explicit statement that intellectual disability was present in all
      individuals of the severe-subtype group.
- category: Nervous System
  name: Absent speech
  subtype: HCM missense
  description: >-
    Absent or minimal expressive language is the feature the entity is named
    for. Most severe-subtype individuals are non-verbal; a minority speak single
    words only. Receptive ability is better than expressive ability in at least
    some individuals, which is the rationale for augmentative communication.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Absent speech
    term:
      id: HP:0001344
      label: Absent speech
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The majority had no speech (74%), four individuals spoke only single
      words, and only individual 6, who is mosaic for the de novo
      p.(Ala734Asp) variant, spoke simple sentences.
    explanation: >-
      74% non-verbal in the severe-subtype group places the frequency in the
      FREQUENT (30-79%) band.
- category: Nervous System
  name: Motor delay
  subtype: HCM missense
  description: >-
    Gross and fine motor development is delayed in every severe-subtype
    individual. Fewer than half ever achieve independent walking.
  frequency: OBLIGATE
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In more detail, all individuals had an intellectual disability, only nine (47%) learned to walk, all with an ataxic gait.
    explanation: >-
      Only 47% of the severe-subtype group learned to walk at all, establishing
      obligate motor delay in that group.
  sequelae:
  - target: Gait ataxia
    causal_link_type: DIRECT
    description: >-
      Those who do achieve ambulation do so with an abnormal, ataxic pattern.
- category: Nervous System
  name: Gait ataxia
  subtype: HCM missense
  description: >-
    Every severe-subtype individual who learned to walk did so with an ataxic
    gait; the remainder never achieved independent ambulation. Gait abnormality
    is one of the four features present in all 19 severe-subtype individuals.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Ataxic gait
    term:
      id: HP:0002066
      label: Gait ataxia
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In more detail, all individuals had an intellectual disability, only nine (47%) learned to walk, all with an ataxic gait.
    explanation: >-
      Ataxic gait in 9/19 (47%) of the severe-subtype group - all of those who
      walk - which is the FREQUENT band. The remainder are non-ambulant rather
      than normally ambulant.
- category: Musculoskeletal
  name: Hypotonia
  subtype: HCM missense
  description: >-
    Muscular hypotonia is near-universal in the severe subtype and is often the
    presenting sign in infancy. Individuals in the milder loss-of-function
    subtype have hypotonia too, but it is mild.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Muscular hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional phenotypic features included muscular hypotonia in eighteen
      (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen
      (81%, 13/16), joint hypermobility in fourteen (74%), structural brain
      anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%),
      strabismus in eight (42%), autistic features in five (33%, 5/15), and
      seizures in four (21%) individuals
    explanation: >-
      Hypotonia in 95% of the severe-subtype group places it in the
      VERY_FREQUENT (80-99%) band.
- category: Gastrointestinal
  name: Feeding difficulties
  subtype: HCM missense
  description: >-
    Feeding difficulty is common from infancy and is one of the main drivers of
    care burden, contributing to poor growth in some individuals.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional phenotypic features included muscular hypotonia in eighteen
      (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen
      (81%, 13/16), joint hypermobility in fourteen (74%), structural brain
      anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%),
      strabismus in eight (42%), autistic features in five (33%, 5/15), and
      seizures in four (21%) individuals
    explanation: >-
      Feeding difficulties in 84% of the severe-subtype group, the
      VERY_FREQUENT band.
- category: Head and Neck
  name: Microcephaly
  subtype: HCM missense
  description: >-
    Acquired or congenital small head circumference is reported in most
    severe-subtype individuals in whom it was assessed. It was absent in all
    four individuals of the milder loss-of-function subtype.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional phenotypic features included muscular hypotonia in eighteen
      (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen
      (81%, 13/16), joint hypermobility in fourteen (74%), structural brain
      anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%),
      strabismus in eight (42%), autistic features in five (33%, 5/15), and
      seizures in four (21%) individuals
    explanation: >-
      Microcephaly in 81% (13/16 assessed) of the severe-subtype group, the
      VERY_FREQUENT band.
- category: Musculoskeletal
  name: Joint hypermobility
  subtype: HCM missense
  description: >-
    Generalised joint hypermobility is common and, together with hypotonia,
    contributes to the motor disability. Atraumatic dislocation and contractures
    have been described in individual cases.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Joint hypermobility
    term:
      id: HP:0001382
      label: Joint hypermobility
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional phenotypic features included muscular hypotonia in eighteen
      (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen
      (81%, 13/16), joint hypermobility in fourteen (74%), structural brain
      anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%),
      strabismus in eight (42%), autistic features in five (33%, 5/15), and
      seizures in four (21%) individuals
    explanation: >-
      Joint hypermobility in 74% of the severe-subtype group, the FREQUENT
      (30-79%) band.
- category: Nervous System
  name: Abnormal brain morphology
  subtype: HCM missense
  description: >-
    Brain MRI is abnormal in about two-thirds of severe-subtype individuals but
    may be entirely normal. Reported findings are heterogeneous - delayed
    myelination, reduced white matter, ventriculomegaly, cerebral or cerebellar
    atrophy, corpus-callosum abnormalities - with no single diagnostic
    signature, which is why the honest binding is the parent term rather than a
    specific malformation.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Structural brain anomaly on MRI
    term:
      id: HP:0012443
      label: Abnormal brain morphology
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: structural brain anomalies in eleven (65%, 11/17)
    explanation: >-
      Structural brain anomalies in 65% (11/17 imaged) of the severe-subtype
      group, the FREQUENT band.
- category: Nervous System
  name: Sleep disturbance
  subtype: HCM missense
  description: >-
    Disturbed sleep affects about half of severe-subtype individuals and is a
    significant contributor to family burden. Altered sleep-wake activity is one
    of the two behavioural abnormalities recapitulated in dhx30-deficient
    zebrafish.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional phenotypic features included muscular hypotonia in eighteen
      (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen
      (81%, 13/16), joint hypermobility in fourteen (74%), structural brain
      anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%),
      strabismus in eight (42%), autistic features in five (33%, 5/15), and
      seizures in four (21%) individuals
    explanation: >-
      Sleep disturbance in 47% of the severe-subtype group, the FREQUENT band.
- category: Eye
  name: Strabismus
  subtype: HCM missense
  description: >-
    Ocular misalignment is a common accompanying feature. Nystagmus has also
    been reported in a substantial minority of individuals across series.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional phenotypic features included muscular hypotonia in eighteen
      (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen
      (81%, 13/16), joint hypermobility in fourteen (74%), structural brain
      anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%),
      strabismus in eight (42%), autistic features in five (33%, 5/15), and
      seizures in four (21%) individuals
    explanation: >-
      Strabismus in 42% of the severe-subtype group, the FREQUENT band.
- category: Behavioral
  name: Autistic behavior
  subtype: HCM missense
  description: >-
    Autistic features, stereotypies including hand-flapping, and low frustration
    tolerance are reported in a third of assessed severe-subtype individuals.
    Reduced social preference is the second behavioural abnormality
    recapitulated in dhx30-deficient zebrafish.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Autistic behavior
    term:
      id: HP:0000729
      label: Autistic behavior
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional phenotypic features included muscular hypotonia in eighteen
      (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen
      (81%, 13/16), joint hypermobility in fourteen (74%), structural brain
      anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%),
      strabismus in eight (42%), autistic features in five (33%, 5/15), and
      seizures in four (21%) individuals
    explanation: >-
      Autistic features in 33% (5/15 assessed) of the severe-subtype group, at
      the lower edge of the FREQUENT band.
  - reference: PMID:34145223
    reference_title: A Japanese adult and two girls with NEDMIAL caused by de novo missense variants in DHX30.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is also characterized by behavioral abnormalities, such as autistic
      features, low frustration tolerance, hand-flapping, and stereotypies.
    explanation: >-
      Independent characterisation of the behavioural phenotype, including the
      specific stereotypies.
- category: Nervous System
  name: Seizure
  subtype: HCM missense
  description: >-
    Seizures occur in a minority and are not a defining feature of the disorder.
    Epileptiform EEG activity without clinical seizures has also been described.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional phenotypic features included muscular hypotonia in eighteen
      (95%), feeding difficulties in sixteen (84%), microcephaly in thirteen
      (81%, 13/16), joint hypermobility in fourteen (74%), structural brain
      anomalies in eleven (65%, 11/17), sleep disturbances in nine (47%),
      strabismus in eight (42%), autistic features in five (33%, 5/15), and
      seizures in four (21%) individuals
    explanation: >-
      Seizures in 21% of the severe-subtype group, the OCCASIONAL (5-29%) band.
genetic:
- name: DHX30
  gene_term:
    preferred_term: DHX30
    term:
      id: hgnc:16716
      label: DHX30
  presence: PRESENT
  relationship_type: CAUSATIVE
  variant_origin: DE_NOVO
  association: >-
    DHX30 (DExH-box helicase 30) at 3p21.31 is the single causal gene. Two
    allelic classes with different functional consequences produce two
    clinically distinct subtypes. Heterozygous missense variants inside the
    conserved helicase core motifs cause the severe classic phenotype; recurrent
    alleles include p.(Arg493His), p.(His562Arg), p.(Arg782Trp), p.(Arg785Cys)
    and p.(Arg785His). These impair ATPase and RNA-unwinding activity and
    additionally confer a detrimental gain of function in stress-granule
    assembly. The severe phenotype therefore requires the mutant protein to be
    present rather than merely the wild-type dosage to be halved - a mosaic
    carrier and four haploinsufficient individuals were all mild. No
    functional_impact_category is recorded here because that slot belongs to a
    per-variant GeneticContext and this entry does not curate variant-level
    allele/zygosity detail; the two allelic classes are instead modelled as
    separate pathophysiology nodes and has_subtypes entries. Causality rests on de novo recurrence
    across unrelated families, absence from gnomAD v2.1.1, extreme constraint
    (pLI 1, LOEUF 0.04), biochemical assays of ATPase and helicase activity,
    stress-granule and puromycin-incorporation assays in cultured cells, and
    developmental defects in zebrafish embryos expressing the human variants.
  evidence:
  - reference: PMID:29100085
    reference_title: De Novo Missense Mutations in DHX30 Impair Global Translation and Cause a Neurodevelopmental Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we identified six different de novo missense mutations in DHX30 in
      twelve unrelated individuals affected by global developmental delay
      (GDD), intellectual disability (ID), severe speech impairment and gait
      abnormalities.
    explanation: >-
      Establishes the gene-disease relationship through de novo recurrence in
      twelve unrelated probands.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      DHX30 loss-of-function variants cause a milder phenotype whereas a severe
      phenotype is caused by HCM missense variants that, in addition to the loss
      of ATPase and helicase activity, lead to a detrimental gain-of-function
      with respect to SG formation.
    explanation: >-
      States the allele-class-to-mechanism-to-severity mapping that this genetic
      record encodes.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: As previously noted, DHX30 is one of the most missense-intolerant genes in the human genome
    explanation: >-
      Population-constraint evidence that missense variation in DHX30 is
      strongly selected against, consistent with missense alleles being the
      severe disease class.
animal_models:
- name: dhx30 CRISPR knockout zebrafish
  species: Zebrafish
  genotype: dhx30 8-bp frameshift deletion (premature stop at amino acid 107), homozygous and heterozygous
  publication: PMID:34020708
  description: >-
    A stable CRISPR/Cas9 dhx30 knockout zebrafish line generated to test the
    consequences of losing dhx30 rather than of expressing a mutant protein.
    Unlike the mouse null, it is viable and grossly normal, which is what makes
    it usable for behavioural work.
  modeled_mechanisms:
  - target: Excess Stress Granule Assembly
    relationship: PERTURBS
    fidelity: MODERATE
    description: >-
      Losing dhx30 impairs stress-granule assembly, establishing that dhx30 is
      a conserved positive factor in granule formation. This is the mirror image
      of the human disease allele, which drives excess granules.
    limitations: >-
      This is a loss-of-function model and therefore perturbs the node in the
      opposite direction from the human severe-subtype variant; it establishes
      that dhx30 acts on granule assembly, not that patients have too few
      granules.
    evidence:
    - reference: PMID:34020708
      reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Thus, these data show that SG formation is compromised in the homozygous
        mutants and suggests an evolutionarily conserved role for DHX30 in SG
        assembly.
      explanation: >-
        The zebrafish-specific result behind the conservation claim: homozygous
        dhx30 mutants form fewer stress granules, establishing that this model
        perturbs the node.
  - target: Global Neurodevelopmental Impairment
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      dhx30-deficient larvae show altered sleep-wake activity and reduced social
      preference, matching the sleep disturbance and autistic features seen in
      patients.
    limitations: >-
      Only the two behavioural domains are reproduced. The model is a null
      rather than an HCM missense allele, is viable and morphologically normal,
      and does not reproduce the defining severe motor impairment, absent
      language, or intellectual disability - which have no zebrafish
      counterpart in any case.
    readouts:
    - name: Larval sleep-wake activity over a 24-hour light-dark cycle
      target: Global Neurodevelopmental Impairment
      direction: ALTERED
      interpretation: >-
        Behavioural correlate of the sleep disturbance reported in about half of
        severe-subtype patients.
      evidence:
      - reference: PMID:34020708
        reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Behavioral characterization of dhx30-deficient zebrafish revealed
          altered sleep-wake activity and social interaction, partially
          resembling the human phenotype.
        explanation: Reports the sleep-wake measurement behind this readout.
    - name: Social preference index
      target: Global Neurodevelopmental Impairment
      direction: DECREASED
      interpretation: >-
        Behavioural correlate of the autistic features and impaired social
        communication reported in patients.
      evidence:
      - reference: PMID:34020708
        reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Behavioral characterization of dhx30-deficient zebrafish revealed
          altered sleep-wake activity and social interaction, partially
          resembling the human phenotype.
        explanation: Reports the social-interaction measurement behind this readout.
    evidence:
    - reference: PMID:34020708
      reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Behavioral characterization of dhx30-deficient zebrafish revealed
        altered sleep-wake activity and social interaction, partially
        resembling the human phenotype.
      explanation: >-
        The authors' own assessment that the model partially resembles the human
        phenotype supports treating it as informative for this node.
- name: DHX30 variant-expressing zebrafish embryos
  species: Zebrafish
  genotype: tuba1a-driven expression of wild-type or HCM-missense human DHX30 cDNA
  publication: PMID:34020708
  description: >-
    Human DHX30 cDNA carrying each candidate missense variant was expressed in
    one-cell-stage embryos under a neural promoter and embryos were scored for
    abnormal development. This is the in vivo arm of the variant-classification
    workflow, and it tests the mutant protein rather than gene loss.
  modeled_mechanisms:
  - target: Disrupted Brain Development
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Expressing the human disease alleles causes developmental defects in the
      embryo, directly connecting the molecular lesion to disturbed development
      in a vertebrate.
    limitations: >-
      Scored as gross embryonic developmental defects over 1-7 days post
      fertilisation under overexpression from a heterologous promoter, so
      neither the dosage nor the specific human cortical and cerebellar findings
      are modelled.
    evidence:
    - reference: PMID:34020708
      reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        These variants impair the ATPase and helicase activity of DHX30, trigger
        SG formation, interfere with global translation, and cause developmental
        defects in a zebrafish model.
      explanation: >-
        The human disease alleles produce developmental defects in vivo,
        supporting this model as informative for the development node.
treatments:
- name: Augmentative and Alternative Communication
  description: >-
    Tablet, smartphone, and eye-gaze-driven communication systems. Reported by
    the largest cohort study to substantially reduce frustration-related
    behaviour in non-verbal individuals - the only intervention in this disorder
    for which a specific benefit has been described in the primary literature,
    though the observation is investigator communication with families rather
    than a controlled study.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: augmentative and alternative communication training
    term:
      id: NCIT:C159273
      label: Speech Language Therapy
  target_mechanisms:
  - target: Global Neurodevelopmental Impairment
    treatment_effect: MODULATES
    description: >-
      Does not alter the underlying lesion; provides an expressive channel that
      bypasses the absent-speech component of the organism-level phenotype.
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is worth noting that the individuals highly benefit from communication
      devices (tablets, smartphones, and eye-driven tablet communication
      systems) which significantly reduced frustration-related behavior
    explanation: >-
      Directly reports benefit from augmentative communication devices in this
      patient group.
- name: Physical Therapy and Motor Rehabilitation
  description: >-
    Physiotherapy, positioning and mobility aids for the hypotonia, ataxia and
    joint hypermobility. Extrapolated from general management of severe
    neurodevelopmental motor disability; no DHX30-specific outcome data exist.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: physical therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  target_mechanisms:
  - target: Global Neurodevelopmental Impairment
    treatment_effect: MODULATES
    description: >-
      Symptomatic support of the motor phenotype; does not act on the
      translational lesion.
  evidence:
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In more detail, all individuals had an intellectual disability, only nine (47%) learned to walk, all with an ataxic gait.
    explanation: >-
      Establishes the severe ambulation deficit and ataxia that motor
      rehabilitation targets. It does not evaluate physiotherapy, which has no
      disease-specific trial evidence.
- name: Genetic Counseling
  description: >-
    Counselling centres on recurrence risk. The disorder is usually de novo, but
    documented parental gonadal mosaicism means that negative parental testing
    on blood does not reduce recurrence risk to the population background, and
    sibling recurrence has been reported more than once. Counselling should also
    convey that variant class predicts severity band.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:37094863
    reference_title: "DHX30-Associated Neurodevelopmental Disorder with Severe Motor Impairment and Absent Language: First Korean Case in Two Siblings and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The same variant was confirmed in two siblings but not in their parents,
      suggesting the possibility of de novo germline mosaicism.
    explanation: >-
      The sibling recurrence with negative parental testing is precisely the
      counselling scenario this entry flags.
definitions:
- definition_type: DIAGNOSTIC_CRITERIA
  name: Molecular diagnosis of DHX30-related neurodevelopmental disorder
  description: >-
    Diagnosis requires identification of a pathogenic or likely pathogenic DHX30
    variant, in practice by trio exome or genome sequencing. Chromosomal
    microarray detects only the deletion alleles. Because variant class predicts
    the severity band, classifying the variant as a helicase-core-motif missense
    versus a loss-of-function allele is part of the diagnostic assessment, as is
    evaluating parents for mosaicism when a sibling is affected.
  derivation_basis: ESTABLISHED_CRITERIA
  evidence:
  - reference: PMID:37094863
    reference_title: "DHX30-Associated Neurodevelopmental Disorder with Severe Motor Impairment and Absent Language: First Korean Case in Two Siblings and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We performed whole-exome sequencing using genomic deoxyribonucleic acid
      isolated from buccal swabs, which revealed a heterozygous missense variant
      of DHX30: (c.2344C>T, p.Arg782Trp).
    explanation: >-
      Worked example of the diagnostic route: exome sequencing identifying the
      causal DHX30 variant.
  - reference: PMID:34020708
    reference_title: Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Classification the identified variants was based on the American College
      of Medical Genetics and Genomics (ACMG) guidelines
    explanation: >-
      Records the variant-classification standard applied in the defining
      cohort.
discussions:
- discussion_id: dhx30_mitochondrial_arm_translational_validity
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    Does the mitoribosomal-translation and mitochondrial-energy-metabolism
    function of DHX30, characterised entirely by depleting both isoforms in
    cancer cell lines, contribute to the human neurodevelopmental phenotype
    caused by helicase-core-motif missense alleles?
  rationale: >-
    The mismatch is directional as well as contextual. Every measurement
    supporting the mitochondrial arm comes from depleting DHX30 in HCT116, U2OS
    or MCF7 cells - the loss-of-function configuration, which in humans produces
    the mild subtype. The severe human phenotype is caused by a catalytically
    dead protein that is still expressed and still assembles into granules. The
    same study shows the two configurations diverge on the cytoplasmic readout,
    since depletion raises global translation while the missense variants lower
    it, so there is a positive reason not to assume the mitochondrial readout
    transfers either. No mitochondrial measurement has been made in a neuron, an
    NEDMIAL patient cell, or an HCM-variant-expressing system.
  attaches_to:
  - pathophysiology#Impaired Mitochondrial Translation and Energy Metabolism
  proposed_experiments:
  - experiment_id: dhx30_mito_readout_in_hcm_variant_neurons
    name: Mitochondrial translation and respiration in HCM-variant neural cells
    description: >-
      Introduce a recurrent HCM missense allele (for example p.Arg782Trp) into
      human iPSC-derived neurons or neural progenitors at the endogenous locus,
      and measure mitoribosomal-transcript translational efficiency, mitochondrial
      protein synthesis and oxygen consumption rate against isogenic wild-type
      and DHX30-heterozygous-null controls. Including the heterozygous null arm
      is what separates a dosage effect from a mutant-protein effect.
    would_support:
    - pathophysiology#Impaired Mitochondrial Translation and Energy Metabolism
    supporting_outcome:
    - >-
      HCM-variant neurons show reduced mitoribosome translational efficiency and
      reduced oxygen consumption relative to isogenic wild-type controls.
    would_refute:
    - pathophysiology#Impaired Mitochondrial Translation and Energy Metabolism
    refuting_outcome:
    - >-
      Mitoribosomal translational efficiency and respiration are unchanged in
      HCM-variant neurons, or are altered only in the heterozygous-null arm,
      indicating the mitochondrial arm belongs to dosage loss and not to the
      severe disease mechanism.
- discussion_id: dhx30_no_patient_derived_neural_model
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What happens to stress-granule dynamics and translational output in human
    neurons carrying an endogenous DHX30 helicase-core-motif missense variant?
  rationale: >-
    The stress-granule and translation phenotypes were established by
    overexpressing GFP-tagged variant DHX30 in HEK293T and U2OS cells - a
    kidney line and an osteosarcoma line, at non-physiological levels. The step
    from the cellular translational lesion to impaired neuronal differentiation
    and circuit formation is the weakest link in the causal chain and is
    currently pure inference. No iPSC-derived neuron, organoid, or post-mortem
    study of an affected individual has been reported.
  attaches_to:
  - pathophysiology#Global Translation Inhibition
  - pathophysiology#Disrupted Brain Development
- discussion_id: dhx30_no_natural_history_or_prevalence
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What is the population prevalence of DHX30-related neurodevelopmental
    disorder, and what is the natural history into adulthood?
  rationale: >-
    All reported individuals come from case series ascertained through
    diagnostic sequencing, GeneMatcher, and a Facebook family support group, so
    published feature frequencies are vulnerable to ascertainment bias and there
    is no denominator. Adult outcome data are limited to isolated reports. This
    matters practically: the 47% ambulation and 74% non-verbal figures are the
    numbers families are counselled with, and they derive from 19 people.
  attaches_to:
  - prevalence#Worldwide
  - phenotypes#Absent speech
notes: >-
  Lump/split decision: curated as a standalone DISEASE entry anchored on
  MONDO:0060622. DHX30 had no entry in dismech before this one. The two clinical
  subtypes that Mannucci et al. established - helicase-core-motif missense
  (severe) and haploinsufficiency/truncating (mild) - are modelled as
  has_subtypes within this single entry rather than as two entries, because the
  mild form has no separate MONDO or OMIM identity and the two share the same
  gene, the same core clinical axes, and one of the two mechanistic nodes.
  Phenotype frequency bands are scoped to the HCM missense subtype throughout,
  since that is the group the published numerators describe; the mild subtype's
  features are recorded in its subtype description rather than duplicated as
  separately banded phenotypes for a four-person group.

  Not the same disorder as Neurodevelopmental_Disorder_with_Hypotonia_and_Speech_Delay,
  which is the EIF4A2 entity NEDHSS (MONDO:0957541). The two are worth reading
  together as translational-machinery neurodevelopmental disorders - EIF4A2 is a
  DEAD-box helicase of translation initiation, DHX30 a DExH-box helicase - but
  they are different genes, different MONDO terms, and different mechanisms
  (initiation/miRNA repression versus stress-granule gain of function).

  The falcon deep-research report for this disease passed preflight-dr against
  MONDO:0060622 and was used only as a lead. It carried no PMIDs, so every
  reference here was independently searched on PubMed and fetched; the report's
  own citation keys were not used. Two PMIDs recalled from memory during
  drafting resolved to unrelated papers and were discarded rather than cited.