NEUROD2-Related Developmental and Epileptic Encephalopathy

Mendelian MONDO:0032710 Pathograph 10 Show in embeddings browser Epilepsy Neurological Disease

NEUROD2-related developmental and epileptic encephalopathy (DEE72) is caused by heterozygous de novo variants in NEUROD2, a class II basic helix-loop-helix proneural transcription factor that dimerises with E-proteins to bind E-box elements in the promoters of neuronal differentiation genes. It is unusual among the developmental and epileptic encephalopathies in that the primary lesion is transcriptional rather than in a channel, synaptic protein or trafficking component, so the disorder arises from mis-specified cortical development rather than from a directly altered conductance. The phenotype has since broadened well past the epileptic encephalopathy it was named for: the core of the disorder is a neurodevelopmental syndrome centred on autistic features, intellectual disability and speech disturbance, of which epilepsy is one non-fully-penetrant branch - present in 3 of 7 assessed patients in the defining cohort, and absent altogether in at least one reported carrier with developmental delay.

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1
Inheritance
7
Pathophys.
8
Phenotypes
3
Gaps
10
Pathograph
1
Genes
3
Medical Actions
3
Models
1
Deep Research
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Inheritance

1
Autosomal dominant HP:0000006
Heterozygous and de novo.
Autosomal dominant inheritance
Show evidence (1 reference)
PMID:30323019 SUPPORT Human Clinical
"We identified novel de novo variants in neuronal differentiation factor 2 (NEUROD2) in two unrelated children with early infantile epileptic encephalopathy"
Establishes the de novo heterozygous architecture in the founding pair of patients.
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Discussions and Knowledge Gaps

3
Is the blood-brain barrier defect part of the human disorder, or a feature of the tadpole model?
HUMAN MODEL MISMATCH OPEN mismatch_bbb_arm_rests_entirely_on_tadpole
Attached to
pathophysiology#Blood-Brain Barrier Permeability
This is the entry's most interesting claim and its least established. A leaky blood-brain barrier is a non-neuronal contributor to epileptogenesis in a disorder caused by a neuronal transcription factor, and the losartan experiment gives it causal weight in the model: a TGF-beta antagonist reduced both barrier permeability and seizure events more than four-fold. But every part of that sits in Xenopus. No human data establish altered barrier permeability in NEUROD2 patients. The stake is unusually concrete, because losartan is an approved drug in wide human use, so a positive human finding would point directly at a repurposing candidate - and a negative one would remove the rationale entirely. The rescue is also described by its own authors as short-term, so even within the model durability is unestablished.
Proposed experiments
Barrier integrity in NEUROD2 patients
exp_bbb_integrity_in_neurod2_patients
Assess blood-brain barrier integrity in genotype-confirmed NEUROD2 patients using contrast-enhanced imaging or CSF-to-serum protein ratios, and compare against age-matched epilepsy controls, to determine whether the tadpole finding has a human counterpart before any repurposing trial is contemplated.
Can a lissencephalic, unlayered, outside-in brain test a mechanism defined by inside-out radial migration into a six-layered cortex?
HUMAN MODEL MISMATCH OPEN mismatch_lissencephalic_model_for_a_lamination_mechanism
Attached to
pathophysiology#Disrupted Cortical Neuron Migration and Lamination
The proposed human mechanism runs through disrupted radial migration and layer-specific differentiation of cortical projection neurons. The principal in vivo model is the Xenopus tadpole, whose forebrain is lissencephalic and unlayered and forms from the outside in, so the oldest neurons end up outermost - the opposite ordering to the human neocortex. The model therefore cannot test the lamination step it is being used to support; what it can show is that reduced NeuroD2 activity produces seizures and network hyperactivity, which it does. The mouse work on cortical over-migration and layer 5 positioning is the better-matched evidence for the lamination arm, and this entry marks the edge from lamination to hyperactivity as indirect with unknown intermediates rather than treating the tadpole seizure phenotype as confirmation of the migration account.
Proposed experiments
Layer-resolved migration phenotype in a layered cortex
exp_layer_resolved_migration_in_a_gyrencephalic_model
Characterise laminar position and radial migration of cortical projection neurons in a Neurod2 hypomorphic mouse carrying a patient-equivalent allele, rather than a null, and determine whether mis-lamination is present at the allele dosage that causes human disease.
What determines whether a NEUROD2 variant carrier develops epilepsy at all?
KNOWLEDGE GAP OPEN gap_seizures_are_not_obligatory
Attached to
pathophysiology#Seizures
The disorder is named and defined as an epileptic encephalopathy, but at least one individual with a de novo NEUROD2 missense variant has developmental delay and no seizures. That is not a minor phenotypic footnote: it means the seizures are a frequent consequence rather than a defining one, and it raises the question of what separates carriers who develop epilepsy from those who do not - allele severity, modifier genotype, or something environmental. The entry therefore curates developmental delay as the constant feature and seizures as a frequent but non-obligatory one. The seizure phenotype does carry a frequency band, FREQUENT, taken from the counted 3 of 7 assessed patients - but that number should be read as a ceiling rather than as a population estimate. The reported cohort is small, and it was ascertained through epilepsy: the disorder was named and first described from epileptic encephalopathy cases, so carriers without seizures are exactly the ones least likely to have been found. Ascertainment through the phenotype being counted inflates its apparent frequency, so 3 of 7 is an upper bound; a denominator assembled through non-epilepsy channels would almost certainly put the figure lower.
Proposed experiments
Seizure penetrance stratified by allele activity
exp_genotype_stratified_seizure_penetrance
Assay residual transcriptional activity for each reported NEUROD2 patient allele in a common reporter system, and test whether residual activity predicts the presence or absence of epilepsy across carriers. Ascertainment through non-epilepsy channels, such as developmental-delay cohorts, would be needed to avoid the bias that currently makes seizures look obligatory.
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Pathophysiology

7
De Novo NEUROD2 Variant
The initiating lesion. Patient variants reduce NEUROD2 activity rather than abolishing the protein - overexpression of the patient alleles was markedly less effective than wild type in a functional assay, which is what establishes them as hypomorphic rather than merely present.
Downstream
Reduced Proneural Transcription Factor Activity The variant acts on the transcription factor's own activity.
Show evidence (1 reference)
PMID:30323019 SUPPORT Model Organism
"Overexpression of wild-type NEUROD2 induced ectopic neurons in tadpoles; however, patient variants were markedly less effective, suggesting that both variants are dysfunctional and likely pathogenic"
A functional assay comparing patient alleles against wild type, which is what distinguishes a hypomorphic variant from an incidental one.
Reduced Proneural Transcription Factor Activity
Loss of NEUROD2 transcriptional activity during vertebrate brain development. This is the disorder's defining molecular state and the level at which it differs from most developmental and epileptic encephalopathies: the lesion is in a regulator of gene expression, so its consequences are distributed across every downstream program NEUROD2 controls rather than concentrated in one protein's function.
central nervous system neuron differentiation GO:0021953 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased central nervous system neuron differentiation (GO:0021953). GO:0021953 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Forebrain excitatory neuron-specific Neurod2 conditional knockout mouse Mouse perturbs Cell-type-restricted deletion isolating the contribution of forebrain excitatory neurons.
Downstream
Disrupted Cortical Neuron Migration and Lamination NEUROD2 regulates genes required for radial migration and layer specification.
Blood-Brain Barrier Permeability A separate, non-neuronal arm established in the tadpole model; the intervening steps between reduced NEUROD2 activity and barrier leakiness are not established.
Show evidence (1 reference)
PMID:38788202 SUPPORT Model Organism
"Our results support a model of DEE75 resulting from reduced NeuroD2 activity during vertebrate brain development"
States the reduced-activity model directly. Note the source labels the disorder DEE75; that designation belongs to a different disease and the discrepancy is addressed in this entry's notes and in a dedicated discussion.
Disrupted Cortical Neuron Migration and Lamination
NEUROD2 target genes include those required for radial migration and layer-specific differentiation of cortical projection neurons, so reduced activity mis-positions neurons rather than killing them. Notably the gross structure of the tadpole brain appeared normal despite the functional phenotype, so this is a wiring defect rather than a malformation visible at low magnification.
cortical glutamatergic projection neuron CL:0000679 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical glutamatergic projection neuron, annotated with glutamatergic neuron (CL:0000679). CL:0000679 is a cell type from the Cell Ontology.
cerebral cortex radially oriented cell migration GO:0021799 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal cerebral cortex radially oriented cell migration (GO:0021799). GO:0021799 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Animal models
Neurod2 knockout and heterozygous mouse Mouse recapitulates Cortical projection neurons over-migrate, shifting the final position and size of cortical layers, in both null and heterozygous animals.
Downstream
Neuronal Hyperactivity Mis-wired cortical circuitry is the proposed substrate for the hyperactivity, but no source establishes the intervening steps.
Neurodevelopmental Syndrome with Autistic Features The same mis-wiring is the proposed substrate for the core neurodevelopmental phenotype. This edge, not the seizure edge, carries the disorder's most frequent outcome - which is why the pathograph terminates in two places.
Show evidence (3 references)
PMID:34188164 SUPPORT Model Organism
"In Neurod2 KO embryos, cortical projection neurons over-migrated, thereby altering the final size and position of layers"
The direct migration measurement, in a layered mammalian cortex rather than the lissencephalic tadpole. Note the direction: neurons over-migrate rather than failing to migrate, so the defect is mis-positioning rather than arrest.
PMID:34188164 SUPPORT Model Organism
"spine density and turnover were dysregulated in apical but not basal compartments in layer 5 neurons"
Compartment-specific synaptic pathology - apical but not basal - which is a finer distinction than a general statement of altered connectivity and is preserved here rather than summarised away.
PMID:38788202 SUPPORT Model Organism
"While the resulting tadpole brain appeared grossly normal, the blood-brain barrier (BBB) was found to be leakier than that of controls"
Records that gross brain structure is preserved, which is what makes this a circuit-wiring rather than a malformation disorder, and simultaneously introduces the barrier arm.
Blood-Brain Barrier Permeability
A leaky blood-brain barrier in the CRISPR tadpole model. This is the entry's most unusual node: a non-neuronal contributor to epileptogenesis in a disorder whose gene is a neuronal transcription factor. It is curated as its own arm rather than as a consequence of the neuronal phenotype, because the losartan experiment acts on it directly and improves seizures.
endothelial cell CL:0000115 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves endothelial cell (CL:0000115). CL:0000115 is a cell type from the Cell Ontology.
Animal models
Xenopus laevis NeuroD2 CRISPR knockdown tadpole Xenopus laevis recapitulates Increased barrier permeability, rescued alongside seizures by losartan.
Downstream
Neuronal Hyperactivity Barrier leak is proposed to contribute to epileptogenesis, supported by the losartan rescue acting on both together.
Show evidence (2 references)
PMID:38788202 SUPPORT Model Organism
"the blood-brain barrier (BBB) was found to be leakier than that of controls"
The barrier measurement in the model.
PMID:38788202 SUPPORT Model Organism
"indicate that a leaky BBB contributes to epileptogenesis"
The authors' own claim that the barrier defect is causally involved rather than incidental.
Neuronal Hyperactivity
Calcium imaging in the tadpole model shows prolonged, strong signals sweeping through the brain. Curated at the level the source states it, as network-level hyperactivity measured by calcium signal rather than as single-neuron excitability, which was not measured here.
Animal models
Neurod2 knockout and heterozygous mouse Mouse recapitulates Increased intrinsic excitability in layer 5 cortical projection neurons.
Xenopus laevis NeuroD2 CRISPR knockdown tadpole Xenopus laevis recapitulates Calcium imaging shows prolonged signals sweeping through the brain.
Downstream
Seizures Network hyperactivity manifests as seizure activity.
Show evidence (3 references)
PMID:38788202 SUPPORT Model Organism
"Live imaging of Ca2+ signaling revealed prolongued, strong signals sweeping through the brain, indicative of neuronal hyperactivity"
The imaging measurement and the interpretation the authors draw from it. The source's spelling of "prolongued" is reproduced as published.
PMID:34188164 SUPPORT Model Organism
"Patch-clamp recordings in layer 5 neurons of juvenile mice revealed increased intrinsic excitability"
Independent, cell-resolved confirmation of increased excitability in a mammalian model, complementing the network-level calcium signal from the tadpole. The two measurements are at different scales and in different species, which is why both are curated rather than one standing for the other.
PMID:34188164 SUPPORT Model Organism
"Bulk RNA sequencing showed dysregulated expression of many genes associated with neuronal excitability and synaptic function"
Establishes the transcriptional route from the transcription factor lesion to the excitability phenotype, which is the mechanistically expected path for this gene class.
Neurodevelopmental Syndrome with Autistic Features
The core clinical outcome: autistic features, intellectual disability and speech disturbance. This node exists because the phenotype data put it here - epilepsy is present in 3 of 7 assessed patients and is explicitly non-fully-penetrant, while these three features are the ones the cohort paper calls core. A pathograph terminating only in seizures would state the disorder backwards. The attribution is unusually well grounded for a neurodevelopmental phenotype: a conditional deletion restricted to forebrain excitatory neurons reproduces the ASD-like phenotype, so the defect is cell-autonomous to glutamatergic neurons rather than a secondary consequence of network dysfunction elsewhere.
cortical glutamatergic projection neuron CL:0000679 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical glutamatergic projection neuron, annotated with glutamatergic neuron (CL:0000679). CL:0000679 is a cell type from the Cell Ontology.
Show evidence (2 references)
PMID:34188164 SUPPORT Human Clinical
"our data point to a core NEUROD2-associated phenotype centered on ASD, intellectual disability, and speech disturbance"
The core human phenotype this node represents.
PMID:34188164 SUPPORT Model Organism
"These features overlap with those uncovered in the mouse studies, demonstrating the necessity of NEUROD2 for normal brain development and revealing the region-specific contributions of dysfunctional NEUROD2 to intellectual disability, ASD, hyperactivity, and social-behavioral deficits"
Links the human phenotype to the mouse work and to the region-specific attribution that the conditional knockout established.
Seizures
Early-onset refractory seizures, characteristically including epileptic spasms. Crucially seizures are not obligatory: the phenotype now includes developmental delay without epilepsy, so the disorder should not be defined by its seizures alone.
Animal models
Neurod2 knockout and heterozygous mouse Mouse partially recapitulates Occasional spontaneous seizures alongside the ASD-like behavioural phenotype.
Show evidence (1 reference)
PMID:30323019 SUPPORT Model Organism
"Depleting neurod2 with CRISPR/Cas9-mediated genome editing induced spontaneous seizures in tadpoles, mimicking the patients' condition"
Establishes that depleting the gene reproduces spontaneous seizures, linking the molecular lesion to the clinical endpoint in a model.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for NEUROD2-Related Developmental and Epileptic Encephalopathy 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

8
Nervous System 7
Autistic Behavior VERY_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:34188164 SUPPORT Human Clinical
"our data point to a core NEUROD2-associated phenotype centered on ASD, intellectual disability, and speech disturbance"
Names ASD as one of three core features. The source characterizes the core phenotype as such against explicitly "non-fully penetrant" features it counts separately, so VERY_FREQUENT rather than OBLIGATE is the defensible band - no per-patient count is given for the core features themselves.
PMID:34188164 SUPPORT Human Clinical
"we identified eleven patients from eight families with a neurodevelopmental disorder including intellectual disability and ASD associated with NEUROD2 pathogenic mutations"
The cohort in which the core phenotype was established.
Intellectual Disability VERY_FREQUENT 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:34188164 SUPPORT Human Clinical
"a core NEUROD2-associated phenotype centered on ASD, intellectual disability, and speech disturbance"
Names intellectual disability as core. Banded VERY_FREQUENT for the same reason as the ASD entry: core but without a stated per-patient count.
Delayed Speech and Language Development VERY_FREQUENT HP:0000750 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Delayed speech and language development (HP:0000750). HP:0000750 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:34188164 SUPPORT Human Clinical
"core NEUROD2-associated phenotype centered on ASD, intellectual disability, and speech disturbance"
Names speech disturbance as the third core feature.
PMID:34188164 SUPPORT Human Clinical
"we searched for and identified five families with pathogenic NEUROD2 mutations associated with intellectual disability, ASD, hyperactivity, and speech delay, with or without epilepsy"
The same feature named as speech delay, and - in the trailing clause - the direct statement that epilepsy is optional in this disorder.
Attention Deficit Hyperactivity Disorder FREQUENT HP:0007018 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Attention deficit hyperactivity disorder (HP:0007018). HP:0007018 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34188164 SUPPORT Human Clinical
"Non-fully penetrant NEUROD2-associated phenotypes include ADHD symptoms (5/7 patients) and epilepsy (3/7 patients)"
5/7 is 71 percent, in the FREQUENT band (30-79 percent), counted directly by the source.
Early-Onset Seizures FREQUENT 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 (2 references)
PMID:30323019 SUPPORT Human Clinical
"novel de novo variants in neuronal differentiation factor 2 (NEUROD2) in two unrelated children with early infantile epileptic encephalopathy"
Establishes early infantile epileptic encephalopathy as the founding phenotype.
PMID:34188164 SUPPORT Human Clinical
"Non-fully penetrant NEUROD2-associated phenotypes include ADHD symptoms (5/7 patients) and epilepsy (3/7 patients)"
Curated PARTIAL because it qualifies rather than simply supports the seizure phenotype: 3/7 is 43 percent, in the FREQUENT band, and the source classes epilepsy as non-fully-penetrant. This is the count behind the frequency band, and behind the seizures-are-not-obligatory discussion below.
Epileptic Spasms HP:0011097 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Epileptic spasm (HP:0011097). HP:0011097 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:36494631 SUPPORT Human Clinical
"We report a female patient of Southeast Asian ethnicity with global developmental delay and epileptic spasms commencing in the first few months of life"
Documents epileptic spasms with onset in the first months in a genotype-confirmed patient.
Global Developmental Delay VERY_FREQUENT 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.
Show evidence (2 references)
PMID:33438828 SUPPORT Human Clinical
"Here, we report an adolescent with developmental delay without seizures who was found to have a novel de novo heterozygous NEUROD2 missense variant"
Documents developmental delay in the absence of seizures, which is what establishes the delay rather than the epilepsy as the constant feature. It also fixes the frequency band: developmental impairment is present even in the carrier who has no epilepsy, so it is at least as frequent as any counted feature here. VERY_FREQUENT rather than OBLIGATE because no source states a per-patient count for it - the same qualitative-anchor reasoning applied to the three core features above.
PMID:33438828 SUPPORT Human Clinical
"Her characteristics are notable primarily for global development delay without the early-onset epileptic encephalopathy of the previously observed phenotype"
States the contrast with the founding phenotype explicitly.
Other 1
Drug-Resistant Epilepsy Refractory drug response HP:0020174 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Refractory drug response (HP:0020174). HP:0020174 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33438828 SUPPORT Human Clinical
"Both patients were non-responsive to multiple antiepileptic medications, one becoming seizure-free with a ketogenic diet, the other with a vagal nerve stimulator"
Documents non-response to multiple drugs, and simultaneously records that two non-drug approaches each achieved seizure freedom - which is why this entry does not describe the epilepsy as untreatable.
🧬

Genetic Associations

1
NEUROD2 (Heterozygous de novo variants in NEUROD2 reduce the activity of the encoded transcription factor and cause DEE72. Reported pathogenic variants cluster in the bHLH domain, the DNA-binding module: p.Glu130Gln, p.Met134Thr and p.Arg129Trp all fall in the conserved DNA-binding basic region of the first helix, and p.Leu163Pro lies in the second helix, also DNA-binding and also highly conserved. p.Glu130Gln is recurrent across unrelated families. In cellular assay the variants are hypomorphic rather than null - markedly less effective than wild type in a neuron-induction assay, but not inert.)
Gene: NEUROD2 hgnc:7763 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is NEUROD2 (hgnc:7763). hgnc:7763 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (4 references)
PMID:30323019 SUPPORT Human Clinical
"We identified novel de novo variants in neuronal differentiation factor 2 (NEUROD2) in two unrelated children with early infantile epileptic encephalopathy"
The gene-disease assertion from the founding study.
PMID:34188164 SUPPORT Human Clinical
"De novo mutations Glu130Gln, Met134Thr, and Arg129Trp from Families 1, 2, and 4 are found in the conserved DNA-binding region of the bHLH domain, which is the basic region of the first helix"
Locates three of the reported variants in the bHLH DNA-binding basic region, and names Glu130Gln as arising independently in more than one family.
PMID:34188164 SUPPORT Human Clinical
"The de novo Leu163Pro mutation from Family 3 lies in the second helix of the bHLH domain thought to be important for DNA binding and is also highly conserved"
Places the fourth variant in the same functional module, which is what makes the bHLH clustering a spectrum-level observation rather than a coincidence of two variants.
+ 1 more reference
💊

Medical Actions

3
Combined Vigabatrin and High-Dose Prednisolone
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: vigabatrin CHEBI:63638 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses vigabatrin (CHEBI:63638). CHEBI:63638 is a therapeutic agent from Chemical Entities of Biological Interest. prednisolone CHEBI:8378 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses prednisolone (CHEBI:8378). CHEBI:8378 is a therapeutic agent from Chemical Entities of Biological Interest.
The one treatment in this entry with a documented positive response. A genotype-confirmed patient with epileptic spasms responded to combined vigabatrin and high-dose prednisolone, with marked EEG improvement. This is a single case, so it establishes that the standard spasms regimen can work in this genotype - not a response rate.
Show evidence (2 references)
PMID:36494631 SUPPORT Human Clinical
"Electroencephalogram before treatment showed multifocal independent spikes predominantly in both posterior head regions and demonstrated marked improvement following combined vigabatrin and high-dose prednisolone treatment"
The measured response to the combination, reported as an objective EEG change rather than as a clinical impression. Preferred over the paper's title, which states the same result less precisely.
PMID:36494631 SUPPORT Human Clinical
"there are limited data about the treatment course of ES with combined vigabatrin and high-dose prednisolone in the NEUROD2-related NDD syndrome"
The authors' own statement of how thin the evidence base is, which is why this entry curates the response as a single documented case rather than as an expected outcome.
Ketogenic Diet
Action: Dietary InterventionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Dietary Intervention (NCIT:C15447). NCIT:C15447 is a clinical intervention from the NCI Thesaurus. NCIT:C15447
One reported patient became seizure-free on a ketogenic diet after failing multiple antiseizure medications.
Show evidence (1 reference)
PMID:33438828 SUPPORT Human Clinical
"Both patients were non-responsive to multiple antiepileptic medications, one becoming seizure-free with a ketogenic diet, the other with a vagal nerve stimulator"
Documents seizure freedom on a ketogenic diet in a drug-refractory patient.
Vagus Nerve Stimulation
A second drug-refractory patient became seizure-free with a vagal nerve stimulator.
Show evidence (1 reference)
PMID:33438828 SUPPORT Human Clinical
"one becoming seizure-free with a ketogenic diet, the other with a vagal nerve stimulator"
Documents seizure freedom with vagus nerve stimulation in the second refractory patient.
🔬

Diagnosis

2
Electroencephalography
EEG in the spasms presentation shows multifocal independent spikes, and improves markedly with effective treatment - making it useful for following response as well as for diagnosis.
Electroencephalography NCIT:C38054 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:36494631 SUPPORT Human Clinical
"Electroencephalogram before treatment showed multifocal independent spikes predominantly in both posterior head regions and demonstrated marked improvement following combined vigabatrin and high-dose prednisolone treatment"
Records both the characteristic interictal pattern and its response to treatment.
Whole Exome Sequencing
The gene was identified by exome sequencing and diagnosis remains genotype-driven.
Whole Exome Sequencing NCIT:C101295 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:30323019 SUPPORT Human Clinical
"We used whole exome sequencing to identify candidate genes"
Establishes the diagnostic route by which the gene-disease relationship was found.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
Eleven patients from eight families in the defining 2021 cohort, which subsumed the five families identified in the same work; two further children were reported in the 2018 founding study. No population prevalence estimate exists.
Show evidence (1 reference)
PMID:34188164 SUPPORT Human Clinical
"we identified eleven patients from eight families with a neurodevelopmental disorder including intellectual disability and ASD associated with NEUROD2 pathogenic mutations"
The largest reported case count, which is the only occurrence measure available.
🐁

Animal Models

3
Neurod2 knockout and heterozygous mouse
The best-matched model for the lamination arm of this disorder, and the one that supplies the dosage evidence. Both null and heterozygous animals were characterized, in a mammalian six-layered neocortex that forms inside-out by radial migration - the architecture the Xenopus model cannot provide. The heterozygote matters specifically: patients are heterozygous, so the HET arm is the genotype-matched one.
Species
Mouse
Genotype
Neurod2 constitutive knockout (KO) and heterozygote (HET)
Publication
PMID:34188164
Pathograph links
Disrupted Cortical Neuron Migration and Lamination recapitulates fidelity: high Cortical projection neurons over-migrate, shifting the final position and size of cortical layers, in both null and heterozygous animals.
Limitations: Mouse and human neocortical development differ in scale, in the extent of the outer subventricular zone and in gyrification, so the magnitude of a migration defect does not transfer quantitatively. The mouse also carries a null or heterozygous-null allele rather than the patients' hypomorphic missense alleles, so it models the dosage consequence rather than the specific allele.
Readouts
Radial position of cortical projection neurons
Direction: ALTERED
Interpretation: Neurons over-migrate rather than under-migrate - they end up too superficial, and the layers are correspondingly displaced. The direction is worth stating because the intuitive prediction for a migration defect is the opposite one.
Show evidence (1 reference)
PMID:34188164 SUPPORT Model Organism
"In Neurod2 KO embryos, cortical projection neurons over-migrated, thereby altering the final size and position of layers"
The migration measurement behind this readout.
Over-migration in heterozygotes
Direction: ALTERED
Interpretation: The same defect in the genotype-matched heterozygote, which is what makes the model's relevance to a dominant human disorder more than an inference from the null.
Show evidence (1 reference)
PMID:34188164 SUPPORT Model Organism
"Mice heterozygous for Neurod2 had similar defects, indicating that Neurod2 is haploinsufficient"
Establishes that one functional copy is insufficient, in the same assay.
Show evidence (1 reference)
PMID:34188164 SUPPORT Model Organism
"Over-migration was maintained post-migration, at P7"
The defect persists past the migratory period rather than being a transient delay, which is what makes it informative for the lamination node rather than only for migration timing.
Neuronal Hyperactivity recapitulates fidelity: high Increased intrinsic excitability in layer 5 cortical projection neurons.
Limitations: Recorded in layer 5 neurons of juvenile mice; the measurement is cell-intrinsic excitability and does not by itself establish network-level hypersynchrony.
Readouts
Intrinsic excitability of layer 5 neurons
Direction: INCREASED
Interpretation: Patch-clamp recordings show increased intrinsic excitability, the cell-autonomous correlate of the hyperactivity node.
Show evidence (1 reference)
PMID:34188164 SUPPORT Model Organism
"Patch-clamp recordings in layer 5 neurons of juvenile mice revealed increased intrinsic excitability"
The electrophysiological measurement behind this readout.
Show evidence (1 reference)
PMID:34188164 SUPPORT Model Organism
"In juvenile and adults, spine density and turnover were dysregulated in apical but not basal compartments in layer 5 neurons"
The structural synaptic correlate in the same cells. The compartment specificity - apical but not basal - is preserved rather than generalized to "synaptic defects".
Seizures partially recapitulates fidelity: moderate Occasional spontaneous seizures alongside the ASD-like behavioural phenotype.
Limitations: Spontaneous seizures were seen only occasionally in the null, and the source gives no count, frequency or EEG characterization. This is a behavioural observation reported in passing among the ASD-like phenotypes, not a quantified epilepsy phenotype, and it is not reported for the genotype-matched heterozygote at all.
Readouts
Spontaneous seizure occurrence
Direction: INCREASED
Interpretation: Present but occasional. The hedge is the source's own and is preserved rather than upgraded to a seizure phenotype.
Show evidence (1 reference)
PMID:34188164 SUPPORT Model Organism
"Neurod2 KO mice displayed social interaction deficits, stereotypies, hyperactivity, and occasionally spontaneous seizures"
Curated PARTIAL: the word "occasionally" is doing real work and no count is given. The same sentence is the primary evidence for the ASD-like behavioural phenotype, which is much better characterized in this model than the seizures are.
Show evidence (1 reference)
PMID:34188164 SUPPORT Model Organism
"social interaction deficits, stereotypies, hyperactivity, and occasionally spontaneous seizures"
Curated PARTIAL for the seizure node specifically. The behavioural triad is well supported; the seizure observation is not quantified.
Forebrain excitatory neuron-specific Neurod2 conditional knockout mouse
A conditional deletion restricted to forebrain excitatory neurons. Its purpose is causal attribution rather than phenotype reproduction: it tests whether the behavioural phenotype arises from within glutamatergic neurons or from elsewhere in the brain, which the constitutive knockout cannot distinguish.
Species
Mouse
Genotype
Emx1-IRES-Cre; Neurod2 flox/flox (cKO)
Publication
PMID:34188164
Pathograph links
Reduced Proneural Transcription Factor Activity perturbs fidelity: high Cell-type-restricted deletion isolating the contribution of forebrain excitatory neurons.
Limitations: Emx1-Cre deletes across forebrain excitatory neurons broadly and from early development, so it localizes the requirement to that population without resolving which region, layer or developmental window within it is responsible.
Show evidence (1 reference)
PMID:34188164 SUPPORT Model Organism
"We generated Neurod2flox/flox mice and crossed them with Emx1IRESCre mice to assess the specific contribution of forebrain excitatory neurons to the ASD-related phenotypes"
States the design and its purpose - attributing the phenotype to a cell type rather than reproducing it.
This model is the basis for the cell-autonomy claim in the source's own title. It is curated as PERTURBS rather than RECAPITULATES because what it contributes is the localization of the requirement, not a demonstration that the human phenotype is reproduced - the constitutive knockout above does that.
Xenopus laevis NeuroD2 CRISPR knockdown tadpole
A CRISPR knockdown tadpole that reproduces seizure behaviour and network hyperactivity, and that produced the entry's most unexpected finding - a leaky blood-brain barrier - together with a pharmacological rescue acting on it.
Species
Xenopus laevis
Genotype
NeuroD2.S CRISPR/Cas9 edited
Publication
PMID:38788202
Pathograph links
Neuronal Hyperactivity recapitulates fidelity: moderate Calcium imaging shows prolonged signals sweeping through the brain.
Limitations: The Xenopus forebrain is lissencephalic, unlayered, and forms outside-in, whereas the human neocortex is six-layered and forms inside-out via radial migration. Since the proposed human mechanism runs through disrupted radial migration and lamination, the model cannot test the step it is being used to support, and higher cognitive phenotypes cannot be assessed at all.
Readouts
Brain-wide calcium signal
Direction: INCREASED
Interpretation: Prolonged, strong signals sweeping through the brain.
Show evidence (1 reference)
PMID:38788202 SUPPORT Model Organism
"Live imaging of Ca2+ signaling revealed prolongued, strong signals sweeping through the brain, indicative of neuronal hyperactivity"
The imaging measurement behind this readout.
Show evidence (1 reference)
PMID:38788202 SUPPORT Model Organism
"NeuroD2.S CRISPR/Cas9 edited tadpoles were more active, swam faster on average, and had more seizures"
Establishes the behavioural seizure phenotype that makes the model informative.
Blood-Brain Barrier Permeability recapitulates fidelity: low Increased barrier permeability, rescued alongside seizures by losartan.
Limitations: The barrier phenotype has been demonstrated only in tadpoles. No human data establish that blood-brain barrier permeability is altered in NEUROD2 patients, so this arm rests entirely on the model - which is why it carries a HUMAN_MODEL_MISMATCH discussion rather than being presented as an established part of the human disease.
Readouts
Blood-brain barrier permeability
Direction: INCREASED
Interpretation: The barrier is leakier than in sibling controls.
Show evidence (1 reference)
PMID:38788202 SUPPORT Model Organism
"the blood-brain barrier (BBB) was found to be leakier than that of controls"
The permeability measurement behind this readout.
Seizure events under losartan
Direction: DECREASED
Interpretation: A TGF-beta antagonist that acts on the barrier reduced seizure events more than four-fold, which is the experiment linking the barrier arm to the seizures.
Show evidence (1 reference)
PMID:38788202 SUPPORT Model Organism
"Treatment of NeuroD2 CRISPant tadpoles with 5 mM Losartan decreased seizure events by more than 4-fold compared to the baseline"
The rescue measurement behind this readout.
Show evidence (1 reference)
PMID:38788202 SUPPORT Model Organism
"Losartan was shown to have a short-term protective effect, reducing neuronal hyperactivity and reducing permeability of the BBB"
Supports treating the barrier as a mechanistically involved arm rather than an incidental finding, since acting on it improves the neuronal phenotype. The word "short-term" is retained because durability was not established.
{ }

Source YAML

click to show 
name: NEUROD2-Related Developmental and Epileptic Encephalopathy
creation_date: "2026-08-20T06:45:00Z"
category: Mendelian
synonyms:
- Developmental and epileptic encephalopathy 72
- DEE72
- EIEE72
- NEUROD2-related neurodevelopmental disorder
description: >-
  NEUROD2-related developmental and epileptic encephalopathy (DEE72) is caused by
  heterozygous de novo variants in NEUROD2, a class II basic helix-loop-helix proneural
  transcription factor that dimerises with E-proteins to bind E-box elements in the
  promoters of neuronal differentiation genes. It is unusual among the developmental and
  epileptic encephalopathies in that the primary lesion is transcriptional rather than in
  a channel, synaptic protein or trafficking component, so the disorder arises from
  mis-specified cortical development rather than from a directly altered conductance. The
  phenotype has since broadened well past the epileptic encephalopathy it was named for: the
  core of the disorder is a neurodevelopmental syndrome centred on autistic features,
  intellectual disability and speech disturbance, of which epilepsy is one non-fully-penetrant
  branch - present in 3 of 7 assessed patients in the defining cohort, and absent altogether
  in at least one reported carrier with developmental delay.
disease_term:
  preferred_term: developmental and epileptic encephalopathy, 72
  term:
    id: MONDO:0032710
    label: developmental and epileptic encephalopathy, 72
parents:
- Epilepsy
- Neurological Disease
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    Heterozygous and de novo.
  evidence:
  - reference: PMID:30323019
    reference_title: "De novo pathogenic variants in neuronal differentiation factor 2 (NEUROD2) cause a form of early infantile epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified novel de novo variants in neuronal differentiation factor 2
      (NEUROD2) in two unrelated children with early infantile epileptic encephalopathy"
    explanation: >-
      Establishes the de novo heterozygous architecture in the founding pair of patients.

pathophysiology:

- name: De Novo NEUROD2 Variant
  biological_scale: MOLECULAR
  description: >-
    The initiating lesion. Patient variants reduce NEUROD2 activity rather than abolishing
    the protein - overexpression of the patient alleles was markedly less effective than
    wild type in a functional assay, which is what establishes them as hypomorphic rather
    than merely present.
  evidence:
  - reference: PMID:30323019
    reference_title: "De novo pathogenic variants in neuronal differentiation factor 2 (NEUROD2) cause a form of early infantile epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Overexpression of wild-type NEUROD2 induced ectopic neurons in tadpoles;
      however, patient variants were markedly less effective, suggesting that both variants
      are dysfunctional and likely pathogenic"
    explanation: >-
      A functional assay comparing patient alleles against wild type, which is what
      distinguishes a hypomorphic variant from an incidental one.
  downstream:
  - target: Reduced Proneural Transcription Factor Activity
    causal_link_type: DIRECT
    description: >-
      The variant acts on the transcription factor's own activity.

- name: Reduced Proneural Transcription Factor Activity
  biological_scale: MOLECULAR
  description: >-
    Loss of NEUROD2 transcriptional activity during vertebrate brain development. This is
    the disorder's defining molecular state and the level at which it differs from most
    developmental and epileptic encephalopathies: the lesion is in a regulator of gene
    expression, so its consequences are distributed across every downstream program
    NEUROD2 controls rather than concentrated in one protein's function.
  biological_processes:
  - preferred_term: central nervous system neuron differentiation
    modifier: DECREASED
    term:
      id: GO:0021953
      label: central nervous system neuron differentiation
  evidence:
  - reference: PMID:38788202
    reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our results support a model of DEE75 resulting from reduced NeuroD2 activity
      during vertebrate brain development"
    explanation: >-
      States the reduced-activity model directly. Note the source labels the disorder
      DEE75; that designation belongs to a different disease and the discrepancy is
      addressed in this entry's notes and in a dedicated discussion.
  downstream:
  - target: Disrupted Cortical Neuron Migration and Lamination
    causal_link_type: DIRECT
    description: >-
      NEUROD2 regulates genes required for radial migration and layer specification.
  - target: Blood-Brain Barrier Permeability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      A separate, non-neuronal arm established in the tadpole model; the intervening steps
      between reduced NEUROD2 activity and barrier leakiness are not established.

- name: Disrupted Cortical Neuron Migration and Lamination
  biological_scale: TISSUE
  description: >-
    NEUROD2 target genes include those required for radial migration and layer-specific
    differentiation of cortical projection neurons, so reduced activity mis-positions
    neurons rather than killing them. Notably the gross structure of the tadpole brain
    appeared normal despite the functional phenotype, so this is a wiring defect rather
    than a malformation visible at low magnification.
  biological_processes:
  - preferred_term: cerebral cortex radially oriented cell migration
    modifier: ABNORMAL
    term:
      id: GO:0021799
      label: cerebral cortex radially oriented cell migration
  cell_types:
  - preferred_term: cortical glutamatergic projection neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  evidence:
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In Neurod2 KO embryos, cortical projection neurons over-migrated, thereby
      altering the final size and position of layers"
    explanation: >-
      The direct migration measurement, in a layered mammalian cortex rather than the
      lissencephalic tadpole. Note the direction: neurons over-migrate rather than failing
      to migrate, so the defect is mis-positioning rather than arrest.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "spine density and turnover were dysregulated in apical but not basal
      compartments in layer 5 neurons"
    explanation: >-
      Compartment-specific synaptic pathology - apical but not basal - which is a finer
      distinction than a general statement of altered connectivity and is preserved here
      rather than summarised away.
  - reference: PMID:38788202
    reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "While the resulting tadpole brain appeared grossly normal, the blood-brain
      barrier (BBB) was found to be leakier than that of controls"
    explanation: >-
      Records that gross brain structure is preserved, which is what makes this a
      circuit-wiring rather than a malformation disorder, and simultaneously introduces the
      barrier arm.
  downstream:
  - target: Neuronal Hyperactivity
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Mis-wired cortical circuitry is the proposed substrate for the hyperactivity, but no
      source establishes the intervening steps.
  - target: Neurodevelopmental Syndrome with Autistic Features
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The same mis-wiring is the proposed substrate for the core neurodevelopmental
      phenotype. This edge, not the seizure edge, carries the disorder's most frequent
      outcome - which is why the pathograph terminates in two places.

- name: Blood-Brain Barrier Permeability
  biological_scale: TISSUE
  description: >-
    A leaky blood-brain barrier in the CRISPR tadpole model. This is the entry's most
    unusual node: a non-neuronal contributor to epileptogenesis in a disorder whose gene is
    a neuronal transcription factor. It is curated as its own arm rather than as a
    consequence of the neuronal phenotype, because the losartan experiment acts on it
    directly and improves seizures.
  cell_types:
  - preferred_term: endothelial cell
    term:
      id: CL:0000115
      label: endothelial cell
  evidence:
  - reference: PMID:38788202
    reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "the blood-brain barrier (BBB) was found to be leakier than that of controls"
    explanation: >-
      The barrier measurement in the model.
  - reference: PMID:38788202
    reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "indicate that a leaky BBB contributes to epileptogenesis"
    explanation: >-
      The authors' own claim that the barrier defect is causally involved rather than
      incidental.
  downstream:
  - target: Neuronal Hyperactivity
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Barrier leak is proposed to contribute to epileptogenesis, supported by the losartan
      rescue acting on both together.

- name: Neuronal Hyperactivity
  biological_scale: CELLULAR
  description: >-
    Calcium imaging in the tadpole model shows prolonged, strong signals sweeping through
    the brain. Curated at the level the source states it, as network-level hyperactivity
    measured by calcium signal rather than as single-neuron excitability, which was not
    measured here.
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Neuronal Hyperexcitability and Hypersynchrony"
  evidence:
  - reference: PMID:38788202
    reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Live imaging of Ca2+ signaling revealed prolongued, strong signals sweeping
      through the brain, indicative of neuronal hyperactivity"
    explanation: >-
      The imaging measurement and the interpretation the authors draw from it. The
      source's spelling of "prolongued" is reproduced as published.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Patch-clamp recordings in layer 5 neurons of juvenile mice revealed increased
      intrinsic excitability"
    explanation: >-
      Independent, cell-resolved confirmation of increased excitability in a mammalian
      model, complementing the network-level calcium signal from the tadpole. The two
      measurements are at different scales and in different species, which is why both are
      curated rather than one standing for the other.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Bulk RNA sequencing showed dysregulated expression of many genes associated
      with neuronal excitability and synaptic function"
    explanation: >-
      Establishes the transcriptional route from the transcription factor lesion to the
      excitability phenotype, which is the mechanistically expected path for this gene
      class.
  downstream:
  - target: Seizures
    causal_link_type: DIRECT
    description: >-
      Network hyperactivity manifests as seizure activity.

- name: Neurodevelopmental Syndrome with Autistic Features
  biological_scale: ORGANISM
  description: >-
    The core clinical outcome: autistic features, intellectual disability and speech
    disturbance. This node exists because the phenotype data put it here - epilepsy is
    present in 3 of 7 assessed patients and is explicitly non-fully-penetrant, while these
    three features are the ones the cohort paper calls core. A pathograph terminating only
    in seizures would state the disorder backwards.
    The attribution is unusually well grounded for a neurodevelopmental phenotype: a
    conditional deletion restricted to forebrain excitatory neurons reproduces the ASD-like
    phenotype, so the defect is cell-autonomous to glutamatergic neurons rather than a
    secondary consequence of network dysfunction elsewhere.
  cell_types:
  - preferred_term: cortical glutamatergic projection neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  evidence:
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "our data point to a core NEUROD2-associated phenotype centered on ASD,
      intellectual disability, and speech disturbance"
    explanation: >-
      The core human phenotype this node represents.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These features overlap with those uncovered in the mouse studies,
      demonstrating the necessity of NEUROD2 for normal brain development and revealing the
      region-specific contributions of dysfunctional NEUROD2 to intellectual disability,
      ASD, hyperactivity, and social-behavioral deficits"
    explanation: >-
      Links the human phenotype to the mouse work and to the region-specific attribution
      that the conditional knockout established.

- name: Seizures
  biological_scale: ORGANISM
  description: >-
    Early-onset refractory seizures, characteristically including epileptic spasms. Crucially
    seizures are not obligatory: the phenotype now includes developmental delay without
    epilepsy, so the disorder should not be defined by its seizures alone.
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Recurrent Unprovoked Seizures"
  evidence:
  - reference: PMID:30323019
    reference_title: "De novo pathogenic variants in neuronal differentiation factor 2 (NEUROD2) cause a form of early infantile epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Depleting neurod2 with CRISPR/Cas9-mediated genome editing induced
      spontaneous seizures in tadpoles, mimicking the patients' condition"
    explanation: >-
      Establishes that depleting the gene reproduces spontaneous seizures, linking the
      molecular lesion to the clinical endpoint in a model.

phenotypes:

- category: Neurological
  name: Autistic Behavior
  description: >-
    Part of the core NEUROD2-associated phenotype, and the feature that led to the human
    cohort being sought in the first place: the mouse mutants were characterized as
    ASD-like before patients were identified. Curated above the epilepsy phenotypes rather
    than below them because the cohort data put it there.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Autistic behavior
    term:
      id: HP:0000729
      label: Autistic behavior
  evidence:
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "our data point to a core NEUROD2-associated phenotype centered on ASD,
      intellectual disability, and speech disturbance"
    explanation: >-
      Names ASD as one of three core features. The source characterizes the core phenotype
      as such against explicitly "non-fully penetrant" features it counts separately, so
      VERY_FREQUENT rather than OBLIGATE is the defensible band - no per-patient count is
      given for the core features themselves.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identified eleven patients from eight families with a neurodevelopmental
      disorder including intellectual disability and ASD associated with NEUROD2 pathogenic
      mutations"
    explanation: >-
      The cohort in which the core phenotype was established.

- category: Neurological
  name: Intellectual Disability
  description: >-
    The second of the three core features.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a core NEUROD2-associated phenotype centered on ASD, intellectual disability,
      and speech disturbance"
    explanation: >-
      Names intellectual disability as core. Banded VERY_FREQUENT for the same reason as
      the ASD entry: core but without a stated per-patient count.

- category: Neurological
  name: Delayed Speech and Language Development
  description: >-
    The third core feature. Described as speech disturbance in the cohort paper and as
    speech delay in the same paper's discussion of the five founding families.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "core NEUROD2-associated phenotype centered on ASD, intellectual disability,
      and speech disturbance"
    explanation: >-
      Names speech disturbance as the third core feature.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we searched for and identified five families with pathogenic NEUROD2
      mutations associated with intellectual disability, ASD, hyperactivity, and speech
      delay, with or without epilepsy"
    explanation: >-
      The same feature named as speech delay, and - in the trailing clause - the direct
      statement that epilepsy is optional in this disorder.

- category: Neurological
  name: Attention Deficit Hyperactivity Disorder
  description: >-
    Explicitly a non-fully-penetrant feature, in 5 of 7 assessed patients.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Attention deficit hyperactivity disorder
    term:
      id: HP:0007018
      label: Attention deficit hyperactivity disorder
  evidence:
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Non-fully penetrant NEUROD2-associated phenotypes include ADHD symptoms (5/7
      patients) and epilepsy (3/7 patients)"
    explanation: >-
      5/7 is 71 percent, in the FREQUENT band (30-79 percent), counted directly by the
      source.

- category: Neurological
  name: Early-Onset Seizures
  description: >-
    Seizures typically begin in the first months of life, often as epileptic spasms. They
    are not, however, an obligate feature: in the eleven-patient cohort epilepsy was present
    in 3 of 7 assessed patients and is explicitly classed as non-fully-penetrant, while ASD,
    intellectual disability and speech disturbance are the core features. The disorder's DEE
    name reflects how it was first found, not how often it seizes.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:30323019
    reference_title: "De novo pathogenic variants in neuronal differentiation factor 2 (NEUROD2) cause a form of early infantile epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "novel de novo variants in neuronal differentiation factor 2 (NEUROD2) in two
      unrelated children with early infantile epileptic encephalopathy"
    explanation: >-
      Establishes early infantile epileptic encephalopathy as the founding phenotype.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Non-fully penetrant NEUROD2-associated phenotypes include ADHD symptoms (5/7
      patients) and epilepsy (3/7 patients)"
    explanation: >-
      Curated PARTIAL because it qualifies rather than simply supports the seizure
      phenotype: 3/7 is 43 percent, in the FREQUENT band, and the source classes epilepsy
      as non-fully-penetrant. This is the count behind the frequency band, and behind the
      seizures-are-not-obligatory discussion below.

- category: Neurological
  name: Epileptic Spasms
  description: >-
    Epileptic spasms beginning in the first months of life, with multifocal independent
    spikes on EEG.
  phenotype_term:
    preferred_term: Epileptic spasm
    term:
      id: HP:0011097
      label: Epileptic spasm
  evidence:
  - reference: PMID:36494631
    reference_title: "Epileptic spasms related to neuronal differentiation factor 2 (NEUROD2) mutation respond to combined vigabatrin and high dose prednisolone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report a female patient of Southeast Asian ethnicity with global
      developmental delay and epileptic spasms commencing in the first few months of life"
    explanation: >-
      Documents epileptic spasms with onset in the first months in a genotype-confirmed
      patient.

- category: Neurological
  name: Global Developmental Delay
  description: >-
    Developmental impairment is the one feature present across the whole reported spectrum,
    including in the individual reported without epilepsy. That makes it, rather than the
    seizures, the phenotype the disorder is most reliably defined by.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:33438828
    reference_title: "Expansion of NEUROD2 phenotypes to include developmental delay without seizures."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report an adolescent with developmental delay without seizures who
      was found to have a novel de novo heterozygous NEUROD2 missense variant"
    explanation: >-
      Documents developmental delay in the absence of seizures, which is what establishes
      the delay rather than the epilepsy as the constant feature. It also fixes the
      frequency band: developmental impairment is present even in the carrier who has no
      epilepsy, so it is at least as frequent as any counted feature here. VERY_FREQUENT
      rather than OBLIGATE because no source states a per-patient count for it - the same
      qualitative-anchor reasoning applied to the three core features above.
  - reference: PMID:33438828
    reference_title: "Expansion of NEUROD2 phenotypes to include developmental delay without seizures."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Her characteristics are notable primarily for global development delay
      without the early-onset epileptic encephalopathy of the previously observed
      phenotype"
    explanation: >-
      States the contrast with the founding phenotype explicitly.

- category: Neurological
  name: Drug-Resistant Epilepsy
  description: >-
    Where seizures occur they are typically refractory to multiple antiseizure medications,
    though non-pharmacological approaches have achieved control in individual patients.
  phenotype_term:
    preferred_term: Refractory drug response
    term:
      id: HP:0020174
      label: Refractory drug response
  evidence:
  - reference: PMID:33438828
    reference_title: "Expansion of NEUROD2 phenotypes to include developmental delay without seizures."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both patients were non-responsive to multiple antiepileptic medications, one
      becoming seizure-free with a ketogenic diet, the other with a vagal nerve stimulator"
    explanation: >-
      Documents non-response to multiple drugs, and simultaneously records that two
      non-drug approaches each achieved seizure freedom - which is why this entry does not
      describe the epilepsy as untreatable.

prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Eleven patients from eight families in the defining 2021 cohort, which subsumed the
    five families identified in the same work; two further children were reported in the
    2018 founding study. No population prevalence estimate exists.
  evidence:
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identified eleven patients from eight families with a neurodevelopmental
      disorder including intellectual disability and ASD associated with NEUROD2 pathogenic
      mutations"
    explanation: >-
      The largest reported case count, which is the only occurrence measure available.

genetic:
- name: NEUROD2
  gene_term:
    preferred_term: NEUROD2
    term:
      id: hgnc:7763
      label: NEUROD2
  relationship_type: CAUSATIVE
  association: >-
    Heterozygous de novo variants in NEUROD2 reduce the activity of the encoded
    transcription factor and cause DEE72. Reported pathogenic variants cluster in the bHLH
    domain, the DNA-binding module: p.Glu130Gln, p.Met134Thr and p.Arg129Trp all fall in the
    conserved DNA-binding basic region of the first helix, and p.Leu163Pro lies in the
    second helix, also DNA-binding and also highly conserved. p.Glu130Gln is recurrent
    across unrelated families. In cellular assay the variants are hypomorphic rather than
    null - markedly less effective than wild type in a neuron-induction assay, but not
    inert.
  evidence:
  - reference: PMID:30323019
    reference_title: "De novo pathogenic variants in neuronal differentiation factor 2 (NEUROD2) cause a form of early infantile epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified novel de novo variants in neuronal differentiation factor 2
      (NEUROD2) in two unrelated children with early infantile epileptic encephalopathy"
    explanation: >-
      The gene-disease assertion from the founding study.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "De novo mutations Glu130Gln, Met134Thr, and Arg129Trp from Families 1, 2, and
      4 are found in the conserved DNA-binding region of the bHLH domain, which is the basic
      region of the first helix"
    explanation: >-
      Locates three of the reported variants in the bHLH DNA-binding basic region, and
      names Glu130Gln as arising independently in more than one family.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The de novo Leu163Pro mutation from Family 3 lies in the second helix of the
      bHLH domain thought to be important for DNA binding and is also highly conserved"
    explanation: >-
      Places the fourth variant in the same functional module, which is what makes the bHLH
      clustering a spectrum-level observation rather than a coincidence of two variants.
  - reference: PMID:34188164
    reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Mice heterozygous for Neurod2 had similar defects, indicating that Neurod2 is
      haploinsufficient"
    explanation: >-
      The dosage evidence. Curated MODEL_ORGANISM because it is a mouse genetic result, and
      see the note below on how it sits with the hypomorphic reading.
  notes: >-
    Haploinsufficiency and hypomorphism are not competing claims here, and the entry should
    not be read as leaving two readings live. They are measurements of different things.
    Haploinsufficiency is a statement about gene DOSAGE in mouse: one wild-type Neurod2 copy
    is not enough, since heterozygotes show the same defects as nulls in kind if milder in
    degree. Hypomorphism is a statement about the patient ALLELE: the mutant protein retains
    partial activity in a neuron-induction assay rather than none. A haploinsufficient gene
    carrying a partially active allele is exactly the expected architecture for a dominant
    disorder of this kind - the mutant contributes some activity, the total falls below the
    threshold the mouse data show exists, and the phenotype follows. What is NOT established
    by any source available to this entry is whether the patient alleles additionally act
    dominant-negatively against the wild-type copy, which would be a third and distinct
    claim.
    A nomenclature hazard worth recording. One of the sources cited here, the Xenopus laevis
    CRISPR model, repeatedly designates this disorder DEE75. That designation belongs to a
    different disease: DEE75 is MONDO:0032752, OMIM 618437, caused by PARS2. NEUROD2 is
    DEE72, MONDO:0032710, OMIM 618374, which carries EIEE72 as an exact synonym. The paper
    is cited here for its findings, which concern NEUROD2 and are not in doubt, but its DEE
    number is not propagated into this entry. A future curator should not "correct" DEE72 to
    DEE75 on the strength of that paper.

diagnosis:
- name: Electroencephalography
  description: >-
    EEG in the spasms presentation shows multifocal independent spikes, and improves
    markedly with effective treatment - making it useful for following response as well as
    for diagnosis.
  diagnosis_term:
    preferred_term: Electroencephalography
    term:
      id: NCIT:C38054
      label: Electroencephalography
  evidence:
  - reference: PMID:36494631
    reference_title: "Epileptic spasms related to neuronal differentiation factor 2 (NEUROD2) mutation respond to combined vigabatrin and high dose prednisolone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Electroencephalogram before treatment showed multifocal independent spikes
      predominantly in both posterior head regions and demonstrated marked improvement
      following combined vigabatrin and high-dose prednisolone treatment"
    explanation: >-
      Records both the characteristic interictal pattern and its response to treatment.

- name: Whole Exome Sequencing
  description: >-
    The gene was identified by exome sequencing and diagnosis remains genotype-driven.
  diagnosis_term:
    preferred_term: Whole Exome Sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  evidence:
  - reference: PMID:30323019
    reference_title: "De novo pathogenic variants in neuronal differentiation factor 2 (NEUROD2) cause a form of early infantile epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We used whole exome sequencing to identify candidate genes"
    explanation: >-
      Establishes the diagnostic route by which the gene-disease relationship was found.

treatments:
- name: Combined Vigabatrin and High-Dose Prednisolone
  description: >-
    The one treatment in this entry with a documented positive response. A genotype-confirmed
    patient with epileptic spasms responded to combined vigabatrin and high-dose
    prednisolone, with marked EEG improvement. This is a single case, so it establishes that
    the standard spasms regimen can work in this genotype - not a response rate.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: vigabatrin
      term:
        id: CHEBI:63638
        label: vigabatrin
    - preferred_term: prednisolone
      term:
        id: CHEBI:8378
        label: prednisolone
  evidence:
  - reference: PMID:36494631
    reference_title: "Epileptic spasms related to neuronal differentiation factor 2 (NEUROD2) mutation respond to combined vigabatrin and high dose prednisolone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Electroencephalogram before treatment showed multifocal independent spikes
      predominantly in both posterior head regions and demonstrated marked improvement
      following combined vigabatrin and high-dose prednisolone treatment"
    explanation: >-
      The measured response to the combination, reported as an objective EEG change rather
      than as a clinical impression. Preferred over the paper's title, which states the same
      result less precisely.
  - reference: PMID:36494631
    reference_title: "Epileptic spasms related to neuronal differentiation factor 2 (NEUROD2) mutation respond to combined vigabatrin and high dose prednisolone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "there are limited data about the treatment course of ES with combined
      vigabatrin and high-dose prednisolone in the NEUROD2-related NDD syndrome"
    explanation: >-
      The authors' own statement of how thin the evidence base is, which is why this entry
      curates the response as a single documented case rather than as an expected outcome.

- name: Ketogenic Diet
  description: >-
    One reported patient became seizure-free on a ketogenic diet after failing multiple
    antiseizure medications.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Dietary Intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  evidence:
  - reference: PMID:33438828
    reference_title: "Expansion of NEUROD2 phenotypes to include developmental delay without seizures."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both patients were non-responsive to multiple antiepileptic medications, one
      becoming seizure-free with a ketogenic diet, the other with a vagal nerve stimulator"
    explanation: >-
      Documents seizure freedom on a ketogenic diet in a drug-refractory patient.

- name: Vagus Nerve Stimulation
  description: >-
    A second drug-refractory patient became seizure-free with a vagal nerve stimulator.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: Implanted vagus nerve stimulation
  notes: >-
    Deliberately left unbound - needs term / NTR. NCIT's only vagus-nerve option is
    NCIT:C203750 Transcutaneous Auricular Vagus Nerve Stimulation, which is a different,
    non-implanted modality; the cited patient had an implanted vagal nerve stimulator.
    Binding the transcutaneous term would misstate the intervention, and no NCIT term for
    implanted vagus nerve stimulation was found.
  evidence:
  - reference: PMID:33438828
    reference_title: "Expansion of NEUROD2 phenotypes to include developmental delay without seizures."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "one becoming seizure-free with a ketogenic diet, the other with a vagal nerve
      stimulator"
    explanation: >-
      Documents seizure freedom with vagus nerve stimulation in the second refractory
      patient.

animal_models:
- name: Neurod2 knockout and heterozygous mouse
  species: Mouse
  genotype: Neurod2 constitutive knockout (KO) and heterozygote (HET)
  publication: PMID:34188164
  description: >-
    The best-matched model for the lamination arm of this disorder, and the one that
    supplies the dosage evidence. Both null and heterozygous animals were characterized, in
    a mammalian six-layered neocortex that forms inside-out by radial migration - the
    architecture the Xenopus model cannot provide. The heterozygote matters specifically:
    patients are heterozygous, so the HET arm is the genotype-matched one.
  modeled_mechanisms:
  - target: Disrupted Cortical Neuron Migration and Lamination
    relationship: RECAPITULATES
    fidelity: HIGH
    limitations: >-
      Mouse and human neocortical development differ in scale, in the extent of the outer
      subventricular zone and in gyrification, so the magnitude of a migration defect does
      not transfer quantitatively. The mouse also carries a null or heterozygous-null
      allele rather than the patients' hypomorphic missense alleles, so it models the
      dosage consequence rather than the specific allele.
    description: >-
      Cortical projection neurons over-migrate, shifting the final position and size of
      cortical layers, in both null and heterozygous animals.
    readouts:
    - name: Radial position of cortical projection neurons
      target: Disrupted Cortical Neuron Migration and Lamination
      direction: ALTERED
      interpretation: >-
        Neurons over-migrate rather than under-migrate - they end up too superficial, and
        the layers are correspondingly displaced. The direction is worth stating because
        the intuitive prediction for a migration defect is the opposite one.
      evidence:
      - reference: PMID:34188164
        reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "In Neurod2 KO embryos, cortical projection neurons over-migrated, thereby
          altering the final size and position of layers"
        explanation: >-
          The migration measurement behind this readout.
    - name: Over-migration in heterozygotes
      target: Disrupted Cortical Neuron Migration and Lamination
      direction: ALTERED
      interpretation: >-
        The same defect in the genotype-matched heterozygote, which is what makes the
        model's relevance to a dominant human disorder more than an inference from the null.
      evidence:
      - reference: PMID:34188164
        reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Mice heterozygous for Neurod2 had similar defects, indicating that Neurod2
          is haploinsufficient"
        explanation: >-
          Establishes that one functional copy is insufficient, in the same assay.
    evidence:
    - reference: PMID:34188164
      reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Over-migration was maintained post-migration, at P7"
      explanation: >-
        The defect persists past the migratory period rather than being a transient delay,
        which is what makes it informative for the lamination node rather than only for
        migration timing.
  - target: Neuronal Hyperactivity
    relationship: RECAPITULATES
    fidelity: HIGH
    limitations: >-
      Recorded in layer 5 neurons of juvenile mice; the measurement is cell-intrinsic
      excitability and does not by itself establish network-level hypersynchrony.
    description: >-
      Increased intrinsic excitability in layer 5 cortical projection neurons.
    readouts:
    - name: Intrinsic excitability of layer 5 neurons
      target: Neuronal Hyperactivity
      direction: INCREASED
      interpretation: >-
        Patch-clamp recordings show increased intrinsic excitability, the cell-autonomous
        correlate of the hyperactivity node.
      evidence:
      - reference: PMID:34188164
        reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Patch-clamp recordings in layer 5 neurons of juvenile mice revealed
          increased intrinsic excitability"
        explanation: >-
          The electrophysiological measurement behind this readout.
    evidence:
    - reference: PMID:34188164
      reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In juvenile and adults, spine density and turnover were dysregulated in
        apical but not basal compartments in layer 5 neurons"
      explanation: >-
        The structural synaptic correlate in the same cells. The compartment specificity -
        apical but not basal - is preserved rather than generalized to "synaptic defects".
  - target: Seizures
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    limitations: >-
      Spontaneous seizures were seen only occasionally in the null, and the source gives no
      count, frequency or EEG characterization. This is a behavioural observation reported
      in passing among the ASD-like phenotypes, not a quantified epilepsy phenotype, and it
      is not reported for the genotype-matched heterozygote at all.
    description: >-
      Occasional spontaneous seizures alongside the ASD-like behavioural phenotype.
    readouts:
    - name: Spontaneous seizure occurrence
      target: Seizures
      direction: INCREASED
      interpretation: >-
        Present but occasional. The hedge is the source's own and is preserved rather than
        upgraded to a seizure phenotype.
      evidence:
      - reference: PMID:34188164
        reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Neurod2 KO mice displayed social interaction deficits, stereotypies,
          hyperactivity, and occasionally spontaneous seizures"
        explanation: >-
          Curated PARTIAL: the word "occasionally" is doing real work and no count is given.
          The same sentence is the primary evidence for the ASD-like behavioural phenotype,
          which is much better characterized in this model than the seizures are.
    evidence:
    - reference: PMID:34188164
      reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "social interaction deficits, stereotypies, hyperactivity, and occasionally
        spontaneous seizures"
      explanation: >-
        Curated PARTIAL for the seizure node specifically. The behavioural triad is well
        supported; the seizure observation is not quantified.

- name: Forebrain excitatory neuron-specific Neurod2 conditional knockout mouse
  species: Mouse
  genotype: Emx1-IRES-Cre; Neurod2 flox/flox (cKO)
  publication: PMID:34188164
  description: >-
    A conditional deletion restricted to forebrain excitatory neurons. Its purpose is
    causal attribution rather than phenotype reproduction: it tests whether the behavioural
    phenotype arises from within glutamatergic neurons or from elsewhere in the brain, which
    the constitutive knockout cannot distinguish.
  modeled_mechanisms:
  - target: Reduced Proneural Transcription Factor Activity
    relationship: PERTURBS
    fidelity: HIGH
    limitations: >-
      Emx1-Cre deletes across forebrain excitatory neurons broadly and from early
      development, so it localizes the requirement to that population without resolving
      which region, layer or developmental window within it is responsible.
    description: >-
      Cell-type-restricted deletion isolating the contribution of forebrain excitatory
      neurons.
    evidence:
    - reference: PMID:34188164
      reference_title: "Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We generated Neurod2flox/flox mice and crossed them with Emx1IRESCre mice to
        assess the specific contribution of forebrain excitatory neurons to the ASD-related
        phenotypes"
      explanation: >-
        States the design and its purpose - attributing the phenotype to a cell type rather
        than reproducing it.
  notes: >-
    This model is the basis for the cell-autonomy claim in the source's own title. It is
    curated as PERTURBS rather than RECAPITULATES because what it contributes is the
    localization of the requirement, not a demonstration that the human phenotype is
    reproduced - the constitutive knockout above does that.

- name: Xenopus laevis NeuroD2 CRISPR knockdown tadpole
  species: Xenopus laevis
  genotype: NeuroD2.S CRISPR/Cas9 edited
  publication: PMID:38788202
  description: >-
    A CRISPR knockdown tadpole that reproduces seizure behaviour and network hyperactivity,
    and that produced the entry's most unexpected finding - a leaky blood-brain barrier -
    together with a pharmacological rescue acting on it.
  modeled_mechanisms:
  - target: Neuronal Hyperactivity
    relationship: RECAPITULATES
    fidelity: MODERATE
    limitations: >-
      The Xenopus forebrain is lissencephalic, unlayered, and forms outside-in, whereas the
      human neocortex is six-layered and forms inside-out via radial migration. Since the
      proposed human mechanism runs through disrupted radial migration and lamination, the
      model cannot test the step it is being used to support, and higher cognitive
      phenotypes cannot be assessed at all.
    description: >-
      Calcium imaging shows prolonged signals sweeping through the brain.
    readouts:
    - name: Brain-wide calcium signal
      target: Neuronal Hyperactivity
      direction: INCREASED
      interpretation: >-
        Prolonged, strong signals sweeping through the brain.
      evidence:
      - reference: PMID:38788202
        reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Live imaging of Ca2+ signaling revealed prolongued, strong signals
          sweeping through the brain, indicative of neuronal hyperactivity"
        explanation: >-
          The imaging measurement behind this readout.
    evidence:
    - reference: PMID:38788202
      reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "NeuroD2.S CRISPR/Cas9 edited tadpoles were more active, swam faster on
        average, and had more seizures"
      explanation: >-
        Establishes the behavioural seizure phenotype that makes the model informative.
  - target: Blood-Brain Barrier Permeability
    relationship: RECAPITULATES
    fidelity: LOW
    limitations: >-
      The barrier phenotype has been demonstrated only in tadpoles. No human data establish
      that blood-brain barrier permeability is altered in NEUROD2 patients, so this arm rests
      entirely on the model - which is why it carries a HUMAN_MODEL_MISMATCH discussion
      rather than being presented as an established part of the human disease.
    description: >-
      Increased barrier permeability, rescued alongside seizures by losartan.
    readouts:
    - name: Blood-brain barrier permeability
      target: Blood-Brain Barrier Permeability
      direction: INCREASED
      interpretation: >-
        The barrier is leakier than in sibling controls.
      evidence:
      - reference: PMID:38788202
        reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "the blood-brain barrier (BBB) was found to be leakier than that of
          controls"
        explanation: >-
          The permeability measurement behind this readout.
    - name: Seizure events under losartan
      target: Blood-Brain Barrier Permeability
      direction: DECREASED
      interpretation: >-
        A TGF-beta antagonist that acts on the barrier reduced seizure events more than
        four-fold, which is the experiment linking the barrier arm to the seizures.
      evidence:
      - reference: PMID:38788202
        reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Treatment of NeuroD2 CRISPant tadpoles with 5 mM Losartan decreased
          seizure events by more than 4-fold compared to the baseline"
        explanation: >-
          The rescue measurement behind this readout.
    evidence:
    - reference: PMID:38788202
      reference_title: "Knockdown of NeuroD2 leads to seizure-like behavior, brain neuronal hyperactivity and a leaky blood-brain barrier in a Xenopus laevis tadpole model of DEE75."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Losartan was shown to have a short-term protective effect, reducing
        neuronal hyperactivity and reducing permeability of the BBB"
      explanation: >-
        Supports treating the barrier as a mechanistically involved arm rather than an
        incidental finding, since acting on it improves the neuronal phenotype. The word
        "short-term" is retained because durability was not established.

discussions:

- discussion_id: mismatch_bbb_arm_rests_entirely_on_tadpole
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Blood-Brain Barrier Permeability
  prompt: >-
    Is the blood-brain barrier defect part of the human disorder, or a feature of the
    tadpole model?
  rationale: >-
    This is the entry's most interesting claim and its least established. A leaky
    blood-brain barrier is a non-neuronal contributor to epileptogenesis in a disorder
    caused by a neuronal transcription factor, and the losartan experiment gives it causal
    weight in the model: a TGF-beta antagonist reduced both barrier permeability and seizure
    events more than four-fold. But every part of that sits in Xenopus. No human data
    establish altered barrier permeability in NEUROD2 patients. The stake is unusually
    concrete, because losartan is an approved drug in wide human use, so a positive human
    finding would point directly at a repurposing candidate - and a negative one would
    remove the rationale entirely. The rescue is also described by its own authors as
    short-term, so even within the model durability is unestablished.
  proposed_experiments:
  - experiment_id: exp_bbb_integrity_in_neurod2_patients
    name: Barrier integrity in NEUROD2 patients
    description: >-
      Assess blood-brain barrier integrity in genotype-confirmed NEUROD2 patients using
      contrast-enhanced imaging or CSF-to-serum protein ratios, and compare against
      age-matched epilepsy controls, to determine whether the tadpole finding has a human
      counterpart before any repurposing trial is contemplated.

- discussion_id: mismatch_lissencephalic_model_for_a_lamination_mechanism
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Disrupted Cortical Neuron Migration and Lamination
  prompt: >-
    Can a lissencephalic, unlayered, outside-in brain test a mechanism defined by
    inside-out radial migration into a six-layered cortex?
  rationale: >-
    The proposed human mechanism runs through disrupted radial migration and layer-specific
    differentiation of cortical projection neurons. The principal in vivo model is the
    Xenopus tadpole, whose forebrain is lissencephalic and unlayered and forms from the
    outside in, so the oldest neurons end up outermost - the opposite ordering to the human
    neocortex. The model therefore cannot test the lamination step it is being used to
    support; what it can show is that reduced NeuroD2 activity produces seizures and network
    hyperactivity, which it does. The mouse work on cortical over-migration and layer 5
    positioning is the better-matched evidence for the lamination arm, and this entry marks
    the edge from lamination to hyperactivity as indirect with unknown intermediates rather
    than treating the tadpole seizure phenotype as confirmation of the migration account.
  proposed_experiments:
  - experiment_id: exp_layer_resolved_migration_in_a_gyrencephalic_model
    name: Layer-resolved migration phenotype in a layered cortex
    description: >-
      Characterise laminar position and radial migration of cortical projection neurons in a
      Neurod2 hypomorphic mouse carrying a patient-equivalent allele, rather than a null, and
      determine whether mis-lamination is present at the allele dosage that causes human
      disease.

- discussion_id: gap_seizures_are_not_obligatory
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Seizures
  prompt: >-
    What determines whether a NEUROD2 variant carrier develops epilepsy at all?
  rationale: >-
    The disorder is named and defined as an epileptic encephalopathy, but at least one
    individual with a de novo NEUROD2 missense variant has developmental delay and no
    seizures. That is not a minor phenotypic footnote: it means the seizures are a frequent
    consequence rather than a defining one, and it raises the question of what separates
    carriers who develop epilepsy from those who do not - allele severity, modifier
    genotype, or something environmental. The entry therefore curates developmental delay as
    the constant feature and seizures as a frequent but non-obligatory one. The seizure
    phenotype does carry a frequency band, FREQUENT, taken from the counted 3 of 7 assessed
    patients - but that number should be read as a ceiling rather than as a population
    estimate. The reported cohort is small, and it was ascertained through epilepsy: the
    disorder was named and first described from epileptic encephalopathy cases, so carriers
    without seizures are exactly the ones least likely to have been found. Ascertainment
    through the phenotype being counted inflates its apparent frequency, so 3 of 7 is an
    upper bound; a denominator assembled through non-epilepsy channels would almost
    certainly put the figure lower.
  proposed_experiments:
  - experiment_id: exp_genotype_stratified_seizure_penetrance
    name: Seizure penetrance stratified by allele activity
    description: >-
      Assay residual transcriptional activity for each reported NEUROD2 patient allele in a
      common reporter system, and test whether residual activity predicts the presence or
      absence of epilepsy across carriers. Ascertainment through non-epilepsy channels, such
      as developmental-delay cohorts, would be needed to avoid the bias that currently makes
      seizures look obligatory.

notes: >-
  Nomenclature: one cited source designates this disorder DEE75. That number belongs to a
  different disease - DEE75 is MONDO:0032752, OMIM 618437, caused by PARS2 - while NEUROD2
  is DEE72, MONDO:0032710, OMIM 618374. The discrepancy was resolved against MONDO rather
  than either publication, and the paper is cited for its findings without its DEE number
  being carried across.
  Scope: the TGF-beta/losartan arm is curated as a model finding with an explicit
  HUMAN_MODEL_MISMATCH, not as a treatment. No human has been treated with losartan for this
  disorder, and the entry deliberately does not create a treatment entry that would imply
  otherwise.
📚

References & Deep Research

Deep Research

1
Claude Code ▸
NEUROD2-Related Developmental and Epileptic Encephalopathy (DEE72): Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 16 citations 2026-08-20T12:17:10.268438

NEUROD2-Related Developmental and Epileptic Encephalopathy (DEE72): Comprehensive Research Report

1. Disease Information

Overview: NEUROD2-related developmental and epileptic encephalopathy (also designated Developmental and Epileptic Encephalopathy 72, DEE72; also described in the literature as "NEUROD2-related disorder" or "NEUROD2 neurodevelopmental syndrome") is a rare, autosomal dominant neurodevelopmental disorder caused by heterozygous, typically de novo, pathogenic variants in NEUROD2 on chromosome 17q12. It was first described in 2019 (Sega et al., Journal of Medical Genetics, PMID:30323019) in two unrelated children with early infantile epileptic encephalopathy, and the phenotypic spectrum was substantially expanded by Runge et al. (2021, Molecular Psychiatry, PMID:34667263) to 11 patients from 8 families, and further by later case reports including patients without seizures (Rots et al./Guerin et al., Am J Med Genet A, PMID:33438828) and neonatal-onset presentations (Exploration Pub case report, 2024).

Core features across the spectrum: developmental delay/intellectual disability, autism spectrum disorder (ASD) features, and — in a subset — early-onset (often infantile-spasm/West syndrome-type) epilepsy that is frequently treatment-refractory. Not all patients have seizures; the phenotype is now understood as a continuum from isolated developmental delay/ASD to a severe DEE with infantile spasms.

Key identifiers: - Gene: NEUROD2 (Neuronal Differentiation 2), HGNC:7763 (per GeneCards/Wikigenes sourcing; some sources list 7761 — confirm against current HGNC), NCBI Gene ID 4762, chromosome 17q12 - OMIM Gene: 601725 — NEUROGENIC DIFFERENTIATION 2; NEUROD2 - OMIM Phenotype: #618374 — DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 72; DEE72 - UniProt (human protein): Q15784 (Neurogenic differentiation factor 2 / NDF2 / NEUROD2) - Inheritance: Autosomal dominant, virtually all reported cases de novo (one familial transmission reported: Runge cohort case with c.804C>A/p.Arg268Trp segregating with a milder phenotype in a parent) - Synonyms:* NDF2, NEUROD-related developmental disorder, DEE72; historically the gene product is also called "NDRF" (NeuroD-related factor) or "bHLHa1"

Note on data provenance: All information below is derived from aggregated case series and case reports in the peer-reviewed literature (not large-scale EHR/registry data), reflecting the rarity of the condition (currently >20 published cases across all reports).

Sources: OMIM #618374, OMIM *601725, GeneCards NEUROD2, UniProt Q15784

2. Etiology

Disease causal factor: Monogenic — heterozygous loss-of-function (predominantly missense, DNA-binding/dimerization-domain) variants in NEUROD2, a proneural basic helix-loop-helix (bHLH) transcription factor gene. All functionally tested pathogenic variants show reduced or absent transactivation/DNA-binding capacity in cellular (P19 embryonal carcinoma cell differentiation) and in vivo (Xenopus laevis ectopic-neuron induction) assays, consistent with loss of function via haploinsufficiency — heterozygous Neurod2 knockout mice recapitulate defects seen in homozygous nulls, confirming dosage sensitivity (Runge et al. 2021, PMID:34667263).

Genetic risk factors: - De novo heterozygous missense variants clustering in the bHLH DNA-binding/dimerization domain (residues ~120–170) are associated with the most severe (DEE/infantile spasms) phenotype: p.Glu130Gln (recurrent — reported in at least 4 independent patients), p.Met134Thr, p.Arg129Trp, p.Glu130Lys, p.Leu163Pro. - Variants outside the canonical bHLH hotspot (e.g., p.Ala235Thr, p.Arg268Trp, p.Ala264Thr) are associated with milder phenotypes (developmental delay/ASD without seizures, or mild ID), though a 2024 neonatal-onset case (p.Ala264Thr, outside the bHLH domain) demonstrated that severe disease can arise from non-canonical regions too — indicating genotype-phenotype correlation is imperfect. - No established genetic modifier loci or susceptibility variants reported to date; no protective genetic variants described. - gnomAD: all reported pathogenic variants are absent from population databases (gnomAD v2/v4), consistent with strong purifying selection against NEUROD2 loss-of-function alleles, though a formal published pLI/LOEUF constraint value for NEUROD2 was not identified in this search.

Environmental risk factors: None established; this is a purely monogenic Mendelian disorder with no known environmental, toxin, infectious, or lifestyle contributors identified in the literature to date.

Gene-environment interactions: None reported.

Sources: Sega et al. 2019, PMID:30323019; Runge et al. 2021, Mol Psychiatry, PMID:34667263; Rots et al./Guerin, PMID:33438828; NEUROD2-related disorder neonatal-onset case report, Exploration Pub 2024

3. Phenotypes

Core clinical features (aggregated from ~15–22 published cases):

Phenotype Type Frequency (approx.) Onset Course Suggested HPO term
Global developmental delay / intellectual disability Clinical sign Near-universal (primary defining feature) Infancy–early childhood Stable to progressive; variable severity HP:0001263 (Global developmental delay); HP:0001249 (Intellectual disability)
Infantile spasms / West syndrome Symptom/seizure type Subset (severe end of spectrum, ~5/11–3/7 in various series) ~5 months (range: neonatal–infancy) Often refractory to standard ASMs HP:0011097 (Infantile spasms); HP:0002373 (Hypsarrhythmia)
Epilepsy (general, not otherwise specified) Symptom Variable across series (~30–50%) Infancy to childhood Often drug-resistant HP:0001250 (Seizure)
Autism spectrum disorder features Behavioral Common, "core phenotype" per Runge et al. Early childhood Stable HP:0000729 (Autistic behavior)
ADHD symptoms / hyperactivity Behavioral ~5/7 (Runge cohort) Childhood Stable HP:0007018 (Attention deficit hyperactivity disorder); HP:0000737 (Irritability)/HP:0000722 (Hyperactivity)
Hypotonia Sign Common in infantile-onset cases Neonatal/infantile Often improves partially HP:0001252 (Hypotonia)
Hyperkinetic movements / stereotypies Behavioral/motor Variable, more common infantile-onset severe cases Infancy–childhood Chronic HP:0002119 (Hyperkinesia); HP:0000733 (Stereotypy)
Absent or impaired walking Motor Common in severe cases Persistent Static/lifelong HP:0002540 (Inability to walk)
Absent or impaired language Speech Common in severe cases Persistent Static/lifelong HP:0002465 (Absent speech); HP:0000750 (Delayed speech and language)
Cortical visual impairment Sensory Variable feature Infancy Variable HP:0100704 (Cerebral visual impairment)
Feeding difficulties / dysphagia Sign Common in neonatal-onset cases Neonatal Often improves HP:0011968 (Feeding difficulties); HP:0002015 (Dysphagia)
Respiratory depression/distress (neonatal) Sign Reported in severe neonatal-onset case Birth Transient HP:0002878 (Respiratory failure)
Rett-like features Behavioral Reported in ≥2 cases (p.Glu130Gln, p.Glu130Lys) Infancy–childhood Chronic HP:0002185 (Neurodevelopmental regression, Rett-like)
Microcephaly Growth Reported in a subset Infancy Static HP:0000252 (Microcephaly)
Central/generalized obesity Growth Reported in one case (p.Arg129Trp) Childhood Chronic HP:0001513 (Obesity)
Aggressive behavior Behavioral Reported (familial p.Arg268Trp case) Childhood/adult Chronic HP:0000718 (Aggressive behavior)
Fifth-finger clinodactyly, short stature Dysmorphic/growth Reported in one non-seizure case Congenital Static HP:0004209 (Clinodactyly of the 5th finger); HP:0004322 (Short stature)
Cardiac septal defect (VSD) Structural Reported in one case (p.Leu163Pro) Congenital — HP:0001629 (Ventricular septal defect)
Subcortical white-matter T2 hyperintensity Neuroimaging Reported in neonatal-onset case Infancy — HP:0002500 (delayed myelination)/nonspecific white matter signal change
Bilateral putaminal T2 signal change, thin corpus callosum Neuroimaging Reported (Sega case 1) Infancy — HP:0002079 (Hypoplasia of the corpus callosum)
Discontinuous/burst-suppression-like EEG EEG Reported in neonatal-onset case Neonatal — HP:0010851 (Burst-suppression); HP:0011182 (Electroencephalographic abnormality)

Age of onset: Bimodal — a severe neonatal/early-infantile presentation with respiratory depression, hypotonia, feeding difficulty, and seizures within the first weeks-to-months of life (infantile spasms peaking ~5 months), versus a milder presentation recognized later in childhood/adolescence with developmental delay/ASD and no seizures.

Severity/progression: Highly variable expressivity even for the same variant (e.g., p.Glu130Gln reported with DEE/infantile spasms in most carriers but developmental delay/ID±ASD without seizures in at least one). Disease course is generally static/non-progressive developmentally once the acute neonatal/infantile period resolves, though seizures can remain drug-resistant long-term in the severe subgroup.

Quality of life impact: Severely delayed or absent independent ambulation and language in the severe DEE subgroup substantially impacts activities of daily living and requires lifelong multidisciplinary support (physiotherapy, speech therapy, special education); the milder ASD/ID-only subgroup has better functional independence but persistent learning, social, and attentional impairment.

Sources: Sega et al. 2019; Runge et al. 2021 (PMC commentary summary); Guerin/Rots et al. 2021, PMID:33438828; neonatal case report 2024; OMIM #618374

4. Genetic / Molecular Information

Causal gene: NEUROD2 (OMIM 601725), a single-exon-poor, intron-containing gene on 17q12 encoding a class II bHLH transcription factor of the NeuroD family (paralogs: NEUROD1, NEUROD4, NEUROD6, ATOH1, NEUROG1/2*).

Reported pathogenic/likely pathogenic variants (composite literature list, cDNA reference NM_006160):

Variant (cDNA) Protein Domain Inheritance Recurrence Associated phenotype
c.385C>T p.Arg129Trp bHLH basic domain De novo 1 DD/ID±ASD, central obesity
c.388G>C p.Glu130Gln bHLH basic domain De novo ≥4 (recurrent hotspot) DEE/infantile spasms (most), also DD/ID±ASD/Rett-like in some carriers
c.388G>A p.Glu130Lys bHLH basic domain De novo 1 Severe delay, Rett-like/stereotypies
c.401T>C p.Met134Thr bHLH basic domain De novo 1 DEE/infantile spasms
c.488T>C p.Leu163Pro bHLH second helix De novo 1 DD/ID without seizures, VSD
c.703G>A p.Ala235Thr Outside bHLH Unknown/uncertain 1 ASD/DD (functional testing showed normal activity — possible non-causal)
c.790G>A p.Ala264Thr Outside bHLH (exon 2) De novo 1 Neonatal-onset DEE, ASD
c.804C>A p.Arg268Trp Outside bHLH Familial (1) and unknown/de novo (1) 2 DD/ID±ASD, aggressive behavior (familial); mild ID (isolated)

Functional testing (P19 embryonal carcinoma neuronal-differentiation assay and Xenopus ectopic-neuron induction) demonstrates that pathogenic missense variants impair or abolish NEUROD2's ability to induce neuronal differentiation — wild-type NEUROD2 induces ectopic neurons in ~90% of assayed cells, while the most severe variants (e.g., p.Glu130Gln) show near-complete loss, and others (e.g., p.Met134Thr) show an intermediate ~45% activity, correlating loosely with phenotypic severity.

Variant classification: All confirmed pathogenic variants are missense, de novo (with one reported familial transmission), and classified pathogenic/likely pathogenic per ACMG/AMP criteria (PS2/PM1/PM2/PP3 typically invoked); absent from gnomAD.

Functional consequence: Loss-of-function via impaired DNA binding/dimerization (bHLH domain variants) or reduced transactivation capacity, producing haploinsufficiency — confirmed directly in mouse models where Neurod2+/- heterozygotes phenocopy (with reduced severity) Neurod2-/- homozygous nulls.

Modifier genes: None formally established, though variable expressivity even for the identical p.Glu130Gln variant across unrelated patients suggests unidentified genetic or stochastic modifiers.

Epigenetic information: Not specifically characterized for this disorder; NEUROD2 itself functions upstream of chromatin/gene-regulatory programs (it is a "pioneer-adjacent" proneural transcription factor cooperating with E-proteins) but no disease-specific DNA methylation or histone signature has been reported.

Chromosomal abnormalities: Disease is caused by intragenic point mutation, not by large chromosomal rearrangement; no microdeletion/microduplication syndrome involving 17q12 is described as the DEE72 mechanism (note: 17q12 recurrent microdeletion/duplication syndrome, involving HNF1B, is a distinct, unrelated genomic disorder that also happens to map to 17q12 but is a different condition).

Suggested GO terms for gene function: GO:0006357 (regulation of transcription by RNA polymerase II), GO:0030154 (cell differentiation), GO:0021953 (central nervous system neuron differentiation), GO:0000981 (DNA-binding transcription factor activity, RNA polymerase II-specific), GO:0046983 (protein dimerization activity)

Sources: Sega et al. 2019; Runge et al. 2021; Guerin/Rots et al. 2021; neonatal case report 2024; GeneCards NEUROD2; OMIM *601725

5. Environmental Information

No environmental factors, lifestyle factors, or infectious agents have been implicated as causal or contributory in NEUROD2-related DEE — it is a purely monogenic disorder with no reported gene-environment interaction literature.

6. Mechanism / Pathophysiology

Molecular pathway/protein function: NEUROD2 is a class II bHLH proneural transcription factor expressed at peak cortical excitatory neurogenesis, acting downstream of proneural genes and dimerizing with ubiquitous class I bHLH "E-proteins" (E2A/TCF3, HEB) to bind E-box (CANNTG) DNA elements in promoters of neuronal differentiation genes (e.g., GAP-43). ChIP/genome-wide target analysis shows NEUROD2 binds and regulates genes required for Reelin signaling (governing radial neuronal migration), layer-specific cortical differentiation, and axonal pathfinding of cortical projection neurons (PMID reference: BMC Genomics 2015 genome-wide target study).

Cellular processes/causal chain (from mouse and Xenopus models): 1. Trigger: Heterozygous loss-of-function NEUROD2 variant → reduced transcription factor DNA-binding/dimerization activity → haploinsufficiency 2. Cortical development defect: In Neurod2 knockout/heterozygous mouse embryos, cortical projection neurons over-migrate, altering the size and laminar position of cortical layers (particularly layer 5); amygdala nuclei (lateral and basolateral) fail to form properly in nulls, with reduced neuron numbers in heterozygotes 3. Synaptic/circuit defect: Altered dendritic spine density and turnover in layer 5 pyramidal neurons; dysregulated expression of genes controlling neuronal excitability and synaptic function (including AMPA receptor subunits, GABA-A receptor γ subunit, and the gene Ulip1), whose human orthologs are strongly enriched for ASD associations 4. Network hyperexcitability: Increased intrinsic neuronal excitability; in the Xenopus CRISPR knockdown model, calcium imaging reveals prolonged, strong hyperactivity signals sweeping through the brain, and behavioral C-shaped seizure-like contractions 5. Blood-brain barrier dysfunction: NeuroD2-deficient tadpoles show significantly increased BBB permeability (sodium fluorescein leakage 5.5–7.7× higher than controls), associated with elevated neural progenitor marker Vimentin and reduced BBB-associated aquaporin-1 expression — a novel, non-neuronal contributor to the seizure phenotype 6. Clinical output: Developmental delay/ID, ASD-like behaviors, hyperactivity/stereotypies, and — when excitability/BBB dysfunction crosses a threshold — clinical seizures, often as infantile spasms

Cell types involved: Cortical excitatory/glutamatergic projection neurons (primary), amygdala neurons (lateral/basolateral nuclei), radial glia/neural progenitors (Reelin-responsive migration), and blood-brain barrier endothelial/glial components (newly implicated).

Tissue damage mechanism: Not classic tissue injury (no oxidative stress/fibrosis/necrosis reported) — this is a neurodevelopmental circuit-wiring disorder: aberrant neuronal migration/lamination and synaptic dysregulation rather than degenerative tissue damage.

Molecular profiling data: Bulk RNA-sequencing in Neurod2 KO mouse cortex shows dysregulation of genes controlling neuronal excitability and synaptic function, with human orthologs strongly overlapping ASD risk-gene sets (Runge et al. 2021). Preliminary Xenopus transcriptomic data show altered neural progenitor and BBB-associated gene expression (elevated Vimentin, reduced aquaporin-1).

Emerging therapeutic mechanistic insight: In the Xenopus DEE72 model, the TGF-β pathway antagonist losartan reduced seizure-like C-shaped contractions by >4-fold and calcium hyperactivity spikes by nearly 4-fold, and transiently improved BBB integrity — implicating TGF-β/BBB-mediated hyperexcitability as a druggable downstream mechanism (a pathway also implicated in other genetic epilepsies with BBB involvement).

Suggested GO/CL terms: - GO:0021953 (central nervous system neuron differentiation), GO:0021799 (cerebral cortex radially oriented cell migration), GO:0007399 (nervous system development), GO:0035418 (protein localization to synapse), GO:0007268 (chemical synaptic transmission) - CL:0000679 (glutamatergic neuron), CL:0002605 (astrocyte of the cerebral cortex — BBB), CL:0000115 (endothelial cell — BBB) - UBERON:0001950 (neocortex), UBERON:0002884 (basolateral amygdaloid nucleus), UBERON:0001902 (epithelium of choroid plexus / BBB structures as relevant)

Sources: BMC Genomics 2015, genome-wide NEUROD2 target analysis; Frontiers 2021, Role of Neurod genes in brain development; Runge et al. 2021, Mol Psychiatry; Xenopus DEE72 model, PMC11228833; Lin et al. 2005, PNAS — amygdala/emotional learning, PMID:16203979

7. Anatomical Structures Affected

Organ level: Primary organ affected is the brain (central nervous system); no primary involvement of other organ systems is described (occasional congenital comorbidities such as a ventricular septal defect have been reported in single cases but are not considered core disease features).

Body systems: Nervous system (primary); secondary developmental/behavioral system involvement (cognitive, motor, psychiatric/behavioral).

Tissue/cell level: - Cerebral cortex — excitatory/glutamatergic projection neurons across cortical layers (particularly layer 5), affected by migration and lamination defects - Amygdala — lateral and basolateral nuclei, hypoplastic/absent in severe loss-of-function models - Blood-brain barrier — endothelial/glial limiting membrane components, showing increased permeability in models

Subcellular level: Nucleus (site of NEUROD2 transcription factor DNA binding/E-box activity); dendritic spines (altered density/turnover in layer 5 pyramidal neurons); synapse (altered excitatory/inhibitory receptor expression — AMPA and GABA-A receptor subunits).

Localization: Bilateral, diffuse cortical/subcortical involvement (not unilateral or focal); neuroimaging findings when present are typically bilateral (e.g., bilateral putaminal T2 signal change, thin corpus callosum, diffuse white matter signal change).

Suggested UBERON/GO-CC terms: UBERON:0000955 (brain), UBERON:0001950 (neocortex), UBERON:0002884 (basolateral amygdaloid nucleus), UBERON:0002360 (corpus callosum), UBERON:0001133 (neostriatum/putamen); GO:0005634 (nucleus), GO:0043198 (dendritic shaft)/GO:0043197 (dendritic spine)

Sources: Frontiers 2021 Neurod genes review; Lin et al. 2005 PNAS; Sega et al. 2019

8. Temporal Development

Onset: - Neonatal/early infantile subtype: Presents at birth or within the first weeks of life with respiratory depression, hypotonia, hyporeactivity, and feeding difficulties, followed within the first month(s) by neonatal/infantile seizures (documented as early as birth in the 2024 neonatal case report). - Infantile-spasm subtype: Infantile spasms/West syndrome onset around 5 months of age (OMIM #618374). - Later-recognized subtype: Developmental delay/ASD recognized in early-to-mid childhood without a seizure history (some patients identified only in adolescence/adulthood via exome sequencing, e.g., a 14-year-old and even adult mildly-affected relatives in familial cases).

Onset pattern: Insidious for the developmental-delay/ASD-predominant phenotype; acute/subacute for the neonatal-encephalopathy and infantile-spasms phenotypes.

Progression: Generally a static/stable neurodevelopmental encephalopathy after the acute neonatal/infantile period — this is not a degenerative disease. Seizures, when present, are frequently drug-resistant initially but some patients achieve seizure freedom with specific interventions (ketogenic diet, vagus nerve stimulation, or combined vigabatrin plus high-dose prednisolone for infantile spasms).

Disease course pattern: Chronic, lifelong; no spontaneous remission of the underlying neurodevelopmental phenotype is described, though seizure control can improve substantially with treatment (e.g., seizure freedom reported by 24 months in the neonatal-onset case with levetiracetam).

Critical periods: The prenatal/early postnatal period of cortical neurogenesis and migration (peak NEUROD2 expression window) is the biologically critical period during which the causal mechanism operates, though this is a developmental-window concept from animal models rather than a clinically actionable intervention window at present.

Sources: OMIM #618374; neonatal-onset case report 2024; Sega et al. 2019

9. Inheritance and Population

Epidemiology: Extremely rare — fewer than ~25 patients reported in the peer-reviewed literature as of 2024–2025 across all published case series (Sega 2019: 2 patients; Runge 2021: 11 patients from 8 families; Rots/Guerin 2021: 2 additional patients; subsequent isolated case reports: several more). No formal population prevalence or incidence estimate has been established (ultra-rare/ORPHA "not yet documented" tier equivalent).

Inheritance pattern: Autosomal dominant. The overwhelming majority of cases are de novo; one instance of familial (parent-to-child) transmission is reported (p.Arg268Trp), associated with a milder phenotype (mild ID in one relative, more pronounced ID/ASD/aggressive behavior in the child), suggesting reduced penetrance or variable expressivity is possible for milder alleles.

Penetrance: Appears to be high but not fully characterized quantitatively; the familial case suggests incomplete penetrance or highly variable expressivity for at least one variant (p.Arg268Trp).

Expressivity: Markedly variable — the same variant (p.Glu130Gln) has been reported with DEE/infantile spasms in the majority of carriers but with milder developmental delay/ID±ASD (no seizures) or Rett-like features in others, indicating expressivity is not tightly variant-determined and likely involves stochastic or unidentified modifier factors.

Genetic anticipation: Not reported/not applicable (missense disorder, not a repeat-expansion disease).

Germline mosaicism: Not specifically documented in the literature reviewed, though as with other de novo dominant NDDs it cannot be excluded as a recurrence-risk consideration for future pregnancies in unaffected parents.

Founder effects: None reported; variants have arisen independently (recurrent p.Glu130Gln likely reflects a mutational hotspot rather than a founder effect, given occurrence in unrelated families of different backgrounds).

Carrier frequency: Not applicable (dominant disorder, not applicable to "carrier" framing); population frequency of pathogenic variants is essentially zero in gnomAD.

Consanguinity role: Not implicated (autosomal dominant, de novo mechanism).

Population demographics: No specific ethnic, geographic, or sex-based enrichment has been reported; cases have been described across multiple countries/regions (North America, Europe) with both male and female patients affected in roughly comparable numbers across the small published cohort (e.g., Sega cases: 1 female, 1 male; broader cohort mixed).

Sources: Sega et al. 2019; Runge et al. 2021; Guerin/Rots et al. 2021, PMID:33438828; OMIM #618374

10. Diagnostics

Clinical/laboratory tests: No specific biochemical or laboratory biomarker exists; standard metabolic/biochemical workup in these patients is typically pursued to exclude alternative diagnoses (e.g., inborn errors of metabolism) and is generally unremarkable/nonspecific.

Imaging: Brain MRI findings are variable and sometimes normal; when abnormal, reported findings include bilateral putaminal T2 hyperintensity, thin corpus callosum, mild cerebral volume loss, and subcortical white matter T2 hyperintensity. MRI is not diagnostic on its own but supports the encephalopathy workup and excludes structural/acquired causes.

Electrophysiology (EEG): Central to diagnosis and monitoring in the seizure-associated subtype — findings include hypsarrhythmia (consistent with West syndrome/infantile spasms), excessively discontinuous/burst-suppression-like background patterns in neonatal-onset disease, and electrographic seizures with minimal clinical correlation.

Genetic testing (primary diagnostic modality): - Exome sequencing (trio, proband + parents) is the diagnostic method by which essentially all reported cases have been identified, given the absence of a recognizable clinical gestalt and the rarity/novelty of the gene-disease association. - Gene panels for developmental and epileptic encephalopathy or intellectual disability/autism increasingly include NEUROD2, given its established OMIM phenotype entry (#618374). - Chromosomal microarray is typically performed as part of standard first-tier NDD workup but does not detect the causal point mutations; it is used to exclude copy-number etiologies. - Single-gene Sanger sequencing confirmatory testing (used in reported cases to confirm de novo status by testing both parents). - Variant interpretation relies on ACMG/AMP criteria (absence from gnomAD, in silico deleteriousness — SIFT, PolyPhen-2, CADD — and, where available, functional assay data).

Differential diagnosis: Other genetic developmental and epileptic encephalopathies (e.g., STXBP1, SCN2A, SCN8A, CDKL5, KCNQ2 DEEs), Rett syndrome (MECP2 — explicitly excluded by genetic testing in at least one reported case), other syndromic autism/ID genes, and metabolic encephalopathies.

Screening: No population-level or newborn screening applicable (ultra-rare Mendelian disorder identified only via clinical exome/genome sequencing in symptomatic individuals); prenatal/preimplantation testing could theoretically be offered in families with a known variant (e.g., the reported familial case), though this is not documented as having occurred.

Sources: neonatal-onset case report 2024; Sega et al. 2019; Guerin/Rots et al. 2021; OMIM #618374

11. Outcome / Prognosis

Survival/mortality: No mortality has been reported in the published case series; this does not appear to be a life-limiting condition in the classic sense (unlike some severe DEEs), though the literature base is too small to generate a formal survival statistic.

Morbidity/function: Substantial and often lifelong: severely delayed or absent independent ambulation and expressive language reported in the severe infantile-spasm subgroup; more variable but still significant functional impairment (ID, ASD, ADHD) in the milder subgroup. No formal quality-of-life instrument (EQ-5D, SF-36) data specific to this condition were identified.

Disease course/complications: Drug-resistant epilepsy is the principal disease-specific complication in the severe subgroup; hyperkinetic movement disorders and cortical visual impairment are additional variable complications. Some patients achieve good seizure control with combination or nonpharmacologic approaches (ketogenic diet, VNS, vigabatrin + high-dose prednisolone), suggesting favorable seizure prognosis is achievable in at least a subset despite initial refractoriness.

Recovery potential: With early, aggressive antiseizure treatment, seizure freedom has been documented (e.g., seizure-free by 24 months on levetiracetam in the neonatal-onset case; seizure freedom with ketogenic diet in the more severe Sega variant carrier; seizure freedom with VNS in the milder Sega variant carrier). The neurodevelopmental (cognitive/ASD) phenotype does not appear to remit but can be supported with early intervention/therapy services.

Prognostic factors: Variant location (bHLH domain vs. outside) shows a loose correlation with severity but is not fully predictive (documented exceptions in both directions); presence/absence and severity of neonatal seizures appears to correlate with overall developmental outcome severity.

Sources: Sega et al. 2019; BMC Neurology vigabatrin/prednisolone case report 2022; neonatal-onset case report 2024

12. Treatment

Pharmacotherapy (antiseizure): - Levetiracetam — used successfully in the neonatal-onset case, with seizure control achieved by 24 months (NCIT:C29073, or generically NCIT:C15986 Pharmacotherapy + therapeutic_agent CHEBI levetiracetam) - Vigabatrin combined with high-dose prednisolone — a specific reported combination therapy for NEUROD2-associated epileptic spasms, with documented favorable response (BMC Neurology 2022 case report) — the standard first-line hormonal/GABAergic combination for infantile spasms/West syndrome of any etiology, here shown effective in a NEUROD2-confirmed case - Standard antiseizure medications are generally trialed first-line per usual DEE/infantile-spasms protocols, though initial refractoriness is common

Non-pharmacologic/device-based therapy: - Ketogenic diet — reported to achieve seizure freedom in a patient with the more severe E130Q (p.Glu130Gln) variant (NCIT:C15447, Dietary Intervention) - Vagus nerve stimulation (VNS) — reported to achieve seizure freedom in the M134T (p.Met134Thr) variant patient (NCIT device-based intervention; therapeutic_modality: DEVICE)

Investigational/mechanism-based approaches (preclinical): - Losartan (an angiotensin receptor blocker with TGF-β pathway antagonist activity) showed a >4-fold reduction in seizure-like behavior and calcium-imaging hyperactivity, plus transient improvement in blood-brain barrier integrity, in the Xenopus laevis NeuroD2 CRISPant model — a promising repurposing candidate not yet tested in human NEUROD2 patients (target_mechanisms: TGF-β pathway inhibition on the BBB-dysfunction/hyperexcitability node)

Supportive/rehabilitative care: - Multidisciplinary developmental support: physiotherapy, occupational therapy, speech and language therapy (documented as ongoing follow-up in the neonatal-onset case) - Nutritional/feeding support (orogastric tube feeding acutely, transition to oral feeding) for neonatal-onset presentations with feeding difficulty - Respiratory support (non-invasive ventilation) in severe neonatal presentations

Experimental treatments in trials: No disease-specific clinical trials for NEUROD2-related DEE were identified in this search (consistent with its extreme rarity and recent gene-disease discovery).

Treatment strategy: No formal evidence-based treatment algorithm exists specific to NEUROD2-DEE given the small case numbers; management follows general DEE/infantile-spasms treatment pathways (hormonal therapy ± vigabatrin as first line for spasms, escalation to ketogenic diet or neuromodulation for drug-resistant epilepsy), individualized based on response, alongside standard developmental/behavioral intervention for the ID/ASD phenotype.

Pharmacogenomics: No NEUROD2-specific pharmacogenomic data identified.

Sources: BMC Neurology 2022, vigabatrin + prednisolone case; Sega et al. 2019; Xenopus DEE72 model / losartan, PMC11228833; neonatal-onset case report 2024

13. Prevention

Primary prevention: Not applicable — this is a de novo genetic disorder with no known modifiable risk factor; no vaccination or exposure-avoidance strategy is relevant.

Secondary prevention/early detection: Early recognition via genetic testing (trio exome sequencing) in infants presenting with unexplained neonatal encephalopathy, hypotonia, and seizures could enable earlier targeted antiseizure treatment selection (e.g., prioritizing vigabatrin/prednisolone or ketogenic diet given documented efficacy signals in NEUROD2-specific cases) and earlier initiation of developmental therapies.

Genetic counseling: Recommended for families of an affected child given the predominantly de novo inheritance pattern (low empiric recurrence risk for future pregnancies, with residual risk from potential parental germline mosaicism not formally quantified for this gene). For the one reported familial case, predictive testing and reproductive counseling for at-risk relatives would be appropriate given documented intrafamilial transmission and variable expressivity.

Screening: No population or newborn screening program exists or is anticipated for this ultra-rare condition; diagnosis remains reactive (symptomatic testing) rather than proactive.

Prophylaxis: Not applicable.

Sources: General inference from inheritance data above; Sega et al. 2019; Guerin/Rots et al. 2021

14. Other Species / Natural Disease

Taxonomy: No naturally occurring NEUROD2-associated disease has been reported in non-human species (companion animals, livestock, or wildlife); no veterinary case series or OMIA entry was identified in this search.

Orthologous gene: Neurod2 is highly conserved; the mouse ortholog (NCBI Gene, chromosome 11) has been extensively studied via targeted knockout models (see Section 15). The variant residues implicated in human disease (e.g., Glu130, Met134) are described in the literature as "highly conserved across multiple species," supporting cross-species functional relevance of the bHLH domain.

Comparative biology: The bHLH DNA-binding mechanism and E-box-dependent proneural gene regulation are deeply conserved across vertebrates, which is why Xenopus laevis (frog) and Mus musculus (mouse) are both tractable and validated model systems for this human disease (see Section 15).

Transmission: Not applicable (non-infectious, non-zoonotic monogenic disorder).

15. Model Organisms

Mouse models (Mus musculus, NCBITaxon:10090):* - Neurod2 knockout (null) mice — the foundational model (Bormuth et al. and related lines), showing failure of lateral and basolateral amygdala nuclei formation, deficits in emotional learning (fear conditioning), and reduced expression of AMPA receptor subunits, GABA-A receptor γ subunit, and Ulip1 (Lin et al. 2005, PNAS, PMID:16203979). Cortical phenotypes include projection-neuron over-migration and altered layer 5 spine density/turnover, plus autism/schizophrenia-like behaviors (bioRxiv cortical morphofunctional study). - Neurod2* heterozygous (+/−) mice — directly model the human haploinsufficiency mechanism; phenocopy homozygous null defects (reduced amygdala neuron number, profound emotional-learning deficits), confirming dosage sensitivity (Lin et al. 2005; Runge et al. 2021). Behaviorally, KO and het mice show social interaction deficits, stereotypies, hyperactivity, and occasional spontaneous seizures (Runge et al. 2021, Molecular Psychiatry, PMID:34667263). - Fidelity/limitations: The mouse model recapitulates core ASD-like behavioral domains (sociability, stereotypy, hyperactivity) and some seizure susceptibility, and directly demonstrates the haploinsufficiency mechanism central to human disease — high translational relevance for the neurodevelopmental/behavioral phenotype. It has been less thoroughly characterized for the severe infantile-spasms/hypsarrhythmia EEG phenotype specifically. - Resources: MGI:107755 (Neurod2 mouse gene detail, Mouse Genome Informatics)

Xenopus laevis models (frog; NCBITaxon:8355): - CRISPR/Cas9 F0 "CRISPant" NeuroD2 knockdown/knockout tadpoles — two independent guide RNA strategies: an in-frame 15bp deletion removing 5 amino acids from the bHLH domain (rnk5), and a frameshift 4bp deletion producing a premature stop codon and truncated protein (rnk20). This model directly recapitulates seizure-like behavior (C-shaped contractions), neuronal hyperactivity on calcium imaging, and — notably — a leaky blood-brain barrier, a novel disease mechanism not previously described in the mouse literature (PMC11228833, 2024). - Fidelity: High construct validity (models the loss-of-function mechanism directly) and demonstrates strong face validity for the seizure phenotype (quantifiable seizure-like behavior and network hyperactivity), plus reveals a testable BBB-dysfunction mechanism. Used as a rapid in vivo drug-screening platform — losartan showed therapeutic effect in this model. - Earlier Sega et al. (2019) and Guerin/Rots et al. (2021) also used Xenopus mRNA microinjection "ectopic neuron induction" assays as the primary variant-functional-validation tool (wild-type NEUROD2 mRNA induces ectopic neurons in injected embryos; pathogenic variant mRNA fails to do so), establishing loss-of-function for each newly identified human variant.

Cellular models: - P19 mouse embryonal carcinoma cells — used as an in vitro neuronal-differentiation reporter assay to quantify the transactivation/differentiation-inducing capacity of wild-type versus mutant NEUROD2 protein (wild-type ~90% differentiation efficiency; loss-of-function variants show reduced-to-absent, or intermediate ~45%, efficiency) (Runge et al. 2021).

Applications: These models collectively enable (1) variant-level functional validation for clinical variant classification, (2) mechanistic dissection of the developmental (migration/lamination), synaptic (spine/excitability), and newly identified vascular (BBB) contributions to disease, and (3) preclinical drug screening (demonstrated for losartan in the Xenopus platform).

Sources: Lin et al. 2005, PNAS, PMID:16203979; Runge et al. 2021, Mol Psychiatry; Xenopus DEE72 CRISPant model, PMC11228833, 2024; MGI:107755; Sega et al. 2019

Summary Table: Key Ontology Term Suggestions

Category Term ID
Disease Developmental and epileptic encephalopathy 72 OMIM:618374
Gene NEUROD2 HGNC:7763 (verify current); NCBI Gene:4762
Protein Neurogenic differentiation factor 2 UniProt:Q15784
Phenotype Global developmental delay HP:0001263
Phenotype Infantile spasms HP:0011097
Phenotype Autistic behavior HP:0000729
Phenotype Hypsarrhythmia HP:0002373
GO Process Central nervous system neuron differentiation GO:0021953
GO Function RNA polymerase II transcription factor activity GO:0000981
Cell type Glutamatergic neuron CL:0000679
Anatomy Neocortex UBERON:0001950
Anatomy Basolateral amygdaloid nucleus UBERON:0002884
Treatment Pharmacotherapy NCIT:C15986
Treatment Dietary intervention (ketogenic diet) NCIT:C15447

Notes on Evidence Gaps

  • No MONDO ID was directly confirmable for this specific entry in this search session (the disease is very recently described; a MONDO cross-reference likely exists via the OMIM #618374 mapping but was not directly located).
  • Formal gnomAD constraint metrics (pLI/LOEUF) specific to NEUROD2 were not located in this search.
  • Precise HGNC numeric ID (7761 vs. 7763) should be confirmed directly against the current HGNC database before curation, as sources were inconsistent.
  • No dedicated GeneReviews chapter was identified for this condition, consistent with its recent (2019+) description and small case count.

Sources (consolidated): - OMIM #618374 — DEE72 - OMIM *601725 — NEUROD2 - Sega et al. 2019, J Med Genet, PMID:30323019 - Runge et al. 2021, Mol Psychiatry, PMID:34667263 / commentary PMC8988728 - Guerin/Rots et al. 2021, Am J Med Genet A, PMID:33438828 / PMC8212414 - Xenopus DEE72 CRISPant/losartan model, PMC11228833 - BMC Neurology, vigabatrin + prednisolone case, 2022 - Neonatal-onset NEUROD2 case report, Exploration Pub, 2024 - Lin et al. 2005, PNAS, PMID:16203979 - BMC Genomics 2015, NEUROD2 target analysis - Frontiers 2021, Neurod gene family review - GeneCards NEUROD2 - UniProt Q15784 - MGI:107755

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