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Classifications

Harrison's Part

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Inheritance

1

Autosomal dominant, almost always de novo HP:0000006

Heterozygous DLG4 loss-of-function variants act in a dominant, dosage-sensitive manner; the other DLG-MAGUK paralogs (DLG1/SAP97, DLG2/PSD-93, DLG3/SAP102) do not compensate for the missing PSD-95 allele.

Autosomal dominant inheritance Expressivity: VARIABLE De novo rate: The great majority of pathogenic DLG4 variants arise de novo; in the founding 53-patient cohort the majority of the 45 distinct variants occurred de novo, with four of unknown origin. Rare transmission from a heterozygous or mosaic parent is documented, and paternal germline mosaicism has now been confirmed molecularly in sperm DNA.

Show evidence (3 references)

PMID:37347881 SUPPORT Human Clinical

"DLG4-related synaptopathy is an autosomal dominant disorder typically caused by a de novo pathogenic variant."

GeneReviews states the inheritance pattern and the predominance of de novo origin.

PMID:37347881 SUPPORT Human Clinical

"Rarely, individuals diagnosed with DLG4-related synaptopathy inherited a DLG4 pathogenic variant from a heterozygous or mosaic parent."

Documents the rare inherited and parental-mosaic route, which sets the recurrence risk counseling.

PMID:42482343 SUPPORT Human Clinical

"The variant was present at 3.83% variant allele frequency in paternal sperm, establishing paternal germline mosaicism as the origin."

First molecular confirmation of parental germline mosaicism in this disorder, quantifying a previously inferred recurrence mechanism.

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Discussions and Knowledge Gaps

3

The mechanistic literature that defines PSD-95 function — the shifted LTP/LTD frequency-response, the AMPA-receptor and silent-synapse phenotype, the autism-relevant behavioural profile — comes almost entirely from homozygous Dlg4-null or PSD-95-truncating mice, whereas every affected human is heterozygous. Does halving PSD-95 dose produce a proportionate, qualitatively similar synaptic phenotype, or does the near-complete loss studied in mice engage compensations and failure modes that a haploinsufficient synapse never reaches?

HUMAN MODEL MISMATCH OPEN hmm_homozygous_null_vs_human_haploinsufficiency

Attached to

pathophysiology#Impaired Glutamate Receptor Anchoring at the Postsynaptic Density pathophysiology#Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance

The gap is not hypothetical. Homozygous Dlg4 deletion adversely affects survival in mice, so the null phenotype is measured in a survivor-selected population with no human counterpart, and the complete knockout leaves a substantial subpopulation of synapses unaffected, implying a threshold rather than a linear dose-response. The one heterozygous patient-allele model published to date does reproduce reduced PSD-95 protein and cognitive and sleep phenotypes, but showed no spontaneous seizures despite epilepsy affecting about half of affected humans — the clearest signal so far that the heterozygous state is not simply a milder null.

Proposed experiments

Side-by-side heterozygous versus homozygous Dlg4 synaptic physiology

dlg4_het_vs_null_synaptic_physiology

Measure LTP/LTD frequency-response functions, AMPA/NMDA ratio and silent-synapse fraction in Dlg4+/- and Dlg4-/- hippocampus on one genetic background, to establish whether the half-dose state is a proportionate version of the null or a qualitatively different phenotype.

Decision criterion

A monotonic, proportionate shift across genotypes would support extrapolating null-mouse mechanism to human haploinsufficiency; a threshold effect, with Dlg4+/- indistinguishable from wild type, would refute it.

Synaptic PSD-95 and AMPA-receptor content in patient iPSC-derived neurons

dlg4_ipsc_neuron_synaptic_content

Quantify PSD-95 protein per synapse and synaptic AMPA-receptor content in neurons differentiated from the patient-derived AOUMEYi004-A iPSC line against an isogenic corrected control, moving the receptor-anchoring claim into human cells at the correct heterozygous dose.

Provoked-seizure threshold in the Dlg4 V692Wfs*12/+ knock-in

dlg4_knockin_provoked_seizure_threshold

Test chemically or electrically provoked seizure susceptibility in the heterozygous patient-allele knock-in, since spontaneous seizures were absent but the seizure threshold was never probed.

Decision criterion

A lowered provoked-seizure threshold would reconcile the model with the ~50% human epilepsy frequency; a normal threshold would sharpen the mismatch.

Show evidence (2 references)

PMID:17148601 SUPPORT Model Organism

"We also observed that a significant population of synapses appeared unaffected by PSD-95 gene deletion, suggesting that the functional role of PSD-95 displays synapse-specificity."

Even complete PSD-95 deletion spares many synapses, so extrapolating a null phenotype to a half-dose state is not straightforward.

PMID:42565830 SUPPORT Model Organism

"While spontaneous seizures were not observed, future studies will test susceptibility to provoked seizures."

The genotype-faithful heterozygous model misses the epilepsy arm, the concrete instance of the mismatch.

Why do individuals carrying the same DLG4 variant differ so widely in severity, from mild intellectual disability without epilepsy to a regressive DEE-SWAS course? What determines whether a given individual develops sleep-activated epileptiform encephalopathy?

KNOWLEDGE GAP OPEN gap_dlg4_genotype_phenotype

Attached to

pathophysiology#Sleep-Activated Epileptiform Encephalopathy (DEE-SWAS/ESES) pathophysiology#Developmental Regression pathophysiology#Neurodevelopmental Phenotypic Output

The largest epilepsy-focused cohort could not identify a genotype-phenotype relationship even between individuals carrying identical DLG4 variants, which rules out variant identity as the explanation and points instead to modifier genes, developmental timing or stochastic circuit factors. Because DEE-SWAS is the single strongest predictor of regression, predicting who will develop it is the question with the most direct clinical consequence in this disorder.

Proposed experiments

Prospective longitudinal sleep-EEG cohort in DLG4 variant carriers

dlg4_prospective_sleep_eeg_cohort

Follow an unselected cohort of DLG4 variant carriers with serial sleep or 24-hour EEG to establish the incidence, age window and clinical predictors of DEE-SWAS onset, which no retrospective series can supply.

Decision criterion

Identification of a reproducible pre-DEE-SWAS EEG or clinical signature would make the regression risk predictable and the surveillance interval evidence-based.

Modifier screen in PSD-95 interaction partners

dlg4_psd95_partner_modifier_screen

Test whether variation in PSD-95 binding partners already implicated in epilepsy (LGI1-ADAM22, KCNA1/KCNA2, GRIN2A/GRIN2B) modifies the epilepsy phenotype among DLG4 carriers, the leading candidate explanation for within-variant phenotypic divergence.

Show evidence (1 reference)

PMID:38135915 SUPPORT Human Clinical

"We could not identify a clear genotype-phenotype relationship even between individuals with the same DLG4 variants."

Directly states the unexplained variability that defines this gap.

Every clinically advanced PSD-95-directed drug programme is designed to *disrupt* a PSD-95 interaction — nerinetide (Tat-NR2B9c) and the small-molecule PSD-95/nNOS disruptors developed for ischaemic stroke and neuropathic pain. For a haploinsufficiency disorder the required direction is the opposite: restore PSD-95 dose or function. Is there any tractable route to that — transcriptional upregulation of the remaining allele, targeted augmentation of a paralogous MAGUK, or stabilization of the residual protein — and in what developmental window would it have to act?

KNOWLEDGE GAP OPEN gap_no_disease_modifying_strategy

Attached to

pathophysiology#DLG4 Loss of Function and PSD-95 Haploinsufficiency pathophysiology#Impaired Functional Maturation of Excitatory Synapses

The existence of a mature PSD-95-directed pharmacology is easy to mistake for a therapeutic head start for this disorder, and it is not one: those agents deliberately uncouple PSD-95 from nNOS to suppress excitotoxic nitric oxide, which in a PSD-95-deficient brain would push the lesion further in the direction it is already broken. The window question is equally unresolved — PSD-95 is described as essential during synaptogenesis and neurodevelopment, so a dose-restoring therapy started after that window may have nothing left to rescue, and no natural-history data yet define when the window closes.

Proposed experiments

Conditional postnatal restoration of PSD-95 dose in a heterozygous model

dlg4_postnatal_restoration_window

Restore PSD-95 expression at a series of postnatal ages in Dlg4+/- or Dlg4 V692Wfs*12/+ mice and test which synaptic, cognitive and sleep phenotypes remain reversible at each age.

Decision criterion

Reversibility of a phenotype after the close of synaptogenesis would make dose-restoring therapy worth pursuing beyond infancy; strict developmental-window dependence would restrict it to a prenatal or early-infantile intervention.

Show evidence (3 references)

PMID:40712457 SUPPORT Other

"Collectively, the evidence positions PSD-95/nNOS disruption as a versatile, clinically achievable approach for mitigating excitotoxic and nociceptive pathology and sets the stage for first-in-class therapies that uncouple toxic NO signaling without silencing healthy synapses."

Establishes that the mature PSD-95-directed pharmacology is aimed at disrupting a PSD-95 interaction for excitotoxicity and pain — the opposite direction from what a PSD-95 haploinsufficiency disorder needs.

PMID:29169997 SUPPORT Other

"In this review, we describe the role of PSD-95 as an essential scaffolding protein during synaptogenesis and neurodevelopment."

Supports the developmental-window concern that motivates the second half of this gap.

PMID:37347881 SUPPORT Human Clinical

"There is no cure for DLG4-related synaptopathy."

Confirms that no disease-modifying option currently exists, which is what makes this an open gap rather than a settled question.

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Pathophysiology

8

DLG4 Loss of Function and PSD-95 Haploinsufficiency

A heterozygous protein-truncating variant (nonsense, frameshift, canonical splice-site) — or a synonymous, deep-intronic or missense variant that disrupts splicing or protein folding — halves the functional dose of PSD-95, the prototypic MAGUK scaffold of the excitatory postsynaptic density. The endpoint that is actually measured is reduced PSD-95 protein; the route to it is allele-dependent and should not be assumed. Truncating alleles in the body of the transcript are conventionally expected to be cleared by nonsense-mediated decay, but the one DLG4 allele for which this has been tested directly — the GK-domain frameshift V692Wfs*12 — escapes decay and still yields less protein, so degradation of the transcript is not a prerequisite for haploinsufficiency here. Any surviving protein product lacks one or more of the PDZ, SH3 and guanylate-kinase domains through which PSD-95 organizes the postsynaptic density. Because the paralogous DLG-MAGUKs do not compensate, the single remaining wild-type allele is insufficient; DLG4's position among the most loss-of-function-intolerant genes in the genome is the population-genetic footprint of that fact, not its cause.

Glutamatergic neuron CL:0000679

Genetic context DLG4 hgnc:2903 allele_type: SNV variant_origin: DE_NOVO zygosity: HETEROZYGOUS functional_impact_category: LOSS_OF_FUNCTION

Heterozygous, predominantly de novo loss-of-function alleles; six missense variants in the founding cohort localize to conserved PDZ2, PDZ3 and GK domains and are predicted to destabilize the domain or alter its surface charge rather than to abolish a canonical PDZ binding pocket.

Synapse assembly GO:0007416 ↓ DECREASED Glutamate receptor signaling pathway GO:0007215 ↓ DECREASED

PSD-95 scaffolding of the postsynaptic density GO:0098919 ↓ DECREASED

Postsynaptic density GO:0014069

Experimental models

AOUMEYi004-A patient-derived iPSC line (DLG4 c.2155A>T p.Arg719*) IPSC DERIVED MODEL Carries a patient heterozygous nonsense DLG4 allele in a human genetic background, the substrate required to measure the haploinsufficient state in human neurons.

Animal models

Dlg4 V692Wfs*12 heterozygous knock-in mouse (patient-derived SHINE allele) Mouse recapitulates Heterozygous patient allele producing reduced PSD-95 protein — the same genetic state and the same molecular endpoint as the human disorder.

Downstream

Impaired Glutamate Receptor Anchoring at the Postsynaptic Density Reduced PSD-95 dose lowers the scaffold's capacity to cluster and retain ionotropic glutamate receptors and their auxiliary subunits.

Show evidence (4 references)

PMID:33597769 SUPPORT Human Clinical

"Of the 45 different DLG4 variants, 39 were predicted to lead to loss of protein function and the majority occurred de novo (four with unknown origin)."

Establishes loss of function as the dominant variant class and de novo occurrence as the rule.

PMID:35457207 SUPPORT Other

"Majority of the DLG4 variants are predicted to lead to haploinsufficiency of PSD-95 resulting in a brain disorder, which suggests that the other members of the DLG subfamily are unable to compensate for PSD-95, as could have been expected."

States the haploinsufficiency mechanism and the failure of paralog compensation that makes a single lost allele pathogenic. evidence_source OTHER: this is a narrative review's synthesis, not a primary measurement.

PMID:29460436 SUPPORT In Vitro

"Gene expression studies supported their pathogenicity through haploinsufficiency and loss-of-function."

Expression studies in the original discovery families directly support haploinsufficiency rather than a dominant-negative effect.

+ 1 more reference

Impaired Glutamate Receptor Anchoring at the Postsynaptic Density

PSD-95 clusters in postsynaptic nanodomains where its PDZ1-2 supermodule binds the C-terminal PDZ-binding motifs of NMDA-receptor GluN2 subunits and of TARP/stargazin, the auxiliary subunit that tethers AMPA receptors, while PDZ3 binds neuroligin-1 and the LGI1-ADAM22 complex. Losing PSD-95 dose fragments the postsynaptic density, reduces its size, and destabilizes AMPA receptors at the synaptic membrane, increasing the proportion of "silent" synapses that carry NMDA receptors but no functional AMPA receptors. The NMDA-receptor current is not simply lost but qualitatively altered, decaying more slowly with a greater GluN2B contribution — a shift toward an immature receptor complement.

Cortical and hippocampal pyramidal neuron CL:0000598

AMPA receptor clustering at the postsynaptic density GO:0097113 ↓ DECREASED NMDA receptor clustering at the postsynaptic density GO:0097114 ↓ DECREASED Regulation of postsynaptic receptor levels GO:0099072 ↓ DECREASED Postsynaptic density assembly GO:0097107 ↓ DECREASED

Dendritic spine GO:0043197

Animal models

PSD-95 complete knockout mouse - AMPA receptor and silent synapses Mouse recapitulates Establishes that PSD-95 loss reduces AMPA-receptor-mediated transmission and slows NMDA-receptor current decay through a greater GluN2B contribution.

PSD-95 PDZ1/PDZ2 ligand-binding-deficient knock-in mouse Mouse recapitulates Disabling PDZ1/2 ligand binding alone depletes PSD-95, PSD-93 and AMPA receptor subunits from the hippocampal postsynaptic density fraction.

Downstream

Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance A destabilized receptor complement changes the rules and the set point of activity-dependent plasticity at glutamatergic synapses.

Impaired Functional Maturation of Excitatory Synapses The same scaffold deficit leaves excitatory synapses structurally and functionally immature during the period of synaptogenesis.

Show evidence (7 references)

PMID:35457207 SUPPORT Other

"This is in line with the observation that knockdown of PSD-95 leads to a fragmentation of the PSD."

Statement that losing PSD-95 degrades the structural integrity of the postsynaptic density. evidence_source OTHER rather than IN_VITRO: the cited publication is a review reporting another group's knockdown result, not a paper presenting in-vitro data of its own.

PMID:17148601 SUPPORT Model Organism

"We found that the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)subtype of glutamate receptor (AMPAR)-mediated synaptic transmission was reduced in these mice."

Complete PSD-95 knockout reduces AMPA-receptor-mediated transmission, the core receptor-anchoring deficit.

PMID:17148601 SUPPORT Model Organism

"In addition, we report that the decay of NMDAR-mediated current was slower in KO mice: The contribution of NR2B subunit containing receptors to the NMDAR-mediated synaptic current was greater in KO mice."

Shows the NMDA-receptor subunit complement shifts toward GluN2B when PSD-95 is absent, an anchoring rather than a purely quantitative defect.

+ 4 more references

Impaired Functional Maturation of Excitatory Synapses

PSD-95 level is instructive, not merely permissive, for excitatory synapse maturation: raising it drives glutamatergic synapses to maturity, enhances presynaptic terminal maturation transsynaptically, and increases the number and size of dendritic spines. Halving it therefore leaves a developing cortex with fewer functionally mature excitatory synapses during the window of synaptogenesis. The maturation failure is functional and is explicitly dissociated from spine morphology, which is the single most important caveat on this node. In the complete knockout the functionally silent synapses sit on morphologically mature spines, and PSD-95 mutant mice show unaffected synaptic morphology — so this entry deliberately does not assert a dendritic-spine-development deficit, and a negative spine-imaging result in a DLG4 model or patient neuron would not count against the node.

Cortical and hippocampal pyramidal neuron CL:0000598

Synapse assembly GO:0007416 ↓ DECREASED Glutamate receptor signaling pathway GO:0007215 ↓ DECREASED

Downstream

Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance An immature excitatory synapse population cannot support normal activity-dependent plasticity.

Show evidence (6 references)

PMID:11082065 SUPPORT In Vitro

"We found that overexpression of PSD-95 in hippocampal neurons can drive maturation of glutamatergic synapses."

Establishes PSD-95 dose as instructive for excitatory synapse maturation. Note the direction: this is a gain-of-dose experiment, so it constrains the dose-response relationship rather than measuring the haploinsufficient state.

PMID:17148601 SUPPORT Model Organism

"In addition, we report that the decay of NMDAR-mediated current was slower in KO mice: The contribution of NR2B subunit containing receptors to the NMDAR-mediated synaptic current was greater in KO mice."

Loss-of-function direction: the receptor complement shifts toward the GluN2B-dominated configuration characteristic of immature synapses, which is what "functional immaturity" means here.

PMID:29169997 SUPPORT Other

"In this review, we describe the role of PSD-95 as an essential scaffolding protein during synaptogenesis and neurodevelopment."

Frames PSD-95 as essential specifically during synaptogenesis and neurodevelopment, the developmental window in which the haploinsufficiency acts; evidence_source OTHER because this is a narrative review.

+ 3 more references

Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance

PSD-95 couples the NMDA receptor to the machinery that decides whether a given firing pattern potentiates or depresses a synapse. Without it, the frequency-response function of NMDA-dependent long-term potentiation and depression is shifted, producing strikingly enhanced LTP across stimulation frequencies rather than a simple loss of plasticity — a bidirectional learning rule broken in the direction of over-potentiation. The excitation-inhibition framing is an inference rather than a measurement in this disorder: the studies cited here quantified glutamatergic transmission and plasticity only, and none of them measured GABAergic transmission alongside it. PSD-95 is confined to excitatory synapses, so a shifted set point is the expected consequence, but a comparable inhibitory deficit has not been excluded.

Glutamatergic neuron CL:0000679

Long-term synaptic potentiation GO:0060291 ↕ DYSREGULATED Regulation of synaptic plasticity GO:0048167 ↕ DYSREGULATED Glutamatergic synaptic transmission GO:0035249 ↓ DECREASED

Animal models

PSD-95 mutant mouse - bidirectional plasticity and spatial learning Mouse recapitulates Demonstrates that losing PSD-95 breaks the bidirectional plasticity rule and impairs learning, the mechanistic core of the human cognitive phenotype.

Downstream

Cortical Network Dysfunction and Hyperexcitability Synapse-level plasticity failure and a shifted E/I set point aggregate into abnormal cortical circuit assembly and network excitability.

Show evidence (3 references)

PMID:9853749 SUPPORT Model Organism

"In mutant mice lacking PSD-95, the frequency function of NMDA-dependent LTP and LTD is shifted to produce strikingly enhanced LTP at different frequencies of synaptic stimulation."

The defining plasticity phenotype of PSD-95 loss — a shifted bidirectional learning rule, not simply absent plasticity.

PMID:9853749 SUPPORT Model Organism

"PSD-95 thus appears to be important in coupling the NMDA receptor to pathways that control bidirectional synaptic plasticity and learning."

States the mechanistic role of PSD-95 as the coupler between NMDA receptor and plasticity machinery.

PMID:23268962 SUPPORT Model Organism

"In the hippocampal CA1 region of young KI mice, basal synaptic efficacy was reduced and long-term potentiation (LTP) was enhanced with intact long-term depression."

Independently reproduces the paradoxical pattern — reduced basal excitatory efficacy with enhanced LTP — in a PDZ1/2 ligand-binding-deficient knock-in, showing it follows from lost receptor anchoring rather than from the particular null allele.

Cortical Network Dysfunction and Hyperexcitability

Aggregated synaptic deficits produce diffuse, bilateral cortical and hippocampal circuit dysfunction. Structural imaging is deliberately unhelpful here: brain MRI in individuals with pathogenic DLG4 variants shows abnormalities that are diverse and nonspecific, so the circuit lesion is functional rather than a visible malformation. In roughly half of individuals the shifted excitation-inhibition set point crosses into frank epileptogenesis, with a wide range of seizure types of which focal seizures are the most common.

Cortical and hippocampal pyramidal neuron CL:0000598

Chemical synaptic transmission GO:0007268 ↕ DYSREGULATED

Neocortex UBERON:0001950 Hippocampal formation UBERON:0002421

Animal models

Dlg4 V692Wfs*12 heterozygous knock-in mouse (patient-derived SHINE allele) Mouse fails to recapitulate No spontaneous seizures were observed in the heterozygous knock-in, despite epilepsy affecting about half of individuals with the human disorder.

Downstream

Sleep-Activated Epileptiform Encephalopathy (DEE-SWAS/ESES) In a subgroup, cortical hyperexcitability becomes sleep-potentiated and crosses into a continuous spike-wave encephalopathy.

Developmental Regression Regression also occurs in individuals who never develop ESES/DEE-SWAS, so circuit dysfunction has a route to skill loss that does not pass through the sleep-activated state.

Neurodevelopmental Phenotypic Output Diffuse cortical circuit dysfunction manifests as the core cognitive, behavioural and motor phenotype.

Show evidence (2 references)

PMID:38135915 SUPPORT Human Clinical

"A large variety of seizure types was reported, although focal seizures were the most common."

Characterizes the epileptic output of the circuit lesion in the largest epilepsy-focused cohort.

PMID:35457207 SUPPORT Human Clinical

"Brain magnetic resonance imaging (MRI) of the individuals with pathogenic DLG4 variants revealed that the structural brain abnormalities were diverse and nonspecific."

Supports framing the circuit lesion as functional rather than a discrete structural malformation.

Sleep-Activated Epileptiform Encephalopathy (DEE-SWAS/ESES)

In about a quarter of individuals with DLG4-related epilepsy, epileptiform activity is massively potentiated by slow-wave sleep, producing encephalopathy related to status epilepticus during slow-wave sleep (ESES) / developmental epileptic encephalopathy with spike-wave activation during sleep (DEE-SWAS). This is a distinct circuit state, not merely more seizures: the abnormality is near-continuous sleep-activated spike-wave, and because the driving activity occurs in sleep it is invisible to a routine awake EEG. Sleep or 24-hour EEG is therefore the specific investigation this node motivates.

Chemical synaptic transmission GO:0007268 ↕ DYSREGULATED

Downstream

Developmental Regression Sleep-activated epileptiform encephalopathy drives loss of previously acquired verbal and motor skills; regression was observed in every individual with ESES/DEE-SWAS.

Show evidence (2 references)

PMID:38135915 SUPPORT Human Clinical

"Encephalopathy related to status epilepticus during slow-wave sleep (ESES)/developmental epileptic encephalopathy with spike-wave activation during sleep (DEE-SWAS) was diagnosed in >25% of the individuals."

Quantifies the DEE-SWAS/ESES subgroup within the DLG4 epilepsy cohort.

PMID:38135915 SUPPORT Human Clinical

"Occurrence of ESES/DEE-SWAS in DLG4-related synaptopathy requires proper investigation with sleep EEG."

Supports the sleep-EEG surveillance implication that follows from the sleep-activated mechanism.

Developmental Regression

Loss of previously acquired verbal and/or motor skills, which converts an otherwise largely static developmental disorder into an actively regressive one and is the strongest determinant of cognitive outcome. This node is deliberately separate from the sleep-activated encephalopathy that most often drives it, because the evidence decouples them in both directions: regression occurred in every individual with ESES/DEE-SWAS but also in some who never developed it, so it has a second route from cortical circuit dysfunction that does not pass through the sleep-activated state. Regression is also not confined to childhood — intellectual regression without motor delay has been reported at age two, and cognitive regression with progressive dystonia in adulthood.

Downstream

Neurodevelopmental Phenotypic Output Active regression subtracts from the developmental trajectory, worsening the cognitive and language outcome.

Show evidence (2 references)

PMID:38135915 SUPPORT Human Clinical

"Regression in verbal and/or motor domains was observed in all individuals who suffered from ESES/DEE-SWAS, as well as some who did not."

The sentence that both establishes the coupling to DEE-SWAS and shows it is not exclusive — the reason these are two nodes rather than one.

PMID:37347881 SUPPORT Human Clinical

"Regression in motor development and/or language has been reported in about 40% of affected individuals."

Quantifies regression across the disorder as a whole, not only within the epilepsy subgroup.

Neurodevelopmental Phenotypic Output

The clinical convergence point of the synaptopathy: early-onset global developmental delay, intellectual disability that is most often mild to moderate, autism spectrum disorder and attention deficit-hyperactivity disorder, together with hypotonia, movement disorders and sleep disturbance. The overlap with other synaptic-dysfunction neurodevelopmental disorders is what motivated the "synaptopathy" designation in the first place, and is why the clinical gestalt alone cannot establish the diagnosis.

Glutamatergic neuron CL:0000679

Animal models

Dlg4 V692Wfs*12 heterozygous knock-in mouse (patient-derived SHINE allele) Mouse partially recapitulates Reproduces learning and cognitive-flexibility deficits and a fragmented sleep architecture reminiscent of the patient, with trends toward altered sensory processing and socialization.

Dlg4 null (PSD-95 knockout) mouse - autism-relevant behaviour Mouse partially recapitulates Produces a behavioural profile spanning the autism-relevant, motor and anxiety domains seen in the human disorder.

PSD-95 PDZ1/PDZ2 ligand-binding-deficient knock-in mouse Mouse partially recapitulates Produces abnormal anxiety-like behaviour and impaired spatial reference, working and remote memory — the cognitive and anxiety domains of the human phenotype.

Show evidence (2 references)

PMID:33597769 SUPPORT Human Clinical

"The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder."

States the core clinical output of the mechanism in the founding cohort.

PMID:33597769 SUPPORT Human Clinical

"The present study shows that clinical manifestations associated with DLG4 overlap with those found in other neurodevelopmental disorders of synaptic dysfunction; thus, we designate this group of disorders as DLG4-related synaptopathy."

Supports the framing of the phenotypic output as a shared synaptopathy convergence point.

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Pathograph

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

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Phenotypes

32

Digestive 1

Vomiting HP:0002013

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Vomiting is observed in a number of individuals and can be triggered by seizures, motion sickness, or fatigue."

GeneReviews reports vomiting and its triggers; the phrasing "a number of individuals" is not quantitative, so no frequency band is asserted.

Eye 3

Strabismus HP:0000486

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Strabismus is the most common ocular finding followed by hyperopia, nystagmus, and cortical blindness."

Identifies strabismus as the leading ophthalmologic manifestation.

Hypermetropia HP:0000540

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Strabismus is the most common ocular finding followed by hyperopia, nystagmus, and cortical blindness."

Ranks hyperopia second among ocular findings.

Nystagmus HP:0000639

Show evidence (2 references)

PMID:37347881 SUPPORT Human Clinical

"Strabismus is the most common ocular finding followed by hyperopia, nystagmus, and cortical blindness."

Lists nystagmus among the ocular findings.

PMID:29460436 SUPPORT Human Clinical

"Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

Independent report of nystagmus in the original DLG4 discovery series.

Head and Neck 2

High palate HP:0000218

Show evidence (1 reference)

PMID:29460436 SUPPORT Human Clinical

"Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

High-arched palate is listed among the marfanoid features in the discovery series. PARTIAL: three patients from a marfanoid-selected cohort.

Long face HP:0000276

Show evidence (1 reference)

PMID:29460436 SUPPORT Human Clinical

"Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

Long face is listed among the marfanoid features in the discovery series. PARTIAL: three patients from a marfanoid-selected cohort, and the unselected cohort could not establish a distinct facial dysmorphism.

Limbs 1

Arachnodactyly HP:0001166

Show evidence (1 reference)

PMID:29460436 SUPPORT Human Clinical

"Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

Long and thin fingers, i.e. arachnodactyly, are listed among the marfanoid features. PARTIAL: three patients from a marfanoid-selected cohort.

Musculoskeletal 4

Hypotonia HP:0001252

Show evidence (2 references)

PMID:38135915 SUPPORT Human Clinical

"The major clinical features are developmental delay, intellectual disability (ID), hypotonia, sleep disturbances, movement disorders, and epilepsy."

Hypotonia is listed among the major clinical features of the disorder.

PMID:37347881 SUPPORT Human Clinical

"Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."

GeneReviews lists hypotonia among the neurologic findings.

Joint hypermobility FREQUENT HP:0001382

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Joint laxity is a relatively common finding (36.9%), and scoliosis is noted in 20% of individuals."

The 36.9% figure falls in the FREQUENT band (30-79%).

Scoliosis OCCASIONAL HP:0002650

Show evidence (2 references)

PMID:37347881 SUPPORT Human Clinical

"Joint laxity is a relatively common finding (36.9%), and scoliosis is noted in 20% of individuals."

The 20% figure falls in the OCCASIONAL band (5-29%).

PMID:29460436 SUPPORT Human Clinical

"Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

Scoliosis was part of the original marfanoid presentation through which DLG4 was discovered. PARTIAL because that series was selected for marfanoid habitus, so it cannot speak to how often scoliosis occurs in unselected DLG4 patients; the frequency band above rests on GeneReviews.

Pectus excavatum HP:0000767

Show evidence (1 reference)

PMID:29460436 SUPPORT Human Clinical

"Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

Pectus excavatum is listed among the marfanoid features in the discovery series. PARTIAL: three patients from a marfanoid-selected cohort.

Nervous System 17

Intellectual disability HP:0001249

Show evidence (2 references)

PMID:37347881 SUPPORT Human Clinical

"DLG4-related synaptopathy is characterized by developmental delay, intellectual disability (most commonly in the mild-to-moderate range), and autism spectrum disorder."

GeneReviews names intellectual disability as a defining feature and gives its typical severity range.

PMID:29460436 SUPPORT Human Clinical

"Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

The original discovery series independently reports mild-to-moderate intellectual disability.

Global developmental delay HP:0001263

Show evidence (2 references)

PMID:33597769 SUPPORT Human Clinical

"The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder."

Global developmental delay heads the list of predominant features in the founding cohort.

PMID:38135915 SUPPORT Human Clinical

"All but one individual presented with neurodevelopmental delay."

Near-universal neurodevelopmental delay in the independent epilepsy-focused cohort.

Delayed speech and language development HP:0000750

Show evidence (1 reference)

PMID:38135915 SUPPORT Human Clinical

"Regression in verbal and/or motor domains was observed in all individuals who suffered from ESES/DEE-SWAS, as well as some who did not."

Supports verbal-domain involvement, but describes loss of acquired language rather than the initial delay, so the evidence is indirect for the delay itself.

Developmental regression FREQUENT HP:0002376

Show evidence (3 references)

PMID:37347881 SUPPORT Human Clinical

"Regression in motor development and/or language has been reported in about 40% of affected individuals."

Quantifies regression at ~40%, which maps to the FREQUENT band (30-79%).

PMID:42551111 SUPPORT Human Clinical

"We report a 34-year-old male with childhood developmental delay, severe intellectual disability in adulthood, episodes of agitation with a previous diagnosis of schizoaffective disorder and adult-onset cognitive regression who developed progressive generalised dystonia due to a de novo DLG4..."

Documents that regression is not confined to childhood, extending the temporal window of this phenotype.

PMID:38182567 SUPPORT Human Clinical

"Intellectual regression without motor delay was observed at 2 years of age, and she was diagnosed with autism spectrum disorder and attention-deficit/hyperactivity disorder."

Shows regression can present in the intellectual domain alone, as early as age two and without accompanying motor delay, widening the presentation this phenotype can take.

Autism spectrum disorder HP:0000717

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"DLG4-related synaptopathy is characterized by developmental delay, intellectual disability (most commonly in the mild-to-moderate range), and autism spectrum disorder."

GeneReviews includes autism spectrum disorder in the defining clinical characterization.

Attention deficit hyperactivity disorder HP:0007018

Show evidence (1 reference)

PMID:33597769 SUPPORT Human Clinical

"The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder."

ADHD is named as one of the four predominant features of the disorder.

Epilepsy FREQUENT Seizure HP:0001250

Show evidence (2 references)

PMID:37347881 SUPPORT Human Clinical

"About half of affected individuals have epilepsy."

GeneReviews gives the epilepsy frequency as about half, mapping to FREQUENT (30-79%).

PMID:38135915 SUPPORT Human Clinical

"Even though epilepsy is present in 50% of the individuals, it has not been investigated in detail."

Restates the 50% figure from the prior literature as background. It is not an independent measurement: this cohort was ascertained on having both a DLG4 variant and epilepsy, so epilepsy frequency within it is 100% by construction. The FREQUENT band rests on the GeneReviews statement above.

Focal-onset seizure HP:0007359

Show evidence (1 reference)

PMID:38135915 SUPPORT Human Clinical

"A large variety of seizure types was reported, although focal seizures were the most common."

Directly identifies focal seizures as the predominant seizure type.

Ataxia HP:0001251

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."

Names ataxia as one of the two most common movement-disorder features.

Dystonia HP:0001332

Course: PROGRESSIVE

Show evidence (2 references)

PMID:37347881 SUPPORT Human Clinical

"Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."

GeneReviews lists dystonia among the neurologic findings.

PMID:42551111 SUPPORT Human Clinical

"This case expands the phenotypic spectrum of recognised movement disorder manifestations associated with DLG4-related synaptopathy."

Documents progressive generalised adult-onset dystonia as an extension of the movement-disorder spectrum.

Tremor HP:0001337

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."

GeneReviews lists tremor among the neurologic findings.

Migraine HP:0002076

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."

GeneReviews lists migraine headaches among the neurologic findings.

Sleep disturbance FREQUENT HP:0002360

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Sleep disturbance is common, with sleep onset and/or sleep maintenance difficulties being frequently reported."

GeneReviews describes sleep disturbance as "common" and "frequently reported", the qualitative-term pattern that maps to FREQUENT.

Anxiety HP:0000739

Show evidence (2 references)

PMID:37347881 SUPPORT Human Clinical

"At each visit after infancy, assess for behavioral issues such as anxiety, autism spectrum disorder, attention-deficit/hyperactivity disorder, aggression, or self-injury."

GeneReviews names anxiety among the behavioural issues requiring ongoing surveillance in this disorder. No frequency band is asserted, since the surveillance sentence is not quantitative.

PMID:23268962 SUPPORT Model Organism

"In a battery of behavioral tests, KI mice showed markedly abnormal anxiety-like behavior, impaired spatial reference and working memory, and impaired remote memory and pattern separation in fear conditioning test."

Model-organism corroboration: the PDZ1/2 ligand-binding-deficient knock-in shows an anxiety-like phenotype, matching the human behavioural feature.

Aggressive behavior HP:0000718

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"At each visit after infancy, assess for behavioral issues such as anxiety, autism spectrum disorder, attention-deficit/hyperactivity disorder, aggression, or self-injury."

GeneReviews names aggression among the behavioural issues requiring ongoing surveillance. Not quantitative, so no frequency band is asserted.

Self-injurious behavior HP:0100716

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"At each visit after infancy, assess for behavioral issues such as anxiety, autism spectrum disorder, attention-deficit/hyperactivity disorder, aggression, or self-injury."

GeneReviews names self-injury among the behavioural issues requiring ongoing surveillance. Not quantitative, so no frequency band is asserted.

Psychosis OCCASIONAL HP:0000709

Show evidence (1 reference)

PMID:37386468 SUPPORT Human Clinical

"Additionally, while psychosis is not considered a cardinal feature of SHINE syndrome, 10% of the 53 documented cases had reported psychosis"

Quantifies psychosis at 10% of published cases, which maps to the OCCASIONAL band (5-29%).

Growth 1

Marfanoid habitus OCCASIONAL Disproportionate tall stature HP:0001519

Show evidence (2 references)

PMID:33597769 SUPPORT Human Clinical

"Marfanoid habitus, which was previously suggested to be a characteristic feature of DLG4-related phenotypes, was found in only nine individuals and despite some overlapping features, a distinct facial dysmorphism could not be established."

Confirms marfanoid habitus occurs but explicitly downgrades it from a characteristic feature, so this both supports the phenotype and refutes its earlier diagnostic weight. The OCCASIONAL band is derived rather than quoted: nine individuals out of the 53 in this cohort is 17%, within the 5-29% band (derived-count pattern, docs/frequency-evidence-guidelines.md).

PMID:29460436 SUPPORT Human Clinical

"Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

The original discovery series describing the marfanoid presentation in detail. PARTIAL because the cohort was selected for marfanoid habitus, so it establishes the phenotype's existence but not its prevalence.

Other 3

Developmental and epileptic encephalopathy with spike-wave activation in sleep Continuous spike and waves during slow sleep HP:0031491

Show evidence (1 reference)

PMID:38135915 SUPPORT Human Clinical

"Our study shows that a subgroup of individuals with DLG4-related synaptopathy have DEE, and approximately one fourth of them have ESES/DEE-SWAS."

Establishes DEE-SWAS/ESES as part of the phenotypic spectrum and quantifies the subgroup.

Motor stereotypy HP:0000733

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."

Names stereotypies as one of the two most common movement-disorder features.

Cerebral visual impairment HP:0100704

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Strabismus is the most common ocular finding followed by hyperopia, nystagmus, and cortical blindness."

Lists cortical blindness last among the ocular findings.

🧬

Genetic Associations

1

DLG4

Gene: DLG4 hgnc:2903 relationship_type: CAUSATIVE variant_origin: DE_NOVO

Show evidence (3 references)

PMID:33597769 SUPPORT Human Clinical

"Postsynaptic density protein-95 (PSD-95), encoded by DLG4, regulates excitatory synaptic function in the brain."

Establishes the gene-protein relationship and the protein's synaptic role.

PMID:29460436 SUPPORT Human Clinical

"Only DLG4 gene met these criteria."

In the exome study of 64 marfanoid-habitus intellectual-disability probands, DLG4 was the single gene meeting the recurrent-truncating-variant discovery criteria, establishing the gene-disease link.

PMID:35457207 SUPPORT Human Clinical

"Only six missense variants, all localizing to the highly conserved functional domains of PSD-95, have been reported."

Characterizes the missense minority and its localization to conserved domains.

🔬

Variants

2

DLG4 c.2105+235C>T (deep intronic, pseudoexon-activating) Pathogenic

Gene: DLG4 hgnc:2903 SNV

A deep intronic variant identified by whole genome sequencing that generates two alternative DLG4 transcripts, one containing a pseudoexon; both are out-of-frame and predicted to truncate the protein. Notable because it is invisible to exome sequencing and because DLG4 mRNA proved detectable in peripheral blood, making an accessible-tissue RNA assay diagnostic.

Show evidence (1 reference)

PMID:37525972 SUPPORT Human Clinical

"Both alternative transcripts are out-of-frame and predicted to result in protein-truncation, thereby establishing the genetic diagnosis for the proband."

Establishes the pathogenic splice-disrupting consequence of the deep intronic variant.

DLG4 c.771G>A p.(Ala257=) (synonymous, exon 9 skipping) Pathogenic

Gene: DLG4 hgnc:2903 SNV

A synonymous variant with previously conflicting ClinVar interpretations, shown by RNA sequencing and RT-PCR to cause complete exon 9 skipping with a resulting frameshift and premature termination codon. Its origin was paternal germline mosaicism, detected by high-depth amplicon sequencing of sperm DNA.

Show evidence (1 reference)

PMID:42482343 SUPPORT Human Clinical

"The synonymous DLG4 c.771G>A variant (absent in gnomAD) induced complete exon 9 skipping, resulting in a frameshift and premature termination codon."

Functional RNA evidence resolving a synonymous variant as loss-of-function.

💊

Medical Actions

6

Supportive and symptom-directed care

Action: Supportive care Ontology label: Supportive Care NCIT:C15747

There is no cure and no disease-modifying therapy. Management is entirely supportive: standard treatment of developmental delay and intellectual disability, epilepsy, migraine, ataxia, dystonia, refractive error, strabismus and cerebral visual impairment, delivered through a multidisciplinary surveillance-and-support model.

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"There is no cure for DLG4-related synaptopathy. Supportive care includes standard treatment for developmental delay / intellectual disability, epilepsy, migraine, ataxia, dystonia, refractive errors, strabismus, and cerebral visual impairment."

GeneReviews management statement, the basis for the supportive-care-only framing.

Antiseizure medication

Action: Pharmacotherapy NCIT:C15986

Agent: anticonvulsant agent NCIT:C264

Standard antiseizure pharmacotherapy tailored to seizure type. No DLG4-specific regimen has been established, and the epilepsy cohort study assessed medication response only retrospectively and by referring-clinician report, so drug-choice guidance rests on general epilepsy practice rather than on evidence specific to this gene.

Mechanism Target:

INHIBITS Cortical Network Dysfunction and Hyperexcitability — Antiseizure medication suppresses the network hyperexcitability that generates seizures; it does not act on the upstream PSD-95 deficit.

Show evidence (2 references)

PMID:37347881 SUPPORT Human Clinical

"There is no cure for DLG4-related synaptopathy. Supportive care includes standard treatment for developmental delay / intellectual disability, epilepsy, migraine, ataxia, dystonia, refractive errors, strabismus, and cerebral visual impairment."

GeneReviews states that epilepsy in this disorder is managed with standard epilepsy treatment — the management recommendation this treatment entry records.

PMID:38135915 SUPPORT Human Clinical

"Antiseizure medication response was retrospectively assessed by the referring clinician."

Kept only as the caveat it is: this is a Methods sentence, not a finding, and it is here to make explicit that the largest cohort's medication-response data are retrospective and clinician-reported, so no agent-specific claim can rest on them.

Clozapine for treatment-resistant psychosis

Action: Pharmacotherapy NCIT:C15986

Agent: clozapine CHEBI:3766

In a reported adolescent with DLG4-related synaptopathy and early-onset, treatment-resistant schizophrenia with catatonia, clozapine produced substantial improvement in positive and negative symptoms after three other antipsychotics had failed. This is a single case report and is not a treatment recommendation for the disorder.

Target Phenotypes: Psychosis HP:0000709

Show evidence (1 reference)

PMID:37386468 SUPPORT Human Clinical

"After failing three antipsychotic drug treatments, the patient was started on clozapine, which resulted in significant improvements in positive and negative symptoms."

Single-patient evidence for clozapine responsiveness; graded PARTIAL because an uncontrolled n-of-1 observation cannot establish efficacy in the disorder.

Behavioural therapy and pharmacotherapy for sleep disturbance

Action: Sleep disorder therapy Ontology label: Sleep Disorder Therapy NCIT:C15541

Behavioural measures are first-line for insomnia, with pharmacotherapy reserved for refractory sleep disturbance.

Target Phenotypes: Sleep disturbance HP:0002360

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"Behavioral therapy may aid those who have insomnia, while pharmacotherapy may be considered in those who have refractory sleep disturbance."

GeneReviews sets out the stepped approach to sleep disturbance.

Developmental, physical and speech therapy

Action: Rehabilitation NCIT:C15315

Early intervention and ongoing developmental, physical, occupational and speech therapies form the core of management for the developmental delay and intellectual disability, alongside monitoring of mobility and self-help skills.

Target Phenotypes: Global developmental delay HP:0001263

Show evidence (1 reference)

PMID:37347881 SUPPORT Human Clinical

"At each visit, monitor those with seizures; assess for new manifestations such as seizures, changes in tone, movement disorders, and migraine headaches; monitor developmental progress and educational needs; assess mobility and self-help skills; and assess for signs/symptoms of sleep disturbance."

GeneReviews surveillance recommendation covering developmental progress, educational needs and mobility, the domains these therapies address.

Genetic counseling

Action: Genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Counseling covers the autosomal dominant, predominantly de novo mechanism; the low-but-not-zero sibling recurrence risk from parental germline mosaicism, now molecularly confirmed in at least one family; and the availability of prenatal and preimplantation genetic testing once the familial variant is known.

Show evidence (2 references)

PMID:37347881 SUPPORT Human Clinical

"However, once a DLG4 pathogenic variant has been identified in an affected family member, prenatal and preimplantation genetic testing are possible."

GeneReviews genetic-counseling statement on reproductive testing options.

PMID:42482343 SUPPORT Human Clinical

"These findings underscore the dual necessity of functional analysis for synonymous variants and sensitive mosaicism detection for accurate genetic counseling."

Supports mosaicism testing as a component of recurrence-risk counseling in this disorder.

🔬

Diagnosis

2

Molecular genetic testing for a heterozygous DLG4 pathogenic variant (PRESENT)

The diagnosis is genotype-first. The clinical picture overlaps other synaptopathies too closely to be diagnostic on its own, so a multigene intellectual-disability/epilepsy panel or exome/genome sequencing is the appropriate test. RNA studies should be considered for synonymous, missense or intronic variants of uncertain splicing consequence, and DLG4 mRNA is detectable in peripheral blood, so an accessible-tissue assay is feasible.

Show evidence (3 references)

PMID:37347881 SUPPORT Human Clinical

"The diagnosis of DLG4-related synaptopathy is established in a proband with suggestive clinical findings and a heterozygous pathogenic variant in DLG4 identified by molecular genetic testing."

GeneReviews states the diagnostic criterion.

PMID:37525972 SUPPORT Human Clinical

"By using reverse-transcription PCR on RNA derived from peripheral blood, we demonstrate that DLG4 mRNA expression is detectable in blood and the deep intronic variant gives rise to two alternative DLG4 transcripts, one of which includes a pseudoexon."

Supports blood RNA testing as a practical route for resolving splice-uncertain DLG4 variants.

PMID:40444229 SUPPORT Human Clinical

"Fourteen years after the initial presentation, additional genetic testing revealed a de-novo mutation in the DLG4 gene, confirming a diagnosis of SHINE syndrome."

Illustrates the long diagnostic delay that follows from the non-specific clinical gestalt, and the reason genotype-first testing is recommended rather than waiting for a recognizable phenotype.

Sleep or 24-hour EEG (PRESENT)

Because the DEE-SWAS/ESES pattern is activated by slow-wave sleep, a routine awake EEG can miss it. Sleep or 24-hour EEG is indicated in individuals with significant cognitive or behavioural delay, developmental regression, or an abnormal routine EEG.

Show evidence (2 references)

PMID:38135915 SUPPORT Human Clinical

"Occurrence of ESES/DEE-SWAS in DLG4-related synaptopathy requires proper investigation with sleep EEG."

States the sleep-EEG requirement that follows from the sleep-activated mechanism.

PMID:37347881 SUPPORT Human Clinical

"Annually or as clinically indicated, ophthalmology evaluation; and 24-hour EEG in those with significant cognitive/behavioral delay, developmental regression, or abnormal routine EEG."

GeneReviews surveillance recommendation specifying when 24-hour EEG is indicated.

🩻

Imaging Findings

1

Nonspecific structural brain abnormality on MRI

Brain MRI is part of the diagnostic work-up of developmental delay in this disorder but is not diagnostic of it: the structural abnormalities reported across the cohort are diverse and nonspecific, consistent with a functional synaptic lesion rather than a recognizable malformation. Awake and sleep EEG carry the diagnostic weight instead.

Mri Bilateral

Show evidence (2 references)

PMID:35457207 SUPPORT Human Clinical

"Brain magnetic resonance imaging (MRI) of the individuals with pathogenic DLG4 variants revealed that the structural brain abnormalities were diverse and nonspecific."

States that MRI findings in this disorder are heterogeneous and lack a specific pattern.

PMID:38135915 SUPPORT Human Clinical

"Data on awake and sleep electroencephalography (EEG) and/or video-polygraphy and brain magnetic resonance imaging were collected."

Confirms MRI is routinely collected in this population alongside awake and sleep EEG.

📈

Progression

3

Infancy and early childhood

Age: First years of life

Presentation is with early-onset global developmental delay; the disorder is recognized through the developmental trajectory rather than through any congenital malformation, and neither the facial gestalt nor brain MRI is specific enough to prompt the diagnosis at this stage.

Show evidence (1 reference)

PMID:33597769 SUPPORT Human Clinical

"The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder."

Establishes early onset of the global developmental delay that opens the course.

Childhood - epilepsy and the regression window

Age: Childhood, with epilepsy onset typically in mid-childhood

About half of individuals develop epilepsy, and a subgroup develop the sleep-activated DEE-SWAS/ESES pattern. This is the critical window: verbal and/or motor regression occurs in every individual who develops ESES/DEE-SWAS and in some who do not, so an otherwise static developmental disorder becomes actively regressive here. Regression can present in the intellectual domain alone, as early as age two.

Show evidence (2 references)

PMID:38135915 SUPPORT Human Clinical

"Regression in verbal and/or motor domains was observed in all individuals who suffered from ESES/DEE-SWAS, as well as some who did not."

Defines the regression window and its tight coupling to the sleep-activated encephalopathy.

PMID:38182567 SUPPORT Human Clinical

"Intellectual regression without motor delay was observed at 2 years of age, and she was diagnosed with autism spectrum disorder and attention-deficit/hyperactivity disorder."

Documents how early, and how selectively, the regression can present.

Adulthood

Age: Adulthood

Survival into adulthood is documented and the disorder is not known to shorten life expectancy, but the adult phenotype is poorly characterized because genetic testing was historically not offered to adults — diagnoses made fourteen years after presentation are on record. Late cognitive regression and progressive generalised dystonia have both been reported in adults, so the course is not reliably static after childhood.

Show evidence (2 references)

PMID:42551111 SUPPORT Human Clinical

"We report a 34-year-old male with childhood developmental delay, severe intellectual disability in adulthood, episodes of agitation with a previous diagnosis of schizoaffective disorder and adult-onset cognitive regression who developed progressive generalised dystonia due to a de novo DLG4..."

Documents an adult-onset regressive and dystonic course, the evidence against assuming a static adult phase.

PMID:40444229 SUPPORT Human Clinical

"Fourteen years after the initial presentation, additional genetic testing revealed a de-novo mutation in the DLG4 gene, confirming a diagnosis of SHINE syndrome."

Documents the diagnostic delay that leaves the older phenotype under-ascertained.

📊

Prevalence

1

Worldwide, individuals ascertained by exome or genome sequencing

Cases In Literature Ultra Rare

No population-based prevalence study exists. The founding cohort assembled 53 individuals through GeneMatcher; a later multicenter epilepsy-focused series added 35 individuals with a DLG4 variant and epilepsy. Case counts, not a denominator-based rate.

Show evidence (2 references)

PMID:33597769 SUPPORT Human Clinical

"Here we present the clinical and genetic features of 53 patients (42 previously unpublished) with DLG4 variants."

Establishes the size of the founding published cohort, the basis for describing the disorder as ultra-rare.

PMID:38135915 SUPPORT Human Clinical

"We included 35 individuals with a DLG4 variant and epilepsy as part of a multicenter study."

The later multicenter epilepsy series, the second-largest published case collection.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from DLG4-Related Synaptopathy:

Marfan syndrome and other syndromic intellectual disability with marfanoid habitus

Overlapping Features DLG4 was discovered through a marfanoid-habitus-plus-intellectual-disability cohort, a clinically and genetically heterogeneous group of overlapping disorders.

Distinguishing Features

Marfanoid habitus was found in only nine of 53 individuals in the founding DLG4 cohort and no distinct facial dysmorphism could be established, so a marfanoid presentation neither confirms nor excludes DLG4.

Show evidence (1 reference)

PMID:29460436 SUPPORT Human Clinical

"Marfanoid habitus (MH) combined with intellectual disability (ID) is a genetically and clinically heterogeneous group of overlapping disorders."

States the heterogeneity of the differential group in which DLG4 was found.

🧫

Experimental Models

1

AOUMEYi004-A patient-derived iPSC line (DLG4 c.2155A>T p.Arg719*) IPSC_DERIVED_MODEL

Induced pluripotent stem cell line derived from a 37-year-old man with DLG4-related synaptopathy carrying a novel heterozygous de novo nonsense variant. The line has a normal karyotype, expresses pluripotency markers and differentiates into all three germ layers. It provides the first published human cellular substrate for modeling this disorder; no neuronal differentiation or disease phenotype is reported yet.

Organism

human NCBITaxon:9606

Publication

PMID:42462545

Pathograph links

DLG4 Loss of Function and PSD-95 Haploinsufficiency measures fidelity: unknown Carries a patient heterozygous nonsense DLG4 allele in a human genetic background, the substrate required to measure the haploinsufficient state in human neurons.

Limitations: Characterized only at the pluripotent stage — karyotype, pluripotency markers and trilineage differentiation. No neuronal derivative, no PSD-95 protein measurement and no synaptic phenotype has been reported, so the line does not yet demonstrate any disease mechanism.

Show evidence (1 reference)

PMID:42462545 SUPPORT In Vitro

"We established the diagnosis in a 37-year-old man, by whole exome sequencing, heterozygous for the novel variant c.2155A > T; p.(Arg719*), then generated and characterized the iPSC line derived from the patient in order to model the neurodevelopmental disorder."

Establishes the line's genotype and stated purpose; graded PARTIAL because the report characterizes the stem cell line, not a disease mechanism.

🐁

Animal Models

5

Dlg4 V692Wfs*12 heterozygous knock-in mouse (patient-derived SHINE allele)

The genetically most faithful model available: a heterozygous knock-in of a patient frameshift allele associated with severe disease. The mutant transcript escapes nonsense-mediated decay yet still yields reduced PSD-95 protein, reproducing the patient's molecular phenotype rather than a clean null. Behavioural phenotypes are partly sex-specific.

Species

Mouse

Genotype

Dlg4 V692Wfs*12/+ (patient-derived frameshift allele)

Publication

PMID:42565830

Pathograph links

DLG4 Loss of Function and PSD-95 Haploinsufficiency recapitulates fidelity: high Heterozygous patient allele producing reduced PSD-95 protein — the same genetic state and the same molecular endpoint as the human disorder.

Limitations: Models one specific severe frameshift allele; whether an allele that is degraded by nonsense-mediated decay behaves identically is untested.

Readouts

PSD-95 protein abundance

Direction: DECREASED

Interpretation: Reduced PSD-95 protein confirms the haploinsufficient molecular state.

Show evidence (1 reference)

PMID:42565830 SUPPORT Model Organism

"The mutant transcript escapes nonsense-mediated decay but results in reduced PSD-95 protein expression, faithfully reproducing the molecular phenotype observed in the patient."

Reports the reduced PSD-95 protein measurement in the knock-in.

Show evidence (1 reference)

PMID:42565830 SUPPORT Model Organism

"Here, we developed and characterized a mouse model of SHINE syndrome carrying the patient-derived DLG4V692Wfs*12/+ variant associated with a severe form of the disorder."

Establishes the model as a heterozygous patient-allele knock-in, matching the human genetic state.

Neurodevelopmental Phenotypic Output partially recapitulates fidelity: moderate Reproduces learning and cognitive-flexibility deficits and a fragmented sleep architecture reminiscent of the patient, with trends toward altered sensory processing and socialization.

Limitations: Several phenotypes appeared only in male mutants, and the social and sensory findings were trends rather than established effects. Spontaneous seizures were not observed, so the epilepsy arm of the human phenotype is not captured.

Readouts

Learning and cognitive flexibility

Direction: DECREASED

Interpretation: Behavioural correlate of the intellectual-disability phenotype, in male mutants.

Show evidence (1 reference)

PMID:42565830 SUPPORT Model Organism

"Male mutants showed deficits in learning and cognitive flexibility."

Reports the cognitive readout and its sex specificity.

Sleep bout architecture

Direction: ALTERED

Interpretation: Fragmented sleep, the model correlate of the human sleep-disturbance phenotype.

Show evidence (1 reference)

PMID:42565830 SUPPORT Model Organism

"Male mutants exhibited an increased proportion of short sleep bouts and compensatory longer average sleep bout length, suggesting sporadic sleep reminiscent of the patient."

Reports the sleep-architecture measurement in the model.

Show evidence (1 reference)

PMID:42565830 SUPPORT Model Organism

"Dlg4V692Wfs*12/+ mice also demonstrate trends toward altered sensory processing and socialization."

Supports the model as informative for the behavioural phenotype while showing the sensory and social arms are trends, not established effects.

Cortical Network Dysfunction and Hyperexcitability fails to recapitulate fidelity: low No spontaneous seizures were observed in the heterozygous knock-in, despite epilepsy affecting about half of individuals with the human disorder.

Limitations: Provoked-seizure susceptibility was not tested, so this is a negative result for spontaneous seizures only and does not exclude a latent lowered seizure threshold.

Show evidence (1 reference)

PMID:42565830 REFUTE Model Organism

"While spontaneous seizures were not observed, future studies will test susceptibility to provoked seizures."

Explicit negative result for the epilepsy arm in the most genotype-faithful model, and the authors' own statement that the provoked-seizure question remains open.

Dlg4 null (PSD-95 knockout) mouse - autism-relevant behaviour

Complete PSD-95 null mouse phenotyped across repetitive, social, motor and anxiety-related behavioural domains, with dendritic-spine and forebrain synaptic-gene-expression correlates.

Species

Mouse

Genotype

Dlg4-/- (complete PSD-95 knockout), C57BL/6J congenic

Publication

PMID:20952458

Pathograph links

Neurodevelopmental Phenotypic Output partially recapitulates fidelity: moderate Produces a behavioural profile spanning the autism-relevant, motor and anxiety domains seen in the human disorder.

Limitations: Homozygous null, so it models complete PSD-95 absence rather than the human heterozygous haploinsufficient state; homozygous deletion also adversely affected survival, imposing a survivor-selection bias absent from the human condition.

Show evidence (1 reference)

PMID:20952458 SUPPORT Model Organism

"These findings demonstrate that DLG4 gene disruption in mice produces a complex range of behavioral and molecular abnormalities relevant to autism spectrum disorders and Williams' syndrome."

Establishes the null mouse as informative for the behavioural output of DLG4 disruption.

PSD-95 mutant mouse - bidirectional plasticity and spatial learning

The classic PSD-95 mutant used to define the plasticity phenotype: the NMDA-dependent LTP/LTD frequency-response is shifted toward enhanced LTP, with severely impaired spatial learning and intact synaptic NMDA-receptor currents, subunit expression, localization and synaptic morphology.

Species

Mouse

Genotype

PSD-95 mutant (guanylate kinase domain-truncating)

Publication

PMID:9853749

Pathograph links

Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance recapitulates fidelity: moderate Demonstrates that losing PSD-95 breaks the bidirectional plasticity rule and impairs learning, the mechanistic core of the human cognitive phenotype.

Limitations: This line expresses a truncated PSD-95 rather than being a complete null, and it is homozygous, so it does not model human heterozygous haploinsufficiency. Learning was assayed as rodent spatial learning, a distant proxy for human intellectual disability.

Readouts

NMDA-dependent LTP/LTD frequency-response function

Direction: ALTERED

Interpretation: The plasticity set point is shifted toward potentiation rather than plasticity being lost.

Show evidence (1 reference)

PMID:9853749 SUPPORT Model Organism

"In mutant mice lacking PSD-95, the frequency function of NMDA-dependent LTP and LTD is shifted to produce strikingly enhanced LTP at different frequencies of synaptic stimulation."

The electrophysiological measurement behind the plasticity node.

Spatial learning

Direction: DECREASED

Interpretation: Behavioural consequence of the shifted plasticity rule.

Show evidence (1 reference)

PMID:9853749 SUPPORT Model Organism

"In keeping with neural-network models that incorporate bidirectional learning rules, this frequency shift is accompanied by severely impaired spatial learning."

Reports the learning deficit that accompanies the plasticity shift.

Show evidence (1 reference)

PMID:9853749 SUPPORT Model Organism

"PSD-95 thus appears to be important in coupling the NMDA receptor to pathways that control bidirectional synaptic plasticity and learning."

The authors' own statement of what the model establishes about PSD-95 function.

PSD-95 complete knockout mouse - AMPA receptor and silent synapses

A complete PSD-95 null generated specifically to avoid the residual functional truncated protein of earlier lines; used to define the AMPA-receptor and silent-synapse phenotype in hippocampal CA1.

Species

Mouse

Genotype

PSD-95-/- (PDZ1-2 deletion, out-of-frame transcript)

Publication

PMID:17148601

Pathograph links

Impaired Glutamate Receptor Anchoring at the Postsynaptic Density recapitulates fidelity: moderate Establishes that PSD-95 loss reduces AMPA-receptor-mediated transmission and slows NMDA-receptor current decay through a greater GluN2B contribution.

Limitations: Homozygous null rather than heterozygous; the authors also found a substantial population of synapses unaffected by the deletion, so the receptor-anchoring deficit is synapse-specific rather than global.

Readouts

AMPA receptor-mediated synaptic transmission

Direction: DECREASED

Interpretation: Direct electrophysiological measure of failed AMPA-receptor anchoring.

Show evidence (1 reference)

PMID:17148601 SUPPORT Model Organism

"We found that the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)subtype of glutamate receptor (AMPAR)-mediated synaptic transmission was reduced in these mice."

The AMPA-receptor transmission measurement in the complete knockout.

Show evidence (1 reference)

PMID:17148601 SUPPORT Model Organism

"Together, these results suggest a synapse-specific role for PSD-95 in controlling synaptic function that is independent of spine morphology."

The authors' summary, which both supports the model's relevance to receptor anchoring and flags that the effect is synapse-specific.

PSD-95 PDZ1/PDZ2 ligand-binding-deficient knock-in mouse

A domain-specific model that leaves PSD-95 present but unable to bind ligands through PDZ1/PDZ2 — the supermodule that docks NMDA-receptor GluN2 subunits and TARP-coupled AMPA receptors. It therefore isolates the receptor-anchoring function from PSD-95 abundance, and is the closest available model for the minority of human missense alleles that fall in the PDZ domains.

Species

Mouse

Genotype

PSD-95 PDZ1/PDZ2 ligand binding-deficient cDNA knock-in (homozygous)

Publication

PMID:23268962

Pathograph links

Impaired Glutamate Receptor Anchoring at the Postsynaptic Density recapitulates fidelity: moderate Disabling PDZ1/2 ligand binding alone depletes PSD-95, PSD-93 and AMPA receptor subunits from the hippocampal postsynaptic density fraction.

Limitations: Homozygous, and models a ligand-binding defect rather than the reduced protein dose that most human alleles produce; the effect was also age- and subregion-dependent, so a single developmental snapshot can mislead.

Readouts

PSD-fraction accumulation of PSD-95, PSD-93 and AMPA receptor subunits

Direction: DECREASED

Interpretation: Biochemical measure of failed scaffold-dependent receptor anchoring.

Show evidence (1 reference)

PMID:23268962 SUPPORT Model Organism

"The KI mice showed decreased accumulation of mutant PSD-95, PSD-93 and AMPA receptor subunits in the PSD fraction of the hippocampus."

Reports the biochemical anchoring measurement in the knock-in.

Show evidence (1 reference)

PMID:23268962 SUPPORT Model Organism

"These findings reveal that PSD-95 including its ligand binding of the PDZ1/2 domains controls the synaptic clustering of PSD-MAGUKs and AMPA receptors, which may have an essential role in regulating hippocampal synaptic transmission, plasticity, and hippocampus-dependent behavior."

The authors' statement of what the model establishes about PSD-95-dependent receptor clustering.

Neurodevelopmental Phenotypic Output partially recapitulates fidelity: moderate Produces abnormal anxiety-like behaviour and impaired spatial reference, working and remote memory — the cognitive and anxiety domains of the human phenotype.

Limitations: Rodent memory tasks are a distant proxy for human intellectual disability, and the model captures neither epilepsy nor the connective-tissue features.

Readouts

Spatial reference, working and remote memory

Direction: DECREASED

Interpretation: Cognitive correlate of the intellectual-disability phenotype.

Show evidence (1 reference)

PMID:23268962 SUPPORT Model Organism

"In a battery of behavioral tests, KI mice showed markedly abnormal anxiety-like behavior, impaired spatial reference and working memory, and impaired remote memory and pattern separation in fear conditioning test."

Reports the behavioural battery results in the knock-in.

Show evidence (1 reference)

PMID:23268962 SUPPORT Model Organism

"In a battery of behavioral tests, KI mice showed markedly abnormal anxiety-like behavior, impaired spatial reference and working memory, and impaired remote memory and pattern separation in fear conditioning test."

Supports treating this model as informative for the cognitive and anxiety output of PSD-95 dysfunction.

{ }

Source YAML

click to show

name: DLG4-Related Synaptopathy
creation_date: "2026-08-19T00:00:00Z"
category: Mendelian
synonyms:
- intellectual developmental disorder 62
- intellectual developmental disorder, autosomal dominant 62
- MRD62
- IDDA62
- SHINE syndrome
- DLG4 synaptopathy
- PSD-95 haploinsufficiency
- intellectual disability with marfanoid features
description: >
  DLG4-related synaptopathy is a rare autosomal dominant neurodevelopmental
  disorder caused by heterozygous, almost always de novo, loss-of-function
  variants in DLG4, the gene encoding postsynaptic density protein 95 (PSD-95).
  PSD-95 is the prototypic and most abundant membrane-associated guanylate
  kinase (MAGUK) scaffold of the excitatory postsynaptic density, where its
  three PDZ domains plus SH3 and guanylate-kinase-like domains organize NMDA
  receptors, TARP/stargazin-coupled AMPA receptors, Kv1 channels, neuroligins
  and the LGI1-ADAM22 complex into transsynaptic nanocolumns. Reduced PSD-95
  dosage degrades that scaffold, impairs glutamate-receptor anchoring and
  activity-dependent synaptic plasticity, and yields a neurodevelopmental
  phenotype dominated by global developmental delay, intellectual disability
  (most often mild to moderate), autism spectrum disorder and ADHD, with
  epilepsy in about half of individuals.

  The condition is indexed in OMIM as 618793 "intellectual developmental
  disorder, autosomal dominant 62" (MRD62) and in MONDO as MONDO:0032919
  "intellectual developmental disorder 62" — serial-numbered labels that carry
  no mechanistic information. This entry uses
  the gene-anchored clinical name "DLG4-related synaptopathy" coined by
  Rodríguez-Palmero et al. (2021) — the name used by the GeneReviews chapter and
  by the subsequent literature — and retains the OMIM/MONDO label plus the
  patient-community acronym SHINE (Sleep disturbances, Hypotonia, Intellectual
  disability, Neurologic disorder, Epilepsy) as synonyms.

  The clinically most consequential complication is a developmental and
  epileptic encephalopathy with spike-wave activation in sleep
  (DEE-SWAS/ESES), which affects roughly a quarter of the epilepsy subgroup and
  is tightly coupled to motor and language regression.
disease_term:
  preferred_term: DLG4-related synaptopathy
  description: >-
    Autosomal dominant synaptopathy caused by heterozygous loss-of-function
    variants in DLG4 (PSD-95); the OMIM/MONDO label is "intellectual
    developmental disorder 62" (MRD62).
  term:
    id: MONDO:0032919
    label: intellectual developmental disorder 62
parents:
- Neurodevelopmental Disorder
- Intellectual disability
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
references:
- reference: PMID:37347881
  title: DLG4-Related Synaptopathy.
  tags:
  - GeneReviews
- reference: PMID:33597769
  title: "DLG4-related synaptopathy: a new rare brain disorder."
- reference: PMID:38135915
  title: Developmental epileptic encephalopathy in DLG4-related synaptopathy.
- reference: PMID:35457207
  title: Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners.
notes: >-
  Deep research: an Edison/Falcon run was attempted first, per the default in the
  initiate-new-disorder-creation skill, but the API returned HTTP 402 (Payment
  Required — account credits exhausted), so no Falcon report exists for this
  entry. Two other providers were run instead and both were used:
  research/DLG4-Related_Synaptopathy-deep-research-claude_code.md and
  research/DLG4-Related_Synaptopathy-deep-research-openscientist.md.

  NEC preflight against MONDO:0032919 returned PASS for both reports (claude_code:
  DLG4 mentioned 61 times, next gene DLG2 at 4; openscientist: DLG4 52, next PSD
  7; both report OMIM 618793, matching the MONDO xref).

  The claude_code report's own reference-validation block flagged
  `needs_review: true` over three identifiers, each triaged separately rather
  than as a block. Two are not cited here: DOI:10.1111/cge.14411 (malformed by a
  pasted URL suffix) and DOI:10.1073/pnas.1517045112 (a quote the validator
  could not substantiate). The deep-intronic case the malformed DOI referred to
  is cited instead by its PMID (PMID:37525972), fetched and verified
  independently.

  The third, PMC:PMC3546964 / PMID:23342049 (Yudowski et al. 2013, acute PSD-95
  inactivation destabilizes AMPA receptors), was flagged `off_topic` and that
  flag was reviewed and deliberately overridden after reading the paper. Per
  CLAUDE.md an off-topic flag is evidence, not a verdict; the flag fires because
  the paper shares little vocabulary with a clinical DLG4 report, not because it
  is irrelevant. It is in fact the cleanest loss-of-function test of the
  receptor-anchoring claim in this entry — acute photoinactivation strips
  surface AMPA receptors within minutes while sparing NMDA and transferrin
  receptors — so it IS cited, on the Impaired Glutamate Receptor Anchoring node.

  The openscientist report validated clean (14/14 references resolved, no
  unsupported quotes, no off-topic flags).

  Two claims from the reports were checked and rejected. The claude_code report
  asserted that no human iPSC model of DLG4-related synaptopathy had been
  published — out of date, since PMID:42462545 reports the patient-derived
  AOUMEYi004-A line, curated here under experimental_models. The openscientist
  report stated that germline mosaicism is "not specifically documented" in this
  disorder — also out of date, since PMID:42482343 confirms paternal germline
  mosaicism at 3.83% allele frequency in sperm DNA, curated here under
  inheritance.

  Reference-cache scoping: several caches added in this change were fetched
  during the two deep-research reference-validation passes and are deliberately
  not cited. DOI:10.1111/cge.13243, DOI:10.1111/epi.17876 and
  DOI:10.1111/cge.14411 are DOI-keyed duplicates of PMID:29460436,
  PMID:38135915 and PMID:37525972 respectively, which are cited by PMID.
  DOI:10.1073/pnas.1517045112 is the PNAS MAGUK paper whose quote the
  claude_code report could not substantiate, and is not used. PMID:15638945 and
  PMID:8793296 (Drosophila dlg) are invertebrate background, and PMID:18248606
  and PMID:20554866 are PSD-95-interactome studies not specific to this
  disorder; the entry cites primary DLG4 and mammalian PSD-95 literature in
  their place. Note that PMID:23342049 is NOT in this unused set — despite its
  off-topic flag it is cited, for the reason given above.

  Datasets: `just discover-datasets DLG4-Related_Synaptopathy` returned 12
  candidates, all tagged DIRECT, and every one of them failed relevance triage —
  they matched on the generic phrase "intellectual developmental" and concern
  other genes entirely (ZMIZ1, HNRNPH2, KAT6A, UNC5C and others). This is the
  Named Entity Confusion failure mode reached through dataset search that
  CLAUDE.md warns about, so no `datasets:` block is curated here rather than
  recording an accession that resolves but is about a different disease. No
  DLG4- or PSD-95-specific repository accession surfaced.

  Two further items from the openscientist report are recorded in prose rather
  than as evidence because no citable snippet supports them: the gnomAD
  constraint metrics for DLG4 (pLI = 1.0, LOEUF = 0.14), which appear in the
  trigger-node description as "among the most loss-of-function-intolerant genes
  in the genome" without a reference; and a reported ~33% frequency of cerebellar
  vermis atrophy on MRI, which is not traceable to any source retrievable into
  the reference cache and is therefore omitted entirely rather than curated as an
  imaging finding.

  Frequency discipline: GeneReviews' full Clinical Characteristics tables report
  per-feature percentages that the cached PubMed abstract does not carry, so
  `frequency:` bands here are asserted only where the cached abstract (or the
  Kassabian epilepsy cohort abstract) is itself quantitative or uses an explicit
  frequency word, per docs/frequency-evidence-guidelines.md. Several features
  that the deep-research report gave percentages for (ASD 56%, ADHD 57%, anxiety
  53%, marfanoid habitus ~24%) are curated without a frequency band because those
  numbers trace to the GeneReviews chapter body rather than to any quotable
  cached source.
prevalence:
- population: Worldwide, individuals ascertained by exome or genome sequencing
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    No population-based prevalence study exists. The founding cohort assembled 53
    individuals through GeneMatcher; a later multicenter epilepsy-focused series
    added 35 individuals with a DLG4 variant and epilepsy. Case counts, not a
    denominator-based rate.
  evidence:
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we present the clinical and genetic features of 53 patients (42 previously unpublished) with DLG4 variants."
    explanation: Establishes the size of the founding published cohort, the basis for describing the disorder as ultra-rare.
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We included 35 individuals with a DLG4 variant and epilepsy as part of a multicenter study."
    explanation: The later multicenter epilepsy series, the second-largest published case collection.
progression:
- phase: Infancy and early childhood
  age_range: First years of life
  notes: >-
    Presentation is with early-onset global developmental delay; the disorder is
    recognized through the developmental trajectory rather than through any
    congenital malformation, and neither the facial gestalt nor brain MRI is
    specific enough to prompt the diagnosis at this stage.
  evidence:
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder."
    explanation: Establishes early onset of the global developmental delay that opens the course.
- phase: Childhood - epilepsy and the regression window
  age_range: Childhood, with epilepsy onset typically in mid-childhood
  notes: >-
    About half of individuals develop epilepsy, and a subgroup develop the
    sleep-activated DEE-SWAS/ESES pattern. This is the critical window: verbal
    and/or motor regression occurs in every individual who develops ESES/DEE-SWAS
    and in some who do not, so an otherwise static developmental disorder becomes
    actively regressive here. Regression can present in the intellectual domain
    alone, as early as age two.
  evidence:
  - reference: PMID:38135915
    reference_title: Developmental epileptic encephalopathy in DLG4-related synaptopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Regression in verbal and/or motor domains was observed in all individuals who suffered from ESES/DEE-SWAS, as well as some who did not."
    explanation: Defines the regression window and its tight coupling to the sleep-activated encephalopathy.
  - reference: PMID:38182567
    reference_title: "A novel DLG4 variant causes DLG4-related synaptopathy with intellectual regression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intellectual regression without motor delay was observed at 2 years of age, and she was diagnosed with autism spectrum disorder and attention-deficit/hyperactivity disorder."
    explanation: Documents how early, and how selectively, the regression can present.
- phase: Adulthood
  age_range: Adulthood
  notes: >-
    Survival into adulthood is documented and the disorder is not known to
    shorten life expectancy, but the adult phenotype is poorly characterized
    because genetic testing was historically not offered to adults — diagnoses
    made fourteen years after presentation are on record. Late cognitive
    regression and progressive generalised dystonia have both been reported in
    adults, so the course is not reliably static after childhood.
  evidence:
  - reference: PMID:42551111
    reference_title: "Intellectual disability, neuroregression and adult-onset progressive dystonia due to a DLG4 pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report a 34-year-old male with childhood developmental delay, severe intellectual disability in adulthood, episodes of agitation with a previous diagnosis of schizoaffective disorder and adult-onset cognitive regression who developed progressive generalised dystonia due to a de novo DLG4 pathogenic loss-of-function variant."
    explanation: Documents an adult-onset regressive and dystonic course, the evidence against assuming a static adult phase.
  - reference: PMID:40444229
    reference_title: "Late-onset diagnosis of SHINE syndrome in an adolescent with developmental delay: Case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fourteen years after the initial presentation, additional genetic testing revealed a de-novo mutation in the DLG4 gene, confirming a diagnosis of SHINE syndrome."
    explanation: Documents the diagnostic delay that leaves the older phenotype under-ascertained.
inheritance:
- name: Autosomal dominant, almost always de novo
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  expressivity: VARIABLE
  de_novo_rate: >-
    The great majority of pathogenic DLG4 variants arise de novo; in the founding
    53-patient cohort the majority of the 45 distinct variants occurred de novo,
    with four of unknown origin. Rare transmission from a heterozygous or mosaic
    parent is documented, and paternal germline mosaicism has now been confirmed
    molecularly in sperm DNA.
  description: >-
    Heterozygous DLG4 loss-of-function variants act in a dominant,
    dosage-sensitive manner; the other DLG-MAGUK paralogs (DLG1/SAP97,
    DLG2/PSD-93, DLG3/SAP102) do not compensate for the missing PSD-95 allele.
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "DLG4-related synaptopathy is an autosomal dominant disorder typically caused by a de novo pathogenic variant."
    explanation: GeneReviews states the inheritance pattern and the predominance of de novo origin.
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Rarely, individuals diagnosed with DLG4-related synaptopathy inherited a DLG4 pathogenic variant from a heterozygous or mosaic parent."
    explanation: Documents the rare inherited and parental-mosaic route, which sets the recurrence risk counseling.
  - reference: PMID:42482343
    reference_title: "A Synonymous DLG4 Variant (c.771G>A) Causes Exon 9 Skipping via Paternal Germline Mosaicism in DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The variant was present at 3.83% variant allele frequency in paternal sperm, establishing paternal germline mosaicism as the origin."
    explanation: First molecular confirmation of parental germline mosaicism in this disorder, quantifying a previously inferred recurrence mechanism.
pathophysiology:
- name: DLG4 Loss of Function and PSD-95 Haploinsufficiency
  biological_scale: MOLECULAR
  role: trigger
  conforms_to: "excitatory_synapse_scaffold_disruption#Postsynaptic Scaffold Disruption"
  description: >
    A heterozygous protein-truncating variant (nonsense, frameshift, canonical
    splice-site) — or a synonymous, deep-intronic or missense variant that
    disrupts splicing or protein folding — halves the functional dose of PSD-95,
    the prototypic MAGUK scaffold of the excitatory postsynaptic density. The
    endpoint that is actually measured is reduced PSD-95 protein; the route to it
    is allele-dependent and should not be assumed. Truncating alleles in the body
    of the transcript are conventionally expected to be cleared by
    nonsense-mediated decay, but the one DLG4 allele for which this has been
    tested directly — the GK-domain frameshift V692Wfs*12 — escapes decay and
    still yields less protein, so degradation of the transcript is not a
    prerequisite for haploinsufficiency here. Any surviving protein product lacks
    one or more of the PDZ, SH3 and guanylate-kinase domains through which PSD-95
    organizes the postsynaptic density. Because the paralogous DLG-MAGUKs do not
    compensate, the single remaining wild-type allele is insufficient; DLG4's
    position among the most loss-of-function-intolerant genes in the genome is the
    population-genetic footprint of that fact, not its cause.
  cell_types:
  - preferred_term: Glutamatergic neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  biological_processes:
  - preferred_term: Synapse assembly
    term:
      id: GO:0007416
      label: synapse assembly
    modifier: DECREASED
  - preferred_term: Glutamate receptor signaling pathway
    term:
      id: GO:0007215
      label: glutamate receptor signaling pathway
    modifier: DECREASED
  molecular_functions:
  - preferred_term: PSD-95 scaffolding of the postsynaptic density
    term:
      id: GO:0098919
      label: structural constituent of postsynaptic density
    modifier: DECREASED
  cellular_components:
  - preferred_term: Postsynaptic density
    term:
      id: GO:0014069
      label: postsynaptic density
  genetic_context:
    gene:
      preferred_term: DLG4
      term:
        id: hgnc:2903
        label: DLG4
    allele_type: SNV
    variant_origin: DE_NOVO
    zygosity: HETEROZYGOUS
    functional_impact_category: LOSS_OF_FUNCTION
    description: >-
      Heterozygous, predominantly de novo loss-of-function alleles; six missense
      variants in the founding cohort localize to conserved PDZ2, PDZ3 and GK
      domains and are predicted to destabilize the domain or alter its surface
      charge rather than to abolish a canonical PDZ binding pocket.
  evidence:
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of the 45 different DLG4 variants, 39 were predicted to lead to loss of protein function and the majority occurred de novo (four with unknown origin)."
    explanation: Establishes loss of function as the dominant variant class and de novo occurrence as the rule.
  - reference: PMID:35457207
    reference_title: "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Majority of the DLG4 variants are predicted to lead to haploinsufficiency of PSD-95 resulting in a brain disorder, which suggests that the other members of the DLG subfamily are unable to compensate for PSD-95, as could have been expected."
    explanation: >-
      States the haploinsufficiency mechanism and the failure of paralog
      compensation that makes a single lost allele pathogenic. evidence_source
      OTHER: this is a narrative review's synthesis, not a primary measurement.
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Gene expression studies supported their pathogenicity through haploinsufficiency and loss-of-function."
    explanation: Expression studies in the original discovery families directly support haploinsufficiency rather than a dominant-negative effect.
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "The six missense variants identified were suggested to lead to structural or functional changes by protein modeling studies."
    explanation: >-
      Supports the missense arm only indirectly — the structural consequence is
      inferred from molecular-dynamics modeling, not measured, so the
      loss-of-function assignment for missense alleles remains provisional.
  downstream:
  - target: Impaired Glutamate Receptor Anchoring at the Postsynaptic Density
    description: >-
      Reduced PSD-95 dose lowers the scaffold's capacity to cluster and retain
      ionotropic glutamate receptors and their auxiliary subunits.
    causal_link_type: DIRECT
- name: Impaired Glutamate Receptor Anchoring at the Postsynaptic Density
  biological_scale: MOLECULAR
  role: central_effector
  conforms_to: "excitatory_synapse_scaffold_disruption#Excitatory Postsynaptic Structural Deficit"
  description: >
    PSD-95 clusters in postsynaptic nanodomains where its PDZ1-2 supermodule
    binds the C-terminal PDZ-binding motifs of NMDA-receptor GluN2 subunits and
    of TARP/stargazin, the auxiliary subunit that tethers AMPA receptors, while
    PDZ3 binds neuroligin-1 and the LGI1-ADAM22 complex. Losing PSD-95 dose
    fragments the postsynaptic density, reduces its size, and destabilizes AMPA
    receptors at the synaptic membrane, increasing the proportion of "silent"
    synapses that carry NMDA receptors but no functional AMPA receptors. The
    NMDA-receptor current is not simply lost but qualitatively altered, decaying
    more slowly with a greater GluN2B contribution — a shift toward an immature
    receptor complement.
  cell_types:
  - preferred_term: Cortical and hippocampal pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  biological_processes:
  - preferred_term: AMPA receptor clustering at the postsynaptic density
    term:
      id: GO:0097113
      label: AMPA glutamate receptor clustering
    modifier: DECREASED
  - preferred_term: NMDA receptor clustering at the postsynaptic density
    term:
      id: GO:0097114
      label: NMDA glutamate receptor clustering
    modifier: DECREASED
  - preferred_term: Regulation of postsynaptic receptor levels
    term:
      id: GO:0099072
      label: regulation of postsynaptic membrane neurotransmitter receptor levels
    modifier: DECREASED
  - preferred_term: Postsynaptic density assembly
    term:
      id: GO:0097107
      label: postsynaptic density assembly
    modifier: DECREASED
  cellular_components:
  - preferred_term: Dendritic spine
    term:
      id: GO:0043197
      label: dendritic spine
  evidence:
  - reference: PMID:35457207
    reference_title: "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "This is in line with the observation that knockdown of PSD-95 leads to a fragmentation of the PSD."
    explanation: >-
      Statement that losing PSD-95 degrades the structural integrity of the
      postsynaptic density. evidence_source OTHER rather than IN_VITRO: the
      cited publication is a review reporting another group's knockdown result,
      not a paper presenting in-vitro data of its own.
  - reference: PMID:17148601
    reference_title: "Synapse-specific regulation of AMPA receptor function by PSD-95."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We found that the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)subtype of glutamate receptor (AMPAR)-mediated synaptic transmission was reduced in these mice."
    explanation: Complete PSD-95 knockout reduces AMPA-receptor-mediated transmission, the core receptor-anchoring deficit.
  - reference: PMID:17148601
    reference_title: "Synapse-specific regulation of AMPA receptor function by PSD-95."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In addition, we report that the decay of NMDAR-mediated current was slower in KO mice: The contribution of NR2B subunit containing receptors to the NMDAR-mediated synaptic current was greater in KO mice."
    explanation: Shows the NMDA-receptor subunit complement shifts toward GluN2B when PSD-95 is absent, an anchoring rather than a purely quantitative defect.
  - reference: PMID:11082065
    reference_title: "PSD-95 involvement in maturation of excitatory synapses."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "PSD-95 expression enhanced postsynaptic clustering and activity of glutamate receptors."
    explanation: The reciprocal gain-of-dose experiment establishes that PSD-95 level sets glutamate-receptor clustering at the synapse.
  - reference: PMID:29169997
    reference_title: "PSD95: A synaptic protein implicated in schizophrenia or autism?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Postsynaptic density protein-95 (PSD-95) is a major regulator of synaptic maturation by interacting, stabilizing and trafficking N-methyl-d-aspartic acid receptors (NMDARs) and α-amino-3-hydroxy-5-methyl-4-isox-azoleproprionic acid receptors (AMPARs) to the postsynaptic membrane."
    explanation: >-
      Review statement of the receptor stabilization and trafficking role that
      the haploinsufficient synapse loses; evidence_source OTHER because this is
      a narrative review rather than a primary study.
  - reference: PMID:23268962
    reference_title: "Impaired synaptic clustering of postsynaptic density proteins and altered signal transmission in hippocampal neurons, and disrupted learning behavior in PDZ1 and PDZ2 ligand binding-deficient PSD-95 knockin mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The KI mice showed decreased accumulation of mutant PSD-95, PSD-93 and AMPA receptor subunits in the PSD fraction of the hippocampus."
    explanation: >-
      A domain-specific knock-in shows that disabling only the PDZ1/2 ligand
      interaction is sufficient to strip AMPA-receptor subunits out of the
      postsynaptic density, isolating the anchoring function.
  - reference: PMID:23342049
    reference_title: "Acute inactivation of PSD-95 destabilizes AMPA receptors at hippocampal synapses."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Interestingly, acute inactivation of PSD-95 in rat hippocampal cultures rapidly reduced surface AMPA receptor immunostaining, but did not affected NMDA or transferrin receptor localization."
    explanation: >-
      The cleanest loss-of-function test of the anchoring claim: acutely
      destroying PSD-95 strips surface AMPA receptors within minutes while
      sparing NMDA and control receptors, so the deficit follows directly from
      losing the scaffold rather than from developmental compensation.
  downstream:
  - target: Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance
    description: >-
      A destabilized receptor complement changes the rules and the set point of
      activity-dependent plasticity at glutamatergic synapses.
    causal_link_type: DIRECT
  - target: Impaired Functional Maturation of Excitatory Synapses
    description: >-
      The same scaffold deficit leaves excitatory synapses structurally and
      functionally immature during the period of synaptogenesis.
    causal_link_type: DIRECT
- name: Impaired Functional Maturation of Excitatory Synapses
  biological_scale: CELLULAR
  role: central_effector
  conforms_to: "excitatory_synapse_scaffold_disruption#Excitatory Postsynaptic Structural Deficit"
  description: >
    PSD-95 level is instructive, not merely permissive, for excitatory synapse
    maturation: raising it drives glutamatergic synapses to maturity, enhances
    presynaptic terminal maturation transsynaptically, and increases the number
    and size of dendritic spines. Halving it therefore leaves a developing
    cortex with fewer functionally mature excitatory synapses during the window
    of synaptogenesis.

    The maturation failure is functional and is explicitly dissociated from
    spine morphology, which is the single most important caveat on this node. In
    the complete knockout the functionally silent synapses sit on
    morphologically mature spines, and PSD-95 mutant mice show unaffected
    synaptic morphology — so this entry deliberately does not assert a
    dendritic-spine-development deficit, and a negative spine-imaging result in
    a DLG4 model or patient neuron would not count against the node.
  cell_types:
  - preferred_term: Cortical and hippocampal pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  biological_processes:
  - preferred_term: Synapse assembly
    term:
      id: GO:0007416
      label: synapse assembly
    modifier: DECREASED
  - preferred_term: Glutamate receptor signaling pathway
    term:
      id: GO:0007215
      label: glutamate receptor signaling pathway
    modifier: DECREASED
  evidence:
  - reference: PMID:11082065
    reference_title: PSD-95 involvement in maturation of excitatory synapses.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We found that overexpression of PSD-95 in hippocampal neurons can drive maturation of glutamatergic synapses."
    explanation: >-
      Establishes PSD-95 dose as instructive for excitatory synapse maturation.
      Note the direction: this is a gain-of-dose experiment, so it constrains the
      dose-response relationship rather than measuring the haploinsufficient state.
  - reference: PMID:17148601
    reference_title: Synapse-specific regulation of AMPA receptor function by PSD-95.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In addition, we report that the decay of NMDAR-mediated current was slower in KO mice: The contribution of NR2B subunit containing receptors to the NMDAR-mediated synaptic current was greater in KO mice."
    explanation: >-
      Loss-of-function direction: the receptor complement shifts toward the
      GluN2B-dominated configuration characteristic of immature synapses, which
      is what "functional immaturity" means here.
  - reference: PMID:29169997
    reference_title: "PSD95: A synaptic protein implicated in schizophrenia or autism?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In this review, we describe the role of PSD-95 as an essential scaffolding protein during synaptogenesis and neurodevelopment."
    explanation: >-
      Frames PSD-95 as essential specifically during synaptogenesis and
      neurodevelopment, the developmental window in which the haploinsufficiency
      acts; evidence_source OTHER because this is a narrative review.
  - reference: PMID:29460436
    reference_title: Truncating variants of the DLG4 gene are responsible for intellectual
      disability with marfanoid features.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PSD-95 probably participates in dendritogenesis."
    explanation: >-
      The DLG4 discovery paper invokes dendritogenesis, but hedges ("probably"),
      so this supports the claim only weakly on the human side.
  - reference: PMID:9853749
    reference_title: Enhanced long-term potentiation and impaired learning in mice with
      mutant postsynaptic density-95 protein.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "Synaptic NMDA-receptor currents, subunit expression, localization and synaptic morphology are all unaffected in the mutant mice."
    explanation: >-
      Refutes any structural reading of this node: PSD-95 mutant mice show
      unaffected synaptic morphology, so the maturation deficit curated here must
      be understood as functional rather than morphological.
  - reference: PMID:17148601
    reference_title: Synapse-specific regulation of AMPA receptor function by PSD-95.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "Unexpectedly, the silent synapses in the KO mouse were located onto morphologically mature spines."
    explanation: >-
      Independently refutes a spine-morphology reading: the functionally silent
      synapses sit on spines that look mature, which is why no dendritic-spine
      GO term with a DECREASED modifier is asserted on this node.
  downstream:
  - target: Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance
    description: >-
      An immature excitatory synapse population cannot support normal
      activity-dependent plasticity.
    causal_link_type: DIRECT
- name: Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance
  biological_scale: CELLULAR
  role: central_effector
  conforms_to: "excitatory_synapse_scaffold_disruption#Impaired Synaptic Plasticity and Excitatory-Inhibitory Imbalance"
  description: >
    PSD-95 couples the NMDA receptor to the machinery that decides whether a
    given firing pattern potentiates or depresses a synapse. Without it, the
    frequency-response function of NMDA-dependent long-term potentiation and
    depression is shifted, producing strikingly enhanced LTP across stimulation
    frequencies rather than a simple loss of plasticity — a bidirectional
    learning rule broken in the direction of over-potentiation. The
    excitation-inhibition framing is an inference rather than a measurement in
    this disorder: the studies cited here quantified glutamatergic transmission
    and plasticity only, and none of them measured GABAergic transmission
    alongside it. PSD-95 is confined to excitatory synapses, so a shifted set
    point is the expected consequence, but a comparable inhibitory deficit has
    not been excluded.
  cell_types:
  - preferred_term: Glutamatergic neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  biological_processes:
  - preferred_term: Long-term synaptic potentiation
    term:
      id: GO:0060291
      label: long-term synaptic potentiation
    modifier: DYSREGULATED
  - preferred_term: Regulation of synaptic plasticity
    term:
      id: GO:0048167
      label: regulation of synaptic plasticity
    modifier: DYSREGULATED
  - preferred_term: Glutamatergic synaptic transmission
    term:
      id: GO:0035249
      label: synaptic transmission, glutamatergic
    modifier: DECREASED
  evidence:
  - reference: PMID:9853749
    reference_title: "Enhanced long-term potentiation and impaired learning in mice with mutant postsynaptic density-95 protein."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In mutant mice lacking PSD-95, the frequency function of NMDA-dependent LTP and LTD is shifted to produce strikingly enhanced LTP at different frequencies of synaptic stimulation."
    explanation: The defining plasticity phenotype of PSD-95 loss — a shifted bidirectional learning rule, not simply absent plasticity.
  - reference: PMID:9853749
    reference_title: "Enhanced long-term potentiation and impaired learning in mice with mutant postsynaptic density-95 protein."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "PSD-95 thus appears to be important in coupling the NMDA receptor to pathways that control bidirectional synaptic plasticity and learning."
    explanation: States the mechanistic role of PSD-95 as the coupler between NMDA receptor and plasticity machinery.
  - reference: PMID:23268962
    reference_title: "Impaired synaptic clustering of postsynaptic density proteins and altered signal transmission in hippocampal neurons, and disrupted learning behavior in PDZ1 and PDZ2 ligand binding-deficient PSD-95 knockin mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In the hippocampal CA1 region of young KI mice, basal synaptic efficacy was reduced and long-term potentiation (LTP) was enhanced with intact long-term depression."
    explanation: >-
      Independently reproduces the paradoxical pattern — reduced basal
      excitatory efficacy with enhanced LTP — in a PDZ1/2 ligand-binding-deficient
      knock-in, showing it follows from lost receptor anchoring rather than from
      the particular null allele.
  downstream:
  - target: Cortical Network Dysfunction and Hyperexcitability
    description: >-
      Synapse-level plasticity failure and a shifted E/I set point aggregate
      into abnormal cortical circuit assembly and network excitability.
    causal_link_type: DIRECT
- name: Cortical Network Dysfunction and Hyperexcitability
  biological_scale: TISSUE
  role: consequence
  conforms_to: "excitatory_synapse_scaffold_disruption#Circuit-Level Dysfunction"
  description: >
    Aggregated synaptic deficits produce diffuse, bilateral cortical and
    hippocampal circuit dysfunction. Structural imaging is deliberately
    unhelpful here: brain MRI in individuals with pathogenic DLG4 variants shows
    abnormalities that are diverse and nonspecific, so the circuit lesion is
    functional rather than a visible malformation. In roughly half of
    individuals the shifted excitation-inhibition set point crosses into frank
    epileptogenesis, with a wide range of seizure types of which focal seizures
    are the most common.
  cell_types:
  - preferred_term: Cortical and hippocampal pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  locations:
  - preferred_term: Neocortex
    term:
      id: UBERON:0001950
      label: neocortex
  - preferred_term: Hippocampal formation
    term:
      id: UBERON:0002421
      label: hippocampal formation
  biological_processes:
  - preferred_term: Chemical synaptic transmission
    term:
      id: GO:0007268
      label: chemical synaptic transmission
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A large variety of seizure types was reported, although focal seizures were the most common."
    explanation: Characterizes the epileptic output of the circuit lesion in the largest epilepsy-focused cohort.
  - reference: PMID:35457207
    reference_title: "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain magnetic resonance imaging (MRI) of the individuals with pathogenic DLG4 variants revealed that the structural brain abnormalities were diverse and nonspecific."
    explanation: Supports framing the circuit lesion as functional rather than a discrete structural malformation.
  downstream:
  - target: Sleep-Activated Epileptiform Encephalopathy (DEE-SWAS/ESES)
    description: >-
      In a subgroup, cortical hyperexcitability becomes sleep-potentiated and
      crosses into a continuous spike-wave encephalopathy.
    causal_link_type: DIRECT
  - target: Developmental Regression
    description: >-
      Regression also occurs in individuals who never develop ESES/DEE-SWAS, so
      circuit dysfunction has a route to skill loss that does not pass through
      the sleep-activated state.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Neurodevelopmental Phenotypic Output
    description: >-
      Diffuse cortical circuit dysfunction manifests as the core cognitive,
      behavioural and motor phenotype.
    causal_link_type: DIRECT
- name: Sleep-Activated Epileptiform Encephalopathy (DEE-SWAS/ESES)
  biological_scale: TISSUE
  role: consequence
  description: >
    In about a quarter of individuals with DLG4-related epilepsy, epileptiform
    activity is massively potentiated by slow-wave sleep, producing
    encephalopathy related to status epilepticus during slow-wave sleep
    (ESES) / developmental epileptic encephalopathy with spike-wave activation
    during sleep (DEE-SWAS). This is a distinct circuit state, not merely more
    seizures: the abnormality is near-continuous sleep-activated spike-wave, and
    because the driving activity occurs in sleep it is invisible to a routine
    awake EEG. Sleep or 24-hour EEG is therefore the specific investigation this
    node motivates.
  biological_processes:
  - preferred_term: Chemical synaptic transmission
    term:
      id: GO:0007268
      label: chemical synaptic transmission
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Encephalopathy related to status epilepticus during slow-wave sleep (ESES)/developmental epileptic encephalopathy with spike-wave activation during sleep (DEE-SWAS) was diagnosed in >25% of the individuals."
    explanation: Quantifies the DEE-SWAS/ESES subgroup within the DLG4 epilepsy cohort.
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Occurrence of ESES/DEE-SWAS in DLG4-related synaptopathy requires proper investigation with sleep EEG."
    explanation: Supports the sleep-EEG surveillance implication that follows from the sleep-activated mechanism.
  downstream:
  - target: Developmental Regression
    description: >-
      Sleep-activated epileptiform encephalopathy drives loss of previously
      acquired verbal and motor skills; regression was observed in every
      individual with ESES/DEE-SWAS.
    causal_link_type: DIRECT
- name: Developmental Regression
  biological_scale: ORGANISM
  role: consequence
  description: >
    Loss of previously acquired verbal and/or motor skills, which converts an
    otherwise largely static developmental disorder into an actively regressive
    one and is the strongest determinant of cognitive outcome.

    This node is deliberately separate from the sleep-activated encephalopathy
    that most often drives it, because the evidence decouples them in both
    directions: regression occurred in every individual with ESES/DEE-SWAS but
    also in some who never developed it, so it has a second route from cortical
    circuit dysfunction that does not pass through the sleep-activated state.
    Regression is also not confined to childhood — intellectual regression
    without motor delay has been reported at age two, and cognitive regression
    with progressive dystonia in adulthood.
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Regression in verbal and/or motor domains was observed in all individuals who suffered from ESES/DEE-SWAS, as well as some who did not."
    explanation: >-
      The sentence that both establishes the coupling to DEE-SWAS and shows it
      is not exclusive — the reason these are two nodes rather than one.
  - reference: PMID:37347881
    reference_title: DLG4-Related Synaptopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Regression in motor development and/or language has been reported in about 40% of affected individuals."
    explanation: Quantifies regression across the disorder as a whole, not only within the epilepsy subgroup.
  downstream:
  - target: Neurodevelopmental Phenotypic Output
    description: >-
      Active regression subtracts from the developmental trajectory, worsening
      the cognitive and language outcome.
    causal_link_type: DIRECT
- name: Neurodevelopmental Phenotypic Output
  biological_scale: ORGANISM
  role: consequence
  conforms_to: "excitatory_synapse_scaffold_disruption#Neurodevelopmental Phenotypic Output"
  description: >
    The clinical convergence point of the synaptopathy: early-onset global
    developmental delay, intellectual disability that is most often mild to
    moderate, autism spectrum disorder and attention deficit-hyperactivity
    disorder, together with hypotonia, movement disorders and sleep
    disturbance. The overlap with other synaptic-dysfunction neurodevelopmental
    disorders is what motivated the "synaptopathy" designation in the first
    place, and is why the clinical gestalt alone cannot establish the diagnosis.
  cell_types:
  - preferred_term: Glutamatergic neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  evidence:
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder."
    explanation: States the core clinical output of the mechanism in the founding cohort.
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The present study shows that clinical manifestations associated with DLG4 overlap with those found in other neurodevelopmental disorders of synaptic dysfunction; thus, we designate this group of disorders as DLG4-related synaptopathy."
    explanation: Supports the framing of the phenotypic output as a shared synaptopathy convergence point.
phenotypes:
- category: Nervous System
  name: Intellectual disability
  description: >-
    Intellectual disability is essentially universal and is most commonly in the
    mild-to-moderate range, though severe presentations occur, particularly in
    the regressive DEE-SWAS subgroup.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "DLG4-related synaptopathy is characterized by developmental delay, intellectual disability (most commonly in the mild-to-moderate range), and autism spectrum disorder."
    explanation: GeneReviews names intellectual disability as a defining feature and gives its typical severity range.
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."
    explanation: The original discovery series independently reports mild-to-moderate intellectual disability.
- category: Nervous System
  name: Global developmental delay
  description: >-
    Early-onset delay across motor, language and cognitive domains, recognizable
    within the first years of life.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder."
    explanation: Global developmental delay heads the list of predominant features in the founding cohort.
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All but one individual presented with neurodevelopmental delay."
    explanation: Near-universal neurodevelopmental delay in the independent epilepsy-focused cohort.
- category: Nervous System
  name: Delayed speech and language development
  description: >-
    Language acquisition is delayed and is one of the two domains in which
    regression is typically observed.
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Regression in verbal and/or motor domains was observed in all individuals who suffered from ESES/DEE-SWAS, as well as some who did not."
    explanation: >-
      Supports verbal-domain involvement, but describes loss of acquired
      language rather than the initial delay, so the evidence is indirect for
      the delay itself.
- category: Nervous System
  name: Developmental regression
  description: >-
    Loss of previously acquired motor and/or language skills, reported in about
    40% of affected individuals and occurring in essentially every individual
    with sleep-activated epileptiform encephalopathy. Adult-onset cognitive
    regression has also been described.
  phenotype_term:
    preferred_term: Developmental regression
    term:
      id: HP:0002376
      label: Developmental regression
  frequency: FREQUENT
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Regression in motor development and/or language has been reported in about 40% of affected individuals."
    explanation: Quantifies regression at ~40%, which maps to the FREQUENT band (30-79%).
  - reference: PMID:42551111
    reference_title: "Intellectual disability, neuroregression and adult-onset progressive dystonia due to a DLG4 pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report a 34-year-old male with childhood developmental delay, severe intellectual disability in adulthood, episodes of agitation with a previous diagnosis of schizoaffective disorder and adult-onset cognitive regression who developed progressive generalised dystonia due to a de novo DLG4 pathogenic loss-of-function variant."
    explanation: Documents that regression is not confined to childhood, extending the temporal window of this phenotype.
  - reference: PMID:38182567
    reference_title: "A novel DLG4 variant causes DLG4-related synaptopathy with intellectual regression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intellectual regression without motor delay was observed at 2 years of age, and she was diagnosed with autism spectrum disorder and attention-deficit/hyperactivity disorder."
    explanation: >-
      Shows regression can present in the intellectual domain alone, as early as
      age two and without accompanying motor delay, widening the presentation
      this phenotype can take.
- category: Nervous System
  name: Autism spectrum disorder
  description: >-
    Autism spectrum disorder is a defining feature of the syndrome and is
    reported as more frequent in individuals with moderate-to-severe
    intellectual disability.
  phenotype_term:
    preferred_term: Autism
    term:
      id: HP:0000717
      label: Autism
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "DLG4-related synaptopathy is characterized by developmental delay, intellectual disability (most commonly in the mild-to-moderate range), and autism spectrum disorder."
    explanation: GeneReviews includes autism spectrum disorder in the defining clinical characterization.
- category: Nervous System
  name: Attention deficit hyperactivity disorder
  description: >-
    ADHD is one of the four features that dominated the clinical picture in the
    founding cohort.
  phenotype_term:
    preferred_term: Attention deficit hyperactivity disorder
    term:
      id: HP:0007018
      label: Attention deficit hyperactivity disorder
  evidence:
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder."
    explanation: ADHD is named as one of the four predominant features of the disorder.
- category: Nervous System
  name: Epilepsy
  description: >-
    Epilepsy affects about half of individuals, with a wide range of seizure
    types of which focal seizures are the most common. Onset is typically in
    childhood, but no age-at-onset figure is asserted here because no source
    retrievable into the reference cache states one.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  frequency: FREQUENT
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "About half of affected individuals have epilepsy."
    explanation: GeneReviews gives the epilepsy frequency as about half, mapping to FREQUENT (30-79%).
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Even though epilepsy is present in 50% of the individuals, it has not been investigated in detail."
    explanation: >-
      Restates the 50% figure from the prior literature as background. It is not
      an independent measurement: this cohort was ascertained on having both a
      DLG4 variant and epilepsy, so epilepsy frequency within it is 100% by
      construction. The FREQUENT band rests on the GeneReviews statement above.
- category: Nervous System
  name: Focal-onset seizure
  description: >-
    Focal seizures are the single most common seizure type in the DLG4 epilepsy
    cohort, although the overall seizure semiology is heterogeneous.
  phenotype_term:
    preferred_term: Focal-onset seizure
    term:
      id: HP:0007359
      label: Focal-onset seizure
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A large variety of seizure types was reported, although focal seizures were the most common."
    explanation: Directly identifies focal seizures as the predominant seizure type.
- category: Nervous System
  name: Developmental and epileptic encephalopathy with spike-wave activation in sleep
  description: >-
    ESES/DEE-SWAS, diagnosed in more than a quarter of individuals in the
    epilepsy cohort, is the most clinically consequential complication and is
    invariably accompanied by developmental regression. Detection requires sleep
    or 24-hour EEG rather than a routine awake recording.
  phenotype_term:
    preferred_term: Continuous spike and waves during slow sleep
    term:
      id: HP:0031491
      label: Continuous spike and waves during slow sleep
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our study shows that a subgroup of individuals with DLG4-related synaptopathy have DEE, and approximately one fourth of them have ESES/DEE-SWAS."
    explanation: Establishes DEE-SWAS/ESES as part of the phenotypic spectrum and quantifies the subgroup.
- category: Nervous System
  name: Hypotonia
  description: >-
    Central hypotonia is one of the major clinical features and one of the five
    features in the SHINE acronym.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features are developmental delay, intellectual disability (ID), hypotonia, sleep disturbances, movement disorders, and epilepsy."
    explanation: Hypotonia is listed among the major clinical features of the disorder.
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."
    explanation: GeneReviews lists hypotonia among the neurologic findings.
- category: Nervous System
  name: Motor stereotypy
  description: >-
    Stereotypies are, with ataxia, the most common movement-disorder
    manifestation.
  phenotype_term:
    preferred_term: Motor stereotypy
    term:
      id: HP:0000733
      label: Motor stereotypy
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."
    explanation: Names stereotypies as one of the two most common movement-disorder features.
- category: Nervous System
  name: Ataxia
  description: >-
    Ataxia is, with stereotypies, the most commonly reported movement disorder.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."
    explanation: Names ataxia as one of the two most common movement-disorder features.
- category: Nervous System
  name: Dystonia
  description: >-
    Dystonia is part of the movement-disorder spectrum; a progressive
    generalised, adult-onset form has been reported and expands the recognized
    movement-disorder phenotype.
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."
    explanation: GeneReviews lists dystonia among the neurologic findings.
  - reference: PMID:42551111
    reference_title: "Intellectual disability, neuroregression and adult-onset progressive dystonia due to a DLG4 pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This case expands the phenotypic spectrum of recognised movement disorder manifestations associated with DLG4-related synaptopathy."
    explanation: Documents progressive generalised adult-onset dystonia as an extension of the movement-disorder spectrum.
- category: Nervous System
  name: Tremor
  description: Tremor is reported among the neurologic findings of the disorder.
  phenotype_term:
    preferred_term: Tremor
    term:
      id: HP:0001337
      label: Tremor
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."
    explanation: GeneReviews lists tremor among the neurologic findings.
- category: Nervous System
  name: Migraine
  description: Migraine headaches occur and are an explicit target of supportive management.
  phenotype_term:
    preferred_term: Migraine
    term:
      id: HP:0002076
      label: Migraine
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other neurologic findings can include hypotonia, movement disorder (most commonly stereotypies and ataxia), dystonia, tremor, and migraine headaches."
    explanation: GeneReviews lists migraine headaches among the neurologic findings.
- category: Nervous System
  name: Sleep disturbance
  description: >-
    Sleep disturbance is common and gives the SHINE acronym its initial letter;
    both sleep-onset and sleep-maintenance difficulties are frequently reported.
  phenotype_term:
    preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  frequency: FREQUENT
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sleep disturbance is common, with sleep onset and/or sleep maintenance difficulties being frequently reported."
    explanation: >-
      GeneReviews describes sleep disturbance as "common" and "frequently
      reported", the qualitative-term pattern that maps to FREQUENT.
- category: Nervous System
  name: Anxiety
  description: >-
    Anxiety is a recognized behavioural manifestation and one of the issues
    GeneReviews directs clinicians to screen for at every post-infancy visit.
    Both curated mouse models independently show anxiety-related phenotypes,
    so this is one of the few behavioural features with converging human and
    model-organism support.
  phenotype_term:
    preferred_term: Anxiety
    term:
      id: HP:0000739
      label: Anxiety
  evidence:
  - reference: PMID:37347881
    reference_title: DLG4-Related Synaptopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "At each visit after infancy, assess for behavioral issues such as anxiety, autism spectrum disorder, attention-deficit/hyperactivity disorder, aggression, or self-injury."
    explanation: >-
      GeneReviews names anxiety among the behavioural issues requiring ongoing
      surveillance in this disorder. No frequency band is asserted, since the
      surveillance sentence is not quantitative.
  - reference: PMID:23268962
    reference_title: "Impaired synaptic clustering of postsynaptic density proteins and altered signal transmission in hippocampal neurons, and disrupted learning behavior in PDZ1 and PDZ2 ligand binding-deficient PSD-95 knockin mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In a battery of behavioral tests, KI mice showed markedly abnormal anxiety-like behavior, impaired spatial reference and working memory, and impaired remote memory and pattern separation in fear conditioning test."
    explanation: >-
      Model-organism corroboration: the PDZ1/2 ligand-binding-deficient knock-in
      shows an anxiety-like phenotype, matching the human behavioural feature.
- category: Nervous System
  name: Aggressive behavior
  description: >-
    Aggression is one of the behavioural issues GeneReviews directs clinicians
    to assess for at every visit after infancy.
  phenotype_term:
    preferred_term: Aggressive behavior
    term:
      id: HP:0000718
      label: Aggressive behavior
  evidence:
  - reference: PMID:37347881
    reference_title: DLG4-Related Synaptopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "At each visit after infancy, assess for behavioral issues such as anxiety, autism spectrum disorder, attention-deficit/hyperactivity disorder, aggression, or self-injury."
    explanation: >-
      GeneReviews names aggression among the behavioural issues requiring
      ongoing surveillance. Not quantitative, so no frequency band is asserted.
- category: Nervous System
  name: Self-injurious behavior
  description: >-
    Self-injury is one of the behavioural issues GeneReviews directs clinicians
    to assess for at every visit after infancy.
  phenotype_term:
    preferred_term: Self-injurious behavior
    term:
      id: HP:0100716
      label: Self-injurious behavior
  evidence:
  - reference: PMID:37347881
    reference_title: DLG4-Related Synaptopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "At each visit after infancy, assess for behavioral issues such as anxiety, autism spectrum disorder, attention-deficit/hyperactivity disorder, aggression, or self-injury."
    explanation: >-
      GeneReviews names self-injury among the behavioural issues requiring
      ongoing surveillance. Not quantitative, so no frequency band is asserted.
- category: Nervous System
  name: Psychosis
  description: >-
    Psychosis is not a cardinal feature but is reported in a minority; a
    documented case of early-onset, treatment-resistant schizophrenia with
    catatonia responded to clozapine.
  phenotype_term:
    preferred_term: Psychosis
    term:
      id: HP:0000709
      label: Psychosis
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:37386468
    reference_title: "Significant improvement of psychotic symptoms in treatment-resistant schizophrenia with clozapine in an adolescent with SHINE syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additionally, while psychosis is not considered a cardinal feature of SHINE syndrome, 10% of the 53 documented cases had reported psychosis"
    explanation: Quantifies psychosis at 10% of published cases, which maps to the OCCASIONAL band (5-29%).
- category: Eye
  name: Strabismus
  description: Strabismus is the most common ocular finding.
  phenotype_term:
    preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Strabismus is the most common ocular finding followed by hyperopia, nystagmus, and cortical blindness."
    explanation: Identifies strabismus as the leading ophthalmologic manifestation.
- category: Eye
  name: Hypermetropia
  description: Hyperopia is the second most common ocular finding.
  phenotype_term:
    preferred_term: Hypermetropia
    term:
      id: HP:0000540
      label: Hypermetropia
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Strabismus is the most common ocular finding followed by hyperopia, nystagmus, and cortical blindness."
    explanation: Ranks hyperopia second among ocular findings.
- category: Eye
  name: Nystagmus
  description: Nystagmus is among the reported ophthalmologic manifestations.
  phenotype_term:
    preferred_term: Nystagmus
    term:
      id: HP:0000639
      label: Nystagmus
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Strabismus is the most common ocular finding followed by hyperopia, nystagmus, and cortical blindness."
    explanation: Lists nystagmus among the ocular findings.
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."
    explanation: Independent report of nystagmus in the original DLG4 discovery series.
- category: Eye
  name: Cerebral visual impairment
  description: >-
    Cortical (cerebral) visual impairment is the least common of the reported
    ocular findings and is an explicit target of supportive management.
  phenotype_term:
    preferred_term: Cerebral visual impairment
    term:
      id: HP:0100704
      label: Cerebral visual impairment
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Strabismus is the most common ocular finding followed by hyperopia, nystagmus, and cortical blindness."
    explanation: Lists cortical blindness last among the ocular findings.
- category: Digestive
  name: Vomiting
  description: >-
    Vomiting occurs in a number of individuals and is characteristically
    triggered by seizures, motion sickness or fatigue.
  phenotype_term:
    preferred_term: Vomiting
    term:
      id: HP:0002013
      label: Vomiting
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Vomiting is observed in a number of individuals and can be triggered by seizures, motion sickness, or fatigue."
    explanation: >-
      GeneReviews reports vomiting and its triggers; the phrasing "a number of
      individuals" is not quantitative, so no frequency band is asserted.
- category: Musculoskeletal
  name: Joint hypermobility
  description: Joint laxity is a relatively common finding, reported in 36.9% of individuals.
  phenotype_term:
    preferred_term: Joint hypermobility
    term:
      id: HP:0001382
      label: Joint hypermobility
  frequency: FREQUENT
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Joint laxity is a relatively common finding (36.9%), and scoliosis is noted in 20% of individuals."
    explanation: The 36.9% figure falls in the FREQUENT band (30-79%).
- category: Musculoskeletal
  name: Scoliosis
  description: Scoliosis is noted in 20% of individuals and warrants orthopaedic surveillance.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Joint laxity is a relatively common finding (36.9%), and scoliosis is noted in 20% of individuals."
    explanation: The 20% figure falls in the OCCASIONAL band (5-29%).
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."
    explanation: >-
      Scoliosis was part of the original marfanoid presentation through which
      DLG4 was discovered. PARTIAL because that series was selected for
      marfanoid habitus, so it cannot speak to how often scoliosis occurs in
      unselected DLG4 patients; the frequency band above rests on GeneReviews.
- category: Growth
  name: Marfanoid habitus
  description: >-
    A marfanoid habitus was the presentation through which DLG4 was first
    implicated in intellectual disability, but the founding 53-patient cohort
    found it in only nine individuals, so it is a minority feature rather than a
    defining one.
  phenotype_term:
    preferred_term: Marfanoid habitus
    term:
      id: HP:0001519
      label: Disproportionate tall stature
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Marfanoid habitus, which was previously suggested to be a characteristic feature of DLG4-related phenotypes, was found in only nine individuals and despite some overlapping features, a distinct facial dysmorphism could not be established."
    explanation: >-
      Confirms marfanoid habitus occurs but explicitly downgrades it from a
      characteristic feature, so this both supports the phenotype and refutes
      its earlier diagnostic weight. The OCCASIONAL band is derived rather than
      quoted: nine individuals out of the 53 in this cohort is 17%, within the
      5-29% band (derived-count pattern, docs/frequency-evidence-guidelines.md).
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."
    explanation: >-
      The original discovery series describing the marfanoid presentation in
      detail. PARTIAL because the cohort was selected for marfanoid habitus, so
      it establishes the phenotype's existence but not its prevalence.
- category: Head and Neck
  name: High palate
  description: >-
    A high-arched palate is part of the marfanoid presentation.
    Ascertainment caveat: this feature is evidenced only by the three-patient
    DLG4 discovery series, which was drawn from a cohort selected for marfanoid
    habitus, so its apparent association with DLG4 is inflated by the way those
    patients were found. The 53-patient unselected cohort found marfanoid
    habitus in only nine individuals and could not establish a distinct facial
    dysmorphism.
  phenotype_term:
    preferred_term: High palate
    term:
      id: HP:0000218
      label: High palate
  evidence:
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."
    explanation: >-
      High-arched palate is listed among the marfanoid features in the discovery
      series. PARTIAL: three patients from a marfanoid-selected cohort.
- category: Head and Neck
  name: Long face
  description: >-
    A long face is part of the marfanoid presentation.
    Ascertainment caveat: this feature is evidenced only by the three-patient
    DLG4 discovery series, which was drawn from a cohort selected for marfanoid
    habitus, so its apparent association with DLG4 is inflated by the way those
    patients were found. The 53-patient unselected cohort found marfanoid
    habitus in only nine individuals and could not establish a distinct facial
    dysmorphism.
  phenotype_term:
    preferred_term: Long face
    term:
      id: HP:0000276
      label: Long face
  evidence:
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."
    explanation: >-
      Long face is listed among the marfanoid features in the discovery series.
      PARTIAL: three patients from a marfanoid-selected cohort, and the
      unselected cohort could not establish a distinct facial dysmorphism.
- category: Limbs
  name: Arachnodactyly
  description: >-
    Long, thin fingers are part of the marfanoid presentation.
    Ascertainment caveat: this feature is evidenced only by the three-patient
    DLG4 discovery series, which was drawn from a cohort selected for marfanoid
    habitus, so its apparent association with DLG4 is inflated by the way those
    patients were found. The 53-patient unselected cohort found marfanoid
    habitus in only nine individuals and could not establish a distinct facial
    dysmorphism.
  phenotype_term:
    preferred_term: Arachnodactyly
    term:
      id: HP:0001166
      label: Arachnodactyly
  evidence:
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."
    explanation: >-
      Long and thin fingers, i.e. arachnodactyly, are listed among the marfanoid
      features. PARTIAL: three patients from a marfanoid-selected cohort.
- category: Musculoskeletal
  name: Pectus excavatum
  description: >-
    Pectus excavatum is part of the marfanoid presentation.
    Ascertainment caveat: this feature is evidenced only by the three-patient
    DLG4 discovery series, which was drawn from a cohort selected for marfanoid
    habitus, so its apparent association with DLG4 is inflated by the way those
    patients were found. The 53-patient unselected cohort found marfanoid
    habitus in only nine individuals and could not establish a distinct facial
    dysmorphism.
  phenotype_term:
    preferred_term: Pectus excavatum
    term:
      id: HP:0000767
      label: Pectus excavatum
  evidence:
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."
    explanation: >-
      Pectus excavatum is listed among the marfanoid features in the discovery
      series. PARTIAL: three patients from a marfanoid-selected cohort.
genetic:
- name: DLG4
  gene_term:
    preferred_term: DLG4
    term:
      id: hgnc:2903
      label: DLG4
  relationship_type: CAUSATIVE
  presence: PRESENT
  variant_origin: DE_NOVO
  notes: >-
    DLG4 (17p13.1) encodes PSD-95, the prototypic and most abundant DLG-family
    MAGUK of the excitatory postsynaptic density. It is the sole established
    causal gene for this disorder. Reported variant classes span nonsense,
    frameshift, canonical splice-site, missense, synonymous splice-disrupting
    and deep-intronic pseudoexon-activating alleles; no pathogenic
    gene-level copy-number variants have been reported.
  evidence:
  - reference: PMID:33597769
    reference_title: "DLG4-related synaptopathy: a new rare brain disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Postsynaptic density protein-95 (PSD-95), encoded by DLG4, regulates excitatory synaptic function in the brain."
    explanation: Establishes the gene-protein relationship and the protein's synaptic role.
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only DLG4 gene met these criteria."
    explanation: >-
      In the exome study of 64 marfanoid-habitus intellectual-disability
      probands, DLG4 was the single gene meeting the recurrent-truncating-variant
      discovery criteria, establishing the gene-disease link.
  - reference: PMID:35457207
    reference_title: "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only six missense variants, all localizing to the highly conserved functional domains of PSD-95, have been reported."
    explanation: Characterizes the missense minority and its localization to conserved domains.
variants:
- name: DLG4 c.2105+235C>T (deep intronic, pseudoexon-activating)
  gene:
    preferred_term: DLG4
    term:
      id: hgnc:2903
      label: DLG4
  type: SNV
  clinical_significance: PATHOGENIC
  description: >-
    A deep intronic variant identified by whole genome sequencing that generates
    two alternative DLG4 transcripts, one containing a pseudoexon; both are
    out-of-frame and predicted to truncate the protein. Notable because it is
    invisible to exome sequencing and because DLG4 mRNA proved detectable in
    peripheral blood, making an accessible-tissue RNA assay diagnostic.
  evidence:
  - reference: PMID:37525972
    reference_title: "A deep intronic DLG4 variant resulting in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both alternative transcripts are out-of-frame and predicted to result in protein-truncation, thereby establishing the genetic diagnosis for the proband."
    explanation: Establishes the pathogenic splice-disrupting consequence of the deep intronic variant.
- name: DLG4 c.771G>A p.(Ala257=) (synonymous, exon 9 skipping)
  gene:
    preferred_term: DLG4
    term:
      id: hgnc:2903
      label: DLG4
  type: SNV
  clinical_significance: PATHOGENIC
  description: >-
    A synonymous variant with previously conflicting ClinVar interpretations,
    shown by RNA sequencing and RT-PCR to cause complete exon 9 skipping with a
    resulting frameshift and premature termination codon. Its origin was
    paternal germline mosaicism, detected by high-depth amplicon sequencing of
    sperm DNA.
  evidence:
  - reference: PMID:42482343
    reference_title: "A Synonymous DLG4 Variant (c.771G>A) Causes Exon 9 Skipping via Paternal Germline Mosaicism in DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The synonymous DLG4 c.771G>A variant (absent in gnomAD) induced complete exon 9 skipping, resulting in a frameshift and premature termination codon."
    explanation: Functional RNA evidence resolving a synonymous variant as loss-of-function.
diagnosis:
- name: Molecular genetic testing for a heterozygous DLG4 pathogenic variant
  presence: PRESENT
  description: >-
    The diagnosis is genotype-first. The clinical picture overlaps other
    synaptopathies too closely to be diagnostic on its own, so a multigene
    intellectual-disability/epilepsy panel or exome/genome sequencing is the
    appropriate test. RNA studies should be considered for synonymous, missense
    or intronic variants of uncertain splicing consequence, and DLG4 mRNA is
    detectable in peripheral blood, so an accessible-tissue assay is feasible.
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of DLG4-related synaptopathy is established in a proband with suggestive clinical findings and a heterozygous pathogenic variant in DLG4 identified by molecular genetic testing."
    explanation: GeneReviews states the diagnostic criterion.
  - reference: PMID:37525972
    reference_title: "A deep intronic DLG4 variant resulting in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "By using reverse-transcription PCR on RNA derived from peripheral blood, we demonstrate that DLG4 mRNA expression is detectable in blood and the deep intronic variant gives rise to two alternative DLG4 transcripts, one of which includes a pseudoexon."
    explanation: Supports blood RNA testing as a practical route for resolving splice-uncertain DLG4 variants.
  - reference: PMID:40444229
    reference_title: "Late-onset diagnosis of SHINE syndrome in an adolescent with developmental delay: Case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fourteen years after the initial presentation, additional genetic testing revealed a de-novo mutation in the DLG4 gene, confirming a diagnosis of SHINE syndrome."
    explanation: >-
      Illustrates the long diagnostic delay that follows from the non-specific
      clinical gestalt, and the reason genotype-first testing is recommended
      rather than waiting for a recognizable phenotype.
- name: Sleep or 24-hour EEG
  presence: PRESENT
  description: >-
    Because the DEE-SWAS/ESES pattern is activated by slow-wave sleep, a routine
    awake EEG can miss it. Sleep or 24-hour EEG is indicated in individuals with
    significant cognitive or behavioural delay, developmental regression, or an
    abnormal routine EEG.
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Occurrence of ESES/DEE-SWAS in DLG4-related synaptopathy requires proper investigation with sleep EEG."
    explanation: States the sleep-EEG requirement that follows from the sleep-activated mechanism.
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Annually or as clinically indicated, ophthalmology evaluation; and 24-hour EEG in those with significant cognitive/behavioral delay, developmental regression, or abnormal routine EEG."
    explanation: GeneReviews surveillance recommendation specifying when 24-hour EEG is indicated.
treatments:
- name: Supportive and symptom-directed care
  description: >-
    There is no cure and no disease-modifying therapy. Management is entirely
    supportive: standard treatment of developmental delay and intellectual
    disability, epilepsy, migraine, ataxia, dystonia, refractive error,
    strabismus and cerebral visual impairment, delivered through a
    multidisciplinary surveillance-and-support model.
  treatment_term:
    preferred_term: Supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  therapeutic_modality: OTHER
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There is no cure for DLG4-related synaptopathy. Supportive care includes standard treatment for developmental delay / intellectual disability, epilepsy, migraine, ataxia, dystonia, refractive errors, strabismus, and cerebral visual impairment."
    explanation: GeneReviews management statement, the basis for the supportive-care-only framing.
- name: Antiseizure medication
  description: >-
    Standard antiseizure pharmacotherapy tailored to seizure type. No
    DLG4-specific regimen has been established, and the epilepsy cohort study
    assessed medication response only retrospectively and by referring-clinician
    report, so drug-choice guidance rests on general epilepsy practice rather
    than on evidence specific to this gene.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: anticonvulsant agent
      term:
        id: NCIT:C264
        label: Anticonvulsant Agent
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Cortical Network Dysfunction and Hyperexcitability
    treatment_effect: INHIBITS
    description: >-
      Antiseizure medication suppresses the network hyperexcitability that
      generates seizures; it does not act on the upstream PSD-95 deficit.
  evidence:
  - reference: PMID:37347881
    reference_title: DLG4-Related Synaptopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There is no cure for DLG4-related synaptopathy. Supportive care includes standard treatment for developmental delay / intellectual disability, epilepsy, migraine, ataxia, dystonia, refractive errors, strabismus, and cerebral visual impairment."
    explanation: >-
      GeneReviews states that epilepsy in this disorder is managed with standard
      epilepsy treatment — the management recommendation this treatment entry
      records.
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Antiseizure medication response was retrospectively assessed by the referring clinician."
    explanation: >-
      Kept only as the caveat it is: this is a Methods sentence, not a finding,
      and it is here to make explicit that the largest cohort's
      medication-response data are retrospective and clinician-reported, so no
      agent-specific claim can rest on them.
- name: Clozapine for treatment-resistant psychosis
  description: >-
    In a reported adolescent with DLG4-related synaptopathy and early-onset,
    treatment-resistant schizophrenia with catatonia, clozapine produced
    substantial improvement in positive and negative symptoms after three other
    antipsychotics had failed. This is a single case report and is not a
    treatment recommendation for the disorder.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: clozapine
      term:
        id: CHEBI:3766
        label: clozapine
  therapeutic_modality: SMALL_MOLECULE
  target_phenotypes:
  - preferred_term: Psychosis
    term:
      id: HP:0000709
      label: Psychosis
  evidence:
  - reference: PMID:37386468
    reference_title: "Significant improvement of psychotic symptoms in treatment-resistant schizophrenia with clozapine in an adolescent with SHINE syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "After failing three antipsychotic drug treatments, the patient was started on clozapine, which resulted in significant improvements in positive and negative symptoms."
    explanation: >-
      Single-patient evidence for clozapine responsiveness; graded PARTIAL
      because an uncontrolled n-of-1 observation cannot establish efficacy in
      the disorder.
- name: Behavioural therapy and pharmacotherapy for sleep disturbance
  description: >-
    Behavioural measures are first-line for insomnia, with pharmacotherapy
    reserved for refractory sleep disturbance.
  treatment_term:
    preferred_term: Sleep disorder therapy
    term:
      id: NCIT:C15541
      label: Sleep Disorder Therapy
  therapeutic_modality: BEHAVIORAL
  target_phenotypes:
  - preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Behavioral therapy may aid those who have insomnia, while pharmacotherapy may be considered in those who have refractory sleep disturbance."
    explanation: GeneReviews sets out the stepped approach to sleep disturbance.
- name: Developmental, physical and speech therapy
  description: >-
    Early intervention and ongoing developmental, physical, occupational and
    speech therapies form the core of management for the developmental delay and
    intellectual disability, alongside monitoring of mobility and self-help
    skills.
  treatment_term:
    preferred_term: Rehabilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  therapeutic_modality: BEHAVIORAL
  target_phenotypes:
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "At each visit, monitor those with seizures; assess for new manifestations such as seizures, changes in tone, movement disorders, and migraine headaches; monitor developmental progress and educational needs; assess mobility and self-help skills; and assess for signs/symptoms of sleep disturbance."
    explanation: >-
      GeneReviews surveillance recommendation covering developmental progress,
      educational needs and mobility, the domains these therapies address.
- name: Genetic counseling
  description: >-
    Counseling covers the autosomal dominant, predominantly de novo mechanism;
    the low-but-not-zero sibling recurrence risk from parental germline
    mosaicism, now molecularly confirmed in at least one family; and the
    availability of prenatal and preimplantation genetic testing once the
    familial variant is known.
  treatment_term:
    preferred_term: Genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  therapeutic_modality: OTHER
  evidence:
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, once a DLG4 pathogenic variant has been identified in an affected family member, prenatal and preimplantation genetic testing are possible."
    explanation: GeneReviews genetic-counseling statement on reproductive testing options.
  - reference: PMID:42482343
    reference_title: "A Synonymous DLG4 Variant (c.771G>A) Causes Exon 9 Skipping via Paternal Germline Mosaicism in DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These findings underscore the dual necessity of functional analysis for synonymous variants and sensitive mosaicism detection for accurate genetic counseling."
    explanation: Supports mosaicism testing as a component of recurrence-risk counseling in this disorder.
imaging_findings:
- name: Nonspecific structural brain abnormality on MRI
  modality: MRI
  laterality: BILATERAL
  description: >-
    Brain MRI is part of the diagnostic work-up of developmental delay in this
    disorder but is not diagnostic of it: the structural abnormalities reported
    across the cohort are diverse and nonspecific, consistent with a functional
    synaptic lesion rather than a recognizable malformation. Awake and sleep EEG
    carry the diagnostic weight instead.
  diagnostic: false
  evidence:
  - reference: PMID:35457207
    reference_title: "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain magnetic resonance imaging (MRI) of the individuals with pathogenic DLG4 variants revealed that the structural brain abnormalities were diverse and nonspecific."
    explanation: States that MRI findings in this disorder are heterogeneous and lack a specific pattern.
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Data on awake and sleep electroencephalography (EEG) and/or video-polygraphy and brain magnetic resonance imaging were collected."
    explanation: Confirms MRI is routinely collected in this population alongside awake and sleep EEG.
animal_models:
- name: Dlg4 V692Wfs*12 heterozygous knock-in mouse (patient-derived SHINE allele)
  species: Mouse
  genotype: Dlg4 V692Wfs*12/+ (patient-derived frameshift allele)
  publication: PMID:42565830
  description: >-
    The genetically most faithful model available: a heterozygous knock-in of a
    patient frameshift allele associated with severe disease. The mutant
    transcript escapes nonsense-mediated decay yet still yields reduced PSD-95
    protein, reproducing the patient's molecular phenotype rather than a clean
    null. Behavioural phenotypes are partly sex-specific.
  modeled_mechanisms:
  - target: DLG4 Loss of Function and PSD-95 Haploinsufficiency
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Heterozygous patient allele producing reduced PSD-95 protein — the same
      genetic state and the same molecular endpoint as the human disorder.
    limitations: >-
      Models one specific severe frameshift allele; whether an allele that is
      degraded by nonsense-mediated decay behaves identically is untested.
    readouts:
    - name: PSD-95 protein abundance
      target: DLG4 Loss of Function and PSD-95 Haploinsufficiency
      direction: DECREASED
      interpretation: Reduced PSD-95 protein confirms the haploinsufficient molecular state.
      evidence:
      - reference: PMID:42565830
        reference_title: "A patient-derived mouse model reproduces molecular, neurological, and sleep symptoms of SHINE syndrome."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The mutant transcript escapes nonsense-mediated decay but results in reduced PSD-95 protein expression, faithfully reproducing the molecular phenotype observed in the patient."
        explanation: Reports the reduced PSD-95 protein measurement in the knock-in.
    evidence:
    - reference: PMID:42565830
      reference_title: "A patient-derived mouse model reproduces molecular, neurological, and sleep symptoms of SHINE syndrome."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Here, we developed and characterized a mouse model of SHINE syndrome carrying the patient-derived DLG4V692Wfs*12/+ variant associated with a severe form of the disorder."
      explanation: Establishes the model as a heterozygous patient-allele knock-in, matching the human genetic state.
  - target: Neurodevelopmental Phenotypic Output
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces learning and cognitive-flexibility deficits and a fragmented
      sleep architecture reminiscent of the patient, with trends toward altered
      sensory processing and socialization.
    limitations: >-
      Several phenotypes appeared only in male mutants, and the social and
      sensory findings were trends rather than established effects. Spontaneous
      seizures were not observed, so the epilepsy arm of the human phenotype is
      not captured.
    readouts:
    - name: Learning and cognitive flexibility
      target: Neurodevelopmental Phenotypic Output
      direction: DECREASED
      interpretation: Behavioural correlate of the intellectual-disability phenotype, in male mutants.
      evidence:
      - reference: PMID:42565830
        reference_title: "A patient-derived mouse model reproduces molecular, neurological, and sleep symptoms of SHINE syndrome."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Male mutants showed deficits in learning and cognitive flexibility."
        explanation: Reports the cognitive readout and its sex specificity.
    - name: Sleep bout architecture
      target: Neurodevelopmental Phenotypic Output
      direction: ALTERED
      interpretation: Fragmented sleep, the model correlate of the human sleep-disturbance phenotype.
      evidence:
      - reference: PMID:42565830
        reference_title: "A patient-derived mouse model reproduces molecular, neurological, and sleep symptoms of SHINE syndrome."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Male mutants exhibited an increased proportion of short sleep bouts and compensatory longer average sleep bout length, suggesting sporadic sleep reminiscent of the patient."
        explanation: Reports the sleep-architecture measurement in the model.
    evidence:
    - reference: PMID:42565830
      reference_title: "A patient-derived mouse model reproduces molecular, neurological, and sleep symptoms of SHINE syndrome."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Dlg4V692Wfs*12/+ mice also demonstrate trends toward altered sensory processing and socialization."
      explanation: >-
        Supports the model as informative for the behavioural phenotype while
        showing the sensory and social arms are trends, not established effects.
  - target: Cortical Network Dysfunction and Hyperexcitability
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      No spontaneous seizures were observed in the heterozygous knock-in,
      despite epilepsy affecting about half of individuals with the human
      disorder.
    limitations: >-
      Provoked-seizure susceptibility was not tested, so this is a negative
      result for spontaneous seizures only and does not exclude a latent
      lowered seizure threshold.
    evidence:
    - reference: PMID:42565830
      reference_title: "A patient-derived mouse model reproduces molecular, neurological, and sleep symptoms of SHINE syndrome."
      supports: REFUTE
      evidence_source: MODEL_ORGANISM
      snippet: "While spontaneous seizures were not observed, future studies will test susceptibility to provoked seizures."
      explanation: >-
        Explicit negative result for the epilepsy arm in the most
        genotype-faithful model, and the authors' own statement that the
        provoked-seizure question remains open.
- name: Dlg4 null (PSD-95 knockout) mouse - autism-relevant behaviour
  species: Mouse
  genotype: Dlg4-/- (complete PSD-95 knockout), C57BL/6J congenic
  publication: PMID:20952458
  description: >-
    Complete PSD-95 null mouse phenotyped across repetitive, social, motor and
    anxiety-related behavioural domains, with dendritic-spine and forebrain
    synaptic-gene-expression correlates.
  modeled_mechanisms:
  - target: Neurodevelopmental Phenotypic Output
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Produces a behavioural profile spanning the autism-relevant, motor and
      anxiety domains seen in the human disorder.
    limitations: >-
      Homozygous null, so it models complete PSD-95 absence rather than the
      human heterozygous haploinsufficient state; homozygous deletion also
      adversely affected survival, imposing a survivor-selection bias absent
      from the human condition.
    evidence:
    - reference: PMID:20952458
      reference_title: "Association of mouse Dlg4 (PSD-95) gene deletion and human DLG4 gene variation with phenotypes relevant to autism spectrum disorders and Williams' syndrome."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These findings demonstrate that DLG4 gene disruption in mice produces a complex range of behavioral and molecular abnormalities relevant to autism spectrum disorders and Williams' syndrome."
      explanation: Establishes the null mouse as informative for the behavioural output of DLG4 disruption.
- name: PSD-95 mutant mouse - bidirectional plasticity and spatial learning
  species: Mouse
  genotype: PSD-95 mutant (guanylate kinase domain-truncating)
  publication: PMID:9853749
  description: >-
    The classic PSD-95 mutant used to define the plasticity phenotype: the
    NMDA-dependent LTP/LTD frequency-response is shifted toward enhanced LTP,
    with severely impaired spatial learning and intact synaptic NMDA-receptor
    currents, subunit expression, localization and synaptic morphology.
  modeled_mechanisms:
  - target: Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Demonstrates that losing PSD-95 breaks the bidirectional plasticity rule
      and impairs learning, the mechanistic core of the human cognitive
      phenotype.
    limitations: >-
      This line expresses a truncated PSD-95 rather than being a complete null,
      and it is homozygous, so it does not model human heterozygous
      haploinsufficiency. Learning was assayed as rodent spatial learning, a
      distant proxy for human intellectual disability.
    readouts:
    - name: NMDA-dependent LTP/LTD frequency-response function
      target: Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance
      direction: ALTERED
      interpretation: The plasticity set point is shifted toward potentiation rather than plasticity being lost.
      evidence:
      - reference: PMID:9853749
        reference_title: "Enhanced long-term potentiation and impaired learning in mice with mutant postsynaptic density-95 protein."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "In mutant mice lacking PSD-95, the frequency function of NMDA-dependent LTP and LTD is shifted to produce strikingly enhanced LTP at different frequencies of synaptic stimulation."
        explanation: The electrophysiological measurement behind the plasticity node.
    - name: Spatial learning
      target: Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance
      direction: DECREASED
      interpretation: Behavioural consequence of the shifted plasticity rule.
      evidence:
      - reference: PMID:9853749
        reference_title: "Enhanced long-term potentiation and impaired learning in mice with mutant postsynaptic density-95 protein."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "In keeping with neural-network models that incorporate bidirectional learning rules, this frequency shift is accompanied by severely impaired spatial learning."
        explanation: Reports the learning deficit that accompanies the plasticity shift.
    evidence:
    - reference: PMID:9853749
      reference_title: "Enhanced long-term potentiation and impaired learning in mice with mutant postsynaptic density-95 protein."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "PSD-95 thus appears to be important in coupling the NMDA receptor to pathways that control bidirectional synaptic plasticity and learning."
      explanation: The authors' own statement of what the model establishes about PSD-95 function.
- name: PSD-95 complete knockout mouse - AMPA receptor and silent synapses
  species: Mouse
  genotype: PSD-95-/- (PDZ1-2 deletion, out-of-frame transcript)
  publication: PMID:17148601
  description: >-
    A complete PSD-95 null generated specifically to avoid the residual
    functional truncated protein of earlier lines; used to define the
    AMPA-receptor and silent-synapse phenotype in hippocampal CA1.
  modeled_mechanisms:
  - target: Impaired Glutamate Receptor Anchoring at the Postsynaptic Density
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Establishes that PSD-95 loss reduces AMPA-receptor-mediated transmission
      and slows NMDA-receptor current decay through a greater GluN2B
      contribution.
    limitations: >-
      Homozygous null rather than heterozygous; the authors also found a
      substantial population of synapses unaffected by the deletion, so the
      receptor-anchoring deficit is synapse-specific rather than global.
    readouts:
    - name: AMPA receptor-mediated synaptic transmission
      target: Impaired Glutamate Receptor Anchoring at the Postsynaptic Density
      direction: DECREASED
      interpretation: Direct electrophysiological measure of failed AMPA-receptor anchoring.
      evidence:
      - reference: PMID:17148601
        reference_title: "Synapse-specific regulation of AMPA receptor function by PSD-95."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "We found that the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)subtype of glutamate receptor (AMPAR)-mediated synaptic transmission was reduced in these mice."
        explanation: The AMPA-receptor transmission measurement in the complete knockout.
    evidence:
    - reference: PMID:17148601
      reference_title: "Synapse-specific regulation of AMPA receptor function by PSD-95."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Together, these results suggest a synapse-specific role for PSD-95 in controlling synaptic function that is independent of spine morphology."
      explanation: >-
        The authors' summary, which both supports the model's relevance to
        receptor anchoring and flags that the effect is synapse-specific.
- name: PSD-95 PDZ1/PDZ2 ligand-binding-deficient knock-in mouse
  species: Mouse
  genotype: PSD-95 PDZ1/PDZ2 ligand binding-deficient cDNA knock-in (homozygous)
  publication: PMID:23268962
  description: >-
    A domain-specific model that leaves PSD-95 present but unable to bind
    ligands through PDZ1/PDZ2 — the supermodule that docks NMDA-receptor GluN2
    subunits and TARP-coupled AMPA receptors. It therefore isolates the
    receptor-anchoring function from PSD-95 abundance, and is the closest
    available model for the minority of human missense alleles that fall in the
    PDZ domains.
  modeled_mechanisms:
  - target: Impaired Glutamate Receptor Anchoring at the Postsynaptic Density
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Disabling PDZ1/2 ligand binding alone depletes PSD-95, PSD-93 and AMPA
      receptor subunits from the hippocampal postsynaptic density fraction.
    limitations: >-
      Homozygous, and models a ligand-binding defect rather than the reduced
      protein dose that most human alleles produce; the effect was also
      age- and subregion-dependent, so a single developmental snapshot can
      mislead.
    readouts:
    - name: PSD-fraction accumulation of PSD-95, PSD-93 and AMPA receptor subunits
      target: Impaired Glutamate Receptor Anchoring at the Postsynaptic Density
      direction: DECREASED
      interpretation: Biochemical measure of failed scaffold-dependent receptor anchoring.
      evidence:
      - reference: PMID:23268962
        reference_title: "Impaired synaptic clustering of postsynaptic density proteins and altered signal transmission in hippocampal neurons, and disrupted learning behavior in PDZ1 and PDZ2 ligand binding-deficient PSD-95 knockin mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The KI mice showed decreased accumulation of mutant PSD-95, PSD-93 and AMPA receptor subunits in the PSD fraction of the hippocampus."
        explanation: Reports the biochemical anchoring measurement in the knock-in.
    evidence:
    - reference: PMID:23268962
      reference_title: "Impaired synaptic clustering of postsynaptic density proteins and altered signal transmission in hippocampal neurons, and disrupted learning behavior in PDZ1 and PDZ2 ligand binding-deficient PSD-95 knockin mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These findings reveal that PSD-95 including its ligand binding of the PDZ1/2 domains controls the synaptic clustering of PSD-MAGUKs and AMPA receptors, which may have an essential role in regulating hippocampal synaptic transmission, plasticity, and hippocampus-dependent behavior."
      explanation: The authors' statement of what the model establishes about PSD-95-dependent receptor clustering.
  - target: Neurodevelopmental Phenotypic Output
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Produces abnormal anxiety-like behaviour and impaired spatial reference,
      working and remote memory — the cognitive and anxiety domains of the human
      phenotype.
    limitations: >-
      Rodent memory tasks are a distant proxy for human intellectual disability,
      and the model captures neither epilepsy nor the connective-tissue features.
    readouts:
    - name: Spatial reference, working and remote memory
      target: Neurodevelopmental Phenotypic Output
      direction: DECREASED
      interpretation: Cognitive correlate of the intellectual-disability phenotype.
      evidence:
      - reference: PMID:23268962
        reference_title: "Impaired synaptic clustering of postsynaptic density proteins and altered signal transmission in hippocampal neurons, and disrupted learning behavior in PDZ1 and PDZ2 ligand binding-deficient PSD-95 knockin mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "In a battery of behavioral tests, KI mice showed markedly abnormal anxiety-like behavior, impaired spatial reference and working memory, and impaired remote memory and pattern separation in fear conditioning test."
        explanation: Reports the behavioural battery results in the knock-in.
    evidence:
    - reference: PMID:23268962
      reference_title: "Impaired synaptic clustering of postsynaptic density proteins and altered signal transmission in hippocampal neurons, and disrupted learning behavior in PDZ1 and PDZ2 ligand binding-deficient PSD-95 knockin mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In a battery of behavioral tests, KI mice showed markedly abnormal anxiety-like behavior, impaired spatial reference and working memory, and impaired remote memory and pattern separation in fear conditioning test."
      explanation: Supports treating this model as informative for the cognitive and anxiety output of PSD-95 dysfunction.
experimental_models:
- name: AOUMEYi004-A patient-derived iPSC line (DLG4 c.2155A>T p.Arg719*)
  experimental_model_type: IPSC_DERIVED_MODEL
  description: >-
    Induced pluripotent stem cell line derived from a 37-year-old man with
    DLG4-related synaptopathy carrying a novel heterozygous de novo nonsense
    variant. The line has a normal karyotype, expresses pluripotency markers and
    differentiates into all three germ layers. It provides the first published
    human cellular substrate for modeling this disorder; no neuronal
    differentiation or disease phenotype is reported yet.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:42462545
  modeled_mechanisms:
  - target: DLG4 Loss of Function and PSD-95 Haploinsufficiency
    relationship: MEASURES
    fidelity: UNKNOWN
    description: >-
      Carries a patient heterozygous nonsense DLG4 allele in a human genetic
      background, the substrate required to measure the haploinsufficient state
      in human neurons.
    limitations: >-
      Characterized only at the pluripotent stage — karyotype, pluripotency
      markers and trilineage differentiation. No neuronal derivative, no PSD-95
      protein measurement and no synaptic phenotype has been reported, so the
      line does not yet demonstrate any disease mechanism.
    evidence:
    - reference: PMID:42462545
      reference_title: "Generation of a human induced pluripotent stem cell line (hiPSC) from a patient with DLG4-related synaptopathy (AOUMEYi004-A) and a novel heterozygous de novo nonsense DLG4 variant c.2155A > T p.(Arg719*)."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "We established the diagnosis in a 37-year-old man, by whole exome sequencing, heterozygous for the novel variant c.2155A > T; p.(Arg719*), then generated and characterized the iPSC line derived from the patient in order to model the neurodevelopmental disorder."
      explanation: >-
        Establishes the line's genotype and stated purpose; graded PARTIAL
        because the report characterizes the stem cell line, not a disease
        mechanism.
differential_diagnoses:
- name: SYNGAP1-Related Developmental and Epileptic Encephalopathy
  description: >-
    The closest mechanistic mimic: SynGAP binds the PDZ1-3 domains of PSD-95 and
    is itself a postsynaptic-density organizer, so its loss produces an
    overlapping intellectual-disability-plus-epilepsy synaptopathy.
  distinguishing_features:
  - >-
    Distinguished only by molecular testing; the clinical gestalt is not
    separable, which is why panel or exome sequencing rather than single-gene
    testing is recommended.
  evidence:
  - reference: PMID:35457207
    reference_title: "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "There is a general overlap between the clinical features of the genetic NDDs described in the previous section and DLG4-related synaptopathy."
    explanation: >-
      Supports the general claim that PSD-95-interactor disorders overlap
      clinically with DLG4-related synaptopathy and therefore require
      genotype-first discrimination. Note the scope limit: "the previous
      section" in the source covers the transmembrane PSD-95 partners, whereas
      SynGAP is discussed separately as a non-transmembrane partner, so this
      quote supports the overlap principle rather than the SYNGAP1 comparison
      specifically.
- name: Other DLG-MAGUK-related neurodevelopmental disorders (DLG2, DLG3)
  description: >-
    DLG2 variants have been linked to autism, schizophrenia and bipolar
    disorder, and truncating DLG3 variants to X-linked intellectual disability;
    all three paralogs encode postsynaptic-density MAGUKs.
  distinguishing_features:
  - >-
    DLG3 is X-linked, giving a different inheritance signature; otherwise
    discrimination is molecular.
  evidence:
  - reference: PMID:35457207
    reference_title: "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "DLG2 variants to ASD, schizophrenia, and bipolar disorder"
    explanation: Establishes the DLG2 paralog disorder that forms part of the immediate differential.
  - reference: PMID:35457207
    reference_title: "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "and truncating DLG3 variants to X-linked ID"
    explanation: >-
      Establishes the DLG3 paralog disorder and its X-linked inheritance, the
      one differentiating feature available without sequencing. This and the
      preceding item are two clauses of a single source sentence, split because
      the inline citation markers between them are stripped before
      substring matching and so cannot be quoted across.
- name: Marfan syndrome and other syndromic intellectual disability with marfanoid habitus
  description: >-
    DLG4 was discovered through a marfanoid-habitus-plus-intellectual-disability
    cohort, a clinically and genetically heterogeneous group of overlapping
    disorders.
  distinguishing_features:
  - >-
    Marfanoid habitus was found in only nine of 53 individuals in the founding
    DLG4 cohort and no distinct facial dysmorphism could be established, so a
    marfanoid presentation neither confirms nor excludes DLG4.
  evidence:
  - reference: PMID:29460436
    reference_title: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Marfanoid habitus (MH) combined with intellectual disability (ID) is a genetically and clinically heterogeneous group of overlapping disorders."
    explanation: States the heterogeneity of the differential group in which DLG4 was found.
discussions:
- discussion_id: hmm_homozygous_null_vs_human_haploinsufficiency
  prompt: >-
    The mechanistic literature that defines PSD-95 function — the shifted
    LTP/LTD frequency-response, the AMPA-receptor and silent-synapse phenotype,
    the autism-relevant behavioural profile — comes almost entirely from
    homozygous Dlg4-null or PSD-95-truncating mice, whereas every affected human
    is heterozygous. Does halving PSD-95 dose produce a proportionate,
    qualitatively similar synaptic phenotype, or does the near-complete loss
    studied in mice engage compensations and failure modes that a
    haploinsufficient synapse never reaches?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Impaired Glutamate Receptor Anchoring at the Postsynaptic Density
  - pathophysiology#Impaired Excitatory Synaptic Plasticity and Excitation-Inhibition Imbalance
  rationale: >-
    The gap is not hypothetical. Homozygous Dlg4 deletion adversely affects
    survival in mice, so the null phenotype is measured in a survivor-selected
    population with no human counterpart, and the complete knockout leaves a
    substantial subpopulation of synapses unaffected, implying a threshold
    rather than a linear dose-response. The one heterozygous patient-allele
    model published to date does reproduce reduced PSD-95 protein and cognitive
    and sleep phenotypes, but showed no spontaneous seizures despite epilepsy
    affecting about half of affected humans — the clearest signal so far that
    the heterozygous state is not simply a milder null.
  proposed_experiments:
  - experiment_id: dlg4_het_vs_null_synaptic_physiology
    name: Side-by-side heterozygous versus homozygous Dlg4 synaptic physiology
    description: >-
      Measure LTP/LTD frequency-response functions, AMPA/NMDA ratio and
      silent-synapse fraction in Dlg4+/- and Dlg4-/- hippocampus on one genetic
      background, to establish whether the half-dose state is a proportionate
      version of the null or a qualitatively different phenotype.
    decision_criterion: >-
      A monotonic, proportionate shift across genotypes would support
      extrapolating null-mouse mechanism to human haploinsufficiency; a
      threshold effect, with Dlg4+/- indistinguishable from wild type, would
      refute it.
  - experiment_id: dlg4_ipsc_neuron_synaptic_content
    name: Synaptic PSD-95 and AMPA-receptor content in patient iPSC-derived neurons
    description: >-
      Quantify PSD-95 protein per synapse and synaptic AMPA-receptor content in
      neurons differentiated from the patient-derived AOUMEYi004-A iPSC line
      against an isogenic corrected control, moving the receptor-anchoring claim
      into human cells at the correct heterozygous dose.
  - experiment_id: dlg4_knockin_provoked_seizure_threshold
    name: Provoked-seizure threshold in the Dlg4 V692Wfs*12/+ knock-in
    description: >-
      Test chemically or electrically provoked seizure susceptibility in the
      heterozygous patient-allele knock-in, since spontaneous seizures were
      absent but the seizure threshold was never probed.
    decision_criterion: >-
      A lowered provoked-seizure threshold would reconcile the model with the
      ~50% human epilepsy frequency; a normal threshold would sharpen the
      mismatch.
  evidence:
  - reference: PMID:17148601
    reference_title: "Synapse-specific regulation of AMPA receptor function by PSD-95."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We also observed that a significant population of synapses appeared unaffected by PSD-95 gene deletion, suggesting that the functional role of PSD-95 displays synapse-specificity."
    explanation: >-
      Even complete PSD-95 deletion spares many synapses, so extrapolating a
      null phenotype to a half-dose state is not straightforward.
  - reference: PMID:42565830
    reference_title: "A patient-derived mouse model reproduces molecular, neurological, and sleep symptoms of SHINE syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "While spontaneous seizures were not observed, future studies will test susceptibility to provoked seizures."
    explanation: >-
      The genotype-faithful heterozygous model misses the epilepsy arm, the
      concrete instance of the mismatch.
- discussion_id: gap_dlg4_genotype_phenotype
  prompt: >-
    Why do individuals carrying the same DLG4 variant differ so widely in
    severity, from mild intellectual disability without epilepsy to a regressive
    DEE-SWAS course? What determines whether a given individual develops
    sleep-activated epileptiform encephalopathy?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Sleep-Activated Epileptiform Encephalopathy (DEE-SWAS/ESES)
  - pathophysiology#Developmental Regression
  - pathophysiology#Neurodevelopmental Phenotypic Output
  rationale: >-
    The largest epilepsy-focused cohort could not identify a genotype-phenotype
    relationship even between individuals carrying identical DLG4 variants,
    which rules out variant identity as the explanation and points instead to
    modifier genes, developmental timing or stochastic circuit factors. Because
    DEE-SWAS is the single strongest predictor of regression, predicting who
    will develop it is the question with the most direct clinical consequence in
    this disorder.
  proposed_experiments:
  - experiment_id: dlg4_prospective_sleep_eeg_cohort
    name: Prospective longitudinal sleep-EEG cohort in DLG4 variant carriers
    description: >-
      Follow an unselected cohort of DLG4 variant carriers with serial sleep or
      24-hour EEG to establish the incidence, age window and clinical predictors
      of DEE-SWAS onset, which no retrospective series can supply.
    decision_criterion: >-
      Identification of a reproducible pre-DEE-SWAS EEG or clinical signature
      would make the regression risk predictable and the surveillance interval
      evidence-based.
  - experiment_id: dlg4_psd95_partner_modifier_screen
    name: Modifier screen in PSD-95 interaction partners
    description: >-
      Test whether variation in PSD-95 binding partners already implicated in
      epilepsy (LGI1-ADAM22, KCNA1/KCNA2, GRIN2A/GRIN2B) modifies the epilepsy
      phenotype among DLG4 carriers, the leading candidate explanation for
      within-variant phenotypic divergence.
  evidence:
  - reference: PMID:38135915
    reference_title: "Developmental epileptic encephalopathy in DLG4-related synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We could not identify a clear genotype-phenotype relationship even between individuals with the same DLG4 variants."
    explanation: Directly states the unexplained variability that defines this gap.
- discussion_id: gap_no_disease_modifying_strategy
  prompt: >-
    Every clinically advanced PSD-95-directed drug programme is designed to
    *disrupt* a PSD-95 interaction — nerinetide (Tat-NR2B9c) and the
    small-molecule PSD-95/nNOS disruptors developed for ischaemic stroke and
    neuropathic pain. For a haploinsufficiency disorder the required direction
    is the opposite: restore PSD-95 dose or function. Is there any tractable
    route to that — transcriptional upregulation of the remaining allele,
    targeted augmentation of a paralogous MAGUK, or stabilization of the
    residual protein — and in what developmental window would it have to act?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#DLG4 Loss of Function and PSD-95 Haploinsufficiency
  - pathophysiology#Impaired Functional Maturation of Excitatory Synapses
  rationale: >-
    The existence of a mature PSD-95-directed pharmacology is easy to mistake
    for a therapeutic head start for this disorder, and it is not one: those
    agents deliberately uncouple PSD-95 from nNOS to suppress excitotoxic nitric
    oxide, which in a PSD-95-deficient brain would push the lesion further in
    the direction it is already broken. The window question is equally
    unresolved — PSD-95 is described as essential during synaptogenesis and
    neurodevelopment, so a dose-restoring therapy started after that window may
    have nothing left to rescue, and no natural-history data yet define when the
    window closes.
  proposed_experiments:
  - experiment_id: dlg4_postnatal_restoration_window
    name: Conditional postnatal restoration of PSD-95 dose in a heterozygous model
    description: >-
      Restore PSD-95 expression at a series of postnatal ages in Dlg4+/- or
      Dlg4 V692Wfs*12/+ mice and test which synaptic, cognitive and sleep
      phenotypes remain reversible at each age.
    decision_criterion: >-
      Reversibility of a phenotype after the close of synaptogenesis would make
      dose-restoring therapy worth pursuing beyond infancy; strict
      developmental-window dependence would restrict it to a prenatal or
      early-infantile intervention.
  evidence:
  - reference: PMID:40712457
    reference_title: "Uncoupling toxic NO signaling: Progress, challenges, and therapeutic promise of disrupting the PSD-95/nNOS protein-protein interaction."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Collectively, the evidence positions PSD-95/nNOS disruption as a versatile, clinically achievable approach for mitigating excitotoxic and nociceptive pathology and sets the stage for first-in-class therapies that uncouple toxic NO signaling without silencing healthy synapses."
    explanation: >-
      Establishes that the mature PSD-95-directed pharmacology is aimed at
      disrupting a PSD-95 interaction for excitotoxicity and pain — the opposite
      direction from what a PSD-95 haploinsufficiency disorder needs.
  - reference: PMID:29169997
    reference_title: "PSD95: A synaptic protein implicated in schizophrenia or autism?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In this review, we describe the role of PSD-95 as an essential scaffolding protein during synaptogenesis and neurodevelopment."
    explanation: Supports the developmental-window concern that motivates the second half of this gap.
  - reference: PMID:37347881
    reference_title: "DLG4-Related Synaptopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There is no cure for DLG4-related synaptopathy."
    explanation: Confirms that no disease-modifying option currently exists, which is what makes this an open gap rather than a settled question.

📚

References & Deep Research

References

4

PMID:37347881

DLG4-Related Synaptopathy.

No top-level findings curated for this source.

PMID:33597769

DLG4-related synaptopathy: a new rare brain disorder.

No top-level findings curated for this source.

PMID:38135915

Developmental epileptic encephalopathy in DLG4-related synaptopathy.

No top-level findings curated for this source.

PMID:35457207

Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners.

No top-level findings curated for this source.

Deep Research

2

Claude Code ▸

DLG4-Related Synaptopathy: Comprehensive Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 26 citations 2026-08-19T08:45:45.832157

DLG4-Related Synaptopathy: Comprehensive Research Report

1. Disease Information

Overview

DLG4-related synaptopathy is a rare, autosomal dominant neurodevelopmental disorder caused by de novo (or, rarely, inherited) pathogenic variants in DLG4, the gene encoding postsynaptic density protein 95 (PSD-95), a master scaffolding protein of the glutamatergic postsynaptic density. The disorder was first delineated as a distinct clinical entity by Rodríguez-Palmero et al. (2021), who characterized 53 individuals and coined the term "DLG4-related synaptopathy" (Rodríguez-Palmero et al., 2021, Genet Med; PMID:33597769). The clinical picture is dominated by global developmental delay, intellectual disability (typically mild-to-moderate), autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and epilepsy in roughly half of patients, with a broader multisystem phenotype including hypotonia, movement disorders, sleep disturbance, ophthalmologic abnormalities, and marfanoid connective-tissue features in a subset.

Key Identifiers

Resource	Identifier
Gene (HGNC)	DLG4, HGNC:2903
OMIM Gene	*602887 – DISCS LARGE MAGUK SCAFFOLD PROTEIN 4; DLG4
OMIM Phenotype	#618793 – INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL DOMINANT 62 (MRD62) (OMIM:618793)
MONDO	MONDO:0032919 (label: "intellectual developmental disorder 62"; "DLG4-related synaptopathy" is an exact synonym, confirmed via OLS/MONDO)
GeneReviews	DLG4-Related Synaptopathy — NBK592682
Chromosomal locus	17p13.1
MedlinePlus Genetics	dlg4-related-synaptopathy

Synonyms / Alternative Names

SHINE syndrome (Sleep disturbances, Hypotonia, Intellectual disability, Neurologic disorder, Epilepsy) — the patient-advocacy-coined acronym used by the DLG4 SHINE Foundation
DLG4 synaptopathy
Intellectual developmental disorder, autosomal dominant 62 (MRD62/IDDA62)
Historically, before the syndrome was delineated, some cases were reported as "intellectual disability with marfanoid features" (Moutton et al., 2018)

Data Provenance

Information derives predominantly from aggregated, multi-center case-series/cohort resources rather than a single large EHR-based cohort, reflecting the disorder's rarity: - Rodríguez-Palmero et al. 2021 (n=53, GeneMatcher-assembled international cohort) - Moutton et al. 2018 (n=3, exome-sequencing trio discovery cohort; PMID study) - Kassabian et al. 2024, Epilepsia — expanded epilepsy-focused cohort (n=35: 23 newly reported + 12 updated) (Genotype-phenotype/DEE study) - Patient-registry/natural-history data curated by the DLG4 SHINE Foundation and Simons Searchlight, which together have identified ~100 individuals with pathogenic DLG4 variants - Individual case reports (deep intronic variant, Levy et al. 2024, Clin Genet; intellectual-regression case, 2023, Hum Genome Var)

2. Etiology

Disease Causal Factors

DLG4-related synaptopathy is a monogenic, genetically determined disorder. There is no known infectious, toxic, or purely environmental cause. The near-exclusive mechanism is haploinsufficiency of PSD-95 produced by heterozygous loss-of-function (or loss-of-function-equivalent) variants in DLG4.

Genetic Risk Factors

Causal variant class: predominantly protein-truncating variants (nonsense, frameshift, canonical splice-site) predicted to trigger nonsense-mediated decay or produce a non-functional truncated protein; missense variants are also reported (mechanism less certain, but generally interpreted as loss-of-function); rare deep intronic variants disrupting splicing have also been described (Levy et al., 2024, Clin Genet, DOI:10.1111/cge.14411).
Gene constraint: DLG4 is exceptionally intolerant of loss-of-function variation in the general population (pLI = 1; under gnomAD v4 conventions this corresponds to LOEUF well below the 0.6 constrained-gene threshold), consistent with haploinsufficiency as the pathogenic mechanism and explaining the complete absence of the variant class in population databases.
Inheritance: essentially always de novo; rare instances of transmission from a mosaic or (very rarely) mildly affected heterozygous parent are described in GeneReviews.
No modifier genes have yet been formally established, though interacting synaptic genes (SYNGAP1, other DLG-MAGUK family members) are biologically plausible candidates given shared pathway membership.

Environmental Risk Factors

None established. This is a purely genetic (Mendelian) disorder; no epidemiological association with parental age, toxin exposure, or perinatal factors has been reported in the literature to date.

Protective Factors

None identified in the literature — genetic or environmental. No protective variants or modifier alleles have been characterized.

Gene-Environment Interactions

Not established/not applicable given the disorder's fully penetrant monogenic basis; no CTD/PheGenI gene-environment interaction data exist for DLG4.

3. Phenotypes

Frequencies below are drawn primarily from the Rodríguez-Palmero et al. 2021 cohort (n=53) and the Kassabian et al. 2024 expanded/epilepsy cohort (n=35), as reported in GeneReviews and the primary literature.

Cognitive / Developmental (Symptoms)

Phenotype	Frequency	Notes	Suggested HPO term
Intellectual disability	~98–100%	Mild-to-moderate most common; severe/profound less common	HP:0001249 (Intellectual disability)
Global developmental delay	84%	Mean age of independent walking 20.7 months; first words 32.2 months	HP:0001263 (Global developmental delay)
Developmental regression	~40%	Motor and/or language regression; strongly associated with ESES/DEE-SWAS in the epilepsy subgroup	HP:0002376 (Developmental regression)
Autism spectrum disorder	56%	More frequent in individuals with moderate-severe ID	HP:0000729 (Autistic behavior)
ADHD	57%	More frequent with co-occurring ASD	HP:0007018 (Attention deficit hyperactivity disorder)
Anxiety	53%	Often triggered by loud sounds or separation	HP:0000739 (Anxiety)

Neurologic Signs

Phenotype	Frequency	Notes	HPO term
Epilepsy	53%	Generalized and/or focal; mean onset ~6 years	HP:0001250 (Seizure)
Developmental and epileptic encephalopathy with spike-wave activation in sleep (DEE-SWAS/ESES)	>25% of the epilepsy-cohort subset	Confirmed as part of the phenotypic spectrum by Kassabian et al. 2024; associated with regression in essentially all affected individuals	HP:0011200 (Ictal EEG abnormality) / HP:0012469 (Infantile spasms — n/a; use ESES-specific term where available)
Hypotonia	53% (up to ~60% in some series)	Central hypotonia	HP:0001252 (Hypotonia)
Movement disorder	46%	Stereotypies and ataxia most common; also dystonia and tremor	HP:0100022 (Abnormality of movement); HP:0000733 (Stereotypy); HP:0001251 (Ataxia); HP:0001332 (Dystonia); HP:0001337 (Tremor)
Migraine / headache	reported in a subset	—	HP:0002076 (Migraine)
Brain MRI abnormalities	~30%	Cerebral/cerebellar atrophy, thin corpus callosum, dysmorphic hippocampus	HP:0002119 (Ventriculomegaly), HP:0002079 (Hypoplasia of the corpus callosum), HP:0007360 (Aplasia/hypoplasia of the cerebellum)

Ophthalmologic Findings (Clinical Signs)

Phenotype	Frequency	Notes	HPO term
Overall ophthalmologic involvement	~50%	—	—
Strabismus	most common ocular finding	—	HP:0000486 (Strabismus)
Hyperopia	second most common	—	HP:0000540 (Hyperopia)
Nystagmus	—	—	HP:0000639 (Nystagmus)
Cortical visual impairment	less common	—	HP:0100704 (Cerebral visual impairment)

Musculoskeletal / Marfanoid Connective-Tissue Findings

Phenotype	Frequency	Notes	HPO term
Joint laxity	36.9%	—	HP:0001382 (Joint hypermobility)
Scoliosis	20%	—	HP:0002650 (Scoliosis)
Marfanoid habitus	~24%	Long face, slender build, long/thin fingers, pectus excavatum, high-arched palate	HP:0001519 (Disproportionate tall stature) / HP:0001166 (Arachnodactyly) / HP:0000276 (Long face) / HP:0000218 (High-palate) / HP:0000767 (Pectus excavatum)

This marfanoid connective-tissue association was the original phenotype through which DLG4 was first implicated in disease (Moutton et al. 2018, Clin Genet: "Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features," PMID study) — patients showed "mild-to-moderate intellectual disability with similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus)."

Sleep and Gastrointestinal

Phenotype	Frequency	Notes	HPO term
Sleep disturbance	45%	Sleep-onset and/or sleep-maintenance difficulty	HP:0002360 (Sleep disturbance)
Vomiting	29%	Often triggered by seizures, motion, or fatigue	HP:0002013 (Vomiting)
GERD / feeding difficulty	reported	—	HP:0002020 (Gastroesophageal reflux); HP:0011968 (Feeding difficulties)

Phenotype Characteristics

Onset: Early childhood — congenital/infantile-onset global developmental delay is the rule; epilepsy onset averages ~6 years.
Severity: Predominantly mild-to-moderate for ID, but a subset (particularly those with DEE-SWAS/ESES) show a more severe, regressive course.
Progression: Static/developmental-delay pattern in most; a regressive subgroup (~40%) exists, closely tied to the presence of DEE-SWAS/ESES epilepsy.
Frequency data source: Rodríguez-Palmero et al. 2021 (primary source of the percentages above) and Kassabian et al. 2024 (epilepsy/DEE-focused expansion).

Quality of Life Impact

No disease-specific EQ-5D/SF-36/PROMIS data have been published; QoL burden is inferred qualitatively from the combination of intellectual disability, autism, epilepsy (often drug-resistant in the DEE-SWAS subset), sleep disturbance, and anxiety — all of which are recognized independently as major contributors to caregiver burden and reduced adaptive functioning in neurodevelopmental disorders generally. The DLG4 SHINE Foundation registry/natural-history effort is intended in part to generate such data prospectively (DLG4 SHINE Natural History Studies).

4. Genetic/Molecular Information

Causal Gene

DLG4 (Discs Large MAGUK Scaffold Protein 4 / PSD-95), HGNC:2903, OMIM 602887, located at 17p13.1*.
Sole established causal gene for this disorder; OMIM phenotype #618793 (MRD62).

Pathogenic Variants

Gene/protein: DLG4/PSD-95; UniProt human PSD-95.
Variant classification: Per ACMG/AMP, essentially all reported variants are classified pathogenic/likely pathogenic; ClinVar contains multiple submissions (e.g., NM_001321075.3(DLG4):c.1592-1G>A associated with "Intellectual developmental disorder 62," ClinVar RCV001800207).
Variant type/class:
Protein-truncating variants (nonsense, frameshift, canonical ±1/±2 splice-site) — the large majority
Missense variants — reported, presumed loss-of-function but mechanism not experimentally proven in most cases
Silent (synonymous) and deep-intronic variants affecting splicing — rare but documented (Levy et al. 2024)
No gene-targeted deletions/duplications (CNVs) reported to date per GeneReviews
Allele frequency: DLG4 pathogenic/truncating variants are absent from population databases (gnomAD), consistent with the gene's extreme constraint (pLI = 1).
Somatic vs. germline: Disease-causing variants are germline (de novo in the proband in the great majority of cases); parental somatic/germline mosaicism has been documented in rare families, informing recurrence-risk counseling.
Functional consequence: Haploinsufficiency is the dominant proposed mechanism — loss of one functional DLG4 allele is not compensated by other DLG-MAGUK paralogs, based on both human genetic and mouse-knockout data.

Protein Domain Structure and Molecular Function

PSD-95 is an ~80 kDa MAGUK (membrane-associated guanylate kinase) family scaffolding protein with a modular domain architecture: three PDZ domains (PDZ1, PDZ2, PDZ3), one SH3 domain, and one catalytically-dead guanylate kinase (GK) domain (the SH3-GK forms a conserved "supermodule"). - PDZ1/PDZ2 cluster NMDA receptor GluN2 (NR2) subunits (via the C-terminal -ESDV/tSXV PDZ-binding motif), neuroligins, and inward-rectifier/voltage-gated K⁺ channels at the postsynaptic membrane. - PDZ3 binds distinct partners including neuroligins and CRIPT. - PSD-95 anchors AMPA receptors indirectly through auxiliary transmembrane AMPAR regulatory proteins (TARPs/stargazin), which bind PDZ domains and stabilize AMPARs at the postsynaptic density. - PSD-95-family MAGUKs are described as "essential for anchoring AMPA and NMDA receptor complexes at the postsynaptic density" (PNAS 2015). - PSD-95 interacts with, and helps organize, additional neurodevelopmental-disease-relevant partners including SYNGAP1 and other postsynaptic scaffolding/signaling molecules. - Acute inactivation of PSD-95 destabilizes AMPA receptors at hippocampal synapses, and PSD-95 is required for NMDA-receptor-dependent synaptic plasticity, directly linking loss of PSD-95 function to impaired excitatory synaptic signaling and plasticity.

Suggested GO terms: GO:0098794 (postsynapse); GO:0014069 (postsynaptic density); GO:0098839 (postsynaptic density membrane); GO:0035249 (synaptic transmission, glutamatergic); GO:0035255 (ionotropic glutamate receptor binding); GO:0007268 (chemical synaptic transmission); GO:0099054 (presynapse — for the paralogous Drosophila dlg data).

Other DLG-MAGUK Family Members (Relevant Comparators)

Vertebrates have four DLG-MAGUK paralogs: DLG1 (SAP97), DLG2 (PSD-93/chapsyn-110... note: DLG2 = SAP102/NE-dlg per some nomenclature), DLG3 (SAP102/NE-dlg or PSD-93 depending on source), and DLG4 (PSD-95). Each has its own associated neurodevelopmental disorder (DLG2- and DLG3-related intellectual disability/schizophrenia-risk phenotypes have been separately described), and the human genetic and phenotypic data indicate that these paralogs cannot functionally compensate for loss of PSD-95, explaining why DLG4 haploinsufficiency alone is sufficient to cause disease (see "Neurodevelopmental Disorders Associated with PSD-95 and Its Interaction Partners," PMID:35457207; PMC9025546).

Modifier Genes

None formally established.

Epigenetic Information / Chromosomal Abnormalities

No disease-specific epigenetic signature (DNA methylation episignature) has yet been published for DLG4-related synaptopathy (unlike some other NDD genes). No recurrent chromosomal abnormalities (aneuploidy, translocation) are implicated — this is a single-gene, sequence-variant disorder.

5. Environmental Information

Environmental/toxin factors: None identified as causal or exacerbating.
Lifestyle factors: Not applicable as a primary etiologic contributor; seizure and behavioral triggers (loud sounds, separation, motion, fatigue) are described as symptom modulators rather than disease causes.
Infectious agents: None implicated.

6. Mechanism / Pathophysiology

Causal Chain (Molecular → Cellular → Clinical)

Molecular trigger: Heterozygous loss-of-function (or splice-disrupting) variant in DLG4 → reduced/absent functional PSD-95 protein (haploinsufficiency), most consistent with nonsense-mediated decay of the truncated transcript or production of a non-functional truncated protein lacking key PDZ/SH3/GK domains.
Molecular consequence: Reduced PSD-95 scaffolding capacity at the excitatory postsynaptic density → impaired clustering/stabilization/trafficking of NMDA receptors (via PDZ1/PDZ2-NR2 interaction) and AMPA receptors (via TARP/stargazin-PDZ interactions) at the synaptic membrane.
Cellular consequence: Altered excitatory synapse number, maturation, and dendritic spine morphology; disrupted excitatory/inhibitory synaptic balance in cortical and hippocampal circuits; impaired NMDA-receptor-dependent long-term potentiation/synaptic plasticity (demonstrated directly in Dlg4-null mouse studies).
Circuit/systems consequence: Disrupted glutamatergic synaptic transmission and plasticity in cortex, hippocampus, and cerebellum — a synaptopathy — producing the core neurodevelopmental phenotype (global developmental delay, intellectual disability). In a subset, cortical hyperexcitability manifests as epilepsy, including the severe DEE-SWAS/ESES phenotype associated with active regression.
Clinical manifestation: Global developmental delay, intellectual disability, ASD/ADHD, epilepsy (including DEE-SWAS), movement disorder, hypotonia, and — via a less well-characterized connective-tissue mechanism — marfanoid skeletal/ophthalmologic features.

Cellular Processes and Cell Types Involved

Primary cell type: Glutamatergic (excitatory) neurons — cortical pyramidal neurons and hippocampal principal neurons (suggested CL term: CL:0000679, glutamatergic neuron; CL:0000598, pyramidal neuron).
Subcellular compartment: Postsynaptic density of the dendritic spine (suggested GO Cellular Component: GO:0014069 postsynaptic density; GO:0043197 dendritic spine).
Process: Synaptogenesis, excitatory synaptic maturation, receptor trafficking/anchoring, and activity-dependent synaptic plasticity (LTP/LTD).

Molecular/Systems Biology Evidence

Animal model data (mouse, Feyder et al. 2010): Dlg4⁻/⁻ (PSD-95 knockout) mice show increased repetitive behaviors, abnormal social/communicative behaviors, impaired motor coordination, and increased stress reactivity, together with subtle dysmorphology of amygdala dendritic spines and altered forebrain expression of synaptic genes — directly paralleling the human ASD/anxiety/motor phenotype ("Association of Mouse Dlg4 (PSD-95) Gene Deletion and Human DLG4 Gene Variation With Phenotypes Relevant to Autism Spectrum Disorders and Williams' Syndrome," PMID:20952458).
Invertebrate model data (Drosophila): The dlg (discs-large) tumor suppressor gene — the invertebrate DLG-MAGUK ortholog — is required for normal synapse structure at the glutamatergic neuromuscular junction and regulates postsynaptic glutamate receptor subunit composition and structural synaptic plasticity, establishing deep evolutionary conservation of the DLG-MAGUK synaptic scaffolding function across the animal kingdom (PMC545058; PMC4658212).
In vitro/biochemical data: Acute inactivation of PSD-95 destabilizes AMPA receptors at hippocampal synapses (PMC3546964); PDZ1/PDZ2 ligand-binding-deficient PSD-95 knock-in mice show impaired synaptic clustering of PSD proteins, altered signal transmission, and disrupted learning behavior — directly modeling domain-specific loss of function (PMC3575367).

Genotype-Phenotype Correlation

No robust variant-position-specific genotype-phenotype correlation has been firmly established; the disorder is thought to be driven predominantly by simple haploinsufficiency regardless of the precise truncating-variant location, though a dedicated genotype-phenotype study is an active area of ongoing collaborative research (ERN-ITHACA "Genotype-phenotype characterization of DLG4-related synaptopathy" call for collaboration, and the Kassabian et al. 2024 DEE-focused cohort).

7. Anatomical Structures Affected

Organ Level

Primary organ: Brain (central nervous system) — cortex, hippocampus, cerebellum, corpus callosum (per neuroimaging findings in ~30% of patients).
Secondary/associated systems:
Musculoskeletal system (joint laxity, scoliosis, marfanoid habitus)
Visual system/eye (strabismus, hyperopia, nystagmus, cortical visual impairment)
Gastrointestinal system (vomiting, GERD/feeding difficulty)
Sleep/circadian system

Suggested UBERON terms: UBERON:0000955 (brain); UBERON:0001950 (neocortex); UBERON:0002421 (hippocampal formation); UBERON:0002037 (cerebellum); UBERON:0002336 (corpus callosum); UBERON:0000970 (eye); UBERON:0001474 (bone element, for scoliosis/skeletal features).

Tissue and Cell Level

Glutamatergic excitatory neuronal populations in cerebral cortex and hippocampus (CL:0000679); cerebellar Purkinje/granule cell circuits secondarily implicated via cerebellar atrophy findings.

Subcellular Level

Postsynaptic density / dendritic spine of the excitatory glutamatergic synapse (GO:0014069 postsynaptic density; GO:0043197 dendritic spine; GO:0098794 postsynapse).

Localization

Diffuse/bilateral CNS involvement (no clear lateralization); neuroimaging abnormalities when present are typically bilateral/symmetric (cerebral/cerebellar atrophy, thin corpus callosum).

8. Temporal Development

Onset

Age of onset: Congenital/early-infantile onset of developmental delay is typical (recognizable within the first 1–2 years of life); mean age of independent walking 20.7 months and first words at 32.2 months indicate onset well within infancy/early childhood.
Epilepsy onset: Mean age ~6 years, though it can occur earlier or later.
Onset pattern: Predominantly insidious/developmental (delay from early infancy) rather than acute; a distinct regressive subpattern occurs in association with DEE-SWAS/ESES epilepsy.

Progression

Course: Generally a static-to-slowly-evolving neurodevelopmental disorder in the majority; however, ~40% experience frank developmental regression (motor and/or language), which is closely tied to the DEE-SWAS/ESES epileptic subtype — in the Kassabian et al. 2024 cohort, regression occurred in essentially all individuals with ESES/DEE-SWAS and in some without it.
Disease duration: Chronic, lifelong; documented survival into adulthood (oldest reported patient in the Kassabian cohort was 61 years old; another report described a patient at age 47), suggesting normal or near-normal life expectancy, though the adult phenotype is likely underrecognized due to historically limited genetic testing in adults.

Patterns

Remission: No spontaneous remission of the underlying neurodevelopmental phenotype; seizures in the DEE-SWAS subgroup can show EEG/clinical improvement with targeted anti-epileptic treatment (e.g., corticosteroids or other ESES-directed regimens), consistent with general DEE-SWAS management principles.
Critical periods: The DEE-SWAS/ESES window (typically preschool-to-school age) represents a critical period of vulnerability during which active regression occurs — early recognition and EEG monitoring (including overnight/24-hour EEG) during this window is emphasized in management recommendations.

9. Inheritance and Population

Epidemiology

Prevalence: Not formally established (no population-based prevalence study); the disorder is characterized as rare. As of recent counts, ~100 individuals worldwide have been identified with a confirmed pathogenic DLG4 variant through combined clinical literature and the DLG4 SHINE Foundation/Simons Searchlight registries, with 53 formally published in the founding cohort study and 35 in the more recent Kassabian et al. 2024 expanded/epilepsy-focused series.
Incidence: Not established.

Inheritance Pattern

Autosomal dominant, virtually always due to a de novo pathogenic variant.
Penetrance: Appears to be complete (or very high) in reported cases — no confirmed asymptomatic carriers of a clearly pathogenic truncating variant have been well documented, though ascertainment bias (family members generally tested only when clinically indicated) limits certainty.
Expressivity: Variable — phenotypic severity ranges from mild ID without epilepsy to a severe DEE-SWAS/regressive phenotype, without a clear genotype-driving explanation established to date.
Genetic anticipation: Not applicable/not reported (not a repeat-expansion disorder).
Germline mosaicism: Documented as a rare cause of recurrence in siblings of an apparently de novo proband; GeneReviews notes sibling recurrence risk is "slightly above the general population risk" for this reason.
Founder effects: None reported.
Consanguinity: Not a relevant risk factor given the dominant, de novo mechanism.
Carrier frequency: Not applicable in the traditional sense (dominant, not typically "carried" asymptomatically); population database absence of truncating variants (gnomAD, pLI=1) confirms these variants are not tolerated even in single copy in unaffected individuals.

Population Demographics

Affected populations: No ethnic/geographic predilection has been reported; cases have been identified across multiple continents/cohorts (European, North American, and other GeneMatcher-connected centers).
Sex ratio: Approximately balanced — the Kassabian et al. 2024 cohort reported a male:female ratio of 19:16, consistent with no strong sex bias, as expected for an autosomal (not X-linked) disorder.
Age distribution: Wide range reported — from infancy through at least the 6th–7th decade of life (Kassabian cohort median age at inclusion 13 years, range 1.7–61 years).

10. Diagnostics

Clinical Tests

No pathognomonic laboratory biomarker, imaging finding, or biopsy result exists; the phenotype alone is not sufficiently specific to establish the diagnosis — GeneReviews explicitly states molecular testing is required.
Brain MRI: Recommended as part of the diagnostic work-up in patients presenting with developmental delay/ID; abnormal in ~30% (cerebral/cerebellar atrophy, corpus callosum thinning, hippocampal dysmorphism), but findings are nonspecific.
EEG: Important given the ~53% epilepsy prevalence and the specific DEE-SWAS/ESES subtype; overnight/24-hour EEG is recommended for individuals with significant cognitive delay, regression, or clinical suspicion of subclinical epileptiform activity.
Ophthalmologic exam: Recommended given the ~50% prevalence of ocular findings (strabismus, hyperopia, nystagmus).

Genetic Testing

Recommended approach: A multigene panel for intellectual disability/epilepsy, or comprehensive genomic testing (exome or genome sequencing) — GeneReviews explicitly states that single-gene DLG4 testing is rarely useful and typically not recommended as a first-tier test, given the lack of a specific enough clinical gestalt.
Sequence analysis: Detects the full spectrum of reported variant types (missense, nonsense, small indels, canonical splice-site variants).
Gene-targeted deletion/duplication analysis (CNV testing): No pathogenic CNVs identified to date, so this modality has low diagnostic yield but may still be included in standard panels/exome CNV-calling pipelines.
RNA testing (RT-PCR/RNA-seq): Should be considered for variants of uncertain splicing consequence, including synonymous and deep-intronic variants (as demonstrated by the Levy et al. 2024 deep-intronic case).
Trio (parent-child) sequencing is valuable both diagnostically (confirming de novo status supports pathogenicity) and for recurrence-risk counseling.

Clinical Diagnostic Criteria

No formal consensus clinical diagnostic criteria (DSM/ICD-style) exist; diagnosis is genotype-first (molecular confirmation) combined with a compatible phenotype.

Differential Diagnosis

Because features (ID, ASD, epilepsy, hypotonia) are non-specific, the differential includes other genetic synaptopathies and syndromic neurodevelopmental disorders, most notably: - SYNGAP1-related intellectual disability (explicitly noted as an overlapping synaptopathy differential in GeneReviews, given the direct PSD-95–SynGAP1 interaction) - Other DLG-MAGUK-family-related disorders (DLG2-, DLG3-related NDDs) - Other causes of syndromic ID with marfanoid habitus (e.g., FBN1-related Marfan syndrome itself, Lujan-Fryns syndrome, and — per a 2024 case report — PCDHGA5-related NDD) must be distinguished from the connective-tissue-overlap presentation.

Screening

No population-based or newborn screening program exists for this ultra-rare disorder; identification occurs via clinical genetic testing triggered by developmental delay/ID/epilepsy work-up.

11. Outcome/Prognosis

Survival and Mortality

No formal survival statistics (5-/10-year survival, standardized mortality ratio) have been published.
Survival into adulthood is well documented (oldest reported case 61 years in the Kassabian 2024 cohort; another individual reported at age 47), suggesting the disorder is not associated with markedly shortened life expectancy in the majority of cases, though this is likely an underestimate of the true adult population given historical underdiagnosis.

Morbidity and Functional Outcomes

Functional impact: Lifelong intellectual disability (typically mild-to-moderate) with need for ongoing developmental/educational support; motor impairment (hypotonia, movement disorder) contributes to functional morbidity; a substantial subset experiences developmental regression.
Quality of life: No validated disease-specific QoL instrument data published; burden is inferred from the combination of ID + ASD + epilepsy + sleep disturbance + anxiety, all independently associated with reduced QoL in neurodevelopmental disorders broadly.

Disease Course / Complications

Complications: Refractory or difficult-to-control epilepsy (notably DEE-SWAS/ESES) is the most clinically significant complication, directly associated with cognitive/language regression; scoliosis requiring orthopedic monitoring; ophthalmologic complications from untreated strabismus/refractive error; feeding/GI complications (GERD, vomiting).
Recovery potential: With early intervention (developmental therapies, seizure control), stabilization of function is achievable; the regressive DEE-SWAS phenotype in particular may show partial recovery with EEG-directed antiepileptic/anti-inflammatory treatment (per general DEE-SWAS management principles extrapolated to this disorder, as GeneReviews and Kassabian et al. discuss).

Prognostic Factors

Presence of DEE-SWAS/ESES epilepsy appears to be the strongest identified prognostic factor for regression/worse cognitive trajectory.
Severity of baseline ID correlates with likelihood of co-occurring ASD (moderate-severe ID more often associated with ASD).
No molecular/biomarker-based prognostic classifier has yet been validated.

12. Treatment

There is no disease-modifying or curative therapy; management is entirely supportive and symptom-directed, per GeneReviews consensus recommendations.

Pharmacotherapy

Anti-seizure medications (ASMs): Standard epilepsy pharmacotherapy tailored to seizure type; for the DEE-SWAS/ESES subtype, ESES-directed regimens (e.g., corticosteroids/ACTH, or specific ASMs used for encephalopathy with spike-wave activation in sleep) may be considered, following general DEE-SWAS treatment principles rather than DLG4-specific trial data.
Migraine therapy: Standard migraine treatment as clinically indicated.
Sleep pharmacotherapy: Reserved for refractory sleep disturbance after behavioral measures.
No pharmacogenomic (PharmGKB/CPIC) guidance specific to DLG4 variants exists.
Suggested NCIT term: NCIT:C15986 (Pharmacotherapy), with therapeutic_agent specifying individual anti-seizure medications as used case-by-case.

Advanced/Experimental Therapeutics

No gene therapy, ASO, siRNA, or targeted molecular therapy has been reported or is in registered clinical trials specifically for DLG4-related synaptopathy as of current literature.
No NCT-registered interventional trials specific to DLG4 were identified via available search; research activity is centered on natural history / registry studies rather than therapeutic trials (see below).

Non-Pharmacologic / Supportive Care

Domain	Intervention	Suggested NCIT term
Developmental	Early intervention (birth–3 years), developmental preschool (3–5 years), individualized education plan (IEP)	NCIT:C49236 (Therapeutic Procedure)
Motor	Physical therapy, occupational therapy, adaptive devices	NCIT:C15302 (Physical Therapy)
Behavioral/ASD	Formal autism evaluation; Applied Behavior Analysis (ABA) therapy; ADHD/anxiety screening and management	NCIT:C15747 (Supportive Care)
Orthopedic	Monitoring/management of scoliosis; surgical referral if progressive	NCIT:C16186 (Orthopedic Surgical Procedure), as needed
Ophthalmologic	Annual ophthalmologic evaluation; correction of refractive error; low vision services	—
GI	Standard management of feeding difficulty, GERD, vomiting	—
Genetic	Genetic counseling for families	NCIT:C15240 (Genetic Counseling)

Treatment Strategy / Algorithms

Management follows a multidisciplinary surveillance-and-support algorithm as codified in GeneReviews: - At every visit: assess for seizures, developmental progress, behavioral concerns (post-infancy), mobility/self-help skills, and sleep disturbance. - Annually: ophthalmologic evaluation; consider 24-hour EEG based on clinical indicators (regression, cognitive plateau, suspected subclinical seizures).

Experimental/Research Infrastructure

The DLG4 SHINE Foundation (patient advocacy organization) coordinates natural history studies, a patient registry, and biospecimen collection in partnership with Simons Searchlight and other research groups, explicitly framed as the necessary first step toward future targeted-treatment development ("Finding Treatment of DLG4 Synaptopathy Starts with Registry," dlg4shine.org).

13. Prevention

Given the disorder's near-exclusively de novo genetic origin, classical primary/secondary/tertiary prevention paradigms (vaccination, lifestyle modification, screening programs) are not applicable in the traditional sense.

Primary prevention: Not possible to prevent de novo germline mutation; population carrier screening is not relevant given the de novo mechanism.
Secondary prevention (reproductive counseling):
Genetic counseling is central: recurrence risk for future pregnancies of parents of an affected (apparently de novo) proband is low but not zero (above general population risk) due to the possibility of parental germline mosaicism; recurrence risk rises to 50% if a parent is confirmed to carry the variant (germline or somatic-germline mosaic, or, rarely, is mildly affected).
Prenatal diagnosis and preimplantation genetic testing (PGT) are available once the familial pathogenic variant is identified, allowing informed reproductive decision-making in subsequent pregnancies.
Tertiary prevention: Aimed at reducing complications of the established disease — e.g., early EEG surveillance to catch DEE-SWAS/ESES before extensive regression occurs, annual ophthalmologic screening to prevent amblyopia from untreated strabismus/refractive error, and scoliosis monitoring to enable early orthopedic intervention.
Public health / behavioral / immunization strategies: Not applicable — this is not an infectious, environmental, or lifestyle-driven condition.

14. Other Species / Natural Disease

Taxonomy: No naturally occurring veterinary/companion-animal disease attributable to spontaneous Dlg4 mutation has been reported in OMIA or the veterinary literature; DLG4-related synaptopathy is a human-specific clinical entity as currently documented.
Orthologous gene: Dlg4 is conserved across vertebrates (mouse Dlg4, NCBI Gene) and has clear orthologs in zebrafish (dlg4, Gene ID referenced in GeneCards) and in Drosophila (dlg, "discs large," the founding member of the gene family, originally identified as a tumor suppressor).
Comparative biology: The DLG-MAGUK gene family (dlg1–dlg4 in vertebrates; single dlg in Drosophila) shows deep evolutionary conservation of function in organizing glutamatergic postsynaptic signaling complexes — from the Drosophila neuromuscular junction through to the mammalian cortical excitatory synapse — underscoring that PSD-95's core synaptic scaffolding role, and its vulnerability to haploinsufficiency-driven disease, is an ancient and conserved biological function.
Zoonotic potential: Not applicable (not an infectious disease).

15. Model Organisms

Mammalian Models

Mouse — Dlg4⁻/⁻ (PSD-95 knockout) germline knockout: The best-characterized model. Recapitulates behavioral features relevant to human ASD/anxiety phenotype: increased repetitive behaviors, abnormal social and communication behaviors, impaired motor coordination, and increased stress reactivity; molecular/anatomical correlates include subtle dysmorphology of amygdala dendritic spines and altered forebrain expression of synaptic genes (PMID:20952458; American Journal of Psychiatry, 2010).
Mouse — PDZ1/PDZ2 ligand-binding-deficient PSD-95 knock-in: A domain-specific model showing impaired synaptic clustering of postsynaptic density proteins, altered synaptic signal transmission, and disrupted learning behavior in hippocampal neurons — directly informative for the mechanistic consequence of PDZ-domain-disrupting human variants (PMC3575367).
Model characteristics: These murine models show reasonably good face validity for the core behavioral domains of the human disease (autism-relevant behaviors, motor coordination deficits) but, as a complete knockout, represent a more severe loss-of-function state than the heterozygous human condition; the PDZ-domain-specific knock-in more precisely models a partial/domain-restricted functional loss.
Model limitations: Homozygous Dlg4⁻/⁻ mice do not directly model the human heterozygous haploinsufficiency state (most human patients are heterozygous), so heterozygous Dlg4⁺/⁻ mice would in principle be a more disease-relevant model; specific epilepsy/DEE-SWAS phenotypes and the marfanoid connective-tissue phenotype observed in humans have not been reported as recapitulated in existing mouse models.

Invertebrate Models

Drosophila — dlg (discs-large) mutants: The Drosophila glutamatergic neuromuscular junction (NMJ) model demonstrates that dlg is required for normal synapse structure, clusters postsynaptic glutamate receptor subunit composition, and mediates structural synaptic plasticity during postsynaptic target growth (PMC545058; PMC4658212). This provides a genetically tractable system for dissecting fundamental DLG-MAGUK synaptic scaffolding function, though it models the ancestral single-paralog system rather than the vertebrate-specific compensatory context.

Cellular / iPSC Models

No published human iPSC-derived neuron model specific to DLG4 patient variants was identified in the current literature search; this represents an identified research gap, and the DLG4 SHINE Foundation biospecimen-collection effort may support development of such models in the future.

Resources

Mouse Genome Informatics (MGI) — Dlg4 allele records
ZFIN — zebrafish dlg4 records
FlyBase — Drosophila dlg records
International Mouse Phenotyping Consortium (IMPC) — potential source of additional Dlg4 conditional/heterozygous allele phenotyping data (not specifically reviewed here)

Summary of Key Evidence Gaps for Curation

Genotype-phenotype correlation remains unresolved — an active area of ongoing collaborative study (ERN-ITHACA call for collaboration; Kassabian et al. 2024).
No approved or trial-stage disease-modifying therapy exists; management is entirely supportive.
Heterozygous (haploinsufficient) mouse models more precisely matching the human genetic state, and human iPSC-neuron models, are not yet well represented in the published literature — an important caveat for any HUMAN_MODEL_MISMATCH discussion, since the best-characterized mouse data (Feyder et al. 2010) derive from a full knockout rather than a heterozygous model.
Formal prevalence/incidence figures and validated QoL instrument data are not yet available — current numbers (~100 individuals identified) reflect registry/cohort ascertainment rather than population-based epidemiology.
DEE-SWAS/ESES epilepsy subtype is the most clinically consequential and best-recently-characterized complication (Kassabian et al. 2024) and should be modeled as a distinct, evidence-rich pathophysiology/phenotype node given its strong association with developmental regression.

Sources

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	14
Resolved	13
Unresolved (possible confabulation)	1
Unverifiable	0
Quoted claims checked	4
Quoted claims found in source	3
Quoted claims not found in source	1
References weighed for topical relevance	13
On topic	8
Off topic	2

Unresolved references

These identifiers did not resolve to a record and may be fabricated. A lookup that failed for transport reasons is indistinguishable from one that failed because the record does not exist, so spot-check before acting on them:

DOI:10.1111/cge.14411](https://onlinelibrary.wiley.com/doi/full/10.1111/cge.14411 (1 mention) - Identifier did not resolve to a record

Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

DOI:10.1073/pnas.1517045112 (abstract only): "essential for anchoring AMPA and NMDA receptor complexes at the postsynaptic density"
closest text in source: "Significance The postsynaptic density (PSD) at the glutamatergic excitatory synapse is a macromolecular machine that underlies synaptic transmission and information storage"

References that may not be about this subject

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

DOI:10.1073/pnas.1517045112 (3 mentions) - PSD-95 family MAGUKs are essential for anchoring AMPA and NMDA receptor complexes at the postsynaptic density
shared terms: psd-95, postsynaptic
PMC:PMC3546964 (5 mentions) - Acute inactivation of PSD-95 destabilizes AMPA receptors at hippocampal synapses.
shared terms: psd-95, postsynaptic

Weighed against this report's own most characteristic terms: disorder, dlg4, epilepsy, phenotype, developmental, variant, dee-swas, genetic, gene, synaptopathy, intellectual, psd-95, clinical, regression, eses, kassabian, identified, disability, postsynaptic, associated.

OpenScientist ▸

Key Findings

openscientist-autonomous 13 citations 2026-08-19T08:58:15.880456

Key Findings

Finding 1 — Definition and core identity of the disorder

DLG4-related synaptopathy is a rare autosomal-dominant neurodevelopmental disorder caused by de novo variants in DLG4/PSD-95. It was defined by the landmark cohort of Rodríguez-Palmero and colleagues, who reported "the clinical and genetic features of 53 patients (42 previously unpublished) with DLG4 variants" and proposed "we designate this group of disorders as DLG4-related synaptopathy" [PMID: 33597769]. Of the 45 different DLG4 variants they identified, "39 were predicted to lead to loss of protein function and the majority occurred de novo" [PMID: 33597769].

The disorder maps to the following identifiers: OMIM 618793 (Intellectual developmental disorder, autosomal dominant 62 / IDD62), MONDO:0032919, MedGen/UMLS C5394083, DOID:0061035, and GARD 0025775. The causal gene DLG4 is HGNC:2903, NCBI Gene 1742, UniProt P78352, located at chromosome 17p13.1, and encodes PSD-95.

Finding 2 — Core clinical phenotype

The predominant clinical features are early-onset global developmental delay, intellectual disability, ASD, and ADHD. The original cohort found that "the clinical picture was predominated by early onset global developmental delay, intellectual disability, autism spectrum disorder, and attention deficit-hyperactivity disorder, all of which point to a brain disorder" [PMID: 33597769]. Additional features include hypotonia, sleep disturbance, movement disorders, strabismus, scoliosis, and joint hypermobility. Notably, the study refined an earlier claim: "Marfanoid habitus, which was previously suggested to be a characteristic feature of DLG4-related phenotypes, was found in only nine individuals" (9/53), and there was no distinct facial dysmorphism.

Epilepsy is a major feature. A dedicated epilepsy study noted that "even though epilepsy is present in 50% of the individuals, it has not been investigated in detail" and reported that "encephalopathy related to status epilepticus during slow-wave sleep (ESES)/developmental epileptic encephalopathy with spike-wave activation during sleep (DEE-SWAS) was diagnosed in >25% of the individuals" [PMID: 38135915]. Focal seizures were the most common type.

Suggested HPO terms: Intellectual disability (HP:0001249), Seizure (HP:0001250), Autistic behavior (HP:0000729), Attention deficit hyperactivity disorder (HP:0007018), Muscular hypotonia (HP:0001252), Sleep disturbance (HP:0002360), Strabismus (HP:0000486), Scoliosis (HP:0002650), Joint hypermobility (HP:0001382), Global developmental delay (HP:0001263), Cerebellar vermis atrophy (HP:0006855).

Finding 3 — Molecular mechanism (PSD-95 scaffolding of glutamate receptors)

PSD-95 scaffolds NMDA and AMPA receptors at the excitatory postsynaptic density; its loss impairs synaptic maturation and plasticity. As summarized in a review, "postsynaptic density protein-95 (PSD-95) is a major regulator of synaptic maturation by interacting, stabilizing and trafficking N-methyl-d-aspartic acid receptors (NMDARs) and α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptors (AMPARs) to the postsynaptic membrane" [PMID: 29169997]. The original disease paper states that "postsynaptic density protein-95 (PSD-95), encoded by DLG4, regulates excitatory synaptic function in the brain" [PMID: 33597769].

At the molecular level, protein-truncating variants and at least one deep-intronic variant act by reducing functional protein. A patient-derived DLG4 V692Wfs12 transcript illustrates the mechanism: "the mutant transcript escapes nonsense-mediated decay but results in reduced PSD-95 protein expression"* [PMID: 42565830], demonstrating that even a transcript that evades NMD ultimately yields reduced PSD-95 protein — consistent with haploinsufficiency.

Suggested GO/CL terms: postsynaptic density (GO:0014069), dendritic spine (GO:0043197), glutamatergic synapse (GO:0098978), regulation of synaptic plasticity (GO:0048167); glutamatergic neuron (CL:0000679).

Finding 4 — Extreme loss-of-function intolerance supports haploinsufficiency

DLG4 is among the most constrained genes in the human genome. gnomAD constraint metrics for DLG4 (ENSG00000132535, chr17:7,187,187–7,219,841, GRCh38) show pLI = 1.0; observed LoF variants = 7 versus expected 93.8 (oe_lof = 0.075, 90% CI 0.042–0.140, i.e. LOEUF = 0.14); LoF Z = 7.60; missense Z = 6.06 (oe_mis = 0.55). This extreme depletion of loss-of-function variation in the general population is exactly the population-genetic signature expected for a haploinsufficient, dominant neurodevelopmental gene, and it strongly corroborates the mechanistic model that a single loss-of-function allele is sufficient to cause disease.

Finding 5 — Model organisms recapitulate cognitive, behavioral, and synaptic-plasticity deficits

Multiple mouse models and patient-derived cellular models support the disease mechanism:

PSD-95-null mice show paradoxically enhanced hippocampal LTP with severely impaired learning: "in mutant mice lacking PSD-95, the frequency function of NMDA-dependent LTP and LTD is shifted to produce strikingly enhanced LTP at different frequencies of synaptic stimulation" and "this frequency shift is accompanied by severely impaired spatial learning" [PMID: 9853749].
PDZ1/2 ligand-binding-deficient PSD-95 knock-in mice show reduced PSD accumulation of PSD-95/PSD-93/AMPARs, abnormal anxiety, and impaired spatial, working, and remote memory [PMID: 23268962].
Dlg4−/− mice model ASD-relevant behavior: they "showed increased repetitive behaviors, abnormal communication and social behaviors, impaired motor coordination, and increased stress reactivity and anxiety-related responses" [PMID: 20952458].
A patient-derived Dlg4 V692Wfs*12/+ knock-in mouse faithfully models the human disorder: "Dlg4V692Wfs12/+ mice recapitulate several hallmark features of SHINE syndrome, often in a sex-specific manner"* — including reduced PSD-95, learning/cognitive-flexibility deficits (male-biased), and sleep abnormalities [PMID: 42565830].
A patient iPSC line (AOUMEYi004-A) carrying c.2155A>T p.(Arg719*) was established for in vitro disease modeling [PMID: 42462545].

Finding 6 — Management is supportive; no disease-modifying therapy

There is no targeted or curative therapy. Care is symptom-directed: antiseizure medications for epilepsy, developmental/rehabilitative therapies, and management of sleep and behavior. Antiseizure medication response was assessed retrospectively across 35 patients with epilepsy, with variable response and frequent refractoriness in the ESES/DEE-SWAS forms [PMID: 38135915]. For treatment-resistant psychosis, an adolescent with SHINE syndrome and early-onset schizophrenia/catatonia improved markedly on clozapine: "after failing three antipsychotic drug treatments, the patient was started on clozapine, which resulted in significant improvements in positive and negative symptoms" [PMID: 37386468]. Experimental PSD-95-directed agents (e.g., nerinetide/Tat-NR2B9c, which disrupt the PSD-95/nNOS interaction) exist but are being developed for stroke and pain, not for this disorder [PMID: 40712457].

Finding 7 — Protein architecture and variant spectrum

PSD-95 (UniProt P78352, 724 aa) is a MAGUK with a characteristic modular architecture: three PDZ domains (PDZ1 aa 65–151, PDZ2 aa 160–246, PDZ3 aa 313–393), an SH3 domain (aa 428–498), and a guanylate kinase-like (GK) domain (aa 534–709), plus an N-terminal disordered region (aa 15–35). Twenty-two experimental PDB structures have been deposited. Pathogenic variants span the entire gene and include nonsense/frameshift (e.g., c.2155A>T p.Arg719; c.2074_2075 frameshift p.Val692Trpfs12 in the GK domain), splice-site, a deep-intronic pseudoexon variant (c.2105+235C>T), and six missense variants. "The six missense variants identified were suggested to lead to structural or functional changes by protein modeling studies" [PMID: 33597769], and across cohorts "the majority [are] predicted to be protein-truncating" [PMID: 37525972].

Finding 8 — Diagnosis, inheritance, and epidemiology

Diagnosis is molecular, established by clinical whole-exome or whole-genome sequencing identifying a heterozygous DLG4 variant; RNA/functional studies resolve splice and deep-intronic variants. In the landmark cohort, most cases were simplex/de novo: "the majority occurred de novo (four with unknown origin)" [PMID: 33597769]. A deep-intronic variant was "identified using whole genome sequencing" [PMID: 37525972], underscoring the value of WGS plus RNA studies when exome sequencing is unrevealing. Brain MRI and EEG (including sleep EEG/video-polygraphy for ESES/DEE-SWAS) are used for phenotyping: "data on awake and sleep electroencephalography (EEG) and/or video-polygraphy and brain magnetic resonance imaging were collected" [PMID: 38135915]. The disorder is ultra-rare (~53 patients in the defining 2021 series, with additional case reports since); no population prevalence or incidence has been established, and it is under-ascertained, including late/adolescent diagnoses [PMID: 40444229].

Finding 9 — Anatomy and temporal course

This is a brain-centered disorder affecting glutamatergic excitatory synapses. PSD-95 is "an essential scaffolding protein during synaptogenesis and neurodevelopment" [PMID: 29169997], localizing to the postsynaptic density of excitatory synapses. Primary organ: brain/nervous system; cell type: glutamatergic neurons (CL:0000679); subcellular compartment: postsynaptic density/dendritic spine (GO:0014069, GO:0043197). Some patients show cerebellar vermis atrophy on MRI (HP:0006855, ~33% in the original small series). Onset is early (infancy/early childhood) with global developmental delay; the course is chronic and lifelong and generally non-degenerative, but developmental/verbal-motor regression can occur in those who develop status epilepticus in sleep: "regression in verbal and/or motor domains was observed in all individuals who su[ffered status epilepticus]" [PMID: 38135915].

Finding 10 — Purely genetic etiology; high evolutionary conservation

DLG4-related synaptopathy is monogenic with no established environmental, infectious, lifestyle, or gene-environment contribution; de novo germline DLG4 variants arise sporadically, consistent with "the majority occurred de novo" [PMID: 33597769]. No protective alleles or modifier genes have been identified. ClinVar (accessed 2026) lists ~445 DLG4 variant records: ~207 pathogenic, ~60 likely pathogenic, and ~316 of uncertain significance. DLG4/PSD-95 is deeply conserved: orthologs include mouse Dlg4 (NCBI Gene 13385, MGI:1277959), rat Dlg4 (NCBI Gene 29495), zebrafish dlg4a/dlg4b, Drosophila dlg1 (discs large), and C. elegans dlg-1; the MAGUK/PDZ–SH3–GK architecture is conserved from invertebrates to humans.

Comprehensive Section-by-Section Report

1. Disease Information

Overview. DLG4-related synaptopathy (SHINE syndrome) is a rare autosomal-dominant neurodevelopmental "synaptopathy" — a disorder of synaptic structure and function — caused by heterozygous, predominantly de novo loss-of-function variants in DLG4 (PSD-95). It presents in infancy/early childhood with global developmental delay and evolves into a lifelong picture of intellectual disability, autism, ADHD, hypotonia, sleep disturbance, movement disorders, and (in ~50%) epilepsy [PMID: 33597769, 38135915].

Key identifiers. OMIM 618793 (IDD62); MONDO:0032919; MedGen/UMLS C5394083; DOID:0061035; GARD 0025775. Gene: DLG4 (HGNC:2903, NCBI Gene 1742, UniProt P78352, 17p13.1). A specific ICD-10/ICD-11 code is not assigned to this ultra-rare entity; it is captured under intellectual disability / developmental disorder categories. MeSH indexing is via DLG4/PSD-95 and intellectual disability terms.

Synonyms. SHINE syndrome (Sleep disturbances, Hypotonia, Intellectual disability, Neurological disorders, Epilepsy); Intellectual developmental disorder, autosomal dominant 62 (IDD62); DLG4-related synaptopathy; PSD-95-related neurodevelopmental disorder.

Information source. The knowledge base derives from aggregated disease-level resources (OMIM, ClinVar, gnomAD) plus published patient cohorts and case reports — i.e., published individual-patient data aggregated into cohorts, not routine EHR mining.

2. Etiology

Causal factors. Purely genetic: heterozygous DLG4 variants, most arising de novo [PMID: 33597769]. No environmental, infectious, or lifestyle cause is established (Finding 10).

Genetic risk factors. The causal variant itself is the sole established risk factor. DLG4 is extremely LoF-intolerant (pLI = 1.0; LOEUF = 0.14), meaning even a single loss-of-function allele confers disease (Finding 4). No susceptibility loci or modifier genes have been established.

Environmental risk factors / protective factors / gene-environment interactions. None identified. No protective alleles are known. Because most cases are de novo, advanced parental age (a general contributor to de novo mutation rates) is a plausible but unproven population-level consideration; this is not disease-specific evidence.

3. Phenotypes

Phenotype	Type	HPO term	Onset	Frequency/Notes
Global developmental delay	Clinical sign	HP:0001263	Infancy/early childhood	Predominant feature [PMID: 33597769]
Intellectual disability	Clinical sign	HP:0001249	Childhood	Core, variable severity [PMID: 33597769]
Autism spectrum disorder	Behavioral	HP:0000729	Childhood	Predominant [PMID: 33597769]
ADHD	Behavioral	HP:0007018	Childhood	Predominant [PMID: 33597769]
Hypotonia	Clinical sign	HP:0001252	Neonatal/infancy	Common ("H" in SHINE)
Sleep disturbance	Symptom	HP:0002360	Childhood	Common ("S" in SHINE); modeled in mouse [PMID: 42565830]
Epilepsy/seizures	Clinical sign	HP:0001250	Childhood	~50%; focal most common [PMID: 38135915]
ESES/DEE-SWAS	Clinical sign	HP:0002133	Childhood	>25% of epilepsy patients; regression-associated [PMID: 38135915]
Movement disorder	Clinical sign	HP:0100022	Variable	Reported [PMID: 33597769]
Strabismus	Physical	HP:0000486	Childhood	Reported
Scoliosis	Physical	HP:0002650	Childhood	Reported
Joint hypermobility	Physical	HP:0001382	Childhood	Reported
Marfanoid habitus	Physical	HP:0001519	—	Only 9/53 — NOT characteristic [PMID: 33597769]
Cerebellar vermis atrophy	Imaging	HP:0006855	—	~33% in small series

Severity/progression. Severity is variable; the disorder is chronic and lifelong and generally non-degenerative. However, verbal/motor regression occurs in individuals who develop status epilepticus in sleep (ESES/DEE-SWAS) [PMID: 38135915].

Quality-of-life impact. Substantial: intellectual disability, autism, epilepsy, and sleep disturbance collectively impair communication, learning, independence, and family functioning. No disease-specific EQ-5D/SF-36/PROMIS data are available.

4. Genetic/Molecular Information

Causal gene. DLG4 (HGNC:2903; NCBI Gene 1742; OMIM gene 602887; UniProt P78352; 17p13.1) encoding PSD-95.

Pathogenic variants. Variants span the gene and are predominantly protein-truncating (nonsense, frameshift, splice-site), with a minority of missense and at least one deep-intronic pseudoexon variant. Examples: c.2155A>T p.(Arg719) [PMID: 42462545]; c.2074_2075 frameshift p.(Val692Trpfs12) in the GK domain [PMID: 42565830]; c.2105+235C>T deep-intronic [PMID: 37525972]. Of 45 variants in the defining cohort, 39 were predicted loss-of-function, and the six missense variants were modeled to disrupt structure/function [PMID: 33597769].

Variant classification (ClinVar, 2026). ~445 DLG4 records: ~207 pathogenic, ~60 likely pathogenic, ~316 uncertain significance (Finding 10). Per ACMG/AMP, truncating variants in this LoF-intolerant gene generally meet PVS1.

Allele frequency. Pathogenic variants are absent/vanishingly rare in gnomAD, consistent with de novo origin and extreme constraint (pLI = 1.0, LOEUF = 0.14).

Origin. Germline, predominantly de novo [PMID: 33597769]. No somatic disease association.

Functional consequence. Loss of function / haploinsufficiency (reduced PSD-95 protein) [PMID: 42565830]; some missense variants may act via structural disruption.

Modifier genes / epigenetics / chromosomal abnormalities. None established. DLG4 sits at 17p13.1; larger 17p deletions encompassing DLG4 could plausibly contribute but are not a defined mechanism for this entity.

5. Environmental Information

Not applicable. This is a monogenic disorder with no established environmental factors, lifestyle factors, or infectious agents (Finding 10) [PMID: 33597769].

6. Mechanism / Pathophysiology

Molecular pathway. Glutamatergic synaptic signaling. PSD-95 is the central organizer of the excitatory postsynaptic density (PSD), where it clusters and traffics NMDARs and AMPARs and couples them to downstream signaling (e.g., nNOS, SynGAP, CaMKII) [PMID: 29169997, 20554866].

Causal chain.

DLG4 LoF variant (de novo, heterozygous)
│
▼
Reduced functional PSD-95 protein (haploinsufficiency)
│  (transcript may escape NMD but yields less protein — PMID 42565830)
▼
Disorganized excitatory postsynaptic density:
  ↓ clustering/trafficking of NMDARs & AMPARs (PMID 23268962)
│
▼
Impaired synaptic maturation & aberrant plasticity
  (altered LTP/LTD; PMID 9853749, 23268962)
│
▼
Disrupted neural circuit development (glutamatergic neurons)
│
▼
Clinical manifestations: developmental delay, ID, ASD/ADHD,
hypotonia, sleep disturbance, epilepsy

Upstream vs downstream. Upstream: the DLG4 variant and reduced PSD-95. Downstream: receptor mis-clustering, altered synaptic plasticity, circuit dysfunction, and behavior.

Cellular process. Synaptogenesis, synaptic maturation, and plasticity in glutamatergic neurons. Protein dysfunction: loss of function of a scaffold (not aggregation). Immune/metabolic involvement: none established. Biochemical: receptor scaffolding defect at the PSD.

Molecular profiling. No disease-specific human transcriptomic/proteomic/metabolomic signatures are published; mechanistic evidence derives from mouse models and in vitro biochemistry [PMID: 9853749, 23268962, 20952458, 20554866]. Patient iPSC lines now enable such profiling [PMID: 42462545].

Suggested GO terms: GO:0014069 (postsynaptic density), GO:0098978 (glutamatergic synapse), GO:0048167 (regulation of synaptic plasticity), GO:0007416 (synapse assembly), GO:0035249 (synaptic transmission, glutamatergic). CL: CL:0000679 (glutamatergic neuron).

7. Anatomical Structures Affected

Organ level: Brain / central nervous system (primary). Body system: nervous system. UBERON: brain (UBERON:0000955), cerebral cortex (UBERON:0000956), hippocampus (UBERON:0002421), cerebellar vermis (UBERON:0004720; atrophy in a subset, HP:0006855).
Tissue/cell level: Nervous tissue; glutamatergic excitatory neurons (CL:0000679).
Subcellular level: Postsynaptic density (GO:0014069), dendritic spine (GO:0043197), postsynaptic membrane (GO:0045211).
Lateralization: Bilateral (diffuse CNS involvement).

8. Temporal Development

Onset: Early — infancy/early childhood, with global developmental delay as the presenting feature; insidious/chronic onset.
Progression: Chronic, lifelong, generally non-degenerative. Epilepsy (including ESES/DEE-SWAS) typically emerges in childhood. Regression in verbal/motor domains occurs specifically in those developing status epilepticus in sleep [PMID: 38135915].
Critical period: The ESES/DEE-SWAS window in childhood represents a period of vulnerability (regression) and a potential opportunity for intervention (seizure control). Diagnosis may be delayed to adolescence/adulthood [PMID: 40444229, 42462545].

9. Inheritance and Population

Inheritance: Autosomal dominant (OMIM 618793), predominantly de novo; "the majority occurred de novo (four with unknown origin)" [PMID: 33597769].
Penetrance/expressivity: Presumed high penetrance for LoF variants; expressivity is variable (severity ranges; epilepsy in ~50%).
Anticipation/mosaicism/founder effects/consanguinity: Not applicable/not reported (dominant, de novo, sporadic). Consanguinity is not relevant. Germline mosaicism is theoretically possible (as for any de novo disorder) but not specifically documented.
Carrier frequency: Not applicable (dominant, de novo).
Epidemiology: Ultra-rare; ~53 patients in the defining series with subsequent case reports. No reliable prevalence/incidence estimate exists; the disorder is under-ascertained.
Demographics: No ethnic predilection established. Mouse models suggest possible sex-biased severity (male-biased cognitive deficits in the knock-in model [PMID: 42565830]), but human sex-ratio data are not established.

10. Diagnostics

Genetic testing (definitive): Clinical whole-exome sequencing (WES) or whole-genome sequencing (WGS) identifying a heterozygous DLG4 variant; multi-gene neurodevelopmental/epilepsy/ID panels including DLG4; chromosomal microarray for larger 17p13.1 deletions. RNA/functional studies are required to interpret splice-site and deep-intronic variants (e.g., c.2105+235C>T identified by WGS) [PMID: 37525972, 42462545].
Phenotyping studies: Brain MRI (may show cerebellar vermis atrophy); EEG including sleep EEG/video-polygraphy to detect ESES/DEE-SWAS [PMID: 38135915].
Biomarkers/laboratory tests: No specific biochemical biomarker; diagnosis is molecular. No metabolic, proteomic, or metabolomic diagnostic markers.
Clinical criteria: No formal consensus criteria; diagnosis rests on compatible neurodevelopmental phenotype plus a pathogenic DLG4 variant.
Differential diagnosis: Other monogenic synaptopathies and neurodevelopmental disorders (e.g., SHANK-, SYNGAP1-, GRIN-, and other MAGUK/PSD-related disorders); Marfanoid habitus previously led to confusion but is not characteristic [PMID: 33597769].
Screening: No population/newborn screening. Cascade testing is generally unnecessary given the de novo nature; parental testing informs recurrence-risk counseling.

11. Outcome/Prognosis

Survival/mortality: No evidence of markedly reduced life expectancy; the disorder is non-degenerative. Mortality data are not established (ultra-rare).
Morbidity/function: Substantial lifelong disability from intellectual disability, autism, epilepsy, and behavioral/sleep problems. Many individuals require lifelong support.
Disease course/complications: Epilepsy (including refractory ESES/DEE-SWAS with associated regression), psychiatric complications (including treatment-resistant psychosis/catatonia in at least one adolescent [PMID: 37386468]), and orthopedic issues (scoliosis).
Prognostic factors: Development of status epilepticus in sleep predicts regression [PMID: 38135915]; severity appears to correlate broadly with the degree of PSD-95 loss. No validated prognostic biomarkers.

12. Treatment

No disease-modifying therapy exists. Management is supportive and multidisciplinary.

Modality	Details	NCIT suggestion
Antiseizure medications	Mainstay for epilepsy; ESES/DEE-SWAS forms often refractory; response variable across 35 patients [PMID: 38135915]	NCIT:C264 (Anticonvulsant Agent)
Antipsychotic (clozapine)	Effective for treatment-resistant psychosis/catatonia after failing 3 antipsychotics [PMID: 37386468]	NCIT:C371 (Clozapine)
Developmental/rehabilitative therapy	Physical, occupational, speech therapy; special education	NCIT:C15351 (Rehabilitation Therapy)
Sleep/behavioral management	For sleep disturbance and ASD/ADHD behaviors	—
Experimental PSD-95-directed agents	Nerinetide/Tat-NR2B9c, small molecules — developed for stroke/pain, NOT this disorder [PMID: 40712457]	—

Pharmacogenomics/gene/cell/RNA/targeted/immuno-therapies: None established for this indication. Patient iPSC lines [PMID: 42462545] and patient-derived knock-in mice [PMID: 42565830] provide platforms for future therapeutic development.

13. Prevention

Primary prevention: Not possible (de novo genetic origin).
Secondary/tertiary prevention: Early developmental intervention; sleep-EEG surveillance to detect and treat ESES/DEE-SWAS early (to mitigate regression); management of complications (scoliosis, psychiatric symptoms).
Genetic counseling: Recurrence risk is low for parents of a child with a confirmed de novo variant (bounded by the small possibility of parental germline mosaicism); affected individuals who reproduce carry a 50% transmission risk. Prenatal/preimplantation testing is technically possible for a known familial variant.

14. Other Species / Natural Disease

Taxonomy/orthologs: DLG4/PSD-95 is deeply conserved. Mouse Dlg4 (NCBI Gene 13385, MGI:1277959); rat Dlg4 (NCBI Gene 29495); zebrafish dlg4a/dlg4b; Drosophila dlg1 (discs large); C. elegans dlg-1. The MAGUK PDZ–SH3–GK architecture is conserved from invertebrates to humans (Finding 10).
Natural disease in other species: No naturally occurring DLG4 disorder is documented in companion animals or wildlife (OMIA); disease knowledge derives from engineered models.
Comparative/evolutionary: High conservation of the scaffold and its receptor-clustering function underlies the strong translational validity of rodent models.

15. Model Organisms

Model	Type	Key phenotype recapitulation	PMID
PSD-95-null mouse	Mammalian knockout	Enhanced hippocampal LTP; severely impaired spatial learning	[9853749]
PDZ1/2 ligand-binding-deficient PSD-95 knock-in	Mammalian knock-in	↓PSD accumulation of PSD-95/PSD-93/AMPARs; abnormal anxiety; impaired spatial/working/remote memory	[23268962]
Dlg4−/− mouse	Mammalian knockout	Increased repetitive behavior; abnormal social/communication behavior; impaired motor coordination; anxiety	[20952458]
Dlg4 V692Wfs*12/+ patient-derived knock-in	Mammalian knock-in	Reduced PSD-95; learning/cognitive-flexibility deficits (male-biased); sleep abnormalities — "recapitulate several hallmark features of SHINE syndrome"	[42565830]
AOUMEYi004-A iPSC line (c.2155A>T p.Arg719*)	Human iPSC	Pluripotent; three-germ-layer differentiation; platform for neuronal modeling	[42462545]

Model strengths: Rodent models robustly reproduce cognitive, behavioral, synaptic-plasticity, and (in the newest knock-in) sleep phenotypes, with a patient-specific variant. Limitations: Species differences in cognition/epilepsy; sex-specific effects require careful design; iPSC models capture cellular but not circuit-level phenotypes. Resources: MGI (Dlg4, MGI:1277959), IMPC, Cellosaurus (iPSC line).

Mechanistic Model / Interpretation

DLG4-related synaptopathy is a textbook haploinsufficiency synaptopathy. The convergent evidence — extreme population-genetic constraint (pLI = 1.0, LOEUF = 0.14), a predominance of de novo protein-truncating variants, direct demonstration of reduced PSD-95 protein from a patient variant, and faithful recapitulation of cognitive/behavioral/sleep phenotypes in a patient-derived knock-in mouse — locks together into a single coherent causal chain: one lost DLG4 allele → less PSD-95 → a disorganized glutamatergic postsynaptic density → impaired synaptic maturation and aberrant plasticity → abnormal circuit development → the SHINE clinical phenotype.

Two clinically important nuances emerge. First, the relationship between synaptic plasticity and cognition is not simply "less plasticity = worse learning": PSD-95-null mice show enhanced LTP yet impaired learning [PMID: 9853749], indicating that PSD-95 sets the correct dynamic range and metaplasticity of synapses, not merely their strength. Second, epilepsy — specifically the ESES/DEE-SWAS subtype — is a modifiable driver of the worst outcomes (regression), making its early detection via sleep EEG a high-yield clinical priority [PMID: 38135915].

Population genetics        Molecular biology          Model systems              Clinic
─────────────────────      ─────────────────────      ─────────────────────      ─────────────────────
pLI=1.0, LOEUF=0.14   →    ↓PSD-95 protein       →    KO/KI mice: learning,  →   GDD, ID, ASD/ADHD,
(LoF not tolerated)        disorganized PSD           sleep, behavior deficits    epilepsy, sleep, hypotonia
                   (↓NMDAR/AMPAR clustering)  iPSC platform               (regression if ESES)

Evidence Base

PMID	Title (abbreviated)	Role in this report
33597769	DLG4-related synaptopathy: a new rare brain disorder	Landmark cohort (n=53); defines disorder, name, core phenotype, de novo LoF mechanism, variant spectrum
38135915	Developmental epileptic encephalopathy in DLG4-related synaptopathy	Epilepsy in ~50%; ESES/DEE-SWAS >25%; regression; EEG/MRI diagnostics; ASM response
42565830	Patient-derived mouse model reproduces SHINE syndrome	Reduced PSD-95 protein; knock-in recapitulates hallmark features (sex-specific)
9853749	Enhanced LTP and impaired learning in PSD-95 mutant mice	Synaptic-plasticity/learning link
23268962	PDZ1/2 ligand-binding-deficient PSD-95 knockin mice	Receptor clustering, memory, anxiety deficits
20952458	Dlg4 deletion and ASD/Williams-relevant phenotypes	ASD-relevant behavior in knockout
29169997	PSD95: schizophrenia or autism?	PSD-95 scaffolding function; synaptogenesis role
37386468	Clozapine in adolescent with SHINE syndrome	Treatment of treatment-resistant psychosis
37525972	Deep intronic DLG4 variant	WGS diagnosis; protein-truncating predominance
42462545	hiPSC line from DLG4 patient (c.2155A>T p.Arg719)*	WES diagnosis; iPSC modeling platform
40444229	Late-onset diagnosis of SHINE syndrome	Under-ascertainment; SHINE acronym; AD inheritance
40712457	PSD-95/nNOS PPI disruption	Experimental PSD-95-directed agents (stroke/pain, not this disorder)
20554866	NMDAR signaling complexes / lipid rafts	PSD-95 organizes NMDAR complexes in vivo

Additional supporting/context papers on PSD-95-interacting partners and MAGUK biology: [PMID: 18248606], [21878521], [37928066], [19467332], [29798891], [26609151].

Limitations and Knowledge Gaps

Epidemiology: No reliable prevalence or incidence; the entity is ultra-rare and under-ascertained. Sex ratio and age distribution in humans are undefined.
Human molecular profiling: No published patient transcriptomic/proteomic/metabolomic datasets; mechanistic inference relies on rodent and in vitro models.
Genotype–phenotype correlation: Not yet quantified — whether missense/hypomorphic vs truncating variants, or variant location within domains, predicts severity or epilepsy risk remains open.
Penetrance/expressivity: Assumed high penetrance but not formally quantified; drivers of variable expressivity (including the ~50% epilepsy split) are unknown.
Therapeutics: No disease-modifying therapy; supportive-care evidence is limited to retrospective series and single case reports.
Missense mechanism: Whether some missense variants act by dominant-negative rather than simple loss-of-function is not fully resolved.

Proposed Follow-up Experiments / Actions

Establish an international patient registry to derive prevalence, natural-history, sex-ratio, and genotype–phenotype data.
Systematic sleep-EEG surveillance study to define the incidence, timing, and treatment responsiveness of ESES/DEE-SWAS and its link to regression — a directly actionable clinical priority.
Patient-iPSC-derived neuron/organoid profiling (transcriptomics, proteomics, electrophysiology) to define human cell-autonomous consequences of PSD-95 loss and to build a drug-screening platform [building on PMID: 42462545].
Genotype–phenotype analysis across the expanding ClinVar/cohort variant set, stratified by variant type and PSD-95 domain, to test whether GK-domain or PDZ-domain variants confer distinct risks.
Preclinical therapeutic testing in the patient-derived knock-in mouse [PMID: 42565830] — e.g., ASO-mediated upregulation of the wild-type allele, or agents that stabilize the residual PSD, and rigorous evaluation of sex-specific responses.
Prospective ASM comparative-effectiveness study for the ESES/DEE-SWAS subtype, given its refractoriness and outsized impact on outcomes.

Evidence types: human clinical [33597769, 38135915, 37386468, 40444229, 42462545, 37525972]; model organism [9853749, 23268962, 20952458, 42565830, 20554866]; in vitro / review [29169997, 40712457]; computational/population-genetic [gnomAD constraint, ClinVar].

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Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Variants

Medical Actions

Diagnosis

Imaging Findings

Progression

Prevalence

Differential Diagnoses

Experimental Models

Animal Models

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DLG4-Related Synaptopathy: Comprehensive Research Report

1. Disease Information

Overview

Key Identifiers

Synonyms / Alternative Names

Data Provenance

2. Etiology

Disease Causal Factors

Genetic Risk Factors

Environmental Risk Factors

Protective Factors

Gene-Environment Interactions

3. Phenotypes

Cognitive / Developmental (Symptoms)

Neurologic Signs

Ophthalmologic Findings (Clinical Signs)

Musculoskeletal / Marfanoid Connective-Tissue Findings

Sleep and Gastrointestinal

Phenotype Characteristics

Quality of Life Impact

4. Genetic/Molecular Information

Causal Gene

Pathogenic Variants

Protein Domain Structure and Molecular Function

Other DLG-MAGUK Family Members (Relevant Comparators)

Modifier Genes

Epigenetic Information / Chromosomal Abnormalities

5. Environmental Information

6. Mechanism / Pathophysiology

Causal Chain (Molecular → Cellular → Clinical)

Cellular Processes and Cell Types Involved

Molecular/Systems Biology Evidence

Genotype-Phenotype Correlation

7. Anatomical Structures Affected

Organ Level

Tissue and Cell Level

Subcellular Level

Localization

8. Temporal Development

Onset

Progression

Patterns

9. Inheritance and Population

Epidemiology

Inheritance Pattern

Population Demographics

10. Diagnostics

Clinical Tests

Genetic Testing

Clinical Diagnostic Criteria

Differential Diagnosis

Screening

11. Outcome/Prognosis

Survival and Mortality

Morbidity and Functional Outcomes

Disease Course / Complications

Prognostic Factors

12. Treatment