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Inheritance

2

X-linked inheritance with mechanism-dependent expression in females HP:0001417

GRIA3 is X-chromosomal, so transmission follows an X-linked pattern, but a single recessive/dominant label does not describe the disorder. Affected males most often carry a hemizygous loss-of-function allele inherited from a clinically healthy carrier mother, while affected females most often carry a de novo heterozygous gain-of-function allele. Both variant classes are disease-causing in both sexes.

X-linked inheritance Expressivity: VARIABLE

Show evidence (2 references)

PMID:38038360 SUPPORT Human Clinical

"Loss-of-function and gain-of-function variants were disease-causing in both sexes but affected males often carried de novo or hemizygous loss-of-function variants inherited from healthy mothers, whereas affected females had mostly de novo heterozygous gain-of-function variants."

States the sex- and mechanism-dependent transmission pattern that this inheritance block records, including that both allele classes affect both sexes.

PMID:38038360 SUPPORT Human Clinical

"AMPARs form by homo- or heteromeric assembly of subunits encoded by the GRIA1-GRIA4 genes, of which only GRIA3 is X-chromosomal."

Establishes that GRIA3 is the X-chromosomal member of the AMPA receptor subunit family, which is why this disorder alone among the GRIA disorders is X-linked.

X-linked recessive inheritance in carrier-mother pedigrees HP:0001419

The historical Wu-type pedigrees are classic X-linked recessive families in which hemizygous males are affected and heterozygous carrier mothers are clinically normal or only mildly affected. This describes many familial loss-of-function pedigrees but is incomplete for de novo gain-of-function disease.

X-linked recessive inheritance Penetrance: UNKNOWN

Show evidence (2 references)

PMID:41462794 SUPPORT Human Clinical

"GRIA3 is located on the X-chromosome, and pathogenic variants may be transmitted from unaffected carrier mothers to affected male offspring, a pattern typical of several X-linked neurodevelopmental disorders"

Describes the carrier-mother-to-affected-son transmission that defines the recessive pedigree pattern.

PMID:34731330 SUPPORT Human Clinical

"The GRIA3 gene maps to chromosome Xq25 and the c.2360A > G variant was transmitted by his healthy mother."

Worked example of maternal transmission of a pathogenic GRIA3 allele from a clinically healthy carrier to an affected son.

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Discussions and Knowledge Gaps

3

Why does the Gria3 null mouse show no spatial memory deficit when global developmental impairment is present in every functionally characterised human patient?

HUMAN MODEL MISMATCH OPEN gria3_ko_mouse_no_cognitive_phenotype

Attached to

pathophysiology#Disturbed Excitatory Synaptic Transmission and Plasticity phenotypes#Global developmental delay animal_models#Gria3 knockout mouse

This is not an absence of evidence but a positive negative result: the knockout was tested on the Morris water maze and the Y-maze and performed normally, while reproducing aggression, sociality, motor and monoaminergic changes. Three readings are open and the data do not separate them. Developmental compensation by GluA1- and GluA2-containing receptors may mask the lesion in a constitutive null in a way that a patient missense allele — which still produces a subunit that assembles into heterotetramers — would not. Rodent spatial navigation may simply be the wrong proxy for human global developmental impairment. Or GluA3 loss may genuinely not be sufficient for the cognitive phenotype, with the human presentation requiring additional species-specific circuit context. Which of these holds matters for whether any Gria3 rodent model can serve as a preclinical efficacy readout for this disorder.

Show evidence (2 references)

PMID:22285418 SUPPORT Model Organism

"Gria3-/Y mice showed no significant deficit in spatial memory function in Morris-water maze and Y-maze tests, and normal levels of testosterone."

The negative cognitive result in the knockout that creates the mismatch with the human phenotype.

PMID:38038360 SUPPORT Human Clinical

"All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25)."

The human side of the mismatch: developmental impairment is universal in patients.

What determines whether a heterozygous female carrying a GRIA3 variant is unaffected, mildly affected, or has a developmental and epileptic encephalopathy?

KNOWLEDGE GAP OPEN female_heterozygote_severity_determinants

Attached to

pathophysiology#GluA3 Gain of Function inheritance#X-linked inheritance with mechanism-dependent expression in females

Carrier mothers transmitting loss-of-function alleles are usually clinically normal, yet females with de novo gain-of-function alleles can be as severely affected as any male, and one female with a de novo allele has only moderate intellectual disability with a good adaptive profile. X-chromosome inactivation generates a mosaic neuronal population expressing either the wild-type or the mutant allele, which is the obvious candidate explanation, but no study has measured skewing against severity in this gene, and the authors of the largest case series state explicitly that neither X-inactivation nor mosaicism fully accounts for the range of symptoms. The functional direction of the allele is a confounder that has never been controlled for: female cases are enriched for gain of function, so an apparent sex effect may partly be an allele-class effect. Resolving this matters directly for counselling carrier females.

Show evidence (2 references)

PMID:41462794 SUPPORT Human Clinical

"As an X-linked gene, GRIA3 is subject to X-chromosome inactivation (XCI), which generates mosaic expression in females and results in a mixed neuronal population expressing either the wild-type or the mutant allele."

States the candidate mechanism whose contribution to female severity is unmeasured.

PMID:36726007 SUPPORT Human Clinical

"Neither X-inactivation nor mosaicism can entirely account for the range of symptoms or severity."

Explicit statement that the obvious explanation is insufficient, which is what makes this a gap rather than a settled question.

Should AMPA receptor pharmacology in GRIA3 disease be selected by the measured functional direction of the patient's own variant, and is an AMPAR antagonist such as perampanel appropriate for gain-of-function disease?

OPEN QUESTION OPEN mechanism_matched_ampar_pharmacology

Attached to

treatments#Carbamazepine for Gain-of-Function Disease pathophysiology#GluA3 Gain of Function pathophysiology#GluA3 Loss of Function

The bidirectional allelic architecture makes this the sharpest open therapeutic question in the disorder. The sensitivity of variant receptors to AMPAR-selective modulators has been measured in recombinant assays, and one clinician group has proposed perampanel, a non-competitive AMPAR antagonist, as a candidate first-line agent. Against that, there is one reported perampanel failure — in the male patient described by Trivisano and colleagues — which a later group cites as behaving the way loss of function predicts. The electrophysiology in that later paper was done on their own p.Glu787Gly allele, not on the treated patient, so this is a same-residue inference and not a measurement in the patient who failed the drug. But direction matters both ways: enhancing an already over-active receptor, or blocking one that is already under-conducting, would be expected to worsen the phenotype. The single supporting clinical observation is the N-of-1 carbamazepine response in a functionally confirmed gain-of-function male, and the one apparent counterexample is a carbamazepine failure in a patient whose variant was never tested electrophysiologically — which is exactly the ambiguity a mechanism-matched strategy is meant to remove. No trial has tested the strategy, and 13 of 44 tested rare GRIA3 missense alleles were functionally neutral, so the strategy also presupposes routine access to variant-level electrophysiology that does not currently exist in clinical practice.

Show evidence (4 references)

PMID:37921875 SUPPORT In Vitro

"We evaluated the sensitivity of variant receptors to AMPAR-selective modulators including FDA-approved drugs to explore potential targeted therapeutic options."

Establishes that variant-specific pharmacological sensitivity has been measured in vitro, which is the basis for proposing a mechanism-matched strategy.

PMID:34731330 SUPPORT Human Clinical

"a targeted trial with a selective non-competitive AMPA receptor antagonist (Perampanel) proved to be ineffective, as expected in case of loss of function of the receptor"

The mirror image of the carbamazepine result. Note carefully whose patient this is: the failure occurred in a patient reported by another group, and the loss of function was measured in the citing authors' own p.Glu787Gly allele at the same residue. The quoted "as expected in case of loss of function" is therefore their inference across a shared residue, not an electrophysiological result in the treated patient.

PMID:41462794 SUPPORT Human Clinical

"It is worth considering that the trial of perampanel, an antiepileptic drug with the AMPA receptor mechanism of action, did not prove clinical or EEG improvement in a previous report"

A later group reading the same perampanel failure the same way. This is a second citation of one event, not a second event, so it corroborates the interpretation and does nothing to establish that the result generalises.

+ 1 more reference

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Pathophysiology

7

GRIA3 Pathogenic Variant

A germline sequence or structural alteration of GRIA3 at Xq25 — missense, canonical splice-site, frameshift, multi-exon deletion or duplication, or a translocation disrupting the locus — is the initiating lesion. GRIA3 encodes GluA3, the sole X-chromosomal member of the GRIA1-GRIA4 family that assembles into AMPA-type ionotropic glutamate receptors, so a single hemizygous allele in a male is sufficient and a heterozygous allele in a female acts against a mosaic wild-type background.

GRIA3 hgnc:4573

Downstream

GluA3 Loss of Function Splice disruption, protein truncation, exon deletion, or a missense change that stabilises a non-conducting channel removes GluA3-mediated current.

GluA3 Gain of Function A subset of missense alleles in and around the channel gate instead slows receptor desensitisation and deactivation, prolonging rather than abolishing current.

Show evidence (2 references)

PMID:38038360 SUPPORT Human Clinical

"AMPARs form by homo- or heteromeric assembly of subunits encoded by the GRIA1-GRIA4 genes, of which only GRIA3 is X-chromosomal."

Identifies GRIA3 as the X-chromosomal AMPA receptor subunit gene whose alteration is the initiating lesion of this disorder.

PMID:34731330 SUPPORT Human Clinical

"the causative role of GRIA3 in XLID patients has been suggested also for Xq25 copy number variants"

Records that structural Xq25 lesions, not only single-nucleotide variants, constitute the initiating GRIA3 alteration in X-linked intellectual disability.

GluA3 Loss of Function

Loss-of-function alleles reduce or abolish GluA3 activity by disrupting transcription or splicing, truncating the protein, deleting exons, or — for the p.Ala653Thr gate variant — stabilising the assembled channel in a closed, non-conducting conformation. In the functionally screened variant set, loss and gain of function together accounted for 31 of 44 tested alleles, so neither direction can be assumed from variant rarity alone.

Genetic context GRIA3 hgnc:4573 allele_type: missense, canonical splice-site, frameshift, and multi-exon deletion alleles variant_origin: GERMLINE functional_impact_category: LOSS_OF_FUNCTION

Typically hemizygous in affected males and inherited from a clinically healthy carrier mother, though de novo loss-of-function alleles also occur and heterozygous females can be affected, so zygosity is left unset rather than asserting the modal case. Mechanisms with direct functional support are exon-2 skipping from c.268+1G>C, the p.Glu787Gly allele that produced no measurable current, and the p.Ala653Thr closed-channel allele. A multi-exon deletion is also reported but only in a source with no PubMed record, so it is described here rather than cited. p.Gly630Arg is a segregating familial allele with no electrophysiology and is deliberately not assigned a functional direction.

GluA3-containing AMPA receptor channel activity GO:0004971 ⇓ LOSS OF FUNCTION

Experimental models

Heterologous AMPA receptor expression with patch-clamp electrophysiology CELL LINE The same assay assigns loss of function, including the closed-channel mechanism that leaves protein expression intact.

HEK293T minigene splicing assay CELL LINE Demonstrates the RNA-level lesion — exon 2 skipping — through which a canonical splice-donor variant abolishes normal GluA3 production.

Animal models

Gria3 knockout mouse Mus musculus recapitulates A null allele is the cleanest available model of complete GluA3 loss of function and isolates the consequences of absent GluA3 from any residual mutant-subunit effect.

Downstream

Reduced AMPA Receptor-Mediated Excitatory Current

Show evidence (3 references)

PMID:35031858 SUPPORT Human Clinical

"Hemizygous loss-of-function (LOF) variants in GRIA3 cause a neurodevelopmental disorder (NDD) in male individuals."

States that hemizygous GRIA3 loss of function is an established cause of the neurodevelopmental phenotype in males.

PMID:38038360 SUPPORT In Vitro

"Thirty-one variants alter receptor function and show loss-of-function or gain-of-function properties, whereas 13 appeared neutral."

Systematic electrophysiological screening establishes loss of function as one of two distinct functional classes among pathogenic GRIA3 alleles, alongside a substantial functionally neutral fraction.

PMID:29016847 SUPPORT In Vitro

"The mutation (A653T) falls within the highly conserved transmembrane domain of the ion channel gate"

Locates the archetypal closed-channel loss-of-function allele in the ion-conduction gate, explaining why it removes current without removing the protein.

GluA3 Gain of Function

Gain-of-function alleles prolong receptor activation by slowing desensitisation and deactivation, so each glutamate release event drives a longer-lasting depolarising current. This is a qualitative change in gating kinetics rather than simply more receptor activity, and it produces a clinical picture opposite to loss of function in muscle tone and seizure onset age.

Genetic context GRIA3 hgnc:4573 allele_type: missense alleles clustering in and around the channel gate and M3-S2 linker variant_origin: DE_NOVO functional_impact_category: GAIN_OF_FUNCTION

Zygosity is deliberately left unset because the single-valued slot cannot represent this branch: affected females are heterozygous and affected males hemizygous, and both occur. p.Ala615Val is the only allele here whose gain of function was measured, by patch clamp, in a hemizygous de novo male. The female alleles usually cited alongside it — p.Met661Thr and p.Thr657Ala — were never tested electrophysiologically; their assignment to this branch is inferred from residue position and from the hypertonic phenotype, and both source papers say so explicitly.

GluA3-containing AMPA receptor channel activity GO:0004971 ⇑ GAIN OF FUNCTION

Experimental models

Heterologous AMPA receptor expression with patch-clamp electrophysiology CELL LINE Measures agonist potency, response time course, desensitisation and deactivation, from which the gain-of-function direction is assigned.

Animal models

Transgenic Drosophila expressing mutant human GluA3 Drosophila melanogaster measures Reads out the functional direction of a human allele through a developmental phenotype in a whole organism, complementing the patch-clamp measurement.

Downstream

Prolonged AMPA Receptor-Mediated Excitatory Current

Show evidence (3 references)

PMID:35031858 SUPPORT Human Clinical

"His neurological signs, such as hypertonia and hyperreflexia, were opposite to those in previous cases having LOF GRIA3 variants."

Establishes gain of function as a mechanistically distinct class whose clinical signs run opposite to loss of function, which is the reason this pathograph branches.

PMID:35031858 SUPPORT Model Organism

"A fly line expressing a human GluA3 mutant possessing our variant and the Lurcher variant, which makes ion channels leaky, showed developmental defects, while one expressing a mutant possessing either of them did not."

Transgenic Drosophila expressing the human mutant subunit shows a genetic interaction with a leaky-channel allele, independent in vivo support for a gain-of-function effect.

PMID:37921875 SUPPORT In Vitro

"These variants produce changes in agonist EC50, response time course, desensitization, and/or receptor surface expression."

Broader GRIA functional survey confirms that altered desensitisation and response time course are the recurring biophysical consequences of pathogenic AMPA receptor variants.

Reduced AMPA Receptor-Mediated Excitatory Current

Loss of GluA3 conductance reduces the fast excitatory postsynaptic current carried by GluA2/3 heterotetramers, one of the two major hippocampal AMPA receptor populations. Clinically this branch is enriched for low muscle tone, later seizure onset, and severely disorganised sleep-wake architecture.

glutamatergic neuron CL:0000679

AMPA receptor-mediated excitatory postsynaptic current GO:0060079 ↓ DECREASED ionotropic glutamate receptor signaling pathway GO:0035235 ↓ DECREASED

GluA2/3 AMPA receptor complex GO:0032281 postsynaptic membrane GO:0045211

Animal models

Gria3 A653T knock-in mouse Mus musculus partially recapitulates Carries the exact human loss-of-function allele and reproduces the sleep-architecture and light-sensitivity consequences attributed to reduced GluA3 current in the patients.

Downstream

Disturbed Excitatory Synaptic Transmission and Plasticity

Hypotonia Low muscle tone is the tone phenotype specifically enriched in the loss-of-function branch of the cohort.

Hyporeflexia Depressed deep tendon reflexes are the reflex counterpart of the low tone on this branch, mirroring the hyperreflexia seen with prolonged current.

Sleep disturbance Sleep-wake disorganisation segregates with loss of function in the cohort and is reproduced allele-specifically in a knock-in mouse.

Show evidence (2 references)

PMID:36429079 SUPPORT Model Organism

"The most abundant AMPAR subtypes in the hippocampus are GluA1/2 and GluA2/3 heterotetramers."

Establishes that GluA3-containing receptors carry a major share of hippocampal AMPA current, so losing GluA3 function measurably reduces that current.

PMID:38038360 SUPPORT Human Clinical

"AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs) mediate fast excitatory neurotransmission in the brain."

Identifies fast excitatory neurotransmission as the function that a loss of AMPA receptor conductance reduces.

Prolonged AMPA Receptor-Mediated Excitatory Current

Slowed desensitisation and deactivation extend the depolarising current carried by mutant GluA3-containing receptors after each glutamate transient, so charge transfer per synaptic event increases. Clinically this branch is enriched for high muscle tone, hyperreflexia, hyperekplexia and very early seizure onset.

glutamatergic neuron CL:0000679

AMPA receptor-mediated excitatory postsynaptic current GO:0060079 ↑ INCREASED excitatory chemical synaptic transmission GO:0098976 ↑ INCREASED

GluA3-containing AMPA receptor complex GO:0032281

Downstream

Disturbed Excitatory Synaptic Transmission and Plasticity

Hypertonia Increased tone is the tone phenotype specifically enriched in the gain-of-function branch, and in the functionally confirmed p.Ala615Val case it responded to a drug that suppresses glutamate release.

Abnormality of movement Movement disorders as a class are more common on this branch, with hyperekplexia and non-epileptic erratic myoclonus as the dominant expression.

Exaggerated startle response Hyperekplexia and non-epileptic erratic myoclonus are the most prevalent movement features and cluster with gain of function.

Show evidence (2 references)

PMID:35031858 SUPPORT In Vitro

"Patch-clamp recordings showed that the human GluA3 mutant (p.Ala615Val) had slower desensitization and deactivation kinetics."

The measured kinetic slowing is the biophysical definition of the prolonged current this node describes.

PMID:37921875 SUPPORT INDIRECT In Vitro

"We predict that these functional and localization changes will have important consequences for circuit function, and therefore likely contribute to the patients' clinical phenotype."

Connects the measured AMPA receptor gating changes to expected circuit-level consequences. Marked INDIRECT because the quoted sentence is the authors' stated prediction from the measured biophysics, not an observation of the circuit consequence itself.

Disturbed Excitatory Synaptic Transmission and Plasticity

Both branches converge here. Whether GluA3-mediated current is reduced or prolonged, the postsynaptic response to glutamate is mistimed relative to the activity-dependent rules that govern synaptic strengthening, so experience-dependent plasticity is degraded and the circuits that support learning and memory develop abnormally. The cognitive outcome itself is carried by the downstream HP phenotypes rather than by a GO behaviour term on this node. GluA2/3 receptors cycle constitutively under basal conditions and their auxiliary partners set trafficking and gating, so the lesion is felt at the level of synaptic maintenance as well as of acute transmission.

glutamatergic neuron CL:0000679 neuron CL:0000540

chemical synaptic transmission GO:0007268 ⚠ ABNORMAL regulation of synaptic plasticity GO:0048167 ↕ DYSREGULATED

postsynaptic density GO:0014069

brain UBERON:0000955 hippocampal formation UBERON:0002421 cerebral cortex UBERON:0000956

Animal models

Gria3 knockout mouse Mus musculus fails to recapitulate The knockout does not reproduce the cognitive impairment that defines the human disorder. Spatial memory was intact on both the Morris water maze and the Y-maze, so the model cannot be used to read out the learning-and-memory limb of this node.

Downstream

Cortical Network Hyperexcitability

Intellectual disability The developmental impairment resolves into fixed intellectual disability in older children and adults, which is the term the adult pedigrees are described with.

Psychosis Psychiatric manifestations emerge in adulthood in some pedigrees. The step from disturbed excitatory transmission to psychosis is not measured in any patient and is asserted here only as the shared upstream lesion.

Aggressive behavior Aggression is reported in affected adult males and is one of the few human features the Gria3 null mouse reproduces, which is why it is hung on the shared synaptic node rather than on either allele branch.

Autistic behavior Autistic features recur across the older familial descriptions without segregating by allele class.

Global developmental delay Global developmental impairment is the one feature present in every functionally characterised patient, on both branches, which is what makes it the convergent output of this shared node rather than of either allele class.

Show evidence (2 references)

PMID:36429079 SUPPORT Model Organism

"Several interactors were shown to affect biogenesis, AMPAR trafficking, and channel properties, alone or in distinct assemblies, and several revealed preferred binding to specific AMPAR subunits."

Establishes that GluA3-containing receptor complexes have subunit-specific trafficking and gating regulation, so altering GluA3 perturbs synaptic receptor handling and not only instantaneous conductance.

PMID:34731330 SUPPORT Human Clinical

"AMPARs are heterotetrameric receptors combining four different subunits, defined GluA1-4 and encoded by GRIA1-4 genes, respectively."

Establishes that GluA3 is one subunit of an obligate heterotetramer, so a variant subunit is incorporated into and perturbs otherwise normal synaptic receptors.

Cortical Network Hyperexcitability

Mistimed excitatory drive in developing cortical and thalamocortical circuits lowers the threshold for synchronous discharge. EEG in affected individuals shows focal spikes that generalise readily, and in one female with a de novo allele the network state escalated to non-convulsive status epilepticus. The step from synaptic dysfunction to network hyperexcitability is inferred from clinical electrophysiology rather than measured directly in patient cortex, so it is recorded as provisional.

regulation of neuronal membrane potential GO:0042391 ↕ DYSREGULATED

cerebral cortex UBERON:0000956

Downstream

Seizure

Show evidence (2 references)

PMID:36726007 SUPPORT Human Clinical

"AMPARs, including complexes with GluA3, are broadly distributed in the brain, particularly in the hippocampus, cerebral cortex, and thalamus, regions associated with epileptic activity"

Places GluA3-containing receptors in exactly the cortical and thalamic circuits that generate epileptic activity, which is the anatomical basis for this node.

PMID:41462794 SUPPORT Human Clinical

"The EEG revealed high-amplitude diffuse rhythmic theta/delta activity consistent with NCSE."

Diffuse rhythmic electrographic activity documents sustained network-level hyperexcitability in a GRIA3 patient.

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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

27

Musculoskeletal 2

Hypertonia FREQUENT HP:0001276

Sequelae: Hyperreflexia Spastic gait

Show evidence (2 references)

PMID:38038360 SUPPORT Human Clinical

"Limb muscular hypotonia was reported in 13/25, and hypertonia in 10/25."

Gives the cohort frequency of hypertonia.

PMID:36726007 SUPPORT Human Clinical

"She exhibited hypertonia and increased deep tendon reflexes."

Documents hypertonia with hyperreflexia from birth in a de novo heterozygous female.

Scoliosis VERY_RARE HP:0002650

Show evidence (1 reference)

PMID:36726007 SUPPORT Human Clinical

"She now presents with severe developmental delay, scoliosis and hip dislocation."

Reports scoliosis in a severely affected, bedridden GRIA3 patient.

Nervous System 18

Global developmental delay VERY_FREQUENT HP:0001263

Sequelae: Delayed speech and language development Severe global developmental delay

Show evidence (1 reference)

PMID:38038360 SUPPORT Human Clinical

"All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25)."

Reports universal global developmental impairment with its severity distribution in the reference cohort.

Intellectual disability VERY_FREQUENT HP:0001249

Show evidence (2 references)

PMID:41462794 SUPPORT Human Clinical

"Over the following years, she developed a paraparetic spastic gait with hyperreflexia, expressive language impairment, and moderate intellectual disability (ID)."

Records intellectual disability at the mild end of the reported range, formally assessed.

PMID:34731330 SUPPORT Human Clinical

"The index subject was referred for severe ID, myoclonic seizures, cerebellar signs and short stature."

Records intellectual disability at the severe end of the range in an independent pedigree.

Severe global developmental delay FREQUENT HP:0011344

Sequelae: Scoliosis Hip dislocation

Show evidence (2 references)

PMID:38038360 SUPPORT Human Clinical

"All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25)."

Gives the 12/25 severe fraction that this phenotype records.

PMID:36726007 SUPPORT Human Clinical

"She now presents with severe developmental delay, scoliosis and hip dislocation."

Illustrative severe case, and the source for the orthopaedic sequelae recorded below.

Delayed speech and language development FREQUENT HP:0000750

Show evidence (2 references)

PMID:41462794 SUPPORT Human Clinical

"Over the following years, she developed a paraparetic spastic gait with hyperreflexia, expressive language impairment, and moderate intellectual disability (ID)."

Documents expressive language impairment as part of the phenotype in a mildly affected female.

PMID:36726007 SUPPORT Human Clinical

"However, she was bedridden and had poor speaking ability at one year of age."

Documents severely impaired speech acquisition at the severe end of the spectrum.

Seizure FREQUENT HP:0001250

Sequelae: Focal motor seizure Generalized myoclonic seizure Non-convulsive status epilepticus

Show evidence (2 references)

PMID:38038360 SUPPORT Human Clinical

"The epilepsy syndrome was classified as developmental and epileptic encephalopathy in eight patients, developmental encephalopathy without seizures in 13 patients, and intellectual disability with epilepsy in four patients."

Gives the epilepsy syndrome classification across the cohort, including the fraction with no seizures at all.

PMID:36726007 SUPPORT Human Clinical

"Epilepsy onset occurred at 3 months of age with tonic and clonic seizures."

Individual early-onset example in a de novo heterozygous female, consistent with the gain-of-function onset distribution.

Generalized myoclonic seizure OCCASIONAL HP:0002123

Show evidence (2 references)

PMID:34731330 SUPPORT Human Clinical

"stress the relevance of myoclonic seizures and cerebellar syndrome as cardinal features of his presentation"

Identifies myoclonic seizures as a defining feature of a GRIA3-variant proband.

PMID:34731330 SUPPORT Human Clinical

"Epilepsy onset occurred at 29 months with clonic seizures and myoclonic seizures with fall."

Individual semiology and onset age for the myoclonic seizures in that proband, whose familial allele was inherited rather than de novo.

Hyperreflexia OCCASIONAL HP:0001347

Show evidence (1 reference)

PMID:35031858 SUPPORT Human Clinical

"His neurological signs, such as hypertonia and hyperreflexia, were opposite to those in previous cases having LOF GRIA3 variants."

Records hyperreflexia in the functionally confirmed gain-of-function male and contrasts it with the loss-of-function presentation.

Abnormality of movement FREQUENT HP:0100022

Show evidence (1 reference)

PMID:38038360 SUPPORT Human Clinical

"Movement disorders were reported in 14/25, with hyperekplexia or non-epileptic erratic myoclonus being the most prevalent feature (8/25)."

Gives the cohort frequency of movement disorders and names their dominant expression.

Exaggerated startle response FREQUENT HP:0002267

Show evidence (2 references)

PMID:38038360 SUPPORT Human Clinical

"Movement disorders were reported in 14/25, with hyperekplexia or non-epileptic erratic myoclonus being the most prevalent feature (8/25)."

Establishes hyperekplexia as the most prevalent movement feature with its cohort fraction.

PMID:38038360 SUPPORT Human Clinical

"Gain-of-function variants were associated with more severe outcomes: patients were younger at the time of seizure onset (median age: 1 month), hypertonic and more often had movement disorders, including hyperekplexia."

Assigns hyperekplexia specifically to the gain-of-function class.

Sleep disturbance OCCASIONAL Sleep-wake cycle disturbance HP:0006979

Show evidence (2 references)

PMID:29016847 SUPPORT Human Clinical

"we sequenced a family in which the two male children had severe developmental delay and a dramatically disturbed sleep-wake cycle, with very long wake and sleep durations, reaching up to 106-h awake and 48-h asleep."

Quantifies the extreme sleep-wake disturbance in an affected sibship carrying a loss-of-function GRIA3 allele.

PMID:38038360 SUPPORT Human Clinical

"Patients with loss-of-function variants were older at the time of seizure onset (median age: 16 months), hypotonic and had sleeping disturbances."

Assigns sleep disturbance to the loss-of-function class at cohort level.

Autistic behavior OCCASIONAL HP:0000729

Show evidence (1 reference)

PMID:24721225 SUPPORT Human Clinical

"are characterized by severe ID with autistic features, epilepsy, short stature and behavioral problems such as self injury and aggressive outbursts"

Names autistic features explicitly, in the GRIA3 pedigree where they were reported, together with the co-occurring behavioural problems.

Self-injurious behavior OCCASIONAL HP:0100716

Show evidence (1 reference)

PMID:24721225 SUPPORT Human Clinical

"are characterized by severe ID with autistic features, epilepsy, short stature and behavioral problems such as self injury and aggressive outbursts"

Names self injury explicitly among the behavioural problems of the GRIA3 pedigree.

Aggressive behavior OCCASIONAL HP:0000718

Show evidence (1 reference)

PMID:42666715 SUPPORT Human Clinical

"In addition, III-1 and II-3 exhibit violent tendencies, emotional instability, delusions, and hallucinations."

Documents aggression together with affective and psychotic features in two affected relatives.

Psychosis OCCASIONAL HP:0000709

Show evidence (1 reference)

PMID:42666715 SUPPORT Human Clinical

"Their behavioral manifestations may include emotional instability, delusions, hallucinations, and other psychiatric symptoms."

Records delusions and hallucinations as part of the behavioural spectrum of GRIA3-related disease.

Cerebellar vermis hypoplasia VERY_RARE HP:0001320

Sequelae: Ataxia

Show evidence (1 reference)

PMID:34731330 SUPPORT Human Clinical

"Cerebral MRI of our proband highlighted cerebellar vermis hypoplasia and a focal cortical dysplasia."

Direct imaging report of cerebellar vermis hypoplasia in a GRIA3-variant patient.

Ataxia VERY_RARE HP:0001251

Show evidence (1 reference)

PMID:34731330 SUPPORT Human Clinical

"Neurological examination was characterized by a cerebellar syndrome with ataxia, tremor and dysmetria."

Documents the clinical cerebellar syndrome in a GRIA3-variant proband.

Cerebral atrophy VERY_RARE HP:0002059

Show evidence (2 references)

PMID:36726007 SUPPORT Human Clinical

"Brain magnetic resonance imaging revealed mild frontal lobe atrophy and slight ventricular enlargement"

Imaging report of frontal atrophy and ventriculomegaly in a GRIA3 patient.

PMID:36726007 SUPPORT Human Clinical

"Slight frontal lobe atrophy and ventricular enlargement were not aggravated."

Records that the structural findings had not worsened by the age-13 scan, which is why this is not curated as a neurodegenerative phenotype. The paper reports one scan and does not give a baseline date, so the interval itself is not established.

Ventriculomegaly VERY_RARE HP:0002119

Show evidence (1 reference)

PMID:36726007 SUPPORT Human Clinical

"Brain magnetic resonance imaging revealed mild frontal lobe atrophy and slight ventricular enlargement"

Imaging report documenting ventricular enlargement.

Growth 1

Short stature VERY_RARE HP:0004322

Show evidence (1 reference)

PMID:34731330 SUPPORT Human Clinical

"Moreover, he showed short stature, low weight, relative macrocephaly and facial dysmorphisms."

Documents short stature with the associated growth and craniofacial features in a GRIA3-variant proband.

Other 6

Hyporeflexia OCCASIONAL HP:0001265

Show evidence (1 reference)

PMID:41462794 SUPPORT Human Clinical

"The neurological phenotype is generally severe, with a combination of hypotonia, hypertonia, movement disorders, and hyporeflexia"

Lists hyporeflexia as part of the neurological phenotype alongside the two opposite tone states.

Focal motor seizure OCCASIONAL HP:0011153

Show evidence (1 reference)

PMID:38038360 SUPPORT Human Clinical

"Twelve patients had seizures, including focal motor (6/12), unknown onset motor (4/12), focal impaired awareness (1/12), (atypical) absence (2/12), myoclonic (5/12) and generalized tonic-clonic (1/12) or atonic (1/12) seizures."

Enumerates the seizure semiologies with focal motor seizures as the most frequent type.

Non-convulsive status epilepticus VERY_RARE Status epilepticus without prominent motor symptoms HP:0031475

Show evidence (2 references)

PMID:41462794 SUPPORT Human Clinical

"This is the first reported case of NCSE in a female patient with a GRIA3 variant."

Establishes the female case as newly described. Note the scope of the claim: the paper states two paragraphs earlier that status epilepticus was already documented in two patients, so this is the first female case rather than the first case.

PMID:41462794 SUPPORT Human Clinical

"Status epilepticus (SE) has been documented in two cases."

Gives the total number of reported status epilepticus cases, which is why this phenotype is graded VERY_RARE rather than presented as a novel single observation.

Hypotonia FREQUENT Appendicular hypotonia HP:0012389

Show evidence (2 references)

PMID:38038360 SUPPORT Human Clinical

"Limb muscular hypotonia was reported in 13/25, and hypertonia in 10/25."

Gives the cohort frequency of hypotonia alongside the competing tone phenotype.

PMID:38038360 SUPPORT Human Clinical

"Patients with loss-of-function variants were older at the time of seizure onset (median age: 16 months), hypotonic and had sleeping disturbances."

Assigns hypotonia specifically to the loss-of-function class.

Spastic gait OCCASIONAL HP:0002064

Show evidence (1 reference)

PMID:41462794 SUPPORT Human Clinical

"Over the following years, she developed a paraparetic spastic gait with hyperreflexia, expressive language impairment, and moderate intellectual disability (ID)."

Documents the spastic gait phenotype and its co-occurrence with hyperreflexia.

Hip dislocation VERY_RARE HP:0002827

Show evidence (1 reference)

PMID:36726007 SUPPORT Human Clinical

"She now presents with severe developmental delay, scoliosis and hip dislocation."

Reports hip dislocation in a severely affected GRIA3 patient.

🧬

Genetic Associations

1

GRIA3 (Sole causative gene. GRIA3 maps to Xq25 and encodes GluA3, the only X-chromosomal AMPA receptor subunit. Reported allele classes span missense, canonical splice-site, frameshift, multi-exon deletion and duplication, and translocations disrupting the locus.)

Gene: GRIA3 hgnc:4573 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (3 references)

PMID:38038360 SUPPORT In Vitro

"Here, we evaluated the impact on AMPAR function of one frameshift and 43 rare missense GRIA3 variants identified in patients with NDD by electrophysiological assays."

Describes the systematic functional screen behind the loss-of-function versus gain-of-function classification used throughout this entry.

PMID:38038360 SUPPORT In Vitro

"Thirty-one variants alter receptor function and show loss-of-function or gain-of-function properties, whereas 13 appeared neutral."

Quantifies the functionally neutral fraction, which is the reason variant interpretation in this gene needs functional data rather than in-silico prediction alone.

PMID:24721225 SUPPORT Human Clinical

"One novel missense mutation (c.1888G > C) was found in GRIA3"

Independent X-exome study identifying a segregating GRIA3 missense allele in a Finnish X-linked intellectual disability family.

Variants (6)

c.1844C>T p.Ala615Val

De novo hemizygous missense allele in a male. The functionally best-characterised gain-of-function allele in the disorder: patch clamp showed slowed desensitisation and deactivation, a transgenic fly assay confirmed a gain-of-function genetic interaction, and both seizures and hypertonia responded to carbamazepine.

Show evidence (1 reference)

PMID:35031858 SUPPORT Human Clinical

"We identified a hemizygous de novo missense variant in GRIA3 in a boy with an NDD: c.1844C > T (p.Ala615Val) using whole-exome sequencing."

Establishes the allele, its zygosity and its de novo origin in the index male.

c.1982T>C p.Met661Thr Likely Pathogenic

De novo heterozygous missense allele in a female with developmental and epileptic encephalopathy, sitting in the M3-S2 linker next to the functionally confirmed gain-of-function residue p.Arg660. Absent from EVS, 1000 Genomes, dbSNP, gnomAD and HGVD. Direct electrophysiology was not performed, so its gain-of-function status is inferred from position and from the hypertonic phenotype rather than measured.

Show evidence (2 references)

PMID:36726007 SUPPORT Human Clinical

"Here, we report a female patient with developmental and epileptic encephalopathy who carries the novel de novo GRIA3 variant NM_007325.5: c.1982T > C: p.Met661Thr."

Establishes the allele, its de novo origin and the affected female carrier.

PMID:36726007 SUPPORT Human Clinical

"the variant was classified as likely pathogenic (PS2, PM2, PP2, PP3)"

Records the ACMG classification and the specific criteria applied.

p.Ala653Thr

Missense allele in the transmembrane ion-channel gate that stabilises the receptor in a closed conformation, so it is a loss-of-function allele that acts without reducing protein. Segregated in a sibship with severe developmental delay and the most extreme sleep-wake disorganisation reported in the disorder, and was modelled by CRISPR knock-in in mouse.

Show evidence (1 reference)

PMID:29016847 SUPPORT In Vitro

"In vitro, the GRIA3(A653T) mutation stabilizes the channel in a closed conformation, in contrast to Lurcher."

Defines the biophysical consequence that makes this a loss-of-function rather than a leaky-channel allele.

c.1969A>G p.Thr657Ala

Novel de novo missense allele in a seven-year-old female presenting with developmental delay, spastic gait and non-convulsive status epilepticus — the mildest reported female course despite a severe acute epileptic episode.

Show evidence (1 reference)

PMID:41462794 SUPPORT Human Clinical

"we present the case of a seven-year-old female patient presenting with developmental delay, spastic gait, and non-convulsive status epilepticus (NCSE), who was found to carry a novel de novo GRIA3 missense variant (c.1969A > G; p.Thr657Ala)."

Establishes the allele, its de novo origin and the associated clinical presentation.

c.268+1G>C Likely Pathogenic

Canonical splice-donor variant reclassified from a variant of uncertain significance to likely pathogenic after co-segregation analysis and a minigene assay showing exon 2 skipping. Segregated in an X-linked pedigree with intellectual disability, prominent psychiatric symptoms and spatial memory deficits.

Show evidence (2 references)

PMID:42666715 SUPPORT Human Clinical

"we reported a pedigree that carried a novel splicing site variant of GRIA3 (c.268 + 1G>C) by whole exome sequencing (WES) and co-segregation analysis"

Establishes the allele and its segregation in the reported family.

PMID:42666715 SUPPORT In Vitro

"The minigene assay further confirmed that this variant lead to exon 2 skipping."

RNA-level functional evidence that upgraded the variant classification.

c.2360A>G p.Glu787Gly

Familial missense allele transmitted by a healthy carrier mother in an Italian pedigree whose proband had severe intellectual disability, myoclonic status epilepticus, cerebellar vermis hypoplasia and short stature.

Show evidence (1 reference)

PMID:34731330 SUPPORT Human Clinical

"Whole exome sequencing identified a novel variant in GRIA3, c.2360A > G, p.(Glu787Gly)."

Establishes the allele identified in the index subject.

💊

Medical Actions

6

Carbamazepine for Gain-of-Function Disease

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: carbamazepine CHEBI:3387

The one genotype-guided treatment observation in the disorder. In a male with the functionally confirmed gain-of-function allele p.Ala615Val, carbamazepine — which reduces presynaptic glutamate release rather than acting on the receptor itself — improved both seizures and hypertonia. This is an N-of-1 result and is explicitly not generalisable across the disorder: in a female whose allele was never functionally tested, carbamazepine was ineffective. Because the rationale is to reduce glutamatergic drive onto an over-active receptor, the same drug would not be expected to help, and could plausibly harm, a patient whose receptors are already under-conducting.

Mechanism Target:

INHIBITS Prolonged AMPA Receptor-Mediated Excitatory Current — Reducing presynaptic glutamate release lowers the agonist transient reaching the slow-deactivating mutant receptor, shortening the excess charge transfer per synaptic event without acting on the channel itself.

Show evidence (1 reference)

PMID:35031858 SUPPORT Human Clinical

"His seizures and hypertonia were ameliorated by carbamazepine, inhibiting glutamate release from presynapses."

States both the clinical response and the presynaptic mechanism by which the drug is proposed to act on this node.

Show evidence (3 references)

PMID:35031858 SUPPORT Human Clinical

"GRIA3 GOF variants may cause an NDD phenotype distinctive from that of LOF variants, and drugs suppressing glutamatergic neurotransmission may ameliorate this phenotype."

The authors' own generalisation: suppressing glutamatergic transmission is the mechanistic rationale, and it is explicitly tied to the gain-of-function class.

PMID:36726007 REFUTE Human Clinical

"Treatment with carbamazepine and ethosuximide was ineffective."

Contradicts any claim that carbamazepine works across GRIA3 disease. This patient's p.Met661Thr allele was never functionally tested, so the failure is consistent with the mechanism-matched reading of the drug rather than with a general benefit.

PMID:36726007 SUPPORT Human Clinical

"In our case, carbamazepine was ineffective, possibly because it does not act directly on AMPAR but inhibits glutamate release from presynaptic neurons"

Independently confirms the indirect, presynaptic mechanism of action recorded on the mechanism link, while noting it as the reason the drug can fail.

Multi-Agent Antiseizure Pharmacotherapy

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: lamotrigine CHEBI:6367 clobazam CHEBI:31413 levetiracetam CHEBI:6437 lacosamide CHEBI:135939 midazolam CHEBI:6931

Seizures are frequently drug-resistant at onset but control often improves over time with sequential or combined conventional antiseizure medication. In the p.Met661Thr female, seizures initially resistant to carbamazepine and ethosuximide were gradually brought under control with lamotrigine, clobazam, levetiracetam and lacosamide. In the p.Thr657Ala female, non-convulsive status epilepticus resolved to baseline with levetiracetam and midazolam. There is no evidence that any of these agents is preferred on mechanistic grounds; selection follows general epilepsy practice by seizure type and EEG.

Target Phenotypes: Seizure HP:0001250 Non-convulsive status epilepticus HP:0002133

Show evidence (2 references)

PMID:36726007 SUPPORT Human Clinical

"The seizures, initially resistant to drug treatment, were gradually brought under control using lamotrigine, clobazam, levetiracetam, and lacosamide."

Names the four agents that achieved control after initial drug resistance in a GRIA3 patient.

PMID:41462794 SUPPORT Human Clinical

"Following intensive treatment with levetiracetam and midazolam, the patient gradually recovered to her baseline neurological status."

Documents resolution of non-convulsive status epilepticus with conventional agents.

Antipsychotic Pharmacotherapy for Psychiatric Manifestations

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: risperidone CHEBI:8871 clozapine CHEBI:3766

Adult affected males in GRIA3 pedigrees can present with delusions, hallucinations, emotional instability and violent behaviour that dominate the clinical picture. Risperidone and clozapine were reported to be effective, and lorazepam improved sleep, in an X-linked splice-variant family. These are uncontrolled observations from a single pedigree.

Target Phenotypes: Delusions and hallucinations HP:0000709 Aggressive outbursts HP:0000718

Show evidence (1 reference)

PMID:42666715 SUPPORT Human Clinical

"Risperidone and clozapine demonstrated good efficacy, while lorazepam effectively improved sleep disturbances."

Reports the observed response of psychiatric and sleep symptoms to these agents in the affected family.

Lorazepam for Sleep Disturbance

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: lorazepam CHEBI:6539

Sleep disruption is one of the most burdensome features on the loss-of-function side, both for the patient and for caregivers, and no disease-specific sleep intervention has been studied. Lorazepam was reported to improve sleep in the affected members of an X-linked GRIA3 pedigree. This is an uncontrolled observation in one family, reported alongside the antipsychotic response rather than as a separate trial.

Target Phenotypes: Sleep-wake cycle disturbance HP:0006979

Show evidence (1 reference)

PMID:42666715 SUPPORT Human Clinical

"Risperidone and clozapine demonstrated good efficacy, while lorazepam effectively improved sleep disturbances."

Reports the sleep response to lorazepam in the same sentence that reports the antipsychotic response, in the same pedigree.

Genetic Counseling and Prenatal Diagnosis

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

Once a familial GRIA3 allele is identified, cascade testing of at-risk maternal relatives, carrier testing, and prenatal or preimplantation genetic testing become available. A carrier mother has a 50 percent chance of transmitting the allele in each pregnancy, with the expected consequence depending on fetal sex, the variant's functional direction and, in females, X-chromosome inactivation. A de novo result lowers but does not eliminate recurrence risk, because parental germline mosaicism cannot be excluded.

Show evidence (1 reference)

PMID:42666715 SUPPORT Human Clinical

"our results further support that this variant is likely pathogenic and may be the cause of their phenotype, which also provide evidence for its prenatal diagnosis and genetic counseling"

States that establishing the variant's pathogenicity is what enables prenatal diagnosis and counselling in the family.

Supportive and Rehabilitative Care

Category: Therapeutic Action: Supportive Care NCIT:C15747

Management is multidisciplinary and phenotype-directed: early intervention, individualised education, speech and augmentative communication therapy, occupational and physical therapy, tone management, orthopaedic surveillance for scoliosis and hip dislocation, behavioural support and sleep intervention. No disease-modifying or gene-directed therapy exists. This entry records the standard-of-care package rather than a GRIA3-specific intervention, and no GRIA3-specific trial of any of these components has been published.

Target Phenotypes: Global developmental delay HP:0001263 Delayed speech and language development HP:0000750

🔬

Diagnosis

4

Trio Exome or Genome Sequencing

First-line molecular test. There is no biochemical marker, enzyme assay or imaging finding that establishes this diagnosis, so it rests entirely on identifying a GRIA3 variant. Sequencing the proband with both parents is what establishes de novo status, which carries substantial ACMG weight here (PS2) and is also the finding that most often flags a gain-of-function allele, since affected females are typically de novo heterozygotes.

trio whole exome sequencing NCIT:C101295

Results: A rare GRIA3 variant absent from population databases, with parental samples establishing whether it arose de novo or was transmitted by a carrier mother.

Show evidence (2 references)

PMID:36726007 SUPPORT Human Clinical

"performed whole-exome sequencing and variant filtering for pathogenicity in the patient and her parents"

Describes the trio design that established de novo status in the index female.

PMID:41462794 SUPPORT Human Clinical

"Whole-exome sequencing (WES) identified a novel de novo variant in GRIA3, c."

Independent case in which exome sequencing was the test that made the diagnosis.

Copy-Number-Sensitive Testing

Not optional in this gene. GRIA3 disease is caused by multi-exon deletions and duplications and by translocations disrupting the locus as well as by point variants, and standard exome SNV and indel analysis will miss them. Chromosomal microarray or read-depth or MLPA-based exon-level dosage analysis therefore belongs in the workup rather than being reserved for when sequencing is negative — and a normal microarray does not exclude the diagnosis, since it is routinely normal in the point-variant cases.

chromosomal microarray and exon-level dosage analysis NCIT:C19770

Results: An Xq25 deletion, duplication or rearrangement involving GRIA3, or a normal result that does not exclude the diagnosis.

The clearest published illustration — a hemizygous exon 5-12 deletion found only after targeted comprehensive testing followed an unrevealing SNV and indel analysis, and later detected prenatally in amniotic fluid — is in a journal with no PubMed or PMC record, so it cannot be quoted as an evidence snippet and is described here instead. The cited evidence below is the weaker but citable form of the same point: microarray is performed and is normal in the point-variant cases.

Show evidence (1 reference)

PMID:36726007 SUPPORT Human Clinical

"Microarray analysis did not show any pathogenic copy number variants."

Records microarray as part of the diagnostic workup and its normal result in a patient whose causal variant was a point variant, which is why a normal microarray cannot exclude the diagnosis.

RNA or Minigene Study for a Splice Variant of Uncertain Significance

A canonical splice-site GRIA3 variant cannot be classified on sequence alone. Patient RNA, RT-PCR, or a minigene reporter demonstrates whether the allele actually alters exon inclusion, and that result is what moves the classification. The worked example is c.268+1G>C, reclassified from a variant of uncertain significance to likely pathogenic on the strength of demonstrated exon 2 skipping together with co-segregation.

minigene splicing assay NCIT:C19770

Results: Demonstrated aberrant splicing, which supplies the functional criterion needed to upgrade a splice variant of uncertain significance.

Show evidence (1 reference)

PMID:42666715 SUPPORT In Vitro

"According to ACMG guidelines, We reclassified previously variant of unknown significance (VUS) into "likely pathogenic" through co-segregates analysis and minigene assay."

States the classification change and names the two lines of evidence that produced it, one of which is the splicing assay this diagnostic step performs.

Functional Electrophysiology for a Missense Variant of Uncertain Significance

The step that connects diagnosis to treatment in this disorder. A rare GRIA3 missense variant may be loss of function, gain of function, or functionally neutral, and nothing about its rarity or its domain location distinguishes those. Patch-clamp characterisation in a heterologous system is what assigns the direction, and the direction is what the entry's mechanism-matched treatment argument depends on. This is currently a research or advanced-diagnostics assay rather than a routinely available clinical test, which is a real limit on that argument.

patch-clamp functional characterisation of a GRIA3 missense allele NCIT:C19770

Results: Assignment of the allele to the loss-of-function, gain-of-function, or functionally neutral class.

Show evidence (2 references)

PMID:38038360 SUPPORT In Vitro

"Thirty-one variants alter receptor function and show loss-of-function or gain-of-function properties, whereas 13 appeared neutral."

Nearly a third of tested rare missense alleles were functionally neutral, which is the reason this step is needed rather than optional: sequence-level interpretation alone cannot separate the three classes.

PMID:38038360 SUPPORT In Vitro

"Here, we evaluated the impact on AMPAR function of one frameshift and 43 rare missense GRIA3 variants identified in patients with NDD by electrophysiological assays."

Describes the assay applied at scale to patient-identified variants, establishing it as a practicable route to a functional classification.

📊

Prevalence

1

Worldwide

Cases In Literature Ultra Rare

No population-based prevalence, incidence or carrier-frequency estimate exists. The largest published series is 25 functionally characterised patients from 23 families, and fewer than a hundred individuals have been described in total, so only a qualitative ultra-rare band is defensible. A rate per 100,000 cannot be responsibly derived from case reports and is deliberately left unset.

Show evidence (2 references)

PMID:38038360 SUPPORT Human Clinical

"We collected detailed clinical data from 25 patients (from 23 families) harbouring 17 of these variants."

The largest assembled cohort is 25 patients from 23 families, which is the scale of the published literature and the basis for the ultra-rare classification.

PMID:36726007 SUPPORT Human Clinical

"Approximately 20 variants have been reported, including balanced translocation, deletion, duplication, and missense variants."

Independent confirmation that the total reported variant count was in the dozens, not a population-scale figure.

🧫

Experimental Models

2

Heterologous AMPA receptor expression with patch-clamp electrophysiology CELL_LINE

Recombinant expression of wild-type and variant GluA3 in a heterologous cell system, recorded by patch clamp, is the assay that assigns each GRIA3 allele to the loss-of-function, gain-of-function or functionally neutral class. It is the method behind the taxonomy on which this entry's whole pathograph branches.

Organism

human NCBITaxon:9606

Publication

PMID:38038360

Pathograph links

GluA3 Gain of Function measures fidelity: moderate Measures agonist potency, response time course, desensitisation and deactivation, from which the gain-of-function direction is assigned.

Limitations: Recombinant receptors of defined subunit composition lack the auxiliary-subunit environment, developmental context and native heterotetramer stoichiometry of a real synapse, so the measured kinetics predict direction but not magnitude of circuit effect.

Readouts

Receptor desensitisation and deactivation kinetics

Direction: ALTERED

Interpretation: Slowed desensitisation and deactivation define the gain-of-function class.

Show evidence (1 reference)

PMID:35031858 SUPPORT In Vitro

"Patch-clamp recordings showed that the human GluA3 mutant (p.Ala615Val) had slower desensitization and deactivation kinetics."

Reports the measured kinetic parameters that define the gain-of-function assignment.

Show evidence (1 reference)

PMID:37921875 SUPPORT In Vitro

"These variants produce changes in agonist EC50, response time course, desensitization, and/or receptor surface expression."

Establishes the parameter set the assay reports and that it discriminates functional consequences of GRIA variants.

GluA3 Loss of Function measures fidelity: moderate The same assay assigns loss of function, including the closed-channel mechanism that leaves protein expression intact.

Limitations: Cannot distinguish reduced current caused by fewer surface receptors from reduced current per receptor without a separate surface-expression measurement, and gives no information about tissue-specific transcript abundance for splice alleles.

Show evidence (1 reference)

PMID:38038360 SUPPORT In Vitro

"Here, we evaluated the impact on AMPAR function of one frameshift and 43 rare missense GRIA3 variants identified in patients with NDD by electrophysiological assays."

Describes the assay and the scale at which it was applied to assign functional class.

HEK293T minigene splicing assay CELL_LINE

Minigene reporter assay used to resolve GRIA3 splice-site variants of uncertain significance, by testing directly whether the candidate allele alters exon inclusion.

Organism

human NCBITaxon:9606

Publication

PMID:42666715

Pathograph links

GluA3 Loss of Function measures fidelity: moderate Demonstrates the RNA-level lesion — exon 2 skipping — through which a canonical splice-donor variant abolishes normal GluA3 production.

Limitations: A minigene reports splice-site strength in an artificial construct in a non-neuronal cell line; it validates aberrant splicing but not the transcript abundance or isoform ratio in patient brain.

Readouts

Exon 2 inclusion in the minigene transcript

Direction: DECREASED

Interpretation: Exon 2 skipping is the loss-of-function mechanism for this allele.

Show evidence (1 reference)

PMID:42666715 SUPPORT In Vitro

"The minigene in vitro splicing assay demonstrated that this variant affects splicing, leading to exon 2 skipping"

Reports the measured splicing outcome.

🐁

Animal Models

3

Gria3 knockout mouse Genetically engineered

Constitutive germline null allele in hemizygous males. Reproduces behavioural and monoaminergic consequences of losing GluA3 but not the defining human cognitive phenotype.

Species

Mus musculus

Genotype

Gria3-/Y germline knockout on C57BL/6J background

Background

C57BL/6J

Genes

Gria3 hgnc:4573

Publication

PMID:22285418

Pathograph links

GluA3 Loss of Function recapitulates fidelity: moderate A null allele is the cleanest available model of complete GluA3 loss of function and isolates the consequences of absent GluA3 from any residual mutant-subunit effect.

Limitations: A complete null is not what most patients carry: human loss-of-function alleles are usually missense or splice changes that still produce a subunit which is incorporated into heterotetramers, so a knockout cannot report dominant-negative or assembly effects. The null is also constitutive and whole-body rather than neuron- or stage-restricted.

Readouts

Isolation-induced male aggression

Direction: INCREASED

Interpretation: Behavioural consequence of absent GluA3, matching the aggressive outbursts described in affected adult males.

Show evidence (1 reference)

PMID:22285418 SUPPORT Model Organism

"Compared to wild type (WT) littermates (n=14), Gria3-/Y mice (n=13) showed an increase in isolation-induced male aggression (p=0.011) in home cage resident-intruder test"

Reports the measured increase in aggression with its comparator and significance.

Striatal dopamine concentration

Direction: INCREASED

Interpretation: Neurochemical correlate of GluA3 loss, indicating that the lesion propagates into monoaminergic circuitry rather than staying confined to glutamatergic synapses.

Show evidence (1 reference)

PMID:22285418 SUPPORT Model Organism

"Increased dopamine concentrations in stratum (p=0.034) and reduced serotonin turnover in olfactory bulb (p=0.002) were documented in Gria3-/Y mice."

Reports the measured striatal dopamine increase and the olfactory-bulb serotonin change.

Show evidence (1 reference)

PMID:22285418 SUPPORT Model Organism

"These results support a role of GluA3 in the modulation of social behavior through brain dopamine and/or serotonin signaling and different AMPA receptor subunits affect social behavior through distinct mechanisms."

The authors' own conclusion that the knockout is informative for GluA3-dependent behavioural regulation.

Disturbed Excitatory Synaptic Transmission and Plasticity fails to recapitulate fidelity: low The knockout does not reproduce the cognitive impairment that defines the human disorder. Spatial memory was intact on both the Morris water maze and the Y-maze, so the model cannot be used to read out the learning-and-memory limb of this node.

Limitations: Rodent spatial navigation tasks are a narrow and species-specific proxy for human global developmental impairment, so an intact result does not prove the node is unaffected — only that this model does not report it. Compensation by GluA1- and GluA2-containing receptors during development is a plausible explanation that the study does not exclude.

Readouts

Spatial memory in Morris water maze and Y-maze

Direction: UNCHANGED

Interpretation: A genuine negative result: the cognitive readout most analogous to the human phenotype is unaffected in the null mouse.

Show evidence (1 reference)

PMID:22285418 SUPPORT Model Organism

"Gria3-/Y mice showed no significant deficit in spatial memory function in Morris-water maze and Y-maze tests, and normal levels of testosterone."

Reports the negative spatial memory result that grounds the failure to recapitulate.

Show evidence (1 reference)

PMID:22285418 SUPPORT Model Organism

"Gria3-/Y mice showed no significant deficit in spatial memory function in Morris-water maze and Y-maze tests, and normal levels of testosterone."

Substantiates the negative claim that this model does not reproduce the cognitive consequence of disturbed excitatory transmission.

Gria3 A653T knock-in mouse Genetically engineered

Allele-specific knock-in of the orthologue of the human closed-channel loss-of-function variant, generated to test whether that allele explains the extreme sleep-wake phenotype in the index sibship. It is the strongest allele-level human-to-mouse concordance in the disorder.

Species

Mus musculus

Genotype

Gria3 A653T hemizygous CRISPR-Cas9 knock-in

Genes

Gria3 hgnc:4573

Publication

PMID:29016847

Pathograph links

Reduced AMPA Receptor-Mediated Excitatory Current partially recapitulates fidelity: moderate Carries the exact human loss-of-function allele and reproduces the sleep-architecture and light-sensitivity consequences attributed to reduced GluA3 current in the patients.

Limitations: Reproduces the sleep and circadian limb of the phenotype but not the developmental delay, epilepsy or tone abnormalities, so it models one downstream consequence of the reduced current rather than the disorder. Mouse sleep is polyphasic and its architecture is not directly comparable to the multi-day human wake and sleep periods that motivated the model.

Readouts

Number of brief activity and sleep bouts

Direction: DECREASED

Interpretation: Loss of the normal polyphasic sleep structure, the murine counterpart of the very long consolidated wake and sleep periods seen in the patients.

Show evidence (1 reference)

PMID:29016847 SUPPORT Model Organism

"The Gria3A653T mouse showed significantly fewer brief bouts of activity and sleep than the wild-types."

Reports the measured change in sleep and activity bout structure.

Circadian period lengthening under constant light

Direction: INCREASED

Interpretation: Enhanced circadian sensitivity to light in the mutant, indicating that reduced GluA3 current alters photic entrainment as well as sleep consolidation.

Show evidence (1 reference)

PMID:29016847 SUPPORT Model Organism

"Gria3A653T mice showed enhanced period lengthening under constant light compared to wild-type mice, suggesting an increased sensitivity to light."

Reports the measured circadian phenotype under constant light.

Show evidence (1 reference)

PMID:29016847 SUPPORT Model Organism

"We introduced the orthologous mutation into a mouse strain by CRISPR-Cas9 mutagenesis and found that hemizygous mutants displayed significant differences in the structure of their activity and sleep compared to wild-type littermates."

Establishes that the model carries the orthologous patient allele and that it produces a measurable phenotype, which is what makes it informative for this node.

Transgenic Drosophila expressing mutant human GluA3 Genetically engineered

Heterologous in vivo assay used to test whether the p.Ala615Val allele behaves as a gain of function. The mutant produced developmental defects only when combined with a leaky-channel alteration, a genetic interaction consistent with excess channel activity.

Species

Drosophila melanogaster

Genotype

transgenic expression of human GluA3 p.Ala615Val combined with the Lurcher leaky-channel alteration

Publication

PMID:35031858

Pathograph links

GluA3 Gain of Function measures fidelity: low Reads out the functional direction of a human allele through a developmental phenotype in a whole organism, complementing the patch-clamp measurement.

Limitations: Drosophila has no orthologous AMPA receptor heterotetramer and the assay requires co-expression with an artificial leaky-channel allele, so it reports the direction of the effect rather than any disease-relevant circuit consequence.

Show evidence (1 reference)

PMID:35031858 SUPPORT Model Organism

"A fly line expressing a human GluA3 mutant possessing our variant and the Lurcher variant, which makes ion channels leaky, showed developmental defects, while one expressing a mutant possessing either of them did not."

The synthetic genetic interaction with a leaky-channel allele is the in vivo readout for gain of function.

{ }

Source YAML

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name: Syndromic X-linked Intellectual Disability 94
creation_date: "2026-09-04T02:26:58Z"
category: Mendelian
description: >-
  Syndromic X-linked intellectual disability 94 (MRXSW, Wu type; MONDO:0010402) is an
  ultra-rare X-linked neurodevelopmental disorder caused by germline variants in GRIA3
  (Xq25), which encodes GluA3, the only X-chromosomal subunit of the AMPA-type ionotropic
  glutamate receptor. The disorder is not a single haploinsufficiency syndrome: pathogenic
  GRIA3 alleles split into loss-of-function (LoF) and gain-of-function (GoF) classes that
  produce partly opposite phenotypes. In the largest functionally characterised cohort
  (25 patients from 23 families), all had global developmental impairment, while LoF was
  associated with later seizure onset, hypotonia and sleep disturbance, and GoF with much
  earlier seizure onset, hypertonia and movement disorder including hyperekplexia.
  Hyperreflexia is reported in the single functionally confirmed GoF male rather than as a
  cohort-level association. Affected males usually carry hemizygous LoF alleles inherited from healthy
  carrier mothers; affected females mostly carry de novo heterozygous GoF alleles. The
  allelic direction is therapeutically consequential — carbamazepine, which suppresses
  presynaptic glutamate release, ameliorated seizures and hypertonia in a functionally
  confirmed GoF case, and a drug that dampens AMPAR signalling would be expected to be
  unhelpful or harmful in LoF disease.
disease_term:
  preferred_term: syndromic X-linked intellectual disability 94
  term:
    id: MONDO:0010402
    label: syndromic X-linked intellectual disability 94
synonyms:
- MRXSW
- MRX94
- syndromic X-linked intellectual disability Wu type
- intellectual developmental disorder, X-linked, syndromic, Wu type
- syndromic X-linked intellectual disability 29
- GRIA3-related neurodevelopmental disorder
parents:
- X-linked syndromic intellectual disability
categories:
- Neurodevelopmental disorder
- Channelopathy
- X-linked disorder

inheritance:
- name: X-linked inheritance with mechanism-dependent expression in females
  inheritance_term:
    preferred_term: X-linked inheritance
    term:
      id: HP:0001417
      label: X-linked inheritance
  expressivity: VARIABLE
  description: >-
    GRIA3 is X-chromosomal, so transmission follows an X-linked pattern, but a single
    recessive/dominant label does not describe the disorder. Affected males most often carry
    a hemizygous loss-of-function allele inherited from a clinically healthy carrier mother,
    while affected females most often carry a de novo heterozygous gain-of-function allele.
    Both variant classes are disease-causing in both sexes.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Loss-of-function and gain-of-function variants were disease-causing in both sexes but affected males often carried de novo or hemizygous loss-of-function variants inherited from healthy mothers, whereas affected females had mostly de novo heterozygous gain-of-function variants."
    explanation: >-
      States the sex- and mechanism-dependent transmission pattern that this inheritance
      block records, including that both allele classes affect both sexes.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AMPARs form by homo- or heteromeric assembly of subunits encoded by the GRIA1-GRIA4 genes, of which only GRIA3 is X-chromosomal."
    explanation: >-
      Establishes that GRIA3 is the X-chromosomal member of the AMPA receptor subunit family,
      which is why this disorder alone among the GRIA disorders is X-linked.
- name: X-linked recessive inheritance in carrier-mother pedigrees
  inheritance_term:
    preferred_term: X-linked recessive inheritance
    term:
      id: HP:0001419
      label: X-linked recessive inheritance
  penetrance: UNKNOWN
  description: >-
    The historical Wu-type pedigrees are classic X-linked recessive families in which
    hemizygous males are affected and heterozygous carrier mothers are clinically normal or
    only mildly affected. This describes many familial loss-of-function pedigrees but is
    incomplete for de novo gain-of-function disease.
  evidence:
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "GRIA3 is located on the X-chromosome, and pathogenic variants may be transmitted from unaffected carrier mothers to affected male offspring, a pattern typical of several X-linked neurodevelopmental disorders"
    explanation: >-
      Describes the carrier-mother-to-affected-son transmission that defines the recessive
      pedigree pattern.
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The GRIA3 gene maps to chromosome Xq25 and the c.2360A > G variant was transmitted by his healthy mother."
    explanation: >-
      Worked example of maternal transmission of a pathogenic GRIA3 allele from a clinically
      healthy carrier to an affected son.

prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    No population-based prevalence, incidence or carrier-frequency estimate exists. The
    largest published series is 25 functionally characterised patients from 23 families, and
    fewer than a hundred individuals have been described in total, so only a qualitative
    ultra-rare band is defensible. A rate per 100,000 cannot be responsibly derived from
    case reports and is deliberately left unset.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We collected detailed clinical data from 25 patients (from 23 families) harbouring 17 of these variants."
    explanation: >-
      The largest assembled cohort is 25 patients from 23 families, which is the scale of the
      published literature and the basis for the ultra-rare classification.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Approximately 20 variants have been reported, including balanced translocation, deletion, duplication, and missense variants."
    explanation: >-
      Independent confirmation that the total reported variant count was in the dozens, not a
      population-scale figure.

pathophysiology:
- name: GRIA3 Pathogenic Variant
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    A germline sequence or structural alteration of GRIA3 at Xq25 — missense, canonical
    splice-site, frameshift, multi-exon deletion or duplication, or a translocation
    disrupting the locus — is the initiating lesion. GRIA3 encodes GluA3, the sole
    X-chromosomal member of the GRIA1-GRIA4 family that assembles into AMPA-type ionotropic
    glutamate receptors, so a single hemizygous allele in a male is sufficient and a
    heterozygous allele in a female acts against a mosaic wild-type background.
  genes:
  - preferred_term: GRIA3
    term:
      id: hgnc:4573
      label: GRIA3
  downstream:
  - target: GluA3 Loss of Function
    causal_link_type: DIRECT
    description: >-
      Splice disruption, protein truncation, exon deletion, or a missense change that
      stabilises a non-conducting channel removes GluA3-mediated current.
    evidence:
    - reference: PMID:42666715
      reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "The minigene assay further confirmed that this variant lead to exon 2 skipping."
      explanation: >-
        Demonstrates that a GRIA3 splice-site allele produces aberrant transcript processing,
        the transcriptional route from variant to loss of GluA3 function.
  - target: GluA3 Gain of Function
    causal_link_type: DIRECT
    description: >-
      A subset of missense alleles in and around the channel gate instead slows receptor
      desensitisation and deactivation, prolonging rather than abolishing current.
    evidence:
    - reference: PMID:35031858
      reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Patch-clamp recordings showed that the human GluA3 mutant (p.Ala615Val) had slower desensitization and deactivation kinetics."
      explanation: >-
        Patch-clamp of the mutant receptor establishes that this class of GRIA3 variant acts
        by prolonging channel gating rather than by removing function.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AMPARs form by homo- or heteromeric assembly of subunits encoded by the GRIA1-GRIA4 genes, of which only GRIA3 is X-chromosomal."
    explanation: >-
      Identifies GRIA3 as the X-chromosomal AMPA receptor subunit gene whose alteration is the
      initiating lesion of this disorder.
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the causative role of GRIA3 in XLID patients has been suggested also for Xq25 copy number variants"
    explanation: >-
      Records that structural Xq25 lesions, not only single-nucleotide variants, constitute the
      initiating GRIA3 alteration in X-linked intellectual disability.

- name: GluA3 Loss of Function
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Loss-of-function alleles reduce or abolish GluA3 activity by disrupting transcription or
    splicing, truncating the protein, deleting exons, or — for the p.Ala653Thr gate variant —
    stabilising the assembled channel in a closed, non-conducting conformation. In the
    functionally screened variant set, loss and gain of function together accounted for 31 of
    44 tested alleles, so neither direction can be assumed from variant rarity alone.
  molecular_functions:
  - preferred_term: GluA3-containing AMPA receptor channel activity
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0004971
      label: AMPA glutamate receptor activity
  genetic_context:
    gene:
      preferred_term: GRIA3
      term:
        id: hgnc:4573
        label: GRIA3
    allele_type: missense, canonical splice-site, frameshift, and multi-exon deletion alleles
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
    description: >-
      Typically hemizygous in affected males and inherited from a clinically healthy carrier
      mother, though de novo loss-of-function alleles also occur and heterozygous females can
      be affected, so zygosity is left unset rather than asserting the modal case. Mechanisms
      with direct functional support are exon-2 skipping from c.268+1G>C, the p.Glu787Gly
      allele that produced no measurable current, and the p.Ala653Thr closed-channel allele.
      A multi-exon deletion is also reported but only in a source with no PubMed record, so it
      is described here rather than cited. p.Gly630Arg is a segregating familial allele with no
      electrophysiology and is deliberately not assigned a functional direction.
  downstream:
  - target: Reduced AMPA Receptor-Mediated Excitatory Current
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:29016847
      reference_title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "In vitro, the GRIA3(A653T) mutation stabilizes the channel in a closed conformation, in contrast to Lurcher."
      explanation: >-
        A closed-channel conformation is the direct biophysical route from a loss-of-function
        allele to reduced AMPA receptor current.
    - reference: PMID:34731330
      reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "When glutamate (10 mM) was applied to HEK cells transfected with GluA3o and GluA3o_E787G, we observed the latter to produce no currents"
      explanation: >-
        A second loss-of-function allele measured directly: the mutant receptor carries no
        current at all, which is the edge stated as a measurement rather than an inference.
  evidence:
  - reference: PMID:35031858
    reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hemizygous loss-of-function (LOF) variants in GRIA3 cause a neurodevelopmental disorder (NDD) in male individuals."
    explanation: >-
      States that hemizygous GRIA3 loss of function is an established cause of the
      neurodevelopmental phenotype in males.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Thirty-one variants alter receptor function and show loss-of-function or gain-of-function properties, whereas 13 appeared neutral."
    explanation: >-
      Systematic electrophysiological screening establishes loss of function as one of two
      distinct functional classes among pathogenic GRIA3 alleles, alongside a substantial
      functionally neutral fraction.
  - reference: PMID:29016847
    reference_title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The mutation (A653T) falls within the highly conserved transmembrane domain of the ion channel gate"
    explanation: >-
      Locates the archetypal closed-channel loss-of-function allele in the ion-conduction gate,
      explaining why it removes current without removing the protein.

- name: GluA3 Gain of Function
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Gain-of-function alleles prolong receptor activation by slowing desensitisation and
    deactivation, so each glutamate release event drives a longer-lasting depolarising
    current. This is a qualitative change in gating kinetics rather than simply more receptor
    activity, and it produces a clinical picture opposite to loss of function in muscle tone
    and seizure onset age.
  molecular_functions:
  - preferred_term: GluA3-containing AMPA receptor channel activity
    modifier: GAIN_OF_FUNCTION
    term:
      id: GO:0004971
      label: AMPA glutamate receptor activity
  genetic_context:
    gene:
      preferred_term: GRIA3
      term:
        id: hgnc:4573
        label: GRIA3
    allele_type: missense alleles clustering in and around the channel gate and M3-S2 linker
    variant_origin: DE_NOVO
    functional_impact_category: GAIN_OF_FUNCTION
    description: >-
      Zygosity is deliberately left unset because the single-valued slot cannot represent this
      branch: affected females are heterozygous and affected males hemizygous, and both occur.
      p.Ala615Val is the only allele here whose gain of function was measured, by patch clamp,
      in a hemizygous de novo male. The female alleles usually cited alongside it —
      p.Met661Thr and p.Thr657Ala — were never tested electrophysiologically; their assignment
      to this branch is inferred from residue position and from the hypertonic phenotype, and
      both source papers say so explicitly.
  downstream:
  - target: Prolonged AMPA Receptor-Mediated Excitatory Current
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:35031858
      reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Patch-clamp recordings showed that the human GluA3 mutant (p.Ala615Val) had slower desensitization and deactivation kinetics."
      explanation: >-
        Slowed desensitisation and deactivation are precisely the kinetic changes that prolong
        the receptor-mediated current, so this measurement is the edge itself.
  evidence:
  - reference: PMID:35031858
    reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "His neurological signs, such as hypertonia and hyperreflexia, were opposite to those in previous cases having LOF GRIA3 variants."
    explanation: >-
      Establishes gain of function as a mechanistically distinct class whose clinical signs run
      opposite to loss of function, which is the reason this pathograph branches.
  - reference: PMID:35031858
    reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "A fly line expressing a human GluA3 mutant possessing our variant and the Lurcher variant, which makes ion channels leaky, showed developmental defects, while one expressing a mutant possessing either of them did not."
    explanation: >-
      Transgenic Drosophila expressing the human mutant subunit shows a genetic interaction with
      a leaky-channel allele, independent in vivo support for a gain-of-function effect.
  - reference: PMID:37921875
    reference_title: "Clinical and functional consequences of GRIA variants in patients with neurological diseases."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These variants produce changes in agonist EC50, response time course, desensitization, and/or receptor surface expression."
    explanation: >-
      Broader GRIA functional survey confirms that altered desensitisation and response time
      course are the recurring biophysical consequences of pathogenic AMPA receptor variants.

- name: Reduced AMPA Receptor-Mediated Excitatory Current
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Loss of GluA3 conductance reduces the fast excitatory postsynaptic current carried by
    GluA2/3 heterotetramers, one of the two major hippocampal AMPA receptor populations.
    Clinically this branch is enriched for low muscle tone, later seizure onset, and severely
    disorganised sleep-wake architecture.
  biological_processes:
  - preferred_term: AMPA receptor-mediated excitatory postsynaptic current
    modifier: DECREASED
    term:
      id: GO:0060079
      label: excitatory postsynaptic potential
  - preferred_term: ionotropic glutamate receptor signaling pathway
    modifier: DECREASED
    term:
      id: GO:0035235
      label: ionotropic glutamate receptor signaling pathway
  cell_types:
  - preferred_term: glutamatergic neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  cellular_components:
  - preferred_term: GluA2/3 AMPA receptor complex
    term:
      id: GO:0032281
      label: AMPA glutamate receptor complex
  - preferred_term: postsynaptic membrane
    term:
      id: GO:0045211
      label: postsynaptic membrane
  downstream:
  - target: Disturbed Excitatory Synaptic Transmission and Plasticity
    causal_link_type: DIRECT
  - target: Hypotonia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Low muscle tone is the tone phenotype specifically enriched in the loss-of-function
      branch of the cohort.
    evidence:
    - reference: PMID:38038360
      reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Patients with loss-of-function variants were older at the time of seizure onset (median age: 16 months), hypotonic and had sleeping disturbances."
      explanation: >-
        Directly associates the loss-of-function functional class with hypotonia rather than
        hypertonia, which is what this branch-specific edge asserts.
  - target: Hyporeflexia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Depressed deep tendon reflexes are the reflex counterpart of the low tone on this branch,
      mirroring the hyperreflexia seen with prolonged current.
    evidence:
    - reference: PMID:41462794
      reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The neurological phenotype is generally severe, with a combination of hypotonia, hypertonia, movement disorders, and hyporeflexia"
      explanation: >-
        Lists hyporeflexia alongside hypotonia as part of the neurological phenotype of the
        disorder.
  - target: Sleep disturbance
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Sleep-wake disorganisation segregates with loss of function in the cohort and is
      reproduced allele-specifically in a knock-in mouse.
    evidence:
    - reference: PMID:29016847
      reference_title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "we sequenced a family in which the two male children had severe developmental delay and a dramatically disturbed sleep-wake cycle, with very long wake and sleep durations, reaching up to 106-h awake and 48-h asleep."
      explanation: >-
        The closed-channel loss-of-function allele co-segregates with extreme sleep-wake
        disruption in an affected sibship, linking reduced current to the sleep phenotype.
  evidence:
  - reference: PMID:36429079
    reference_title: "Expression and Interaction Proteomics of GluA1- and GluA3-Subunit-Containing AMPARs Reveal Distinct Protein Composition."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The most abundant AMPAR subtypes in the hippocampus are GluA1/2 and GluA2/3 heterotetramers."
    explanation: >-
      Establishes that GluA3-containing receptors carry a major share of hippocampal AMPA
      current, so losing GluA3 function measurably reduces that current.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs) mediate fast excitatory neurotransmission in the brain."
    explanation: >-
      Identifies fast excitatory neurotransmission as the function that a loss of AMPA receptor
      conductance reduces.

- name: Prolonged AMPA Receptor-Mediated Excitatory Current
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Slowed desensitisation and deactivation extend the depolarising current carried by
    mutant GluA3-containing receptors after each glutamate transient, so charge transfer per
    synaptic event increases. Clinically this branch is enriched for high muscle tone,
    hyperreflexia, hyperekplexia and very early seizure onset.
  biological_processes:
  - preferred_term: AMPA receptor-mediated excitatory postsynaptic current
    modifier: INCREASED
    term:
      id: GO:0060079
      label: excitatory postsynaptic potential
  - preferred_term: excitatory chemical synaptic transmission
    modifier: INCREASED
    term:
      id: GO:0098976
      label: excitatory chemical synaptic transmission
  cell_types:
  - preferred_term: glutamatergic neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  cellular_components:
  - preferred_term: GluA3-containing AMPA receptor complex
    term:
      id: GO:0032281
      label: AMPA glutamate receptor complex
  downstream:
  - target: Disturbed Excitatory Synaptic Transmission and Plasticity
    causal_link_type: DIRECT
  - target: Hypertonia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Increased tone is the tone phenotype specifically enriched in the gain-of-function branch,
      and in the functionally confirmed p.Ala615Val case it responded to a drug that suppresses
      glutamate release.
    evidence:
    - reference: PMID:38038360
      reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Gain-of-function variants were associated with more severe outcomes: patients were younger at the time of seizure onset (median age: 1 month), hypertonic and more often had movement disorders, including hyperekplexia."
      explanation: >-
        Directly associates the gain-of-function functional class with hypertonia and earlier
        seizure onset, which is what this branch-specific edge asserts.
  - target: Abnormality of movement
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Movement disorders as a class are more common on this branch, with hyperekplexia and
      non-epileptic erratic myoclonus as the dominant expression.
    evidence:
    - reference: PMID:38038360
      reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Gain-of-function variants were associated with more severe outcomes: patients were younger at the time of seizure onset (median age: 1 month), hypertonic and more often had movement disorders, including hyperekplexia."
      explanation: >-
        Assigns movement disorders as a class, not only hyperekplexia, to the gain-of-function
        branch.
  - target: Exaggerated startle response
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Hyperekplexia and non-epileptic erratic myoclonus are the most prevalent movement features
      and cluster with gain of function.
    evidence:
    - reference: PMID:41462794
      reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Gain-of-function (GoF) variants in GRIA3 are associated with severe phenotypes, including early-onset seizures, hypertonia, and hyperekplexia, while affected females most often carry de novo heterozygous GoF variants."
      explanation: >-
        Independently associates gain of function with hyperekplexia alongside hypertonia and
        early seizures.
  evidence:
  - reference: PMID:35031858
    reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Patch-clamp recordings showed that the human GluA3 mutant (p.Ala615Val) had slower desensitization and deactivation kinetics."
    explanation: >-
      The measured kinetic slowing is the biophysical definition of the prolonged current this
      node describes.
  - reference: PMID:37921875
    reference_title: "Clinical and functional consequences of GRIA variants in patients with neurological diseases."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: "We predict that these functional and localization changes will have important consequences for circuit function, and therefore likely contribute to the patients' clinical phenotype."
    explanation: >-
      Connects the measured AMPA receptor gating changes to expected circuit-level consequences.
      Marked INDIRECT because the quoted sentence is the authors' stated prediction from the
      measured biophysics, not an observation of the circuit consequence itself.

- name: Disturbed Excitatory Synaptic Transmission and Plasticity
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Both branches converge here. Whether GluA3-mediated current is reduced or prolonged, the
    postsynaptic response to glutamate is mistimed relative to the activity-dependent rules
    that govern synaptic strengthening, so experience-dependent plasticity is degraded and the
    circuits that support learning and memory develop abnormally. The cognitive outcome itself
    is carried by the downstream HP phenotypes rather than by a GO behaviour term on this
    node. GluA2/3 receptors cycle constitutively under basal
    conditions and their auxiliary partners set trafficking and gating, so the lesion is felt
    at the level of synaptic maintenance as well as of acute transmission.
  biological_processes:
  - preferred_term: chemical synaptic transmission
    modifier: ABNORMAL
    term:
      id: GO:0007268
      label: chemical synaptic transmission
  - preferred_term: regulation of synaptic plasticity
    modifier: DYSREGULATED
    term:
      id: GO:0048167
      label: regulation of synaptic plasticity
  cell_types:
  - preferred_term: glutamatergic neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  cellular_components:
  - preferred_term: postsynaptic density
    term:
      id: GO:0014069
      label: postsynaptic density
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  - preferred_term: hippocampal formation
    term:
      id: UBERON:0002421
      label: hippocampal formation
  - preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  downstream:
  - target: Cortical Network Hyperexcitability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Intellectual disability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The developmental impairment resolves into fixed intellectual disability in older
      children and adults, which is the term the adult pedigrees are described with.
  - target: Psychosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Psychiatric manifestations emerge in adulthood in some pedigrees. The step from
      disturbed excitatory transmission to psychosis is not measured in any patient and is
      asserted here only as the shared upstream lesion.
  - target: Aggressive behavior
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Aggression is reported in affected adult males and is one of the few human features the
      Gria3 null mouse reproduces, which is why it is hung on the shared synaptic node rather
      than on either allele branch.
  - target: Autistic behavior
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Autistic features recur across the older familial descriptions without segregating by
      allele class.
  - target: Global developmental delay
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Global developmental impairment is the one feature present in every functionally
      characterised patient, on both branches, which is what makes it the convergent output of
      this shared node rather than of either allele class.
    evidence:
    - reference: PMID:38038360
      reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25)."
      explanation: >-
        Universal developmental impairment across both functional classes is what identifies it
        as the shared downstream consequence of disturbed synaptic transmission.
  evidence:
  - reference: PMID:36429079
    reference_title: "Expression and Interaction Proteomics of GluA1- and GluA3-Subunit-Containing AMPARs Reveal Distinct Protein Composition."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Several interactors were shown to affect biogenesis, AMPAR trafficking, and channel properties, alone or in distinct assemblies, and several revealed preferred binding to specific AMPAR subunits."
    explanation: >-
      Establishes that GluA3-containing receptor complexes have subunit-specific trafficking and
      gating regulation, so altering GluA3 perturbs synaptic receptor handling and not only
      instantaneous conductance.
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AMPARs are heterotetrameric receptors combining four different subunits, defined GluA1-4 and encoded by GRIA1-4 genes, respectively."
    explanation: >-
      Establishes that GluA3 is one subunit of an obligate heterotetramer, so a variant subunit
      is incorporated into and perturbs otherwise normal synaptic receptors.

- name: Cortical Network Hyperexcitability
  biological_scale: TISSUE
  mechanism_confidence: PROVISIONAL
  description: >-
    Mistimed excitatory drive in developing cortical and thalamocortical circuits lowers the
    threshold for synchronous discharge. EEG in affected individuals shows focal spikes that
    generalise readily, and in one female with a de novo allele the network state escalated to
    non-convulsive status epilepticus. The step from synaptic dysfunction to network
    hyperexcitability is inferred from clinical electrophysiology rather than measured
    directly in patient cortex, so it is recorded as provisional.
  biological_processes:
  - preferred_term: regulation of neuronal membrane potential
    modifier: DYSREGULATED
    term:
      id: GO:0042391
      label: regulation of membrane potential
  locations:
  - preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  downstream:
  - target: Seizure
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:36726007
      reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "An electroencephalogram (EEG) showed frequent spikes in the central area, which readily developed into generalized spikes and waves"
      explanation: >-
        Cortical spikes that generalise readily are the electrographic expression of network
        hyperexcitability producing clinical seizures in a GRIA3 patient.
  evidence:
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "AMPARs, including complexes with GluA3, are broadly distributed in the brain, particularly in the hippocampus, cerebral cortex, and thalamus, regions associated with epileptic activity"
    explanation: >-
      Places GluA3-containing receptors in exactly the cortical and thalamic circuits that
      generate epileptic activity, which is the anatomical basis for this node.
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The EEG revealed high-amplitude diffuse rhythmic theta/delta activity consistent with NCSE."
    explanation: >-
      Diffuse rhythmic electrographic activity documents sustained network-level hyperexcitability
      in a GRIA3 patient.

phenotypes:
- name: Global developmental delay
  category: Neurologic
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  frequency: VERY_FREQUENT
  description: >-
    Present in every functionally characterised patient reported so far and the one feature
    that does not distinguish the loss-of-function from the gain-of-function branch. Graded
    VERY_FREQUENT rather than OBLIGATE because the cohort was selected for having both a
    functionally characterised variant and detailed clinical data, so 25/25 is not a
    penetrance estimate. Severity
    is graded moderate in 9 of 25 and severe in 12 of 25, so the modal patient is severely
    impaired.
  sequelae:
  - target: Delayed speech and language development
  - target: Severe global developmental delay
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25)."
    explanation: >-
      Reports universal global developmental impairment with its severity distribution in the
      reference cohort.

- name: Intellectual disability
  category: Neurologic
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  frequency: VERY_FREQUENT
  description: >-
    The developmental delay of infancy resolves into fixed intellectual disability, graded
    moderate to severe. This is the term the adult pedigrees are described with, where
    `Global developmental delay` no longer applies: the Finnish family D174 males were 35 to
    57 years old at report, and the Italian and Chinese pedigrees describe severe intellectual
    disability rather than delay.
  evidence:
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over the following years, she developed a paraparetic spastic gait with hyperreflexia, expressive language impairment, and moderate intellectual disability (ID)."
    explanation: >-
      Records intellectual disability at the mild end of the reported range, formally assessed.
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The index subject was referred for severe ID, myoclonic seizures, cerebellar signs and short stature."
    explanation: >-
      Records intellectual disability at the severe end of the range in an independent pedigree.

- name: Hyporeflexia
  category: Neurologic
  phenotype_term:
    preferred_term: Hyporeflexia
    term:
      id: HP:0001265
      label: Hyporeflexia
  frequency: OCCASIONAL
  description: >-
    Depressed deep tendon reflexes are the reflex counterpart of the hypotonic,
    loss-of-function branch and the mirror image of the hyperreflexia seen with prolonged
    receptor current. Both appear in the disorder for the same reason both tone phenotypes do:
    the reported patients span two opposite functional classes.
  evidence:
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The neurological phenotype is generally severe, with a combination of hypotonia, hypertonia, movement disorders, and hyporeflexia"
    explanation: >-
      Lists hyporeflexia as part of the neurological phenotype alongside the two opposite tone
      states.

- name: Severe global developmental delay
  category: Neurologic
  phenotype_term:
    preferred_term: Severe global developmental delay
    term:
      id: HP:0011344
      label: Severe global developmental delay
  frequency: FREQUENT
  description: >-
    Roughly half of reported patients (12/25) sit at the severe end of the developmental
    spectrum, with limited or absent speech and, in the most affected, loss of independent
    mobility.
  sequelae:
  - target: Scoliosis
  - target: Hip dislocation
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25)."
    explanation: >-
      Gives the 12/25 severe fraction that this phenotype records.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She now presents with severe developmental delay, scoliosis and hip dislocation."
    explanation: >-
      Illustrative severe case, and the source for the orthopaedic sequelae recorded below.

- name: Delayed speech and language development
  category: Neurologic
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  frequency: FREQUENT
  description: >-
    Expressive language is disproportionately affected. Reports range from poor speech by one
    year of age in the most severe cases to isolated expressive language impairment with
    preserved socialisation in the mildest.
  evidence:
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over the following years, she developed a paraparetic spastic gait with hyperreflexia, expressive language impairment, and moderate intellectual disability (ID)."
    explanation: >-
      Documents expressive language impairment as part of the phenotype in a mildly affected
      female.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, she was bedridden and had poor speaking ability at one year of age."
    explanation: >-
      Documents severely impaired speech acquisition at the severe end of the spectrum.

- name: Seizure
  category: Neurologic
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  frequency: FREQUENT
  description: >-
    Reported in 12 of 25 patients. Age at onset is the sharpest genotype-phenotype signal in
    the disorder: median one month for gain-of-function alleles versus 16 months for
    loss-of-function alleles. The epilepsy syndrome was classified as developmental and
    epileptic encephalopathy in eight patients and as intellectual disability with epilepsy in
    four.
  sequelae:
  - target: Focal motor seizure
  - target: Generalized myoclonic seizure
  - target: Non-convulsive status epilepticus
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The epilepsy syndrome was classified as developmental and epileptic encephalopathy in eight patients, developmental encephalopathy without seizures in 13 patients, and intellectual disability with epilepsy in four patients."
    explanation: >-
      Gives the epilepsy syndrome classification across the cohort, including the fraction with
      no seizures at all.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epilepsy onset occurred at 3 months of age with tonic and clonic seizures."
    explanation: >-
      Individual early-onset example in a de novo heterozygous female, consistent with the
      gain-of-function onset distribution.

- name: Focal motor seizure
  category: Neurologic
  phenotype_term:
    preferred_term: Focal motor seizure
    term:
      id: HP:0011153
      label: Focal motor seizure
  frequency: OCCASIONAL
  description: >-
    The commonest single seizure semiology in the reference cohort, reported in 6 of the 12
    patients with epilepsy. The frequency band is computed over all 25 patients (6/25, 24%),
    not over the epilepsy subgroup.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Twelve patients had seizures, including focal motor (6/12), unknown onset motor (4/12), focal impaired awareness (1/12), (atypical) absence (2/12), myoclonic (5/12) and generalized tonic-clonic (1/12) or atonic (1/12) seizures."
    explanation: >-
      Enumerates the seizure semiologies with focal motor seizures as the most frequent type.

- name: Generalized myoclonic seizure
  category: Neurologic
  phenotype_term:
    preferred_term: Generalized myoclonic seizure
    term:
      id: HP:0002123
      label: Generalized myoclonic seizure
  frequency: OCCASIONAL
  description: >-
    Myoclonic seizures occurred in 5 of 12 patients with epilepsy (5/25, 20% of the whole
    cohort, which is the denominator the frequency band uses) and were the cardinal
    feature, escalating to myoclonic status epilepticus, in an Italian pedigree carrying the
    p.Glu787Gly allele.
  evidence:
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "stress the relevance of myoclonic seizures and cerebellar syndrome as cardinal features of his presentation"
    explanation: >-
      Identifies myoclonic seizures as a defining feature of a GRIA3-variant proband.
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epilepsy onset occurred at 29 months with clonic seizures and myoclonic seizures with fall."
    explanation: >-
      Individual semiology and onset age for the myoclonic seizures in that proband, whose
      familial allele was inherited rather than de novo.

- name: Non-convulsive status epilepticus
  category: Neurologic
  phenotype_term:
    preferred_term: Non-convulsive status epilepticus
    term:
      id: HP:0031475
      label: Status epilepticus without prominent motor symptoms
  frequency: VERY_RARE
  description: >-
    Status epilepticus of either kind has been documented in only a handful of patients. This
    phenotype is scoped to the non-convulsive form, which was described first in a male and, in
    2025, for the first time in a female — a seven-year-old with a de novo p.Thr657Ala allele
    who resolved back to her neurological baseline after treatment. The convulsive myoclonic
    form, which escalated to myoclonic status epilepticus in the Italian pedigree, is carried by
    the separate Generalized myoclonic seizure entry.
  evidence:
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first reported case of NCSE in a female patient with a GRIA3 variant."
    explanation: >-
      Establishes the female case as newly described. Note the scope of the claim: the paper
      states two paragraphs earlier that status epilepticus was already documented in two
      patients, so this is the first female case rather than the first case.
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Status epilepticus (SE) has been documented in two cases."
    explanation: >-
      Gives the total number of reported status epilepticus cases, which is why this phenotype is
      graded VERY_RARE rather than presented as a novel single observation.

- name: Hypotonia
  category: Neurologic
  phenotype_term:
    preferred_term: Limb muscular hypotonia
    term:
      id: HP:0012389
      label: Appendicular hypotonia
  frequency: FREQUENT
  description: >-
    Reported in 13 of 25 patients and enriched in the loss-of-function branch, where it
    appears together with later seizure onset and disturbed sleep. Hypotonia and hypertonia
    are both frequent in the disorder as a whole because the cohort mixes the two functional
    classes.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Limb muscular hypotonia was reported in 13/25, and hypertonia in 10/25."
    explanation: >-
      Gives the cohort frequency of hypotonia alongside the competing tone phenotype.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with loss-of-function variants were older at the time of seizure onset (median age: 16 months), hypotonic and had sleeping disturbances."
    explanation: >-
      Assigns hypotonia specifically to the loss-of-function class.

- name: Hypertonia
  category: Neurologic
  phenotype_term:
    preferred_term: Hypertonia
    term:
      id: HP:0001276
      label: Hypertonia
  frequency: FREQUENT
  description: >-
    Reported in 10 of 25 patients and enriched in the gain-of-function branch. It can be
    congenital: in the p.Met661Thr female it was noted at delivery. In the functionally
    confirmed p.Ala615Val male it improved on carbamazepine, which makes it the tone
    phenotype with a demonstrated pharmacological handle.
  sequelae:
  - target: Hyperreflexia
  - target: Spastic gait
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Limb muscular hypotonia was reported in 13/25, and hypertonia in 10/25."
    explanation: >-
      Gives the cohort frequency of hypertonia.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She exhibited hypertonia and increased deep tendon reflexes."
    explanation: >-
      Documents hypertonia with hyperreflexia from birth in a de novo heterozygous female.

- name: Hyperreflexia
  category: Neurologic
  phenotype_term:
    preferred_term: Hyperreflexia
    term:
      id: HP:0001347
      label: Hyperreflexia
  frequency: OCCASIONAL
  description: >-
    Brisk deep tendon reflexes accompany hypertonia and, with spasticity, point to
    corticospinal involvement. The only functionally confirmed gain-of-function case in which
    hyperreflexia was recorded is a male; the females in whom it is reported carry alleles
    whose functional direction was never measured, so this is not established as a
    sex-independent gain-of-function feature.
  evidence:
  - reference: PMID:35031858
    reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "His neurological signs, such as hypertonia and hyperreflexia, were opposite to those in previous cases having LOF GRIA3 variants."
    explanation: >-
      Records hyperreflexia in the functionally confirmed gain-of-function male and contrasts it
      with the loss-of-function presentation.

- name: Spastic gait
  category: Neurologic
  phenotype_term:
    preferred_term: Spastic paraparetic gait
    term:
      id: HP:0002064
      label: Spastic gait
  frequency: OCCASIONAL
  description: >-
    Lower-limb spasticity progressing to a paraparetic spastic gait is described in a
    mildly affected female with a de novo gain-of-function-associated allele.
  evidence:
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over the following years, she developed a paraparetic spastic gait with hyperreflexia, expressive language impairment, and moderate intellectual disability (ID)."
    explanation: >-
      Documents the spastic gait phenotype and its co-occurrence with hyperreflexia.

- name: Abnormality of movement
  category: Neurologic
  phenotype_term:
    preferred_term: Movement disorder
    term:
      id: HP:0100022
      label: Abnormality of movement
  frequency: FREQUENT
  description: >-
    Movement disorders were reported in 14 of 25 patients, the second most frequent domain
    after developmental impairment, and were more common in the gain-of-function branch.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Movement disorders were reported in 14/25, with hyperekplexia or non-epileptic erratic myoclonus being the most prevalent feature (8/25)."
    explanation: >-
      Gives the cohort frequency of movement disorders and names their dominant expression.

- name: Exaggerated startle response
  category: Neurologic
  phenotype_term:
    preferred_term: Hyperekplexia
    term:
      id: HP:0002267
      label: Exaggerated startle response
  frequency: FREQUENT
  description: >-
    Hyperekplexia, or non-epileptic erratic myoclonus, was the single most prevalent movement
    feature (8 of 25) and clusters with gain-of-function alleles. It is important
    diagnostically because it is non-epileptic and can be mistaken for seizure activity.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Movement disorders were reported in 14/25, with hyperekplexia or non-epileptic erratic myoclonus being the most prevalent feature (8/25)."
    explanation: >-
      Establishes hyperekplexia as the most prevalent movement feature with its cohort fraction.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Gain-of-function variants were associated with more severe outcomes: patients were younger at the time of seizure onset (median age: 1 month), hypertonic and more often had movement disorders, including hyperekplexia."
    explanation: >-
      Assigns hyperekplexia specifically to the gain-of-function class.

- name: Sleep disturbance
  category: Neurologic
  phenotype_term:
    preferred_term: Sleep-wake cycle disturbance
    term:
      id: HP:0006979
      label: Sleep-wake cycle disturbance
  frequency: OCCASIONAL
  description: >-
    Disturbed sleep segregates with loss-of-function alleles. The extreme reported case is a
    sibship carrying p.Ala653Thr in whom wake periods reached 106 hours and sleep periods 48
    hours, a degree of sleep-wake disorganisation that is itself allele-specific and is
    reproduced in a knock-in mouse.
  evidence:
  - reference: PMID:29016847
    reference_title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we sequenced a family in which the two male children had severe developmental delay and a dramatically disturbed sleep-wake cycle, with very long wake and sleep durations, reaching up to 106-h awake and 48-h asleep."
    explanation: >-
      Quantifies the extreme sleep-wake disturbance in an affected sibship carrying a
      loss-of-function GRIA3 allele.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with loss-of-function variants were older at the time of seizure onset (median age: 16 months), hypotonic and had sleeping disturbances."
    explanation: >-
      Assigns sleep disturbance to the loss-of-function class at cohort level.

- name: Autistic behavior
  category: Behavioral
  phenotype_term:
    preferred_term: Autistic features
    term:
      id: HP:0000729
      label: Autistic behavior
  frequency: OCCASIONAL
  description: >-
    Autistic features are recurrent in the older familial descriptions of Wu-type X-linked
    syndromic intellectual disability, alongside self-injury and aggressive outbursts in
    adult affected males. The Finnish family D174, in which three affected males aged 35 to
    57 carry GRIA3 p.Gly630Arg, is the best-described example.
  evidence:
  - reference: PMID:24721225
    reference_title: "X-exome sequencing in Finnish families with intellectual disability--four novel mutations and two novel syndromic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "are characterized by severe ID with autistic features, epilepsy, short stature and behavioral problems such as self injury and aggressive outbursts"
    explanation: >-
      Names autistic features explicitly, in the GRIA3 pedigree where they were reported,
      together with the co-occurring behavioural problems.

- name: Self-injurious behavior
  category: Behavioral
  phenotype_term:
    preferred_term: Self injury
    term:
      id: HP:0100716
      label: Self-injurious behavior
  frequency: OCCASIONAL
  description: >-
    Self-injury is reported alongside aggressive outbursts in the affected adult males of the
    Finnish family D174, and is one of the behavioural features that make the adult
    presentation of this disorder difficult to manage.
  evidence:
  - reference: PMID:24721225
    reference_title: "X-exome sequencing in Finnish families with intellectual disability--four novel mutations and two novel syndromic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "are characterized by severe ID with autistic features, epilepsy, short stature and behavioral problems such as self injury and aggressive outbursts"
    explanation: >-
      Names self injury explicitly among the behavioural problems of the GRIA3 pedigree.

- name: Aggressive behavior
  category: Behavioral
  phenotype_term:
    preferred_term: Aggressive outbursts
    term:
      id: HP:0000718
      label: Aggressive behavior
  frequency: OCCASIONAL
  description: >-
    Violent tendencies and emotional instability are reported in affected adult males in
    GRIA3 pedigrees, and increased isolation-induced aggression was measured in Gria3-null
    mice in a single study.
  evidence:
  - reference: PMID:42666715
    reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, III-1 and II-3 exhibit violent tendencies, emotional instability, delusions, and hallucinations."
    explanation: >-
      Documents aggression together with affective and psychotic features in two affected
      relatives.

- name: Psychosis
  category: Behavioral
  phenotype_term:
    preferred_term: Delusions and hallucinations
    term:
      id: HP:0000709
      label: Psychosis
  frequency: OCCASIONAL
  description: >-
    Psychotic symptoms — delusions and hallucinations — are described in affected members of
    a GRIA3 splice-variant pedigree and responded to antipsychotic treatment. This is the
    feature that most distinguishes the adult presentation from a purely developmental
    phenotype.
  evidence:
  - reference: PMID:42666715
    reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Their behavioral manifestations may include emotional instability, delusions, hallucinations, and other psychiatric symptoms."
    explanation: >-
      Records delusions and hallucinations as part of the behavioural spectrum of GRIA3-related
      disease.

- name: Cerebellar vermis hypoplasia
  category: Neurologic
  phenotype_term:
    preferred_term: Cerebellar vermis hypoplasia
    term:
      id: HP:0001320
      label: Cerebellar vermis hypoplasia
  frequency: VERY_RARE
  description: >-
    Structural cerebellar findings are not universal but were the imaging correlate of a
    clinical cerebellar syndrome in the p.Glu787Gly proband, whose MRI also showed a focal
    cortical dysplasia.
  sequelae:
  - target: Ataxia
  evidence:
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cerebral MRI of our proband highlighted cerebellar vermis hypoplasia and a focal cortical dysplasia."
    explanation: >-
      Direct imaging report of cerebellar vermis hypoplasia in a GRIA3-variant patient.

- name: Ataxia
  category: Neurologic
  phenotype_term:
    preferred_term: Cerebellar syndrome with ataxia, tremor and dysmetria
    term:
      id: HP:0001251
      label: Ataxia
  frequency: VERY_RARE
  description: >-
    A full cerebellar syndrome — ataxia, tremor and dysmetria — was a cardinal feature in the
    Italian pedigree, matching the vermian hypoplasia seen on imaging.
  evidence:
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neurological examination was characterized by a cerebellar syndrome with ataxia, tremor and dysmetria."
    explanation: >-
      Documents the clinical cerebellar syndrome in a GRIA3-variant proband.

- name: Cerebral atrophy
  category: Neurologic
  phenotype_term:
    preferred_term: Frontal lobe atrophy
    term:
      id: HP:0002059
      label: Cerebral atrophy
  frequency: VERY_RARE
  description: >-
    Mild frontal atrophy with ventricular enlargement was seen in the p.Met661Thr female and,
    importantly, had not progressed by age 13 — the structural findings in this disorder are
    not reliably degenerative.
  evidence:
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain magnetic resonance imaging revealed mild frontal lobe atrophy and slight ventricular enlargement"
    explanation: >-
      Imaging report of frontal atrophy and ventriculomegaly in a GRIA3 patient.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Slight frontal lobe atrophy and ventricular enlargement were not aggravated."
    explanation: >-
      Records that the structural findings had not worsened by the age-13 scan, which is why this
      is not curated as a neurodegenerative phenotype. The paper reports one scan and does not
      give a baseline date, so the interval itself is not established.

- name: Ventriculomegaly
  category: Neurologic
  phenotype_term:
    preferred_term: Ventricular enlargement
    term:
      id: HP:0002119
      label: Ventriculomegaly
  frequency: VERY_RARE
  description: >-
    Slight ventricular enlargement accompanies the frontal atrophy in the reported imaging and
    is likewise non-progressive.
  evidence:
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain magnetic resonance imaging revealed mild frontal lobe atrophy and slight ventricular enlargement"
    explanation: >-
      Imaging report documenting ventricular enlargement.

- name: Scoliosis
  category: Skeletal
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  frequency: VERY_RARE
  description: >-
    Orthopaedic complications appear at the severe end of the spectrum and are best understood
    as secondary to abnormal tone and loss of ambulation rather than as a primary skeletal
    feature.
  evidence:
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She now presents with severe developmental delay, scoliosis and hip dislocation."
    explanation: >-
      Reports scoliosis in a severely affected, bedridden GRIA3 patient.

- name: Hip dislocation
  category: Skeletal
  phenotype_term:
    preferred_term: Hip dislocation
    term:
      id: HP:0002827
      label: Hip dislocation
  frequency: VERY_RARE
  description: >-
    Reported with scoliosis in the same severely affected, non-ambulatory patient; secondary
    to abnormal tone and immobility.
  evidence:
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She now presents with severe developmental delay, scoliosis and hip dislocation."
    explanation: >-
      Reports hip dislocation in a severely affected GRIA3 patient.

- name: Short stature
  category: Growth
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  frequency: VERY_RARE
  description: >-
    Short stature with relative macrocephaly and facial dysmorphism was part of the historical
    Wu-type description and recurs in the Italian p.Glu787Gly pedigree, but it is not a
    consistent feature of the disorder and is absent from several well-characterised cases.
  evidence:
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Moreover, he showed short stature, low weight, relative macrocephaly and facial dysmorphisms."
    explanation: >-
      Documents short stature with the associated growth and craniofacial features in a
      GRIA3-variant proband.

genetic:
- name: GRIA3
  gene_term:
    preferred_term: GRIA3
    term:
      id: hgnc:4573
      label: GRIA3
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  association: >-
    Sole causative gene. GRIA3 maps to Xq25 and encodes GluA3, the only X-chromosomal AMPA
    receptor subunit. Reported allele classes span missense, canonical splice-site,
    frameshift, multi-exon deletion and duplication, and translocations disrupting the locus.
  features: >-
    Functional direction, not variant class, is what predicts phenotype. Systematic
    electrophysiology of one frameshift and 43 rare missense alleles found 31 that alter
    receptor function as loss or gain of function and 13 that behave neutrally, so rarity and
    a plausible domain location do not by themselves establish pathogenicity.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here, we evaluated the impact on AMPAR function of one frameshift and 43 rare missense GRIA3 variants identified in patients with NDD by electrophysiological assays."
    explanation: >-
      Describes the systematic functional screen behind the loss-of-function versus
      gain-of-function classification used throughout this entry.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Thirty-one variants alter receptor function and show loss-of-function or gain-of-function properties, whereas 13 appeared neutral."
    explanation: >-
      Quantifies the functionally neutral fraction, which is the reason variant interpretation in
      this gene needs functional data rather than in-silico prediction alone.
  - reference: PMID:24721225
    reference_title: "X-exome sequencing in Finnish families with intellectual disability--four novel mutations and two novel syndromic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "One novel missense mutation (c.1888G > C) was found in GRIA3"
    explanation: >-
      Independent X-exome study identifying a segregating GRIA3 missense allele in a Finnish
      X-linked intellectual disability family.
  variants:
  - name: c.1844C>T p.Ala615Val
    description: >-
      De novo hemizygous missense allele in a male. The functionally best-characterised
      gain-of-function allele in the disorder: patch clamp showed slowed desensitisation and
      deactivation, a transgenic fly assay confirmed a gain-of-function genetic interaction,
      and both seizures and hypertonia responded to carbamazepine.
    evidence:
    - reference: PMID:35031858
      reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We identified a hemizygous de novo missense variant in GRIA3 in a boy with an NDD: c.1844C > T (p.Ala615Val) using whole-exome sequencing."
      explanation: >-
        Establishes the allele, its zygosity and its de novo origin in the index male.
  - name: c.1982T>C p.Met661Thr
    clinical_significance: LIKELY_PATHOGENIC
    description: >-
      De novo heterozygous missense allele in a female with developmental and epileptic
      encephalopathy, sitting in the M3-S2 linker next to the functionally confirmed
      gain-of-function residue p.Arg660. Absent from EVS, 1000 Genomes, dbSNP, gnomAD and HGVD.
      Direct electrophysiology was not performed, so its gain-of-function status is inferred
      from position and from the hypertonic phenotype rather than measured.
    evidence:
    - reference: PMID:36726007
      reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Here, we report a female patient with developmental and epileptic encephalopathy who carries the novel de novo GRIA3 variant NM_007325.5: c.1982T > C: p.Met661Thr."
      explanation: >-
        Establishes the allele, its de novo origin and the affected female carrier.
    - reference: PMID:36726007
      reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "the variant was classified as likely pathogenic (PS2, PM2, PP2, PP3)"
      explanation: >-
        Records the ACMG classification and the specific criteria applied.
  - name: p.Ala653Thr
    description: >-
      Missense allele in the transmembrane ion-channel gate that stabilises the receptor in a
      closed conformation, so it is a loss-of-function allele that acts without reducing
      protein. Segregated in a sibship with severe developmental delay and the most extreme
      sleep-wake disorganisation reported in the disorder, and was modelled by CRISPR knock-in
      in mouse.
    evidence:
    - reference: PMID:29016847
      reference_title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "In vitro, the GRIA3(A653T) mutation stabilizes the channel in a closed conformation, in contrast to Lurcher."
      explanation: >-
        Defines the biophysical consequence that makes this a loss-of-function rather than a
        leaky-channel allele.
  - name: c.1969A>G p.Thr657Ala
    description: >-
      Novel de novo missense allele in a seven-year-old female presenting with developmental
      delay, spastic gait and non-convulsive status epilepticus — the mildest reported female
      course despite a severe acute epileptic episode.
    evidence:
    - reference: PMID:41462794
      reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "we present the case of a seven-year-old female patient presenting with developmental delay, spastic gait, and non-convulsive status epilepticus (NCSE), who was found to carry a novel de novo GRIA3 missense variant (c.1969A > G; p.Thr657Ala)."
      explanation: >-
        Establishes the allele, its de novo origin and the associated clinical presentation.
  - name: c.268+1G>C
    clinical_significance: LIKELY_PATHOGENIC
    description: >-
      Canonical splice-donor variant reclassified from a variant of uncertain significance to
      likely pathogenic after co-segregation analysis and a minigene assay showing exon 2
      skipping. Segregated in an X-linked pedigree with intellectual disability, prominent
      psychiatric symptoms and spatial memory deficits.
    evidence:
    - reference: PMID:42666715
      reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "we reported a pedigree that carried a novel splicing site variant of GRIA3 (c.268 + 1G>C) by whole exome sequencing (WES) and co-segregation analysis"
      explanation: >-
        Establishes the allele and its segregation in the reported family.
    - reference: PMID:42666715
      reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "The minigene assay further confirmed that this variant lead to exon 2 skipping."
      explanation: >-
        RNA-level functional evidence that upgraded the variant classification.
  - name: c.2360A>G p.Glu787Gly
    description: >-
      Familial missense allele transmitted by a healthy carrier mother in an Italian pedigree
      whose proband had severe intellectual disability, myoclonic status epilepticus,
      cerebellar vermis hypoplasia and short stature.
    evidence:
    - reference: PMID:34731330
      reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Whole exome sequencing identified a novel variant in GRIA3, c.2360A > G, p.(Glu787Gly)."
      explanation: >-
        Establishes the allele identified in the index subject.

diagnosis:
- name: Trio Exome or Genome Sequencing
  description: >-
    First-line molecular test. There is no biochemical marker, enzyme assay or imaging finding
    that establishes this diagnosis, so it rests entirely on identifying a GRIA3 variant.
    Sequencing the proband with both parents is what establishes de novo status, which carries
    substantial ACMG weight here (PS2) and is also the finding that most often flags a
    gain-of-function allele, since affected females are typically de novo heterozygotes.
  diagnosis_term:
    preferred_term: trio whole exome sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  results: >-
    A rare GRIA3 variant absent from population databases, with parental samples establishing
    whether it arose de novo or was transmitted by a carrier mother.
  evidence:
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "performed whole-exome sequencing and variant filtering for pathogenicity in the patient and her parents"
    explanation: >-
      Describes the trio design that established de novo status in the index female.
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole-exome sequencing (WES) identified a novel de novo variant in GRIA3, c."
    explanation: >-
      Independent case in which exome sequencing was the test that made the diagnosis.

- name: Copy-Number-Sensitive Testing
  description: >-
    Not optional in this gene. GRIA3 disease is caused by multi-exon deletions and duplications
    and by translocations disrupting the locus as well as by point variants, and standard
    exome SNV and indel analysis will miss them. Chromosomal microarray or read-depth or
    MLPA-based exon-level dosage analysis therefore belongs in the workup rather than being
    reserved for when sequencing is negative — and a normal microarray does not exclude the
    diagnosis, since it is routinely normal in the point-variant cases.
  diagnosis_term:
    preferred_term: chromosomal microarray and exon-level dosage analysis
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  results: >-
    An Xq25 deletion, duplication or rearrangement involving GRIA3, or a normal result that
    does not exclude the diagnosis.
  notes: >-
    The clearest published illustration — a hemizygous exon 5-12 deletion found only after
    targeted comprehensive testing followed an unrevealing SNV and indel analysis, and later
    detected prenatally in amniotic fluid — is in a journal with no PubMed or PMC record, so it
    cannot be quoted as an evidence snippet and is described here instead. The cited evidence
    below is the weaker but citable form of the same point: microarray is performed and is
    normal in the point-variant cases.
  evidence:
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Microarray analysis did not show any pathogenic copy number variants."
    explanation: >-
      Records microarray as part of the diagnostic workup and its normal result in a patient
      whose causal variant was a point variant, which is why a normal microarray cannot exclude
      the diagnosis.

- name: RNA or Minigene Study for a Splice Variant of Uncertain Significance
  description: >-
    A canonical splice-site GRIA3 variant cannot be classified on sequence alone. Patient RNA,
    RT-PCR, or a minigene reporter demonstrates whether the allele actually alters exon
    inclusion, and that result is what moves the classification. The worked example is
    c.268+1G>C, reclassified from a variant of uncertain significance to likely pathogenic on
    the strength of demonstrated exon 2 skipping together with co-segregation.
  diagnosis_term:
    preferred_term: minigene splicing assay
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  results: >-
    Demonstrated aberrant splicing, which supplies the functional criterion needed to upgrade a
    splice variant of uncertain significance.
  evidence:
  - reference: PMID:42666715
    reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "According to ACMG guidelines, We reclassified previously variant of unknown significance (VUS) into \"likely pathogenic\" through co-segregates analysis and minigene assay."
    explanation: >-
      States the classification change and names the two lines of evidence that produced it, one
      of which is the splicing assay this diagnostic step performs.

- name: Functional Electrophysiology for a Missense Variant of Uncertain Significance
  description: >-
    The step that connects diagnosis to treatment in this disorder. A rare GRIA3 missense
    variant may be loss of function, gain of function, or functionally neutral, and nothing
    about its rarity or its domain location distinguishes those. Patch-clamp characterisation
    in a heterologous system is what assigns the direction, and the direction is what the
    entry's mechanism-matched treatment argument depends on. This is currently a research or
    advanced-diagnostics assay rather than a routinely available clinical test, which is a real
    limit on that argument.
  diagnosis_term:
    preferred_term: patch-clamp functional characterisation of a GRIA3 missense allele
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  results: >-
    Assignment of the allele to the loss-of-function, gain-of-function, or functionally neutral
    class.
  evidence:
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Thirty-one variants alter receptor function and show loss-of-function or gain-of-function properties, whereas 13 appeared neutral."
    explanation: >-
      Nearly a third of tested rare missense alleles were functionally neutral, which is the
      reason this step is needed rather than optional: sequence-level interpretation alone
      cannot separate the three classes.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here, we evaluated the impact on AMPAR function of one frameshift and 43 rare missense GRIA3 variants identified in patients with NDD by electrophysiological assays."
    explanation: >-
      Describes the assay applied at scale to patient-identified variants, establishing it as a
      practicable route to a functional classification.

treatments:
- name: Carbamazepine for Gain-of-Function Disease
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    The one genotype-guided treatment observation in the disorder. In a male with the
    functionally confirmed gain-of-function allele p.Ala615Val, carbamazepine — which reduces
    presynaptic glutamate release rather than acting on the receptor itself — improved both
    seizures and hypertonia. This is an N-of-1 result and is explicitly not generalisable
    across the disorder: in a female whose allele was never functionally tested, carbamazepine
    was ineffective. Because the rationale is to reduce glutamatergic drive onto an
    over-active receptor, the same drug would not be expected to help, and could plausibly
    harm, a patient whose receptors are already under-conducting.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: carbamazepine
      term:
        id: CHEBI:3387
        label: carbamazepine
  target_mechanisms:
  - target: Prolonged AMPA Receptor-Mediated Excitatory Current
    treatment_effect: INHIBITS
    description: >-
      Reducing presynaptic glutamate release lowers the agonist transient reaching the
      slow-deactivating mutant receptor, shortening the excess charge transfer per synaptic
      event without acting on the channel itself.
    evidence:
    - reference: PMID:35031858
      reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "His seizures and hypertonia were ameliorated by carbamazepine, inhibiting glutamate release from presynapses."
      explanation: >-
        States both the clinical response and the presynaptic mechanism by which the drug is
        proposed to act on this node.
  evidence:
  - reference: PMID:35031858
    reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "GRIA3 GOF variants may cause an NDD phenotype distinctive from that of LOF variants, and drugs suppressing glutamatergic neurotransmission may ameliorate this phenotype."
    explanation: >-
      The authors' own generalisation: suppressing glutamatergic transmission is the
      mechanistic rationale, and it is explicitly tied to the gain-of-function class.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Treatment with carbamazepine and ethosuximide was ineffective."
    explanation: >-
      Contradicts any claim that carbamazepine works across GRIA3 disease. This patient's
      p.Met661Thr allele was never functionally tested, so the failure is consistent with the
      mechanism-matched reading of the drug rather than with a general benefit.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In our case, carbamazepine was ineffective, possibly because it does not act directly on AMPAR but inhibits glutamate release from presynaptic neurons"
    explanation: >-
      Independently confirms the indirect, presynaptic mechanism of action recorded on the
      mechanism link, while noting it as the reason the drug can fail.
  notes: >-
    Not a disease-modifying therapy and not tested in any trial. Treat as a hypothesis to be
    checked against the individual variant's measured functional direction, not as a
    recommendation.

- name: Multi-Agent Antiseizure Pharmacotherapy
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    Seizures are frequently drug-resistant at onset but control often improves over time with
    sequential or combined conventional antiseizure medication. In the p.Met661Thr female,
    seizures initially resistant to carbamazepine and ethosuximide were gradually brought
    under control with lamotrigine, clobazam, levetiracetam and lacosamide. In the p.Thr657Ala
    female, non-convulsive status epilepticus resolved to baseline with levetiracetam and
    midazolam. There is no evidence that any of these agents is preferred on mechanistic
    grounds; selection follows general epilepsy practice by seizure type and EEG.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: lamotrigine
      term:
        id: CHEBI:6367
        label: lamotrigine
    - preferred_term: clobazam
      term:
        id: CHEBI:31413
        label: clobazam
    - preferred_term: levetiracetam
      term:
        id: CHEBI:6437
        label: levetiracetam
    - preferred_term: lacosamide
      term:
        id: CHEBI:135939
        label: lacosamide
    - preferred_term: midazolam
      term:
        id: CHEBI:6931
        label: midazolam
  target_phenotypes:
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  - preferred_term: Non-convulsive status epilepticus
    term:
      id: HP:0002133
      label: Status epilepticus
  evidence:
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The seizures, initially resistant to drug treatment, were gradually brought under control using lamotrigine, clobazam, levetiracetam, and lacosamide."
    explanation: >-
      Names the four agents that achieved control after initial drug resistance in a GRIA3
      patient.
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Following intensive treatment with levetiracetam and midazolam, the patient gradually recovered to her baseline neurological status."
    explanation: >-
      Documents resolution of non-convulsive status epilepticus with conventional agents.

- name: Antipsychotic Pharmacotherapy for Psychiatric Manifestations
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    Adult affected males in GRIA3 pedigrees can present with delusions, hallucinations,
    emotional instability and violent behaviour that dominate the clinical picture.
    Risperidone and clozapine were reported to be effective, and lorazepam improved sleep, in
    an X-linked splice-variant family. These are uncontrolled observations from a single
    pedigree.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: risperidone
      term:
        id: CHEBI:8871
        label: risperidone
    - preferred_term: clozapine
      term:
        id: CHEBI:3766
        label: clozapine
  target_phenotypes:
  - preferred_term: Delusions and hallucinations
    term:
      id: HP:0000709
      label: Psychosis
  - preferred_term: Aggressive outbursts
    term:
      id: HP:0000718
      label: Aggressive behavior
  evidence:
  - reference: PMID:42666715
    reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Risperidone and clozapine demonstrated good efficacy, while lorazepam effectively improved sleep disturbances."
    explanation: >-
      Reports the observed response of psychiatric and sleep symptoms to these agents in the
      affected family.

- name: Lorazepam for Sleep Disturbance
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    Sleep disruption is one of the most burdensome features on the loss-of-function side, both
    for the patient and for caregivers, and no disease-specific sleep intervention has been
    studied. Lorazepam was reported to improve sleep in the affected members of an X-linked
    GRIA3 pedigree. This is an uncontrolled observation in one family, reported alongside the
    antipsychotic response rather than as a separate trial.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: lorazepam
      term:
        id: CHEBI:6539
        label: Lorazepam
  target_phenotypes:
  - preferred_term: Sleep-wake cycle disturbance
    term:
      id: HP:0006979
      label: Sleep-wake cycle disturbance
  evidence:
  - reference: PMID:42666715
    reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Risperidone and clozapine demonstrated good efficacy, while lorazepam effectively improved sleep disturbances."
    explanation: >-
      Reports the sleep response to lorazepam in the same sentence that reports the antipsychotic
      response, in the same pedigree.

- name: Genetic Counseling and Prenatal Diagnosis
  action_category: COUNSELING_INFORMATIONAL
  description: >-
    Once a familial GRIA3 allele is identified, cascade testing of at-risk maternal relatives,
    carrier testing, and prenatal or preimplantation genetic testing become available. A
    carrier mother has a 50 percent chance of transmitting the allele in each pregnancy, with
    the expected consequence depending on fetal sex, the variant's functional direction and,
    in females, X-chromosome inactivation. A de novo result lowers but does not eliminate
    recurrence risk, because parental germline mosaicism cannot be excluded.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:42666715
    reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "our results further support that this variant is likely pathogenic and may be the cause of their phenotype, which also provide evidence for its prenatal diagnosis and genetic counseling"
    explanation: >-
      States that establishing the variant's pathogenicity is what enables prenatal diagnosis and
      counselling in the family.

- name: Supportive and Rehabilitative Care
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  description: >-
    Management is multidisciplinary and phenotype-directed: early intervention, individualised
    education, speech and augmentative communication therapy, occupational and physical
    therapy, tone management, orthopaedic surveillance for scoliosis and hip dislocation,
    behavioural support and sleep intervention. No disease-modifying or gene-directed therapy
    exists. This entry records the standard-of-care package rather than a GRIA3-specific
    intervention, and no GRIA3-specific trial of any of these components has been published.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  - preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  notes: >-
    Deliberately left without an evidence item. The supporting sources describe supportive care
    only as general recommendation prose, with no quotable finding specific to this disorder,
    and manufacturing a snippet for it would misrepresent the evidence base.

animal_models:
- name: Gria3 knockout mouse
  species: Mus musculus
  genotype: Gria3-/Y germline knockout on C57BL/6J background
  background: C57BL/6J
  publication: PMID:22285418
  category: Genetically engineered
  description: >-
    Constitutive germline null allele in hemizygous males. Reproduces behavioural and
    monoaminergic consequences of losing GluA3 but not the defining human cognitive phenotype.
  genes:
  - preferred_term: Gria3
    term:
      id: hgnc:4573
      label: GRIA3
  modeled_mechanisms:
  - target: GluA3 Loss of Function
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      A null allele is the cleanest available model of complete GluA3 loss of function and
      isolates the consequences of absent GluA3 from any residual mutant-subunit effect.
    limitations: >-
      A complete null is not what most patients carry: human loss-of-function alleles are
      usually missense or splice changes that still produce a subunit which is incorporated
      into heterotetramers, so a knockout cannot report dominant-negative or assembly effects.
      The null is also constitutive and whole-body rather than neuron- or stage-restricted.
    readouts:
    - name: Isolation-induced male aggression
      target: GluA3 Loss of Function
      direction: INCREASED
      interpretation: >-
        Behavioural consequence of absent GluA3, matching the aggressive outbursts described in
        affected adult males.
      evidence:
      - reference: PMID:22285418
        reference_title: "GluA3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Compared to wild type (WT) littermates (n=14), Gria3-/Y mice (n=13) showed an increase in isolation-induced male aggression (p=0.011) in home cage resident-intruder test"
        explanation: >-
          Reports the measured increase in aggression with its comparator and significance.
    - name: Striatal dopamine concentration
      target: GluA3 Loss of Function
      direction: INCREASED
      interpretation: >-
        Neurochemical correlate of GluA3 loss, indicating that the lesion propagates into
        monoaminergic circuitry rather than staying confined to glutamatergic synapses.
      evidence:
      - reference: PMID:22285418
        reference_title: "GluA3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Increased dopamine concentrations in stratum (p=0.034) and reduced serotonin turnover in olfactory bulb (p=0.002) were documented in Gria3-/Y mice."
        explanation: >-
          Reports the measured striatal dopamine increase and the olfactory-bulb serotonin change.
    evidence:
    - reference: PMID:22285418
      reference_title: "GluA3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These results support a role of GluA3 in the modulation of social behavior through brain dopamine and/or serotonin signaling and different AMPA receptor subunits affect social behavior through distinct mechanisms."
      explanation: >-
        The authors' own conclusion that the knockout is informative for GluA3-dependent
        behavioural regulation.
  - target: Disturbed Excitatory Synaptic Transmission and Plasticity
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      The knockout does not reproduce the cognitive impairment that defines the human disorder.
      Spatial memory was intact on both the Morris water maze and the Y-maze, so the model
      cannot be used to read out the learning-and-memory limb of this node.
    limitations: >-
      Rodent spatial navigation tasks are a narrow and species-specific proxy for human global
      developmental impairment, so an intact result does not prove the node is unaffected — only
      that this model does not report it. Compensation by GluA1- and GluA2-containing receptors
      during development is a plausible explanation that the study does not exclude.
    readouts:
    - name: Spatial memory in Morris water maze and Y-maze
      target: Disturbed Excitatory Synaptic Transmission and Plasticity
      direction: UNCHANGED
      interpretation: >-
        A genuine negative result: the cognitive readout most analogous to the human phenotype is
        unaffected in the null mouse.
      evidence:
      - reference: PMID:22285418
        reference_title: "GluA3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Gria3-/Y mice showed no significant deficit in spatial memory function in Morris-water maze and Y-maze tests, and normal levels of testosterone."
        explanation: >-
          Reports the negative spatial memory result that grounds the failure to recapitulate.
    evidence:
    - reference: PMID:22285418
      reference_title: "GluA3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Gria3-/Y mice showed no significant deficit in spatial memory function in Morris-water maze and Y-maze tests, and normal levels of testosterone."
      explanation: >-
        Substantiates the negative claim that this model does not reproduce the cognitive
        consequence of disturbed excitatory transmission.

- name: Gria3 A653T knock-in mouse
  species: Mus musculus
  genotype: Gria3 A653T hemizygous CRISPR-Cas9 knock-in
  publication: PMID:29016847
  category: Genetically engineered
  description: >-
    Allele-specific knock-in of the orthologue of the human closed-channel loss-of-function
    variant, generated to test whether that allele explains the extreme sleep-wake phenotype in
    the index sibship. It is the strongest allele-level human-to-mouse concordance in the
    disorder.
  genes:
  - preferred_term: Gria3
    term:
      id: hgnc:4573
      label: GRIA3
  modeled_mechanisms:
  - target: Reduced AMPA Receptor-Mediated Excitatory Current
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Carries the exact human loss-of-function allele and reproduces the sleep-architecture and
      light-sensitivity consequences attributed to reduced GluA3 current in the patients.
    limitations: >-
      Reproduces the sleep and circadian limb of the phenotype but not the developmental delay,
      epilepsy or tone abnormalities, so it models one downstream consequence of the reduced
      current rather than the disorder. Mouse sleep is polyphasic and its architecture is not
      directly comparable to the multi-day human wake and sleep periods that motivated the model.
    readouts:
    - name: Number of brief activity and sleep bouts
      target: Reduced AMPA Receptor-Mediated Excitatory Current
      direction: DECREASED
      interpretation: >-
        Loss of the normal polyphasic sleep structure, the murine counterpart of the very long
        consolidated wake and sleep periods seen in the patients.
      evidence:
      - reference: PMID:29016847
        reference_title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The Gria3A653T mouse showed significantly fewer brief bouts of activity and sleep than the wild-types."
        explanation: >-
          Reports the measured change in sleep and activity bout structure.
    - name: Circadian period lengthening under constant light
      target: Reduced AMPA Receptor-Mediated Excitatory Current
      direction: INCREASED
      interpretation: >-
        Enhanced circadian sensitivity to light in the mutant, indicating that reduced GluA3
        current alters photic entrainment as well as sleep consolidation.
      evidence:
      - reference: PMID:29016847
        reference_title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Gria3A653T mice showed enhanced period lengthening under constant light compared to wild-type mice, suggesting an increased sensitivity to light."
        explanation: >-
          Reports the measured circadian phenotype under constant light.
    evidence:
    - reference: PMID:29016847
      reference_title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We introduced the orthologous mutation into a mouse strain by CRISPR-Cas9 mutagenesis and found that hemizygous mutants displayed significant differences in the structure of their activity and sleep compared to wild-type littermates."
      explanation: >-
        Establishes that the model carries the orthologous patient allele and that it produces a
        measurable phenotype, which is what makes it informative for this node.

- name: Transgenic Drosophila expressing mutant human GluA3
  species: Drosophila melanogaster
  genotype: transgenic expression of human GluA3 p.Ala615Val combined with the Lurcher leaky-channel alteration
  publication: PMID:35031858
  category: Genetically engineered
  description: >-
    Heterologous in vivo assay used to test whether the p.Ala615Val allele behaves as a gain of
    function. The mutant produced developmental defects only when combined with a leaky-channel
    alteration, a genetic interaction consistent with excess channel activity.
  modeled_mechanisms:
  - target: GluA3 Gain of Function
    relationship: MEASURES
    fidelity: LOW
    description: >-
      Reads out the functional direction of a human allele through a developmental phenotype in
      a whole organism, complementing the patch-clamp measurement.
    limitations: >-
      Drosophila has no orthologous AMPA receptor heterotetramer and the assay requires
      co-expression with an artificial leaky-channel allele, so it reports the direction of the
      effect rather than any disease-relevant circuit consequence.
    evidence:
    - reference: PMID:35031858
      reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "A fly line expressing a human GluA3 mutant possessing our variant and the Lurcher variant, which makes ion channels leaky, showed developmental defects, while one expressing a mutant possessing either of them did not."
      explanation: >-
        The synthetic genetic interaction with a leaky-channel allele is the in vivo readout for
        gain of function.

experimental_models:
- name: Heterologous AMPA receptor expression with patch-clamp electrophysiology
  experimental_model_type: CELL_LINE
  description: >-
    Recombinant expression of wild-type and variant GluA3 in a heterologous cell system,
    recorded by patch clamp, is the assay that assigns each GRIA3 allele to the
    loss-of-function, gain-of-function or functionally neutral class. It is the method behind
    the taxonomy on which this entry's whole pathograph branches.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:38038360
  modeled_mechanisms:
  - target: GluA3 Gain of Function
    relationship: MEASURES
    fidelity: MODERATE
    description: >-
      Measures agonist potency, response time course, desensitisation and deactivation, from
      which the gain-of-function direction is assigned.
    limitations: >-
      Recombinant receptors of defined subunit composition lack the auxiliary-subunit
      environment, developmental context and native heterotetramer stoichiometry of a real
      synapse, so the measured kinetics predict direction but not magnitude of circuit effect.
    readouts:
    - name: Receptor desensitisation and deactivation kinetics
      target: GluA3 Gain of Function
      direction: ALTERED
      interpretation: >-
        Slowed desensitisation and deactivation define the gain-of-function class.
      evidence:
      - reference: PMID:35031858
        reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "Patch-clamp recordings showed that the human GluA3 mutant (p.Ala615Val) had slower desensitization and deactivation kinetics."
        explanation: >-
          Reports the measured kinetic parameters that define the gain-of-function assignment.
    evidence:
    - reference: PMID:37921875
      reference_title: "Clinical and functional consequences of GRIA variants in patients with neurological diseases."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "These variants produce changes in agonist EC50, response time course, desensitization, and/or receptor surface expression."
      explanation: >-
        Establishes the parameter set the assay reports and that it discriminates functional
        consequences of GRIA variants.
  - target: GluA3 Loss of Function
    relationship: MEASURES
    fidelity: MODERATE
    description: >-
      The same assay assigns loss of function, including the closed-channel mechanism that
      leaves protein expression intact.
    limitations: >-
      Cannot distinguish reduced current caused by fewer surface receptors from reduced current
      per receptor without a separate surface-expression measurement, and gives no information
      about tissue-specific transcript abundance for splice alleles.
    evidence:
    - reference: PMID:38038360
      reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Here, we evaluated the impact on AMPAR function of one frameshift and 43 rare missense GRIA3 variants identified in patients with NDD by electrophysiological assays."
      explanation: >-
        Describes the assay and the scale at which it was applied to assign functional class.

- name: HEK293T minigene splicing assay
  experimental_model_type: CELL_LINE
  description: >-
    Minigene reporter assay used to resolve GRIA3 splice-site variants of uncertain
    significance, by testing directly whether the candidate allele alters exon inclusion.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:42666715
  modeled_mechanisms:
  - target: GluA3 Loss of Function
    relationship: MEASURES
    fidelity: MODERATE
    description: >-
      Demonstrates the RNA-level lesion — exon 2 skipping — through which a canonical
      splice-donor variant abolishes normal GluA3 production.
    limitations: >-
      A minigene reports splice-site strength in an artificial construct in a non-neuronal cell
      line; it validates aberrant splicing but not the transcript abundance or isoform ratio in
      patient brain.
    readouts:
    - name: Exon 2 inclusion in the minigene transcript
      target: GluA3 Loss of Function
      direction: DECREASED
      interpretation: >-
        Exon 2 skipping is the loss-of-function mechanism for this allele.
      evidence:
      - reference: PMID:42666715
        reference_title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "The minigene in vitro splicing assay demonstrated that this variant affects splicing, leading to exon 2 skipping"
        explanation: >-
          Reports the measured splicing outcome.

discussions:
- discussion_id: gria3_ko_mouse_no_cognitive_phenotype
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    Why does the Gria3 null mouse show no spatial memory deficit when global developmental
    impairment is present in every functionally characterised human patient?
  attaches_to:
  - pathophysiology#Disturbed Excitatory Synaptic Transmission and Plasticity
  - phenotypes#Global developmental delay
  - animal_models#Gria3 knockout mouse
  rationale: >-
    This is not an absence of evidence but a positive negative result: the knockout was tested
    on the Morris water maze and the Y-maze and performed normally, while reproducing
    aggression, sociality, motor and monoaminergic changes. Three readings are open and the
    data do not separate them. Developmental compensation by GluA1- and GluA2-containing
    receptors may mask the lesion in a constitutive null in a way that a patient missense
    allele — which still produces a subunit that assembles into heterotetramers — would not.
    Rodent spatial navigation may simply be the wrong proxy for human global developmental
    impairment. Or GluA3 loss may genuinely not be sufficient for the cognitive phenotype,
    with the human presentation requiring additional species-specific circuit context. Which
    of these holds matters for whether any Gria3 rodent model can serve as a preclinical
    efficacy readout for this disorder.
  evidence:
  - reference: PMID:22285418
    reference_title: "GluA3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Gria3-/Y mice showed no significant deficit in spatial memory function in Morris-water maze and Y-maze tests, and normal levels of testosterone."
    explanation: >-
      The negative cognitive result in the knockout that creates the mismatch with the human
      phenotype.
  - reference: PMID:38038360
    reference_title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25)."
    explanation: >-
      The human side of the mismatch: developmental impairment is universal in patients.

- discussion_id: female_heterozygote_severity_determinants
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What determines whether a heterozygous female carrying a GRIA3 variant is unaffected,
    mildly affected, or has a developmental and epileptic encephalopathy?
  attaches_to:
  - pathophysiology#GluA3 Gain of Function
  - inheritance#X-linked inheritance with mechanism-dependent expression in females
  rationale: >-
    Carrier mothers transmitting loss-of-function alleles are usually clinically normal, yet
    females with de novo gain-of-function alleles can be as severely affected as any male, and
    one female with a de novo allele has only moderate intellectual disability with a good
    adaptive profile. X-chromosome inactivation generates a mosaic neuronal population
    expressing either the wild-type or the mutant allele, which is the obvious candidate
    explanation, but no study has measured skewing against severity in this gene, and the
    authors of the largest case series state explicitly that neither X-inactivation nor
    mosaicism fully accounts for the range of symptoms. The functional direction of the allele
    is a confounder that has never been controlled for: female cases are enriched for gain of
    function, so an apparent sex effect may partly be an allele-class effect. Resolving this
    matters directly for counselling carrier females.
  evidence:
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "As an X-linked gene, GRIA3 is subject to X-chromosome inactivation (XCI), which generates mosaic expression in females and results in a mixed neuronal population expressing either the wild-type or the mutant allele."
    explanation: >-
      States the candidate mechanism whose contribution to female severity is unmeasured.
  - reference: PMID:36726007
    reference_title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neither X-inactivation nor mosaicism can entirely account for the range of symptoms or severity."
    explanation: >-
      Explicit statement that the obvious explanation is insufficient, which is what makes this a
      gap rather than a settled question.

- discussion_id: mechanism_matched_ampar_pharmacology
  kind: OPEN_QUESTION
  status: OPEN
  prompt: >-
    Should AMPA receptor pharmacology in GRIA3 disease be selected by the measured functional
    direction of the patient's own variant, and is an AMPAR antagonist such as perampanel
    appropriate for gain-of-function disease?
  attaches_to:
  - treatments#Carbamazepine for Gain-of-Function Disease
  - pathophysiology#GluA3 Gain of Function
  - pathophysiology#GluA3 Loss of Function
  rationale: >-
    The bidirectional allelic architecture makes this the sharpest open therapeutic question in
    the disorder. The sensitivity of variant receptors to AMPAR-selective modulators has been
    measured in recombinant assays, and one clinician group has proposed perampanel, a
    non-competitive AMPAR antagonist, as a candidate first-line agent. Against that, there is
    one reported perampanel failure — in the male patient described by Trivisano and
    colleagues — which a later group cites as behaving the way loss of function predicts. The
    electrophysiology in that later paper was done on their own p.Glu787Gly allele, not on the
    treated patient, so this is a same-residue inference and not a measurement in the patient
    who failed the drug. But direction matters both ways:
    enhancing an already over-active receptor, or blocking one that is already under-conducting,
    would be expected to worsen the phenotype. The single supporting clinical observation is the
    N-of-1 carbamazepine response in a functionally confirmed gain-of-function male, and the one
    apparent counterexample is a carbamazepine failure in a patient whose variant was never
    tested electrophysiologically — which is exactly the ambiguity a mechanism-matched strategy
    is meant to remove. No trial has tested the strategy, and 13 of 44 tested rare GRIA3 missense
    alleles were functionally neutral, so the strategy also presupposes routine access to
    variant-level electrophysiology that does not currently exist in clinical practice.
  evidence:
  - reference: PMID:37921875
    reference_title: "Clinical and functional consequences of GRIA variants in patients with neurological diseases."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We evaluated the sensitivity of variant receptors to AMPAR-selective modulators including FDA-approved drugs to explore potential targeted therapeutic options."
    explanation: >-
      Establishes that variant-specific pharmacological sensitivity has been measured in vitro,
      which is the basis for proposing a mechanism-matched strategy.
  - reference: PMID:34731330
    reference_title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a targeted trial with a selective non-competitive AMPA receptor antagonist (Perampanel) proved to be ineffective, as expected in case of loss of function of the receptor"
    explanation: >-
      The mirror image of the carbamazepine result. Note carefully whose patient this is: the
      failure occurred in a patient reported by another group, and the loss of function was
      measured in the citing authors' own p.Glu787Gly allele at the same residue. The quoted
      "as expected in case of loss of function" is therefore their inference across a shared
      residue, not an electrophysiological result in the treated patient.
  - reference: PMID:41462794
    reference_title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is worth considering that the trial of perampanel, an antiepileptic drug with the AMPA receptor mechanism of action, did not prove clinical or EEG improvement in a previous report"
    explanation: >-
      A later group reading the same perampanel failure the same way. This is a second citation
      of one event, not a second event, so it corroborates the interpretation and does nothing
      to establish that the result generalises.
  - reference: PMID:35031858
    reference_title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "GRIA3 GOF variants may cause an NDD phenotype distinctive from that of LOF variants, and drugs suppressing glutamatergic neurotransmission may ameliorate this phenotype."
    explanation: >-
      The clinical proposal that treatment should be matched to the functional direction of the
      variant.

references:
- reference: PMID:38038360
  title: "Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes."
- reference: PMID:35031858
  title: "Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant."
- reference: PMID:36726007
  title: "GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy."
- reference: PMID:29016847
  title: "A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability."
- reference: PMID:41462794
  title: "Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene."
- reference: PMID:42666715
  title: "Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms."
- reference: PMID:34731330
  title: "Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene."
- reference: PMID:24721225
  title: "X-exome sequencing in Finnish families with intellectual disability--four novel mutations and two novel syndromic phenotypes."
- reference: PMID:22285418
  title: "GluA3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum."
- reference: PMID:36429079
  title: "Expression and Interaction Proteomics of GluA1- and GluA3-Subunit-Containing AMPARs Reveal Distinct Protein Composition."
- reference: PMID:37921875
  title: "Clinical and functional consequences of GRIA variants in patients with neurological diseases."

notes: >-
  Curated from the Edison/falcon deep-research report
  research/Syndromic_X-linked_Intellectual_Disability_94-deep-research-falcon.md. The
  named-entity preflight against MONDO:0010402 passed (GRIA3 mentioned 24 times, top gene in
  the report), so the report is genuinely about this disease.

  Corrections made to CURIEs the report proposed, all of which its own Term Validation section
  reported as clean (47/47 resolved, confabulation_rate 0.0) — that section checks only that a
  CURIE exists and is named consistently, not that it names the right concept.

  One was a wrong concept: the report offered HP:0002169 as "Hyperekplexia", but HP:0002169 is
  Clonus. Hyperekplexia is covered by HP:0002267 Exaggerated startle response, which is what
  this entry binds.

  Four were stale or paraphrased labels against the canonical HPO label: "Muscular hypotonia"
  for HP:0001252 (now Hypotonia), "Myoclonic seizure" for HP:0002123 (Generalized myoclonic
  seizure), "Movement abnormality" for HP:0100022 (Abnormality of movement), and "Abnormal
  sleep pattern" for HP:0002360 (Sleep disturbance). It also suggested "thalamus
  (UBERON:0001897)", whose canonical label is dorsal plus ventral thalamus; that term is not
  used in this entry.

  Three of the report's suggestions resolved to a term one level too general, and a more exact
  HPO term was bound instead: HP:0006979 Sleep-wake cycle disturbance rather than the parent
  HP:0002360; HP:0031475 Status epilepticus without prominent motor symptoms (exact synonym
  "Nonconvulsive status epilepticus") rather than the parent HP:0002133; and HP:0012389
  Appendicular hypotonia, defined as muscular hypotonia of one or more limbs, rather than
  HP:0001252, since the cohort figure being cited is specifically for limb hypotonia.

  All 13 of the report's citations are DOI-only — it states explicitly that PMIDs were not
  present in the retrieved metadata. Every DOI was resolved to a PMID before use (11 via the
  PMC ID converter, one — the Hamanaka carbamazepine paper, PMID:35031858 — by PubMed title
  search after the converter failed), so no evidence item in this entry sits on a DOI prefix
  that the gating reference validator skips.

  Two of the report's sources were deliberately not used. The exon 5-12 deletion prenatal
  diagnosis case (DOI 10.26717/BJSTR.2023.52.008322) is not indexed in PubMed or PMC and could
  not be given a PMID; its content — a hemizygous multi-exon deletion segregating through
  carrier females, detected prenatally in amniotic fluid — is therefore recorded here rather
  than curated as evidence, and the structural-variant claim in the pathograph is cited to
  PMID:34731330 instead. The Huang et al. brain-region transcriptomics work
  (DOI 10.1101/2024.11.15.623468) is an unreviewed bioRxiv preprint modelling a
  schizophrenia-associated protein-truncating Gria3 allele rather than this disorder, so the
  downstream regional transcriptional and glial adaptation it describes is not curated as a
  pathophysiology node.

  ClinicalTrials.gov was queried directly rather than trusting the report. A GRIA3 term search
  returns one study, NCT03676569, an intrathecal autologous adipose-derived regenerative cell
  trial in autoimmune refractory epilepsy with no GRIA3 relationship; a condition search for
  GRIA3-related neurodevelopmental disorder returns nothing. No clinical_trials block is
  therefore curated.

  Frequencies in the phenotypes section derive from the 25-patient functionally characterised
  cohort in PMID:38038360 and are cohort proportions, not population frequencies. Hypotonia and
  hypertonia are both tagged FREQUENT because the cohort mixes the two allele classes; within a
  branch they are close to mutually exclusive, which is what the pathograph records.

  Two claims from the source report were checked against the cached papers and found to
  overstate them, and are curated in the weaker form the sources actually support. The report
  presents the female non-convulsive status epilepticus case as the first report of that
  manifestation; the paper itself says status epilepticus was already documented in two
  patients and claims only the first *female* case, so both are recorded. The report also
  attributes hyperreflexia to the gain-of-function arm of the 25-patient cohort; the string
  does not occur anywhere in that paper, and hyperreflexia comes only from the single
  functionally confirmed p.Ala615Val male, so it is not curated as a cohort-level association.

  The strongest published support for treating allele direction as therapeutically decisive is
  not in the report at all and was found by reading the cached full texts: perampanel, an AMPA
  receptor antagonist, was tried and proved ineffective, and a later group reads that outcome
  as what loss of function predicts. It is one reported failure cited by two papers, not two
  failures, and the loss-of-function characterisation belongs to the citing authors' own
  same-residue allele rather than to the treated patient — the entry states both limits where
  it cites the result. It is the mirror image of the carbamazepine-in-gain-of-function
  observation and is cited in the mechanism_matched_ampar_pharmacology discussion.

  Two identity checks requested in review and run against the authorities. PubMed has no
  GeneReviews chapter for this gene: both `GRIA3[TI] GeneReviews[TI]` and
  `GRIA3 AND GeneReviews[Book]` return zero records, so no `references[]` entry carries a
  GeneReviews tag and none should. The synonym "syndromic X-linked intellectual disability 29"
  is genuine and belongs to this concept rather than to a neighbouring one: MONDO:0010402
  carries it, together with MRXS29 and "mental retardation, X-linked, syndromic 29", because
  the Wu-type entity was numbered 29 in the older syndromic X-linked series before being
  renumbered 94.

📚

References & Deep Research

References

11

PMID:38038360

Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes.

No top-level findings curated for this source.

PMID:35031858

Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function GRIA3 variant.

No top-level findings curated for this source.

PMID:36726007

GRIA3 p.Met661Thr variant in a female with developmental epileptic encephalopathy.

No top-level findings curated for this source.

PMID:29016847

A point mutation in the ion conduction pore of AMPA receptor GRIA3 causes dramatically perturbed sleep patterns as well as intellectual disability.

No top-level findings curated for this source.

PMID:41462794

Non-Convulsive Status Epilepticus and Mild Neurodevelopmental Phenotype in a Female with a Novel p.Thr657Ala Variant in the GRIA3 Gene.

No top-level findings curated for this source.

PMID:42666715

Reclassification of the GRIA3 splice-site variant in an X-linked family with intellectual disability and psychiatric symptoms.

No top-level findings curated for this source.

PMID:34731330

Myoclonic status epilepticus and cerebellar hypoplasia associated with a novel variant in the GRIA3 gene.

No top-level findings curated for this source.

PMID:24721225

X-exome sequencing in Finnish families with intellectual disability--four novel mutations and two novel syndromic phenotypes.

No top-level findings curated for this source.

PMID:22285418

GluA3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum.

No top-level findings curated for this source.

PMID:36429079

Expression and Interaction Proteomics of GluA1- and GluA3-Subunit-Containing AMPARs Reveal Distinct Protein Composition.

No top-level findings curated for this source.

PMID:37921875

Clinical and functional consequences of GRIA variants in patients with neurological diseases.

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 41 citations 2026-09-03T20:36:45.380316

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: Syndromic X-linked Intellectual Disability 94
MONDO ID: (if available)
Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Syndromic X-linked Intellectual Disability 94 covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Present this section as an ordered causal chain first, then the detail below. Open with a numbered sequence of mechanistic steps running from the initiating lesion (mutation, exposure, infection) to the clinical manifestation, one step per line, each naming what it causes next. State the causal verb explicitly ("leads to", "results in") and say where a step is inferred rather than demonstrated. Where the mechanism branches, show the branch. The categories below are a checklist of what to cover within those steps, not the organizing structure — a step may draw on several of them, and a category may contribute to several steps.

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest NCIT (NCI Thesaurus) clinical-intervention terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, NCIT, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (NCIT terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Syndromic X-linked intellectual disability 94: disease-characteristics report

Executive summary and scope

Syndromic X-linked intellectual disability 94 is a very rare GRIA3-related neurodevelopmental disorder caused by altered function or dosage of the X-chromosomal AMPA-receptor subunit GluA3. The current concept is broader than the historical male-predominant syndrome: pathogenic loss-of-function (LoF) and gain-of-function (GoF) alleles produce partly distinct phenotypes, and females can be affected, particularly by de novo heterozygous GoF variants. The best recent dataset comprises only 25 affected individuals, so frequencies are provisional rather than population estimates. In that series, all 25 had global developmental impairment, 12/25 seizures, 14/25 movement disorders, 13/25 hypotonia, and 10/25 hypertonia. GoF was associated with earlier seizures and hypertonia, whereas LoF was associated with hypotonia and sleep disturbance. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)

This report treats “syndromic X-linked intellectual disability 94,” historical Wu-type X-linked syndromic intellectual developmental disorder, and the broader GRIA3-related neurodevelopmental disorder as overlapping concepts. The broader term is preferable when describing heterozygous affected females or GoF disease that does not follow a simple recessive model. Evidence is predominantly aggregated from small pedigrees, case reports, and one multicenter cohort—not electronic-health-record incidence data.

Evidence domain	Key finding with exact quantitative values where available	Evidence type	Source/date/DOI
Contemporary genotype–phenotype spectrum	Among 25 patients from 23 families carrying 17 functionally abnormal variants, all had global developmental impairment: 9/25 moderate, 12/25 severe; 12/25 had seizures, 13/25 hypotonia, 10/25 hypertonia, and 14/25 movement disorders, including hyperekplexia or nonepileptic erratic myoclonus in 8/25. Testing of one frameshift and 43 missense variants found 31 function-altering LoF/GoF variants and 13 apparently neutral variants. Median seizure onset was 1 month for GoF versus 16 months for LoF.	Human clinical cohort; in-vitro electrophysiology	Rinaldi et al., Brain; online 2023-12-01, 2024 volume; DOI 10.1093/brain/awad403 (rinaldi2024gainoffunctionandlossoffunction pages 1-3)
Structural variant and prenatal diagnosis	A hemizygous GRIA3 exon 5–12 deletion was found in an affected male with intellectual disability, schizophrenia, brain atrophy, seizures, and episodic irritability. The pregnant woman and maternal grandmother were heterozygous; amniotic-fluid testing detected the familial deletion in the fetus.	Human pedigree; prenatal molecular diagnosis	Wang et al., Biomedical Journal of Scientific & Technical Research; published 2023-09-15; DOI 10.26717/BJSTR.2023.52.008322 (jiang2023geneticanalysisand pages 1-2)
Female developmental and epileptic encephalopathy	A 13-year-old girl carried de novo heterozygous NM_007325.5:c.1982T>C, p.Met661Thr, absent from several population databases and classified likely pathogenic. Hypertonia was present at birth; seizures began at 3 months. Carbamazepine and ethosuximide were ineffective; lamotrigine, clobazam, levetiracetam, and lacosamide gradually controlled seizures.	Human clinical case; WES and segregation	Okano et al., Human Genome Variation; published 2023-02-02; DOI 10.1038/s41439-023-00232-1 (okano2023gria3p.met661thrvariant pages 1-3)
Genotype-guided symptomatic treatment	A boy with de novo hemizygous GRIA3 c.1844C>T, p.Ala615Val had neurodevelopmental impairment, seizures, hypertonia, and hyperreflexia. Carbamazepine ameliorated seizures and hypertonia. Patch-clamp recordings showed slower receptor desensitization and deactivation, supporting GoF.	Human case; in-vitro electrophysiology; transgenic fly	Hamanaka et al., Human Genetics; published online 2022-01-15; DOI 10.1007/s00439-021-02416-7 (hamanaka2022ameliorationofa pages 1-2)
Sleep–wake phenotype and allelic mouse model	Two brothers with severe developmental delay and p.Ala653Thr had wake periods up to 106 hours and sleep periods up to 48 hours. In vitro, the variant stabilized the channel in a closed conformation. CRISPR knock-in hemizygous mice had fewer brief sleep/activity bouts and enhanced period lengthening under constant light.	Human pedigree; in vitro; CRISPR knock-in mouse	Davies et al., Human Molecular Genetics; advance publication 2017-07-14; DOI 10.1093/hmg/ddx270 (davies2017apointmutation pages 1-2)
Knockout behavior and monoamines	Compared with wild-type littermates (n=14), knockout mice (n=13) showed increased aggression (p=0.011), sociality (p=0.01), male–male interaction (p=0.005), peripheral activity (p=0.037), and minor rotarod impairment (p=0.016). Striatal dopamine increased (p=0.034) and olfactory-bulb serotonin turnover decreased (p=0.002).	Germline knockout mouse; behavioral and neurochemical assays	Adamczyk et al., Behavioural Brain Research; 2012-04-01; DOI 10.1016/j.bbr.2012.01.007 (adamczyk2012glua3deficiencyinmice pages 1-3)
AMPAR interaction proteomics	Hippocampal proteomics in wild-type and Gria3-knockout mice showed that GluA2/3 receptors most strongly co-purified with CNIH-2, TARP-γ2/Stargazin, and Noelin-1/OLFM1, identifying subtype-specific partners involved in receptor trafficking and gating.	Mouse hippocampal interaction proteomics	van der Spek et al., Cells; published 2022-11-17; DOI 10.3390/cells11223648 (spek2022expressionandinteraction pages 1-2)
Brain-region-specific molecular profiling	Bulk RNA-seq across six brain regions at 1 and 3 months found 153 regional DEG calls/148 unique DEGs at 1 month and 209/201 at 3 months, with downregulated activity-regulated genes and region-specific immune, glial, and oligodendrocyte-pathway changes. Synaptic proteome composition was also altered.	Mouse transcriptomics and synaptic proteomics; non-peer-reviewed preprint	Huang et al., bioRxiv; posted 2024-11-17; DOI 10.1101/2024.11.15.623468 (huang2024brainregionspecificchangesand pages 1-3)

Table: Compact evidence matrix covering clinical genotype–phenotype findings, prenatal diagnosis, functional studies, treatment observations, and animal or omics models relevant to GRIA3-related syndromic X-linked intellectual disability 94.

1. Disease information

Definition

The disorder is a congenital or early-childhood neurodevelopmental syndrome characterized by developmental delay/intellectual disability, variably accompanied by epilepsy, altered muscle tone, movement disorder, behavioral or psychiatric manifestations, sleep disturbance, dysmorphism, and occasionally cerebellar or cerebral structural abnormalities. GRIA3 encodes GluA3, a pore-forming component of postsynaptic AMPA-type ionotropic glutamate receptors that mediate rapid excitatory neurotransmission. (rinaldi2024gainoffunctionandlossoffunction pages 1-3, okano2023gria3p.met661thrvariant pages 1-3)

Identifiers and nomenclature

OMIM disease: #300699, reported as Wu-type X-linked syndromic intellectual developmental disorder/MRXSW in the retrieved literature. (hu2026reclassificationofthe pages 1-2)
OMIM gene: GRIA3, *305915. (okano2023gria3p.met661thrvariant pages 1-3)
Gene location: Xq25. (hu2026reclassificationofthe pages 1-2, okano2023gria3p.met661thrvariant pages 1-3)
Common names: syndromic X-linked intellectual disability 94; MRX94; GRIA3-related neurodevelopmental disorder; GRIA3-related intellectual developmental disorder; Wu-type X-linked syndromic intellectual developmental disorder.
MONDO, Orphanet, MeSH, ICD-10/ICD-11: a disease-specific identifier was not verified in the retrieved primary literature. A knowledge base should not infer an exact MONDO or Orphanet code without direct ontology-database verification. Clinically, nonspecific intellectual-developmental-disorder and epilepsy codes may be used, but they are not equivalent to a molecular diagnosis.

Source granularity: Published evidence is disease-level aggregation of individually phenotyped patients and families. No prevalence study based on EHRs or administrative claims was identified.

2. Etiology

Causal factors and genetic risk

The primary cause is a germline pathogenic or likely pathogenic GRIA3 alteration. Reported classes include missense variants, canonical splice variants, frameshift variants, multi-exon deletions or duplications, larger rearrangements, and balanced translocations disrupting GRIA3. Approximately 20 variants had been reported by early 2023, although the 2024 functional study substantially expanded the tested missense spectrum. (rinaldi2024gainoffunctionandlossoffunction pages 1-3, okano2023gria3p.met661thrvariant pages 1-3)

Examples include:

LoF/closed-channel: p.Ala653Thr, which stabilized the receptor in a closed conformation and was associated with severe developmental delay and extreme sleep–wake disturbance. (davies2017apointmutation pages 1-2)
GoF: c.1844C>T, p.Ala615Val, with slowed desensitization/deactivation, hypertonia, hyperreflexia, and seizures. (hamanaka2022ameliorationofa pages 1-2)
Likely GoF phenotype: de novo c.1982T>C, p.Met661Thr in an affected girl; absent from EVS, 1000 Genomes, dbSNP, gnomAD, and HGVD and classified likely pathogenic under ACMG criteria PS2/PM2/PP2/PP3. Direct electrophysiology was not performed. (okano2023gria3p.met661thrvariant pages 1-3)
Splice disruption: c.268+1G>C caused exon-2 skipping in a minigene assay and was reclassified from VUS to likely pathogenic. (hu2026reclassificationofthe pages 4-5, hu2026reclassificationofthe pages 1-2)
Structural LoF: exon 5–12 deletion segregating through carrier females in a Chinese family. (jiang2023geneticanalysisand pages 1-2)
Additional familial missense alleles: c.2360A>G, p.Glu787Gly, and c.1888G>C, p.Gly630Arg. (rinaldi2022myoclonicstatusepilepticus pages 1-2, philips2014xexomesequencingin pages 4-6)

The 2024 study tested one frameshift and 43 rare missense alleles: 31 altered receptor function as LoF or GoF and 13 appeared functionally neutral. This is important diagnostically: rarity and missense location alone are insufficient evidence of pathogenicity. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)

Environmental, lifestyle, infectious, and protective factors

No environmental exposure, infection, diet, smoking, alcohol use, occupational exposure, or lifestyle factor has been demonstrated to cause or materially modify this Mendelian disorder. No validated protective allele, modifier gene, or environmental protective factor is known. Family history and male sex increase prior probability for inherited hemizygous LoF disease, but they are not environmental risk factors.

No disease-specific gene–environment interaction has been established. Light sensitivity in the p.Ala653Thr mouse and sleep phenotype suggests that environmental light can modulate circadian expression after the genetic lesion, but this is not evidence that light causes the disorder. (davies2017apointmutation pages 1-2)

3. Phenotypes

The following frequencies derive from the 25-person functional cohort and should not be generalized as precise population frequencies:

Global developmental impairment/intellectual disability: 25/25; moderate in 9/25 and severe in 12/25. Suggested HPO: Global developmental delay (HP:0001263), Intellectual disability (HP:0001249), Severe global developmental delay. Onset is infancy/early childhood and impairment is generally lifelong. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)
Epilepsy/seizures: 12/25. Types included focal motor 6/12, unknown-onset motor 4/12, focal impaired-awareness 1/12, absence/atypical absence 2/12, myoclonic 5/12, generalized tonic-clonic 1/12, and atonic 1/12. Suggested HPO: Seizure (HP:0001250), Myoclonic seizure (HP:0002123), Focal motor seizure, Absence seizure. GoF median onset was 1 month versus 16 months for LoF. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)
Hypotonia: 13/25, enriched among LoF cases. HPO: Muscular hypotonia (HP:0001252). (rinaldi2024gainoffunctionandlossoffunction pages 1-3)
Hypertonia/spasticity/hyperreflexia: 10/25, enriched among GoF cases. HPO: Hypertonia (HP:0001276), Hyperreflexia (HP:0001347), Spasticity (HP:0001257). Hypertonia can be congenital, as in the p.Met661Thr girl. (rinaldi2024gainoffunctionandlossoffunction pages 1-3, okano2023gria3p.met661thrvariant pages 1-3)
Movement disorder: 14/25; hyperekplexia or nonepileptic erratic myoclonus in 8/25. HPO: Movement abnormality (HP:0100022), Hyperekplexia (HP:0002169), Myoclonus (HP:0001336), Chorea (HP:0002072). (rinaldi2024gainoffunctionandlossoffunction pages 1-3)
Sleep disturbance: particularly associated with LoF. Two p.Ala653Thr brothers remained awake for up to 106 hours and slept for up to 48 hours. HPO: Abnormal sleep pattern (HP:0002360), Sleep–wake cycle disturbance. (rinaldi2024gainoffunctionandlossoffunction pages 1-3, davies2017apointmutation pages 1-2)
Behavioral/psychiatric manifestations: autism, self-injury, aggression, emotional instability, psychosis-like symptoms, hallucinations, and spatial-memory deficits have been reported. In one Finnish family, three adult males had severe ID, autistic features, self-injury, and aggressive outbursts. Suggested HPO: Autistic behavior (HP:0000729), Aggressive behavior (HP:0000718), Self-injurious behavior (HP:0100716), Psychotic episodes (HP:0000725). (hu2026reclassificationofthe pages 4-5, philips2014xexomesequencingin pages 4-6)
Brain abnormalities: reported findings include cerebellar hypoplasia, cerebral or frontal atrophy, and ventricular enlargement, but imaging may be normal. Suggested HPO: Cerebellar hypoplasia (HP:0001321), Cerebral atrophy (HP:0002059), Ventriculomegaly (HP:0002119). In the p.Met661Thr case, slight frontal atrophy and ventricular enlargement were not progressive at age 13. (rinaldi2022myoclonicstatusepilepticus pages 1-2, okano2023gria3p.met661thrvariant pages 1-3)
Motor/orthopedic consequences: delayed milestones, impaired gait, scoliosis, hip dislocation, and bedridden status can occur in severe disease. HPO: Delayed gross motor development (HP:0002194), Gait disturbance (HP:0001288), Scoliosis (HP:0002650), Hip dislocation (HP:0002827). (okano2023gria3p.met661thrvariant pages 1-3)
Growth/dysmorphism: short stature, macrocephaly, constitutional weakness, and variable facial dysmorphism have been described but are not universal. The p.Met661Thr girl lacked characteristic facies. (rinaldi2022myoclonicstatusepilepticus pages 1-2, jiang2023geneticanalysisand pages 1-2, okano2023gria3p.met661thrvariant pages 1-3)

Quality of life: No validated EQ-5D, SF-36, PROMIS, or disease-specific quality-of-life study was identified. Nevertheless, severe cognitive and language impairment, refractory epilepsy, abnormal tone, impaired mobility, behavioral dysregulation, and sleep disruption can substantially restrict communication, education, autonomy, and caregiver sleep. This functional impact is inferred from case descriptions rather than standardized instruments.

4. Genetic and molecular information

Causal gene: GRIA3; protein GluA3/GluR3; Xq25; OMIM *305915. HGNC numerical identifier was not verified in the retrieved sources. (okano2023gria3p.met661thrvariant pages 1-3)
Origin: Germline. Both inherited and de novo disease occur. No evidence supports a somatic disease mechanism.
Inheritance: Historically X-linked recessive/semidominant. Hemizygous males frequently inherit LoF alleles from clinically healthy mothers; however, de novo hemizygous male disease and heterozygous female disease are established. Nearly all affected females in the recent cohort carried de novo heterozygous GoF variants. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)
Functional consequences: LoF mechanisms include disrupted transcription/splicing, reduced protein stability, reduced ion permeation, or stabilization of a closed channel. GoF commonly prolongs receptor activation by slowing deactivation/desensitization. Both too little and too much AMPAR activity can impair neurodevelopment. (rinaldi2024gainoffunctionandlossoffunction pages 1-3, davies2017apointmutation pages 1-2, hamanaka2022ameliorationofa pages 1-2)
Population frequency: Individual disease alleles are generally absent or extremely rare in population databases. Absence from gnomAD was documented for c.268+1G>C and p.Met661Thr. Exact allele frequencies for every reported variant were not available. (hu2026reclassificationofthe pages 4-5, okano2023gria3p.met661thrvariant pages 1-3)
ACMG classification: Classification must be variant-specific. Functional electrophysiology, RNA studies, segregation, de novo status, and population absence are particularly valuable. A functionally neutral rare missense allele should not automatically be labeled pathogenic. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)
Modifier genes: None validated.
Epigenetics: Skewed X-chromosome inactivation is a plausible determinant of female severity, but no reproducible disease-specific methylation episignature has been established. (rubino2025nonconvulsivestatusepilepticus pages 7-8, hu2026reclassificationofthe pages 1-2)
Chromosomal abnormalities: GRIA3-disrupting translocations, deletions, duplications, and multi-exon copy-number changes are reported. Some Xq25 duplications may include neighboring genes, complicating attribution.

5. Environmental information

No toxin, radiation exposure, pollutant, lifestyle behavior, nutritional deficiency, or infectious agent is known to cause GRIA3-related XLID94. Consequently, CTD-style chemical–disease causality and pathogen annotations are not currently justified. Routine avoidance of neurotoxic exposures is sensible general care but is not disease-specific prevention.

6. Mechanism and pathophysiology

Ordered causal chain

A germline GRIA3 sequence or structural variant leads to altered GluA3 abundance, assembly, trafficking, or channel gating.
Altered GluA3 leads to LoF or GoF of GluA3-containing AMPA receptors at postsynaptic membranes.
LoF leads to reduced/abnormally brief excitatory currents, whereas GoF leads to prolonged or excessive currents through slowed deactivation/desensitization.
Abnormal AMPAR current leads to disturbed excitatory synaptic transmission, synaptic plasticity, and excitation–inhibition balance in developing neural circuits.
Circuit dysfunction leads to impaired learning, memory, language, motor development, behavior, and sleep regulation; excessive or mistimed excitation can lead to epilepsy and hypertonic/hyperkinetic phenotypes.
Inferred branch: chronic synaptic dysfunction leads to region- and age-specific transcriptional and proteomic adaptation in neurons and glia, potentially contributing to psychiatric and behavioral manifestations.

Mechanistic detail

AMPARs are glutamate-gated cation channels assembled as tetramers from GluA1–GluA4. GluA3-containing receptors are concentrated at the postsynaptic density and participate in rapid excitatory transmission and activity-dependent plasticity. In hippocampus, GluA2/3 is the second major AMPAR population after GluA1/2. Suggested GO terms include AMPA glutamate receptor activity (GO:0004971), ionotropic glutamate receptor signaling pathway (GO:0035235), chemical synaptic transmission (GO:0007268), regulation of synaptic plasticity (GO:0048167), learning or memory (GO:0007611), and transmembrane ion transport (GO:0034220). (okano2023gria3p.met661thrvariant pages 1-3, spek2022expressionandinteraction pages 1-2)

The strongest genotype-specific human mechanism comes from electrophysiology. p.Ala653Thr stabilized a closed channel, while p.Ala615Val slowed desensitization and deactivation and behaved as GoF. In the large 2024 study, 31/44 tested rare variants altered function, establishing bidirectional channel dysfunction rather than uniform haploinsufficiency. (rinaldi2024gainoffunctionandlossoffunction pages 1-3, davies2017apointmutation pages 1-2, hamanaka2022ameliorationofa pages 1-2)

Interaction proteomics showed that hippocampal GluA2/3 receptors preferentially co-purify with CNIH2, CACNG2/TARP-γ2 (stargazin), and OLFM1/Noelin-1, proteins affecting receptor biogenesis, trafficking, surface expression, mobility, and gating. Relevant compartments are postsynaptic membrane (GO:0045211), postsynaptic density (GO:0014069), AMPA glutamate receptor complex (GO:0032281), neuronal synapse (GO:0098984), and plasma membrane. (spek2022expressionandinteraction pages 1-2)

A 2024 mouse preprint found downregulated activity-regulated genes in cortical regions and region-specific immune-, glial-, and oligodendrocyte-related changes after a Gria3 protein-truncating mutation. Across six regions there were 148 unique differentially expressed genes at one month and 201 at three months. This supports downstream network adaptation but remains non-peer-reviewed and models schizophrenia-associated Gria3 LoF rather than XLID94 directly. (huang2024brainregionspecificchangesand pages 1-3)

No disease-specific human metabolomic, lipidomic, single-cell, spatial-transcriptomic, or methylation signature was identified. There is no established primary immune, inflammatory, apoptotic, autophagic, mitochondrial, or metabolic lesion. Any glial/immune signal presently appears downstream and model-derived.

Suggested cell ontology annotations: neuron (CL:0000540), glutamatergic neuron (CL:0000679), cerebral-cortex neuron, hippocampal neuron, thalamic neuron, spinal motor neuron, oligodendrocyte (CL:0000128), astrocyte (CL:0000127), and microglial cell (CL:0000129). Direct disease causality is strongest for neurons; glial annotations are based mainly on mouse profiling.

7. Anatomical structures affected

Primary organ/system: central nervous system and nervous system.
Brain regions implicated clinically or experimentally: cerebral cortex, frontal/prefrontal cortex, hippocampus, thalamus, striatum, cerebellum, substantia nigra, and sleep/circadian circuits. GluA3-containing AMPARs are broadly distributed, especially in hippocampus, cortex, and thalamus. (huang2024brainregionspecificchangesand pages 1-3, okano2023gria3p.met661thrvariant pages 1-3)
Peripheral/secondary structures: corticospinal and motor systems are implicated by hypertonia, hyperreflexia, gait abnormalities, scoliosis, and hip dislocation; these musculoskeletal changes are likely secondary to neurologic impairment. (okano2023gria3p.met661thrvariant pages 1-3)
Subcellular localization: postsynaptic plasma membrane, postsynaptic density, AMPAR tetramer, dendritic/synaptic compartments; ER-associated biogenesis and receptor trafficking are relevant upstream processes. (spek2022expressionandinteraction pages 1-2)
Suggested UBERON terms: brain (UBERON:0000955), cerebral cortex (UBERON:0000956), hippocampal formation (UBERON:0002421), thalamus (UBERON:0001897), striatum (UBERON:0002435), cerebellum (UBERON:0002037), spinal cord (UBERON:0002240), and skeletal muscle (UBERON:0001134, secondary involvement).
Lateralization: No consistent unilateral or asymmetric pattern is established.

8. Temporal development

The disorder begins prenatally at the molecular level and manifests congenitally or during infancy/early childhood. Developmental delay is chronic and usually recognized as milestones are missed. GoF disease can present with neonatal hypertonia and seizures in the first months; LoF-associated seizures tend to begin later, with cohort medians of 1 versus 16 months respectively. (rinaldi2024gainoffunctionandlossoffunction pages 1-3, okano2023gria3p.met661thrvariant pages 1-3)

There is no validated staging system. The typical course is lifelong developmental impairment with variable evolution of seizures, tone, movement symptoms, behavior, and sleep. Structural brain findings are not necessarily progressive: slight frontal atrophy/ventricular enlargement in one girl had not worsened by age 13. Adult familial cases demonstrate survival into at least the fifth decade, but longitudinal data remain sparse. (philips2014xexomesequencingin pages 4-6, okano2023gria3p.met661thrvariant pages 1-3)

No spontaneous molecular remission is expected. Seizures and psychiatric symptoms can improve with treatment. Early childhood is plausibly a critical intervention period because AMPARs influence neural-circuit development, but no trial has established a disease-specific therapeutic window.

9. Inheritance and population

Epidemiology

No population-based prevalence, incidence, geographic-distribution, or carrier-frequency estimate was identified. Published patients number in the dozens, indicating an ultra-rare disorder, but ascertainment and functional reclassification are still evolving. A prevalence “per 100,000” cannot be responsibly calculated from case reports.

Genetic epidemiology

Pattern: X-linked with sex- and mechanism-dependent expression; “X-linked recessive” describes many familial LoF pedigrees but is incomplete for de novo GoF disease in females. (rinaldi2024gainoffunctionandlossoffunction pages 1-3, hu2026reclassificationofthe pages 1-2)
Sex ratio: Historically strongly male-biased. By 2023, only five affected females had been highlighted in one review of approximately 20 reported variants; newer cohorts establish female disease more firmly. (okano2023gria3p.met661thrvariant pages 1-3)
Penetrance: Apparently high in hemizygous males carrying clearly pathogenic alleles, but exact penetrance is unknown. Heterozygous female penetrance is variable, likely influenced by variant mechanism and X inactivation.
Expressivity: Markedly variable, ranging from moderate ID and sleep disturbance to profound developmental and epileptic encephalopathy.
Anticipation: Not reported; no repeat expansion is involved.
Mosaicism/germline mosaicism: Theoretically possible for de novo variants, but no quantified recurrence risk or proven recurrent germline mosaicism was identified.
Founder effect/consanguinity: No established founder allele; consanguinity is not a characteristic risk because the disorder is X-linked.
Ethnicity/geography: Families have been reported from multiple populations, including Chinese, Japanese, Finnish, and Italian cohorts, without demonstrated population enrichment. (rinaldi2022myoclonicstatusepilepticus pages 1-2, philips2014xexomesequencingin pages 4-6, jiang2023geneticanalysisand pages 1-2, okano2023gria3p.met661thrvariant pages 1-3)

10. Diagnostics

Clinical evaluation

There are no disease-specific consensus clinical criteria. Suspicion should arise in a child—especially a boy—with unexplained developmental delay/ID plus epilepsy, hypotonia or hypertonia, myoclonus/hyperekplexia, disturbed sleep, autism/aggression, or an X-linked family history.

Recommended phenotyping includes neurologic and developmental examination, standardized cognitive/adaptive assessment, speech-language evaluation, movement-disorder assessment, sleep history, hearing/vision assessment, and psychiatric/behavioral review. EEG is indicated for seizures or episodic events. Brain MRI may identify cerebellar hypoplasia, cerebral/frontal atrophy, or ventriculomegaly but is not a molecular biomarker. (rinaldi2022myoclonicstatusepilepticus pages 1-2, okano2023gria3p.met661thrvariant pages 1-3)

No diagnostic blood chemistry, enzyme assay, metabolite, protein biomarker, biopsy, EMG pattern, or histopathologic criterion is established.

Genetic testing strategy

First-line: trio WES or WGS with single-nucleotide, indel, and copy-number calling; alternatively, a comprehensive neurodevelopmental/epilepsy panel including GRIA3.
Confirm: Sanger confirmation and family segregation analysis.
CNV-sensitive testing: exon-level deletion/duplication analysis, MLPA/qPCR, read-depth CNV calling, or chromosomal microarray. Standard exome SNV analysis can miss multi-exon deletions. The Chinese exon 5–12 deletion was identified only after targeted comprehensive testing following unrevealing SNV/indel analysis. (jiang2023geneticanalysisand pages 1-2)
RNA studies: patient RNA, RT-PCR, or a minigene assay can resolve splice VUS; c.268+1G>C was upgraded after demonstration of exon-2 skipping. (hu2026reclassificationofthe pages 4-5, hu2026reclassificationofthe pages 1-2)
Functional electrophysiology: useful in research/advanced diagnostics for missense VUS because LoF, GoF, and apparently neutral variants coexist. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)
CMA/karyotype/FISH: appropriate when a large Xq25 rearrangement is suspected or exome/genome analysis indicates a structural lesion.
Not routinely relevant: mitochondrial sequencing and repeat-expansion testing unless the broader differential diagnosis warrants them.

The p.Met661Thr case illustrates a typical workflow: microarray was negative, trio WES detected a de novo heterozygous variant, population databases were negative, and ACMG evidence supported likely pathogenicity. (okano2023gria3p.met661thrvariant pages 1-3)

Differential diagnosis

Important alternatives include other GRIA-related disorders (GRIA1, GRIA2, GRIA4), NMDA-receptor disorders, DLG3-related XLID, creatine-transporter deficiency, fragile X syndrome, MECP2-related disease, FOXG1 syndrome, STXBP1/SCN2A-related developmental epileptic encephalopathy, and other X-linked ID genes. Distinguishing evidence is a pathogenic GRIA3 variant with segregation and, for missense variants, compatible functional data.

Screening

GRIA3 disease is not included in routine newborn biochemical screening. Cascade testing of at-risk maternal relatives is appropriate after identifying a familial allele. Carrier, prenatal, and preimplantation genetic testing are technically feasible. Amniotic-fluid testing successfully detected the familial exon 5–12 deletion in one fetus. (jiang2023geneticanalysisand pages 1-2)

11. Outcome and prognosis

No survival curve, standardized mortality rate, or life-expectancy estimate exists. Adult affected males aged 35–57 years were described in a Finnish family, showing that survival into later adulthood is possible, but this does not establish normal life expectancy. (philips2014xexomesequencingin pages 4-6)

The major morbidity is lifelong neurodevelopmental disability. Severe cases may remain nonverbal or bedridden and develop orthopedic complications. Epilepsy may be drug-resistant, although control can improve over time; psychiatric and sleep symptoms can require long-term treatment. (hu2026reclassificationofthe pages 4-5, okano2023gria3p.met661thrvariant pages 1-3)

Potential prognostic indicators are functional variant class and sex: GoF correlates with earlier seizures, hypertonia, movement disorders, and greater severity; LoF correlates with later seizures, hypotonia, and sleep disturbance. These are cohort-level associations, not deterministic predictions for an individual. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)

No validated molecular prognostic biomarker or quality-of-life instrument has been developed. Recovery of established intellectual disability has not been demonstrated; functional gains are expected mainly through developmental therapies and control of seizures, tone, sleep, and behavior.

12. Treatment

There is no approved GRIA3 disease-modifying therapy and no disease-specific randomized trial was identified. Management is multidisciplinary and phenotype-directed.

Pharmacotherapy

Epilepsy: standard antiseizure treatment guided by seizure type and EEG. In the p.Met661Thr girl, carbamazepine and ethosuximide were ineffective, while lamotrigine, clobazam, levetiracetam, and lacosamide gradually improved control. (okano2023gria3p.met661thrvariant pages 1-3)
Mechanism-informed GoF treatment: in one boy with p.Ala615Val GoF, carbamazepine—described by the authors as suppressing presynaptic glutamate release—ameliorated both seizures and hypertonia. This is a single case, not evidence for universal efficacy, and contrasts with carbamazepine failure in another unfunctionally characterized allele. (okano2023gria3p.met661thrvariant pages 1-3, hamanaka2022ameliorationofa pages 1-2)
Psychiatric/sleep symptoms: risperidone and clozapine reportedly improved psychiatric manifestations, and lorazepam improved sleep in one family. These observations are uncontrolled. (hu2026reclassificationofthe pages 4-5)
AMPAR modulators: positive modulators and antagonists normalized selected variant currents in experimental assays, but no compound has established clinical efficacy in XLID94. Variant direction must be known because enhancing a GoF receptor or inhibiting a LoF receptor could be harmful. (xiangwei2023clinicalandfunctional pages 1-6)

Suggested NCIt concepts include Anticonvulsant Therapy, Carbamazepine, Levetiracetam, Lamotrigine, Clobazam, Lacosamide, Antipsychotic Agent, Physical Therapy, Occupational Therapy, Speech and Language Therapy, and Genetic Counseling. Exact NCIt numerical codes should be verified directly before database ingestion.

Supportive and rehabilitative care

Early-intervention services, individualized education, speech/augmentative communication therapy, occupational and physical therapy, tone management, mobility equipment, orthopedic surveillance, behavioral therapy, sleep intervention, nutritional assessment, and caregiver support are appropriate. Epilepsy rescue planning and sudden-death risk counseling should follow general epilepsy standards.

There is no established role for surgery except treatment of complications such as hip dislocation or scoliosis. No gene replacement, CRISPR, antisense, cell therapy, RNA therapy, immunotherapy, or pharmacogenomic guideline is available for GRIA3 disease.

13. Prevention

The causal germline variant cannot be prevented by lifestyle modification, vaccination, or exposure avoidance.

Primary prevention: genetic counseling and reproductive options for known carrier families, including preimplantation genetic testing, chorionic-villus sampling, amniocentesis, or use of donor gametes.
Secondary prevention: prompt genetic diagnosis, cascade testing, early developmental intervention, and surveillance for epilepsy, movement disorder, sleep disturbance, and behavioral illness.
Tertiary prevention: seizure control, aspiration and injury prevention, contracture/orthopedic management, communication support, and caregiver education.

For a carrier mother, each pregnancy has a 50% probability of transmitting the variant; expected clinical consequences depend on fetal sex, variant mechanism, and—among females—X inactivation. A de novo result lowers but does not eliminate recurrence because parental germline mosaicism cannot be excluded. The 2023 family report demonstrates technical feasibility of prenatal detection but should not be treated as a population-screening recommendation. (jiang2023geneticanalysisand pages 1-2)

No vaccine, prophylactic drug, public-health sanitation measure, or environmental intervention is disease-specific.

14. Other species and natural disease

Mouse: Mus musculus, NCBI Taxonomy 10090; ortholog Gria3.
Fruit fly: Drosophila melanogaster, NCBI Taxonomy 7227; used as a transgenic expression system for human mutant GluA3.
Human: Homo sapiens, NCBI Taxonomy 9606.

No naturally occurring veterinary disease equivalent was identified in companion animals, livestock, or wildlife. There is no transmission or zoonotic potential. Comparative relevance derives from evolutionary conservation of AMPAR channel architecture and synaptic function rather than natural cross-species disease.

15. Model organisms and experimental systems

Mouse models

Gria3 knockout mice: Germline hemizygous knockout mice showed increased aggression, sociality, peripheral activity, minor motor/balance deficits, elevated striatal dopamine, and reduced olfactory-bulb serotonin turnover. They did not reproduce the profound human intellectual disability phenotype, limiting face validity, but support roles in behavior, motor control, and monoaminergic circuitry. (adamczyk2012glua3deficiencyinmice pages 1-3)
p.Ala653Thr CRISPR knock-in: Reproduced altered sleep/activity architecture and enhanced light-induced period lengthening, providing unusually strong allele-specific human–mouse concordance for sleep regulation. (davies2017apointmutation pages 1-2)
Protein-truncating Gria3 model: Multi-region RNA-seq and synaptic proteomics revealed age- and region-dependent activity-regulated, glial, immune, oligodendrocyte, and synaptic changes. Because this was a 2024 bioRxiv preprint and modeled a schizophrenia-associated PTV, extrapolation to XLID94 should remain cautious. (huang2024brainregionspecificchangesand pages 1-3)

Cellular and invertebrate systems

HEK293/heterologous cells and Xenopus oocytes: Used for patch clamp or voltage clamp to measure current amplitude, agonist potency, desensitization, deactivation, and pharmacologic rescue. These systems define LoF versus GoF but lack native neuronal development and circuit context. (xiangwei2023clinicalandfunctional pages 1-6, hamanaka2022ameliorationofa pages 1-2)
Minigene assay: HEK293T testing demonstrated exon-2 skipping from c.268+1G>C. It validates aberrant splicing but not tissue-specific transcript abundance. (hu2026reclassificationofthe pages 4-5)
Drosophila transgenics: Co-expression of p.Ala615Val with the leaky Lurcher alteration produced developmental defects, supporting GoF interaction. Species and receptor-composition differences limit direct clinical translation. (hamanaka2022ameliorationofa pages 1-2)
Mouse hippocampal interaction proteomics: Defined GluA2/3-associated CNIH2, TARP-γ2, and OLFM1 complexes and provides a resource for studying trafficking/gating modifiers. (spek2022expressionandinteraction pages 1-2)

No patient-derived iPSC neuron, brain organoid, rat, zebrafish, or C. elegans XLID94 model was identified in the retrieved evidence. Such models would be valuable for developmental timing, cell-type specificity, X-inactivation in females, and allele-specific drug screening.

Recent developments and expert interpretation

The decisive recent advance is the online-December-2023/2024-volume Brain study demonstrating that GRIA3 disease is not a unitary haploinsufficiency syndrome. Its abstract states: “Thirty-one variants alter receptor function and show loss-of-function (LoF) or gain-of-function (GoF) properties, whereas 13 appeared neutral.” It further reports that “GoF variants were associated with more severe outcomes,” with median seizure onset at one month versus 16 months for LoF. This functional taxonomy should now guide variant interpretation, prognosis, and any future precision therapy. (rinaldi2024gainoffunctionandlossoffunction pages 1-3)

A second advance is recognition of affected females. The 2023 p.Met661Thr report states: “Here, we report a female patient with developmental and epileptic encephalopathy who carries the novel de novo GRIA3 variant.” Together with the multicenter cohort, this argues against excluding GRIA3 because the patient is female. (okano2023gria3p.met661thrvariant pages 1-3)

A third advance is preliminary precision pharmacology. Hamanaka and colleagues concluded that “drugs suppressing glutamatergic neurotransmission may ameliorate this phenotype” after carbamazepine improved a GoF case. This is biologically coherent but remains an N-of-1 observation, and the contrasting failure of carbamazepine in another patient demonstrates that treatment cannot yet be generalized without variant-level functional evidence. (okano2023gria3p.met661thrvariant pages 1-3, hamanaka2022ameliorationofa pages 1-2)

Finally, 2024 mouse multi-omics suggests that primary AMPAR dysfunction generates broader, brain-region-specific neuronal and glial adaptations. This is hypothesis-generating rather than clinically validated because the study was not peer reviewed and did not directly model every XLID94 allele. (huang2024brainregionspecificchangesand pages 1-3)

Evidence limitations

The evidence base remains small and vulnerable to referral, publication, and ascertainment bias. Phenotype frequencies come from 25 patients, standardized natural-history and quality-of-life studies are absent, and many alleles lack electrophysiologic validation. No prevalence, mortality, penetrance, carrier-frequency, formal diagnostic guideline, randomized treatment trial, or approved targeted therapy is available. PMIDs were not present in the retrieved full-text metadata; therefore, DOI URLs and publication dates are supplied rather than risking incorrect PMID assignment. The 2012 article proposing GRIA3 silencing through an upstream noncoding duplication was explicitly retrieved as retracted and was not used as affirmative evidence.

References

(rinaldi2024gainoffunctionandlossoffunction pages 1-3): Berardo Rinaldi, Allan Bayat, Linda G Zachariassen, Jia-Hui Sun, Yu-Han Ge, Dan Zhao, Kristine Bonde, Laura H Madsen, Ilham Abdimunim Ali Awad, Duygu Bagiran, Amal Sbeih, Syeda Maidah Shah, Shaymaa El-Sayed, Signe M Lyngby, Miriam G Pedersen, Charlotte Stenum-Berg, Louise Claudia Walker, Ilona Krey, Andrée Delahaye-Duriez, Lisa T Emrick, Krystal Sully, Chaya N Murali, Lindsay C Burrage, Julie Ana Plaud Gonzalez, Mered Parnes, Jennifer Friedman, Bertrand Isidor, Jérémie Lefranc, Sylvia Redon, Delphine Heron, Cyril Mignot, Boris Keren, Mélanie Fradin, Christele Dubourg, Sandra Mercier, Thomas Besnard, Benjamin Cogne, Wallid Deb, Clotilde Rivier, Donatella Milani, Maria Francesca Bedeschi, Claudia Di Napoli, Federico Grilli, Paola Marchisio, Suzanna Koudijs, Danielle Veenma, Emanuela Argilli, Sally Ann Lynch, Ping Yee Billie Au, Fernando Eduardo Ayala Valenzuela, Carolyn Brown, Diane Masser-Frye, Marilyn Jones, Leslie Patron Romero, Wenhui Laura Li, Erin Thorpe, Laura Hecher, Jessika Johannsen, Jonas Denecke, Vanda McNiven, Anna Szuto, Emma Wakeling, Vincent Cruz, Valerie Sency, Heng Wang, Juliette Piard, Fanny Kortüm, Theresia Herget, Tatjana Bierhals, Angelo Condell, Bruria Ben Zeev, Simranpreet Kaur, John Christodoulou, Amelie Piton, Christiane Gertrud Zweier, Cornelia Kraus, Alessia Micalizzi, Marina Trivisano, Nicola Specchio, Gaetan Lesca, Rikke S Møller, Zeynep Tümer, Maria Musgaard, Benedicte Gerard, Johannes R Lemke, Yun Stone Shi, and Anders S Kristensen. Gain-of-function and loss-of-function variants in gria3 lead to distinct neurodevelopmental phenotypes. Brain : a journal of neurology, Dec 2024. URL: https://doi.org/10.1093/brain/awad403, doi:10.1093/brain/awad403. This article has 40 citations.
(jiang2023geneticanalysisand pages 1-2): Yanting Jiang. Genetic analysis and prenatal diagnosis of a chinese pedigree affected with syndromic x-linked intellectual disability 94 due to exon 5-12 deletion in gria3 gene. Sep 2023. URL: https://doi.org/10.26717/bjstr.2023.52.008322, doi:10.26717/bjstr.2023.52.008322. This article has 0 citations.
(okano2023gria3p.met661thrvariant pages 1-3): Satomi Okano, Yoshio Makita, Akie Miyamoto, Genya Taketazu, Kayano Kimura, Ikue Fukuda, Hajime Tanaka, Kumiko Yanagi, and Tadashi Kaname. Gria3 p.met661thr variant in a female with developmental epileptic encephalopathy. Human Genome Variation, Feb 2023. URL: https://doi.org/10.1038/s41439-023-00232-1, doi:10.1038/s41439-023-00232-1. This article has 10 citations.
(hamanaka2022ameliorationofa pages 1-2): Kohei Hamanaka, Keita Miyoshi, Jia-Hui Sun, Keisuke Hamada, Takao Komatsubara, Ken Saida, Naomi Tsuchida, Yuri Uchiyama, Atsushi Fujita, Takeshi Mizuguchi, Benedicte Gerard, Allan Bayat, Berardo Rinaldi, Mitsuhiro Kato, Jun Tohyama, Kazuhiro Ogata, Yun Stone Shi, Kuniaki Saito, Satoko Miyatake, and Naomichi Matsumoto. Amelioration of a neurodevelopmental disorder by carbamazepine in a case having a gain-of-function gria3 variant. Human Genetics, 141:283-293, Jan 2022. URL: https://doi.org/10.1007/s00439-021-02416-7, doi:10.1007/s00439-021-02416-7. This article has 14 citations and is from a peer-reviewed journal.
(davies2017apointmutation pages 1-2): Benjamin Davies, Laurence A Brown, Ondrej Cais, Jake Watson, Amber J Clayton, Veronica T Chang, Daniel Biggs, Christopher Preece, Polinka Hernandez-Pliego, Jon Krohn, Amarjit Bhomra, Stephen R F Twigg, Andrew Rimmer, Alexander Kanapin, Arjune Sen, Zenobia Zaiwalla, Gil McVean, Russell Foster, Peter Donnelly, Jenny C Taylor, Edward Blair, David Nutt, A Radu Aricescu, Ingo H Greger, Stuart N Peirson, Jonathan Flint, and Hilary C Martin. A point mutation in the ion conduction pore of ampa receptor gria3 causes dramatically perturbed sleep patterns as well as intellectual disability. Human Molecular Genetics, 26:3869-3882, Jul 2017. URL: https://doi.org/10.1093/hmg/ddx270, doi:10.1093/hmg/ddx270. This article has 66 citations and is from a domain leading peer-reviewed journal.
(adamczyk2012glua3deficiencyinmice pages 1-3): Abby Adamczyk, Rebeca Mejias, Kogo Takamiya, Jennifer Yocum, Irina N. Krasnova, Juan Calderon, Jean Lud Cadet, Richard L. Huganir, Mikhail V. Pletnikov, and Tao Wang. Glua3-deficiency in mice is associated with increased social and aggressive behavior and elevated dopamine in striatum. Behavioural Brain Research, 229:265-272, Apr 2012. URL: https://doi.org/10.1016/j.bbr.2012.01.007, doi:10.1016/j.bbr.2012.01.007. This article has 96 citations and is from a peer-reviewed journal.
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(hu2026reclassificationofthe pages 1-2): Lina Hu, Yuqiong Chai, Xiaofei Liu, Yanan Wang, and Hongwei Jiang. Reclassification of the gria3 splice-site variant in an x-linked family with intellectual disability and psychiatric symptoms. Frontiers in Genetics, Aug 2026. URL: https://doi.org/10.3389/fgene.2026.1914453, doi:10.3389/fgene.2026.1914453. This article has 0 citations and is from a peer-reviewed journal.
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(philips2014xexomesequencingin pages 4-6): Anju K Philips, Auli Sirén, Kristiina Avela, Mirja Somer, Maarit Peippo, Minna Ahvenainen, Fatma Doagu, Maria Arvio, Helena Kääriäinen, Hilde Van Esch, Guy Froyen, Stefan A Haas, Hao Hu, Vera M Kalscheuer, and Irma Järvelä. X-exome sequencing in finnish families with intellectual disability - four novel mutations and two novel syndromic phenotypes. Orphanet Journal of Rare Diseases, 9:49-49, Apr 2014. URL: https://doi.org/10.1186/1750-1172-9-49, doi:10.1186/1750-1172-9-49. This article has 102 citations and is from a peer-reviewed journal.
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(xiangwei2023clinicalandfunctional pages 1-6): Wenshu XiangWei, Riley E. Perszyk, Nana Liu, Yuchen Xu, Subhrajit Bhattacharya, Gil H. Shaulsky, Constance Smith-Hicks, Ali Fatemi, Andrew E. Fry, Kate Chandler, Tao Wang, Julie Vogt, Julie S. Cohen, Alex R. Paciorkowski, Annapurna Poduri, Yuehua Zhang, Shuang Wang, Yuping Wang, Qiongxiang Zhai, Fang Fang, Jie Leng, Kathryn Garber, Scott J. Myers, Robin-Tobias Jauss, Kristen L. Park, Timothy A. Benke, Johannes R. Lemke, Hongjie Yuan, Yuwu Jiang, and Stephen F. Traynelis. Clinical and functional consequences of gria variants in patients with neurological diseases. Cellular and Molecular Life Sciences, Nov 2023. URL: https://doi.org/10.1007/s00018-023-04991-6, doi:10.1007/s00018-023-04991-6. This article has 22 citations and is from a domain leading peer-reviewed journal.

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References weighed for topical relevance	14
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Syndromic X-linked intellectual disability 94: disease-characteristics report

Executive summary and scope

1. Disease information

Definition

Identifiers and nomenclature

2. Etiology

Causal factors and genetic risk

Environmental, lifestyle, infectious, and protective factors

3. Phenotypes

4. Genetic and molecular information

5. Environmental information

6. Mechanism and pathophysiology

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7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

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10. Diagnostics

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Genetic testing strategy

Differential diagnosis

Screening

11. Outcome and prognosis

12. Treatment

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