GRIN3B
Chr 19glutamate ionotropic receptor NMDA type subunit 3B
Also known as: GluN3B, NR3B
GRIN3B encodes the GluN3B subunit of NMDA receptors, which forms excitatory glycine receptor complexes with GluN1 and modulates glutamatergic signaling with low calcium permeability and reduced magnesium block. The gene shows minimal constraint against loss-of-function variants (pLI near 0, LOEUF 0.98), and while genetic variations have been proposed to associate with schizophrenia, definitive Mendelian disease associations and inheritance patterns have not been established. The protein is primarily expressed in motor neurons where it contributes to excitatory neurotransmission through both glycinergic and glutamatergic pathways.
Population Genetics & Constraint
gnomAD v4 — loss-of-function & missense intolerance
Typical tolerance to LoF variation
Tolerant to missense variation
This gene has evidence for multiple mechanisms of pathogenicity (gain-of-function and dominant-negative). Both the Badonyi & Marsh prediction and the broader genomic evidence point to gain-of-function as the predominant mechanism. Different variants in this gene may act through different mechanisms — interpret in context of the specific variant.
Note: In-silico variant effect predictors (SIFT, PolyPhen, REVEL, CADD) may underestimate pathogenicity of missense variants in genes with GOF or DN mechanisms. Consider functional evidence and clinical context.
Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312.
ClinVar Variant Classifications
310 submitted variants in ClinVar
Classification Summary
Curated Variants Distribution
Classified variants from ClinVar · 5 ACMG categories
| Classification | LoF | Missense + Inframe | Non-coding | Synonymous | Total |
|---|---|---|---|---|---|
Pathogenic | 0 | 0 | 27 | 0 | 27 |
Likely Pathogenic | 0 | 0 | 4 | 0 | 4 |
VUS | 0 | 244 | 9 | 0 | 253 |
Likely Benign | 0 | 5 | 1 | 4 | 10 |
Benign | 0 | 4 | 2 | 2 | 8 |
Conflicting | — | 1 | |||
| Total | 0 | 253 | 43 | 6 | 303 |
LoF = frameshift, stop gained/lost, canonical splice · Counts from ClinVar esearch · Updated hourly
View in ClinVar →Protein Context — Lollipop Plot
GRIN3B · protein map & ClinVar variants
Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.
External Resources
Links to major genomics databases and tools
Clinical Trials
Active and recruiting trials from ClinicalTrials.gov
No active trials found for this gene.
Search ClinicalTrials.gov →External Resources
Links to major genomics databases and tools