GRIN3B encodes the NR3B subunit of NMDA receptors, which forms non-conventional glutamate-gated ion channels with distinctive properties including low calcium permeability and reduced voltage-dependent magnesium block 1. The protein functions as a component of heterotetrameric receptor complexes, forming both glutamatergic receptors with GluN1 and GluN2 subunits and excitatory glycinergic receptors with GluN1 alone, with glycine and D-serine serving as ligands. GRIN3B shows motoneuron-specific expression and may protect against glutamate-mediated excitotoxicity by reducing calcium permeability 1. The gene exhibits a common null allele variant (insCGTT) with global distribution and frequencies ranging 0-0.38, suggesting evolutionary significance 1. GRIN3B has emerged as a potential biomarker in neuropsychiatric disorders, with blood mRNA levels associated with PTSD symptom trajectories and genetic variants linked to mismatch negativity in schizophrenia 23. The gene shows dysregulated expression in neurodegenerative diseases, with altered RNA editing patterns in Alzheimer's disease brains and reduced expression in Down syndrome neural cells, accompanied by impaired neuronal activity 45. However, genetic association studies have not consistently linked GRIN3B variants to ALS or Alzheimer's disease risk 16.