GAD2 encodes glutamate decarboxylase 2 (GAD65), a cytoplasmic enzyme catalyzing GABA synthesis for vesicular release at presynaptic terminals 1. The gene produces multiple alternative transcripts whose expression is regulated by CREB and activity-dependent epigenetic mechanisms 1. GAD2 functions primarily in GABAergic neurotransmission, with dysregulation implicated in multiple neuropsychiatric conditions. In schizophrenia and bipolar disorder, reduced full-length GAD2 transcript expression in the dorsolateral prefrontal cortex correlates with decreased GABA synthesis capacity 2. Increased GAD2 truncated transcripts appear elevated in bipolar disorder but decreased in schizophrenia 2. Autoimmunity targeting GAD65 (the GAD2 protein product) causes diverse CNS hyperexcitability disorders. GAD65 antibodies are biomarkers for limbic encephalitis, epilepsy, cerebellar ataxia, and stiff-person syndrome, with ~70% of affected patients having coexisting autoimmune conditions including type 1 diabetes 3. Approximately 60-80% of stiff-person syndrome patients carry anti-GAD65 antibodies 4. GAD65 autoimmunity in seizure disorders correlates with increased risk for chr10 epilepsy 5. Clinically, immunotherapy responses are variable (~50% improvement) across GAD65-associated neurological phenotypes 3. Emerging evidence suggests GAD2 expression influences cancer cell proliferation through altered GABA signaling 6, though population-based associations with alcoholism remain inconsistent 7.