NOS1 encodes neuronal nitric oxide synthase (nNOS), the predominant nitric oxide (NO)-producing enzyme in the brain that catalyzes L-arginine to generate NO, functioning as a neurotransmitter with diverse signaling roles 1. NOS1 mediates multiple neuronal functions including learning, memory development, synaptic plasticity, and neuronal development through both canonical NO signaling and non-canonical roles such as cysteine S-nitrosylation of target proteins 1. The enzyme is transiently expressed by gonadotropin-releasing hormone (GnRH) neurons and critically regulates reproductive development; NOS1 loss-of-function mutations cause congenital hypogonadotropic hypogonadism with associated anosmia, hearing loss, and intellectual disability, reversible by nitric oxide treatment during minipuberty 2. In cardiac tissue, NOS1 translocates to the sarcolemma in ischemic cardiomyopathy and maintains myocardial homeostasis; BAT-derived lipokine 12,13-diHOME enhances cardiac function via NOS1-dependent calcium cycling regulation 34. Genetically, NOS1 polymorphisms associate with psychiatric disorders: the rs3782206 variant confers schizophrenia risk in Asian populations, while nNOS in ErbB4-positive GABAergic interneurons regulates hippocampal GABA transmission, with nNOS deletion inducing schizophrenia-relevant behavioral deficits 56. NOS1 exon18 polymorphism shows association with Parkinson's disease risk 7. Reduced prefrontal NO signaling, determined by NOS1 genetic variants, associates with cognitive and neuropsychiatric symptoms 8.