CHAT (choline O-acetyltransferase) is the biosynthetic enzyme catalyzing the synthesis of acetylcholine (ACh) from acetyl-CoA and choline at cholinergic synapses 1. This enzyme is essential for neurotransmission in both central and peripheral nervous systems, with particularly high expression in brainstem regions like the dorsal motor nucleus of the vagus 2. In the myenteric plexus, ChAT-positive neurons comprise 38-52% of neurons depending on intestinal region, often co-existing or co-absent with nitric oxide synthase in distinct neuronal populations 3. ChAT dysfunction is associated with congenital myasthenic syndrome type 6, a presynaptic disorder 4. Clinically, ChAT has emerged as a therapeutic target in Alzheimer's disease, where cholinergic system degeneration contributes to cognitive decline 4. Neural stem cells overexpressing ChAT improved learning and memory in AD model mice by increasing acetylcholine levels, reducing amyloid-β deposits, and promoting neuroregeneration 4. Additionally, CHAT genetic variants (rs1258267) show population-specific associations with primary angle-closure glaucoma risk, with decreased risk in Asian populations 5. Altered cholinergic regulation involving ChAT has also been implicated in sudden infant death syndrome neuropathology, with reduced ChAT expression observed in vulnerable brainstem regions 2.