ChAT, or choline acetyltransferase, is an enzyme involved in the synthesis of the neurotransmitter acetylcholine. In humans, it is encoded by the gene, CHAT, to produce a 748-aa canonical protein with a mass of 82.5 kDa. There are two other alternatively spliced isoforms. It is highly expressed in the axons of cholinergic neurons, and is often used as a neuronal antibody marker. ChAT expression is implicated in Alzheimer’s disease and amyotrophic lateral sclerosis (ALS). Other names include CHOACTase, choline acetylase, choline O-acetyltransferase, and CAT.