CHAT (choline acetyltransferase) belongs to the carnitine/choline acetyltransferase family.Choline O-acetyltransferase (ChAT) catalyzes the synthesis of the neurotransmitter acetylcholine (ACh) from acetyl CoA and choline in the central and peripheral nervous system.CHAT is known to to be present exclusively in the cytoplasm of cholinergic neurons and anti-CHAT antibody has been considered as the best marker for cholinergic neurons.