Chat, short for choline acetyltransferase, is a synthesizing enzyme for acetylcholine (ACh), a neurotransmitter crucial for nerve impulse transmission in both the central and peripheral nervous systems [1]. It catalyzes the transfer of an acetyl group from coenzyme acetyl-CoA to choline to yield ACh. ChAT-expressing neurons play significant roles in various neural functions, and the creation of transgenic mouse models like the ChAT-eGFP transgenic mice has provided advantages for studying cholinergic neurons [1].

In the ChAT-eGFP transgenic mouse brain study, while there was a complete overlap between the transgenic expression of eGFP and the immunohistochemical staining in the cholinergic basal forebrain, in other areas such as the cortex, hippocampus, and brainstem, differences in the distribution of ChAT-eGFP expressing neurons and ChAT immunoreactive neurons were observed. This indicates that caution should be exercised when using this transgenic mouse line for studying cholinergic neurons in specific brain regions [1].

In conclusion, Chat is essential for the synthesis of acetylcholine, a key neurotransmitter. The use of transgenic mouse models, like the ChAT-eGFP transgenic mice, has revealed differences in the distribution of ChAT-expressing neurons in different brain regions. This contributes to our understanding of the role of cholinergic neurons in neural functions and could potentially aid in research related to neurological diseases where cholinergic function may be disrupted.