Somatomotor neuron-specific expression of the human cholinergic gene locusin transgenic mice

We examined the expression pattern of the vesicular acetylcholine transport er in the mouse nervous system, using rodent-specific riboprobes and antibo dies, prior to comparing it with the distribution of vesicular acetylcholin e transporter expressed from a human transgene in the mouse, using riboprob es and antibodies specific for human. Endogenous vesicular acetylcholine tr ansporter expression was high in spinal and brainstem somatomotor neurons, vagal visceromotor neurons, and postganglionic parasympathetic neurons, mod erate in basal forebrain and brainstem projection neurons and striatal inte rneurons, and low in intestinal intrinsic neurons. Vesicular acetylcholine transporter expression in intrinsic cortical neurons was restricted to the entorhinal cortex. The sequence of the mouse cholinergic gene locus to 5.1 kb upstream of the start of transcription of the vesicular acetylcholine tr ansporter gene was determined and compared with the corresponding region of the human gene. Cis-regulatory domains implicated previously in human or r at cholinergic gene regulation are highly conserved in mouse, indicating th eir probable relevance to the regulation of the mammalian cholinergic gene locus in vivo. Mouse lines were established containing a human transgene th at included the vesicular acetylcholine transporter gene and sequences span ning 5 kb upstream and 1.8 kb downstream of the vesicular acetylcholine tra nsporter open reading frame. In this transgene, the intact human vesicular acetylcholine transporter was able to act as its own reporter. This allowed elements within the vesicular acetylcholine transporter open reading frame itself, shown previously to affect transcription in vitro, to be assessed in vivo with antibodies and riboprobes that reliably distinguished between human and mouse vesicular acetylcholine transporters and their messenger RN As. Expression of the human vesicular acetylcholine transporter was restric ted to mouse cholinergic somatomotor neurons in the spinal cord and brainst em, but absent from other central and peripheral cholinergic neurons. The mouse appears to be an appropriate model for the study of the genetic r egulation of the cholinergic gene locus, and the physiology and neurochemis try of the mammalian cholinergic nervous system, although differences exist in the distribution of cortical cholinergic neurons between the mouse and other mammals. The somatomotor neuron-specific expression pattern of the tr ansgenic human vesicular acetylcholine transporter suggests a mosaic model for cholinergic gene locus regulation in separate subdivisions of the mamma lian cholinergic nervous system. (C) 2000 IBRO. Published by Elsevier Scien ce Ltd.