MOLECULAR-CLONING OF A PUTATIVE VESICULAR TRANSPORTER FOR ACETYLCHOLINE

Classical neurotransmitters such as acetylcholine (ACh) require transp ort into synaptic vesicles for regulated exocytotic release. The Caeno rhabditis elegans gene unc-17 encodes a protein with homology to mamma lian transporters that concentrate monoamine neurotransmitters into sy naptic vesicles. Mutations in unc-17 protect against organophosphorus toxicity, indicating a role in cholinergic neurotransmission. Using th e relationship of unc-17 to the vesicular amine transporters, we first isolated a related sequence from the electric ray Torpedo californica [Torpedo vesicular ACh transporter (TorVAChT)] that is expressed by t he electric lobe but not by peripheral tissues. Using the relationship of the Torpedo sequence to unc-17, we then isolated the cDNA for a ra t homologue (rVAChT). Northern blot analysis shows expression of these sequences in the basal forebrain, basal ganglia, and spinal cord but not cerebellum or peripheral tissues. In situ hybridization shows expr ession of rVAChT mRNA in all cholinergic cell groups, including those in the basal forebrain, brainstem, and spinal cord that previously hav e been shown to express choline acetyltransferase mRNA. The human VACh T gene also localizes to chromosome 10 near the gene for choline acety ltransferase. Taken together, these observations support a role for rV AChT in vesicular ACh transport and indicate its potential as a novel marker for cholinergic neurons.