Acj6: a positive transcriptional regulator of the cholinergic gene locus in Drosophila olfactory neurons. M. Lee , H. Wang , P.M. Salvaterra. Division of Neurosciences, Beckman Research Institute, Duarte, CA.

   We have previously shown that the specification of cholinergic neurons in Drosophila nervous system is accomplished by the action of separate and relatively independent cis regulatory elements located within the 5' flanking DNA of the cholinergic locus (choline acetyltransferase/ vesicular acetylcholine transporter genes,ChAT/VAChT). Nubbin (Pdm1), a POU domain transcription factor appears to be responsible for activating cholinergic gene expression in essential CNS cholinergic neurons. Here, we demonstrate that another Drosophila POU domain protein, Acj6, plays a role in regulation of cholinergic locus expression in some non-essential peripheral sensory neurons. ChAT enzyme activity is significantly reduced in two different acj6 mutant alleles. These mutations are known to affect olfactory behavior and physiology. When we recombine the acj6⁶ null mutant allele with a transgenic line expressing a GFP reporter gene in all cholinergic neurons, the fluorescent signal present in most primary olfactory sensory neurons of the 3^rd antennal segment is almost abolished. In contrast, fluorescence in cholinergic auditory neurons of the 2^nd antennal segment appears unaffected by the acj6⁶ mutation. We also see a reduction in fluorescence in presumed olfactory sensory neurons of embryos and larvae. The 5' flanking DNA of the cholinergic locus contains a number of potential binding sites for Acj6 protein. Electrophoretic gel mobility shift assays using recombinant Acj6 protein confirmed binding to 2 sites. Taken together our results suggest that Acj6 is a positive regulatory factor for expression of the cholinergic gene locus in some types of peripheral sensory neurons. Supported by grants from the NIH, NINDS and the John Douglas French Foundation for Alzheimers Disease Research.