A DROSOPHILA CALCIUM-CHANNEL ALPHA-1 SUBUNIT GENE MAPS TO A GENETIC-LOCUS ASSOCIATED WITH BEHAVIORAL AND VISUAL DEFECTS

We have cloned cDNAs that encode a complete open reading frame for a c alcium channel alpha 1 subunit from Drosophila melanogaster. The deduc ed 1851 amino acid protein belongs to the superfamily of voltage-gated sodium and calcium channels. Phylogenetic analysis shows that the seq uence of this subunit is relatively distant from sodium channel alpha subunits and most similar to genes encoding the A, B, and E isoforms o f calcium channel alpha 1 subunits. To indicate its similarity to this subfamily of vertebrate isoforms, we name this protein Dmca1A, for Dr osophila melanogaster calcium channel alpha 1 subunit, type A. Norther n blot analysis detected a single 10.5 kb transcript class that is reg ulated developmentally, with expression peaks in the first larval inst ar, midpupal, and late pupal stages. In late-stage embryos, Dmca1A is expressed preferentially in the nervous system. Variant transcripts ar e generated by alternative splicing. In addition, single nucleotide va riations between cDNAs and genomic sequence are consistent with RNA ed iting. Dmca1A maps to a chromosomal region implicated in, and is the l ikely candidate for, the gene involved in the generation of behavioral , physiological, and lethal phenotypes of the cacophony, nightblind-A, and lethal(1)L13 mutants.