RNA editing in the Drosophila DMCA1A calcium-channel alpha 1 subunit transcript.

Messenger RNA editing of transcripts encoding voltage-sensitive ion channels has not been extensively analyzed--least of all in Drosophila, for which several channel-encoding genes are known. Previous sequence studies of D. melanogaster's cacophony gene, which encodes an alpha 1 calcium-channel subunit called Dmca1A, suggested that several nucleotides within the ORF of the primary transcript are edited such that "A-to-G" substitutions occur (these two nucleotides being the adenine that is found at the relevant sites in the sense strand of genomic DNA or the primary transcript, compared to the substitution of guanine that is detected at the level of cDNA analysis). Such A-to-G changes are the same kind of post-transcriptional variations originally discovered--in a neurobiological context--for a ligand-sensitive channel in vertebrates. Here, we extracted RNA from adult flies and revealed, by RT-PCR and restriction-enzyme analyses, that transcript heterogeneity exists in vivo for three distinct edited sites within the cac-encoded RNA. Each such nucleotide would lead to channel variability at the level of the Dmca1A polypeptide. Owing to cacophony being originally identified as a "behavioral gene," the possible significance of Dmca1A RNA editing for influencing the relevant neuro-functional phenotypes is discussed.