Drosophila has several genes for gap junction proteins

The Innexin gene family forms gap junctions in invertebrates. Many genes in this family have been identified in Caenorhabditis elegans, but only two in Drosophila. We have used PCR techniques to identify three new members of this family from Drosophila. These are designated pas-related proteins (prp) 6, 7, and 33. The putative proteins coded by these new genes show 25-35% identity and 39-66% similarity to other Drosophila innexins and share a similar hydrophobicity profile. The genes form two small clusters on the X-chromosome, with three of the genes sitting within 10kb of each other. The closeness in sequence and location suggests an evolutionary origin of these genes via local duplication. In situ hybridization shows expression in the CNS, gut and epidermis. Each gene has a distinct pattern of expression in different tissues at different developmental times. However, parts of the expression patterns overlap, especially for prp33 and ogre which may be expressed from the same transcriptional enhancers. This suggest that the Prp33 and Ogre proteins may join in forming heteromeric gap junction channels.