REPO ENCODES A GLIAL-SPECIFIC HOMEO DOMAIN PROTEIN REQUIRED IN THE DROSOPHILA NERVOUS-SYSTEM

We report the identification of a Drosophila locus, reversed polarity (repo). Weak repo alleles were viable but affected glia in the optic l obe, resulting in a reversal in polarity of the electrophysiological r esponse to light in the adult. Strong repo alleles caused defects in e mbryonic glia and resulted in embryonic lethality. Expression of repo appeared to be specific to glia throughout development. In the adult v isual system, repo was expressed in laminal glia, medullar glia, and s ubretinal cells; in the embryo, repo was expressed in nearly all of th e identified glia in the central and peripheral nervous systems except midline glia. The repo gene encoded a homeo domain protein suggesting that it might be a transcriptional regulator of genes required for gl ial development.