Dpp and Hedgehog mediate neuron-glia interactions in Drosophila eye development by promoting the proliferation and motility of subretinal glia

Neuron-glia interactions are crucial for the establishment of normal connec tivity in the nervous system during development, but the molecular signals involved in these interactions are largely unknown. Here we show that diffe rentiating photoreceptors in the developing Drosophila eye influence the pr oliferative and migratory behavior of the subretinal glia through the diffu sible factors Decapentaplegic (Dpp) and Hedgehog (Hh). We demonstrate that proliferation and migration of the glia are separable processes, and that D pp promotes both the proliferation and motility of the glia, whereas Hh app ears to promote only their motility; neither specifies the direction of mig ration. We present evidence that Dpp and Hh act on the glia in parallel and through the regulation of transcription. Finally, we show that ectopic mig ration of subretinal glia can result in the ectopic projection of photorece ptor axons. Our study suggests a novel function for Hh in regulating migrat ory behavior and provides further evidence for a complex mutual dependence between glial and neuronal cells during development. (C) 2001 Elsevier Scie nce Ireland Ltd. All rights reserved.