Defective glia induce neuronal apoptosis in the repo visual system of Drosophila.

The role of glia in suppressing neuronal cell death was investigated in the visual system of the Drosophila mutant, reversed polarity (repo). The repo locus encodes a glial-specific homeodomain protein expressed in the optic lobes. Here, we show that survival of the laminar neurons in the optic lobe depends on repo expression in the laminar glia, indicating that the laminar glia supply factors required for neuronal survival. The repo glia also underwent cell death, suggesting that the laminar neurons are required for survival of the glia or that repo expression is required to suppress an intrinsic cell suicide program. Subsequent to the laminar cell death, the retinal cells in the repo visual system also degenerated, indicating that the retinal cell death was due to retrograde degeneration.