GLIOTACTIN, A NOVEL TRANSMEMBRANE PROTEIN ON PERIPHERAL GLIA, IS REQUIRED TO FORM THE BLOOD-NERVE BARRIER IN DROSOPHILA

Peripheral glia help ensure that motor and sensory axons are bathed in the appropriate ionic and biochemical environment. In Drosophila, per ipheral glia help shield these axons against the high K+ concentration of the hemolymph, which would largely abolish their excitability. Her e, we describe the molecular genetic analysis of gliotactin, a novel t ransmembrane protein that is transiently expressed on peripheral glia and that is required for the formation of the peripheral blood-nerve b arrier, In gliotactin mutant embryos, the peripheral glia develop norm ally in many respects, except that ultrastructurally and physiological ly they do not form a complete blood-nerve barrier. As a result, perip heral motor axons are exposed to the high K+ hemolymph, action potenti als fail to propagate, and the embryos are nearly paralyzed.