Glial cell migration in Drosophila

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The formation of the stereotyped axonal network found in many metazoan organisms depends on the intricate interplay of neuronal and glial cells and requires migration of either cell type. In the Drosophila CNS, migration of the midline glial cells is required for the establishment of the segmental commissures. A block in this migration leads to a mutant CNS phenotype which allowed us to conduct a saturating EMS mutagenesis screening for genes required for midline glial cell migration. Mutations in more than 13 genes were identified. Four of them affect EGF receptor signalling which controls differentiation of the midline glia. kette was shown to act in the midline neurons where it affects the formation of axons along which the midline glial cells migrate. Here I purpose two different related projects aimed to understand the molecular mechanisms underlying glial migration in the embryonic nervous system of Drosophila. In the first project we are planing a molecular analysis of the gene schmalspur, which appears to be expressed in the midline glia. Based on the phenotypic analysis and on genetic interactions we observed with the neuronally expressed gene kette, schmalspur is a very promising candidate gene relevant for glial migration. In the second project we want to establish new genetic screening systems aimed to more directly address glial cell migration. We will focus on the analysis of peripheral glial cells in the embryonic as well as in the larval PNS, since only here extensive migrations can be observed. In order to identify the relevant genes we will employ several techniques. We will set up a classical F3 approach and a modified FRT/FLP approach using the recently described MARCM system. Finally, we want to establish a new glial cell specific gene silencing system.