THE ACTIVE MIGRATION OF DROSOPHILA PRIMORDIAL GERM-CELLS

We describe our analysis of primordial germ cell migration in Drosophi la wild-type and mutant embryos using high resolution microscopy and p rimary culture in vitro, During migratory events the germ cells form t ransient interactions with each other and surrounding somatic cells. B oth in vivo and in vitro they extend pseudopodia and the accompanying changes in the cytoskeleton suggest that actin polymerization drives t hese movements. These cellular events occur from the end of the blasto derm stage and are regulated by environmental cues. We show that the v ital transepithelial migration allowing exit from the gut primordium a nd passage into the interior of the embryo is facilitated by changes i n the structure of this epithelium. Migrating germ cells extend proces ses in different directions. This phenomenon also occurs in primary cu lture where the cells move in an unoriented fashion at substratum conc entration-dependent rates. In vivo this migration is oriented leading germ cells to the gonadal mesoderm. We suggest that this guidance invo lves stabilization of states of an intrinsic cellular oscillator resul ting in cell polarization and oriented movement.