A Summary of Early Germ Cell Migration Steps and Genes

<div><p>(A) For each stage, the position of germ cells (yellow) and midgut (red) is indicated. Yellow arrows point in the direction of migration. Note that in wild-type embryos, few germ cells can be observed on the basal side of the midgut anlage (black arrow, stage 7). Genes known for their specific role in germ cell guidance are indicated next to the step where the activity of the respective gene product is needed. In addition to the genes listed, a role for <i>hedgehog</i> has been suggested in germ cell migration (Desphpande et al. 2001); however, the exact step affected is unclear.</p> <p>(B–G) Overexpression of <i>EP1631</i> in germ cells and expression pattern of <i>CG4322</i>. Anterior is to the left in all panels. (B), (C), (F), and (G) are lateral views; (D) and (E) are top views. Wild-type embryos (B and D) and embryos overexpressing <i>EP1631</i> (<i>CG4322</i> GPCR) in germ cells (C and E) were stained with anti-Vasa to mark germ cells. At stage 11 (B and C), germ cells in the wild-type (B) associate with the mesoderm, while germ cells expressing <i>EP1631</i> (<i>CG4322</i> GPCR) using the germ cell-specific <i>nos-GAL4</i> driver are disorganized (C). When the gonads are normally coalescing at stage 13 in wild-type control embryos (D), many germ cells expressing the <i>CG4322</i> GPCR remain lost and are found in ectopic locations (E; arrow points to few germ cells in gonad). (F and G) Expression pattern of <i>CG4322</i> RNA. <i>CG4322</i> RNA is detected in hemocytes (asterisk), in the caudal visceral mesoderm (arrow), and in the PMG at stage 9 (F) and in midgut (arrow) and glial cells (arrowhead) at stage 13 (G).</p>