Fig. 6.

Model showing how wunen activity leads to germ cell-germ cell repulsion. Model depicts germ cells inside the midgut pocket in a stage-10 embryo. Wunen in somatic cells depletes a lipid phosphate attractant (blue circle with P) required for survival, leading to repulsion of germ cells from wunen-expressing somatic cells (a). Germ cells also deplete the lipid phosphate attractant leading to germ cell-germ cell repulsion (b). This leads germ cells to cross the midgut in all directions (c), ensuring that the germ cells become partitioned equally to the embryonic gonads. The extent to which competition between soma and germ cells occurs inside the midgut pocket is uncertain. Germ cells do cross the midgut in wun wun2 zygotic mutants in which the midgut cells would lack wunens, therefore germ cell-germ cell repulsion is sufficient for crossing the midgut.