Fig. 7. Slam is hypothesized to deposit a germ cell guidance cue early that will act later in embryogenesis. Slam expression, green; posterior midgut primordium, red; germ cells, yellow; hypothesized guidance cue, blue triangles. (A) Blastoderm embryo, Slam is expressed on the basal-lateral membrane of all cells. A guidance cue (blue triangles) is expressed in the posterior midgut (if not in other cells as well), which is deposited on the basal-lateral membrane by Slam. (B) Gastrulating embryo, Slam expression begins to decrease. (C) Stage 9-10, germ cells are exiting the midgut pocket, moving from the apical to the basal side of the midgut cells. Slam protein is no longer present, but the guidance cue remains. (D) Stage 11, germ cells are guided off the midgut into the mesoderm by the guidance cue that requires Slam.