EGL-17(FGF) expression coordinates the attraction of the migrating sex myoblasts with vulval induction in <i>C. elegans</i>

During the development of the egg-laying system in Caenorhabditis elegans hermaphrodites, central gonadal cells organize the alignment of the vulva with the sex myoblasts, the progenitors of the egg-laying muscles. A fibroblast growth factor [EGL-17(FGF)] and an FGF receptor [EGL-15(FGFR)] are involved in the gonadal signals that guide the migrations of the sex myoblasts. Here we show that EGL-17(FGF) can act as an instructive guidance cue to direct the sex myoblasts to their final destinations. We find that egl-17 reporter constructs are expressed in the primary vulval cell and that EGL-17(FGF) expression in this cell correlates with the precise positioning of the sex myoblasts. We postulate that EGL-17(FGF) helps to coordinate the development of a functional egg-laying system, linking vulval induction with proper sex myoblast migration.