Genetic Enhancers of sem-5Define Components of the Gonad-Independent Guidance Mechanism Controlling Sex Myoblast Migration in Caenorhabditis elegansHermaphrodites

Abstract

The migrations of the sex myoblasts in Caenorhabditis eleganshermaphrodites involve two guidance mechanisms: a gonad-dependent attraction that confers precise positioning of the sex myoblasts and a gonad-independent mechanism that is sufficient for coarse positioning in the absence of the gonad (Thomas et al.,1990). Here we show that mutations in unc-53, unc-71,and unc-73disrupt sex myoblast positioning in the absence of the gonad, while they do not affect positioning in the presence of the gonad. Thus, mutations in these genes appear to compromise the gonad-independent mechanism without affecting motility or the gonad-dependent attraction. Mutations in sem-5confer dramatic sex myoblast positioning defects in double mutant combinations with unc-53, unc-71,or unc-73mutations, even in the presence of the gonad. This suggests that sem-5is required for the gonad-dependent attractive mechanism. Mutations in let-60 rasand let-341also confer sex myoblast migration defects in an unc-53background, implicating these genes in gonad-dependent positioning as well.