The gene
mab-3 appears to regulate a subset of sex-specific events in C. elegans male development. Mutations in
mab-3 have no apparent effect on hermaphrodites, but cause synthesis of yolk proteins and a limited lineage alteration in males. We infer that
mab-3 has at least two distinct male-specific functions. First,
mab-3 activity prevents yolk protein production by males, without affecting stage or tissue specificity of expression. Second,
mab-3 activity is required for expression of the male V ray cell lineage. Epistasis analysis is most consistent with a model in which
mab-3 is controlled by
tra-1, the last switch gene known to act in the somatic sex determination pathway. We discuss how genes such as
mab-3 might generate sexual dimorphism.