Re-programming of C. elegans male epidermal precursor fates by Wnt, Hox, and LIN-12/Notch activities

In Caenorhabditiselegans males, different subsets of ventral epidermal precursor (Pn.p) cells adopt distinct fates in a position-specific manner: three posterior cells, P(9–11).p, comprise the hook sensillum competence group (HCG) with three potential fates (1°, 2°, or 3°), while eight anterior cells, P(1–8).p, fuse with the hyp7 epidermal syncytium. Here we show that activation of the canonical BAR-1 β-catenin pathway of Wnt signaling alters the competence of P(3–8).p and specifies ectopic HCG-like fates. This fate transformation requires the Hox gene mab-5. In addition, misexpression of mab-5 in P(1–8).p is sufficient to establish HCG competence among these cells, as well as to generate ectopic HCG fates in combination with LIN-12 or EGF signaling. While increased Wnt signaling induces predominantly 1° HCG fates, increased LIN-12 or EGF signaling in combination with MAB-5 overexpression promotes 2° HCG fates in anterior Pn.p cells, suggesting distinctive functions of Wnt, LIN-12, and EGF signaling in specification of HCG fates. Lastly, wild-type mab-5 function is necessary for normal P(9–11).p fate specification, indicating that regulation of ectopic HCG fate formation revealed in anterior Pn.p cells reflect mechanisms of pattern formation during normal hook development.