Practice question

LIN-39 is Sex Combs Reduced-like Hox protein expressed in central body region P3.p-P8.p controlling vulval precursor competence and central patterning. LIN-39 maintains LET-23 EGFR expression, prevents premature fusion of VPCs with hyp7 syncytium during L1-L2 via repression of eff-1 fusogen. Without LIN-39, all six VPCs fuse and become refractory to LIN-3 induction, causing vulvaless phenotype despite normal anchor cell signaling and positioning. LIN-39 cooperates with Wnt effectors BAR-1 beta-catenin, LIN-31 forkhead, and other Hox genes, linking anteroposterior patterning to tissue competence.