Fig. 6. Wnt/MAP kinase signaling plays a role in MS-derived body wall muscle development. The left column (A) shows the comma stage pattern of body wall muscle (MHC A) and pharyngeal muscle (3NB12) in a wild-type embryo. Embryos depleted of MEX-1 activity (B) have a large excess in body wall and pharyngeal muscle due to cell fate transformations that causes a reiteration of MS-like lineages (Mello et al., 1992). The right column (C) shows the effects of blocking Wnt/MAP kinase signaling using wrm-1 RNAi, in an embryo co-depleted of mex-1. There is a severe reduction in the number of body wall muscle-like cells and concomitant increase in pharyngeal-like muscle cells demonstrating the role of Wnt/MAP kinase signaling in body wall formation within the MS lineage. Images in B and C are representative of focal planes throughout the embryo.