Fig. 2

Induction of blimp1 expression by Hh signaling in presumptive slow muscle precursors requires their prior commitment to the myogenic fate. (A) MAb A4.1025 staining for all MyHC in a 24 hpf wild-type embryo. (B) MAb A4.1025 staining of a myoD; myf5 double morphant embryo showing few differentiated muscles within the somites at 24 hpf (arrow, n = 20/20). (C, D) myoD; myf5 double morphant embryos retain functional Hh signaling as demonstrated by normal expression of the Hh target genes ptc1 (C, n = 16/16) and myoD (D, n = 16/16) in adaxial cells. (E, H) Wild-type embryos showing blimp1 expression in the adaxial cells (arrowheads) and the neuro-ectodermal border (arrows). (F) blimp1 expression is absent from the adaxial cells of a smo mutant embryo. (G, I) blimp1 expression is specifically lost from adaxial cells in myoD; myf5 morphants while it appears unaffected in the neuro-ectodermal border (arrows, n = 23/23). Panels A and B depict lateral views; C–I depict dorsal views of 11 hpf embryos. C, D, H, I depict flat mounts; E–G depict whole mounts. Scale bars = 25 μm in A and C, and 100 μm in E. The scale bar in A applies to B; the scale bar in C applies to D, H and I and the scale bar in E applies to F and G.