a, CREB transcriptional reporter assay, reflecting PKA-C mediated substrate phosphorylation, in HEK293 cells transfected with PKA-Cɑ and the indicated SMO674 constructs. Data represent the mean +/− standard deviation, n = three biologically independent samples. b, GLI transcriptional reporter assay in Smo−/− MEFs transfected with a GFP negative control (Ctrl), or the indicated wild-type (wt) or mutant SMO constructs. Cells were treated with conditioned medium containing the N-terminal signaling domain of Sonic hedgehog (ShhN, green), or control, non-ShhN-containing conditioned medium (Ctrl, black). Data represent the mean +/− standard deviation, n = three biologically independent samples. c, Wild-type or smo−/− zebrafish injected with the indicated mRNA constructs were stained for Prox1 (magenta) or Engrailed (En, green) to mark muscle fiber nuclei. n=12 (uninjected), n=41 (SMO wt), n= 47 (SMO WRR). P < 0.05 (*); P < 0.01 (**), P < 0.001 (***), n.s. = not significant. See Supplementary Table 1 for full statistical analysis of Fig. 6a,b.