(A) Indicated views of in situ hybridizations with sox10 and foxd3 probes from control, MO-, LS mRNA-injected, DMSO and U0126 treated embryos (16–18 somites). The head is to the top in all views. Note increased sox10 expression in the cranial neural crest in MO-and LS mRNA-injected embryos (arrows). Cranial views of the same region indicated by the arrow show delayed neural crest migration. At the same stage, foxd3 expression is elevated in trunk neural crest (arrowheads indicate region of higher magnification views). WT embryos treated with U0126 (150 µM) at the tailbud stage show elevated sox10 and foxd3 expression and delayed migration in cranial and trunk neural crest. (B) Lateral views of 26 somite embryos showing increased sox10 expression in MO- and LS mRNA-injected embryos in the head and along the dorsal midline (arrows). Trunk neural crest migration, as indicated by the most posterior migrating cells (arrowheads), also is delayed. Right panels show higher magnifications. (C) Lateral (left) and dorsal (right) views of WT embryos injected with control (gfp) or heat shock-inducible sox10 mRNA. A 2 hr heat shock at the 16- to 18-somite stage causes increased pigmentation in sox10 mRNA-injected embryos at 3 dpf; see Figure S2 for quantification and data. Scale bars are 200µ, position of the eye (e) and the anterior-posterior (A–P) position in the trunk views is indicated.