Fig. 5. (A) In situ hybridization showing Sox10 expression just after the onset of neural crest migration. At these stages, Sox10 marks the entire neural crest stem cell population. (B) Double in situ hybridization showing expression of Sox10 (cyan) and N-tubulin (magenta) at stage 28. Sox10 expression at these stages is restricted to glia in the peripheral ganglia and CNS (aqua) as well as to melanoblasts (not shown). (C,D) Forced expression of Id3 leads to the persistence of Sox10 expression in neural crest cells migrating to the pharyngeal pouches on the injected side of the embryo (C, arrows). At this stage, expression of Sox10 has normally been downregulated in all neural crest cells except those committing to a glial or melanocyte fate, as seen on the uninjected side of the embryo (D). (E,F) No significant difference is seen in the number of migratory neural crest precursor cells following forced Id3 expression, as visualized by comparing expressing of Twist on the Id3-injected (E) versus uninjected (F) side of the embryo. (G,H) Overexpression of Slug leads to expanded expression of markers of neural crest precursor cells on the injected side of the embryo (arrowheads) at neural plate stages. (I,J) In contrast to forced Id3 expression, Slug expression does not lead to persistent expression of Sox10 in migrating neural crest cells (arrows indicate location of migratory neural crest cells).