Figure 3.

Absence of the ngn2-expressing sensory sublineage in the emigrating crest of mutant embryos. Whole mount in situ hybridization experiments showed ngn2 expression in the neural tube and in placodes (arrowheads) of control and mutant embryos at E9.5 (A–D). In migratory crest, ngn2 mRNA was only detectable in control (A and B, arrow) but not in mutant embryos (C and D, open arrow). The boxes in A and C indicate the areas enlarged in B and D, respectively. On transverse sections at E9.0, ngn2-positive neural crest cells were found in control (E, arrow) but not in mutant (F, open arrow) embryos. In contrast, on adjacent sections, neural crest emigrating from the dorsal neural tube was marked by sox10 mRNA both in control and mutant embryos (G and H, arrows). As at earlier stages, ngn2 mRNA was present in the DRG anlage of control (K, arrow) but not of mutant embryos (L, open arrow) at E10.5. Hybridization with a wnt1 riboprobe showed maintained wnt1 expression in the emerging crest of mutant embryos (J, arrow), whereas it was down-regulated in neural crest of control embryos (I, open arrow) at E9.0. Bars: (E–J) 10 μm; (K and L) 20 μm.