Figure 7.

Mash1 does not rescue the development of Ngn2-dependent sensory neurons in dorsal root ganglia. (A, B). Transverse section of E9.5 embryos sectioned following whole mount in situ hybridization with a Mash1 probe. Mash1 is expressed in sympathetic ganglia (arrowheads) of both wild-type and Ngn1^Δ; Ngn2^KIMash1 double mutant embryos. Mash1 expression is also observed in migrating neural crest cells entering DRGs in a Ngn2^KIMash1 embryo. (C–F) Mouse embryos at E10.5 are probed with the pan-neuronal marker SCG10. A wild-type embryo shows DRG staining well beyond the 20^th somite (C, arrow). SCG10 expression in Ngn2^KIMash1 (E) is delayed in comparison to the wild-type embryo, as also observed in Ngn2^Δ mutants (D). Arrowhead points to the eighth somite (C–E). Ngn1^Δ, Ngn2^KIMash1 embryo (F) shows no SCG10 staining in DRGs, indicating that no sensory neurons are generated by Mash1 expression from the Ngn2 locus.