Fig. 3.

Alteration of Neurog1, Neurod, Math3 and Nscl1 expression in Eya1^−/− and Six1^−/− epibranchial neuronal precursors. (A–F) Transverse section hybridization showing Neurog1 expression in the otic vesicle (ov) and in the VIIIth ganglion region and epibranchial (VII, IX) neuronal precursors in wild-type embryos (A,D), no expression in Eya1^−/− epibranchial neuronal precursors (arrow in B,E) and reduced expression in Six1^−/− epibranchial neurons (arrow in C,F). Note that Neurog1 expression was observed in the VIIIth precursors (open arrow in B,C). (G–L) Transverse section hybridization showing Neurod expression in the VIIIth and epibranchial neuronal precursors in wild-type embryos (G,J), no expression in epibranchial precursors in Eya1^−/− embryos (arrow in H,K) and no expression (arrow in I) or reduced expression in Six1^−/− epibranchial neurons (arrow in L). Note that Neurod expression was detected in the VIIIth neuroblast precursors (open arrow in H,I). (M–O) Whole-mount hybridization showing Math3 expression in epibranchial neurons in wild-type embryos (M), only a few Math3-positive cells in Eya1^−/− Xth neurons (open arrow in N), and reduced expression in Six1^−/− IXth and Xth neurons (O). (P–R) Whole-mount hybridization showing Nscl1 expression in cranial sensory ganglia in wild-type embryos (P). In Eya1^−/− embryos, while Nscl1 expression appeared relatively normal in the Vth ganglion, it expression is absent in VIIIth, VIIth and IXth ganglia and very few Nscl1-positive cells were detected in Eya1^−/− Xth neurons (open arrow in Q). (R) Nscl1 expression is also absent in Six1^−/− VIIIth ganglion and markedly reduced in Six1^−/− VIIth (arrowhead) and IXth (arrow) ganglia.