Fig. 7. Facial branchio-motoneurons in r4 co-express Nkx6.1 and Nkx6.2. Immunofluorescence detection of Nkx6.2 (red in A,B and green in C,D) with Nkx2.2 (green in A), Isl1 (green in B), Nkx6.1 (red in C,D) on sections through r4 in wild-type (A-C) and Nkx6.1 mutant (D) embryos at E10.5. Nkx6.2 is co-expressed with Nkx2.2 (yellow appearing cells in A), Isl1 (yellow appearing cells in B) and Nkx6.1 (yellow appearing cells in C). The number of Nkx6.2-expressing cells and the level of Nkx6.2 expression are not changed in Nkx6.1 mutants (D). (E-H) Whole-mount in situ hybridization with Nkx6.2 on flat-mounted hindbrains from E11.0 (E,F) and E12.5 (G,H) wild-type (E,G) and Nkx6.1 mutant embryos (F,H). At E11.0, Nkx6.2 is strongly expressed in facial branchio-motor (fbm, nVII) neurons in r4, but not in migrating fbm neurons in r5 or r6 (E). At E12.5, expression of Nkx6.2 in fbm neurons is markedly downregulated (G). Trigeminal branchio-motoneurons (nV) express Nkx6.2 at E11.0 (E) and E12.5 (G). Nkx6.2 expression in fbm neurons does not differ between wild-type and Nkx6.1 mutant embryos (E-H). However, in Nkx6.1 mutants, Nkx6.2 does not mark the trigeminal branchio-motoneurons at E11.0 (F), and is only faintly detected in these neurons at E12.5 (H). The signal may be decreased in Nkx6.1 mutants, because trigeminal neurons are not clustered as a compactly as in wild-type embryos.

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