Fig. 8. Summary of the molecular changes in facial branchio-motoneurons of Nkx6.1 mutant embryos. (A) Between E10.5 and E11 pre-migratory facial branchio-motor (fbm) neurons in r4 express both Nkx6.1 and Nkx6.2. Early migratory populations of fbm neurons progress into rostral r5 in both wild-type and Nkx6.1 mutant embryos, and do not express the cell-surface receptors Unc5h3, Ret and neogenin. (B) Although Nkx6.2 is strongly expressed at the early stages of fbm neuron migration, later populations of pre-migratory fbm neurons at E12.5 express only low levels of Nkx6.2. At E12.5, some fbm neurons have already migrated from r4 into r6, and Unc5h3, Ret and neogenin are expressed in these neurons in a rhombomere-specific pattern. In Nkx6.1 mutants, fbm neurons do not migrate caudally, and show ectopic expression of Unc5h3 and Ret in r4.

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