Fig. 7. Expression of Krox20 in r3 is restored in Gbx2 mutants by removing Otx2 function. (A-D) Double labeling for Six3 (arrowheads) and Krox20 (arrows) expression in wild-type (A), Gbx2^–/– (B), Otx2^hOtx1/hOtx1 (C) and Gbx2^–/–; Otx2^hOtx1/hOtx1 (D) embryos at the eight-somite stage. Insets show Six3 expression in embryos of corresponding genotypes at the 3-somite stage. Two stripes of Krox20 expressing cells (arrows), corresponding to r3 and r5, are found in wild type, Otx2^hOtx1/hOtx1 and Gbx2^–/–; Otx2^hOtx1/hOtx1 embryos, but there is only a single stripe of Krox20 expression in r5 of Gbx2^–/– embryos. (E-H) Hoxa2 expression in wild-type (E), Gbx2^–/– (F), Otx2^hOtx1/hOtx1 (G) and Gbx2^–/–; Otx2^hOtx1/hOtx1 (H) embryos at E9.5. Hoxa2 expression in rhombomeres is bracketed, whereas the expression in neural crest cells migrating from r4 is indicated by arrows. R3 expression of Hoxa2 is rescued in Gbx2^–/–; Otx2^hOtx1/hOtx1 mutant embryos, whereas r2 expression of Hoxa2 is missing.

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