Fig. 2. Wnt/ß-catenin pathway is activated in the AFB of Hesx1^-/- mutants at early somite stages. (A,B) Rostral view of the Wnt1 expression domain in wild type (A) and Hesx1^-/- mutant (B) at the 3- to 4-somite stage. Wnt1 transcripts do not reach the rostral tip of the NP in wild-type embryos, but do so in Hesx1^-/- mutants (arrowhead). (C-F) Frontal (C,D) and lateral (E,F) views of the Fgf8 expression domain in wild type (C,E) and Hesx1^-/- mutant (D,F) at the 4- to 5-somite stage. Fgf8 expression in the anterior neural ridge (ANR) is reduced in the Hesx1^-/- mutant. Arrowheads in C,D indicate the posterior limit of the Fgf8 expression domain in the ANR. (G,H) Expression of the Wnt/ß-catenin target Axin2 in wild type (G) and Hesx1^-/- mutant (H) at the 3- to 4-somite stage. Dorsal view, anterior is to the bottom. Note the expansion of the Axin2 expression domain in the Hesx1^-/- mutant (H). Arrowheads indicate the rostral limit of Axin2 expression. (I-N) Dorsal (I-L) and lateral (M,N) views of the expression domain of the Wnt/ß-catenin target Sp5 in wild type (I,K,M) and Hesx1^-/- mutant (J,L,N) at the 5- to 6-somite (I,J) and the 2- to 3-somite (K-N) stages. Anterior is to the bottom (I-L) or to the left (M,N). Note the expansion of Sp5 expression throughout the anterior NP in the Hesx1 mutant (J,L,N). Only the most rostromedial region of the NP is free of Sp5 transcripts (arrowheads indicate the rostral limit of Sp5 expression).