Fgf8 is required for cardiac marker gene expression. Stages and markers as indicated. (A,B) Expression of nkx2.7 in wild-type (A) and ace (B) embryos. (C,D) Expression of gata4 in wild-type (C) and ace (D) embryos. (E-H) Expression of nkx2.5 in wild-type (E,G) and ace (F,H) embryos. Notice the differential sensitivity of the posterior nkx2.5 domain (dashed lines). (I,J) Expression of gata6 (arrows) in wild-type (I) and ace (J) embryos. (K,L) Late expression of nkx2.5 in dissected hearts of wild-type (K) and ace (L) embryos. A-F show dorsal views of whole embryos, anterior to the top. Embryos in G-J are flat mounted, anterior to the left. Embryos in G,H are stained for nkx2.5 and ntl (black) and gata4 (red). Embryos in I and J are double-stained for myoD to genotype the embryos (Reifers et al., 1998).
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