Fig. 4

Impaired expression of bmp4, fgf8a, and1 and msx genes in the pectoral fin region of dlx5a/6a morphants.

Whole mount in situ hybridization for bmp4 (A, A2–B, B2), fg8a (C, C2), and1 (D, D2), msxB (E, E2–F, F2) and msxC (G, G2–H–H2) at 24 and 48 hpf in dorsal views of control (A–H) and dlx5a/6a morphant (A2–H2) embryos. At 24 hpf, bmp4, msxB and msxC genes are expressed in apical ectodermal cells of the presumptive pectoral fin bud (PPF) in control embryos (A, E, G). In dlx5a/6a morphants, bmp4 expression is lost or altered in the presumptive pectoral fin bud (A2) and the msxB and msxC transcripts are hardly detectable (E2, G2). In 48 hpf control embryos, bmp4 is expressed in the pectoral fin fold (PFF), the underlying mesenchyme and in mesodermal cells of the pectoral fin bud (PFB) (B). At the equivalent stage, fgf8a is detected in PFF ectodermal cells (C), and and1 expression is observed in the distal mesenchyme and in epithelial cells of the PFB but not in the PFF (D). The msxB gene is expressed in the PFF and the underlying mesenchyme (F), and msxC is detected in the mesenchymal cells but not in the PFF (H). In contrast to what is observed in controls at 48 hpf, dlx5a/6a morphants show a marked decrease or loss of expression of the PFB markers associated with pectoral fin agenesis (B2–D2, F2, H2). (I) Schematic representation of the pectoral fin bud at 48 hpf summarizing the expression of dlx5a and the analyzed PFB markers in their corresponding cellular types. Scale bars 50 μm.