Zebrafish wnt2b is required for tbx5 and tgf10 expression and pectoral fin initiation and outgrowth. (A-F) Zebrafish embryos injected at the one-cell stage with a control morpholino (A,D), wnt2b morpholino (B,E) or wnt2b morpholino + tbx5 RNA (C,F), were allowed to develop for 5 days. Normal pectoral fin development (A, arrows) is abrogated after wnt2b morpholino injection (B, asterisks), and rescued by co-injection of tbx5 RNA (C, arrows). Other defects caused by tbx5 RNA injections were observed (arrowhead in C). (D-F) Cartilage staining confirms normal pectoral fin development in control injections (D, arrows) and after rescue with tbx5 RNA (F, arrows), and lack of pectoral fins after wnt2b morpholino alone (E, asterisks). Dorsal view of zebrafish embryos, anterior to the top. (G-K) Effect of wnt2b morpholino injections on tbx5 expression in whole embryos at 28 hpf (G,H) and in pectoral fin buds at 36 hpf (I-K). tbx5 is expressed in control-injected embryos in the presumptive pectoral fin bud (arrowhead) and in the eye (G). After injection of wnt2b morpholino, tbx5 expression was no longer detected in the presumptive fin field (arrowhead), but remained in the eye at 28 hpf (H). In 36 hpf embryos, expression was seen in the developing fin bud of control injected embryos (I), but was reduced after wnt2b morpholino injections of low dosage (2ng, J) or absent after injections of higher dosage (10 ng, K). Lateral view, anterior to the left. (L,M) Comparison of fgf10 expression patterns in embryos injected with 10 ng of control (L) or tbx5 (M) morpholino. After injection of wnt2b morpholino, expression of fgf10 in the presumptive fin bud forming area at 24 hpf can no longer be detected (M, asterisks), compared to the control-injected embryo (L, arrowheads). Dorsal view, anterior to the top. (N) wnt2b expression in embryos injected with 10 ng of tbx5 morpholino. In injected embryos, wnt2b expression remains unchanged in the LPM at 22 hpf (arrowheads). Dorsal view, anterior to the top. See Fig. 4B for comparison.
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