osr2 knock down results in abnormal pectoral fin. Brightfield images of control fins at 48 hpf show the pectoral fin extending toward the posterior (A) while osr2 morphants display only a fin stump (B). Embryos are oriented with anterior to the left and dorsal to the bottom in A, B. C: Methylene blue–stained transverse section of normal pectoral fin at 72 hpf. D: osr2 morphants showed abnormal pectoral fin morphology and lacked differentiated chondrocytes. col2a1 in situ hybridization analysis at 48 hpf of control embryos (E) and osr2 morphants (F). osr2 morphants showed reduction or disappearance of col2a1 expression in the pectoral fin. G–J: sox9a expression was reduced in osr2 morphants at both 24 hpf (H) and 48 hpf (J) compared to controls (G, I). K–N: tbx5a expression in lateral mesoderm at 30 hpf (K, L) and in the pectoral fin buds at 72 hpf (M, N) was not affected in osr2 morphants compared to controls. O–R: fgf24 expression is unaffected by osr2 knock down and is unchanged in the lateral mesoderm at 24 hpf (O, P) and is restricted to the apical ectodermal ridge in both control and osr2 morphants at 48 hpf (Q, R). Embryos in E, F, G–R are displayed from a dorsal view and anterior to the top.
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