Fig. 4

Characterization of the role of Hh pathway in swimbladder development. (A–D) EGFP expression in Et(krt4:EGFP)^sq33-2 in wild type (A), syu^t4(B), Ihha morphants (C), and smo^b641 (D) backgrounds. Panel (A) shows normal swimbladder epithelium in wild type control and the swimbladder is hypoplastic in syu^t4(B), reduced in Ihha morphants (C), and absent in smo^b641 (D, white arrowheads). (E–H) Expression of hb9 was normal in wild type control (E), almost absent in syu^t4 (F) reduced in Ihha morphants (G), and absent in smo^b641 (H) at 72 hpf. (I–L) Mesenchymal fgf10 expression is normal in wild type (I), reduced and disorganized in syu^t4 (J), reduced and disorganized in Ihha morphants (K), and absent in smo^b641 (L). (M–P) Smooth muscle is absent in all experimental larvae as indicated by the absence of acta2 expression. (Q–T) Mesothelial anxa5 expression was well-organized in wild type controls (Q), disorganized and presented as two lateral stripes of cells (arrowhead) in syu^t4 mutants (R), organized but severely reduced in Ihha morphants (S), and significantly reduced and presented as scattered cell clusters in smo^b641 mutants (T). The epithelial expression in Ihha morphants is denoted by white arrowhead. (U–X) cross sections of 4 dpf control (U), syu^t4 (V), Ihha morphants (W) and smo^b641 (X) larvae stained by hematoxylin–eosin. Abbreviations: ba, branchial arches; e, epithelium; g, gut; m, mesenchyme; nt, neural tube; n, notochord; o, outer mesothelium; sb, swimbladder. Scale bars: 250 mm.