s441 mutants show defects in the development of organs derived from epithelial tissues. (A, B) Comparison of 36 hpf wildtype and s441 mutant embryos. (B) s441 mutant embryos show defects in heart development (red arrow), failure of the brain ventricles to inflate (black arrow), and dorsal curvature. (C, D) Dorsal views comparing 30 hpf wildtype and s441 mutant hearts as assessed by myl7 expression. (C) In wildtype embryos, the heart elongates to form a tube. (D) In s441 mutant embryos, the heart fails to elongate. (E, F) Transverse sections of 72 hpf wildtype and s441 mutant larvae through a region just posterior to the endodermal organ-forming region. The pronephric ducts marked by acetylated-tubulin staining are also visible in these sections (white arrowheads). (E) Wildtype larvae form one polarized lumen in the posterior gut (red arrow). (F) s441 mutants occasionally show multiple lumens in the gut (red arrows). (G, H) Transverse sections of 30 hpf Tg(gutGFP)s854 wildtype and s441 mutant embryos. Sections are through the endodermal organ-forming region and were stained for filamentous actin and aPKC. (G) In wildtype embryos, the right side of the LPM (outlined in white) moves ventrally towards the endoderm while the left side (outlined in yellow) moves dorsally. (H) In s441 mutant embryos, the LPM fails to undergo asymmetric morphogenesis and both sides move dorsal to the endoderm. (I, J) Rhodamine dextran injected ventricles. Lateral (I) and dorsal (I′) views show that wildtype embryos have well-inflated (arrow) and continuous (arrowhead) brain ventricles. Lateral (J) and dorsal (J′) views illustrate that s441 mutant embryos do not form fully inflated brain ventricles (arrow) and that the lumen is discontinuous (arrowhead). (K, K′) Lateral views of 32 hpf wildtype and s441 mutant embryos show the absence of an inflated hindbrain ventricle (arrows) in mutants compared to wildtype.
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