Wnt/β-catenin signaling regulates LR asymmetry. (A-E) APC is required for left-right patterning of zebrafish heart but not visceral organs. Wild-type sibling (A,C) and apc mutant (B,D) embryos were stained at 28 hpf (A,B) for cmlc2 and at 52 hpf (C,D) for trypsin. (E) Quantification of cardiac jogging and looping, and pancreas positioning. Shown are dorsal views with anterior to the top. (F-L) Activation and repression of Wnt/β-catenin signaling differentially affect cardiac and visceral organ laterality. (F-H) Representative images of cardiac looping as revealed by cmlc2 staining of 52 hpf embryos. Ventral views with anterior to the top. (I-K) Representative images of the positioning of visceral organs as revealed by foxa3 staining of 52 hpf embryos. Dorsal views with anterior to the top. l, liver; g, gut; p, pancreas. (L) Quantification of cardiac and visceral organ laterality. H, heart; G, gut and other visceral organs; n, total numbers of embryos scored.