Figure 4: Chiral heart looping occurs independently from cardiac disc rotation.

(a) Still images (dorsal view, anterior up) from time-lapse movies generated from projected confocal stacks using the Tg(myl7:GFP) transgenic line labelling all cardiomyoscytes. Blue, green, red and turquoise traces indicate movement of individual cells in wild-type or sfw mutants embryos between 19.5 hpf and 23 hpf. Ventral view stills indicate direction of heart looping at 55 hpf in time-lapse-imaged embryos. (b) Schematic showing method for analysis of cardiac rotation. (c) Quantification of cardiac disc rotation in wild-type embryos with a d-looped heart, sfw mutants with d-looped heart and sfw mutants with s-looped heart (n=4 for each category). Error bars indicate s.e.m. Significance determined by Student’s t-test indicated by asterisks: *P<0.05; n=4 embryos for each category (wild-type, d-loop mutant, s-loop mutant). Scale bars, 50 μM (a).