Fig. 5: Onset of left–right morphological asymmetry before heart looping.
a, Schemes show the calculated principal directions of the IFT (orange lines) and the polar coordinates system with θ and φ angles. rsh, right sinus horn; lsh, left sinus horn; vr, vectorial direction of rsh; vl, vectorial direction of lsh. b, Plot showing the evolution of the θ angles depending on the d1/d2 value. Curves represent Padé approximations of every group of specimens. c, Evolution of P values as a function of d1/d2 for the deviation of the θ angle from left–right symmetry and for the comparisons between experimental groups, as indicated. A mixed linear model was applied to estimate the asymmetry between both sides at different stages (fixed effects) adjusting by the angle with two-sided P value calculation and applying Sidak’s correction for multiple tests. d, Separated values of θl and θr for the two groups of control specimens. Analysis of covariance has been applied to test whether slopes are significantly different calculating two-tailed P values; NS, not significant. e, Separated values of θl and θr for the Nodal-mutant specimens. The statistical analysis was the same as in d. f, Schematic representation of the different evolution of θl and θr angles in wild-type and Nodal-mutant embryos. g, Specific wild-type hearts from different groups, highlighting the acute angle between the right IFT insertion and the ventricle (red arrow) and the smooth transition on the opposite side (gray arrow), often accompanied by a small bulge; n, number of specimens showing this feature over the total number of specimens in each staging group. The black arrow illustrates the direction of looping.
