Figure 6.

Posterior up-regulation of hapln1a in the cardiac disc is independent of left–right asymmetry. (A–G) mRNA in situ hybridization analysis of hapln1a expression in an incross of spaw (A and B) or pkd2^hu2173 (C–G) heterozygous carriers. At 19hpf hapln1a is expressed in the posterior cardiac disc of both spaw mutant embryos (B, n = 17/19), and pkd2 mutant embryos (D, n = 13/13), similar to sibling embryos. At 26hpf pkd2 mutant hearts that have jogged to the left exhibit left side up-regulation of hapln1a (E, n = 18), pkd2 mutant hearts on the right have right side up-regulation of hapln1a (F, n = 9), and pkd2 mutant hearts that remain at the midline have no clear left–right asymmetry in expression (G, n = 13). (H) Quantification of position of hapln1a expression in sibling and pkd2^hu2173 mutant embryos at 26hpf, n = 138 pkd2^hu2173 siblings, 40 pkd2^hu2173 mutants. (I–P) Fluorescent immunostaining of Hapln1a (magenta) and cardiac troponin (green) at 26hpf in wild-type siblings (I–L) or spaw mutant embryos (M–P). Wild-type siblings exhibit left-sided deposition of Hapln1a in the heart tube (I–L, n = 6), whereas spaw mutant embryos exhibit ventral localization of Hapln1a (M–P, n = 6). (I and M) Dorsal views. (J–L and N–P) Optical transverse sections. Scale bar = 50μm. L, left; R, right; D, dorsal; V, ventral.