Figure 3

Figure 3 Hapln1a promotes atrial growth. (A–C) mRNA in situ hybridization analysis of hapln1a expression at 26hpf in embryos from an incross of hapln1a^Δ241 heterozygous carriers. Wild-type and heterozygous siblings express hapln1a in the heart (bracket A, B, respectively), whereas hapln1a is absent in homozygous mutants (arrow C). (D–I) mRNA in situ hybridization expression analysis at 50hpf of myl7 (D–F) and myh6 (G–I) in wild-type siblings (D and G), hapln1a^Δ241 heterozygous siblings (E and H) or hapln1a^Δ241 homozygous mutant embryos (F and I). Scale bar = 50 μm. (J and K) Quantification of atrial area (J), and atrial outer curvature (K) in ISH-processed sibling embryos (wt/het) and hapln1a^Δ241 or hapln1a^Δ187 mutants (mut) at 50hpf. Atrial area is significantly reduced in hapln1a^Δ241 mutants compared to wild-type siblings (P = 0.013), and atrial outer curvature is significantly reduced in both hapln1a^Δ187 and hapln1a^Δ241 mutants (P = 0.033 and P = 0.032). In both J and K, n = 54 hapln1a^Δ187 wt; 104 hapln1a^Δ187 het; 60 hapln1a^Δ187 mut, 66 hapln1a^Δ241 wt; 116 hapln1a^Δ241 het; 53 hapln1a^Δ241 mut. (L–O) Maximum intensity projections of light-sheet z-stacks of live 50hpf (L and M) and 72hpf (N and O) Tg(myl7:lifeActGFP); Tg(fli1a:AC-TagRFP) transgenic wild-type (L and N), and hapln1a^Δ241 mutant embryos (M and O). Scale bar = 50μm. (P and Q) Quantification of atrial area (P), and atrial outer curvature (Q) in live light-sheet z-projections from wild-type sibling embryos and hapln1a^Δ241 or hapln1a^Δ187 mutants at 50hpf and 72hpf. Atrial area and atrial outer curvature are significantly reduced in hapln1a^Δ241 mutants (mut) compared to wild-type siblings (wt/het) at 50hpf (P = 0.0002, and P = 0.014). In both (P) and (Q), n = 4 hapln1a^Δ187 50hpf wt; 5 hapln1a^Δ187 50hpf mut, 7 hapln1a^Δ241 50hpf wt; 10 hapln1a^Δ241 50hpf mut; 4 hapln1a^Δ187 72hpf wt; 7 hapln1a^Δ187 72hpf mut, 9 hapln1a^Δ241 72hpf wt; 10 hapln1a^Δ241 72hpf mut. Comparative statistics carried out using a Kruskal–Wallis test with multiple comparisons.