Fig. 2

Pygo1/2 mutant zebrafish and mouse embryos develop cardiac malformations reminiscent of CHD. (A) Schematic of the tripartite complex comprised of β-catenin, BCL9, and Pygo with their individual interaction domains together tethered to a WRE by TCF/LEF. (B) Schematic representation of the zebrafish pygo1 and pygo2 genes with annotated NHDs and PHDs and the Cas9 cutting site to generate mutants. The gene locus is represented as per genome annotation Zv10, with the main isoforms of both genes shown. See also the legend for Figure 1B. (C,D) CrispRVariants panel plot depictions of the germline alleles with a 5-bp or 1-bp deletion in pygo1 and pygo2, respectively. The top shows the genomic reference with the pygo1Δ5:g.2924_2928del and pygo2Δ1:g.3191del alleles shown below. Both alleles result in an out-of-frame deletion introducing a frameshift in the CDS. See also the legend for Figure 1C. (E,F) Bright-field images of live pygo1^Δ5;pygo2^Δ1 double mutants reveal cardiac edema (asterisks), craniofacial defects (arrowheads), and aberrant swim bladder inflation (arrows) as detected in bcl9^Δ29 mutants (lateral views; anterior to the left). (G–J) Hematoxylin/eosin-stained transverse sections of a murine heart at 10.5 d post-coitum (dpc) (G,H) and 14.5 dpc (I,J). At 10.5 dpc, the development of the heart and heart cushion was still largely normal in the mutants. At 14.5 dpc, the mutants displayed markedly smaller and thinner valves (dashed reduced compact outline), reduced compact ventricular myocardium (arrowhead), highly dilated atria, and defective or absent atrial septum (asterisks). (RA) Right atrium; (LA) left atrium; (RV) right ventricle; (LV) left ventricle. (K–N) Gross anatomical view of the heart and great vessels at 13.5/14.5 dpc as revealed by India ink injection. While normally the aorta (Ao) arises from the left ventricle (LV), and the pulmonary artery (Pa) arises from the right ventricle (RV), mutants showed a classic transposition of the great arteries (TGA; arrows) and hypoplastic aorta and pulmonary artery. (O,P) Schematic representation of the Bcl9/9l–Pygo1/2 interaction (O), the molecular configuration of this interaction when the HD1 domain in Bcl9/9l is deleted in Bcl9/9l-ΔHD1 mice (P), and heart sections at 14 dpc, stained with hematoxylin/eosin. The abrogation of this interaction leads to a delayed chamber septation (asterisks), hypoplastic myocardium (arrowhead), and valve deficiency. Bars: E,F, 250 µm.