Deficient GATA6-ACKR3/CXCR7 signaling leads to bicuspid aortic valve

AbstractThe cardiac outflow tract (OFT) transiently links the ventricles to the aortic sac and gives rise to the arterial valves. Abnormalities of the arterial valves, mainly bicuspid aortic valve (BAV), are the commonest congenital anomalies.Gata6inactivating mutations cause cardiac OFT defects and BAV, but the cellular and molecular mechanisms are poorly understood. We find thatGata6STOP/+mice, generated by CRISPR-Cas9, display highly penetrant BAV (70%), and a membranous ventricular septal defect (43%). OFT development inGata6STOP/+mice is characterized by decreased proliferation and increased presence of ISL1-positive progenitor cells, suggestive of aberrant cardiovascular differentiation. In support, conditionalGata6deletion with theMef2cAHF − Credriver line recapitulatesGata6STOP/+phenotypes, indicating a cell-autonomous requirement forGata6in the SHF.Gata6STOP/+mice display dramatic reductions in OFT length and caliber, associated with deficient cardiac neural crest cells (cNCCs) contribution in the mutant OFT, potentially underlying the valvulo-septal defects. RNA-seq analysis ofGata6STOP/+OFT reveal multiple depleted pathways linked to cell proliferation and migration, and highlightACKR3/CXCR7as a candidate gene regulating migratory effects downstream of GATA6. Consistently, mesenchymal cell migration and invasion are drastically reduced in explantedGata6STOP/+OFT tissue. Supplementing wild type OFT explants with CXCR7 agonists decreases mesenchymal cell migration and increases invasion, these effects are suppressed in theGata6STOP/+explants, suggesting that CXCR7-mediated migration and invasion is Gata6-dependent. These findings demonstrate a requirement for CXCR7 downstream ofGata6in OFT development and suggest that the cellular defects associated with BAV in GATA6-deficient mice can be ascribed, in part, to reduced CXCR7 function.