Gata4 potentiates second heart field proliferation and Hedgehog signaling for cardiac septation

Abstract

GATA4, an essential cardiogenic transcription factor, provides a model for dominant transcription factor mutations in human disease. Dominant GATA4 mutations cause congenital heart disease (CHD), specifically atrial and atrioventricular septal defects (ASDs and AVSDs). We found that second heart field (SHF)-specificGata4heterozygote embryos recapitulated the AVSDs observed in germlineGata4heterozygote embryos. A proliferation defect of SHF atrial septum progenitors and hypoplasia of the dorsal mesenchymal protrusion, rather than anlage of the atrioventricular septum, were observed in this model. Knockdown of the cell-cycle repressor phosphatase and tensin homolog (Pten) restored cell-cycle progression and rescued the AVSDs.Gata4mutants also demonstrated Hedgehog (Hh) signaling defects. Gata4 acts directly upstream ofHhcomponents: Gata4 activated acis-regulatory element atGli1in vitro and occupied the element in vivo. Remarkably, SHF-specific constitutive Hh signaling activation rescued AVSDs in Gata4 SHF-specific heterozygous knockout embryos. Pten expression was unchanged inSmoothenedmutants, and Hh pathway genes were unchanged inPtenmutants, suggesting pathway independence. Thus, both the cell-cycle and Hh-signaling defects caused by dominantGata4mutations were required for CHD pathogenesis, suggesting a combinatorial model of disease causation by transcription factor haploinsufficiency.