GATA4 Is a Direct Transcriptional Activator of Cyclin D2 and Cdk4 and Is Required for Cardiomyocyte Proliferation in Anterior Heart Field-Derived Myocardium

Abstract

The anterior heart field (AHF) comprises a population of mesodermal progenitor cells that are added to the nascent linear heart to give rise to the majority of the right ventricle, interventricular septum, and outflow tract in mammals and birds. The zinc finger transcription factor GATA4 functions as an integral member of the cardiac transcription factor network in the derivatives of the AHF. In addition to its role in cardiac differentiation, GATA4 is also required for cardiomyocyte replication, although the transcriptional targets of GATA4 required for proliferation have not been previously identified. In the present study, we disrupted Gata4 function exclusively in the AHF and its derivatives. Gata4 AHF knockout mice die by embryonic day 13.5 and exhibit hypoplasia of the right ventricular myocardium and interventricular septum and display profound ventricular septal defects. Loss of Gata4 function in the AHF results in decreased myocyte proliferation in the right ventricle, and we identified numerous cell cycle genes that are dependent on Gata4 by microarray analysis. We show that GATA4 is required for cyclin D2, cyclin A2, and Cdk4 expression in the right ventricle and that the Cyclin D2 and Cdk4 promoters are bound and activated by GATA4 via multiple consensus GATA binding sites in each gene's proximal promoter. These findings establish Cyclin D2 and Cdk4 as direct transcriptional targets of GATA4 and support a model in which GATA4 controls cardiomyocyte proliferation by coordinately regulating numerous cell cycle genes.The cardiac lineage in mammals is initially specified from the anterior lateral mesoderm at embryonic day 7.5 (E7.5) in the mouse. The nascent cardiac mesoderm migrates anteriolaterally and fuses ventrally in the embryo to form a linear tube. The linear tube elongates through the addition of cells from the second heart field to the arterial and venous poles (1,12,28). A more restricted, anterior subset of these cells are added only to the arterial pole from the pharyngeal and splanchnic mesoderm. These cells, referred as the anterior heart field (AHF), give rise to the outflow tract, right ventricle, and ventricular septum (1,9,11,27,81). As cells from the AHF are added, the heart bends toward the ventral side, undergoes rightward looping, expands dramatically, and is eventually remodeled into the mature, four-chambered organ (13, 66).Embryonic cardiomyocytes differentiate as they continue to proliferate (48, 52). At early stages in development, cardiomyocytes have a high proliferation rate, which decreases progressively in late gestation (67). The high rate of cell cycle activity during the early stages of cardiomyocyte differentiation contributes to the growth of the future chambers within the linear tube during looping morphogenesis (42). The trabecular myocardium has a high rate of proliferation at this stage. As ventricular volumes increase, the trabeculations become compressed within the ventricular wall, resulting in a significant increase in the thickness of the compact myocardium (...

Gata4 and Gata5 Cooperatively Regulate Cardiac Myocyte Proliferation in Mice

“…Overexpression of Gata6 inhibits cell cycle progression of vascular smooth muscle cells by regulating expression of Cdkn2a p21 WAF1 (33). Finally, GATA4 directly regulates expression levels of Ccdn2 (cyclin D) and Cdk4 controlling myocardial cell proliferation in the anterior heart field (32).…”

“…Recent experiments demonstrated that GATA4 is required for cyclin D2, Cdk4, and cyclin A2 expression in the ventricular myocardium. Furthermore, cyclin D2 and Cdk4 are direct targets of GATA4 (32). To determine whether the ventricular myocardial hypoplasia observed in Gata4 ϩ/Ϫ 5 Ϫ/Ϫ FIGURE 2.…”

“…GATA4 has been shown to regulate myocardial proliferation and survival, whereas GATA6 inhibits cell cycle progression in vascular smooth muscle cells (32,33). Ki67 was used to assess cell proliferation rates in WT and Gata4…”

GATA4 regulates Fgf16 to promote heart repair after injury

“…4F). Indeed, it has been reported that CDK4 is essential for cardiomyocyte replication and is directly regulated by GATA4 (Rojas et al, 2008). To confirm whether GATA4 directly binds to the Cdk4 promoter, we cloned the Cdk4 promoter into a luciferase reporter plasmid.…”

Genetic Networks Governing Heart Development

“…It has been a powerful discovery tool in biology with the potential for further impact as transcriptomes are accessed at greater depth. As one illustration of its early application to heart development, Rojas et al used microarrays to survey changes to the transcriptome of murine SHF progenitors induced by loss of the cardiac-kernel factor GATA4 (Rojas et al 2008). Among dysregulated genes, those involved in the cell cycle were prominent, including direct GATA4 target genes encoding cyclin A2, cyclin D3, and cyclin-dependent kinase 4.…”