Transcription factor CHF1/Hey2 regulates coronary vascular maturation

The transcription factor CHF1/Hey2 has been implicated in a variety of cardiovascular developmental abnormalities including ventricular septal defect, deformed valves and cardiomyopathy. To date, its role in coronary vascular development remains unknown. We have found that KO mice developed coronary vascular abnormalities accompanied by a thin compact ventricular myocardium but grossly normal epicardial and subepicardial layers. The coronary vascular anomalies included dysmorphic large vessels and abnormal vascular structures at E15.5 and reduced recruitment of vascular smooth muscle cells into the coronary arteries at E18.5. In E18.5 KO hearts, the abnormal coronary veins demonstrated reduced expression of markers for vein identity. Whole-mount PECAM staining of the E18.5 KO hearts indicated that EphB4 negative vein networks were increased in the surface layers of the myocardium compared to those of the controls. CHF1/Hey2 was not expressed in the epicardium in vivo, and cultured epicardium-derived cells isolated from E12.5 wild-type mice showed no CHF1/Hey2 expression. KO mice with a myocardially expressed CHF1/Hey2 transgene partially rescued the vascular phenotypes. Quantitative RT-PCR analysis demonstrated that PDGF and Angiopoietin/Tie2 signaling pathways are altered in E12.5 KO hearts. Taken together, global CHF1/Hey2 deficiency caused impaired vascular formation, the reduced recruitment of vascular smooth muscle cells into coronary arteries and abnormally remodeled vein networks. These findings suggest that CHF1/Hey2 regulates the later steps of coronary vascular development in both a myocardial-dependent, non-cell autonomous fashion and likely a vascular cell-specific effect as well.