Both HEY1 and HEY2 repress transcriptional activation by GATA4 and GATA6 (inferred from mouse homologs). The repression appears to be due to the direct binding of HEY1 and HEY2 to GATA4 and GATA6 (inferred from mouse homologs). Though HEY1 and HEY2 act at least partially redundantly and are both expressed in endocardial cells, HEY1 is expressed in atrial cardiomyocytes while HEY2 is expressed in ventricular cardiomyocytes. Expression of HEY2 is increased by Notch signaling (inferred from mouse homologs). TBX20 and GATA proteins enhance expression of HEY2 in ventricular myocardium (inferred from mouse homologs).