Transcriptional activator that binds to the consensus sequence 5'-AGATAG-3' and plays a key role in cardiac development and function (PubMed:24000169, PubMed:27984724, PubMed:35182466). In cooperation with TBX5, it binds to cardiac super-enhancers and promotes cardiomyocyte gene expression, while it down-regulates endocardial and endothelial gene expression (PubMed:27984724). Involved in bone morphogenetic protein (BMP)-mediated induction of cardiac-specific gene expression. Binds to BMP response element (BMPRE) DNA sequences within cardiac activating regions (By similarity). Acts as a transcriptional activator of ANF in cooperation with NKX2-5 (By similarity). Promotes cardiac myocyte enlargement (PubMed:20081228). Required during testicular development (PubMed:21220346). May play a role in sphingolipid signaling by regulating the expression of sphingosine-1- phosphate degrading enzyme, sphingosine-1-phosphate lyase (PubMed:15734735). {ECO:0000250|UniProtKB:P46152, ECO:0000250|UniProtKB:Q08369, ECO:0000269|PubMed:15734735, ECO:0000269|PubMed:20081228, ECO:0000269|PubMed:21220346, ECO:0000269|PubMed:24000169, ECO:0000269|PubMed:27984724, ECO:0000269|PubMed:35182466}. This is the function of GATA4 (GATA binding protein 4, ENSG00000136574).