GATA proteins comprise a group of transcription factors that are related by the presence of conserved zinc finger DNA-binding domains, which bind directly to the nucleotide sequence core element GATA. There are six vertebrate GATA proteins, designated GATA-1 to GATA-6. GATA-6 plays a critical role in endoderm development. It is essential for development of the heart, gut, and other organs. Knock out of GATA-6 is embryonic lethal due to defects in formation of the heart tube and a failure to develop extraembryonic endoderm. Loss of expression, or loss of nuclear localization of GATA-6 is apparent in a large number of ovarian tumors.