Involved in epithelial-mesenchymal interactions in kidney and lung morphogenesis that include epithelial differentiation and branching morphogenesis. May be involved in the organogenesis of the spleen and heart and in cardiac and coronary artery development. May function in the development and sex differentiation of gonad via transcriptional regulation of AD4BP/SF-1. Efficient DNA binding requires dimerization with another bHLH protein. Forms a heterodimer with TCF3 and binds the E box (5'-CANNTG-3'). Expressed at high levels in lung, kidney, gut, heart, ovary and podocytes (visceral glomerular epithelial cells). Also found in spleen, large intestine, uterus, bladder and testis. Expressed during embryogenesis specifically in mesodermally-derived cells that surround the epithelium of the developing gastrointestinal, genitourinary, respiratory systems and in spiral septum of the heart and in epicardial precursor cells fated to form the coronary arteries. Expression pattern is sex- and stage-dependent during gonadogenesis. At 13.5 dpc expressed at higher levels in testis than ovary. In 3-month old adults expression drastically decreased in testis while it increased in ovary showing an opposite sex-dependent pattern in adults compared with fetuses. Expression in other organs was similar between the adults and the fetal stage.