Transcription factor required for the development of the heart and the spleen. Implicated in commitment to and/or differentiation of the myocardial lineage. May regulate the expression of genes involved in cardiogenesis and play a role in the formation of gut and the pharyngeal region. Binds to the core DNA motif of promoter. Homodimer (via the homeobox); binds DNA as homodimer. Heart and gut tissue. It is first expressed in early neurula embryos (about stage 15) in a bi-lobed pattern at the front of the embryo (this corresponds to the presumptive heart mesoderm). By the end of neural fold closure it is highly expressed in the presumptive heart region. By stage 26-27 (at which heart differentiation begins) its expression can be clearly seen in the heart and the level in embryonic heart decreases at later stages of development. As expression within heart declines low level expression is seen in the foregut and the pharyngeal region. The homeobox domain binds to double-stranded DNA. Belongs to the NK-2 homeobox family.