Localization of Transcription Factor GATA-4 to Regions of the Mouse Embryo Involved in Cardiac Development

To clarify the role of transcription factor GATA-4 in mammalian development, we have determined the pattern of expression of GATA-4 in early postimplantation mouse embryos. Using in situ hybridization and immunohistochemistry, we find that GATA-4 RNA and protein are expressed in cells associated with heart development. Intraembryonic expression of GATA-4 RNA is first apparent in coelomic epithelial cells of the primitive streak embryo (≈7.0-7.5 days postcoitum). During formation and bending of the heart tube (≈8 days postcoitum), GATA-4 RNA and protein are expressed in endocardium, myocardium, and embryonic structures containing precardiac mesoderm such as the septum transversum and intraembryonic coelomic epithelium. By the onset of cardiac septation (≈9 days postcoitum), abundant GATA-4 RNA expression is evident in endocardium, endocardial cushion tissue, and myocardium. Expression of GATA-4 by the myocardium continues through gestation and after birth. The temporal and spatial patterns of GATA-4 expression support a role for this factor in the regulation of cardiac differentiation, analogous to the established role of transcription factor GATA-1 in the regulation of hematopoiesis.