CAPSULIN - A NOVEL BHLH TRANSCRIPTION FACTOR EXPRESSED IN EPICARDIAL PROGENITORS AND MESENCHYME OF VISCERAL ORGANS

Members of the basic helix-loop-helix (bHLH) family of transcription f actors have been shown to control development and differentiation of a variety of cell types. We describe a novel bHLH protein, called capsu lin, which is expressed specifically in mesodermally-derived cells tha t surround the epithelium of the developing gastrointestinal, genitour inary and respiratory systems during mouse embryogenesis. Capsulin tra nscripts also mark the spiral septum of the heart and progenitor cells that give rise to the pericardium and coronary arteries. Capsulin sha res high homology with a recently identified bHLH protein from Drosoph ila, called bHLH102C, which is expressed in visceral muscle cells that surround the midgut. Capsulin binds a specific E-box consensus sequen ce (CANNTG) as a heterodimer with the widely-expressed bHLH protein E1 2, but it does not activate transcription through that sequence on its own. Its restricted expression pattern and DNA binding activity sugge st that capsulin regulates gene expression in specific subtypes of vis ceral mesodermal cells involved in organogenesis and in precursor cell s that contribute to the pericardium, coronary arteries and regions of the heart. (C) 1998 Elsevier Science Ireland Ltd.