Transcriptional regulation of human cardiac homeobox gene CSX1

Cardiac homeobox gene Csx/Nkx-2.5 is essential for normal heart development and morphogenesis and is the earliest marker for cardiogenesis. To elucida te the regulatory mechanisms of Csx/Nkx-2.5 expression, we have isolated an d characterized the upstream regulatory region of human Csx/Nkx-2.5 (CSX1). Transfection of the reporter gene containing a 965-bp CSX1 5' flanking reg ion indicated that this region confers cardiomyocyte-predominant expression of CSX1. Deletion and mutational analyses revealed two positive cis-regula tory elements in this region that are essential for CSX1 expression in card iomyocytes. Electrophoretic mobility shift assay revealed that nuclear prot eins prepared from cardiac myocytes bound to these elements in a sequence-s pecific manner. The identification of cis-regulatory sequences of the Csx/N kx-2.5 gene will facilitate further analysis for the upstream regulatory fa ctors that control the expression of Csx/Nkx-2.5 and the process of vertebr ate heart development. (C) 2000 Academic Press.