The cTnI promoter is activated by mutation or deletion of GATA sites in skeletal muscle cells in vitro. Transfection experiments of cTnI-CAT constructs in cultured primary cardiomyocytes (grey bars) and skeletal muscle cells (black bars). Schematic drawings of constructs are as in Fig. 1. Note that mutation of GATA sites leads to decreased promoter activity in cardiomyocytes but increased activity in skeletal muscle cells. Values (means ± S.E.) are expressed as fold increase in normalized CAT activity over the promoterless construct. Each construct was tested in 4 to 5 independent experiments.