Analysis of CMF1 reveals a bone morphogenetic protein-independent component of the cardiomyogenic pathway

Disruption of the CMF1 function in anterior mesoderm inhibits cardiac myoge nesis in avian embryos. In the present study, we show that CMF1 is a member of an emerging family of proteins that includes centromeric protein-F, mit osin, and LEK1. These proteins are characterized by their large size (350 k Da), dynamic subcellular distribution, and potential functions in cell divi sion and differentiation. The current data suggest that CMF1 is a unique me mber of this family by virtue of its restricted protein expression and vari ant subcellular distribution. Immunochemical analysis demonstrates that CMF 1 protein is expressed in cardiogenic cells prior to the activation of card iac structural gene products. In addition, we show that expression of CMF1 is not dependent on the bone morphogenetic protein (BMP) signaling pathway during development. Still, CMF1 cannot direct cardiomyogenesis in the absen ce of such factors as NKX-2.5. Taken with our previous data, this study sug gests that CMF1 is a BMP-independent component of the cardiomyogenic pathwa y.