ECTOPIC EXPRESSION OF THE CCAAT ENHANCER-BINDING PROTEIN-ALPHA PROMOTES THE ADIPOGENIC PROGRAM IN A VARIETY OF MOUSE FIBROBLASTIC CELLS

The CCAAT/enhancer-binding protein alpha (C/EBP alpha) has been implicated in the regulation of adipoblast differentiation. In this study we investigate the potential of C/EBP alpha to promote the adipogenic program in a variety of fibroblastic cells. Transduction of the C/EBP alpha gene into eight mouse fibroblastic cell lines by retroviruses and DNA transfection generates adipocyte colonies at variable frequencies. The most dramatic results are obtained with NIH-3T3 cells, in which the percentage of G418-resistant colonies that exhibit the adipocyte morphology is reproducibly >50% when the C/EBP alpha gene is transduced by retroviruses. The ability to promote the adipogenic program requires the potent transcriptional activation domain of C/EBP alpha and is not observed with C/EBP beta. Paradoxically, in spite of its antimitogenic effects, clonal cell lines that stably express high amounts of C/EBP alpha can readily be generated. Stable expression of C/EBP alpha in BALB/c-3T3 cells dramatically enhances their ability to terminally differentiate into adipocytes. The results demonstrate that C/EBP alpha can efficiently promote the adipogenic program in a variety of mouse fibroblastic cells, including those that have little or no spontaneous capacity to undergo adipogenesis.