BCL2 REGULATES NEURAL DIFFERENTIATION

A main function attributed to the BCL2 protein is its ability to confe r resistance against apoptosis. In addition to the constitutively high expression of BCL2, caused by gene rearrangement in follicular lympho mas, elevated expression of the BCL2 gene has been found in differenti ating hematopoietic, neural, and epithelial tissues. To address the qu estion of whether the expression of BCL2 is a cause or consequence of cell differentiation, we used a human neural-crest-derived tumor cell line, Paju, that undergoes spontaneous neural differentiation in vitro . The Paju cell line displays moderate expression of BCL2, the level o f which increases in parallel with further neural differentiation indu ced by treatment with phorbol 12-myristate 13-acetate, Transfection of normal human BCL2 cDNA in sense and antisense orientations had a dram atic impact on the differentiation of the Paju cells. Overexpression o f BCL2 cDNA induced extensive neurite outgrowth, even in ion: serum co ncentrations, together with an increased expression of neuron-specific enolase. Paju cells expressing the anti-sense BCL2 cDNA construct, wh ich reduced the endogenous levels of BCL2, did not undergo spontaneous neural differentiation. These cells acquired an epithelioid morpholog y and up-regulated the intermediate filament protein nestin, typically present in primitive neuroectodermal cells. The manipulated levels of BCL2 did not have appreciable impact on cell survival in normal cultu re. Our findings demonstrate that the BCL2 gene product participates i n the regulation of neural differentiation.