CELL-CYCLE ARREST AND MORPHOLOGICAL-DIFFERENTIATION CAN OCCUR IN THE ABSENCE OF APOPTOSIS IN A NEURONAL CELL-LINE

Apoptotic cell death plays a critical role in the development of the n ervous system. Although the apoptotic death of mature non-dividing neu rons has been extensively studied, the mechanisms mediating the extens ive cell death in areas of the developing brain where proliferating ne uroblasts are differentiating into mature neurons have not been analyz ed. We have previously shown that the cell cycle arrest of a prolifera ting neuronal cell line by transfer from medium containing 10% foetal calf serum (FCS) to serum-free medium results in the morphological dif ferentiation of some cells and the death of others by apoptosis. Here we show that the effect of 10% FCS can be mimicked by medium containin g either similar concentrations of newborn or adult bovine serum or 1% FCS all of which maintain cellular proliferation and inhibit differen tiation and apoptosis. In contrast, the presence of 0.5% FCS in the me dium effectively prevents apoptosis but does not allow cellular prolif eraton or inhibit morphological differentiation. Hence cell cycle arre st and differentiation can occur in the absence of apoptosis in cells of neuronal origin and the factors in serum responsible for modulating these processes are likely to be distinct.