Rb and Cellular Differentiation.

The pivotal role of the Retinoblastoma gene product pllO (pRb) in cellular differentiation has been postulated since the identification of pRb as a target of oncogenic events. The demonstration of the essential role of pRb during terminal differentiation of many tissues appeared evident along with the identification of the critical properties of pRb in regu-lating cell cycle progression and apoptosis. Permanent cell cycle arrest and resistance to both tumor formation and apoptosis are three cardinal features of terminal differentiation. Upon functional or genetic inactivation of pRb, cells from skeletal muscle, neuronal and hematopoi-etic lineages exhibit higher extent of apoptosis, fail to permanently exit the cell cycle and showincomplete differentiation. [ABSTRACT FROM AUTHOR]