The physiological demands made upon precursor cell populations during different developmental epochs can be remarkably divergent, particularly in tissues that do not undergo constant turnover in the adult animal. In such tissues, with the central nervous system (CNS) being a prime example, the rapid increase in numbers of precursor cells and their differentiated progeny becomes turned off over a relatively short period of time. Once this period of rapid cell generation ends, precursor cell populations may be maintained in the adult tissue to participate in homeostatic cell replacement during normal function and to repair damaged tissue following injury. The regulation of the precursor cells resident in adult tissue must, however, be different in some manner from that which characterizes the explosive growth of early development.
It would be of great interest to understand the biological basis for the different...
