Fibroblast growth factor-2 activates a latent neurogenic program in neuralstem cells from diverse regions of the adult CNS

During development of the mammalian brain, both neurons and glia are genera ted from multipotent neural stem cells. Although neurogenesis ceases in mos t areas at birth, stem cells continue to generate neurons within the subven tricular zone and hippocampal dentate gyrus throughout adult life. In this work, we provide the first demonstration that precursors native to regions of the adult brain that generate only glia can also generate neurons after exposure to FGF-2 in vitro. When progenitors isolated from hippocampal tiss ue were directly compared with cells isolated from the neocortex, both popu lations were able to initiate a program of proliferative neurogenesis. Gene tic marking and lineage analysis showed that a majority of the cells able t o generate neurons were multipotent precursors; however, progeny from these precursors acquired the competence to differentiate into neurons only afte r exposure to FGF-2. The recruitment of similar FGF-2-responsive cells from the adult optic nerve, a structure well isolated from the neurogenic zones within the brain, confirmed that neuron-competent precursors naturally exi st in widely divergent tissues of the adult brain.