Genome-Wide Expression Profiling of Neurogenesis in Relation to Cell Cycle Exit

Neurogenesis is the process by which new brain cells are produced either during development or in the adult brain. More specifically, it is “the proliferation of neuronal precursor cells to produce neurons.” Both definitions embody a key role for the cell cycle in the process particularly because the brain is an architecturally complex, multicompartmented tissue and the correct numbers of neurons (and glial cells) must be placed into each compartment. The process is made more complicated by the fact that neurons within each compartment are highly specialized, mandating that the new neurons also have the correct phenotype. Therefore, a mechanistic understanding of neurogenesis requires an understanding of several processes—control of the cell cycle to generate neurons in sufficient numbers, spatial mechanisms that ensure the correct number of cells in each compartment, the differentiation process that transforms a progenitor cell into a neuron, and an explanation of how so many neuronal subtypes can be readily created. Equally important is an understanding of the temporal coordination of these four processes, particularly regarding cell cycle exit.