Neurogenesis in the dentate gyrus of the hippocampus begins during the embryonic stage and continues throughout life (Ming and Song, 2005; Zhao et al., 2008). Newborn dentate granule cells become integrated into the hippocampal neuronal circuitry through a stereotypic process, including neuronal morphogenesis, migration, axon/dendritic growth and synapse formation (Duan et al., 2008; Ge et al., 2008). One distinct feature of adult hippocampal neurogenesis is its prolonged course of development by new neurons, which is subjected to prominent activity-dependent regulation (Duan et al., 2008). For example, neuronal activation through seizures accelerates the tempo of adult neurogenesis (Overstreet-Wadiche et al., 2006) and prolonged seizures induce inappropriate integration of new neurons into the adult hippocampal circuitry (Jessberger et al., 2007). The speed of new neuron development during adult neurogenesis also appears to be crucial for spatial memory in rodents (Farioli-Vecchioli et al., 2008). While these and other studies have implicated the importance of tempo regulation in adult neurogenesis, the underlying molecular mechanism is not well understood.
