UC Irvine

Neurogenesis in olfactory and vomeronasal sensory epithelia proceeds through two phases: primary neurogenesis, an early morphogenetic phase in which neural stem cells are established and expanded, and established neurogenesis, in which cell proliferation and differentiation are balanced to maintain constant neuron number. Together with secreted signals (extrinsic factors), stage-specific transcription factors (intrinsic factors) direct progressive restrictions in developmental potential that occur as neuronal stem cells and committed progenitor cells produce terminally differentiated neurons during each phase of neurogenesis. Olfactory epithelium neurogenesis is regulated by a negative feedback circuit in which endogenous cytostatic factors regulate the size of the stem/progenitor cell pool and total neuron number, endowing the olfactory epithelia with the ability to rapidly respond to neuron loss with regeneration.