Postnatal Neurogenesis in the Subventricular Zone: A Manipulable Source for CNS Plasticity and Repair

Neurogenesis is the production of new nerve cells or neurons, a specialized class of cells that make up the functional components of the central nervous system (CNS). Throughout most of the CNS this process of neurogenesis is limited to the developmental period before birth, after which time no new cells are added to the pre-established circuitry. In mammals including humans however, neurogenesis persists into the early postnatal period in two discrete brain regions: the subgranular zone in the hippocampus and the subventricular zone (SVZ) lining the lateral ventricles [1-5]. It is unknown why neurogenesis continues in such discrete locations yet is excluded from most other brain regions. A finite number of neurons is thought to afford us a stable set of circuitry that is able to accumulate and assimilate experiential information throughout our lifetimes. However, this predetermined number of neurons is also our Achilles’ heel as any accidental or pathological damage to the CNS often results in irreparable damage to neurons. Consequently, there is a great unmet need for endogenous sources of brain repair, for conditions such as neurodegenerative disorders, cognitive neurological impairments, epilepsy, and cancer. This reason is one of the primary driving forces behind the study of postnatal neurogenesis and it is hoped that once the mechanisms are understood, this process can be harnessed to provide therapeutic avenues for intractable neuropathologies. Consider‐ able progress has been made in the last twenty years to unravel the mechanisms that both define and limit postnatal neurogenesis.