title: Noncanonical Sites of Adult Neurogenesis in the Mammalian Brain.
abstract: Two decades after the discovery that neural stem cells (NSCs) populate some regions of the mammalian central nervous system (CNS), deep knowledge has been accumulated on their capacity to generate new neurons in the adult brain. This constitutive adult neurogenesis occurs throughout life primarily within remnants of the embryonic germinal layers known as "neurogenic sites." Nevertheless, some processes of neurogliogenesis also occur in the CNS parenchyma commonly considered as "nonneurogenic." This "noncanonical" cell genesis has been the object of many claims, some of which turned out to be not true. Indeed, it is often an "incomplete" process as to its final outcome, heterogeneous by several measures, including regional location, progenitor identity, and fate of the progeny. These aspects also strictly depend on the animal species, suggesting that persistent neurogenic processes have uniquely adapted to the brain anatomy of different mammals. Whereas some examples of noncanonical neurogenesis are strictly parenchymal, others also show stem cell niche-like features and a strong link with the ventricular cavities. This work will review results obtained in a research field that expanded from classic neurogenesis studies involving a variety of areas of the CNS outside of the subventricular zone (SVZ) and subgranular zone (SGZ). It will be highlighted how knowledge concerning noncanonical neurogenic areas is still incomplete owing to its regional and species-specific heterogeneity, and to objective difficulties still hampering its full identification and characterization.
authors.affiliation: Department of Biological Sciences, Clemson University, Clemson, South Carolina 29634.
authors.forename: David M
authors.initials: DM
authors.lastname: Feliciano
authors.affiliation: Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06510 Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
authors.forename: Angélique
authors.initials: A
authors.lastname: Bordey
authors.affiliation: Department of Veterinary Sciences, University of Turin 10095, Italy Neuroscience Institute Cavalieri-Ottolenghi (NICO), University of Turin 10043, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Bonfanti
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology* / Q000502:physiology*; D049109:Cell Proliferation; D002874:Chromosome Mapping; D006801:Humans; D007031:Hypothalamus / Q000473:pathology; D020547:Lateral Ventricles / Q000502:physiology; D058953:Neural Stem Cells / Q000502:physiology*; D055495:Neurogenesis / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology