title: Non-neurogenic SVZ-like niche in dolphins, mammals devoid of olfaction.
abstract: Adult neurogenesis has been implicated in brain plasticity and brain repair. In mammals, it is mostly restricted to specific brain regions and specific physiological functions. The function and evolutionary history of mammalian adult neurogenesis has been elusive so far. The largest neurogenic site in mammals (subventricular zone, SVZ) generates neurons destined to populate the olfactory bulb. The SVZ neurogenic activity appears to be related to the dependence of the species on olfaction since it occurs at high rates throughout life in animals strongly dependent on this function for their survival. Indeed, it dramatically decreases in humans, who do not depend so much on it. This study investigates whether the SVZ neurogenic site exists in mammals devoid of olfaction and olfactory brain structures, such as dolphins. Our results demonstate that a small SVZ-like region persists in these aquatic mammals. However, this region seems to have lost its neurogenic capabilities since neonatal stages. In addition, instead of the typical newly generated neuroblasts, some mature neurons were observed in the dolphin SVZ. Since cetaceans evolved from terrestrial ancestors, non-neurogenic SVZ may indicate extinction of adult neurogenesis in the absence of olfactory function, with the retention of an SVZ-like anatomical region either vestigial or of still unknown role.
authors.affiliation: Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy.|Department of Veterinary Sciences, University of Turin, Via Leonardo da Vinci, 44, 10095, Grugliasco, TO, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Parolisi
authors.affiliation: Department of Comparative Biomedicine and Food Science, University of Padua, Legnaro, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Cozzi
authors.affiliation: Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy. luca.bonfanti@unito.it.|Department of Veterinary Sciences, University of Turin, Via Leonardo da Vinci, 44, 10095, Grugliasco, TO, Italy. luca.bonfanti@unito.it.
authors.forename: Luca
authors.identifier: http://orcid.org/0000-0002-1469-8898
authors.initials: L
authors.lastname: Bonfanti
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D005075:Biological Evolution; D015415:Biomarkers / Q000032:analysis; D004289:Dolphins / Q000502:physiology*; D005260:Female; D020547:Lateral Ventricles / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D008297:Male; D055495:Neurogenesis; D009473:Neuronal Plasticity; D009474:Neurons / Q000737:chemistry / Q000502:physiology*; D010641:Phenotype; D012903:Smell; D013045:Species Specificity
chemical_list: D015415:Biomarkers
keywords: Adult neurogenesis; Brain plasticity; Cetaceans; Doublecortin; Evolution; Olfactory bulb; Subventricular zone