title: Apoptosis of glutamatergic neurons fails to trigger a neurogenic response in the adult neocortex.
abstract: Adult neurogenesis is actively studied in part because of the potential to manipulate endogenous neural stem and progenitor cells for tissue repair. Although constitutive generation of neurons in the adult rodent olfactory bulb and hippocampal dentate gyrus is widely accepted and stroke-induced generation of striatal inhibitory neurons consistently observed, evidence supporting the generation of neurons in the neocortex after neuronal loss remains slim. Nevertheless, a few studies suggested that targeted apoptosis of neocortical glutamatergic neurons could trigger the generation of new ones in the adult brain. In light of such studies, we tested whether apoptosis of glutamatergic cortical neurons using two novel transgenic approaches in mice, an inducible Caspase-8 protein and an inducible diphtheria toxin gene, results in new neurons. After a thorough analysis, no new neurons were detected in the neocortex. Interestingly, an increase in the expression of the neuroblast marker DCX was observed in both models, in some cases in cells with morphologies previously associated with poststroke neuroblasts, but DCX(+) cells coexpressed the oligodendrocyte precursor marker Olig2, suggesting caution when using DCX as a marker for neuroblasts after injury. Given that the adult neocortex lacks an innate potential to regenerate lost glutamatergic neurons, future strategies should concentrate on manipulating the differentiation potential of endogenous or exogenous precursor cells.
authors.affiliation: Department of Genetics, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Diaz
authors.forename: Nicholas
authors.initials: N
authors.lastname: McKeehan
authors.forename: Wenfei
authors.initials: W
authors.lastname: Kang
authors.forename: Jean M
authors.initials: JM
authors.lastname: Hébert
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis; D053181:Caspase 8 / Q000235:genetics; D004167:Diphtheria Toxin / Q000235:genetics; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D005971:Glutamates / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D017628:Microglia / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D019579:Neocortex / Q000502:physiology*; D009410:Nerve Degeneration / Q000235:genetics / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D055495:Neurogenesis / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009479:Neuropeptides / Q000096:biosynthesis; D000076104:Oligodendrocyte Transcription Factor 2; D015854:Up-Regulation
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D053181:Caspase 8; D004167:Diphtheria Toxin; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D005971:Glutamates; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D000076104:Oligodendrocyte Transcription Factor 2; C000714847:Dcx protein, mouse; C512773:Olig2 protein, mouse