title: Evidence of functional duplicity of Nestin expression in the adult mouse midbrain.
abstract: Whether or not neurogenesis occurs in the adult substantia nigra pars compacta (SNc) is an important question relevant for developing better treatments for the motor symptoms of Parkinson's disease (PD). Although controversial, it is generally believed that dividing cells here remain undifferentiated or differentiate into glia, not neurons. However, there is a suggestion that Nestin-expressing neural precursor cells (NPCs) in the adult SNc have a propensity to differentiate into neurons, which we sought to confirm in the present study. Adult (>8-weeks old) transgenic NesCreERT2/GtROSA or NesCreERT2/R26eYFP mice were used to permanently label Nestin-expressing cells and their progeny with β-galactosidase (β-gal) or enhanced yellow fluorescent protein (eYFP), respectively. Most β-gal+ or eYFP+ cells were found in the ependymal lining of the midbrain aqueduct (Aq) and in the midline ventral to Aq. Smaller but significant numbers were in the periaqueductal gray (PAG), the ventral tegmental area (VTA), and in SNc. Low-level basal proliferation was evidenced by a modest increase in number of β-gal+ or eYFP+ cells over time, fewer β-gal+ or eYFP+ cells when mice were administered the anti-mitotic agent Cytarabine, and incorporation of the proliferation marker bromodeoxyuridine (BrdU) in a very small number of β-gal+ cells. No evidence of migration was found, including no immunoreactivity against the migration markers doublecortin (DCX) or polysialic acid neural cell adhesion molecule (PSA-NCAM), and no dispersal of β-gal+ or eYFP+ cells through the midbrain parenchyma over time. However, β-gal+ or eYFP+ cells did increase in size and express higher levels of mature neuronal genes over time, indicating growth and neuronal differentiation. In mice whose SNc dopamine neurons had been depleted with 6-hydroxy-dopamine, a model of PD, there were ~2-fold more β-gal+ cells in SNc specifically, although the proportion that were also NeuN+ was not affected. Remarkably, as early as 4days following putative Nestin-expression, many β-gal+ or eYFP+ cells had mature neuronal morphology and were NeuN+. Furthermore, mature neuronal β-gal+ cells were immunoreactive against the self-renewal or pluripotency marker sex determining region Y-box 2 (Sox2). Overall, our data support the notion that some Nestin-expressing, presumably NPCs, have a limited capacity for proliferation, no capacity for migration, and a propensity to generate new neurons within the microenvironment of the adult midbrain. However, our data also suggest that significant numbers of extant midbrain neurons express Nestin and other classical neurogenesis markers in contexts that are presumably not neurogenic. These findings foreshadow duplicitous roles for Nestin and other molecules that are traditionally associated with neurogenesis in the adult midbrain, which should be considered in future PD research.
authors.affiliation: Florey Institute for Neuroscience & Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Parisa
authors.initials: P
authors.lastname: Farzanehfar
authors.affiliation: Florey Institute for Neuroscience & Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Shi Sheng
authors.initials: SS
authors.lastname: Lu
authors.affiliation: Florey Institute for Neuroscience & Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Anupa
authors.initials: A
authors.lastname: Dey
authors.affiliation: Florey Institute for Neuroscience & Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Dharshani
authors.initials: D
authors.lastname: Musiienko
authors.affiliation: Florey Institute for Neuroscience & Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Hamzah
authors.initials: H
authors.lastname: Baagil
authors.affiliation: Florey Institute for Neuroscience & Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Malcolm K
authors.initials: MK
authors.lastname: Horne
authors.affiliation: Florey Institute for Neuroscience & Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia. Electronic address: taumann@unimelb.edu.au.
authors.forename: Tim D
authors.initials: TD
authors.lastname: Aumann
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D059290:Dopaminergic Neurons / Q000378:metabolism; D000089662:Doublecortin Protein; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008636:Mesencephalon / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000378:metabolism; D064231:Nestin / Q000235:genetics / Q000378:metabolism*; D055495:Neurogenesis; D009687:Nuclear Proteins / Q000378:metabolism; D065842:Pars Compacta / Q000378:metabolism; D055748:SOXB1 Transcription Factors / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C000714847:Dcx protein, mouse; D000089662:Doublecortin Protein; D008164:Luminescent Proteins; D009419:Nerve Tissue Proteins; D064231:Nestin; C492380:NeuN protein, mouse; D009687:Nuclear Proteins; D055748:SOXB1 Transcription Factors; C527783:Sox2 protein, mouse; C054562:yellow fluorescent protein, Bacteria; D001616:beta-Galactosidase
keywords: Adult neurogenesis; Dopamine; Parkinson's disease; Substantia nigra