This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 Running title: Beneficial and detrimental outcomes of astrogliosis after central nervous system injury. Abbreviations:Ado, adenosine; AMPA, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate; AP1, activator protein1; AQP, acquaporin; BBB, blood-brain barrier; BDNF, brain-derived growth factor; bFGF, basic fibroblast growth factor; bHLH, basic helix loop helix; BMP, bone morphogenetic protein; CNS, central nervous system; CNTF, ciliary neurotrophic factor;COX-2, cyclooxigenase-2; CREB, cAMP response element binding; CSPGs, chondroitinsulphate proteoglycans; ERK, extracellular signal-regulated kinase; EGF, epidermal growth factor; Eph4A, ephrin 4A; Epo, erythropoietin; ET1, Endothelin 1; ET-R, endothelin receptor; GABA, gamma-aminobutyric acid; GDNF, glial cell-line derived neurotropic factor; GF, growth factor; GFAP, glial fibrillary acidic protein; GLAST, glutamate aspartate transporter; GLT1, glutamate transporter 1; GS, glutamine synthase; IFN , interferon-beta; IFNγ, interferon gamma; IGF1, insulin growth factor1; IL1β, interleukin 1 beta; IL2, interleukin 2; IL6, interleukin 6; IL10, interleukin 10; JAK, Janus protein tyrosine kinases; Lcn2, Lipocalin 2; MAPK, mitogen-activated protein kinase; MMP, matrix metalloprotease; mTOR, mammalian target of rapamycin; NFAT, nuclear factor of activated T cell; NFkB, nuclear factor kappa B; NGF, nerve growth factor; NT3, neurotrophin 3; p38MAPK, p38 mitogen-activated protein kinase; PTEN, phosphatase and tensin homolog; SOCS, suppressor of cytokine signaling; SOD, superoxide dismutase; STAT, signal transducers and activators of transcription; TGFα, transforming growth factor alpha;TGFβ, transforming growth factor beta; TNFα, tumor necrosis factor alpha; VCAM1, vascular cell adhesion molecule-1; VEGF, vascular endothelial growth factor. Page 4 of 63A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 4...

In the adult brain, subsets of astrocytic cells residing in well-defined neurogenic niches constitutively generate neurons throughout life. Brain lesions can stimulate neurogenesis in otherwise non-neurogenic regions, but whether local astrocytic cells generate neurons in these conditions is unresolved. Here, through genetic and viral lineage tracing in mice, we demonstrate that striatal astrocytes become neurogenic following an acute excitotoxic lesion. Similar to astrocytes of adult germinal niches, these activated parenchymal progenitors express nestin and generate neurons through the formation of transit amplifying progenitors. These results shed new light on the neurogenic potential of the adult brain parenchyma.

SUMMARYMulti-lineage neuronal, astrocytic and oligodendrocytic potential is considered a neural stem cell (NSC) trait. However, hippocampal NSCs generate neurons and astrocytes but not oligodendrocytes in vivo and how this is regulated is unknown. Here we show that the RNAseIII Drosha is an intrinsic regulator of stem cell maintenance and differentiation in the adult mouse hippocampus. Inactivation of Drosha results in exhaustion of the NSC pool, premature arrest of neurogenesis, and induction of oligodendrocyte fate commitment. Drosha silences Nuclear Factor IB (NFIB) in hippocampal NSCs by targeting a double-stranded hairpin in the NFIB mRNA, thereby repressing its expression in a Dicer and miRNA-independent manner. We show that NFIB is required and sufficient for oligodendrocyte fate and knockdown of NFIB rescues neurogenesis by Drosha-deficient hippocampal NSCs. Our findings reveal a novel mechanism for stem cell maintenance and oligodendrocyte fate restriction in the adult hippocampus.3

Cerebellar GABAergic interneurons in mouse comprise multiple subsets of morphologically and neurochemically distinct phenotypes located at strategic nodes of cerebellar local circuits. These cells are produced by common progenitors deriving from the ventricular epithelium during embryogenesis and from the prospective white matter (PWM) during postnatal development. However, it is not clear whether these progenitors are also shared by other cerebellar lineages and whether germinative sites different from the PWM originate inhibitory interneurons. Indeed, the postnatal cerebellum hosts another germinal site along the Purkinje cell layer (PCL), in which Bergmann glia are generated up to first the postnatal weeks, which was proposed to be neurogenic. Both PCL and PWM comprise precursors displaying traits of juvenile astroglia and neural stem cell markers. First, we examine the proliferative and fate potential of these niches, showing that different proliferative dynamics regulate progenitor amplification at these sites. In addition, PCL and PWM differ in the generated progeny. GABAergic interneurons are produced exclusively by PWM astroglial-like progenitors, whereas PCL precursors produce only astrocytes. Finally, through in vitro, ex vivo, and in vivo clonal analyses we provide evidence that the postnatal PWM hosts a bipotent progenitor that gives rise to both interneurons and white matter astrocytes.