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Cellular redox states regulate the balance between stem cell maintenance and activation. Increased levels of intracellular reactive oxygen species (ROS) are linked to proliferation and lineage specification. In contrast to this general principle, we here show that in the hippocampus of adult mice, quiescent neural precursor cells (NPCs) maintain the highest ROS levels (hiROS). Classifying NPCs on the basis of cellular ROS content identified distinct functional states. Shifts in ROS content primed cells for a subsequent state transition, with lower ROS content marking proliferative activity and differentiation. Physical activity, a physiological activator of adult hippocampal neurogenesis, recruited hiROS NPCs into proliferation via a transient Nox2-dependent ROS surge. In the absence of Nox2, baseline neurogenesis was unaffected, but the activity-induced increase in proliferation disappeared. These results provide a metabolic classification of NPC functional states and describe a mechanism linking the modulation of cellular ROS by behavioral cues to the activation of adult NPCs., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

MicroRNAs (miRNAs) are short (∼22 nt) single-stranded non-coding RNAs that regulate gene expression at the post-transcriptional level. Over recent years, many studies have extensively characterized the involvement of miRNA-mediated regulation in neurogenesis and brain development. However, a comprehensive catalog of cortical miRNAs expressed in a cell-specific manner in progenitor types of the developing mammalian cortex is still missing. Overcoming this limitation, here we exploited a double reporter mouse line previously validated by our group to allow the identification of the transcriptional signature of neurogenic commitment and provide the field with the complete atlas of miRNA expression in proliferating neural stem cells, neurogenic progenitors and newborn neurons during corticogenesis. By extending the currently known list of miRNAs expressed in the mouse brain by over twofold, our study highlights the power of cell type-specific analyses for the detection of transcripts that would otherwise be diluted out when studying bulk tissues. We further exploited our data by predicting putative miRNAs and validated the power of our approach by providing evidence for the involvement of miR-486 in brain development., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2020. Published by The Company of Biologists Ltd.)

Large-scale RNAi screens are a powerful approach to identify functions of genes in a cell-type-specific manner. For model organisms, genetically identical (isogenic) cells from different cell types are readily available, making comparative studies meaningful. However, large-scale screens in isogenic human primary cells remain challenging. Here, we show that RNAi screens are possible in genetically identical human stem cells, using induced pluripotent stem cells as intermediates. The screens revealed SMARCA4 (SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily A member 4) as a stemness regulator, while balancing differentiation distinctively for each cell type. SMARCA4 knockdown in hematopoietic stem and progenitor cells caused impaired self-renewal in vitro and in vivo with skewed myeloid differentiation; whereas, in neural stem cells, it impaired self-renewal while biasing differentiation toward neural lineage, through combinatorial SWI/SNF subunit assembly. Our findings pose a powerful approach for deciphering human stem cell biology and attribute distinct roles to SMARCA4 in stem cell maintenance., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

The neural stem cell (NSC) reservoir can be harnessed for stem cell-based regenerative therapies. Zebrafish remarkably regenerate their brain by inducing NSC plasticity in a Amyloid-β-42 (Aβ42)-induced experimental Alzheimer's disease (AD) model. Interleukin-4 (IL-4) is also critical for AD-induced NSC proliferation. However, the mechanisms of this response have remained unknown. Using single-cell transcriptomics in the adult zebrafish brain, we identify distinct subtypes of NSCs and neurons and differentially regulated pathways and their gene ontologies and investigate how cell-cell communication is altered through ligand-receptor pairs in AD conditions. Our results propose the existence of heterogeneous and spatially organized stem cell populations that react distinctly to amyloid toxicity. This resource article provides an extensive database for the molecular basis of NSC plasticity in the AD model of the adult zebrafish brain. Further analyses of stem cell heterogeneity and neuro-regenerative ability at single-cell resolution could yield drug targets for mobilizing NSCs for endogenous neuro-regeneration in humans., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Neural stem cells (NSCs) constitute an endogenous reservoir for neurons that could potentially be harnessed for regenerative therapies in disease contexts such as neurodegeneration. However, in Alzheimer's disease (AD), NSCs lose plasticity and thus possible regenerative capacity. We investigate how NSCs lose their plasticity in AD by using starPEG-heparin-based hydrogels to establish a reductionist 3D cell-instructive neuro-microenvironment that promotes the proliferative and neurogenic ability of primary and induced human NSCs. We find that administration of AD-associated Amyloid-β42 causes classical neuropathology and hampers NSC plasticity by inducing kynurenic acid (KYNA) production. Interleukin-4 restores NSC proliferative and neurogenic ability by suppressing the KYNA-producing enzyme Kynurenine aminotransferase (KAT2), which is upregulated in APP/PS1dE9 mouse model of AD and in postmortem human AD brains. Thus, our culture system enables a reductionist investigation of regulation of human NSC plasticity for the identification of potential therapeutic targets for intervention in AD., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Delamination of neural progenitor cells (NPCs) from the ventricular surface is a crucial prerequisite to form the subventricular zone, the germinal layer linked to the expansion of the mammalian neocortex in development and evolution. Here, we dissect the molecular mechanism by which the transcription factor Insm1 promotes the generation of basal progenitors (BPs). Insm1 protein is most highly expressed in newborn BPs in mouse and human developing neocortex. Forced Insm1 expression in embryonic mouse neocortex causes NPC delamination, converting apical to basal radial glia. Insm1 represses the expression of the apical adherens junction belt-specific protein Plekha7. CRISPR/Cas9-mediated disruption of Plekha7 expression suffices to cause NPC delamination. Plekha7 overexpression impedes the intrinsic and counteracts the Insm1-induced, NPC delamination. Our findings uncover a novel molecular mechanism underlying NPC delamination in which a BP-genic transcription factor specifically targets the integrity of the apical adherens junction belt, rather than adherens junction components as such., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Evolutionary expansion of the human neocortex reflects increased amplification of basal progenitors in the subventricular zone, producing more neurons during fetal corticogenesis. In this work, we analyze the transcriptomes of distinct progenitor subpopulations isolated by a cell polarity-based approach from developing mouse and human neocortex. We identify 56 genes preferentially expressed in human apical and basal radial glia that lack mouse orthologs. Among these, ARHGAP11B has the highest degree of radial glia-specific expression. ARHGAP11B arose from partial duplication of ARHGAP11A (which encodes a Rho guanosine triphosphatase-activating protein) on the human lineage after separation from the chimpanzee lineage. Expression of ARHGAP11B in embryonic mouse neocortex promotes basal progenitor generation and self-renewal and can increase cortical plate area and induce gyrification. Hence, ARHGAP11B may have contributed to evolutionary expansion of human neocortex., (Copyright © 2015, American Association for the Advancement of Science.)

Transcriptome analysis of somatic stem cells and their progeny is fundamental to identify new factors controlling proliferation versus differentiation during tissue formation. Here, we generated a combinatorial, fluorescent reporter mouse line to isolate proliferating neural stem cells, differentiating progenitors and newborn neurons that coexist as intermingled cell populations during brain development. Transcriptome sequencing revealed numerous novel long non-coding (lnc)RNAs and uncharacterized protein-coding transcripts identifying the signature of neurogenic commitment. Importantly, most lncRNAs overlapped neurogenic genes and shared with them a nearly identical expression pattern suggesting that lncRNAs control corticogenesis by tuning the expression of nearby cell fate determinants. We assessed the power of our approach by manipulating lncRNAs and protein-coding transcripts with no function in corticogenesis reported to date. This led to several evident phenotypes in neurogenic commitment and neuronal survival, indicating that our study provides a remarkably high number of uncharacterized transcripts with hitherto unsuspected roles in brain development. Finally, we focussed on one lncRNA, Miat, whose manipulation was found to trigger pleiotropic effects on brain development and aberrant splicing of Wnt7b. Hence, our study suggests that lncRNA-mediated alternative splicing of cell fate determinants controls stem-cell commitment during neurogenesis.

MicroRNAs (miRNAs) are short (~22 nt) single-stranded non-coding RNAs that regulate gene expression at the post-transcriptional level. Over the past years, many studies have extensively characterized the involvement of miRNA-mediated regulation in neurogenesis and brain development. However, a comprehensive catalog of cortical miRNAs cell-specifically expressed in progenitor types of the developing mammalian cortex is still missing. Overcoming this limitation, here we exploited a double reporter mouse line previously validated by our group to allow the identification of the transcriptional signature to neurogenic commitment and provide the field with the complete atlas of miRNAs expression in proliferating neural stem cells, neurogenic progenitors and newborn neurons during corticogenesis. By extending the currently known list of miRNAs expressed in the mouse brain by over two fold, our study highlights the power of cell type-specific analyses for the detection of transcripts that would otherwise be diluted out when studying bulk tissues. We further exploited our data by predicting putative novel miRNAs and validated the power of our approach by providing novel evidence for the involvement of miR-486 as a novel player in brain development. [ABSTRACT FROM AUTHOR]

Zebrafish display widespread and pronounced adult neurogenesis, which is fundamental for their regeneration capability after central nervous system injury. However, the cellular identity and the biological properties of adult newborn neurons are elusive for most brain areas. Here, we have used short-term lineage tracing of radial glia progeny to prospectively isolate newborn neurons from the her4.1+ radial glia lineage in the homeostatic adult forebrain. Transcriptome analysis of radial glia, newborn neurons and mature neurons using single cell sequencing identified distinct transcriptional profiles, including novel markers for each population. Specifically, we detected two separate newborn neuron types, which showed diversity of cell fate commitment and location. Further analyses showed that these cell types are homologous to neurogenic cells in the mammalian brain, identified neurogenic commitment in proliferating radial glia and indicated that glutamatergic projection neurons are generated in the adult zebrafish telencephalon. Thus, we prospectively isolated adult newborn neurons from the adult zebrafish forebrain, identified markers for newborn and mature neurons in the adult brain, and revealed intrinsic heterogeneity among adult newborn neurons and their homology with mammalian adult neurogenic cell types. [ABSTRACT FROM AUTHOR]

Major efforts are invested to characterize the factors controlling the proliferation of neural stem cells. During mammalian corticogenesis, our group has identified a small pool of genes that are transiently downregulated in the switch of neural stem cells to neurogenic division and reinduced in newborn neurons. Among these switch genes, we found Tox, a transcription factor with hitherto uncharacterized roles in the nervous system. Here, we investigated the role of Tox in corticogenesis by characterizing its expression at the tissue, cellular and temporal level. We found that Tox is regulated by calcineurin/Nfat signalling. Moreover, we combined DNA adenine methyltransferase identification (DamID) with deep sequencing to characterize the chromatin binding properties of Tox including its motif and downstream transcriptional targets including Sox2, Tbr2, Prox1 and other key factors. Finally, we manipulated Tox in the developing brain and validated its multiple roles in promoting neural stem cell proliferation and neurite outgrowth of newborn neurons. Our data provide a valuable resource to study the role of Tox in other tissues and highlight a novel key player in brain development. [ABSTRACT FROM AUTHOR]