A Common Embryonic Origin of Stem Cells Drives Developmental and Adult Neurogenesis

Repetitive traumatic brain injury-induced complement C1-related inflammation impairs long-term hippocampal neurogenesis

JOURNAL/nrgr/04.03/01300535-202503000-00027/figure1/v/2024-06-17T092413Z/r/image-tiff Repetitive traumatic brain injury impacts adult neurogenesis in the hippocampal dentate gyrus, leading to long-term cognitive impairment. However, the mechanism underlying this neurogenesis impairment remains unknown. In this study, we established a male mouse model of repetitive traumatic brain injury and performed long-term evaluation of neurogenesis of the hippocampal dentate gyrus after repetitive traumatic brain injury. Our results showed that repetitive traumatic brain injury inhibited neural stem cell proliferation and development, delayed neuronal maturation, and reduced the complexity of neuronal dendrites and spines. Mice with repetitive traumatic brain injuryalso showed deficits in spatial memory retrieval. Moreover, following repetitive traumatic brain injury, neuroinflammation was enhanced in the neurogenesis microenvironment where C1q levels were increased, C1q binding protein levels were decreased, and canonical Wnt/β-catenin signaling was downregulated. An inhibitor of C1 reversed the long-term impairment of neurogenesis induced by repetitive traumatic brain injury and improved neurological function. These findings suggest that repetitive traumatic brain injury-induced C1-related inflammation impairs long-term neurogenesis in the dentate gyrus and contributes to spatial memory retrieval dysfunction.

Differentiation stage-specific expression of transcriptional regulators for epithelial mesenchymal transition in dentate granule progenitors

During the development of the mouse dentate gyrus (DG), granule neuronal progenitors (GNPs) arise from glial fibrillary acidic protein (GFAP)-expressing neural stem cells in the dentate notch. However, the transcriptional regulators that control their stepwise differentiation remain poorly defined. Since neurogenesis involves epithelial-to-mesenchymal transition (EMT)-like processes, we investigated the spatio-temporal expression profiles of the EMT transcription factors Zeb1, Scratch2 (Scrt2) and Nkx6-2 in relation to known GNP markers. Our results show that Zeb1 and Scrt2 exhibit sequential, but partially overlapping expression across embryonic and postnatal stages of GNP differentiation. Zeb1 is highly enriched in gfap-GFP+/Sox2+ neural stem/progenitor pools and subsets of Tbr2+/Prox1+/NeuroD+ intermediate GNPs, whereas Scrt2 predominates in Tbr2+/Prox1+/NeuroD+ GNPs. Strikingly, the neuronal EMT regulator Nkx6-2 shows selective expression in postnatal Tbr2+/Prox1+ GNPs, but it is excluded from embryonic counterparts. This temporally coordinated yet distinct expression of Zeb1, Scrt2 and Nkx6-2 reveals discrete transcriptional programs orchestrating GNP differentiation and neurogenic progression at embryonic versus postnatal stages of DG neurogenesis.

Single Cell Transcriptomics-Informed Induced Pluripotent Stem Cells Differentiation to Tenogenic Lineage

During vertebrate embryogenesis, axial tendons develop from the paraxial mesoderm and differentiate through specific developmental stages to reach the syndetome stage. While the main roles of signaling pathways in the earlier stages of the differentiation have been well established, pathway nuances in syndetome specification from the sclerotome stage have yet to be explored. Here, we show stepwise differentiation of human iPSCs to the syndetome stage using chemically defined media and small molecules that were modified based on single cell RNA-sequencing and pathway analysis. We identified a significant population of branching off-target cells differentiating towards a neural phenotype overexpressing Wnt. Further transcriptomics post-addition of a WNT inhibitor at the somite stage and onwards revealed not only total removal of the neural off-target cells, but also increased syndetome induction efficiency. Fine-tuning tendon differentiation in vitro is essential to address the current challenges in developing a successful cell-based tendon therapy.

Epigenetic maintenance of adult neural stem cell quiescence in the mouse hippocampus via Setd1a

Quiescence, a hallmark of adult neural stem cells (NSCs), is required for maintaining the NSC pool to support life-long continuous neurogenesis in the adult dentate gyrus (DG). Whether long-lasting epigenetic modifications maintain NSC quiescence over the long term in the adult DG is not well-understood. Here we show that mice with haploinsufficiency of Setd1a, a schizophrenia risk gene encoding a histone H3K4 methyltransferase, develop an enlarged DG with more dentate granule cells after young adulthood. Deletion of Setd1a specifically in quiescent NSCs in the adult DG promotes their activation and neurogenesis, which is countered by inhibition of the histone demethylase LSD1. Mechanistically, RNA-sequencing and CUT & RUN analyses of cultured quiescent adult NSCs reveal Setd1a deletion-induced transcriptional changes and many Setd1a targets, among which down-regulation of Bhlhe40 promotes quiescent NSC activation in the adult DG in vivo. Together, our study reveals a Setd1a-dependent epigenetic mechanism that sustains NSC quiescence in the adult DG.

The integrated stress response promotes neural stem cell survival under conditions of mitochondrial dysfunction in neurodegeneration

Impaired mitochondrial function is a hallmark of aging and a major contributor to neurodegenerative diseases. We have shown that disrupted mitochondrial dynamics typically found in aging alters the fate of neural stem cells (NSCs) leading to impairments in learning and memory. At present, little is known regarding the mechanisms by which neural stem and progenitor cells survive and adapt to mitochondrial dysfunction. Using Opa1-inducible knockout as a model of aging and neurodegeneration, we identify a decline in neurogenesis due to impaired stem cell activation and progenitor proliferation, which can be rescued by the mitigation of oxidative stress through hypoxia. Through sc-RNA-seq, we identify the ATF4 pathway as a critical mechanism underlying cellular adaptation to metabolic stress. ATF4 knockdown in Opa1-deficient NSCs accelerates cell death, while the increased expression of ATF4 enhances proliferation and survival. Using a Slc7a11 mutant, an ATF4 target, we show that ATF4-mediated glutathione production plays a critical role in maintaining NSC survival and function under stress conditions. Together, we show that the activation of the integrated stress response (ISR) pathway enables NSCs to adapt to metabolic stress due to mitochondrial dysfunction and metabolic stress and may serve as a therapeutic target to enhance NSC survival and function in aging and neurodegeneration.

Autocrine VEGF drives neural stem cell proximity to the adult hippocampus vascular niche

The vasculature is a key component of adult brain neural stem cell (NSC) niches. In the adult mammalian hippocampus, NSCs reside in close contact with a dense capillary network. How this niche is maintained is unclear. We recently found that adult hippocampal NSCs express VEGF, a soluble factor with chemoattractive properties for vascular endothelia. Here, we show that global and NSC-specific VEGF loss led to dissociation of NSCs and their intermediate progenitor daughter cells from local vasculature. Surprisingly, though, we found no changes in local vascular density. Instead, we found that NSC-derived VEGF supports maintenance of gene expression programs in NSCs and their progeny related to cell migration and adhesion. In vitro assays revealed that blockade of VEGF receptor 2 impaired NSC motility and adhesion. Our findings suggest that NSCs maintain their own proximity to vasculature via self-stimulated VEGF signaling that supports their motility towards and/or adhesion to local blood vessels.

Role of histone modifications in neurogenesis and neurodegenerative disease development

Progressive neuronal dysfunction and death are key features of neurodegenerative diseases; therefore, promoting neurogenesis in neurodegenerative diseases is crucial. With advancements in proteomics and high-throughput sequencing technology, it has been demonstrated that histone post-transcriptional modifications (PTMs) are often altered during neurogenesis when the brain is affected by disease or external stimuli and that the degree of histone modification is closely associated with the development of neurodegenerative diseases. This review aimed to show the regulatory role of histone modifications in neurogenesis and neurodegenerative diseases by discussing the changing patterns and functional significance of histone modifications, including histone methylation, acetylation, ubiquitination, phosphorylation, and lactylation. Finally, we explored the control of neurogenesis and the development of neurodegenerative diseases by artificially modulating histone modifications.

Molecular cascade reveals sequential milestones underlying hippocampal neural stem cell development into an adult state

Quiescent adult neural stem cells (NSCs) in the mammalian brain arise from proliferating NSCs during development. Beyond acquisition of quiescence, an adult NSC hallmark, little is known about the process, milestones, and mechanisms underlying the transition of developmental NSCs to an adult NSC state. Here, we performed targeted single-cell RNA-seq analysis to reveal the molecular cascade underlying NSC development in the early postnatal mouse dentate gyrus. We identified two sequential steps, first a transition to quiescence followed by further maturation, each of which involved distinct changes in metabolic gene expression. Direct metabolic analysis uncovered distinct milestones, including an autophagy burst before NSC quiescence acquisition and cellular reactive oxygen species level elevation along NSC maturation. Functionally, autophagy is important for the NSC transition to quiescence during early postnatal development. Together, our study reveals a multi-step process with defined milestones underlying establishment of the adult NSC pool in the mammalian brain.

SAFB regulates hippocampal stem cell fate by targeting Drosha to destabilize Nfib mRNA

Neural stem cells (NSCs) are multipotent and correct fate determination is crucial to guarantee brain formation and homeostasis. How NSCs are instructed to generate neuronal or glial progeny is not well understood. Here, we addressed how murine adult hippocampal NSC fate is regulated and described how scaffold attachment factor B (SAFB) blocks oligodendrocyte production to enable neuron generation. We found that SAFB prevents NSC expression of the transcription factor nuclear factor I/B (NFIB) by binding to sequences in the Nfib mRNA and enhancing Drosha-dependent cleavage of the transcripts. We show that increasing SAFB expression prevents oligodendrocyte production by multipotent adult NSCs, and conditional deletion of Safb increases NFIB expression and oligodendrocyte formation in the adult hippocampus. Our results provide novel insights into a mechanism that controls Drosha functions for selective regulation of NSC fate by modulating the post-transcriptional destabilization of Nfib mRNA in a lineage-specific manner.

Transcriptional control of neural stem cell activity

In the adult brain, neural stem cells (NSCs) are under the control of various molecular mechanisms to produce an appropriate number of neurons that are essential for specific brain functions. Usually, the majority of adult NSCs stay in a non-proliferative and undifferentiated state known as quiescence, occasionally transitioning to an active state to produce newborn neurons. This transition between the quiescent and active states is crucial for the activity of NSCs. Another significant state of adult NSCs is senescence, in which quiescent cells become more dormant and less reactive, ceasing the production of newborn neurons. Although many genes involved in the regulation of NSCs have been identified using genetic manipulation and omics analyses, the entire regulatory network is complicated and ambiguous. In this review, we focus on transcription factors, whose importance has been elucidated in NSCs by knockout or overexpression studies. We mainly discuss the transcription factors with roles in the active, quiescent, and rejuvenation states of adult NSCs.

Identity and nature of neural stem cells in the adult human subventricular zone

The existence of neural stem cells (NSCs) in adult human brain neurogenic regions remains unresolved. To address this, we created a cell atlas of the adult human subventricular zone (SVZ) derived from fresh neurosurgical samples using single-cell transcriptomics. We discovered 2 adult radial glia (RG)-like populations, aRG1 and aRG2. aRG1 shared features with fetal early RG (eRG) and aRG2 were transcriptomically similar to fetal outer RG (oRG). We also captured early neuronal and oligodendrocytic NSC states. We found that the biological programs driven by their transcriptomes support their roles as early lineage NSCs. Finally, we show that these NSCs have the potential to transition between states and along lineage trajectories. These data reveal that multipotent NSCs reside in the adult human SVZ.

Deciphering molecular heterogeneity and dynamics of human hippocampal neural stem cells at different ages and injury states

While accumulated publications support the existence of neurogenesis in the adult human hippocampus, the homeostasis and developmental potentials of neural stem cells (NSCs) under different contexts remain unclear. Based on our generated single-nucleus atlas of the human hippocampus across neonatal, adult, aging, and injury, we dissected the molecular heterogeneity and transcriptional dynamics of human hippocampal NSCs under different contexts. We further identified new specific neurogenic lineage markers that overcome the lack of specificity found in some well-known markers. Based on developmental trajectory and molecular signatures, we found that a subset of NSCs exhibit quiescent properties after birth, and most NSCs become deep quiescence during aging. Furthermore, certain deep quiescent NSCs are reactivated following stroke injury. Together, our findings provide valuable insights into the development, aging, and reactivation of the human hippocampal NSCs, and help to explain why adult hippocampal neurogenesis is infrequently observed in humans.

Prosaposin maintains adult neural stem cells in a state associated with deep quiescence

In most vertebrates, adult neural stem cells (NSCs) continuously give rise to neurons in discrete brain regions. A critical process for maintaining NSC pools over long periods of time in the adult brain is NSC quiescence, a reversible and tightly regulated state of cell-cycle arrest. Recently, lysosomes were identified to regulate the NSC quiescence-proliferation balance. However, it remains controversial whether lysosomal activity promotes NSC proliferation or quiescence, and a finer influence of lysosomal activity on NSC quiescence duration or depth remains unexplored. Using RNA sequencing and pharmacological manipulations, we show that lysosomes are necessary for NSC quiescence maintenance. In addition, we reveal that expression of psap, encoding the lysosomal regulator Prosaposin, is enriched in quiescent NSCs (qNSCs) that reside upstream in the NSC lineage and display a deep/long quiescence phase in the adult zebrafish telencephalon. We show that shRNA-mediated psap knockdown increases the proportion of activated NSCs (aNSCs) as well as NSCs that reside in shallower quiescence states (signed by ascl1a and deltaA expression). Collectively, our results identify the lysosomal protein Psap as a (direct or indirect) quiescence regulator and unfold the interplay between lysosomal function and NSC quiescence heterogeneities.

Evaluation of specific RBE in different cells of hippocampus under high-dose proton irradiation in rats

The study aimed to determine the specific relative biological effectiveness (RBE) of various cells in the hippocampus following proton irradiation. Sixty Sprague-Dawley rats were randomly allocated to 5 groups receiving 20 or 30 Gy of proton or photon irradiation. Pathomorphological neuronal damage in the hippocampus was assessed using Hematoxylin-eosin (HE) staining. The expression level of NeuN, Nestin, Caspase-3, Olig2, CD68 and CD45 were determined by immunohistochemistry (IHC). The RBE range established by comparing the effects of proton and photon irradiation at equivalent biological outcomes. Proton20Gy induced more severe damage to neurons than photon20Gy, but showed no difference compared to photon30Gy. The RBE of neuron was determined to be 1.65. Similarly, both proton20Gy and proton30Gy resulted in more inhibition of oligodendrocytes and activation of microglia in the hippocampal regions than photon20Gy and photon30Gy. However, the expression of Olig2 was higher and CD68 was lower in the proton20Gy group than in the photon30Gy group. The RBE of oligodendrocyte and microglia was estimated to be between 1.1 to 1.65. For neural stem cells (NSCs) and immune cells, there were no significant difference in the expression of Nestin and CD45 between proton and photon irradiation (both 20 and 30 Gy). Therefore, the RBE for NSCs and immune cell was determined to be 1.1. These findings highlight the varying RBE values of different cells in the hippocampus in vivo. Moreover, the actual RBE of the hippocampus may be higher than 1.1, suggesting that using as RBE value of 1.1 in clinical practice may underestimate the toxicities induced by proton radiation.

Lifelong persistence of nuclear RNAs in the mouse brain

Genomic DNA that resides in the nuclei of mammalian neurons can be as old as the organism itself. The life span of nuclear RNAs, which are critical for proper chromatin architecture and transcription regulation, has not been determined in adult tissues. In this work, we identified and characterized nuclear RNAs that do not turn over for at least 2 years in a subset of postnatally born cells in the mouse brain. These long-lived RNAs were stably retained in nuclei in a neural cell type-specific manner and were required for the maintenance of heterochromatin. Thus, the life span of neural cells may depend on both the molecular longevity of DNA for the storage of genetic information and also the extreme stability of RNA for the functional organization of chromatin.

From Vessels to Neurons-The Role of Hypoxia Pathway Proteins in Embryonic Neurogenesis

Embryonic neurogenesis can be defined as a period of prenatal development during which divisions of neural stem and progenitor cells give rise to neurons. In the central nervous system of most mammals, including humans, the majority of neocortical neurogenesis occurs before birth. It is a highly spatiotemporally organized process whose perturbations lead to cortical malformations and dysfunctions underlying neurological and psychiatric pathologies, and in which oxygen availability plays a critical role. In case of deprived oxygen conditions, known as hypoxia, the hypoxia-inducible factor (HIF) signaling pathway is activated, resulting in the selective expression of a group of genes that regulate homeostatic adaptations, including cell differentiation and survival, metabolism and angiogenesis. While a physiological degree of hypoxia is essential for proper brain development, imbalanced oxygen levels can adversely affect this process, as observed in common obstetrical pathologies such as prematurity. This review comprehensively explores and discusses the current body of knowledge regarding the role of hypoxia and the HIF pathway in embryonic neurogenesis of the mammalian cortex. Additionally, it highlights existing gaps in our understanding, presents unanswered questions, and provides avenues for future research.

Deubiquitinase Mysm1 regulates neural stem cell proliferation and differentiation by controlling Id4 expression

Neural stem cells (NSCs) are critical for brain development and maintenance of neurogenesis. However, the molecular mechanisms that regulate NSC proliferation and differentiation remain unclear. Mysm1 is a deubiquitinase and is essential for the self-renewal and differentiation of several stem cells. It is unknown whether Mysm1 plays an important role in NSCs. Here, we found that Mysm1 was expressed in NSCs and its expression was increased with age in mice. Mice with Mysm1 knockdown by crossing Mysm1 floxed mice with Nestin-Cre mice exhibited abnormal brain development with microcephaly. Mysm1 deletion promoted NSC proliferation and apoptosis, resulting in depletion of the stem cell pool. In addition, Mysm1-deficient NSCs skewed toward neurogenesis instead of astrogliogenesis. Mechanistic investigations with RNA sequencing and genome-wide CUT&Tag analysis revealed that Mysm1 epigenetically regulated Id4 transcription by regulating histone modification at the promoter region. After rescuing the expression of Id4, the hyperproliferation and imbalance differentiation of Mysm1-deficient NSCs was reversed. Additionally, knockdown Mysm1 in aged mice could promote NSC proliferation. Collectively, the present study identified a new factor Mysm1 which is essential for NSC homeostasis and Mysm1-Id4 axis may be an ideal target for proper NSC proliferation and differentiation.

Wnt signal-dependent antero-posterior specification of early-stage CNS primordia modeled in EpiSC-derived neural stem cells

The specification of the embryonic central nervous system (CNS) into future brain (forebrain, midbrain, or hindbrain) and spinal cord (SC) regions is a critical step of CNS development. A previous chicken embryo study indicated that anterior epiblast cells marked by Sox2 N2 enhancer activity are specified to the respective brain regions during the transition phase of the epiblast to the neural plate-forming neural primordium. The present study showed that the SC precursors positioned posterior to the hindbrain precursors in the anterior epiblast migrated posteriorly in contrast to the anterior migration of brain precursors. The anteroposterior specification of the CNS precursors occurs at an analogous time (∼E7.5) in mouse embryos, in which an anterior-to-posterior incremental gradient of Wnt signal strength was observed. To examine the possible Wnt signal contribution to the anteroposterior CNS primordium specification, we utilized mouse epiblast stem cell (EpiSC)-derived neurogenesis in culture. EpiSCs maintained in an activin- and FGF2-containing medium start neural development after the removal of activin, following a day in a transitory state. We placed activin-free EpiSCs in EGF- and FGF2-containing medium to arrest neural development and expand the cells into neural stem cells (NSCs). Simultaneously, a Wnt antagonist or agonist was added to the culture, with the anticipation that different levels of Wnt signals would act on the transitory cells to specify CNS regionality; then, the Wnt-treated cells were expanded as NSCs. Gene expression profiles of six NSC lines were analyzed using microarrays and single-cell RNA-seq. The NSC lines demonstrated anteroposterior regional specification in response to increasing Wnt signal input levels: forebrain-midbrain-, hindbrain-, cervical SC-, and thoracic SC-like lines. The regional coverage of these NSC lines had a range; for instance, the XN1 line expressed Otx2 and En2, indicating midbrain characteristics, but additionally expressed the SC-characteristic Hoxa5. The ranges in the anteroposterior specification of neural primordia may be narrowed as neural development proceeds. The thoracic SC is presumably the posterior limit of the contribution by anterior epiblast-derived neural progenitors, as the characteristics of more posterior SC regions were not displayed.

Single-cell transcriptome analyses reveal critical regulators of spermatogonial stem cell fate transitions

BACKGROUND

Spermatogonial stem cells (SSCs) are the foundation cells for continual spermatogenesis and germline regeneration in mammals. SSC activities reside in the undifferentiated spermatogonial population, and currently, the molecular identities of SSCs and their committed progenitors remain unclear.

RESULTS

We performed single-cell transcriptome analysis on isolated undifferentiated spermatogonia from mice to decipher the molecular signatures of SSC fate transitions. Through comprehensive analysis, we delineated the developmental trajectory and identified candidate transcription factors (TFs) involved in the fate transitions of SSCs and their progenitors in distinct states. Specifically, we characterized the Asingle spermatogonial subtype marked by the expression of Eomes. Eomes+ cells contained enriched transplantable SSCs, and more than 90% of the cells remained in the quiescent state. Conditional deletion of Eomes in the germline did not impact steady-state spermatogenesis but enhanced SSC regeneration. Forced expression of Eomes in spermatogenic cells disrupted spermatogenesis mainly by affecting the cell cycle progression of undifferentiated spermatogonia. After injury, Eomes+ cells re-enter the cell cycle and divide to expand the SSC pool. Eomes+ cells consisted of 7 different subsets of cells at single-cell resolution, and genes enriched in glycolysis/gluconeogenesis and the PI3/Akt signaling pathway participated in the SSC regeneration process.

CONCLUSIONS

In this study, we explored the molecular characteristics and critical regulators of subpopulations of undifferentiated spermatogonia. The findings of the present study described a quiescent SSC subpopulation, Eomes+ spermatogonia, and provided a dynamic transcriptional map of SSC fate determination.

Generation of adult hippocampal neural stem cells occurs in the early postnatal dentate gyrus and depends on cyclin D2

Lifelong hippocampal neurogenesis is maintained by a pool of multipotent adult neural stem cells (aNSCs) residing in the subgranular zone of the dentate gyrus (DG). The mechanisms guiding transition of NSCs from the developmental to the adult state remain unclear. We show here, by using nestin-based reporter mice deficient for cyclin D2, that the aNSC pool is established through cyclin D2-dependent proliferation during the first two weeks of life. The absence of cyclin D2 does not affect normal development of the dentate gyrus until birth but prevents postnatal formation of radial glia-like aNSCs. Furthermore, retroviral fate mapping reveals that aNSCs are born on-site from precursors located in the dentate gyrus shortly after birth. Taken together, our data identify the critical time window and the spatial location of the precursor divisions that generate the persistent population of aNSCs and demonstrate the central role of cyclin D2 in this process.

HOPX-associated molecular programs control cardiomyocyte cell states underpinning cardiac structure and function

Genomic regulation of cardiomyocyte differentiation is central to heart development and function. This study uses genetic loss-of-function human-induced pluripotent stem cell-derived cardiomyocytes to evaluate the genomic regulatory basis of the non-DNA-binding homeodomain protein HOPX. We show that HOPX interacts with and controls cardiac genes and enhancer networks associated with diverse aspects of heart development. Using perturbation studies in vitro, we define how upstream cell growth and proliferation control HOPX transcription to regulate cardiac gene programs. We then use cell, organoid, and zebrafish regeneration models to demonstrate that HOPX-regulated gene programs control cardiomyocyte function in development and disease. Collectively, this study mechanistically links cell signaling pathways as upstream regulators of HOPX transcription to control gene programs underpinning cardiomyocyte identity and function.

Isolated loss of the AUTS2 long isoform, brain-wide or targeted to Calbindin-lineage cells, generates a specific suite of brain, behavioral, and molecular pathologies

Rearrangements within the AUTS2 region are associated with a rare syndromic disorder with intellectual disability, developmental delay, and behavioral abnormalities as core features. In addition, smaller regional variants are linked to wide range of neuropsychiatric disorders, underscoring the gene's essential role in brain development. Like many essential neurodevelopmental genes, AUTS2 is large and complex, generating distinct long (AUTS2-l) and short (AUTS2-s) protein isoforms from alternative promoters. Although evidence suggests unique isoform functions, the contributions of each isoform to specific AUTS2-linked phenotypes have not been clearly resolved. Furthermore, Auts2 is widely expressed across the developing brain, but cell populations most central to disease presentation have not been determined. In this study, we focused on the specific roles of AUTS2-l in brain development, behavior, and postnatal brain gene expression, showing that brain-wide AUTS2-l ablation leads to specific subsets of the recessive pathologies associated with mutations in 3' exons (exons 8-19) that disrupt both major isoforms. We identify downstream genes that could explain expressed phenotypes including hundreds of putative direct AUTS2-l target genes. Furthermore, in contrast to 3' Auts2 mutations which lead to dominant hypoactivity, AUTS2-l loss-of-function is associated with dominant hyperactivity and repetitive behaviors, phenotypes exhibited by many human patients. Finally, we show that AUTS2-l ablation in Calbindin 1-expressing cell lineages is sufficient to yield learning/memory deficits and hyperactivity with abnormal dentate gyrus granule cell maturation, but not other phenotypic effects. These data provide new clues to in vivo AUTS2-l functions and novel information relevant to genotype-phenotype correlations in the human AUTS2 region.

Dietary Nucleotides Promote Neonatal Rat Microbiota-Gut-Brain Axis Development by Affecting Gut Microbiota Composition and Metabolic Function

A variety of active factors in milk and foods have been proven to serve as microbial nutrients that regulate the formation of early gut microbiota (GM), thereby ensuring the healthy development of infants. This study demonstrated that dietary nucleotides (NTs), one of the main nitrogen-containing substances in human milk, promoted the neurodevelopment of neonatal rats and the expression of Sox2, Dcx, Tuj1, and NeuN in the prefrontal cortex and hippocampus, but had no significant regulatory effects in the striatum. 16s rRNA sequencing and metabolomics of the colon contents of neonatal rats at different developmental stages showed that the early intake of NTs promoted an increase in the abundance of beneficial microorganisms related to neurodevelopment, digestion, and gut absorption, such as g_Romboutsia and g_Akkermansia. Changes in the ability of the GM to regulate folate synthesis, riboflavin metabolism, and other processes were also observed. Further analysis revealed significant correlations between the level of characteristic metabolites, namely, trans-3-indoleacrylic acid, urocanic acid, inosine, and adenosine, in the gut with neurodevelopment and characteristic GM components. These findings suggest that NTs in milk may affect neurodevelopment and maturation in early life by regulating the GM composition-gut-brain axis.

Shh from mossy cells contributes to preventing NSC pool depletion after seizure-induced neurogenesis and in aging

Epileptic seizures induce aberrant neurogenesis from resident neural stem cells (NSCs) in the dentate gyrus of the adult mouse hippocampus, which has been implicated in depletion of the NSC pool and impairment of hippocampal function. However, the mechanisms regulating neurogenesis after seizures remain unknown. Here, we demonstrate that Sonic hedgehog (Shh) from mossy cells is a major source of Shh signaling activity after seizures, by which mossy cells contribute to seizure-induced neurogenesis and maintenance of the NSC pool. Deletion of Shh from mossy cells attenuates seizure-induced neurogenesis. Moreover, in the absence of Shh from mossy cells, NSCs pool are prematurely depleted after seizure-induced proliferation, and NSCs have impaired self-renewal. Likewise, lack of Shh from mossy cells accelerates age-related decline of the NSC pool with accompanying reduction of self-renewal of NSCs outside the context of pathology such as seizures. Together, our findings indicate that Shh from mossy cells is critical to maintain NSCs and to prevent exhaustion from excessive consumption in aging and after seizures.

Homemade: building the structure of the neurogenic niche

Neural stem/progenitor cells live in an intricate cellular environment, the neurogenic niche, which supports their function and enables neurogenesis. The niche is made of a diversity of cell types, including neurons, glia and the vasculature, which are able to signal to and are structurally organised around neural stem/progenitor cells. While the focus has been on how individual cell types signal to and influence the behaviour of neural stem/progenitor cells, very little is actually known on how the niche is assembled during development from multiple cellular origins, and on the role of the resulting topology on these cells. This review proposes to draw a state-of-the art picture of this emerging field of research, with the aim to expose our knowledge on niche architecture and formation from different animal models (mouse, zebrafish and fruit fly). We will span its multiple aspects, from the existence and importance of local, adhesive interactions to the potential emergence of larger-scale topological properties through the careful assembly of diverse cellular and acellular components.

Adult neurogenesis research in China

Neural stem cells are multipotent stem cells that generate functional newborn neurons through a process called neurogenesis. Neurogenesis in the adult brain is tightly regulated and plays a pivotal role in the maintenance of brain function. Disruption of adult neurogenesis impairs cognitive function and is correlated with numerous neurologic disorders. Deciphering the mechanisms underlying adult neurogenesis not only advances our understanding of how the brain functions, but also offers new insight into neurologic diseases and potentially contributes to the development of effective treatments. The field of adult neurogenesis is experiencing significant growth in China. Chinese researchers have demonstrated a multitude of factors governing adult neurogenesis and revealed the underlying mechanisms of and correlations between adult neurogenesis and neurologic disorders. Here, we provide an overview of recent advancements in the field of adult neurogenesis due to Chinese scientists.

Adult human neurogenesis: A view from two schools of thought

Are we truly losing neurons as we grow older? If yes, why, and how can the lost neurons be replaced or compensated for? Is so-called adult neurogenesis (ANG) still a controversial process, particularly in the human cerebral cortex? How do adult-born neurons -if proven to exist- contribute to brain functions? Is adult neurogenesis a disease-relevant process, meaning that neural progenitor cells are dormant in adulthood, but they may be reactivated, for example, following stroke? Is the earnest hope to cure neurological diseases justifying the readiness to accept ANG claim uncritically? These are all fundamental issues that have not yet been firmly explained. Although it is completely understandable that some researchers believe that we can add new neurons to our inevitably deteriorating brain, the brain regeneration process still possesses intellectually and experimentally diverting views, as until now, there has been significant confusion about the concept of ANG. This paper is not intended to be an extensively analytical review distilling all findings and conclusions presented in the ANG literature. Instead, it is an attempt to discuss the commonly entertained opinions and then present our reflective insight concerning the current status quo of the field, which might help redirect research questions, avoid marketing an exaggerated hope, and more importantly, save the ever-limited resources, namely, intellectuals' time, facilities, and grants.

Autophagy drives the conversion of developmental neural stem cells to the adult quiescent state

Neurogenesis in the adult mammalian brain relies on the lifelong persistence of quiescent neural stem cell (NSC) reservoirs. Little is known about the mechanisms that lead to the initial establishment of quiescence, the main hallmark of adult stem cells, during development. Here we show that protein aggregates and autophagy machinery components accumulate in developmental radial glia-like NSCs as they enter quiescence and that pharmacological or genetic blockade of autophagy disrupts quiescence acquisition and maintenance. Conversely, increasing autophagy through AMPK/ULK1 activation instructs the acquisition of the quiescent state without affecting BMP signaling, a gatekeeper of NSC quiescence during adulthood. Selective ablation of Atg7, a critical gene for autophagosome formation, in radial glia-like NSCs at early and late postnatal stages compromises the initial acquisition and maintenance of quiescence during the formation of the hippocampal dentate gyrus NSC niche. Therefore, we demonstrate that autophagy is cell-intrinsically required to establish NSC quiescence during hippocampal development. Our results uncover an important role of autophagy in the transition of developmental NSCs into their dormant adult form, paving the way for studies directed at further understanding the mechanisms of stem cell niche formation and maintenance in the mammalian brain.

Neurogenesis in primates versus rodents and the value of non-human primate models

Neurogenesis, the process of generating neurons from neural stem cells, occurs during both embryonic and adult stages, with each stage possessing distinct characteristics. Dysfunction in either stage can disrupt normal neural development, impair cognitive functions, and lead to various neurological disorders. Recent technological advancements in single-cell multiomics and gene-editing have facilitated investigations into primate neurogenesis. Here, we provide a comprehensive overview of neurogenesis across rodents, non-human primates, and humans, covering embryonic development to adulthood and focusing on the conservation and diversity among species. While non-human primates, especially monkeys, serve as valuable models with closer neural resemblance to humans, we highlight the potential impacts and limitations of non-human primate models on both physiological and pathological neurogenesis research.

Regulation of young-adult neurogenesis and neuronal differentiation by neural cell adhesion molecule 2 (NCAM2)

Adult neurogenesis persists in mammals in the neurogenic zones, where newborn neurons are incorporated into preexisting circuits to preserve and improve learning and memory tasks. Relevant structural elements of the neurogenic niches include the family of cell adhesion molecules (CAMs), which participate in signal transduction and regulate the survival, division, and differentiation of radial glial progenitors (RGPs). Here we analyzed the functions of neural cell adhesion molecule 2 (NCAM2) in the regulation of RGPs in adult neurogenesis and during corticogenesis. We characterized the presence of NCAM2 across the main cell types of the neurogenic process in the dentate gyrus, revealing different levels of NCAM2 amid the progression of RGPs and the formation of neurons. We showed that Ncam2 overexpression in adult mice arrested progenitors in an RGP-like state, affecting the normal course of young-adult neurogenesis. Furthermore, changes in Ncam2 levels during corticogenesis led to transient migratory deficits but did not affect the survival and proliferation of RGPs, suggesting a differential role of NCAM2 in adult and embryonic stages. Our data reinforce the relevance of CAMs in the neurogenic process by revealing a significant role of Ncam2 levels in the regulation of RGPs during young-adult neurogenesis in the hippocampus.

Apical size and deltaA expression predict adult neural stem cell decisions along lineage progression

The maintenance of neural stem cells (NSCs) in the adult brain depends on their activation frequency and division mode. Using long-term intravital imaging of NSCs in the zebrafish adult telencephalon, we reveal that apical surface area and expression of the Notch ligand DeltaA predict these NSC decisions. deltaA-negative NSCs constitute a bona fide self-renewing NSC pool and systematically engage in asymmetric divisions generating a self-renewing deltaAneg daughter, which regains the size and behavior of its mother, and a neurogenic deltaApos daughter, eventually engaged in neuronal production following further quiescence-division phases. Pharmacological and genetic manipulations of Notch, DeltaA, and apical size further show that the prediction of activation frequency by apical size and the asymmetric divisions of deltaAneg NSCs are functionally independent of Notch. These results provide dynamic qualitative and quantitative readouts of NSC lineage progression in vivo and support a hierarchical organization of NSCs in differently fated subpopulations.

Perturbations in neural stem cell function during a neurotropic viral infection in juvenile mice

Viral infections of the central nervous system (CNS) often cause worse neurological outcomes in younger hosts. Throughout childhood, the brain undergoes extensive development and refinement to produce functional neural networks. Network function is maintained partly with the help of neural stem cells (NSCs) that replace neuronal and glia subtypes in the two neurogenic niches of the brain (the hippocampus and subventricular zone). Accumulating evidence suggests that viruses disrupt NSC function in adulthood and infancy, but the in vivo impact of childhood infections on acute and long-term NSC function is unknown. Using a juvenile mouse model of measles virus (MeV) infection, where only mature neurons in the brain are infected, we defined the effects of the antiviral immune response on NSCs from juvenile to adult stages of life. We found that (a) virus persists in the brains of survivors despite an anti-viral immune response; (b) NSC numbers decrease dramatically during early infection, but ultimately stabilize in adult survivors; (c) infection is associated with mild apoptosis throughout the juvenile brain, but NSC proliferation is unchanged; (d) the loss of NSC numbers is dependent upon the stage of NSC differentiation; and (e) immature neurons increase early during infection, concurrent with depletion of NSC pools. Collectively, we show that NSCs are exquisitely sensitive to the inflammatory microenvironment created during neuron-restricted MeV infection in juveniles, responding with an early loss of NSCs but increased neurogenesis. These studies provide insight into potential cellular mechanisms associated with long-term neurological deficits in survivors of childhood CNS infections.

Cell type-specific NRBF2 orchestrates autophagic flux and adult hippocampal neurogenesis in chronic stress-induced depression

Dysfunctional autophagy and impairment of adult hippocampal neurogenesis (AHN) each contribute to the pathogenesis of major depressive disorder (MDD). However, whether dysfunctional autophagy is linked to aberrant AHN underlying MDD remains unclear. Here we demonstrate that the expression of nuclear receptor binding factor 2 (NRBF2), a component of autophagy-associated PIK3C3/VPS34-containing phosphatidylinositol 3-kinase complex, is attenuated in the dentate gyrus (DG) under chronic stress. NRBF2 deficiency inhibits the activity of the VPS34 complex and impairs autophagic flux in adult neural stem cells (aNSCs). Moreover, loss of NRBF2 disrupts the neurogenesis-related protein network and causes exhaustion of aNSC pool, leading to the depression-like phenotype. Strikingly, overexpressing NRBF2 in aNSCs of the DG is sufficient to rescue impaired AHN and depression-like phenotype of mice. Our findings reveal a significant role of NRBF2-dependent autophagy in preventing chronic stress-induced AHN impairment and suggest the therapeutic potential of targeting NRBF2 in MDD treatment.

Shh from mossy cells contributes to preventing NSC pool depletion after seizure-induced neurogenesis and in aging

Epileptic seizures induce aberrant neurogenesis from resident neural stem cells (NSCs) in the dentate gyrus of the adult mouse hippocampus, which has been implicated in depletion of the NSC pool and impairment of hippocampal function. However, the mechanisms regulating neurogenesis after seizures remain unknown. Here we demonstrate that Shh from mossy cells is a major source of Shh signaling activity after seizures, by which mossy cells contribute to seizure-induced neurogenesis and maintenance of the NSC pool. Deletion of Shh from mossy cells attenuates seizure-induced neurogenesis. Moreover, in the absence of Shh from mossy cells, NSCs pool are prematurely depleted after seizure-induced proliferation, and NSCs have impaired self-renewal. Likewise, lack of Shh from mossy cells accelerates age-related decline of the NSC pool with accompanying reduction of self-renewal of NSCs outside the context of pathology such as seizures. Together, our findings indicate that Shh from mossy cells is critical to maintain NSCs and to prevent exhaustion from excessive consumption in aging and after seizures.

Neural stem cell metabolism revisited: a critical role for mitochondria

Metabolism has emerged as a key regulator of stem cell behavior. Mitochondria are crucial metabolic organelles that are important for differentiated cells, yet considered less so for stem cells. However, recent studies have shown that mitochondria influence stem cell maintenance and fate decisions, inviting a revised look at this topic. In this review, we cover the current literature addressing the role of mitochondrial metabolism in mouse and human neural stem cells (NSCs) in the embryonic and adult brain. We summarize how mitochondria are implicated in fate regulation and how substrate oxidation affects NSC quiescence. We further explore single-cell RNA sequencing (scRNA-seq) data for metabolic signatures of adult NSCs, highlight emerging technologies reporting on metabolic signatures, and discuss mitochondrial metabolism in other stem cells.

An integrated single-cell analysis of human adrenal cortex development

The adrenal glands synthesize and release essential steroid hormones such as cortisol and aldosterone, but many aspects of human adrenal gland development are not well understood. Here, we combined single-cell and bulk RNA sequencing, spatial transcriptomics, IHC, and micro-focus computed tomography to investigate key aspects of adrenal development in the first 20 weeks of gestation. We demonstrate rapid adrenal growth and vascularization, with more cell division in the outer definitive zone (DZ). Steroidogenic pathways favored androgen synthesis in the central fetal zone, but DZ capacity to synthesize cortisol and aldosterone developed with time. Core transcriptional regulators were identified, with localized expression of HOPX (also known as Hop homeobox/homeobox-only protein) in the DZ. Potential ligand-receptor interactions between mesenchyme and adrenal cortex were seen (e.g., RSPO3/LGR4). Growth-promoting imprinted genes were enriched in the developing cortex (e.g., IGF2, PEG3). These findings reveal aspects of human adrenal development and have clinical implications for understanding primary adrenal insufficiency and related postnatal adrenal disorders, such as adrenal tumor development, steroid disorders, and neonatal stress.

Mitochondrial GSNOR Alleviates Cardiac Dysfunction via ANT1 Denitrosylation

BACKGROUND

The cardiac-protective role of GSNOR (S-nitrosoglutathione reductase) in the cytoplasm, as a denitrosylase enzyme of S-nitrosylation, has been reported in cardiac remodeling, but whether GSNOR is localized in other organelles and exerts novel effects remains unknown. We aimed to elucidate the effects of mitochondrial GSNOR, a novel subcellular localization of GSNOR, on cardiac remodeling and heart failure (HF).

METHODS

GSNOR subcellular localization was observed by cellular fractionation assay, immunofluorescent staining, and colloidal gold particle staining. Overexpression of GSNOR in mitochondria was achieved by mitochondria-targeting sequence-directed adeno-associated virus 9. Cardiac-specific knockout of GSNOR mice was used to examine the role of GSNOR in HF. S-nitrosylation sites of ANT1 (adenine nucleotide translocase 1) were identified using biotin-switch and liquid chromatography-tandem mass spectrometry.

RESULTS

GSNOR expression was suppressed in cardiac tissues of patients with HF. Consistently, cardiac-specific knockout mice showed aggravated pathological remodeling induced by transverse aortic constriction. We found that GSNOR is also localized in mitochondria. In the angiotensin II-induced hypertrophic cardiomyocytes, mitochondrial GSNOR levels significantly decreased along with mitochondrial functional impairment. Restoration of mitochondrial GSNOR levels in cardiac-specific knockout mice significantly improved mitochondrial function and cardiac performance in transverse aortic constriction-induced HF mice. Mechanistically, we identified ANT1 as a direct target of GSNOR. A decrease in mitochondrial GSNOR under HF leads to an elevation of S-nitrosylation ANT1 at cysteine 160 (C160). In accordance with these findings, overexpression of either mitochondrial GSNOR or ANT1 C160A, non-nitrosylated mutant, significantly improved mitochondrial function, maintained the mitochondrial membrane potential, and upregulated mitophagy.

CONCLUSIONS

We identified a novel species of GSNOR localized in mitochondria and found mitochondrial GSNOR plays an essential role in maintaining mitochondrial homeostasis through ANT1 denitrosylation, which provides a potential novel therapeutic target for HF.

Excitatory amino acid transporter 1 supports adult hippocampal neural stem cell self-renewal

Within the adult mammalian dentate gyrus (DG) of the hippocampus, glutamate stimulates neural stem cell (NSC) self-renewing proliferation, providing a link between adult neurogenesis and local circuit activity. Here, we show that glutamate-induced self-renewal of adult DG NSCs requires glutamate transport via excitatory amino acid transporter 1 (EAAT1) to stimulate lipogenesis. Loss of EAAT1 prevented glutamate-induced self-renewing proliferation of NSCs in vitro and in vivo, with little role evident for canonical glutamate receptors. Transcriptomics and further pathway manipulation revealed that glutamate simulation of NSCs relied on EAAT1 transport-stimulated lipogenesis. Our findings demonstrate a critical, direct role for EAAT1 in stimulating NSCs to support neurogenesis in adulthood, thereby providing insights into a non-canonical mechanism by which NSCs sense and respond to their niche.

Fine-tuned rest: unveiling the regulatory landscape of adult quiescent neural stem cells

Cell quiescence is an essential mechanism that allows cells to temporarily halt proliferation while preserving the potential to resume it at a later time. The molecular mechanisms underlying cell quiescence are complex and involve the regulation of various signaling pathways, transcription factors and epigenetic modifications. The importance of unveiling the mechanisms regulating the quiescent state is undeniable, as its long-term maintenance is key to sustain tissue homeostasis throughout life. Neural stem cells (NSCs) are maintained in the subependymal zone (SEZ) niche of adult mammalian brains mostly as long-lasting quiescent cells, owing to multiple intrinsic and extrinsic cues that actively regulate this state. Differently from other non-proliferative states, quiescence is a reversible and tightly regulated condition that can re-activate to support the formation of new neurons throughout adult lifespan. Decoding its regulatory mechanisms in homeostasis and unveiling how it is modulated in the context of the aged brain or during tumorigenesis, could bring us closer to the development of new potential strategies to intervene in adult neurogenesis with therapeutic purposes. Starting with a general conceptualization of the quiescent state in different stem cell niches, we here review what we have learned about NSC quiescence in the SEZ, encompassing the experimental strategies used for its study, to end up discussing the modulation of quiescence in the context of a physiology or pathological NSC dysregulation.

Chromatin accessibility dynamics of neurogenic niche cells reveal defects in neural stem cell adhesion and migration during aging

The regenerative potential of brain stem cell niches deteriorates during aging. Yet the mechanisms underlying this decline are largely unknown. Here we characterize genome-wide chromatin accessibility of neurogenic niche cells in vivo during aging. Interestingly, chromatin accessibility at adhesion and migration genes decreases with age in quiescent neural stem cells (NSCs) but increases with age in activated (proliferative) NSCs. Quiescent and activated NSCs exhibit opposing adhesion behaviors during aging: quiescent NSCs become less adhesive, whereas activated NSCs become more adhesive. Old activated NSCs also show decreased migration in vitro and diminished mobilization out of the niche for neurogenesis in vivo. Using tension sensors, we find that aging increases force-producing adhesions in activated NSCs. Inhibiting the cytoskeletal-regulating kinase ROCK reduces these adhesions, restores migration in old activated NSCs in vitro, and boosts neurogenesis in vivo. These results have implications for restoring the migratory potential of NSCs and for improving neurogenesis in the aged brain.

Notch signaling as a master regulator of adult neurogenesis

Neurogenesis ceases in most regions of the mammalian brain before or shortly after birth, however, in a few restricted brain regions, the production of new neurons proceeds into adulthood. Neural stem cells (NSCs) in these neurogenic zones are integrated into niches that control their activity and fate. Most stem cells in the adult brain are mitotically inactive and these cells can remain quiescent for months or even years. One of the key questions is what are the molecular mechanisms that regulate NSC maintenance and differentiation. Notch signaling has been shown to be a critical regulator of stem cell activity and maintenance in many tissues including in the nervous system. In this mini-review we discuss the roles of Notch signaling and the functions of the different Notch receptors and ligands in regulating neurogenesis in the adult murine brain. We review the functions of Notch signaling components in controlling NSC quiescence and entry into cell cycle and neurogenesis.

Cell-autonomous and non-cell-autonomous roles of NKCC1 in regulating neural stem cell quiescence in the hippocampal dentate gyrus

Quiescence is a hallmark of adult neural stem cells (NSCs) in the mammalian brain, and establishment and maintenance of quiescence is essential for life-long continuous neurogenesis. How NSCs in the dentate gyrus (DG) of the hippocampus acquire their quiescence during early postnatal stages and continuously maintain quiescence in adulthood is poorly understood. Here, we show that Hopx-CreER^T2-mediated conditional deletion of Nkcc1, which encodes a chloride importer, in mouse DG NSCs impairs both their quiescence acquisition at early postnatal stages and quiescence maintenance in adulthood. Furthermore, PV-CreER^T2-mediated deletion of Nkcc1 in PV interneurons in the adult mouse brain leads to activation of quiescent DG NSCs, resulting in an expanded NSC pool. Consistently, pharmacological inhibition of NKCC1 promotes NSC proliferation in both early postnatal and adult mouse DG. Together, our study reveals both cell-autonomous and non-cell-autonomous roles of NKCC1 in regulating the acquisition and maintenance of NSC quiescence in the mammalian hippocampus.

Mapping human adult hippocampal neurogenesis with single-cell transcriptomics: Reconciling controversy or fueling the debate?

The notion of exploiting the regenerative potential of the human brain in physiological aging or neurological diseases represents a particularly attractive alternative to conventional strategies for enhancing or restoring brain function. However, a major first question to address is whether the human brain does possess the ability to regenerate. The existence of human adult hippocampal neurogenesis (AHN) has been at the center of a fierce scientific debate for many years. The advent of single-cell transcriptomic technologies was initially viewed as a panacea to resolving this controversy. However, recent single-cell RNA sequencing studies in the human hippocampus yielded conflicting results. Here, we critically discuss and re-analyze previously published AHN-related single-cell transcriptomic datasets. We argue that, although promising, the single-cell transcriptomic profiling of AHN in the human brain can be confounded by methodological, conceptual, and biological factors that need to be consistently addressed across studies and openly discussed within the scientific community.

The transcriptional co-activator Yap1 promotes adult hippocampal neural stem cell activation

Most adult hippocampal neural stem cells (NSCs) remain quiescent, with only a minor portion undergoing active proliferation and neurogenesis. The molecular mechanisms that trigger the transition from quiescence to activation are still poorly understood. Here, we found the activity of the transcriptional co-activator Yap1 to be enriched in active NSCs. Genetic deletion of Yap1 led to a significant reduction in the relative proportion of active NSCs, supporting a physiological role of Yap1 in regulating the transition from quiescence to activation. Overexpression of wild-type Yap1 in adult NSCs did not induce NSC activation, suggesting tight upstream control mechanisms, but overexpression of a gain-of-function mutant (Yap1-5SA) elicited cell cycle entry in NSCs and hilar astrocytes. Consistent with a role of Yap1 in NSC activation, single cell RNA sequencing revealed a partial induction of an activated NSC gene expression program. Furthermore, Yap1-5SA expression also induced expression of Taz and other key components of the Yap/Taz regulon that were previously identified in glioblastoma stem cell-like cells. Consequently, dysregulated Yap1 activity led to repression of hippocampal neurogenesis, aberrant cell differentiation, and partial acquisition of a glioblastoma stem cell-like signature.

Isolated loss of the AUTS2 long isoform, brain-wide or targeted to Calbindin -lineage cells, generates a specific suite of brain, behavioral and molecular pathologies

Rearrangements within the AUTS2 region are associated with a rare syndromic disorder with intellectual disability, developmental delay and behavioral abnormalities as core features. In addition, smaller regional variants are linked to wide range of neuropsychiatric disorders, underscoring the gene's essential role in brain development. Like many essential neurodevelopmental genes, AUTS2 is large and complex, generating distinct long (AUTS2-l) and short (AUTS2-s) protein isoforms from alternative promoters. Although evidence suggests unique isoform functions, the contributions of each isoform to specific AUTS2- linked phenotypes have not been clearly resolved. Furthermore, Auts2 is widely expressed across the developing brain, but cell populations most central to disease presentation have not been determined. In this study, we focused on the specific roles of AUTS2-l in brain development, behavior, and postnatal brain gene expression, showing that brain-wide AUTS2-l ablation leads to specific subsets of the recessive pathologies associated with C-terminal mutations that disrupt both isoforms. We identify downstream genes that could explain expressed phenotypes including hundreds of putative direct AUTS2- l target genes. Furthermore, in contrast to C-terminal Auts2 mutations which lead to dominant hypoactivity, AUTS2-l loss-of-function is associated with dominant hyperactivity, a phenotype exhibited by many human patients. Finally, we show that AUTS2-l ablation in Calbindin 1 -expressing cell lineages is sufficient to yield learning/memory deficits and hyperactivity with abnormal dentate gyrus granule cell maturation, but not other phenotypic effects. These data provide new clues to in vivo AUTS2-l functions and novel information relevant to genotype-phenotype correlations in the human AUTS2 region.

Single-cell analysis of the postnatal dorsal V-SVZ reveals a role for Bmpr1a signaling in silencing pallial germinal activity

The ventricular-subventricular zone (V-SVZ) is the largest neurogenic region of the postnatal forebrain, containing neural stem cells (NSCs) that emerge from both the embryonic pallium and subpallium. Despite of this dual origin, glutamatergic neurogenesis declines rapidly after birth, while GABAergic neurogenesis persists throughout life. We performed single-cell RNA sequencing of the postnatal dorsal V-SVZ for unraveling the mechanisms leading to pallial lineage germinal activity silencing. We show that pallial NSCs enter a state of deep quiescence, characterized by high bone morphogenetic protein (BMP) signaling, reduced transcriptional activity and Hopx expression, while in contrast, subpallial NSCs remain primed for activation. Induction of deep quiescence is paralleled by a rapid blockade of glutamatergic neuron production and differentiation. Last, manipulation of Bmpr1a demonstrates its key role in mediating these effects. Together, our results highlight a central role of BMP signaling in synchronizing quiescence induction and blockade of neuronal differentiation to rapidly silence pallial germinal activity after birth.

Cell population dynamics in the course of adult hippocampal neurogenesis: Remaining unknowns

Neural stem cells (NSCs) generate new neurons throughout life in the mammalian hippocampus. The distinct developmental steps in the course of adult neurogenesis, including NSC activation, expansion, and neuronal integration, are increasingly well characterized down to the molecular level. However, substantial gaps remain in our knowledge about regulators and mechanisms involved in this biological process. This review highlights three long-standing unknowns. First, we discuss potency and identity of NSCs and the quest for a unifying model of short- and long-term self-renewal dynamics. Next, we examine cell death, specifically focusing on the early demise of newborn cells. Then, we outline the current knowledge on cell integration dynamics, discussing which (if any) neurons are replaced by newly added neurons in the hippocampal circuits. For each of these unknowns, we summarize the trajectory of studies leading to the current state of knowledge. Finally, we offer suggestions on how to fill the remaining gaps by taking advantage of novel technology to reveal currently hidden secrets in the course of adult hippocampal neurogenesis.

Early fate bias in neuroepithelial progenitors of hippocampal neurogenesis

Hippocampal adult neural stem cells emerge from progeny of the neuroepithelial lineage during murine brain development. Hippocampus development is increasingly well understood. However, the clonal relationships between early neuroepithelial stem cells and postnatal neurogenic cells remain unclear, especially at the single-cell level. Here we report fate bias and gene expression programs in thousands of clonally related cells in the juvenile hippocampus based on single-cell RNA-seq of barcoded clones. We find evidence for early fate restriction of neuroepithelial stem cells to either neurogenic progenitor cells of the dentate gyrus region or oligodendrogenic, non-neurogenic fate supplying cells for other hippocampal regions including gray matter areas and the Cornu ammonis region 1/3. Our study provides new insights into the phenomenon of early fate restriction guiding the development of postnatal hippocampal neurogenesis.

Lateral septal nucleus, dorsal part, and dentate gyrus are necessary for spatial and object recognition memory, respectively, in mice

Introduction

Cognitive impairment includes the abnormality of learning, memory and judgment, resulting in severe learning and memory impairment and social activity impairment, which greatly affects the life quality of individuals. However, the specific mechanisms underlying cognitive impairment in different behavioral paradigms remain to be elucidated.

Methods

The study utilized two behavioral paradigms, novel location recognition (NLR) and novel object recognition (NOR), to investigate the brain regions involved in cognitive function. These tests comprised two phases: mice were presented with two identical objects for familiarization during the training phase, and a novel (experiment) or familiar (control) object/location was presented during testing. Immunostaining quantification of c-Fos, an immediate early gene used as a neuronal activity marker, was performed in eight different brain regions after the NLR or NOR test.

Results

The number of c-Fos-positive cells was significantly higher in the dorsal part of the lateral septal nucleus (LSD) in the NLR and dentate gyrus (DG) in the NOR experiment group than in the control group. We further bilaterally lesioned these regions using excitotoxic ibotenic acid and replenished the damaged areas using an antisense oligonucleotide (ASO) strategy.

Discussion

These data reinforced the importance of LSD and DG in regulating spatial and object recognition memory, respectively. Thus, the study provides insight into the roles of these brain regions and suggests potential intervention targets for impaired spatial and object recognition memory.

Promoting Endogenous Neurogenesis as a Treatment for Alzheimer's Disease

Alzheimer's disease (AD) is the most universal neurodegenerative disorder characterized by memory loss and cognitive impairment. AD is biologically defined by production and aggregation of misfolded protein including extracellular amyloid β (Aβ) peptide and intracellular microtubule-associated protein tau tangles in neurons, leading to irreversible neuronal loss. At present, regulation of endogenous neurogenesis to supplement lost neurons has been proposed as a promising strategy for treatment of AD. However, the exact underlying mechanisms of impaired neurogenesis in AD have not been fully explained and effective treatments targeting neurogenesis for AD are limited. In this review, we mainly focus on the latest research of impaired neurogenesis in AD. Then we discuss the factors affecting stages of neurogenesis and the interplay between neural stem cells (NSCs) and neurogenic niche under AD pathological conditions. This review aims to explore potential therapeutic strategies that promote endogenous neurogenesis for AD treatments.