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Graphical abstract, Highlights • NESTIN, SOX1, and SOX4 decreased progressively from prenatal to adult age. • KI67 and TBR2 reached zero expression level at adolescence. • NEUROD1, DCX, PSA NCAM remained unchanged post-childhood. • VEGF and FGF2 did not change significantly from prenatal to adult age. • BAX and TP53 decreased progressively from prenatal to adult age., Purpose Immunohistological investigations have given rise to divergent perspectives about adult hippocampal neurogenesis in humans. Therefore, this study aimed to examine whether a comprehensive transcriptomic analysis of signature markers of neurogenesis, supplemented with markers of gliogenesis, vasculogenesis, cell proliferation, and apoptosis, may help discern essential aspects of adult hippocampal neurogenesis in humans. Materials and Methods RNA expression data for salient marker genes of neurogenesis, gliogenesis, vasculogenesis, and apoptosis in post-mortem human hippocampal tissue [from prenatal (n = 15), child (n = 5), adolescent (n = 4), and adult (n = 6) brains] were downloaded from the Allen Human Brain Atlas database (http://www.brainspan.org/rnaseq/search/index.html). Gene expression data was categorized, median values were computed, and age group-specific differential expression was subjected to statistical analysis (significance level, α = 0.01). Results With the exception of the genes encoding GFAP, BLBP, SOX2, and PSA-NCAM (unchanged), and the post-mitotic late maturation markers CALB1, CALB2, MAP2, and NEUN as well as the pan-neuronal marker PROX1 which were persistently expressed throughout, expression of all other genes associated with neurogenesis was steeply and progressively downregulated between perinatal life and adulthood. Interestingly, expression of the classical proliferation marker KI67 and a progenitor cell marker TBR2 were found to have reached baseline expression levels (zero expression score) at adolescence while the expression of immature neuronal, post-mitotic early and late maturation markers remained at a constant level after childhood. In contrast, markers of gliogenesis (other than PDGFRA and Vimentin) were significantly upregulated between prenatal life and childhood. Expression of the vasculogenesis markers VEGFA and FGF2 did not differ across any of the age groups studied, whereas the expression of apoptotic markers was progressively decreased after prenatal life. Conclusions Our findings indicate that the progression of neurogenesis from progenitor cells is highly restricted in the human brain from childhood onwards. An alternative possibility that limited neurogenesis may be continued in adolescents and adults from a developmentally arrested pool of immature neurons needs to be examined further through experimental studies.

Summary During brain development, neural stem cells (NSCs) initially produce neurons and change their fate to generate glias. While the regulation of neurogenesis is well characterized, specific markers for glial precursor cells (GPCs) and the master regulators for gliogenesis remain unidentified. Accumulating evidence suggests that RNA-binding proteins (RBPs) have significant roles in neuronal development and function, as they comprehensively regulate the expression of target genes in a cell-type-specific manner. We systematically investigated the expression profiles of 1,436 murine RBPs in the developing mouse brain and identified quaking (Qk) as a marker of the putative GPC population. Functional analysis of the NSC-specific Qk-null mutant mouse revealed the key role of Qk in astrocyte and oligodendrocyte generation and differentiation from NSCs. Mechanistically, Qk upregulates gliogenic genes via quaking response elements in their 3′ untranslated regions. These results provide crucial directions for identifying GPCs and deciphering the regulatory mechanisms of gliogenesis from NSCs., Graphical Abstract, Highlights • Differential expression analysis identified Qk as a glial precursor cell marker • Loss of Qk ablated both astrocyte and OL production from neural stem cells • Qk−/− NSCs failed to become glia and aberrantly expressed neural genes • Qk comprehensively upregulates essential genes for gliogenesis as regulons via QREs, This study sought to determine whether there is a common glial precursor cell (GPC), what the GPC markers are, and what molecular mechanisms govern gliogenesis. Takeuchi and colleagues identified the RNA-binding protein Qk as a GPC marker. Functional analysis revealed that Qk comprehensively upregulates essential genes for gliogenesis and that loss of Qk disrupts the generation of glial cells from NSCs.

Astrocytes perform multiple essential functions in the developing and mature brain, including regulation of synapse formation, control of neurotransmitter release and uptake, and maintenance of extracellular ion balance. As a result, astrocytes have been implicated in the progression of neurodegenerative disorders such as Alzheimer's disease, Huntington's disease, and Parkinson's disease. Despite these critical functions, the study of human astrocytes can be difficult because standard differentiation protocols are time-consuming and technically challenging, but a differentiation protocol recently developed in our laboratory enables the efficient derivation of astrocytes from human embryonic stem cells. We used this protocol along with microarrays, luciferase assays, electrophoretic mobility shift assays, and ChIP assays to explore the genes involved in astrocyte differentiation. We demonstrate that paired-like homeodomain transcription factor 1 (PITX1) is critical for astrocyte differentiation. PITX1 overexpression induced early differentiation of astrocytes, and its knockdown blocked astrocyte differentiation. PITX1 overexpression also increased and PITX1 knockdown decreased expression of sex-determining region Y box 9 (SOX9), known initiator of gliogenesis, during early astrocyte differentiation. Moreover, we determined that PITX1 activates the SOX9 promoter through a unique binding motif. Taken together, these findings indicate that PITX1 drives astrocyte differentiation by sustaining activation of the SOX9 promoter.

Significance Depletion of the neural stem cell (NSC) pool is a major driver of age-related regenerative decline in the hippocampus. While increased quiescence is a major contributor to this decline, NSCs can also undergo terminal differentiation into astrocytes, thus restricting the stem cell pool. The mechanisms underlying this fate switch and their relation to age-related regenerative decline have not yet been fully elucidated. In this study, we report an age-related decline in NSC O-GlcNAcylation, coincident with reduced neurogenesis and increased gliogenesis. We identify loss of O-GlcNAcylation at STAT3 T717 in the hippocampus with age, and demonstrate that O-GlcNAcylation of this site is a critical determinant of NSC fate. Our work expands our understanding of how posttranslational modifications influence the aging brain., Increased neural stem cell (NSC) quiescence is a major determinant of age-related regenerative decline in the adult hippocampus. However, a coextensive model has been proposed in which division-coupled conversion of NSCs into differentiated astrocytes restrict the stem cell pool with age. Here we report that age-related loss of the posttranslational modification, O-linked β-N-acetylglucosamine (O-GlcNAc), in NSCs promotes a glial fate switch. We detect an age-dependent decrease in NSC O-GlcNAc levels coincident with decreased neurogenesis and increased gliogenesis in the mature hippocampus. Mimicking an age-related loss of NSC O-GlcNAcylation in young mice reduces neurogenesis, increases astrocyte differentiation, and impairs associated cognitive function. Using RNA-sequencing of primary NSCs following decreased O-GlcNAcylation, we detected changes in the STAT3 signaling pathway indicative of glial differentiation. Moreover, using O-GlcNAc–specific mass spectrometry analysis of the aging hippocampus, together with an in vitro site-directed mutagenesis approach, we identify loss of STAT3 O-GlcNAc at Threonine 717 as a driver of astrocyte differentiation. Our data identify the posttranslational modification, O-GlcNAc, as a key molecular regulator of regenerative decline underlying an age-related NSC fate switch.

Glial cells are crucial for the development of the central nervous system and the maintenance of chemical homeostasis. The process of gliogenesis has been well studied in the rodent brain, but it remains less well studied in the human brain. In addition, rodent glial cells differ from human counterparts in terms of morphologies, functions, and anatomical locations. Cerebral organoids (also referred to as spheroids) derived from human pluripotent stem cells (hPSCs) have been developed and are suitable cell‐based models for researching developmental and neurodegenerative diseases. The in vitro generation of glia, including astrocytes and oligodendrocytes, from such organoids represents a promising tool to model neuronal diseases. Here, we showed that three‐dimensional (3D) culture of OLIG2‐ and NKX2.2‐expressing neurospheres produced efficiently mature astrocytes and oligodendrocytes in terms of morphologies and expression pattern recapitulating native 3D environment. Our findings provide important insights for developmental research of the human brain and glial specification that may facilitate patient‐specific disease modeling., Human pluripotent stem cell‐derived cerebral organoids can mimic development of the mammalian central nervous system. In this study, we demonstrate that pre‐patterned stem/progenitor cells, especially OLIG2/NKX2.2‐expressing pre‐oligodendrocyte progenitor cells, facilitate glial specification during organoid development. The resulting spheroids can serve as in vitro model for myelination to evaluate promyelination drugs and a source for cell therapy in demyelinating disease.

The RAS/RAF/MEK/ERK pathway promotes gliogenesis but the kinetic role of RAF1, a key RAF kinase, in the induction of astrocytogenesis remains to be elucidated. To address this challenge, we determine the temporal functional outcome of RAF1 during mouse neural progenitor cell differentiation using an optogenetic RAF1 system (OptoRAF1). OptoRAF1 allows for reversible activation of the RAF/MEK/ERK pathway via plasma membrane recruitment of RAF1 based on blue light-sensitive protein dimerizer CRY2/CIB1. We found that early light-induced OptoRAF1 activation in neural progenitor cells promotes cell proliferation and increased expression of glial markers and glia-enriched genes. However, delayed OptoRAF1 activation in differentiated neural progenitor had little effect on glia marker expression, suggesting that RAF1 is required to promote astrocytogenesis only within a short time window. In addition, activation of OptoRAF1 did not have a significant effect on neurogenesis, but was able to promote neuronal neurite growth.

The regulation of gliogenesis is a fundamental process for nervous system development, as the appropriate glial number and identity is required for a functional nervous system. To investigate the molecular mechanisms involved in gliogenesis, we used C. elegans as a model and identified the function of the proneural gene lin-32/Atoh1 in gliogenesis. We found that lin-32 functions during embryonic development to negatively regulate the number of AMsh glia. The ectopic AMsh cells at least partially arise from cells originally fated to become CEPsh glia, suggesting that lin-32 is involved in the specification of specific glial subtypes. Moreover, we show that lin-32 acts in parallel with cnd-1/ NeuroD1 and ngn-1/ Neurog1 in negatively regulating an AMsh glia fate. Furthermore, expression of murine Atoh1 fully rescues lin-32 mutant phenotypes, suggesting lin-32/Atoh1 may have a conserved role in glial specification.

Determining the origin of different glial subtypes is crucial to understand glial heterogeneity, and to enhance our knowledge of glial and progenitor cell behavior in embryos and adults. NG2-glia are homogenously distributed in a grid-like manner in both, gray and white matter of the adult brain. While some NG2-glia in the CNS are responsible for the generation of mature oligodendrocytes (OPCs), most of them do not differentiate and they can proliferate outside of adult neurogenic niches. Thus, NG2-glia constitute a heterogeneous population containing different subpopulations with distinct functions. We hypothesized that their diversity emerges from specific progenitors during development, as occurs with other glial cell subtypes. To specifically target NG2-pallial progenitors and to define the NG2-glia lineage, as well as the NG2-progenitor potential, we designed two new StarTrack strategies using the NG2 promoter. These approaches label NG2 expressing progenitor cells, permitting the cell fates of these NG2 progenitors to be tracked in vivo. StarTrack labelled cells producing different neural phenotypes in different regions depending on the age targeted, and the strategy selected. This specific genetic targeting of neural progenitors in vivo has provided new data on the heterogeneous pool of NG2 progenitors at both embryonic and postnatal ages., This work was supported by research Grants from the Ministerio de Economía y Competitividad (MINECO; BFU2016-75207-R) and Fundación Ramón Areces (Ref. CIVP9A5928).

Background Noonan syndrome (NS) is a developmental disorder caused by mutations of Src homology 2 domain-containing protein tyrosine phosphatase 2 (SHP2). Although NS patients have diverse neurological manifestations, the mechanisms underlying the involvement of SHP2 mutations in neurological dysfunction remain elusive. Methods Induced pluripotent stem cells generated from dermal fibroblasts of three NS-patients (NS-iPSCs) differentiated to the neural cells by using two different culture systems, 2D- and 3D-cultured systems in vitro. Results Here we represent that SHP2 mutations cause aberrant neural development. The NS-iPSCs exhibited impaired development of EBs in which BMP and TGF-β signalings were activated. Defective early neuroectodermal development of NS-iPSCs recovered by inhibition of both signalings and further differentiated into NPCs. Intriguingly, neural cells developed from NS-NPCs exhibited abundancy of the glial cells, neurites of neuronal cells, and low electrophysiological property. Those aberrant phenotypes were also detected in NS-cerebral organoids. SHP2 inhibition in the NS-NPCs and NS-cerebral organoids ameliorated those anomalies such as biased glial differentiation and low neural activity. Conclusion Our findings demonstrate that SHP2 mutations contribute to precocious gliogenesis in NS-iPSCs during neural development in vitro.

Stroke is the leading cause of adult disability. Recovery of function after stroke involves signaling events that are mediated by cAMP and cGMP pathways, such as axonal sprouting, neurogenesis, and synaptic plasticity. cAMP and cGMP are degraded by phosphodiesterases (PDEs), which are differentially expressed in brain regions. PDE10A is highly expressed in the basal ganglia/striatum. We tested a novel PDE10A inhibitor (TAK-063) for its effects on functional recovery. Stroke was produced in mice in the cortex or the striatum. Behavioral recovery was measured to 9 weeks. Tissue outcome measures included analysis of growth factor levels, angiogenesis, neurogenesis, gliogenesis, and inflammation. TAK-063 improved motor recovery after striatal stroke in a dose-related manner, but not in cortical stroke. Recovery of motor function correlated with increases in striatal brain-derived neurotrophic factor. TAK-063 treatment also increased motor system axonal connections. Stroke affects distinct brain regions, with each comprising different cellular and molecular elements. Inhibition of PDE10A improved recovery of function after striatal but not cortical stroke, consistent with its brain localization. This experiment is the first demonstration of brain region-specific enhanced functional recovery after stroke, and indicates that differential molecular signaling between brain regions can be exploited to improve recovery based on stroke subtype. Electronic supplementary material The online version of this article (10.1007/s12975-020-00819-8) contains supplementary material, which is available to authorized users.

Although astrocytes have gained increased recognition as an important regulator in normal brain function and pathology, the mechanisms underlying their genesis are not well understood. In this study, we show that constitutive YAP activation by in utero introduction of a non-degradable form of the YAP gene (YAP 5SA) causes productive GFAP+ cell generation at late embryonic periods, and this activity is nuclear localization- and TEAD transcription factor-dependent. Moreover, we found that the GFAP+ cells were not YAP 5SA-expressing cells themselves but cells in the vicinity in vivo. Conditioned medium prepared from YAP 5SA-expressing cells induced GFAP+ cell production in vitro, suggesting that a soluble factor(s) was mediating the astrogenic activity of YAP 5SA. Indeed, YAP 5SA expression greatly increased CNTF and BMP4 transcription in neural progenitor cells, and a neutralizing antibody against CNTF reduced the astrogenic effects of YAP 5SA-conditioned medium. Furthermore, the YAP 5SA-expressing cells were identified as FN1+ mesenchymal cells which are responsible for the precocious astrogenesis. These results suggest a novel molecular mechanism by which YAP activation can induce astrogenesis in a non-cell autonomous manner.

Exposure to air pollution - and particularly to particulate matter (PM) - is strongly associated with higher risk of neurodevelopmental disorders, poor mental health and cognitive defects. In animal models, disruption of CNS development and disturbances of adult neurogenesis contribute to PM neurotoxicity. Recent studies show that gestational PM exposure not only affects embryonic neurodevelopment, but also disturbs postnatal brain growth and maturation, by interfering with neurogenic/gliogenic events, myelination and synaptogenesis. Similarly, adult neurogenesis is affected at many levels, from neural stem cell amplification up to the maturation and integration of novel neurons in the adult brain parenchyma. The underlying mechanisms are still by and large unknown. Beyond microglia activation and neuroinflammation, recent studies propose a role for novel epigenetic mechanisms, including DNA methylation and extracellular vesicles-associated microRNAs.

Hypoxic damage to the developing brain due to preterm birth causes many anatomical changes, including damage to the periventricular white matter. This results in the loss of glial cells, significant disruptions in myelination, and thereby cognitive and behavioral disabilities seen throughout life. Encouragingly, these neurological morbidities can be improved by environmental factors; however, the underlying cellular mechanisms remain unknown. We found that early and continuous environmental enrichment selectively enhances endogenous repair of the developing white matter by promoting oligodendroglial maturation, myelination, and functional recovery after perinatal brain injury. These effects require increased exposure to socialization, physical activity, and cognitive enhancement of surroundings—a complete enriched environment. Using RNA-sequencing, we identified oligodendroglial-specific responses to hypoxic brain injury, and uncovered molecular mechanisms involved in enrichment-induced recovery. Together, these results indicate that myelin plasticity induced by modulation of the neonatal environment can be targeted as a therapeutic strategy for preterm birth., Hypoxic brain damage associated with premature birth causes lasting neurological impairments. Here, the authors use environmental enrichment to rescue white matter dysmaturation following hypoxia, while identifying a critical window of intervention and oligodendrocyte-specific changes in gene expression.

During development, regulatory factors appear in a precise order to determine cell fates over time. Consequently, to investigate complex tissue development, it is necessary to visualize and manipulate cell lineages with temporal control. Current strategies for tracing vertebrate cell lineages lack genetic access to sequentially produced cells. Here, we present TEMPO (Temporal Encoding and Manipulation in a Predefined Order), an imaging-readable genetic tool allowing differential labeling and manipulation of consecutive cell generations in vertebrates. TEMPO is based on CRISPR and powered by a cascade of gRNAs that drive orderly activation and inactivation of reporters and/or effectors. Using TEMPO to visualize zebrafish and mouse neurogenesis, we recapitulated birth-order-dependent neuronal fates. Temporally manipulating cell-cycle regulators in mouse cortex progenitors altered the proportion and distribution of neurons and glia, revealing the effects of temporal gene perturbation on serial cell fates. Thus, TEMPO enables sequential manipulation of molecular factors, crucial to study cell-type specification.

Enteric glia are a fascinating population of cells. Initially identified in the gut wall as the "support" cells of the enteric nervous system, studies over the past 20 years have unveiled a vast array of functions carried out by enteric glia. They mediate enteric nervous system signalling and play a vital role in the local regulation of gut functions. Enteric glial cells interact with other gastrointestinal cell types such as those of the epithelium and immune system to preserve homeostasis, and are perceptive to luminal content. Their functional versatility and phenotypic heterogeneity are mirrored by an extensive level of plasticity, illustrated by their reactivity in conditions associated with enteric nervous system dysfunction and disease. As one of the hallmarks of their plasticity and extending their operative relationship with enteric neurons, enteric glia also display neurogenic potential. In this review, we focus on the development of enteric glial cells, and the mechanisms behind their heterogeneity in the adult gut. In addition, we discuss what is currently known about the role of enteric glia as neural precursors in the enteric nervous system. WB is supported by the Francqui Foundation and grants from the Research Foundation Flanders (FWO: G036320N) and the Dutch Research Council (NWO VIDI: 016.196.367). AN and MMH are funded by Cancer Australia (APP1181621), Cure Cancer, the CanToo Foundation, and the Jennifer Eggins Cancer Support Trust Fund. MMH is an ARC DECRA fellow (DE190101209).

Dentate gyrus (DG) of the mammalian hippocampus gives rise to new neurons and astrocytes all through adulthood. Canine hippocampus presents many similarities in fetal development, anatomy, and physiology with human hippocampus, establishing canines as excellent animal models for the study of adult neurogenesis. In the present study, BrdU-dated cells of the structurally and functionally dissociated dorsal (dDG) and ventral (vDG) adult canine DG were comparatively examined over a period of 30 days. Each part's neurogenic potential, radial glia-like neural stem cells (NSCs) proliferation and differentiation, migration, and maturation of their progenies were evaluated at 2, 5, 14, and 30 days post BrdU administration, with the use of selected markers (glial fibrillary acidic protein, doublecortin, calretinin and calbindin). Co-staining of BrdU+ cells with NeuN or S100B permitted the parallel study of the ongoing neurogenesis and gliogenesis. Our findings reveal the comparatively higher populations of residing granule cells, proliferating NSCs and BrdU+ neurons in the dDG, whereas newborn neurons of the vDG showed a prolonged differentiation, migration, and maturation. Newborn astrocytes were found all along the dorso-ventral axis, counting however for only 11% of newborn cell population. Comparative evaluation of adult canine and rat neurogenesis revealed significant differences in the distribution of resident and newborn granule cells along the dorso-ventral axis, division pattern of adult NSCs, maturation time plan of newborn neurons, and ongoing gliogenesis. Concluding, spatial and temporal features of adult canine neurogenesis are similar to that of other gyrencephalic species, including humans, and justify the comparative examination of adult neurogenesis across mammalian species.

The processes of neural genesis, namely neurogenesis, astrogliogenesis, and oligodendrogenesis, that is, the formation of new neurons, astrocytes, and oligodendrocytes start with embryonic developm...

Recent studies have begun to reveal surprising levels of cell diversity in the human brain, both in adults and during development. Distinctive cellular phenotypes point to complex molecular profiles, cellular hierarchies and signaling pathways in neural stem cells, progenitor cells, neuronal and glial cells. Several recent reports have suggested that neural stem and progenitor cell types found in the developing and adult brain share several properties and phenotypes with cells from brain primary tumors, such as gliomas. This transcriptomic crosstalk may help us to better understand the cell hierarchies and signaling pathways in both gliomas and the normal brain, and, by clarifying the phenotypes of cells at the origin of the tumor, to therapeutically address their most relevant signaling pathways.

Sulf2a belongs to the Sulf family of extracellular sulfatases which selectively remove 6-O-sulfate groups from heparan sulfates, a critical regulation level for their role in modulating the activity of signalling molecules. Data presented here define Sulf2a as a novel player in the control of Sonic Hedgehog (Shh)-mediated cell type specification during spinal cord development. We show that Sulf2a depletion in zebrafish results in overproduction of V3 interneurons at the expense of motor neurons and also impedes generation of oligodendrocyte precursor cells (OPCs), three cell types that depend on Shh for their generation. We provide evidence that Sulf2a, expressed in a spatially restricted progenitor domain, acts by maintaining the correct patterning and specification of ventral progenitors. More specifically, Sulf2a prevents Olig2 progenitors to activate high-threshold Shh response and, thereby, to adopt a V3 interneuron fate, thus ensuring proper production of motor neurons and OPCs. We propose a model in which Sulf2a reduces Shh signalling levels in responding cells by decreasing their sensitivity to the morphogen factor. More generally, our work, revealing that, in contrast to its paralog Sulf1, Sulf2a regulates neural fate specification in Shh target cells, provides direct evidence of non-redundant functions of Sulfs in the developing spinal cord.

Knowledge on cortical development is based mainly on rodent besides primates and carnivores, all being altricial. Here, we analyzed a precocial animal, the pig, looking at dorsoparietal cortex from E45 to P90. At E45, most ionized calcium-binding adapter molecule 1-positive (Iba1+) cells had a macrophage-like morphology and resided in meninges and choroid plexus. Only a few cells were scattered in ventricular and subventricular zone (VZ and SVZ). At E60/E70, all laminar compartments displayed microglia cells at a low-to-moderate density, being highest in VZ and SVZ followed by intermediate zone/white matter (IZ/WM). Cortical plate and marginal zone displayed only a few Iba1+ cells. Cells were intensely labeled, but still had poorly arborized somata and many resembled ameboid, macrophage-like microglia. Concurrent with a massive increase in cortical volume, microglia cell density increased until E85, and further until E100/E110 (birth at E114) to densities that resemble those seen postnatally. A fraction of microglia co-labeled with Ki67 suggesting proliferation in all laminar compartments. Cell-to-cell distance decreased substantially during this time, and the fraction of microglia to all nuclei and to neurons increases in the laminar compartments. Eventually, of all cortical DAPI+ nuclei 7-12% were Iba1+ microglia. From E70 onwards, more and more cells with ramified processes were present in MZ down to IZ/WM, showing for instance a close association with NeuN+, NPY+ and GAD65/67+ somata and axon initial segments. These results suggested that development of microglia cell density and morphology proceeds rapidly from mid-gestation onwards reaching near-adult status already before birth. This article is protected by copyright. All rights reserved.

The human brain is subdivided into distinct anatomical structures, including the neocortex, which in turn encompasses dozens of distinct specialized cortical areas. Early morphogenetic gradients are known to establish early brain regions and cortical areas, but how early patterns result in finer and more discrete spatial differences remains poorly understood1. Here we use single-cell RNA sequencing to profile ten major brain structures and six neocortical areas during peak neurogenesis and early gliogenesis. Within the neocortex, we find that early in the second trimester, a large number of genes are differentially expressed across distinct cortical areas in all cell types, including radial glia, the neural progenitors of the cortex. However, the abundance of areal transcriptomic signatures increases as radial glia differentiate into intermediate progenitor cells and ultimately give rise to excitatory neurons. Using an automated, multiplexed single-molecule fluorescent in situ hybridization approach, we find that laminar gene-expression patterns are highly dynamic across cortical regions. Together, our data suggest that early cortical areal patterning is defined by strong, mutually exclusive frontal and occipital gene-expression signatures, with resulting gradients giving rise to the specification of areas between these two poles throughout successive developmental timepoints., RNA-sequencing analysis of the prenatal human brain at different stages of development shows that areal transcriptional signatures are dynamic and coexist with developmental and cell-type signatures.

Brain organoids are self-organized three-dimensional aggregates generated from pluripotent stem cells. They exhibit complex cell diversities and organized architectures that resemble human brain development ranging from neural tube formation, neuroepithelium differentiation, neurogenesis and gliogenesis, to neural circuit formation. Rapid advancements in brain organoid culture technologies have allowed researchers to generate more accurate models of human brain development and neurological diseases. These models also allow for direct investigation of pathological processes associated with infectious diseases affecting the nervous system. In this review, we first briefly summarize recent advancements in brain organoid methodologies and neurodevelopmental processes that can be effectively modeled by brain organoids. We then focus on applications of brain organoids to investigate the pathogenesis of neurotropic viral infection. Finally, we discuss limitations of the current brain organoid methodologies as well as applications of other organ specific organoids in the infectious disease research.

Hippocampal sclerosis (HS) is one of the most common pathological type of intractable temporal lobe epilepsy (TLE), often characterized by hippocampal atrophy, neuronal apoptosis, and gliogenesis. However, the molecular mechanisms of neuronal apoptosis in patients with HS are still not fully understood. We therefore conducted a pilot study focusing on the neuronal apoptosis ceRNA network in the sclerotic hippocampus of intractable TLE patients. In this research, RNA sequencing (RNA-seq) was utilized to quantify the expression levels of lncRNAs, miRNAs, and mRNAs in TLE patients with HS (HS-TLE) and without HS (non-HS-TLE), and reverse transcription-quantitative PCR (qRT-PCR). The interactions of differential expression (DE) lncRNAs-miRNAs or DEmiRNAs-mRNAs were integrated by StarBase v3.0, and visualized using Cytoscape. Subsequently, we annotate the functions of lncRNA-associated competitive endogenous RNA (ceRNA) network through analysis of their interactions with mRNAs. RNA-seq analyses showed 381 lncRNAs, 42 miRNAs, and 457 mRNAs were dysregulated expression in HS-TLE compared to non-HS-TLE. According to the ceRNA hypothesis, 5 HS-specific ceRNA network were constructed. Among them, the core ceRNA regulatory network involved in neuronal apoptosis was constituted by 10 DElncRNAs (CDKN2B-AS1, MEG3, UBA6-AS1, etc.), 7 DEmiRNAs (hsa-miR-155-5p, hsa-miR-195-5p, hsa-miR-200c-3p, etc.), and 3 DEmRNAs (SCN2A, DYRK2, and MAPK8), which belonging to apoptotic and epileptic terms. Our findings established the first ceRNA network of lncRNA-mediated neuronal apoptosis in HS-TLE based on transcriptome sequencing, which provide a new perspective on the disease pathogenesis and precise treatments of HS.

Autism spectrum disorders (ASD) are associated with mutations of chromodomain-helicase DNA-binding protein 8 (Chd8) and tuberous sclerosis complex 2 (Tsc2). Although these ASD-related genes are detected in glial cells such as microglia, the effect of Chd8 or Tsc2 deficiency on microglial functions and microglia-mediated brain development remains unclear. In this study, we investigated the role of microglial Chd8 and Tsc2 in cytokine expression, phagocytosis activity, and neuro/gliogenesis from neural stem cells (NSCs) in vitro. Chd8 or Tsc2 knockdown in microglia reduced insulin-like growth factor-1(Igf1) expression under lipopolysaccharide (LPS) stimulation. In addition, phagocytosis activity was inhibited by Tsc2 deficiency, microglia-mediated oligodendrocyte development was inhibited, in particular, the differentiation of oligodendrocyte precursor cells to oligodendrocytes was prevented by Chd8 or Tsc2 deficiency. These results suggest that ASD-related gene expression in microglia is involved in oligodendrocyte differentiation, which may contribute to the white matter pathology relating to ASD.

Amyloid-β 42 peptide (Aβ1-42 (Aβ42)) is well-known for its involvement in the development of Alzheimer’s disease (AD). Aβ42 accumulates and aggregates in fibers that precipitate in the form of plaques in the brain causing toxicity, however, like other forms of Aβ peptide, the role of these peptides remains unclear. Here we analyze and compare the effects of oligomeric and fibrillary Aβ42 peptide on the biology (cell death, proliferative rate, and cell fate specification) of differentiating human neural stem cells (hNS1 cell line). By using the hNS1 cells we found that, at high concentrations, oligomeric and fibrillary Aβ42 peptides provoke apoptotic cellular death and damage of DNA in these cells, but Aβ42 fibrils have the strongest effect. The data also show that both oligomeric and fibrillar Aβ42 peptides decrease cellular proliferation but Aβ42 oligomers have the greatest effect. Finally, both, oligomers and fibrils favor gliogenesis and neurogenesis in hNS1 cells, although, in this case, the effect is more prominent in oligomers. All together the findings of this study may contribute to a better understanding of the molecular mechanisms involved in the pathology of AD and to the development of human neural stem cell-based therapies for AD treatment.

[This corrects the article DOI: 10.3389/fnins.2022.919462.]., (Copyright © 2023 Galante, Marichal, Scarante, Ghayad, Shi, Schuurmans, Berninger and Péron.)