Isolation of multipotent neural stem or progenitor cells from both the dentate gyrus and subventricular zone of a single adult mouse

O-GlcNAcylation of circadian clock protein Bmal1 impairs cognitive function in diabetic mice

Neuronal damage in the hippocampus induced by high glucose has been shown to promote the onset and development of cognitive impairment in diabetes, but the underlying molecular mechanism remains unclear. Guided by single-cell RNA sequencing, we here report that high glucose increases O-GlcNAcylation of Bmal1 in hippocampal neurons. This glycosylation promotes the binding of Clock to Bmal1, resulting in the expression of transcription factor Bhlhe41 and its target Dnajb4. Upregulated Dnajb4 in turn leads to ubiquitination and degradation of the mitochondrial Na + /Ca2+ exchanger NCLX, thereby inducing mitochondrial calcium overload that causes neuronal damage and cognitive impairment in mice. Notably, Bhlhe41 downregulation or treatment with a short peptide that specifically blocks O-GlcNAcylation of Bmal1 on Ser424 mitigated these adverse effects in diabetic mouse models. These data highlight the crucial role of O-GlcNAcylation in circadian clock gene expression and may facilitate the design of targeted therapies for diabetes-associated cognitive impairment.

Saroglitazar Enhances Memory Functions and Adult Neurogenesis via Up-Regulation of Wnt/β Catenin Signaling in the Rat Model of Dementia

Peroxisome proliferator-activated receptors (PPARs) have emerged as a promising target for the treatment of various neurodegenerative disorders. Studies have shown that both PPAR α & γ individually modulate various pathophysiological events like neuroinflammation and insulin resistance, which are known to variedly affect neurogenesis. Our study aimed to evaluate the effect of saroglitazar (SGZR), a dual PPAR agonist, on adult neurogenesis and spatial learning and memory, in intracerebroventricular streptozotocin (ICV STZ)-induced dementia in rats. We have found that SGZR at the dose of 4 mg/kg per oral showed significant improvement in learning and memory compared to ICV STZ-treated rats. A substantial increase in neurogenesis was observed in the subventricular zone (SVZ) and the dentate gyrus (DG), as indicated by an increase in the number of 5-bromo-2'-deoxyuridine (BrdU)+ cells, BrdU+ nestin+ cells, and doublecortin (DCX)+cells. Treatment with SGZR also decreased the active form of glycogen synthase kinase 3β (GSK3β) and hence enhanced the nuclear translocation of the β-catenin. Enhanced expression of Wnt transcription factors and target genes indicates that the up-regulation of Wnt signaling might be involved in the observed increase in neurogenesis. Hence, it can be concluded that the SGZR enhances memory functions and adult neurogenesis via the upregulation of Wnt β-catenin signaling in ICV STZ-treated rats.

Immunological isolation and characterization of neuronal progenitors from human dental pulp: A laboratory-based investigation

AIMS

Dental pulp stem cells (DPSCs) contain a population of stem cells with a broad range of differentiation potentials, as well as more lineage-committed progenitors. Such heterogeneity is a significant obstacle to experimental and clinical applications. The aim of this study is to isolate and characterize a homogenous neuronal progenitor cell population from human DPSCs.

METHODOLOGY

Polysialylated-neural cell adhesion molecule (PSA-NCAM+) neural progenitors were isolated from the dental pulp of three independent donors using magnetic-activated cell sorting (MACS) technology. Immunofluorescent staining with a panel of neural and non-neural markers was used to characterize the magnetically isolated PSA-NCAM+ fraction. PSA-NCAM+ cells were then cultured in Neurobasal A supplemented with neurotrophic factors: dibutyryl cyclic-AMP, neurotrophin-3, B27 and N2 supplements to induce neuronal differentiation. Both PSA-NCAM+ and differentiated PSA-NCAM+ cells were used in Ca2+ imaging studies to assess the functionality of P2X3 receptors as well as membrane depolarization.

RESULTS

PSA-NCAM+ neural progenitors were isolated from a heterogeneous population of hDPSCs using magnetic-activated cell sorting and anti-PSA-NCAM MicroBeads. Flow cytometry analysis demonstrated that immunomagnetic sorting significantly increased the purity of PSA-NCAM+ cells. Immunofluorescent staining revealed expression of pan-neuronal and mature neuronal markers, PGP9.5 and MAP2, respectively, as well as weak expression of the mature sensory markers, peripherin and islet1. ATP-induced response was mediated predominately by P2X3 receptors in both undifferentiated and differentiated cells, with a greater magnitude observed in the latter. In addition, membrane depolarizations were also detected in cells before and after differentiation when loaded with fast-voltage-responding fluorescent molecule, FluoVolt™ in response to potassium chloride. Interestingly, only differentiated PSA-NCAM+ cells were capable of spontaneous membrane oscillations.

CONCLUSIONS

In summary, DPSCs contain a population of neuronal progenitors with enhanced neural differentiation and functional neural-like properties that can be effectively isolated with magnetic-activated cell sorting (MACS).

Bexarotene drives the self-renewing proliferation of adult neural stem cells, promotes neuron-glial fate shift, and regulates late neuronal differentiation

Treatment with bexarotene, a selective retinoid X receptor (RXR) agonist, significantly improves behavioral dysfunctions in various neurodegenerative animal models. Additionally, it activates neurodevelopmental and plasticity pathways in the brains of adult mice. Our objective was to investigate the impact of RXR activation by bexarotene on adult neural stem cells (aNSC) and their cell lineages. To achieve this, we treated NSCs isolated from the subventricular zone (SVZ) of adult rat brains from the proliferative stage to the differentiated status. The results showed that bexarotene-treated aNSC exhibited increased BrdU incorporation, SOX2+ dividing cell pairs, and cell migration from neurospheres, revealing that the treatment promotes self-renewing proliferation and cell motility in SVZ-aNCS. Furthermore, bexarotene induced a cell fate shift characterized by a significant increase in GFAP+/S100B+ differentiated astrocytes, which uncovers the participation of activated-RXR in astrogenesis. In the neuronal lineage, the fate shift was counteracted by bexarotene-induced enhancement of NeuN+ nuclei together with neurite network outgrowth, indicating that the RXR agonist stimulates SVZ-aNCS neuronal differentiation at later stages. These findings establish new connections between RXR activation, astro- and neurogenesis in the adult brain, and contribute to the development of therapeutic strategies targeting nuclear receptors for neural repair.

Astrocyte-derived CHI3L1 signaling impairs neurogenesis and cognition in the demyelinated hippocampus

Cognitive dysfunction is a feature in multiple sclerosis (MS), a chronic inflammatory demyelinating disorder. A notable aspect of MS brains is hippocampal demyelination, which is closely associated with cognitive decline. However, the mechanisms underlying this phenomenon remain unclear. Chitinase-3-like (CHI3L1), secreted by activated astrocytes, has been identified as a biomarker for MS progression. Our study investigates CHI3L1's function within the demyelinating hippocampus and demonstrates a correlation between CHI3L1 expression and cognitive impairment in patients with MS. Activated astrocytes release CHI3L1 in reaction to induced demyelination, which adversely affects the proliferation and differentiation of neural stem cells and impairs dendritic growth, complexity, and spine formation in neurons. Our findings indicate that the astrocytic deletion of CHI3L1 can mitigate neurogenic deficits and cognitive dysfunction. We showed that CHI3L1 interacts with CRTH2/receptor for advanced glycation end (RAGE) by attenuating β-catenin signaling. The reactivation of β-catenin signaling can revitalize neurogenesis, which holds promise for therapy of inflammatory demyelination.

Sex-specific impacts of prenatal bisphenol A exposure on genes associated with cortical development, social behaviors, and autism in the offspring's prefrontal cortex

BACKGROUND

Recent studies have shown that prenatal BPA exposure altered the transcriptome profiles of autism-related genes in the offspring's hippocampus, disrupting hippocampal neuritogenesis and causing male-specific deficits in learning. However, the sex differences in the effects of prenatal BPA exposure on the developing prefrontal cortex, which is another brain region highly implicated in autism spectrum disorder (ASD), have not been investigated.

METHODS

We obtained transcriptome data from RNA sequencing analysis of the prefrontal cortex of male and female rat pups prenatally exposed to BPA or control and reanalyzed. BPA-responsive genes associated with cortical development and social behaviors were selected for confirmation by qRT-PCR analysis. Neuritogenesis of primary cells from the prefrontal cortex of pups prenatally exposed to BPA or control was examined. The social behaviors of the pups were assessed using the two-trial and three-chamber tests. The male-specific impact of the downregulation of a selected BPA-responsive gene (i.e., Sema5a) on cortical development in vivo was interrogated using siRNA-mediated knockdown by an in utero electroporation technique.

RESULTS

Genes disrupted by prenatal BPA exposure were associated with ASD and showed sex-specific dysregulation. Sema5a and Slc9a9, which were involved in neuritogenesis and social behaviors, were downregulated only in males, while Anxa2 and Junb, which were also linked to neuritogenesis and social behaviors, were suppressed only in females. Neuritogenesis was increased in males and showed a strong inverse correlation with Sema5a and Slc9a9 expression levels, whereas, in the females, neuritogenesis was decreased and correlated with Anxa2 and Junb levels. The siRNA-mediated knockdown of Sema5a in males also impaired cortical development in utero. Consistent with Anxa2 and Junb downregulations, deficits in social novelty were observed only in female offspring but not in males.

CONCLUSION

This is the first study to show that prenatal BPA exposure dysregulated the expression of ASD-related genes and functions, including cortical neuritogenesis and development and social behaviors, in a sex-dependent manner. Our findings suggest that, besides the hippocampus, BPA could also exert its adverse effects through sex-specific molecular mechanisms in the offspring's prefrontal cortex, which in turn would lead to sex differences in ASD-related neuropathology and clinical manifestations, which deserves further investigation.

Disrupted de novo pyrimidine biosynthesis impairs adult hippocampal neurogenesis and cognition in pyridoxine-dependent epilepsy

Despite seizure control by early high-dose pyridoxine (vitamin B6) treatment, at least 75% of pyridoxine-dependent epilepsy (PDE) patients with ALDH7A1 mutation still suffer from intellectual disability. It points to a need for additional therapeutic interventions for PDE beyond pyridoxine treatment, which provokes us to investigate the mechanisms underlying the impairment of brain hemostasis by ALDH7A1 deficiency. In this study, we show that ALDH7A1-deficient mice with seizure control exhibit altered adult hippocampal neurogenesis and impaired cognitive functions. Mechanistically, ALDH7A1 deficiency leads to the accumulation of toxic lysine catabolism intermediates, α-aminoadipic-δ-semialdehyde and its cyclic form, δ-1-piperideine-6-carboxylate, which in turn impair de novo pyrimidine biosynthesis and inhibit NSC proliferation and differentiation. Notably, supplementation of pyrimidines rescues abnormal neurogenesis and cognitive impairment in ALDH7A1-deficient adult mice. Therefore, our findings not only define the important role of ALDH7A1 in the regulation of adult hippocampal neurogenesis but also provide a potential therapeutic intervention to ameliorate the defective mental capacities in PDE patients with seizure control.

PRMT5-mediated homologous recombination repair is essential to maintain genomic integrity of neural progenitor cells

Maintaining genomic stability is a prerequisite for proliferating NPCs to ensure genetic fidelity. Though histone arginine methylation has been shown to play important roles in safeguarding genomic stability, the underlying mechanism during brain development is not fully understood. Protein arginine N-methyltransferase 5 (PRMT5) is a type II protein arginine methyltransferase that plays a role in transcriptional regulation. Here, we identify PRMT5 as a key regulator of DNA repair in response to double-strand breaks (DSBs) during NPC proliferation. Prmt5F/F; Emx1-Cre (cKO-Emx1) mice show a distinctive microcephaly phenotype, with partial loss of the dorsal medial cerebral cortex and complete loss of the corpus callosum and hippocampus. This phenotype is resulted from DSBs accumulation in the medial dorsal cortex followed by cell apoptosis. Both RNA sequencing and in vitro DNA repair analyses reveal that PRMT5 is required for DNA homologous recombination (HR) repair. PRMT5 specifically catalyzes H3R2me2s in proliferating NPCs in the developing mouse brain to enhance HR-related gene expression during DNA repair. Finally, overexpression of BRCA1 significantly rescues DSBs accumulation and cell apoptosis in PRMT5-deficient NSCs. Taken together, our results show that PRMT5 maintains genomic stability by regulating histone arginine methylation in proliferating NPCs.

Transcriptional and epigenetic dysregulation impairs generation of proliferative neural stem and progenitor cells during brain aging

The decline in stem cell function during aging may affect the regenerative capacity of mammalian organisms; however, the gene regulatory mechanism underlying this decline remains unclear. Here we show that the aging of neural stem and progenitor cells (NSPCs) in the male mouse brain is characterized by a decrease in the generation efficacy of proliferative NSPCs rather than the changes in lineage specificity of NSPCs. We reveal that the downregulation of age-dependent genes in NSPCs drives cell aging by decreasing the population of actively proliferating NSPCs while increasing the expression of quiescence markers. We found that epigenetic deregulation of the MLL complex at promoters leads to transcriptional inactivation of age-dependent genes, highlighting the importance of the dynamic interaction between histone modifiers and gene regulatory elements in regulating transcriptional program of aging cells. Our study sheds light on the key intrinsic mechanisms driving stem cell aging through epigenetic regulators and identifies potential rejuvenation targets that could restore the function of aging stem cells.

Isolation and Culture of Neural Stem/Progenitor Cells from the Hippocampal Dentate Gyrus of Young Adult and Aged Rats

Adult neural stem/progenitor cells (NSPCs) in two neurogenic areas of the brain, the dentate gyrus and the subventricular zone, are major players in adult neurogenesis. Addressing specific questions regarding NSPCs outside of their niche entails in vitro studies through isolation and culture of these cells. As there is heterogeneity in their morphology, proliferation, and differentiation capacity between these two neurogenic areas, NSPCs should be isolated from each area through specific procedures and media. Identifying region-specific NPSCs provides an accurate pathway for assessing the effects of extrinsic factors and drugs on these cells and investigating the mechanisms of neurogenesis in both healthy and pathologic conditions. A great number of isolation and expansion techniques for NSPCs have been reported. The growth and expansion of NSPCs obtained from the dentate gyrus of aged rats are generally difficult. There are relatively limited data and protocols about NSPCs isolation and their culture from aged rats. Our approach is an efficient and reliable strategy to isolate and expand NSPCs obtained from young adult and aged rats. NSPCs isolated by this method maintain their self-renewal and multipotency. Key features • NSPCs isolated from the hippocampal dentate gyrus of young adult and aged rats, based on Kempermann et al. (2014) and Aligholi et al. (2014). • Maintenance of NSPCs isolated from the dentate gyrus of aged rats (20-24 months) in our culture condition is feasible. • According to our protocol, maximum growth of primary neurospheres obtained from isolated NSPCs of young and aged rats took 15 and 35 days, respectively.

CHI3L1 signaling impairs hippocampal neurogenesis and cognitive function in autoimmune-mediated neuroinflammation

Chitinase-3-like protein 1 (CHI3L1) is primarily secreted by activated astrocytes in the brain and is known as a reliable biomarker for inflammatory central nervous system (CNS) conditions such as neurodegeneration and autoimmune disorders like neuromyelitis optica (NMO). NMO is an astrocyte disease caused by autoantibodies targeting the astroglial protein aquaporin 4 (AQP4) and leads to vision loss, motor deficits, and cognitive decline. In this study examining CHI3L1's biological function in neuroinflammation, we found that CHI3L1 expression correlates with cognitive impairment in our NMO patient cohort. Activated astrocytes secrete CHI3L1 in response to AQP4 autoantibodies, and this inhibits the proliferation and neuronal differentiation of neural stem cells. Mouse models showed decreased hippocampal neurogenesis and impaired learning behaviors, which could be rescued by depleting CHI3L1 in astrocytes. The molecular mechanism involves CHI3L1 engaging the CRTH2 receptor and dampening β-catenin signaling for neurogenesis. Blocking this CHI3L1/CRTH2/β-catenin cascade restores neurogenesis and improves cognitive deficits, suggesting the potential for therapeutic development in neuroinflammatory disorders.

Pleiotrophin ameliorates age-induced adult hippocampal neurogenesis decline and cognitive dysfunction

Cognitive impairment has been associated with an age-related decline in adult hippocampal neurogenesis (AHN). The molecular basis of declining neurogenesis in the aging hippocampus remains to be elucidated. Here, we show that pleiotrophin (PTN) expression is decreased with aging in neural stem and progenitor cells (NSPCs). Mice lacking PTN exhibit impaired AHN accompanied by poor learning and memory. Mechanistically, we find that PTN engages with protein tyrosine phosphatase receptor type Z1 (PTPRZ1) to promote NSPC proliferation and differentiation by activating AKT signaling. PTN overexpression or pharmacological activation of AKT signaling in aging mice restores AHN and alleviates relevant memory deficits. Importantly, we also find that PTN overexpression improves impaired neurogenesis in senescence-accelerated mouse prone 8 (SAMP8) mice. We further confirm that PTN is required for enriched environment-induced increases in AHN. These results corroborate the significance of AHN in aging and reveal a possible therapeutic intervention by targeting PTN.

Therapeutic Effect of a Hydrogel-based Neural Stem Cell Delivery Sheet for Mild Traumatic Brain Injury

OBJECTIVE

There are no effective clinically applicable treatments for neuronal dysfunction after mild traumatic brain injury (TBI). Here, we evaluated the therapeutic effect of a new delivery method of mouse neural stem cell (mNSC) spheroids using a hydrogel, in terms of improvement in damaged cortical lesions and cognitive impairment after mild TBI.

METHODS

mNSCs were isolated from the subventricular zone and subgranular zone by a hydrogel-based culture system. GFP-transduced mNSCs were generated into spheroids and wrapped into a sheet for transplantation. Male C57BL/6J mice were randomly divided into four groups: sham operation, TBI, TBI with mNSC spheroids, and TBI with mNSC spheroid sheet transplantation covering the damaged cortex. Histopathological and immunohistochemical features and cognitive function were evaluated 7, 14, and 28 days after transplantation following TBI.

RESULTS

Hydrogel-based culture systems and mNSC isolation were successfully established from the adult mice. Essential transcription factors for NSCs, such as SOX2, PAX6, Olig2, nestin, and doublecortin (DCX), were highly expressed in the mNSCs. A transplanted hydrogel-based mNSC spheroid sheet showed good engraftment and survival ability, differentiated into TUJ1-positive neurons, promoted angiogenesis, and reduced neuronal degeneration. Also, TBI mice treated with mNSC spheroid sheet transplantation exhibited a significantly increased preference for a new object, suggesting improved cognitive function compared to the mNSC spheroids or no treatment groups.

CONCLUSION

Transplantation with a hydrogel-based mNSC spheroid sheet showed engraftment, migration, and stability of delivered cells in a hostile microenvironment after TBI, resulting in improved cognitive function via reconstruction of the damaged cortex.

STATEMENT OF SIGNIFICANCE

This study presents the therapeutic effect of a new delivery method of mouse neural stem cells spheroids using a hydrogel, in terms of improvement in damaged cortical lesions and cognitive impairment after traumatic brain injury. Collagen/fibrin hydrogel allowed long-term survival and migratory ability of NSCs spheroids. Furthermore, transplanted hydrogel-based mNSCs spheroids sheet showed good engraftment, migration, and stability of delivered cells in a hostile microenvironment, resulting in reconstruction of the damaged cortex and improved cognitive function after TBI. Therefore, we suggest that a hydrogel-based mNSCs spheroids sheet could help to improve cognitive impairment after TBI.

Neural cell isolation from adult macaques for high-throughput analyses and neurosphere cultures

The low number of neural progenitor cells (NPCs) present in the adult and aged primate brains represents a challenge for generating high-yield and viable in vitro cultures of primary brain cells. Here we report a step-by-step approach for the fast and reproducible isolation of high-yield and viable primary brain cells, including mature neurons, immature cells and NPCs, from adult and aged macaques. We describe the anesthesia, transcardial perfusion and brain tissue preparation; the subsequent microdissection of the regions of interest and their enzymatic dissociation, leading to the separation of single cells. The cell isolation steps of our protocol can also be used for routine cell culturing, in particular for NPC expansion and differentiation, suitable for studies of hippocampal neurogenesis in the adult macaque brain. The purified primary brain cells are largely free from myelin debris and erythrocytes, paving the way for multiple downstream applications in vitro and in vivo. When combined with single-cell profiling techniques, this approach allows an unbiased and comprehensive mapping of cell states in the adult and aged macaque brain, which is needed to advance our understanding of human cognitive and neurological diseases. The neural cell isolation protocol requires 4 h and a team of four to six users with expertize in primary brain cell isolation to avoid tissue hypoxia during the time-sensitive steps of the procedure.

The Use of Stem Cells as a Potential Treatment Method for Selected Neurodegenerative Diseases: Review

Stem cells have been the subject of research for years due to their enormous therapeutic potential. Most neurological diseases such as multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD) are incurable or very difficult to treat. Therefore new therapies are sought in which autologous stem cells are used. They are often the patient's only hope for recovery or slowing down the progress of the disease symptoms. The most important conclusions arise after analyzing the literature on the use of stem cells in neurodegenerative diseases. The effectiveness of MSC cell therapy has been confirmed in ALS and HD therapy. MSC cells slow down ALS progression and show early promising signs of efficacy. In HD, they reduced huntingtin (Htt) aggregation and stimulation of endogenous neurogenesis. MS therapy with hematopoietic stem cells (HSCs) inducted significant recalibration of pro-inflammatory and immunoregulatory components of the immune system. iPSC cells allow for accurate PD modeling. They are patient-specific and therefore minimize the risk of immune rejection and, in long-term observation, did not form any tumors in the brain. Extracellular vesicles derived from bone marrow mesenchymal stromal cells (BM-MSC-EVs) and Human adipose-derived stromal/stem cells (hASCs) cells are widely used to treat AD. Due to the reduction of Aβ42 deposits and increasing the survival of neurons, they improve memory and learning abilities. Despite many animal models and clinical trial studies, cell therapy still needs to be refined to increase its effectiveness in the human body.

L-arginine homeostasis governs adult neural stem cell activation by modulating energy metabolism in vivo

Neurogenesis in the developing and adult brain is intimately linked to remodeling of cellular metabolism. However, it is still unclear how distinct metabolic programs and energy sources govern neural stem cell (NSC) behavior and subsequent neuronal differentiation. Here, we found that adult mice lacking the mitochondrial urea metabolism enzyme, Arginase-II (Arg-II), exhibited NSC overactivation, thereby leading to accelerated NSC pool depletion and decreased hippocampal neurogenesis over time. Mechanistically, Arg-II deficiency resulted in elevated L-arginine levels and induction of a metabolic shift from glycolysis to oxidative phosphorylation (OXPHOS) caused by impaired attachment of hexokinase-I to mitochondria. Notably, selective inhibition of OXPHOS ameliorated NSC overactivation and restored abnormal neurogenesis in Arg-II deficient mice. Therefore, Arg-II-mediated intracellular L-arginine homeostasis directly influences the metabolic fitness of neural stem cells that is essential to maintain neurogenesis with age.

D-2-hydroxyglutarate dehydrogenase governs adult neural stem cell activation and promotes histone acetylation via ATP-citrate lyase

The generation of neurons from quiescent radial-glia-like neural stem cells (RGLs) in adult brain goes hand in hand with the modulation of cellular metabolism. However, it is still unclear how the exact metabolic program governs the balance between quiescent and activated RGLs. Here, we find that loss of mitochondrial D-2-hydroxyglutarate dehydrogenase (D2HGDH) leads to aberrant accumulation of D-2-hydroxyglutarate (D-2-HG) and impaired RGL activation. Mechanistically, accumulated D-2-HG bonds directly to ATP-citrate lyase and competitively inhibits its enzymatic activity, thereby reducing acetyl-CoA production and diminishing histone acetylation. However, administration of acetate restores the acetyl-CoA levels via acetyl-CoA synthetase-mediated catabolism and rescues the deficiencies in histone acetylation and RGL activation caused by loss of D2HGDH. Therefore, our findings define the role of cross talk between mitochondria and the nucleus via a mitochondrial metabolite, D-2-HG, the aberrant accumulation of which hinders the regulation of histone acetylation in RGL activation and attenuates continuous neurogenesis in adult mammalian brain.

Histone Methyltransferase SETDB1 Regulates the Development of Cortical Htr3a-Positive Interneurons and Mood Behaviors

BACKGROUND

GABAergic (gamma-aminobutyric acidergic) interneurons (INs) are highly heterogeneous, and Htr3a labels a subpopulation of cortical INs originating from the embryonic caudal ganglionic eminence. SETDB1 is one of the histone H3K9 methyltransferases and plays an essential role in the excitatory neurons, but its role in regulating cortical inhibitory INs remains largely unknown.

METHODS

In this study, we generated transgenic mice with conditional knockout of Setdb1 in neural progenitor cells (Setdb1-NS-cKO) and GABAergic neurons (Setdb1-Gad2-cKO). In addition, we performed RNA sequencing, ATAC-seq (assay for transposase-accessible chromatin with sequencing), chromatin immunoprecipitation sequencing, luciferase assay, chromatin conformation capture, and CRISPR (clustered regularly interspaced short palindromic repeats)/dCas9 to study the epigenetic mechanism underlying SETDB1-mediated transcriptional regulation of Htr3a. We also performed in situ hybridization and whole-cell recording to evaluate the functional properties of cortical Htr3a+ INs and behavioral tests for mood.

RESULTS

We detected significant upregulation of Htr3a expression in the embryonic ganglionic eminence of Setdb1-NS-cKO and identified the endogenous retroviral sequence RMER21B as a new target of SETDB1. RMER21B showed enhancer activity and formed distal chromatin interaction with the promoter of Htr3a. In addition, we observed an increased number and enhanced excitability of Htr3a+ INs in the knockout cortex. Moreover, Setdb1-Gad2-cKO mice exhibited anxiety- and depressive-like behaviors, which were partially reversed by a 5-HT₃ receptor antagonist.

CONCLUSIONS

These findings suggest that SETDB1 represses Htr3a transcription via RMER21B-mediated distal chromatin interaction in the embryonic ganglionic eminence and regulates the development of cortical Htr3a+ INs and mood behaviors.

Differential vulnerability of adult neurogenic niches to dosage of the neurodevelopmental-disorder linked gene Foxg1

The transcription factor FOXG1 serves pleiotropic functions in brain development ranging from the regulation of precursor proliferation to the control of cortical circuit formation. Loss-of-function mutations and duplications of FOXG1 are associated with neurodevelopmental disorders in humans illustrating the importance of FOXG1 dosage for brain development. Aberrant FOXG1 dosage has been found to disrupt the balanced activity of glutamatergic and GABAergic neurons, but the underlying mechanisms are not fully understood. We report that FOXG1 is expressed in the main adult neurogenic niches in mice, i.e. the hippocampal dentate gyrus and the subependymal zone/olfactory bulb system, where neurogenesis of glutamatergic and GABAergic neurons persists into adulthood. These niches displayed differential vulnerability to increased FOXG1 dosage: high FOXG1 levels severely compromised survival and glutamatergic dentate granule neuron fate acquisition in the hippocampal neurogenic niche, but left neurogenesis of GABAergic neurons in the subependymal zone/olfactory bulb system unaffected. Comparative transcriptomic analyses revealed a significantly higher expression of the apoptosis-linked nuclear receptor Nr4a1 in FOXG1-overexpressing hippocampal neural precursors. Strikingly, pharmacological interference with NR4A1 function rescued FOXG1-dependent death of hippocampal progenitors. Our results reveal differential vulnerability of neuronal subtypes to increased FOXG1 dosage and suggest that activity of a FOXG1/NR4A1 axis contributes to such subtype-specific response.

Disruption of Sonic Hedgehog Signaling Accelerates Age-Related Neurogenesis Decline and Abolishes Stroke-Induced Neurogenesis and Leads to Increased Anxiety Behavior in Stroke Mice

Sonic Hedgehog (SHH) signaling has a critical role in mediating developmental neurogenesis and has been implicated in adult subventricular (SVZ) neurogenesis. However, the precise role of Smoothened (SMO) receptor-mediated SHH signaling in adult neurogenesis during aging especially in hippocampal subgranular zone (SGZ) neurogenesis remains undefined. Additionally, our previous study showed that stimulation of SHH signaling post-stroke leads to increased neurogenesis and improved behavioral functions after stroke. However, it is not clear whether SHH signaling in neural stem cells (NSCs) is required for stroke-induced neurogenesis and functional recovery post-stroke. In this study, using conditional knockout (cKO) of SHH signaling receptor Smo gene in NSCs, we show a decreased neurogenesis at both SVZ and SGZ in young-adult mice and an accelerated depletion of neurogenic cells in the process of aging suggesting that SHH signaling is critical in maintaining neurogenesis during aging. Behavior studies revealed that compromised neurogenesis in Smo cKO mice leads to increased anxiety/depression-like behaviors without affecting general locomotor function or spatial and fear-related learning. Importantly, we also show that NSCs with a cKO of SHH signaling abolishes stroke-induced neurogenesis in Smo cKO mice. Compared to control mice, Smo cKO mice also show delayed motor function recovery and increased anxiety level after stroke. Our data highlights the essential role of Smo function in regulating adult neurogenesis and emotional behaviors during both aging and CNS injury such as stroke.

Topoisomerase IIA in adult NSCs regulates SVZ neurogenesis by transcriptional activation of Usp37

Topoisomerase IIA (TOP2a) has traditionally been known as an important nuclear enzyme that resolves entanglements and relieves torsional stress of DNA double strands. However, its function in genomic transcriptional regulation remains largely unknown, especially during adult neurogenesis. Here, we show that TOP2a is preferentially expressed in neurogenic niches in the brain of adult mice, such as the subventricular zone (SVZ). Conditional knockout of Top2a in adult neural stem cells (NSCs) of the SVZ significantly inhibits their self-renewal and proliferation, and ultimately reduces neurogenesis. To gain insight into the molecular mechanisms by which TOP2a regulates adult NSCs, we perform RNA-sequencing (RNA-Seq) plus chromatin immunoprecipitation sequencing (ChIP-Seq) and identify ubiquitin-specific protease 37 (Usp37) as a direct TOP2a target gene. Importantly, overexpression of Usp37 is sufficient to rescue the impaired self-renewal ability of adult NSCs caused by Top2a knockdown. Taken together, this proof-of-principle study illustrates a TOP2a/Usp37-mediated novel molecular mechanism in adult neurogenesis, which will significantly expand our understanding of the function of topoisomerase in the adult brain.

Astrocytic Piezo1-mediated mechanotransduction determines adult neurogenesis and cognitive functions

Adult brain activities are generally believed to be dominated by chemical and electrical transduction mechanisms. However, the importance of mechanotransduction mediated by mechano-gated ion channels in brain functions is less appreciated. Here, we show that the mechano-gated Piezo1 channel is expressed in the exploratory processes of astrocytes and utilizes its mechanosensitivity to mediate mechanically evoked Ca²⁺ responses and ATP release, establishing Piezo1-mediated mechano-chemo transduction in astrocytes. Piezo1 deletion in astrocytes causes a striking reduction of hippocampal volume and brain weight and severely impaired (but ATP-rescuable) adult neurogenesis in vivo, and it abolishes ATP-dependent potentiation of neural stem cell (NSC) proliferation in vitro. Piezo1-deficient mice show impaired hippocampal long-term potentiation (LTP) and learning and memory behaviors. By contrast, overexpression of Piezo1 in astrocytes sufficiently enhances mechanotransduction, LTP, and learning and memory performance. Thus, astrocytes utilize Piezo1-mediated mechanotransduction mechanisms to robustly regulate adult neurogenesis and cognitive functions, conceptually highlighting the importance of mechanotransduction in brain structure and function.

The effects of Bone Morphogenetic Protein 4 on adult neural stem cell proliferation, differentiation and survival in an in vitro model of ischemic stroke

The subventricular zone (SVZ) of the lateral ventricles represents a main region where neural stem cells (NSCs) of the mature central nervous system (CNS) reside. Bone Morphogenetic Proteins (BMPs) are the largest subclass of the transforming growth factor-β (TGF-β) superfamily of ligands. BMP4 is one such member and plays important roles in adult NSC differentiation. However, the exact effects of BMP4 on SVZ adult NSCs in CNS ischemia are still unknown. Using oxygen and glucose deprivation (OGD) as an in vitro model of ischemia, we examined the behavior of adult NSCs. We observed that anoxia resulted in reduced viability of adult NSCs, and that BMP4 treatment clearly rescued apoptotic cell death following anoxia. Furthermore, BMP4 treatment exhibited a strong inhibitory effect on cellular proliferation of the adult NSCs in normoxic conditions. Moreover, such inhibitory effects of BMP4 treatment were also found in OGD conditions, despite the enhanced cellular proliferation of the adult NSCs that was observed under such ischemic conditions. Increased neuronal and astroglial commitment of adult NSCs were found in the OGD conditions, whereas a reduction in differentiated neurons and an increase in differentiated astrocytes were observed following BMP4 treatment. The present data indicate that BMP4 modulates proliferation and differentiation of SVZ-derived adult NSCs and promotes cell survival in the in vitro model of ischemic stroke.

Cerebral endothelial cell derived small extracellular vesicles improve cognitive function in aged diabetic rats

Small extracellular vesicles (sEVs) mediate cell-cell communication by transferring their cargo biological materials into recipient cells. Diabetes mellitus (DM) induces cerebral vascular dysfunction and neurogenesis impairment, which are associated with cognitive decline and an increased risk of developing dementia. Whether the sEVs are involved in DM-induced cerebral vascular disease, is unknown. Therefore, we studied sEVs derived from cerebral endothelial cells (CEC-sEVs) of aged DM rats (DM-CEC-sEVs) and found that DM-CEC-sEVs robustly inhibited neural stem cell (NSC) generation of new neuroblasts and damaged cerebral endothelial function. Treatment of aged DM-rats with CEC-sEVs derived from adult healthy normal rats (N-CEC-sEVs) ameliorated cognitive deficits and improved cerebral vascular function and enhanced neurogenesis. Intravenously administered N-CEC-sEVs crossed the blood brain barrier and were internalized by neural stem cells in the neurogenic region, which were associated with augmentation of miR-1 and –146a and reduction of myeloid differentiation primary response gene 88 and thrombospondin 1 proteins. In addition, uptake of N-CEC-sEVs by the recipient cells was mediated by clathrin and caveolin dependent endocytosis signaling pathways. The present study provides ex vivo and in vivo evidence that DM-CEC-sEVs induce cerebral vascular dysfunction and neurogenesis impairment and that N-CEC-sEVs have a therapeutic effect on improvement of cognitive function by ameliorating dysfunction of cerebral vessels and increasing neurogenesis in aged DM rats, respectively.

Molecular signatures and cellular diversity during mouse habenula development

The habenula plays a key role in various motivated and pathological behaviors and is composed of molecularly distinct neuron subtypes. Despite progress in identifying mature habenula neuron subtypes, how these subtypes develop and organize into functional brain circuits remains largely unknown. Here, we performed single-cell transcriptional profiling of mouse habenular neurons at critical developmental stages, instructed by detailed three-dimensional anatomical data. Our data reveal cellular and molecular trajectories during embryonic and postnatal development, leading to different habenular subtypes. Further, based on this analysis, our work establishes the distinctive functional properties and projection target of a subtype of Cartpt⁺ habenula neurons. Finally, we show how comparison of single-cell transcriptional profiles and GWAS data links specific developing habenular subtypes to psychiatric disease. Together, our study begins to dissect the mechanisms underlying habenula neuron subtype-specific development and creates a framework for further interrogation of habenular development in normal and disease states.

Xenogenic Neural Stem Cell-Derived Extracellular Nanovesicles Modulate Human Mesenchymal Stem Cell Fate and Reconstruct Metabolomic Structure

Extracellular nanovesicles, particularly exosomes, can deliver their diverse bioactive biomolecular content, including miRNAs, proteins, and lipids, thus providing a context for investigating the capability of exosomes to induce stem cells toward lineage-specific cells and tissue regeneration. In this study, it is demonstrated that rat subventricular zone neural stem cell-derived exosomes (rSVZ-NSCExo) can control neural-lineage specification of human mesenchymal stem cells (hMSCs). Microarray analysis shows that the miRNA content of rSVZ-NSCExo is a faithful representation of rSVZ tissue. Through immunocytochemistry, gene expression, and multi-omics analyses, the capability to use rSVZ-NSCExo to induce hMSCs into a neuroglial or neural stem cell phenotype and genotype in a temporal and dose-dependent manner via multiple signaling pathways is demonstrated. The current study presents a new and innovative strategy to modulate hMSCs fate by harnessing the molecular content of exosomes, thus suggesting future opportunities for rSVZ-NSCExo in nerve tissue regeneration.

Sustained correction of hippocampal neurogenic and cognitive deficits after a brief treatment by Nutlin-3 in a mouse model of fragile X syndrome

BACKGROUND

Fragile X syndrome (FXS), the most prevalent inherited intellectual disability and one of the most common monogenic forms of autism, is caused by a loss of fragile X messenger ribonucleoprotein 1 (FMR1). We have previously shown that FMR1 represses the levels and activities of ubiquitin ligase MDM2 in young adult FMR1-deficient mice, and treatment by a MDM2 inhibitor Nutlin-3 rescues both hippocampal neurogenic and cognitive deficits in FMR1-deficient mice when analyzed shortly after the administration. However, it is unknown whether Nutlin-3 treatment can have long-lasting therapeutic effects.

METHODS

We treated 2-month-old young adult FMR1-deficient mice with Nutlin-3 for 10 days and then assessed the persistent effect of Nutlin-3 on both cognitive functions and adult neurogenesis when mice were 6-month-old mature adults. To investigate the mechanisms underlying the persistent effects of Nutlin-3, we analyzed the proliferation and differentiation of neural stem/progenitor cells isolated from these mice and assessed the transcriptome of the hippocampal tissues of treated mice.

RESULTS

We found that transient treatment with Nutlin-3 of 2-month-old young adult FMR1-deficient mice prevents the emergence of neurogenic and cognitive deficits in mature adult FXS mice at 6 months of age. We further found that the long-lasting restoration of neurogenesis and cognitive function might not be mediated by changing intrinsic properties of adult neural stem cells. Transcriptomic analysis of the hippocampal tissue demonstrated that transient Nultin-3 treatment leads to significant expression changes in genes related to the extracellular matrix, secreted factors, and cell membrane proteins in the FMR1-deficient hippocampus.

CONCLUSIONS

Our data indicates that transient Nutlin-3 treatment in young adults leads to long-lasting neurogenic and behavioral changes likely through modulating adult neurogenic niche that impact adult neural stem cells. Our results demonstrate that cognitive impairments in FXS may be prevented by an early intervention through Nutlin-3 treatment.

A pathogenic DYT-THAP1 dystonia mutation causes hypomyelination and loss of YY1 binding

Dystonia is a disabling disease that manifests as prolonged involuntary twisting movements. DYT-THAP1 is an inherited form of isolated dystonia caused by mutations in THAP1 encoding the transcription factor THAP1. The phe81leu (F81L) missense mutation is representative of a category of poorly understood mutations that do not occur on residues critical for DNA binding. Here, we demonstrate that the F81L mutation (THAP1F81L) impairs THAP1 transcriptional activity and disrupts CNS myelination. Strikingly, THAP1F81L exhibits normal DNA binding but causes a significantly reduced DNA binding of YY1, its transcriptional partner that also has an established role in oligodendrocyte lineage progression. Our results suggest a model of molecular pathogenesis whereby THAP1F81L normally binds DNA but is unable to efficiently organize an active transcription complex.

Sirt1 protects subventricular zone derived neural stem cells from DNA double strand breaks and contributes to olfactory function maintenance in aging mice

DNA damage is assumed to accumulate in stem cells over time and their ability to withstand this damage and maintain tissue homeostasis is a key determinant of aging. Nonetheless, relatively few studies have investigated whether DNA damage does indeed accumulate in stem cells and whether this contributes to stem cell aging and functional decline. Here, we found that, compared with young mice, DNA double strand breaks (DSBs) are reduced in subventricular zone (SVZ)-derived neural stem cells (NSCs) of aged mice, which was achieved partly through the adaptive upregulation of Sirt1 expression and non-homologous end joining (NHEJ)-mediated DNA repair. Sirt1 deficiency abolished this effect, leading to stem cell exhaustion, olfactory memory decline, and accelerated aging. The reduced DSBs and the upregulation of Sirt1 expression in SVZ-derived NSCs with age may represent a compensatory mechanism that evolved to protect stem cells from excessive DNA damage, as well as mitigate memory loss and other stresses during aging.

Metabolic control of adult neural stem cell self-renewal by the mitochondrial protease YME1L

The transition between quiescence and activation in neural stem and progenitor cells (NSPCs) is coupled with reversible changes in energy metabolism with key implications for lifelong NSPC self-renewal and neurogenesis. How this metabolic plasticity is ensured between NSPC activity states is unclear. We find that a state-specific rewiring of the mitochondrial proteome by the i-AAA peptidase YME1L is required to preserve NSPC self-renewal. YME1L controls the abundance of numerous mitochondrial substrates in quiescent NSPCs, and its deletion activates a differentiation program characterized by broad metabolic changes causing the irreversible shift away from a fatty-acid-oxidation-dependent state. Conditional Yme1l deletion in adult NSPCs in vivo results in defective self-renewal and premature differentiation, ultimately leading to NSPC pool depletion. Our results disclose an important role for YME1L in coordinating the switch between metabolic states of NSPCs and suggest that NSPC fate is regulated by compartmentalized changes in protein network dynamics.

Routine culture and study of adult human brain cells from neurosurgical specimens

When modeling disease in the laboratory, it is important to use clinically relevant models. Patient-derived human brain cells grown in vitro to study and test potential treatments provide such a model. Here, we present simple, highly reproducible coordinated procedures that can be used to routinely culture most cell types found in the human brain from single neurosurgically excised brain specimens. The cell types that can be cultured include dissociated cultures of neurons, astrocytes, microglia, pericytes and brain endothelial and neural precursor cells, as well as explant cultures of the leptomeninges, cortical slice cultures and brain tumor cells. The initial setup of cultures takes ~2 h, and the cells are ready for further experiments within days to weeks. The resulting cells can be studied as purified or mixed population cultures, slice cultures and explant-derived cultures. This protocol therefore enables the investigation of human brain cells to facilitate translation of neuroscience research to the clinic.

Integrative analysis of the 3D genome structure reveals that CTCF maintains the properties of mouse female germline stem cells

The three-dimensional configuration of the genome ensures cell type-specific gene expression profiles by placing genes and regulatory elements in close spatial proximity. Here, we used in situ high-throughput chromosome conformation (in situ Hi-C), RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) to characterize the high-order chromatin structure signature of female germline stem cells (FGSCs) and identify its regulating key factor based on the data-driven of multiple omics data. By comparison with pluripotent stem cells (PSCs), adult stem cells (ASCs), and somatic cells at three major levels of chromatin architecture, A/B compartments, topologically associating domains, and chromatin loops, the chromatin architecture of FGSCs was most similar to that of other ASCs and largely different from that of PSCs and somatic cells. After integrative analysis of the three-dimensional chromatin structure, active compartment-associating loops (aCALs) were identified as a signature of high-order chromatin organization in FGSCs, which revealed that CCCTC-binding factor was a major factor to maintain the properties of FGSCs through regulation of aCALs. We found FGSCs belong to ASCs at chromatin structure level and characterized aCALs as the high-order chromatin structure signature of FGSCs. Furthermore, CTCF was identified to play a key role in regulating aCALS to maintain the biological functions of FGSCs. These data provide a valuable resource for future studies of the features of chromatin organization in mammalian stem cells and further understanding of the fundamental characteristics of FGSCs.

Autism-Related Transcription Factors Underlying the Sex-Specific Effects of Prenatal Bisphenol A Exposure on Transcriptome-Interactome Profiles in the Offspring Prefrontal Cortex

Bisphenol A (BPA) is an environmental risk factor for autism spectrum disorder (ASD). BPA exposure dysregulates ASD-related genes in the hippocampus and neurological functions of offspring. However, whether prenatal BPA exposure has an impact on genes in the prefrontal cortex, another brain region highly implicated in ASD, and through what mechanisms have not been investigated. Here, we demonstrated that prenatal BPA exposure disrupts the transcriptome-interactome profiles of the prefrontal cortex of neonatal rats. Interestingly, the list of BPA-responsive genes was significantly enriched with known ASD candidate genes, as well as genes that were dysregulated in the postmortem brain tissues of ASD cases from multiple independent studies. Moreover, several differentially expressed genes in the offspring's prefrontal cortex were the targets of ASD-related transcription factors, including AR, ESR1, and RORA. The hypergeometric distribution analysis revealed that BPA may regulate the expression of such genes through these transcription factors in a sex-dependent manner. The molecular docking analysis of BPA and ASD-related transcription factors revealed novel potential targets of BPA, including RORA, SOX5, TCF4, and YY1. Our findings indicated that prenatal BPA exposure disrupts ASD-related genes in the offspring's prefrontal cortex and may increase the risk of ASD through sex-dependent molecular mechanisms, which should be investigated further.

Telomerase Reverse Transcriptase Preserves Neuron Survival and Cognition in Alzheimer's Disease Models

Amyloid-induced neurodegeneration plays a central role in Alzheimer's disease (AD) pathogenesis. Here, we show that telomerase reverse transcriptase (TERT) haploinsufficiency decreases BDNF and increases amyloid-β (Aβ) precursor in murine brain. Moreover, prior to disease onset, the TERT locus sustains accumulation of repressive epigenetic marks in murine and human AD neurons, implicating TERT repression in amyloid-induced neurodegeneration. To test the impact of sustained TERT expression on AD pathobiology, AD mouse models were engineered to maintain physiological levels of TERT in adult neurons, resulting in reduced Aβ accumulation, improved spine morphology, and preserved cognitive function. Mechanistically, integrated profiling revealed that TERT interacts with β-catenin and RNA polymerase II at gene promoters and upregulates gene networks governing synaptic signaling and learning processes. These TERT-directed transcriptional activities do not require its catalytic activity nor telomerase RNA. These findings provide genetic proof-of-concept for somatic TERT gene activation therapy in attenuating AD progression including cognitive decline.

Dl-3-N-Butylphthalide Attenuates Hypoxic Injury of Neural Stem Cells by Increasing Hypoxia-Inducible Factor-1alpha

OBJECTIVE

To assess the potential effect of dl-3-N-butylphthalide (dl-NBP) for the proliferation and differentiation of neural stem cells (NSCs) against hypoxia and the underlying mechanism.

MATERIALS AND METHODS

Hippocampal NSCs were obtained from fetal rats. NSCs combined with dl-NBP and single NSCs were cultured. The impact of siRNA-mediated hypoxia-inducible factor-1alpha (HIF-1α) knockdown on NSCs was detected with western blotting (WB) and quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR). Cell-counting kit-8 assay was used for evaluating the viability of NSCs. Levels of HIF-1α protein were measured using WB, and vascular endothelial growth factor (VEGF) expression was quantified using RT-qPCR and enzyme-linked immunosorbent assay.

RESULTS

Compared with 7 different concentrations of dl-NBP, 0.25 g/L was determined as the optimal concentration to significantly increase the viability of NSCs (p < 0.001). Dl-NBP can significantly increase the viability of hypoxic NSCs (p < 0.001) and improve the differentiation of hypoxic NSCs into astrocytes (p = 0.001) and oligodendrocytes (p < 0.001). Meanwhile, Dl-NBP can significantly elevate levels of HIF-1α protein (p < 0.001) and VEGF mRNA (p = 0.001) / protein (p < 0.001) in NSCs in the hypoxic environment. However, after transfection with HIF-1α siRNA in NSCs, the viability and differentiation of NSCs was not recovered using dl-NBP under the hypoxic condition, as well as levels of HIF-1α and VEGF.

CONCLUSION

Dl-NBP can reverse the weaker proliferation and differentiation power of NSCs in the hypoxic environment. The HIF-1α - VEGF pathway may be implicated in this protective effect of dl-NBP.

Reduction of Tet2 exacerbates early stage Alzheimer's pathology and cognitive impairments in 2×Tg-AD mice

Abnormal modification of 5-hydroxymethylcytosine (5hmC) is closely related to the occurrence of Alzheimer's disease (AD). However, the role of 5hmC and its writers, ten-eleven translocation (Tet) proteins, in regulating the pathogenesis of AD remains largely unknown. We detected a significant decrease in 5hmC and Tet2 levels in the hippocampus of aged APPswe/PSEN1 double-transgenic (2×Tg-AD) mice that coincides with abundant amyloid-β (Aβ) plaque accumulation. On this basis, we examined the reduction of Tet2 expression in the hippocampus at early disease stages, which caused a decline of 5hmC levels and led young 2×Tg-AD mice to present with advanced stages of AD-related pathological hallmarks, including Aβ accumulation, GFAP-positive astrogliosis and Iba1-positive microglia overgrowth as well as the overproduction of pro-inflammatory factors. Additionally, the loss of Tet2 in the 2×Tg-AD mice at 5 months of age accelerated hippocampal-dependent learning and memory impairments compared to age-matched control 2×Tg-AD mice. In contrast, restoring Tet2 expression in adult neural stem cells isolated from aged 2×Tg-AD mice hippocampi increased 5hmC levels and increased their regenerative capacity, suggesting that Tet2 might be an exciting target for rejuvenating the brain during aging and AD. Further, hippocampal RNA sequencing data revealed that the expression of altered genes identified in both Tet2 knockdown and control 2×Tg-AD mice was significantly associated with inflammation response. Finally, we demonstrated that Tet2-mediated 5hmC epigenetic modifications regulate AD pathology by interacting with HDAC1. These results suggest a combined approach for the regulation and treatment of AD-related memory impairment and cognitive symptoms by increasing Tet2 via HDAC1 suppression.

Exercise hormone irisin is a critical regulator of cognitive function

Identifying secreted mediators that drive the cognitive benefits of exercise holds great promise for the treatment of cognitive decline in ageing or Alzheimer's disease (AD). Here, we show that irisin, the cleaved and circulating form of the exercise-induced membrane protein FNDC5, is sufficient to confer the benefits of exercise on cognitive function. Genetic deletion of Fndc5/irisin (global Fndc5 knock-out (KO) mice; F5KO) impairs cognitive function in exercise, ageing and AD. Diminished pattern separation in F5KO mice can be rescued by delivering irisin directly into the dentate gyrus, suggesting that irisin is the active moiety. In F5KO mice, adult-born neurons in the dentate gyrus are morphologically, transcriptionally and functionally abnormal. Importantly, elevation of circulating irisin levels by peripheral delivery of irisin via adeno-associated viral overexpression in the liver results in enrichment of central irisin and is sufficient to improve both the cognitive deficit and neuropathology in AD mouse models. Irisin is a crucial regulator of the cognitive benefits of exercise and is a potential therapeutic agent for treating cognitive disorders including AD.

Isolation of adult mouse hippocampal neural stem cells for fluorescence loss in photobleaching assays

This protocol describes the isolation and culturing of primary neural stem cells (NSCs) from the adult mouse hippocampus, followed by the experimental approach for fluorescence loss in photobleaching assays, previously used to characterize the presence of an endoplasmic reticulum (ER) membrane diffusion barrier. The assay described here can be used to study live asymmetry in the ER membrane or other organelles that is established in dividing NSCs.

For complete details on the use and execution of this protocol, please refer to Clay et al. (2014); bin Imtiaz et al. (2021); Lee et al. (2016); Luedeke et al. (2005); Moore et al. (2015); Shcheprova et al. (2008).

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Protocol describes the isolation of hippocampal neural stem cells (NSCs)

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Approach to culture NSCs for fluorescence loss in photobleaching (FLIP) assays

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FLIP assays of NSCs explained step by step

Heme Oxygenase 1 Inhibits Adult Neural Stem Cells Proliferation and Survival via Modulation of Wnt/β-Catenin Signaling

BACKGROUND

Adult hippocampal neurogenesis is critical for renewing hippocampal neural circuits and maintaining hippocampal cognitive function and is closely associated with age-related neurodegenerative diseases. Heme oxygenase 1 (HO-1) is a stress protein that catalyzes the degradation of heme into free iron, biliverdin, and carbon monoxide. Elevated HO-1 level constitutes a pathological feature of Alzheimer's disease, Parkinson's disease, and many other age-related neurodegenerative diseases.

OBJECTIVE

Here we research the precise role of HO-1 in adult hippocampal neurogenesis.

METHODS

To explore the effect of HO-1 overexpression on adult neural stem cells (aNSCs) and elucidate its mechanisms, Tg(HO-1) was constructed. The transgenic mice and aNSCs were subjected to neurosphereing assay, clonal analysis, and BrdU labelling to detect the proliferation and self-renewal ability. LiCl, MG132, CHX, and IGF-1 treatment were used to research the signaling pathways which regulated by HO-1.

RESULTS

HO-1 overexpression decreased proliferation ability and induced apoptosis of aNSCs in subgranular zoon (SGZ) in vivo and in vitro. Furthermore, HO-1 overexpression inactivated canonical WNT/β-catenin pathway. Re-activate canonical WNT/β-catenin pathway rescued aNSCs proliferation and survival upon HO-1 overexpression. More importantly, phosphorylation of AKTS473 and GSK3βS9 was found to be significantly decreased in HO-1 overexpressed aNSCs. Re-activation of AKT signaling proved that HO-1 inhibited Wnt/β-catenin signaling pathway via AKT/GSK3β signaling pathway.

CONCLUSION

These results demonstrated a critical role of HO-1 in regulating aNSCs survival and proliferation by inhibiting Wnt/β-catenin pathway through repression of AKT/GSK3β, which provide a novel insight into the role of HO-1 in Alzheimer's disease pathogenesis.

Protocol for mouse adult neural stem cell isolation and culture

This protocol entails a simple method for isolation, culturing, and in vitro differentiation of adult neural stem cells from the dentate gyrus in the hippocampus and the subventricular zone of adult mice. Cultured adult neural stem cells are an important in vitro model to investigate stem cell properties such as proliferation and differentiation and to expand the understanding of plasticity in the adult brain.

For complete details on the use and execution of this protocol, please refer to Isaksen et al. (2020).

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A simple protocol for mouse adult neural stem cell isolation and culture

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Targeted differentiation into various neural cells

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Potential use of derived cells for studying brain plasticity

Nuclear isoform of FGF13 regulates post-natal neurogenesis in the hippocampus through an epigenomic mechanism

The hippocampus is one of two niches in the mammalian brain with persistent neurogenesis into adulthood. The neurogenic capacity of hippocampal neural stem cells (NSCs) declines with age, but the molecular mechanisms of this process remain unknown. In this study, we find that fibroblast growth factor 13 (FGF13) is essential for the post-natal neurogenesis in mouse hippocampus, and FGF13 deficiency impairs learning and memory. In particular, we find that FGF13A, the nuclear isoform of FGF13, is involved in the maintenance of NSCs and the suppression of neuronal differentiation during post-natal hippocampal development. Furthermore, we find that FGF13A interacts with ARID1B, a unit of Brahma-associated factor chromatin remodeling complex, and suppresses the expression of neuron differentiation-associated genes through chromatin modification. Our results suggest that FGF13A is an important regulator for maintaining the self-renewal and neurogenic capacity of NSCs in post-natal hippocampus, revealing an epigenomic regulatory function of FGFs in neurogenesis.

Simultaneous binding of Guidance Cues NET1 and RGM blocks extracellular NEO1 signaling

During cell migration or differentiation, cell surface receptors are simultaneously exposed to different ligands. However, it is often unclear how these extracellular signals are integrated. Neogenin (NEO1) acts as an attractive guidance receptor when the Netrin-1 (NET1) ligand binds, but it mediates repulsion via repulsive guidance molecule (RGM) ligands. Here, we show that signal integration occurs through the formation of a ternary NEO1-NET1-RGM complex, which triggers reciprocal silencing of downstream signaling. Our NEO1-NET1-RGM structures reveal a "trimer-of-trimers" super-assembly, which exists in the cell membrane. Super-assembly formation results in inhibition of RGMA-NEO1-mediated growth cone collapse and RGMA- or NET1-NEO1-mediated neuron migration, by preventing formation of signaling-compatible RGM-NEO1 complexes and NET1-induced NEO1 ectodomain clustering. These results illustrate how simultaneous binding of ligands with opposing functions, to a single receptor, does not lead to competition for binding, but to formation of a super-complex that diminishes their functional outputs.

Applying real-time monitoring of circadian oscillations in adult mouse brain slices to study communications between brain regions

This protocol combines a protective cutting method to prepare various brain slices from adult mice and real-time monitoring of circadian oscillations to measure circadian rhythmicity in various brain slices. This protocol can be applied to studies of how brain damages affect local circadian clocks and subsequent circadian variations in nearby areas. Further functional analyses with in vivo systems will determine whether these circadian variations are detrimental or beneficial to the brain.

For complete details on the use and execution of this protocol, please refer to Huang et al. (2020).

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Protective cutting method of the adult brain to minimize neural cell damages

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Co-culture system to study communications between different brain areas

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Monitoring circadian oscillations in non-SCN brain areas

On the role of p53 in the cellular response to aneuploidy

Most solid tumors are aneuploid, and p53 has been implicated as the guardian of the euploid genome. Previous experiments using human cell lines showed that aneuploidy induction leads to p53 accumulation and p21-mediated G1 cell cycle arrest. We find that adherent 2-dimensional (2D) cultures of human immortalized or cancer cell lines activate p53 upon aneuploidy induction, whereas suspension cultures of a human lymphoid cell line undergo a p53-independent cell cycle arrest. Surprisingly, 3D human and mouse organotypic cultures from neural, intestinal, or mammary epithelial tissues do not activate p53 or arrest in G1 following aneuploidy induction. p53-deficient colon organoids have increased aneuploidy and frequent lagging chromosomes and multipolar spindles during mitosis. These data suggest that p53 may not act as a universal surveillance factor restricting the proliferation of aneuploid cells but instead helps directly or indirectly ensure faithful chromosome transmission likely by preventing polyploidization and influencing spindle mechanics.

Enriched Environment Promotes Adult Hippocampal Neurogenesis through FGFRs

The addition of new neurons to existing neural circuits in the adult brain remains of great interest to neurobiology because of its therapeutic implications. The premier model for studying this process has been the hippocampal dentate gyrus in mice, where new neurons are added to mature circuits during adulthood. Notably, external factors such as an enriched environment (EE) and exercise markedly increase hippocampal neurogenesis. Here, we demonstrate that EE acts by increasing fibroblast growth factor receptor (FGFR) function autonomously within neurogenic cells to expand their numbers in adult male and female mice. FGFRs activated by EE signal through their mediators, FGFR substrate (FRS), to induce stem cell proliferation, and through FRS and phospholipase Cγ to increase the number of adult-born neurons, providing a mechanism for how EE promotes adult neurogenesis.SIGNIFICANCE STATEMENT How the environment we live in affects cognition remains poorly understood. In the current study, we explore the mechanism underlying the effects of an enriched environment on the production of new neurons in the adult hippocampal dentate gyrus, a brain area integral in forming new memories. A mechanism is provided for how neural precursor cells in the adult mammalian dentate gyrus respond to an enriched environment to increase their neurogenic output. Namely, an enriched environment acts on stem and progenitor cells by activating fibroblast growth factor receptor signaling through phospholipase Cγ and FGF receptor substrate proteins to expand the pool of precursor cells.

Insight Into the Mechanisms and the Challenges on Stem Cell-Based Therapies for Cerebral Ischemic Stroke

Strokes are the most common types of cerebrovascular disease and remain a major cause of death and disability worldwide. Cerebral ischemic stroke is caused by a reduction in blood flow to the brain. In this disease, two major zones of injury are identified: the lesion core, in which cells rapidly progress toward death, and the ischemic penumbra (surrounding the lesion core), which is defined as hypoperfusion tissue where cells may remain viable and can be repaired. Two methods that are approved by the Food and Drug Administration (FDA) include intravenous thrombolytic therapy and endovascular thrombectomy, however, the narrow therapeutic window poses a limitation, and therefore a low percentage of stroke patients actually receive these treatments. Developments in stem cell therapy have introduced renewed hope to patients with ischemic stroke due to its potential effect for reversing the neurological sequelae. Over the last few decades, animal tests and clinical trials have been used to treat ischemic stroke experimentally with various types of stem cells. However, several technical and ethical challenges must be overcome before stem cells can become a choice for the treatment of stroke. In this review, we summarize the mechanisms, processes, and challenges of using stem cells in stroke treatment. We also discuss new developing trends in this field.

Long-term exposure to a hypomagnetic field attenuates adult hippocampal neurogenesis and cognition

Adult hippocampal neurogenesis contributes to learning and memory, and is sensitive to a variety of environmental stimuli. Exposure to a hypomagnetic field (HMF) influences the cognitive processes of various animals, from insects to human beings. However, whether HMF exposure affect adult hippocampal neurogenesis and hippocampus-dependent cognitions is still an enigma. Here, we showed that male C57BL/6 J mice exposed to HMF by means of near elimination of the geomagnetic field (GMF) exhibit significant impairments of adult hippocampal neurogenesis and hippocampus-dependent learning, which is strongly correlated with a reduction in the content of reactive oxygen species (ROS). However, these deficits seen in HMF-exposed mice could be rescued either by elevating ROS levels through pharmacological inhibition of ROS removal or by returning them back to GMF. Therefore, our results suggest that GMF plays an important role in adult hippocampal neurogenesis through maintaining appropriate endogenous ROS levels.

Environment permissible concentrations of glyphosate in drinking water can influence the fate of neural stem cells from the subventricular zone of the postnatal mouse

The developing nervous system is highly vulnerable to environmental toxicants especially pesticides. Glyphosate pesticide induces neurotoxicity both in humans and rodents, but so far only when exposed to higher concentrations. A few studies, however, have also reported the risk of general toxicity of glyphosate at concentrations comparable to allowable limits set up by environmental protection authorities. In vitro data regarding glyphosate neurotoxicity at concentrations comparable to maximum permissible concentrations in drinking water is lacking. In the present study, we established an in vitro assay based upon neural stem cells (NSCs) from the subventricular zone of the postnatal mouse to decipher the effects of two maximum permissible concentrations of glyphosate in drinking water on the basic neurogenesis processes. Our results demonstrated that maximum permissible concentrations of glyphosate recognized by environmental protection authorities significantly reduced the cell migration and differentiation of NSCs as demonstrated by the downregulation of the expression levels of the neuronal ß-tubulin III and the astrocytic S100B genes. The expression of the cytoprotective gene CYP1A1 was downregulated whilst the expression of oxidative stresses indicator gene SOD1 was upregulated. The concentration comparable to non-toxic human plasma concentration significantly induced cytotoxicity and activated Ca2+ signalling in the differentiated culture. Our findings demonstrated that the permissible concentrations of glyphosate in drinking water recognized by environmental protection authorities are capable of inducing neurotoxicity in the developing nervous system.

A Set of Cell Lines Derived from a Genetic Murine Glioblastoma Model Recapitulates Molecular and Morphological Characteristics of Human Tumors

Simple Summary

Glioblastoma (GBM) is a highly aggressive and almost inevitably lethal brain tumor. Animal models for GBM are crucial to study how the tumor evolves in vivo and to test novel treatment options. Most currently available models are based on the transplantation of human GBM cells into mice with a defective immune system. However, this approach does not allow to study the contribution of immune cells to GBM growth and to test immunotherapies. Transplantation of murine GBM cells overcomes this limitation, however, up to now, only a limited number, which mostly do not mimic important characteristics of human GBM, have been available. Via in vivo passaging, we established a set of murine GBM cell lines that (i) can be easily cultivated and further genetically manipulated, (ii) upon transplantation develop tumors with phenotypic and pathological features of human GBM, and (iii) are available to be shared with the scientific community.

Abstract

Glioblastomas (GBM) are the most aggressive tumors affecting the central nervous system in adults, causing death within, on average, 15 months after diagnosis. Immunocompetent in-vivo models that closely mirror human GBM are urgently needed for deciphering glioma biology and for the development of effective treatment options. The murine GBM cell lines currently available for engraftment in immunocompetent mice are not only exiguous but also inadequate in representing prominent characteristics of human GBM such as infiltrative behavior, necrotic areas, and pronounced tumor heterogeneity. Therefore, we generated a set of glioblastoma cell lines by repeated in vivo passaging of cells isolated from a neural stem cell-specific Pten/p53 double-knockout genetic mouse brain tumor model. Transcriptome and genome analyses of the cell lines revealed molecular heterogeneity comparable to that observed in human glioblastoma. Upon orthotopic transplantation into syngeneic hosts, they formed high-grade gliomas that faithfully recapitulated the histopathological features, invasiveness and immune cell infiltration characteristic of human glioblastoma. These features make our cell lines unique and useful tools to study multiple aspects of glioblastoma pathomechanism and to test novel treatments in an intact immune microenvironment.

WDR81 regulates adult hippocampal neurogenesis through endosomal SARA-TGFβ signaling

Adult hippocampal neurogenesis, a process considered important for hippocampal function, is regulated at multiple molecular levels. Mutations in the gene encoding the WD40 repeat-containing protein WDR81 are associated with neurological disorders, including cerebellar ataxia, mental retardation, quadrupedal locomotion syndrome (CAMRQ2), and microcephaly. In this study, we show that ablation of WDR81 in adult neural progenitor cells (aNPCs) markedly reduced adult hippocampal neurogenesis and impaired hippocampus-dependent learning. WDR81 suppresses endosomal PtdIns3P synthesis, likely by inhibiting the assembly of the PI3K-III complex. In the absence of WDR81, endosomal PtdIns3P levels are greatly elevated, leading to endosomal persistence of the PtdIns3P-binding protein SARA and consequently hyperactivation of SARA-dependent TGFβ signaling. Inhibition of PI3K-III activity or suppression of SARA-dependent TGFβ signaling markedly ameliorated the defective adult neurogenesis in WDR81-deficient mice. Taken together, these findings not only uncover the requirement for the WDR81-SARA-TGFβ axis in adult hippocampal neurogenesis, but also suggest that defective adult hippocampal neurogenesis contributes to the etiology of WDR81-related neurological diseases.