Notch signaling as a master regulator of adult neurogenesis

The Nerve-Induced Adipose Stem Cells Promote Nerve Repair in Stress Urinary Incontinence by Regulating Schwann Cell Repair Phenotype Conversion Through Activation of the Notch Pathway

Stress urinary incontinence (SUI) currently lacks effective treatment options, and the restoration of neurological function remains a major challenge, with unmet clinical needs. Research has indicated that adipose-derived stem cells (ADSCs) can be induced to differentiate into neural-induced adipose-derived stem cells (NI-ADSCs) under specific inductive conditions, exhibiting excellent neuroregenerative capabilities. ADSCs were obtained from female SD rats and induced into NI-ADSCs. In vitro, NI-ADSCs were co-cultured with Schwann cells (SCs) to investigate their effects on SC proliferation and repair phenotype transition and further explore its underlying mechanism. In vivo, a rat model of SUI was established using a bilateral pudendal nerve transection method. NI-ADSCs were injected into the urethral sphincter to evaluate their effects on urodynamics, muscle angiogenesis, and neural repair in SUI rats, while also exploring the mechanisms of neural repair. This study used EGF, FGF, and B27 to induce ADSCs into NI-ADSCs expressing neural induction markers (MAP, Nestin, and PAX6). In vitro experiments found no significant difference in the proliferation of L6 and RSC96 between NI-ADSCs and ADSCs (p > 0.05). However, when co-cultured with NI-ADSCs, SCs showed upregulated expression of repair-related phenotypic markers (BDNF, GDNF, and GFAP). In this phenotypic transformation process, the expression of Notch-related pathway proteins (Notch1, NICD, and Hes1) was increased, and the use of DAPT (a Notch pathway inhibitor) could suppress the SC repair phenotype transformation. In vivo, experiments revealed that intraurethral injection of NI-ADSCs significantly promoted the expression of neural marker (S100β) and demyelination markers (GFAP) and urodynamic recovery in SUI rats, while DAPT inhibited its neural repair effect. In summary, our study demonstrates that NI-ADSCs can promote nerve regeneration by promoting and maintaining the repair-related phenotype of SCs. The underlying mechanism may be related to the activation of the Notch signaling pathway.

Life History-Dependent Brain Transcriptomic Signatures in Nothobranchids: Insights into Aging, Neurogenesis, and Life History Evolution

The African turquoise killifish Nothobranchius furzeri is a powerful model organism in aging research. Within the family Nothobranchiidae, a wide range of lifespan is observed in annual, semi-annual, and non-annual life histories. In this study, we examined the brain transcriptomic signatures of adult nothobranchids across life history variations. Our results show that the brain gene expression profiles exhibit strong life history signatures compared to the liver tissue. Semi-annual Fundulopanchax species shows upregulation in cell division and mitosis compared to non-annual Aphyosemion species. We identified genes related to neurogenesis such as DNMT3A, SOX2, and FGF10 that show downregulation in the short-lived annual species compared to other life histories. The Notch signaling pathway is enriched in the non-annual species suggesting the importance of this pathway in longer-lived killifish. Our study demonstrates that other non-model nothobranchids can be used as comparative species to N .  furzeri in the study of aging, neurogenesis, and life history.

Epigenetic and genetic profiling of comorbidity patterns among substance dependence diagnoses

This study investigated the genetic and epigenetic mechanisms underlying the comorbidity of five substance dependence diagnoses (SDs; alcohol, AD; cannabis, CaD; cocaine, CoD; opioid, OD; tobacco, TD). A latent class analysis (LCA) was performed on 22,668 individuals from six cohorts to identify comorbid DSM-IV SD patterns. In subsets of this sample, we tested SD-latent classes with respect to polygenic overlap of psychiatric and psychosocial traits in 7659 individuals of European descent and epigenome-wide changes in 886 individuals of African, European, and Admixed-American descents. The LCA identified four latent classes related to SD comorbidities: AD + TD, CoD + TD, AD + CoD + OD + TD (i.e., polysubstance addiction, PSU), and TD. In the epigenome-wide association analysis, SPATA4 cg02833127 was associated with CoD + TD, AD + TD, and PSU latent classes. AD + TD latent class was also associated with CpG sites located on ARID1B, NOTCH1, SERTAD4, and SIN3B, while additional epigenome-wide significant associations with CoD + TD latent class were observed in ANO6 and MOV10 genes. PSU-latent class was also associated with a differentially methylated region in LDB1. We also observed shared polygenic score (PGS) associations for PSU, AD + TD, and CoD + TD latent classes (i.e., attention-deficit hyperactivity disorder, anxiety, educational attainment, and schizophrenia PGS). In contrast, TD-latent class was exclusively associated with posttraumatic stress disorder-PGS. Other specific associations were observed for PSU-latent class (subjective wellbeing-PGS and neuroticism-PGS) and AD + TD-latent class (bipolar disorder-PGS). In conclusion, we identified shared and unique genetic and epigenetic mechanisms underlying SD comorbidity patterns. These findings highlight the importance of modeling the co-occurrence of SD diagnoses when investigating the molecular basis of addiction-related traits.

Identifying reproducible transcription regulator coexpression patterns with single cell transcriptomics

The proliferation of single cell transcriptomics has potentiated our ability to unveil patterns that reflect dynamic cellular processes such as the regulation of gene transcription. In this study, we leverage a broad collection of single cell RNA-seq data to identify the gene partners whose expression is most coordinated with each human and mouse transcription regulator (TR). We assembled 120 human and 103 mouse scRNA-seq datasets from the literature (>28 million cells), constructing a single cell coexpression network for each. We aimed to understand the consistency of TR coexpression profiles across a broad sampling of biological contexts, rather than examine the preservation of context-specific signals. Our workflow therefore explicitly prioritizes the patterns that are most reproducible across cell types. Towards this goal, we characterize the similarity of each TR's coexpression within and across species. We create single cell coexpression rankings for each TR, demonstrating that this aggregated information recovers literature curated targets on par with ChIP-seq data. We then combine the coexpression and ChIP-seq information to identify candidate regulatory interactions supported across methods and species. Finally, we highlight interactions for the important neural TR ASCL1 to demonstrate how our compiled information can be adopted for community use.

Quantitative phosphoproteomics reveals that nestin is a downstream target of dual leucine zipper kinase during retinoic acid-induced neuronal differentiation of Neuro-2a cells

BACKGROUND

Dual leucine zipper kinase (DLK) is critical for neurite outgrowth in the developing nervous system and during nerve regeneration, but the underlying mechanisms remain largely unknown. To address this issue, we generated stable shRNA-mediated DLK-depleted Neuro-2a cell lines and analyzed their phosphoproteome after induction of neuronal differentiation by retinoic acid (RA).

RESULTS

Here, we report the identification of 32 phosphopeptides that exhibited significant differences in relative abundance between control and DLK-depleted cells. Two of the most downregulated phosphopeptides identified after DLK depletion were derived from nestin, a type VI intermediate filament (IF) protein typically expressed in neural progenitor cells. The reduced abundance of these phosphopeptides in response to DLK knockdown was validated using parallel reaction monitoring (PRM)-based quantitative proteomics and paired with a concomitant reduction in nestin mRNA and protein expression, indicating that the decrease in nestin phosphorylation was due to a decrease in total nestin in DLK-depleted cells compared to control cells. This DLK-mediated regulation of nestin expression had no apparent effect on neurite formation because nestin knockdown alone was not sufficient to impair RA-induced neurite extension in parental Neuro-2a cells, and nestin overexpression failed to rescue the neurite outgrowth defect observed in DLK-depleted Neuro-2a cells.

CONCLUSIONS

Together, these results demonstrate that nestin is a novel downstream target of DLK signaling but not a mediator of its ability to promote neurite outgrowth during neuronal differentiation.

Developing zebrafish models of Notch-related CNS pathologies

Notch signaling is an evolutionarily conserved cellular pathway that regulates various stem cell functions, including fate determination, differentiation, proliferation, and apoptosis. This crucial signaling mechanism also plays an important role in the brain, regulating neurogenesis, cell differentiation, and homeostasis, whereas disrupted Notch signaling is linked to various neurodegenerative diseases and brain cancers. Here, we review the central nervous system (CNS) pathologies associated with aberrant Notch signaling, and summarize the available experimental (animal) models used to study these pathologies, with a special focus on zebrafish (Danio rerio). As genetic, pharmacological, and behavioral models in zebrafish have significantly advanced our understanding of Notch-related CNS disorders, future research is expected to further link Notch signaling to brain disorders and, eventually, lead to their more specific and targeted therapeuties.

Impaired olfactory bulb neurogenesis mediated by Notch1 contributes to olfactory dysfunction in mice chronically exposed to methamphetamine

Methamphetamine (Meth) is a potent central nervous system stimulant with high addictive potential and neurotoxic effects. Chronic use results in significant damage in various brain functions, including cognition, memory, and sensory perception. Olfactory dysfunction is a notable yet often overlooked consequence of Meth abuse, and its underlying mechanisms are not fully understood. This study investigates the mechanisms of Meth-induced olfactory impairment through a thorough examination of olfactory bulb (OB) neurogenesis. We found that chronic Meth abuse impaired olfactory function in mice by not only reducing the self-renewal of subventricular zone (SVZ) neural stem cells (NSCs) but also altering their differentiation potential, leading their differentiation into astrocytes at the expense of neurons. Mechanistically, Meth inhibits autophagosome-lysosome fusion by downregulating Syntaxin 17 (Stx17), which reduces autophagic flux. In NSCs, autophagy tightly regulates Notch1 levels, and impaired autophagic degradation of Notch1 leads to its abnormal activation. This alters NSCs fate determination, ultimately affecting OB neurogenesis. Our study reveals that Meth impairs olfactory function through autophagic dysfunction and aberrant Notch1 signaling. Understanding these mechanisms not only provides new insights into Meth-induced olfactory dysfunction but also offers potential targets for developing therapies to alleviate Meth-induced neurotoxicity and sensory damage in the future.

Identifying Reproducible Transcription Regulator Coexpression Patterns with Single Cell Transcriptomics

The proliferation of single cell transcriptomics has potentiated our ability to unveil patterns that reflect dynamic cellular processes such as the regulation of gene transcription. In this study, we leverage a broad collection of single cell RNA-seq data to identify the gene partners whose expression is most coordinated with each human and mouse transcription regulator (TR). We assembled 120 human and 103 mouse scRNA-seq datasets from the literature (>28 million cells), constructing a single cell coexpression network for each. We aimed to understand the consistency of TR coexpression profiles across a broad sampling of biological contexts, rather than examine the preservation of context-specific signals. Our workflow therefore explicitly prioritizes the patterns that are most reproducible across cell types. Towards this goal, we characterize the similarity of each TR's coexpression within and across species. We create single cell coexpression rankings for each TR, demonstrating that this aggregated information recovers literature curated targets on par with ChIP-seq data. We then combine the coexpression and ChIP-seq information to identify candidate regulatory interactions supported across methods and species. Finally, we highlight interactions for the important neural TR ASCL1 to demonstrate how our compiled information can be adopted for community use.

Regulation of the microglial polarization for alleviating neuroinflammation in the pathogenesis and therapeutics of major depressive disorder

Major depressive disorder (MDD), as a multimodal neuropsychiatric and neurodegenerative illness with high prevalence and disability rates, has become a burden to world health and the economy that affects millions of individuals worldwide. Neuroinflammation, an atypical immune response occurring in the brain, is currently gaining more attention due to its association with MDD. Microglia, as immune sentinels, have a vital function in regulating neuroinflammatory reactions in the immune system of the central nervous system. From the perspective of steady-state branching states, they can transition phenotypes between two extremes, namely, M1 and M2 phenotypes are pro-inflammatory and anti-inflammatory, respectively. It has an intermediate transition state characterized by different transcriptional features and the release of inflammatory mediators. The timing regulation of inflammatory cytokine release is crucial for damage control and guiding microglia back to a steady state. The dysregulation can lead to exorbitant tissue injury and neuronal mortality, and targeting the cellular signaling pathway that serves as the regulatory basis for microglia is considered an essential pathway for treating MDD. However, the specific intervention targets and mechanisms of microglial activation pathways in neuroinflammation are still unclear. Therefore, the present review summarized and discussed various signaling pathways and effective intervention targets that trigger the activation of microglia from its branching state and emphasizes the mechanism of microglia-mediated neuroinflammation associated with MDD.

Müller glia in short-term dark adaptation of the Austrolebias charrua retina: Cell proliferation and cytoarchitecture

Fish with unique life cycles offer valuable insights into retinal plasticity, revealing mechanisms of environmental adaptation, cell proliferation, and thus, potentially regeneration. The variability of the environmental factors to which Austrolebias annual fishes are exposed has acted as a strong selective pressure shaping traits such as nervous system plasticity. This has contributed to adaptation to their extreme conditions including the decreased luminosity as ponds dry out. In particular, the retina of A. charrua has been shown to respond to 30 days of decreased luminosity by exacerbating cell proliferation Now, we aimed to determine the cellular component of the retina involved in shorter-term responses. To this end, we performed 5-bromo-2'-deoxyuridine (BrdU) experiments, exposing adult fish to a short period (11 days) of constant darkness. Strikingly, in control conditions, neurogenesis in the inner nuclear and ganglion cell layer in the differentiated retina was detected. In constant darkness, we observed an effect on inner nuclear layer cell proliferation and changes in retinal cytoarchitecture of the retina with cell clusters located in the inner plexiform layer. Additionally, increased BLBP (brain lipid-binding protein) presence was detected in darkness, which has been previously associated with immature and reactivated Müller glia. Thus, our results suggest that the A. charrua retina can respond to environmental changes via rapid activation of progenitor cells in the INL, namely the Müller glia This leads us to hypothesize, that cell proliferation and neurogenesis might contribute to the responses to the functional needs of organisms, potentially playing an adaptive role.

Neural differentiation in perspective: mitochondria as early programmers

Neural differentiation during development of the nervous system has been extensively studied for decades. These efforts have culminated in the generation of a detailed map of developmental events that appear to be associated with emergence of committed cells in the nervous system. In this review the landscape of neural differentiation is revisited by focusing on abiotic signals that play a role in induction of neural differentiation. Evidence is presented regarding a chimeric landscape whereby abiotic signals generated by mitochondria orchestrate early events during neural differentiation. This early stage, characterised by mitochondrial hyperactivity, in turn triggers a late stage of differentiation by reprogramming the activity of biotic signals.

Aberrant neurodevelopment in human iPS cell-derived models of Alexander disease

Alexander disease (AxD) is a rare and severe neurodegenerative disorder caused by mutations in glial fibrillary acidic protein (GFAP). While the exact disease mechanism remains unknown, previous studies suggest that mutant GFAP influences many cellular processes, including cytoskeleton stability, mechanosensing, metabolism, and proteasome function. While most studies have primarily focused on GFAP-expressing astrocytes, GFAP is also expressed by radial glia and neural progenitor cells, prompting questions about the impact of GFAP mutations on central nervous system (CNS) development. In this study, we observed impaired differentiation of astrocytes and neurons in co-cultures of astrocytes and neurons, as well as in neural organoids, both generated from AxD patient-derived induced pluripotent stem (iPS) cells with a GFAPR239C mutation. Leveraging single-cell RNA sequencing (scRNA-seq), we identified distinct cell populations and transcriptomic differences between the mutant GFAP cultures and a corrected isogenic control. These findings were supported by results obtained with immunocytochemistry and proteomics. In co-cultures, the GFAPR239C mutation resulted in an increased abundance of immature cells, while in unguided neural organoids and cortical organoids, we observed altered lineage commitment and reduced abundance of astrocytes. Gene expression analysis revealed increased stress susceptibility, cytoskeletal abnormalities, and altered extracellular matrix and cell-cell communication patterns in the AxD cultures, which also exhibited higher cell death after stress. Overall, our results point to altered cell differentiation in AxD patient-derived iPS-cell models, opening new avenues for AxD research.

Transcription factor networks in cellular quiescence

Many of the cells in mammalian tissues are in a reversible quiescent state; they are not dividing, but retain the ability to proliferate in response to extracellular signals. Quiescence relies on the activities of transcription factors (TFs) that orchestrate the repression of genes that promote proliferation and establish a quiescence-specific gene expression program. Here we discuss how the coordinated activities of TFs in different quiescent stem cells and differentiated cells maintain reversible cell cycle arrest and establish cell-protective signalling pathways. We further cover the emerging mechanisms governing the dysregulation of quiescence TF networks with age. We explore how recent developments in single-cell technologies have enhanced our understanding of quiescence heterogeneity and gene regulatory networks. We further discuss how TFs and their activities are themselves regulated at the RNA, protein and chromatin levels. Finally, we summarize the challenges associated with defining TF networks in quiescent cells.

Pleiotropic Associations with Alzheimer's Disease and Physical Activity: Sex Differences and the Effects of Environment

Physical activity (PA) is a modifiable factor in mitigating/preventing Alzheimer's disease (AD). It is crucial to identify the conditions under which PA's effects on AD risk would be beneficial. This study aims to gain insights into pleiotropic predisposition to AD and PA within and across sexes and environmental effects. We performed a genome-wide association study (GWAS) of pleiotropic AD-PA associations in individuals (65 years and older) of European ancestry in a US sample (14,628 individuals), for men and women separately and combined, and contrasted them with the UK biobank (204,789 individuals) to elucidate the effects of the environment. Fisher's method and Wald's test were used for estimating the significance of pleiotropic associations and differences between the samples. We identified genetic markers in 60 loci with significant pleiotropic associations. Of them, 91.7% of loci exhibited antagonistic relationships characterized by a misalignment of the signs of the associations of the same alleles with AD and PA and a correlation between these phenotypes. Only 16.7% of associations were replicated in the UKB. Phosphorylation and the regulation of transcription were identified as more pronounced biological mechanisms of AD-PA pleiotropy in females and males, respectively. Our results demonstrate the intrinsic heterogeneity of AD-PA pleiotropy and suggest that PA should be used as an intervention against AD with caution, after identifying groups of individuals and combinations of gene-environment interactions with beneficial effects.

Non-apoptotic caspase events and Atf3 expression underlie direct neuronal differentiation of adult neural stem cells

Neural stem cells (NSCs) generate neurons over a lifetime in adult vertebrate brains. In the adult zebrafish pallium, NSCs persist long term through balanced fate decisions. These decisions include direct neuronal conversions, i.e. delamination and neurogenesis without a division. To characterize this process, we reanalyze intravital imaging data of adult pallial NSCs, and observe shared delamination dynamics between NSCs and committed neuronal progenitors. Searching for mechanisms predicting direct NSC conversions, we build an NSC-specific genetic tracer of Caspase3/7 activation (Cas3*/Cas7*) in vivo. We show that non-apoptotic Cas3*/7* events occur in adult NSCs and are biased towards lineage termination under physiological conditions, with a predominant generation of single neurons. We further identify the transcription factor Atf3 as necessary for this bias. Finally, we show that the Cas3*/7* pathway is engaged by NSCs upon parenchymal lesion and correlates with NSCs more prone to lineage termination and neuron formation. These results provide evidence for non-apoptotic caspase events occurring in vertebrate adult NSCs and link these events with the NSC fate decision of direct conversion, which is important for long-term NSC population homeostasis.

C11orf58 (Hero20) Gene Polymorphism: Contribution to Ischemic Stroke Risk and Interactions with Other Heat-Resistant Obscure Chaperones

Background: Recently identified Hero proteins, which possess chaperone-like functions, are promising candidates for research into atherosclerosis-related diseases, including ischemic stroke (IS). Methods: 2204 Russian subjects (917 IS patients and 1287 controls) were genotyped for fifteen common SNPs in Hero20 gene C11orf58 using probe-based PCR and the MassArray-4 system. Results: Six C11orf58 SNPs were significantly associated with an increased risk of IS in the overall group (OG) and significantly modified by smoking (SMK) and low fruit/vegetable intake (LFVI): rs10766342 (effect allele (EA) A; P(OG = 0.02; SMK = 0.009; LFVI = 0.04)), rs11024032 (EA T; P(OG = 0.01; SMK = 0.01; LFVI = 0.036)), rs11826990 (EA G; P(OG = 0.007; SMK = 0.004; LFVI = 0.03)), rs3203295 (EA C; P(OG = 0.016; SMK = 0.01; LFVI = 0.04)), rs10832676 (EA G; P(OG = 0.006; SMK = 0.002; LFVI = 0.01)), rs4757429 (EA T; P(OG = 0.02; SMK = 0.04; LFVI = 0.04)). The top ten intergenic interactions of Hero genes (two-, three-, and four-locus models) involved exclusively polymorphic loci of C11orf58 and C19orf53 and were characterized by synergic and additive (independent) effects between SNPs. Conclusions: Thus, C11orf58 gene polymorphism represents a major risk factor for IS. Bioinformatic analysis showed the involvement of C11orf58 SNPs in molecular mechanisms of IS mediated by their role in the regulation of redox homeostasis, inflammation, vascular remodeling, apoptosis, vasculogenesis, neurogenesis, lipid metabolism, proteostasis, hypoxia, cell signaling, and stress response. In terms of intergenic interactions, C11orf58 interacts most closely with C19orf53.

Generating neurons in the embryonic and adult brain: compared principles and mechanisms

Neurogenesis is a lifelong process, generating neurons in the right amount, time and place and with the correct identity to permit the growth, function, plasticity and repair of the nervous system, notably the brain. Neurogenesis originates from neural progenitor cells (NPs), endowed with the capacity to divide, renew to maintain the progenitor population, or commit to engage in the neurogenesis process. In the adult brain, these progenitors are classically called neural stem cells (NSCs). We review here the commonalities and differences between NPs and NSCs, in their cellular and molecular attributes but also in their potential, regulators and lineage, in the embryonic and adult brains. Our comparison is based on the two most studied model systems, namely the telencephalon of the zebrafish and mouse. We also discuss how the population of embryonic NPs gives rise to adult NSCs, and outstanding questions pertaining to this transition.

Epigenetic and Genetic Profiling of Comorbidity Patterns among Substance Dependence Diagnoses

Objective

This study investigated the genetic and epigenetic mechanisms underlying the comorbidity patterns of five substance dependence diagnoses (SDs; alcohol, AD; cannabis, CaD; cocaine, CoD; opioid, OD; tobacco, TD).

Methods

A latent class analysis (LCA) was performed on 31,197 individuals (average age 42±11 years; 49% females) from six cohorts to identify comorbid DSM-IV SD patterns. In subsets of this sample, we tested SD-latent classes with respect to polygenic burden of psychiatric and behavioral traits and epigenome-wide changes in three population groups.

Results

An LCA identified four latent classes related to SD comorbidities: AD+TD, CoD+TD, AD+CoD+OD+TD (i.e., polysubstance use, PSU), and TD. In the epigenome-wide association analysis, SPATA4 cg02833127 was associated with CoD+TD, AD+TD, and PSU latent classes. AD+TD latent class was also associated with CpG sites located on ARID1B , NOTCH1 , SERTAD4, and SIN3B , while additional epigenome-wide significant associations with CoD+TD latent class were observed in ANO6 and MOV10 genes. PSU-latent class was also associated with a differentially methylated region in LDB1 . We also observed shared polygenic score (PGS) associations for PSU, AD+TD, and CoD+TD latent classes (i.e., attention-deficit hyperactivity disorder, anxiety, educational attainment, and schizophrenia PGS). In contrast, TD-latent class was exclusively associated with posttraumatic stress disorder-PGS. Other specific associations were observed for PSU-latent class (subjective wellbeing-PGS and neuroticism-PGS) and AD+TD-latent class (bipolar disorder-PGS).

Conclusions

We identified shared and unique genetic and epigenetic mechanisms underlying SD comorbidity patterns. These findings highlight the importance of modeling the co-occurrence of SD diagnoses when investigating the molecular basis of addiction-related traits.

Role of O-GlcNAcylation in Central Nervous System Development and Injuries: A Systematic Review

The development of central nervous system (CNS) can form perceptual, memory, and cognitive functions, while injuries to CNS often lead to severe neurological dysfunction and even death. As one of the prevalent post-translational modifications (PTMs), O-GlcNAcylation has recently attracted great attentions due to its functions in regulating the activity, subcellular localization, and stability of target proteins. It has been indicated that O-GlcNAcylation could interact with phosphorylation, ubiquitination, and methylation to jointly regulate the function and activity of proteins. Furthermore, a growing number of studies have suggested that O-GlcNAcylation played an important role in the CNS. During development, O-GlcNAcylation participated in the neurogenesis, neuronal development, and neuronal function. In addition, O-GlcNAcylation was involved in the progress of CNS injuries including ischemic stroke, subarachnoid hemorrhage (SAH), and intracerebral hemorrhage (ICH) and played a crucial role in the improvement of brain damage such as attenuating cognitive impairment, inhibiting neuroinflammation, suppressing endoplasmic reticulum (ER) stress, and maintaining blood-brain barrier (BBB) integrity. Therefore, O-GlcNAcylation showed great promise as a potential target in CNS development and injuries. In this article, we presented a review highlighting the role of O-GlcNAcylation in CNS development and injuries. Hence, on the basis of these properties and effects, intervention with O-GlcNAcylation may be developed as therapeutic agents for CNS diseases.

Rbm24/Notch1 signaling regulates adult neurogenesis in the subventricular zone and mediates Parkinson-associated olfactory dysfunction

Rationale: Adult neurogenesis in the subventricular zone (SVZ) is essential for maintaining neural homeostasis, and its dysregulation contributes to anosmia and delayed tissue healing in neurological disorders, such as Parkinson's disease (PD). Despite intricate regulatory networks identified in SVZ neurogenesis, the molecular mechanisms dynamically maintaining neural stem/progenitor cells (NSPCs) in response to physiological and pathological stimuli remain incompletely elucidated. Methods: We generated an RNA binding motif protein 24 (Rbm24) knockout model to investigate its impact on adult neurogenesis in the SVZ, employing immunofluorescence, immunoblot, electrophysiology, RNA-sequencing, and in vitro experiments. Further investigations utilized a PD mouse model, along with genetic and pharmacological manipulations, to elucidate Rbm24 involvement in PD pathology. Results: Rbm24, a multifaceted post-transcriptional regulator of cellular homeostasis, exhibited broad expression in the SVZ from development to aging. Deletion of Rbm24 significantly impaired NSPC proliferation in the adult SVZ, ultimately resulting in collapsed neurogenesis in the olfactory bulb. Notably, Rbm24 played a specific role in maintaining Notch1 mRNA stability in adult NSPCs. The Rbm24/Notch1 signaling axis was significantly downregulated in the SVZ of PD mice. Remarkably, overexpression of Rbm24 rescued disruption of adult neurogenesis and olfactory dysfunction in PD mice, and these effects were hindered by DAPT, a potent inhibitor of Notch1. Conclusions: Our findings highlight the critical role of the Rbm24/Notch1 signaling axis in regulating adult SVZ neurogenesis under physiological and pathological circumstances. This provides valuable insights into the dynamic regulation of NSPC homeostasis and offers a potential targeted intervention for PD and related neurological disorders.

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

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

Cerebellar granular neuron progenitors exit their germinative niche via BarH-like1 activity mediated partly by inhibition of T-cell factor

Cerebellar granule neuron progenitors (GNPs) originate from the upper rhombic lip (URL), a germinative niche in which developmental defects produce human diseases. T-cell factor (TCF) responsiveness and Notch dependence are hallmarks of self-renewal in neural stem cells. TCF activity, together with transcripts encoding proneural gene repressors hairy and enhancer of split (Hes/Hey), are detected in the URL; however, their functions and regulatory modes are undeciphered. Here, we established amphibian as a pertinent model for studying vertebrate URL development. The amphibian long-lived URL is TCF active, whereas the external granular layer (EGL) is non-proliferative and expresses hes4 and hes5 genes. Using functional and transcriptomic approaches, we show that TCF activity is necessary for URL emergence and maintenance. We establish that the transcription factor Barhl1 controls GNP exit from the URL, acting partly through direct TCF inhibition. Identification of Barhl1 target genes suggests that, besides TCF, Barhl1 inhibits transcription of hes5 genes independently of Notch signaling. Observations in amniotes suggest a conserved role for Barhl in maintenance of the URL and/or EGL via co-regulation of TCF, Hes and Hey genes.

The dynamics of Notch signaling in the neuron-glia switch: a balancing act

A recent study by Tran et al. (Tran LN, Loew SK, Franco SJ. J Neurosci 43: 6854-6871, 2023) investigated the cellular processes underlying the timing and regulation of oligodendrocyte production, focusing on the role of Notch signaling in the dorsal forebrain of mouse embryos. They found that although Notch signaling is required to specify oligodendrocyte precursor cell fate during embryonic development, overexpression prevents oligodendrogenesis through several mechanisms. This critical review highlights their findings and offers suggestions for future research investigating the precise spatiotemporal control of Notch signaling throughout the development of the central nervous system.

SNP and Structural Study of the Notch Superfamily Provides Insights and Novel Pharmacological Targets against the CADASIL Syndrome and Neurodegenerative Diseases

The evolutionary conserved Notch signaling pathway functions as a mediator of direct cell-cell communication between neighboring cells during development. Notch plays a crucial role in various fundamental biological processes in a wide range of tissues. Accordingly, the aberrant signaling of this pathway underlies multiple genetic pathologies such as developmental syndromes, congenital disorders, neurodegenerative diseases, and cancer. Over the last two decades, significant data have shown that the Notch signaling pathway displays a significant function in the mature brains of vertebrates and invertebrates beyond neuronal development and specification during embryonic development. Neuronal connection, synaptic plasticity, learning, and memory appear to be regulated by this pathway. Specific mutations in human Notch family proteins have been linked to several neurodegenerative diseases including Alzheimer's disease, CADASIL, and ischemic injury. Neurodegenerative diseases are incurable disorders of the central nervous system that cause the progressive degeneration and/or death of brain nerve cells, affecting both mental function and movement (ataxia). There is currently a lot of study being conducted to better understand the molecular mechanisms by which Notch plays an essential role in the mature brain. In this study, an in silico analysis of polymorphisms and mutations in human Notch family members that lead to neurodegenerative diseases was performed in order to investigate the correlations among Notch family proteins and neurodegenerative diseases. Particular emphasis was placed on the study of mutations in the Notch3 protein and the structure analysis of the mutant Notch3 protein that leads to the manifestation of the CADASIL syndrome in order to spot possible conserved mutations and interpret the effect of these mutations in the Notch3 protein structure. Conserved mutations of cysteine residues may be candidate pharmacological targets for the potential therapy of CADASIL syndrome.

Hypoxia preconditioning increases Notch1 activity by regulating DNA methylation in vitro and in vivo

BACKGROUND

Our previous research has demonstrated that hypoxic preconditioning (HPC) can improve spatial learning and memory abilities in adult mice. Adult hippocampal neurogenesis has been associated with learning and memory. The Neurogenic locus notch homolog protein (Notch) was involved in adult hippocampal neurogenesis, as well as in learning and memory. It is currently unclear whether the Notch pathway regulates hippocampal neuroregeneration by modifying the DNA methylation status of the Notch gene following HPC.

METHOD

The HPC animal model and cell model were established through repeated hypoxia exposure using mice and the mouse hippocampal neuronal cell line HT22. Step-down test was conducted on HPC mice. Real-time PCR and Western blot analysis were used to assess the mRNA and protein expression levels of Notch1 and hairy and enhancer of split1 (HES1). The presence of BrdU-positive cells and Notch1 expression in the hippocampal dental gyrus (DG) were examined with confocal microscopy. The methylation status of the Notch1 was analyzed using methylation-specific PCR (MS-PCR). HT22 cells were employed to elucidate the impact of HPC on Notch1 in vitro.

RESULTS

HPC significantly improved the step-down test performance of mice with elevated levels of mRNA and protein expression of Notch1 and HES1 (P < 0.05). The intensities of the Notch1 signal in the control group, the H group and the HPC group were 2.62 ± 0.57 × 107, 2.87 ± 0.84 × 107, and 3.32 ± 0.14 × 107, respectively, and the number of BrdU (+) cells in the hippocampal DG were 1.83 ± 0.54, 3.71 ± 0.64, and 7.29 ± 0.68 respectively. Compared with that in C and H group, the intensity of the Notch1 signal and the number of BrdU (+) cells increased significantly in HPC group (P < 0.05). The methylation levels of the Notch1 promoter 0.82 ± 0.03, 0.65 ± 0.03, and 0.60 ± 0.02 in the C, H, and HPC groups, respectively. The methylation levels of Notch1 decreased significantly (P < 0.05). The effect of HPC on HT22 cells exhibited similarities to that observed in the hippocampus.

CONCLUSION

HPC may confer neuroprotection by activating the Notch1 signaling pathway and regulating its methylation level, resulting in the regeneration of hippocampal neurons.

Adult Neurogenesis of Teleost Fish Determines High Neuronal Plasticity and Regeneration

Studying the properties of neural stem progenitor cells (NSPCs) in a fish model will provide new information about the organization of neurogenic niches containing embryonic and adult neural stem cells, reflecting their development, origin cell lines and proliferative dynamics. Currently, the molecular signatures of these populations in homeostasis and repair in the vertebrate forebrain are being intensively studied. Outside the telencephalon, the regenerative plasticity of NSPCs and their biological significance have not yet been practically studied. The impressive capacity of juvenile salmon to regenerate brain suggests that most NSPCs are likely multipotent, as they are capable of replacing virtually all cell lineages lost during injury, including neuroepithelial cells, radial glia, oligodendrocytes, and neurons. However, the unique regenerative profile of individual cell phenotypes in the diverse niches of brain stem cells remains unclear. Various types of neuronal precursors, as previously shown, are contained in sufficient numbers in different parts of the brain in juvenile Pacific salmon. This review article aims to provide an update on NSPCs in the brain of common models of zebrafish and other fish species, including Pacific salmon, and the involvement of these cells in homeostatic brain growth as well as reparative processes during the postraumatic period. Additionally, new data are presented on the participation of astrocytic glia in the functioning of neural circuits and animal behavior. Thus, from a molecular aspect, zebrafish radial glia cells are seen to be similar to mammalian astrocytes, and can therefore also be referred to as astroglia. However, a question exists as to if zebrafish astroglia cells interact functionally with neurons, in a similar way to their mammalian counterparts. Future studies of this fish will complement those on rodents and provide important information about the cellular and physiological processes underlying astroglial function that modulate neural activity and behavior in animals.

Harnessing the Stem Cell Niche in Regenerative Medicine: Innovative Avenue to Combat Neurodegenerative Diseases

Regenerative medicine harnesses the body's innate capacity for self-repair to restore malfunctioning tissues and organs. Stem cell therapies represent a key regenerative strategy, but to effectively harness their potential necessitates a nuanced understanding of the stem cell niche. This specialized microenvironment regulates critical stem cell behaviors including quiescence, activation, differentiation, and homing. Emerging research reveals that dysfunction within endogenous neural stem cell niches contributes to neurodegenerative pathologies and impedes regeneration. Strategies such as modifying signaling pathways, or epigenetic interventions to restore niche homeostasis and signaling, hold promise for revitalizing neurogenesis and neural repair in diseases like Alzheimer's and Parkinson's. Comparative studies of highly regenerative species provide evolutionary clues into niche-mediated renewal mechanisms. Leveraging endogenous bioelectric cues and crosstalk between gut, brain, and vascular niches further illuminates promising therapeutic opportunities. Emerging techniques like single-cell transcriptomics, organoids, microfluidics, artificial intelligence, in silico modeling, and transdifferentiation will continue to unravel niche complexity. By providing a comprehensive synthesis integrating diverse views on niche components, developmental transitions, and dynamics, this review unveils new layers of complexity integral to niche behavior and function, which unveil novel prospects to modulate niche function and provide revolutionary treatments for neurodegenerative diseases.