HDAC1 and HDAC2 Regulate Intermediate Progenitor Positioning to Safeguard Neocortical Development

HDAC1 is involved in the destabilization of the HSF2 protein under non-stress and stress conditions

Heat shock transcription factors 1 and 2 (HSF1 and HSF2) are the major regulators of the cellular response to stressors, notably to heat shock and to oxidative stress. HSF1 and HSF2 are also important contributors in devasting human pathologies like cancer, neurodegenerative disorders, and neurodevelopmental disorders. Under physiological conditions, nuclear HSF2 is detected in only a few cell types in human adult healthy tissues. In contrast, HSF2 protein levels are elevated at some embryonic stages, but greatly vary among cell types and fluctuates during the cell cycle in diverse cell lines. HSF2 is a short-lived protein whose rapid turnover is controlled by the components of the ubiquitin-proteasome degradation pathway and the stabilization of HSF2 constitutes an important step that regulates its DNA-binding activity and mediates its roles in non-stress, physiological processes. The control of HSF2 abundancy is therefore critical for its regulatory roles in stress responses as well as under physiological conditions. In this regard, the fetal brain cortex is a singular context where HSF2 is strikingly abundant, exhibits constitutive DNA-binding activity and, by controlling a specific repertoire of target genes that play important roles at multiple steps of neurodevelopment. Recently, we showed that the lysine-acetyl-transferases CBP and EP300 stabilize the HSF2 protein under both unstressed and stressed conditions and that the integrity of the CBP/EP300-HSF2 pathway is important for neurodevelopment. Here, we identify the lysine-deacetylase HDAC1 as a novel HSF2-interacting protein partner and regulator, in an unbiased manner, and show that HSF2 and HDAC1 localize in the same cells in the developing mouse cortex and human cerebral organoids (hCOs). We also demonstrate that HDAC1, through its catalytic activity, destabilizes the HSF2 protein, through HSF2 poly-ubiquitination and proteasomal degradation, under both normal and stress conditions.

Mitotic block and epigenetic repression underlie neurodevelopmental defects and neurobehavioral deficits in congenital heart disease

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart disease associated with microcephaly and poor neurodevelopmental outcomes. Here we show that the Ohia HLHS mouse model, with mutations in Sap130, a chromatin modifier, and Pcdha9, a cell adhesion protein, also exhibits microcephaly associated with mitotic block and increased apoptosis leading to impaired cortical neurogenesis. Transcriptome profiling, DNA methylation, and Sap130 ChIPseq analyses all demonstrate dysregulation of genes associated with autism and cognitive impairment. This includes perturbation of REST transcriptional regulation of neurogenesis, disruption of CREB signaling regulating synaptic plasticity, and defects in neurovascular coupling mediating cerebral blood flow. Adult mice harboring either the Pcdha9 mutation, which show normal brain anatomy, or forebrain-specific Sap130 deletion via Emx1-Cre, which show microcephaly, both demonstrate learning and memory deficits and autism-like behavior. These findings provide mechanistic insights indicating the adverse neurodevelopment in HLHS may involve cell autonomous/nonautonomous defects and epigenetic dysregulation.

HDAC1 and HDAC2 orchestrate Wnt signaling to regulate neural progenitor transition during brain development

Tightly controlled neurogenesis is crucial for generating the precise number of neurons and establishing the intricate architecture of the cortex, with deficiencies often leading to neurodevelopmental disorders. Neuroepithelial progenitors (NPs) transit into radial glial progenitors (RGPs) to initiate neural differentiation, yet the governing mechanisms remain elusive. Here, we found that histone deacetylases 1 and 2 (HDAC1/2) mediated suppression of Wnt signaling is essential for the NP-to-RGP transition. Conditional depletion of HDAC1/2 from NPs upregulated Wnt signaling genes, impairing the transition to RGPs and resulting in rosette structures within the neocortex. Multi-omics analysis revealed that HDAC1/2 are critical for downregulating Wnt signaling, identifying Wnt9a as a key target. Overexpression of Wnt9a led to an increased population of NPs and the disruption of cortical organization. Notably, Wnt inhibitor administration partially rescued the disrupted cortical architecture. Our findings reveal the significance of tightly controlled Wnt signaling through epigenetic mechanisms in neocortical development.

Lactylation: A Novel Post-Translational Modification with Clinical Implications in CNS Diseases

Lactate, an important metabolic product, provides energy to neural cells during energy depletion or high demand and acts as a signaling molecule in the central nervous system. Recent studies revealed that lactate-mediated protein lactylation regulates gene transcription and influences cell fate, metabolic processes, inflammation, and immune responses. This review comprehensively examines the regulatory roles and mechanisms of lactylation in neurodevelopment, neuropsychiatric disorders, brain tumors, and cerebrovascular diseases. This analysis indicates that lactylation has multifaceted effects on central nervous system function and pathology, particularly in hypoxia-induced brain damage. Highlighting its potential as a novel therapeutic target, lactylation may play a significant role in treating neurological diseases. By summarizing current findings, this review aims to provide insights and guide future research and clinical strategies for central nervous system disorders.

Role of histone modifications in neurogenesis and neurodegenerative disease development

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

Mitotic Block and Epigenetic Repression Underlie Neurodevelopmental Defects and Neurobehavioral Deficits in Congenital Heart Disease

Poor neurodevelopment is often observed with congenital heart disease (CHD), especially with mutations in chromatin modifiers. Here analysis of mice with hypoplastic left heart syndrome (HLHS) arising from mutations in Sin3A associated chromatin modifier Sap130 , and adhesion protein Pcdha9, revealed neurodevelopmental and neurobehavioral deficits reminiscent of those in HLHS patients. Microcephaly was associated with impaired cortical neurogenesis, mitotic block, and increased apoptosis. Transcriptional profiling indicated dysregulated neurogenesis by REST, altered CREB signaling regulating memory and synaptic plasticity, and impaired neurovascular coupling modulating cerebral blood flow. Many neurodevelopmental/neurobehavioral disease pathways were recovered, including autism and cognitive impairment. These same pathways emerged from genome-wide DNA methylation and Sap130 chromatin immunoprecipitation sequencing analyses, suggesting epigenetic perturbation. Mice with Pcdha9 mutation or forebrain-specific Sap130 deletion without CHD showed learning/memory deficits and autism-like behavior. These novel findings provide mechanistic insights indicating the adverse neurodevelopment in HLHS may involve cell autonomous/nonautonomous defects and epigenetic dysregulation and suggest new avenues for therapy.

Epigenetic Regulation in Schizophrenia: Focus on Methylation and Histone Modifications in Human Studies

Despite extensive research over the last few decades, the etiology of schizophrenia (SZ) remains unclear. SZ is a pathological disorder that is highly debilitating and deeply affects the lifestyle and minds of those affected. Several factors (one or in combination) have been reported as contributors to SZ pathogenesis, including neurodevelopmental, environmental, genetic and epigenetic factors. Deoxyribonucleic acid (DNA) methylation and post-translational modification (PTM) of histone proteins are potentially contributing epigenetic processes involved in transcriptional activity, chromatin folding, cell division and apoptotic processes, and DNA damage and repair. After establishing a summary of epigenetic processes in the context of schizophrenia, this review aims to highlight the current understanding of the role of DNA methylation and histone PTMs in this disorder and their potential roles in schizophrenia pathophysiology and pathogenesis.

Maternal sevoflurane exposure increases the epilepsy susceptibility of adolescent offspring by interrupting interneuron development

BACKGROUND

Exposure to general anesthesia influences neuronal functions during brain development. Recently, interneurons were found to be involved in developmental neurotoxicity by anesthetic exposure. But the underlying mechanism and long-term consequences remain elusive.

METHODS

Pregnant mice received 2.5% sevoflurane for 6-h on gestational day 14.5. Pentylenetetrazole (PTZ)-induced seizure, anxiety- and depression-like behavior tests were performed in 30- and 60-day-old male offspring. Cortical interneurons were labeled using Rosa26-EYFP/-; Nkx2.1-Cre mice. Immunofluorescence and electrophysiology were performed to determine the cortical interneuron properties. Q-PCR and in situ hybridization (ISH) were performed for the potential mechanism, and the finding was further validated by in utero electroporation (IUE).

RESULTS

In this study, we found that maternal sevoflurane exposure increased epilepsy susceptibility by using pentylenetetrazole (PTZ) induced-kindling models and enhanced anxiety- and depression-like behaviors in adolescent offspring. After sevoflurane exposure, the highly ordered cortical interneuron migration was disrupted in the fetal cortex. In addition, the resting membrane potentials of fast-spiking interneurons in the sevoflurane-treated group were more hyperpolarized in adolescence accompanied by an increase in inhibitory synapses. Both q-PCR and ISH indicated that CXCL12/CXCR4 signaling pathway downregulation might be a potential mechanism under sevoflurane developmental neurotoxicity which was further confirmed by IUE and behavioral tests. Although the above effects were obvious in adolescence, they did not persist into adulthood.

CONCLUSIONS

Our findings demonstrate that maternal anesthesia impairs interneuron migration through the CXCL12/CXCR4 signaling pathway, and influences the interneuron properties, leading to the increased epilepsy susceptibility in adolescent offspring. Our study provides a novel perspective on the developmental neurotoxicity of the mechanistic link between maternal use of general anesthesia and increased susceptibility to epilepsy.

MKL/SRF and Bcl6 mutual transcriptional repression safeguards the fate and positioning of neocortical progenitor cells mediated by RhoA

During embryogenesis, multiple intricate and intertwined cellular signaling pathways coordinate cell behavior. Their slightest alterations can have dramatic consequences for the cells and the organs they form. The transcriptional repressor Bcl6 was recently found as important for brain development. However, its regulation and integration with other signals is unknown. Using in vivo functional approaches combined with molecular mechanistic analysis, we identified a reciprocal regulatory loop between B cell lymphoma 6 (Bcl6) and the RhoA-regulated transcriptional complex megakaryoblastic leukemia/serum response factor (MKL/SRF). We show that Bcl6 physically interacts with MKL/SRF, resulting in a down-regulation of the transcriptional activity of both Bcl6 and MKL/SRF. This molecular cross-talk is essential for the control of proliferation, neurogenesis, and spatial positioning of neural progenitors. Overall, our data highlight a regulatory mechanism that controls neuronal production and neocortical development and reveal an MKL/SRF and Bcl6 interaction that may have broader implications in other physiological functions and in diseases.

METTL3-Dependent N6-Methyladenosine Modification Programs Human Neural Progenitor Cell Proliferation

METTL3, a methyltransferase responsible for N6-methyladenosine (m6A) modification, plays key regulatory roles in mammal central neural system (CNS) development. However, the specific epigenetic mechanisms governing human CNS development remain poorly elucidated. Here, we generated small-molecule-assisted shut-off (SMASh)-tagged hESC lines to reduce METTL3 protein levels, and found that METTL3 is not required for human neural progenitor cell (hNPC) formation and neuron differentiation. However, METTL3 deficiency inhibited hNPC proliferation by reducing SLIT2 expression. Mechanistic studies revealed that METTL3 degradation in hNPCs significantly decreased the enrichment of m6A in SLIT2 mRNA, consequently reducing its expression. Our findings reveal a novel functional target (SLIT2) for METTL3 in hNPCs and contribute to a better understanding of m6A-dependent mechanisms in hNPC proliferation.

Lactate and Lactylation in the Brain: Current Progress and Perspectives

As the final product of glycolysis, lactate features not only as an energy substrate, a metabolite, and a signaling molecule in a variety of diseases-such as cancer, inflammation, and sepsis-but also as a regulator of protein lactylation; this is a newly proposed epigenetic modification that is considered to be crucial for energy metabolism and signaling in brain tissues under both physiological and pathological conditions. In this review, evidence on lactylation from studies on lactate metabolism and disease has been summarized, revealing the function of lactate and its receptors in the regulation of brain function and summarizing the levels of lactylation expression in various brain diseases. Finally, the function of lactate and lactylation in the brain and the potential mechanisms of intervention in brain diseases are presented and discussed, providing optimal perspectives for future research on the role of lactylation in the brain.

Ccdc85c-Par3 condensates couple cell polarity with Notch to control neural progenitor proliferation

Polarity proteins regulate the proliferation and differentiation of neural progenitors to generate neurons during brain development through multiple signaling pathways. However, how cell polarity couples the signaling pathways remains unclear. Here, we show that coiled-coil domain-containing protein 85c (Ccdc85c) interacts with the polarity protein Par3 to regulate the proliferation of radial glial cells (RGCs) via phase separation coupled to percolation (PSCP). We find that the interaction with Ccdc85c relieves the intramolecular auto-inhibition of Par3, which leads to PSCP of Par3. Downregulation of Ccdc85c causes RGC differentiation. Importantly, the open conformation of Par3 facilitates the recruitment of the Notch regulator Numb to the Par3 condensates, which might prevent the attenuation of Notch activity to maintain RGC proliferation. Furthermore, ectopic activation of Notch signaling rescues RGC proliferation defects caused by the downregulation of Ccdc85c. These results suggest that Ccdc85c-mediated PSCP of Par3 regulates Notch signaling to control RGC proliferation during brain development.

Protein posttranslational modifications in health and diseases: Functions, regulatory mechanisms, and therapeutic implications

Protein posttranslational modifications (PTMs) refer to the breaking or generation of covalent bonds on the backbones or amino acid side chains of proteins and expand the diversity of proteins, which provides the basis for the emergence of organismal complexity. To date, more than 650 types of protein modifications, such as the most well-known phosphorylation, ubiquitination, glycosylation, methylation, SUMOylation, short-chain and long-chain acylation modifications, redox modifications, and irreversible modifications, have been described, and the inventory is still increasing. By changing the protein conformation, localization, activity, stability, charges, and interactions with other biomolecules, PTMs ultimately alter the phenotypes and biological processes of cells. The homeostasis of protein modifications is important to human health. Abnormal PTMs may cause changes in protein properties and loss of protein functions, which are closely related to the occurrence and development of various diseases. In this review, we systematically introduce the characteristics, regulatory mechanisms, and functions of various PTMs in health and diseases. In addition, the therapeutic prospects in various diseases by targeting PTMs and associated regulatory enzymes are also summarized. This work will deepen the understanding of protein modifications in health and diseases and promote the discovery of diagnostic and prognostic markers and drug targets for diseases.

A Human-Specific De Novo Gene Promotes Cortical Expansion and Folding

Newly originated de novo genes have been linked to the formation and function of the human brain. However, how a specific gene originates from ancestral noncoding DNAs and becomes involved in the preexisting network for functional outcomes remains elusive. Here, a human-specific de novo gene, SP0535, is identified that is preferentially expressed in the ventricular zone of the human fetal brain and plays an important role in cortical development and function. In human embryonic stem cell-derived cortical organoids, knockout of SP0535 compromises their growth and neurogenesis. In SP0535 transgenic (TG) mice, expression of SP0535 induces fetal cortex expansion and sulci and gyri-like structure formation. The progenitors and neurons in the SP0535 TG mouse cortex tend to proliferate and differentiate in ways that are unique to humans. SP0535 TG adult mice also exhibit improved cognitive ability and working memory. Mechanistically, SP0535 interacts with the membrane protein Na⁺ /K⁺ ATPase subunit alpha-1 (ATP1A1) and releases Src from the ATP1A1-Src complex, allowing increased level of Src phosphorylation that promotes cell proliferation. Thus, SP0535 is the first proven human-specific de novo gene that promotes cortical expansion and folding, and can function through incorporating into an existing conserved molecular network.

Tip60/KAT5 Histone Acetyltransferase Is Required for Maintenance and Neurogenesis of Embryonic Neural Stem Cells

Epigenetic regulation via epigenetic factors in collaboration with tissue-specific transcription factors is curtail for establishing functional organ systems during development. Brain development is tightly regulated by epigenetic factors, which are coordinately activated or inactivated during processes, and their dysregulation is linked to brain abnormalities and intellectual disability. However, the precise mechanism of epigenetic regulation in brain development and neurogenesis remains largely unknown. Here, we show that Tip60/KAT5 deletion in neural stem/progenitor cells (NSCs) in mice results in multiple abnormalities of brain development. Tip60-deficient embryonic brain led to microcephaly, and proliferating cells in the developing brain were reduced by Tip60 deficiency. In addition, neural differentiation and neuronal migration were severely affected in Tip60-deficient brains. Following neurogenesis in developing brains, gliogenesis started from the earlier stage of development in Tip60-deficient brains, indicating that Tip60 is involved in switching from neurogenesis to gliogenesis during brain development. It was also confirmed in vitro that poor neurosphere formation, proliferation defects, neural differentiation defects, and accelerated astrocytic differentiation in mutant NSCs are derived from Tip60-deficient embryonic brains. This study uncovers the critical role of Tip60 in brain development and NSC maintenance and function in vivo and in vitro.

Epigenetics of neural differentiation: Spotlight on enhancers

Neural induction, both in vivo and in vitro, includes cellular and molecular changes that result in phenotypic specialization related to specific transcriptional patterns. These changes are achieved through the implementation of complex gene regulatory networks. Furthermore, these regulatory networks are influenced by epigenetic mechanisms that drive cell heterogeneity and cell-type specificity, in a controlled and complex manner. Epigenetic marks, such as DNA methylation and histone residue modifications, are highly dynamic and stage-specific during neurogenesis. Genome-wide assessment of these modifications has allowed the identification of distinct non-coding regulatory regions involved in neural cell differentiation, maturation, and plasticity. Enhancers are short DNA regulatory regions that bind transcription factors (TFs) and interact with gene promoters to increase transcriptional activity. They are of special interest in neuroscience because they are enriched in neurons and underlie the cell-type-specificity and dynamic gene expression profiles. Classification of the full epigenomic landscape of neural subtypes is important to better understand gene regulation in brain health and during diseases. Advances in novel next-generation high-throughput sequencing technologies, genome editing, Genome-wide association studies (GWAS), stem cell differentiation, and brain organoids are allowing researchers to study brain development and neurodegenerative diseases with an unprecedented resolution. Herein, we describe important epigenetic mechanisms related to neurogenesis in mammals. We focus on the potential roles of neural enhancers in neurogenesis, cell-fate commitment, and neuronal plasticity. We review recent findings on epigenetic regulatory mechanisms involved in neurogenesis and discuss how sequence variations within enhancers may be associated with genetic risk for neurological and psychiatric disorders.

The epigenetic state of EED-Gli3-Gli1 regulatory axis controls embryonic cortical neurogenesis

Mutations in the embryonic ectoderm development (EED) cause Weaver syndrome, but whether and how EED affects embryonic brain development remains elusive. Here, we generated a mouse model in which Eed was deleted in the forebrain to investigate the role of EED. We found that deletion of Eed decreased the number of upper-layer neurons but not deeper-layer neurons starting at E16.5. Transcriptomic and genomic occupancy analyses revealed that the epigenetic states of a group of cortical neurogenesis-related genes were altered in Eed knockout forebrains, followed by a decrease of H3K27me3 and an increase of H3K27ac marks within the promoter regions. The switching of H3K27me3 to H3K27ac modification promoted the recruitment of RNA-Pol2, thereby enhancing its expression level. The small molecule activator SAG or Ptch1 knockout for activating Hedgehog signaling can partially rescue aberrant cortical neurogenesis. Taken together, we proposed a novel EED-Gli3-Gli1 regulatory axis that is critical for embryonic brain development.

Dynamic profiling and functional interpretation of histone lysine crotonylation and lactylation during neural development

Metabolites such as crotonyl-CoA and lactyl-CoA influence gene expression by covalently modifying histones, known as histone lysine crotonylation (Kcr) and lysine lactylation (Kla). However, the existence patterns, dynamic changes, biological functions and associations of these modifications with histone lysine acetylation and gene expression during mammalian development remain largely unknown. Here, we find that histone Kcr and Kla are widely distributed in the brain and undergo global changes during neural development. By profiling the genome-wide dynamics of H3K9ac, H3K9cr and H3K18la in combination with ATAC and RNA sequencing, we reveal that these marks are tightly correlated with chromatin state and gene expression, and extensively involved in transcriptome remodeling to promote cell-fate transitions in the developing telencephalon. Importantly, we demonstrate that global Kcr and Kla levels are not the consequence of transcription and identify the histone deacetylases (HDACs) 1-3 as novel ‘erasers’ of H3K18la. Using P19 cells as an induced neural differentiation system, we find that HDAC1-3 inhibition by MS-275 pre-activates neuronal transcriptional programs by stimulating multiple histone lysine acylations simultaneously. These findings suggest that histone Kcr and Kla play crucial roles in the epigenetic regulation of neural development.

The role of histone modifications: from neurodevelopment to neurodiseases

Epigenetic regulatory mechanisms, including DNA methylation, histone modification, chromatin remodeling, and microRNA expression, play critical roles in cell differentiation and organ development through spatial and temporal gene regulation. Neurogenesis is a sophisticated and complex process by which neural stem cells differentiate into specialized brain cell types at specific times and regions of the brain. A growing body of evidence suggests that epigenetic mechanisms, such as histone modifications, allow the fine-tuning and coordination of spatiotemporal gene expressions during neurogenesis. Aberrant histone modifications contribute to the development of neurodegenerative and neuropsychiatric diseases. Herein, recent progress in understanding histone modifications in regulating embryonic and adult neurogenesis is comprehensively reviewed. The histone modifications implicated in neurodegenerative and neuropsychiatric diseases are also covered, and future directions in this area are provided.

DLX1 and the NuRD complex cooperate in enhancer decommissioning and transcriptional repression

In the developing subpallium, the fate decision between neurons and glia is driven by expression of Dlx1/2 or Olig1/2, respectively, two sets of transcription factors with a mutually repressive relationship. The mechanism by which Dlx1/2 repress progenitor and oligodendrocyte fate, while promoting transcription of genes needed for differentiation, is not fully understood. We identified a motif within DLX1 that binds RBBP4, a NuRD complex subunit. ChIP-seq studies of genomic occupancy of DLX1 and six different members of the NuRD complex show that DLX1 and NuRD colocalize to putative regulatory elements enriched near other transcription factor genes. Loss of Dlx1/2 leads to dysregulation of genome accessibility at putative regulatory elements near genes repressed by Dlx1/2, including Olig2. Consequently, heterozygosity of Dlx1/2 and Rbbp4 leads to an increase in the production of OLIG2+ cells. These findings highlight the importance of the interplay between transcription factors and chromatin remodelers in regulating cell-fate decisions.

miR-3189-targeted GLUT3 repression by HDAC2 knockdown inhibits glioblastoma tumorigenesis through regulating glucose metabolism and proliferation

BACKGROUND

Epigenetic regulations frequently appear in Glioblastoma (GBM) and are highly associated with metabolic alterations. Especially, Histone deacetylases (HDACs) correlates with the regulation of tumorigenesis and cell metabolism in GBM progression, and HDAC inhibitors report to have therapeutic efficacy in GBM and other neurological diseases; however, GBM prevention and therapy by HDAC inhibition lacks a mechanism in the focus of metabolic reprogramming.

METHODS

HDAC2 highly express in GBM and is analyzed in TCGA/GEPIA databases. Therefore, HDAC2 knockdown affects GBM cell death. Analysis of RNA sequencing and qRT-PCR reveals that miR-3189 increases and GLUT3 decreases by HDAC2 knockdown. GBM tumorigenesis also examines by using in vivo orthotopic xenograft tumor models. The metabolism change in HDAC2 knockdown GBM cells measures by glucose uptake, lactate production, and OCR/ECAR analysis, indicating that HDAC2 knockdown induces GBM cell death by inhibiting GLUT3.

RESULTS

Notably, GLUT3 was suppressed by increasing miR-3189, demonstrating that miR-3189-mediated GLUT3 inhibition shows an anti-tumorigenic effect and cell death by regulating glucose metabolism in HDAC2 knockdown GBM.

CONCLUSIONS

Our findings will demonstrate the central role of HDAC2 in GBM tumorigenesis through the reprogramming of glucose metabolism by controlling miR-3189-inhibited GLUT3 expression, providing a potential new therapeutic strategy for GBM treatment.

Androgens increase excitatory neurogenic potential in human brain organoids

The biological basis of male-female brain differences has been difficult to elucidate in humans. The most notable morphological difference is size, with male individuals having on average a larger brain than female individuals1,2, but a mechanistic understanding of how this difference arises remains unknown. Here we use brain organoids3 to show that although sex chromosomal complement has no observable effect on neurogenesis, sex steroids-namely androgens-lead to increased proliferation of cortical progenitors and an increased neurogenic pool. Transcriptomic analysis and functional studies demonstrate downstream effects on histone deacetylase activity and the mTOR pathway. Finally, we show that androgens specifically increase the neurogenic output of excitatory neuronal progenitors, whereas inhibitory neuronal progenitors are not increased. These findings reveal a role for androgens in regulating the number of excitatory neurons and represent a step towards understanding the origin of sex-related brain differences in humans.

HDAC1 Regulates Neuronal Differentiation

In adult hippocampal neurogenesis, chromatin modification plays an important role in neural stem cell self-renewal and differentiation by regulating the expression of multiple genes. Histone deacetylases (HDACs), which remove acetyl groups from histones, create a non-permissive chromatin that prevents transcription of genes involved in adult neurogenesis. HDAC inhibitors have been shown to promote adult neurogenesis and have also been used to treat nervous system disorders, such as epilepsy. However, most HDAC inhibitors are not specific and may have other targets. Therefore, it is important to decipher the role of individual HDACs in adult hippocampal neurogenesis. HDACs 1, 2, and 3 have been found expressed at different cellular stages during neurogenesis. Conditional deletion of HDAC2 in neural stem cells impairs neuronal differentiation in adult hippocampus. HDAC3 supports proliferation of adult hippocampal neural stem/progenitor cells. The role of HDAC1 in adult neurogenesis remains still open. Here, we used a conditional knock-out mouse to block HDAC1 expression in neural stem cells (Nestin+ cells) during hippocampal neurogenesis. Our results showed that both HDAC1 and HDAC2 are expressed in all cellular stages during hippocampal neurogenesis. Moreover, we found that deletion of HDAC1 by viral infection of neural stem cells is sufficient to compromise neuronal differentiation in vitro. However, we were unable to reduce the expression of HDAC1 in vivo using Nestin-CreERT2 mice. Understanding the role of HDAC1 may lead to ways to control stem cell proliferation and neuronal regeneration in the adult hippocampus, and to more specific HDAC therapeutics for neurological disorders.

PDK1 Regulates the Lengthening of G1 Phase to Balance RGC Proliferation and Differentiation during Cortical Neurogenesis

During cortical development, the balance between progenitor self-renewal and neurogenesis is critical for determining the size/morphology of the cortex. A fundamental feature of the developing cortex is an increase in the length of G1 phase in RGCs over the course of neurogenesis, which is a key determinant of progenitor fate choice. How the G1 length is temporally regulated remains unclear. Here, Pdk1, a member of the AGC kinase family, was conditionally disrupted by crossing an Emx1-Cre mouse line with a Pdk1fl/fl line. The loss of Pdk1 led to a shorter cell cycle accompanied by increased RGC proliferation specifically at late rather than early/middle neurogenic stages, which was attributed to impaired lengthening of G1 phase. Coincidently, apical-to-basal interkinetic nuclear migration was accelerated in Pdk1 cKO cortices. Consequently, we detected an increased neuronal output at P0. We further showed the significant upregulation of the cell cycle regulator cyclin D1 and its activator Myc in the cKO cortices relative to those of control animals. Overall, we have identified a novel role for PDK1 in cortical neurogenesis. PDK1 functions as an upstream regulator of the Myc-cyclin D1 pathway to control the lengthening of G1 phase and the balance between RGC proliferation and differentiation.

Transcription factor 4 controls positioning of cortical projection neurons through regulation of cell adhesion

The establishment of neural circuits depends on precise neuronal positioning in the cortex, which occurs via a tightly coordinated process of neuronal differentiation, migration, and terminal localization. Deficits in this process have been implicated in several psychiatric disorders. Here, we show that the transcription factor Tcf4 controls neuronal positioning during brain development. Tcf4-deficient neurons become mispositioned in clusters when their migration to the cortical plate is complete. We reveal that Tcf4 regulates the expression of cell adhesion molecules to control neuronal positioning. Furthermore, through in vivo extracellular electrophysiology, we show that neuronal functions are disrupted after the loss of Tcf4. TCF4 mutations are strongly associated with schizophrenia and cause Pitt-Hopkins syndrome, which is characterized by severe intellectual disability. Thus, our results not only reveal the importance of neuronal positioning in brain development but also provide new insights into the potential mechanisms underlying neurological defects linked to TCF4 mutations.

Histone crotonylation regulates neural stem cell fate decisions by activating bivalent promoters

Histone lysine crotonylation (Kcr), an evolutionarily conserved and widespread non-acetyl short-chain lysine acylation, plays important roles in transcriptional regulation and disease processes. However, the genome-wide distribution, dynamic changes, and associations with gene expression of histone Kcr during developmental processes are largely unknown. In this study, we find that histone Kcr is mainly located in active promoter regions, acts as an epigenetic hallmark of highly expressed genes, and regulates genes participating in metabolism and proliferation. Moreover, elevated histone Kcr activates bivalent promoters to stimulate gene expression in neural stem/progenitor cells (NSPCs) by increasing chromatin openness and recruitment of RNA polymerase II (RNAP2). Functionally, these activated genes contribute to transcriptome remodeling and promote neuronal differentiation. Overall, histone Kcr marks active promoters with high gene expression and modifies the local chromatin environment to allow gene activation.

Inhibition of HDAC1 alleviates monocrotaline-induced pulmonary arterial remodeling through up-regulation of miR-34a

Background

It has been found that up-regulation of histone deacetylases 1 (HDAC1) is involved in the development of pulmonary arterial hypertension (PAH). However, it is still unclear whether inhibition of HDAC1 suppresses the development of PAH via restoring miR-34a level in monocrotaline (MCT)-induced PAH rats.

Methods

PAH rat models were induced by intraperitoneal injection of MCT. HDAC1 was suppressed by intraperitoneal injection of the class I HDAC inhibitor MS-275, and miR-34a was over-expressed via tail vein injection of miR-34a agomiR.

Results

HDAC1 protein was significantly increased in MCT-induced PAH rats; this was accompanied with down-regulation of miR-34a and subsequent up-regulation of matrix metalloproteinase 9 (MMP-9)/tissue inhibitor of metalloproteinase 1 (TIMP-1) and MMP-2/TIMP-2. Administration of PAH rats with MS-275 or miR-34a agomiR dramatically abolished MCT-induced reduction of miR-34a and subsequent up-regulation of MMP-9/TIMP-1 and MMP-2/TIMP-2, finally reduced extracellular matrix (ECM) accumulation, pulmonary arterial remodeling, right ventricular systolic pressure (RVSP) and right ventricle hypertrophy index (RVHI) in PAH rats.

Conclusions

HDAC1 contributes to the development of MCT-induced rat PAH by suppressing miR-34a level and subsequently up-regulating the ratio of MMP-9/TIMP-1 and MMP-2/TIMP-2. Inhibition of HDAC1 alleviates pulmonary arterial remodeling and PAH through up-regulation of miR-34a level and subsequent reduction of MMP-9/TIMP-1 and MMP-2/TIMP-2, suggesting that inhibition of HDAC1 might have potential value in the management of PAH.

Chromatin remodelling complexes in cerebral cortex development and neurodevelopmental disorders

The diverse number of neurons in the cerebral cortex are generated during development by neural stem cells lining the ventricle, and they continue maturing postnatally. Dynamic chromatin regulation in these neural stem cells is a fundamental determinant of the emerging property of the functional neural network, and the chromatin remodellers are critical determinants of this process. Chromatin remodellers participate in several steps of this process from proliferation, differentiation, migration leading to complex network formation which forms the basis of higher-order functions of cognition and behaviour. Here we review the role of these ATP-dependent chromatin remodellers in cortical development in health and disease and highlight several key mouse mutants of the subunits of the complexes which have revealed how the remodelling mechanisms control the cortical stem cell chromatin landscape for expression of stage-specific transcripts. Consistent with their role in cortical development, several putative risk variants in the subunits of the remodelling complexes have been identified as the underlying causes of several neurodevelopmental disorders. A basic understanding of the detailed molecular mechanism of their action is key to understating how mutations in the same networks lead to disease pathologies and perhaps pave the way for therapeutic development for these complex multifactorial disorders.

Maternal sevoflurane exposure induces temporary defects in interkinetic nuclear migration of radial glial progenitors in the fetal cerebral cortex through the Notch signalling pathway

OBJECTIVES

The effects of general anaesthetics on fetal brain development remain elusive. Radial glial progenitors (RGPs) generate the majority of neurons in developing brains. Here, we evaluated the acute alterations in RGPs after maternal sevoflurane exposure.

METHODS

Pregnant mice were exposed to 2.5% sevoflurane for 6 hours on gestational day 14.5. Interkinetic nuclear migration (INM) of RGPs in the ventricular zone (VZ) of the fetal brain was evaluated by thymidine analogues labelling. Cell fate of RGP progeny was determined by immunostaining using various neural markers. The Morris water maze (MWM) was used to assess the neurocognitive behaviours of the offspring. RNA sequencing (RNA-Seq) was performed for the potential mechanism, and the potential mechanism validated by quantitative real-time PCR (qPCR), Western blot and rescue experiments. Furthermore, INM was examined in human embryonic stem cell (hESC)-derived 3D cerebral organoids.

RESULTS

Maternal sevoflurane exposure induced temporary abnormities in INM, and disturbed the cell cycle progression of RGPs in both rodents and cerebral organoids without cell fate alternation. RNA-Seq analysis, qPCR and Western blot showed that the Notch signalling pathway was a potential downstream target. Reactivation of Notch by Jag1 and NICD overexpression rescued the defects in INM. Young adult offspring showed no obvious cognitive impairments in MWM.

CONCLUSIONS

Maternal sevoflurane exposure during neurogenic period temporarily induced abnormal INM of RGPs by targeting the Notch signalling pathway without inducing long-term effects on RGP progeny cell fate or offspring cognitive behaviours. More importantly, the defects of INM in hESC-derived cerebral organoids provide a novel insight into the effects of general anaesthesia on human brain development.

A unique macrophage subpopulation signals directly to progenitor cells to promote regenerative neurogenesis in the zebrafish spinal cord

Central nervous system injury re-initiates neurogenesis in anamniotes (amphibians and fishes), but not in mammals. Activation of the innate immune system promotes regenerative neurogenesis, but it is fundamentally unknown whether this is indirect through the activation of known developmental signaling pathways or whether immune cells directly signal to progenitor cells using mechanisms that are unique to regeneration. Using single-cell RNA-seq of progenitor cells and macrophages, as well as cell-type-specific manipulations, we provide evidence for a direct signaling axis from specific lesion-activated macrophages to spinal progenitor cells to promote regenerative neurogenesis in zebrafish. Mechanistically, TNFa from pro-regenerative macrophages induces Tnfrsf1a-mediated AP-1 activity in progenitors to increase regeneration-promoting expression of hdac1 and neurogenesis. This establishes the principle that macrophages directly communicate to spinal progenitor cells via non-developmental signals after injury, providing potential targets for future interventions in the regeneration-deficient spinal cord of mammals.

[Role and mechanism of histone deacetylases in mouse neuronal development]

OBJECTIVE

To study the role and mechanism of histone deacetylase 1 (HDAC1) and histone deacetylase 2 (HDAC2) in mouse neuronal development.

METHODS

The mice with Synapsin1-Cre recombinase were bred with HDAC1&2^flox/flox mice to obtain the mice with neuron-specific HDAC1&2 conditional knockout (knockout group), and their littermates without HDAC1&2 knockout were used as the control group. The general status of the mice was observed and survival curves were plotted. Brain tissue samples were collected from the knockout group and the control group. Western blot and immunohistochemistry were used to measure the protein expression of related neuronal and axonal markers, neuronal nuclear antigen (NeuN), non-phosphorylated neurofilament heavy chain (np-NF200), and phosphorylated neurofilament heavy chain (p-NF200), as well as the downstream effector of the mTOR signaling pathway, phosphorylated S6 ribosomal protein (p-S6).

RESULTS

The mice with HDAC1&2 conditional knockout usually died within one month after birth and were significantly smaller than those in the control group, with motor function abnormalities such as tremor and clasping of hindlimbs. Compared with the control group, the knockout group had significant reductions in the protein expression levels of NeuN, np-NF200, p-NF200, and p-S6 (P < 0.05; n=3).

CONCLUSIONS

Deletion of HDAC1 and HDAC2 in mouse neurons results in reduced neuronal maturation and axonal dysplasia, which may be associated with the mTOR signaling pathway.

Knock-Down of HDAC2 in Human Induced Pluripotent Stem Cell Derived Neurons Improves Neuronal Mitochondrial Dynamics, Neuronal Maturation and Reduces Amyloid Beta Peptides

Histone deacetylase 2 (HDAC2) is a major HDAC protein in the adult brain and has been shown to regulate many neuronal genes. The aberrant expression of HDAC2 and subsequent dysregulation of neuronal gene expression is implicated in neurodegeneration and brain aging. Human induced pluripotent stem cell-derived neurons (hiPSC-Ns) are widely used models for studying neurodegenerative disease mechanisms, but the role of HDAC2 in hiPSC-N differentiation and maturation has not been explored. In this study, we show that levels of HDAC2 progressively decrease as hiPSCs are differentiated towards neurons. This suppression of HDAC2 inversely corresponds to an increase in neuron-specific isoforms of Endophilin-B1, a multifunctional protein involved in mitochondrial dynamics. Expression of neuron-specific isoforms of Endophilin-B1 is accompanied by concomitant expression of a neuron-specific alternative splicing factor, SRRM4. Manipulation of HDAC2 and Endophilin-B1 using lentiviral approaches shows that the knock-down of HDAC2 or the overexpression of a neuron-specific Endophilin-B1 isoform promotes mitochondrial elongation and protects against cytotoxic stress in hiPSC-Ns, while HDAC2 knock-down specifically influences genes regulating mitochondrial dynamics and synaptogenesis. Furthermore, HDAC2 knock-down promotes enhanced mitochondrial respiration and reduces levels of neurotoxic amyloid beta peptides. Collectively, our study demonstrates a role for HDAC2 in hiPSC-neuronal differentiation, highlights neuron-specific isoforms of Endophilin-B1 as a marker of differentiating hiPSC-Ns and demonstrates that HDAC2 regulates key neuronal and mitochondrial pathways in hiPSC-Ns.

Early Life Stress Induced DNA Methylation of Monoamine Oxidases Leads to Depressive-Like Behavior

Major depressive disorder (MDD) is coming to be the regarded as one of the leading causes for human disabilities. Due to its complicated pathological process, the etiology is still unclear and the treatment is still targeting at the monoamine neurotransmitters. Early life stress has been known as a major cause for MDD, but how early life stress affects adult monoaminergic activity is not clear either. Recently, DNA methylation is considered to be the key mechanism of epigenetics and might play a role in early life stress induced mental illness. DNA methylation is an enzymatic covalent modification of DNA, has been one of the main epigenetic mechanisms investigated. The metabolic enzyme for the monoamine neurotransmitters, monoamine oxidases A/B (MAO A/MAO B) are the prime candidates for the investigation into the role of DNA methylation in mental disorders. In this review, we will review recent advances about the structure and physiological function of monoamine oxidases (MAO), brief narrative other factors include stress induced changes, early life stress, perinatal depression (PD) relationship with other epigenetic changes, such as DNA methylation, microRNA (miRNA). This review will shed light on the epigenetic changes involved in MDD, which may provide potential targets for future therapeutics in depression pathogenesis.

Wnt/β-Catenin Signaling in Neural Stem Cell Homeostasis and Neurological Diseases

Neural stem/progenitor cells (NSCs) maintain the ability of self-renewal and differentiation and compose the complex nervous system. Wnt signaling is thought to control the balance of NSC proliferation and differentiation via the transcriptional coactivator β-catenin during brain development and adult tissue homeostasis. Disruption of Wnt signaling may result in developmental defects and neurological diseases. Here, we summarize recent findings of the roles of Wnt/β-catenin signaling components in NSC homeostasis for the regulation of functional brain circuits. We also suggest that the potential role of Wnt/β-catenin signaling might lead to new therapeutic strategies for neurological diseases, including, but not limited to, spinal cord injury, Alzheimer's disease, Parkinson's disease, and depression.

Regulation of Central Nervous System Development by Class I Histone Deacetylases

Neurodevelopment is a highly complex process composed of several carefully regulated events starting from the proliferation of neuroepithelial cells and culminating with and refining of neural networks and synaptic transmission. Improper regulation of any of these neurodevelopmental events often results in severe brain dysfunction. Accumulating evidence indicates that epigenetic modifications of chromatin play a key role in neurodevelopmental regulation. Among these modifications are histone acetylation and deacetylation, which control access of transcription factors to DNA, thereby regulating gene transcription. Histone deacetylation, which restricts access of transcription factor repressing gene transcription, involves the action of members of a family of 18 enzymes, the histone deacetylases (HDAC), which are subdivided in 4 subgroups. This review focuses on the Group 1 HDACs - HDAC 1, 2, 3, and 8. Although much of the evidence for HDAC involvement in neurodevelopment has come from the use of pharmacological inhibitors, because these agents are generally nonselective with regard to their effects on individual members of the HDAC family, this review is limited to evidence garnered from the use of molecular genetic approaches. Our review describes that Class I HDACs play essential roles in all phases of neurodevelopment. Modulation of the activity of individual HDACs could be an important therapeutic approach for neurodevelopmental and psychiatric disorders.

Histone deacetylases 1, 2 and 3 in nervous system development

Although histone acetylases (HDACS) were initially believed to render chromatin in a transcriptionally repressed state by deacetylating histones, it is now known that they both repress and activate transcription. Moreover, HDACs regulate the activity and/or function of a large number of other cellular proteins localized in the nucleus and cytoplasm. Accumulating evidence indicates that HDACs also play a key role in the development of the nervous system. This review focuses on three classical HDACS - HDACs 1, 2 and 3. Although much evidence on the involvement of HDACs in neurodevelopment has come from the use of pharmacological inhibitors, because these agents are not specific in their action on individual HDAC proteins, this review only describes evidence derived from the use of molecular genetic approaches. Our review describes that HDACs 1, 2 and 3 play crucial roles in neurodevelopment by regulating neurogenesis, gliogenesis, the development of neural circuitry and synaptic transmission.

Recent advances in understanding neocortical development

The neocortex is the largest part of the mammalian brain and is the seat of our higher cognitive functions. This outstanding neural structure increased massively in size and complexity during evolution in a process recapitulated today during the development of extant mammals. Accordingly, defects in neocortical development commonly result in severe intellectual and social deficits. Thus, understanding the development of the neocortex benefits from understanding its evolution and disease and also informs about their underlying mechanisms. Here, I briefly summarize the most recent and outstanding advances in our understanding of neocortical development and focus particularly on dorsal progenitors and excitatory neurons. I place special emphasis on the specification of neural stem cells in distinct classes and their proliferation and production of neurons and then discuss recent findings on neuronal migration. Recent discoveries on the genetic evolution of neocortical development are presented with a particular focus on primates. Progress on all these fronts is being accelerated by high-throughput gene expression analyses and particularly single-cell transcriptomics. I end with novel insights into the involvement of microglia in embryonic brain development and how improvements in cultured cerebral organoids are gradually consolidating them as faithful models of neocortex development in humans.