Molecular Control of Oligodendrocyte Development

Perilipin-2 mediates ferroptosis in oligodendrocyte progenitor cells and myelin injury after ischemic stroke

JOURNAL/nrgr/04.03/01300535-202507000-00024/figure1/v/2024-09-09T124005Z/r/image-tiff Differentiation of oligodendrocyte progenitor cells into mature myelin-forming oligodendrocytes contributes to remyelination. Failure of remyelination due to oligodendrocyte progenitor cell death can result in severe nerve damage. Ferroptosis is an iron-dependent form of regulated cell death caused by membrane rupture induced by lipid peroxidation, and plays an important role in the pathological process of ischemic stroke. However, there are few studies on oligodendrocyte progenitor cell ferroptosis. We analyzed transcriptome sequencing data from GEO databases and identified a role of ferroptosis in oligodendrocyte progenitor cell death and myelin injury after cerebral ischemia. Bioinformatics analysis suggested that perilipin-2 (PLIN2) was involved in oligodendrocyte progenitor cell ferroptosis. PLIN2 is a lipid storage protein and a marker of hypoxia-sensitive lipid droplet accumulation. For further investigation, we established a mouse model of cerebral ischemia/reperfusion. We found significant myelin damage after cerebral ischemia, as well as oligodendrocyte progenitor cell death and increased lipid peroxidation levels around the infarct area. The ferroptosis inhibitor, ferrostatin-1, rescued oligodendrocyte progenitor cell death and subsequent myelin injury. We also found increased PLIN2 levels in the peri-infarct area that co-localized with oligodendrocyte progenitor cells. Plin2 knockdown rescued demyelination and improved neurological deficits. Our findings suggest that targeting PLIN2 to regulate oligodendrocyte progenitor cell ferroptosis may be a potential therapeutic strategy for rescuing myelin damage after cerebral ischemia.

Galectin-3 alleviates demyelination by modulating microglial anti-inflammatory polarization through PPARγ-CD36 axis

Demyelination is characterized by disruption of myelin sheath and disorders in myelin formation. Currently, there are no effective therapeutic treatments available. Microglia, especially anti-inflammatory phenotype microglia are critical for remyelination. Galectin-3 (Gal-3), which is known to modulate microglia activation, is correlated with myelination. In this study, we aimed to elucidate the roles of Gal-3 during myelin formation and explore the efficiency and mechanism of rGal-3 administration in remyelination. We enrolled Gal-3 knockout (Lgals3 KO) mice and demonstrated Lgals3 KO causes demyelination during spontaneous myelinogenesis. We performed a cuprizone (CPZ) intoxication model and found Lgals3 KO aggravates demyelinated lesions and favors microglial pro-inflammatory phenotype polarization. Recombinant Gal-3 (rGal-3) administration alleviates CPZ intoxication and drives microglial towards anti-inflammatory phenotype. Additionally, RNA sequencing results reveal the correlation between Gal-3 and the PPARγ-CD36 axis. Thus, we performed SSO and GW9662 administration to inhibit the activation of the PPARγ-CD36 axis and found that rGal-3 administration modulates microglial phenotype polarization by regulating the PPARγ-CD36 axis. Together, our findings highlight the importance of Gal-3 in myelination and provide insights into rGal-3 administration for modulating microglial anti-inflammatory phenotype polarization through the PPARγ-CD36 axis.

Progesterone alleviates esketamine-induced hypomyelination via PI3K/Akt signaling pathway in the developing rat brain

The neurodevelopmental toxicity of anesthetics has been confirmed repeatedly, and esketamine is now widely used in pediatric surgeries. Oligodendrocyte precursor cells (OPCs) evolved into mature oligodendrocytes (OLs) and formed myeline sheath during the early brain development. In this study, we investigated whether esketamine exposure interrupted development of OPCs and induced hypomyelination in rats. Further we explored the roles of PI3K/Akt phosphorylation in OPCs development and myelination. Sprague Dawley rats with different ages (postnatal day (P) 1, 3, 7 and 12) were exposed to 40mg/kg esketamine. Progesterone treatment was given (16 mg/kg per day for 3 days) 24 h after esketamine exposure via the intraperitoneal route. Corpus callosum tissues were collected at P8 or P14 for western blot and immunofluorescence analyses. Esketamine exposure at P7 and P12 significantly reduced myelin basic protein (MBP) expression and CC1+ OLs number in corpus callosum. Esketamine exposure at P7 not only aggravated the mature OLs apoptosis, also decreased the OPCs proliferation and differentiation, which was related with dephosphorylation of PI3K/Akt. Progesterone was able to promote OPCs differentiation and ameliorate esketamine-induced hypomyelination by enhancing PI3K/Akt phosphorylation. Stage-dependent abnormality of OPCs/OLs after esketamine leads to the esketamine-induced hypomyelination. Esketamine interrupted OPCs evolution via PI3K/Akt signaling pathway, which can be ameliorated by progesterone.

The gut microbiota-oligodendrocyte axis: A promising pathway for modulating oligodendrocyte homeostasis and demyelination-associated disorders

The bidirectional regulation between the gut microbiota and brain, known as gut-brain axis, has received significant attention. The myelin sheath, produced by oligodendrocytes or Schwann cells, is essential for efficient nervous signal transmission and the maintenance of brain function. Growing evidence shows that both oligodendrogenesis and myelination are modulated by gut microbiota and its metabolites, and when dysbiosis occurs, changes in the microbiota composition and/or associated metabolites may impact developmental myelination and the occurrence of neurodevelopmental disabilities. Although the link between the microbiota and demyelinating disease such as multiple sclerosis has been extensively studied, our knowledge about the role of the microbiota in other myelin-related disorders, such as neurodegenerative diseases, is limited. Mechanistically, the microbiota-oligodendrocyte axis is primarily mediated by factors such as inflammation, the vagus nerve, endocrine hormones, and microbiota metabolites as evidenced by metagenomics, metabolomics, vagotomy, and morphological and molecular approaches. Treatments targeting this axis include probiotics, prebiotics, microbial metabolites, herbal bioactive compounds, and specific dietary management. In addition to the commonly used approaches, viral vector-mediated tracing and gene manipulation, integrated multiomics and multicenter clinical trials will greatly promote the mechanistic and interventional studies and ultimately, the development of new preventive and therapeutic strategies against gut-oligodendrocyte axis-mediated brain impairments. Interestingly, recent findings showed that microbiota dysbiosis can be induced by hippocampal myelin damage and is reversible by myelin-targeted drugs, which provides new insights into understanding how hippocampus-based functional impairment (such as in neurodegenerative Alzheimer's disease) regulates the peripheral homeostasis of microbiota and associated systemic disorders.

A New Acquaintance of Oligodendrocyte Precursor Cells in the Central Nervous System

Oligodendrocyte precursor cells (OPCs) are a heterogeneous multipotent population in the central nervous system (CNS) that appear during embryogenesis and persist as resident cells in the adult brain parenchyma. OPCs could generate oligodendrocytes to participate in myelination. Recent advances have renewed our knowledge of OPC biology by discovering novel markers of oligodendroglial cells, the myelin-independent roles of OPCs, and the regulatory mechanism of OPC development. In this review, we will explore the updated knowledge on OPC identity, their multifaceted roles in the CNS in health and diseases, as well as the regulatory mechanisms that are involved in their developmental stages, which hopefully would contribute to a further understanding of OPCs and attract attention in the field of OPC biology.

Oligodendrocytes in central nervous system diseases: the effect of cytokine regulation

Cytokines including tumor necrosis factor, interleukins, interferons, and chemokines are abundantly produced in various diseases. As pleiotropic factors, cytokines are involved in nearly every aspect of cellular functions such as migration, survival, proliferation, and differentiation. Oligodendrocytes are the myelin-forming cells in the central nervous system and play critical roles in the conduction of action potentials, supply of metabolic components for axons, and other functions. Emerging evidence suggests that both oligodendrocytes and oligodendrocyte precursor cells are vulnerable to cytokines released under pathological conditions. This review mainly summarizes the effects of cytokines on oligodendrocyte lineage cells in central nervous system diseases. A comprehensive understanding of the effects of cytokines on oligodendrocyte lineage cells contributes to our understanding of central nervous system diseases and offers insights into treatment strategies.

Zinc-Finger Protein ZFP488 Regulates the Timing of Oligodendrocyte Myelination and Remyelination

Oligodendrocyte myelination and remyelination after injury are intricately regulated by various intrinsic and extrinsic factors, including transcriptional regulators. Among these, the zinc-finger protein ZFP488 is an oligodendrocyte-enriched transcriptional regulator that promotes oligodendrocyte differentiation in the developing neural tube and in oligodendroglial cell lines. However, the specific in vivo genetic requirements for ZFP488 during oligodendrocyte development and remyelination have not been defined. To address this gap, we generated a lineage-traceable ZFP488 knock-out mouse line, wherein an H2b-GFP reporter replaces the ZFP488-coding region. Using these mice of either sex, we examined the dynamics of ZFP488 expression from the endogenous promoter in the developing central nervous system (CNS). We observed a unique expression pattern in the oligodendrocyte lineage, with ZFP488 expression particularly enriched in differentiated oligodendrocytes. ZFP488 loss resulted in delayed myelination in the developing CNS and impaired remyelination after demyelinating injury in the brain. Integrated transcriptomic and genomic profiling further revealed that ZFP488 loss decreased the expression of myelination-associated genes but not oligodendrocyte progenitor-associated genes, suggesting that ZFP488 serves as a positive regulator of myelination by regulating maturation programs. Thus, our genetic loss-of-function study revealed that ZFP488 regulates a stage-dependent differentiation program that controls the timing of CNS myelination and remyelination.

CelltypeR: A flow cytometry pipeline to characterize single cells from brain organoids

Motivated by the cellular heterogeneity in complex tissues, particularly in brain and induced pluripotent stem cell (iPSC)-derived brain models, we developed a complete workflow to reproducibly characterize cell types in complex tissues. Our approach combines a flow cytometry (FC) antibody panel with our computational pipeline CelltypeR, enabling dataset aligning, unsupervised clustering optimization, cell type annotating, and statistical comparisons. Applied to human iPSC derived midbrain organoids, it successfully identified the major brain cell types. We performed fluorescence-activated cell sorting of CelltypeR-defined astrocytes, radial glia, and neurons, exploring transcriptional states by single-cell RNA sequencing. Among the sorted neurons, we identified subgroups of dopamine neurons: one reminiscent of substantia nigra cells most vulnerable in Parkinson's disease. Finally, we used our workflow to track cell types across a time course of organoid differentiation. Overall, our adaptable analysis framework provides a generalizable method for reproducibly identifying cell types across FC datasets in complex tissues.

Astrocyte allocation during brain development is controlled by Tcf4-mediated fate restriction

Astrocytes in the brain exhibit regional heterogeneity contributing to regional circuits involved in higher-order brain functions, yet the mechanisms controlling their distribution remain unclear. Here, we show that the precise allocation of astrocytes to specific brain regions during development is achieved through transcription factor 4 (Tcf4)-mediated fate restriction based on their embryonic origin. Loss of Tcf4 in ventral telencephalic neural progenitor cells alters the fate of oligodendrocyte precursor cells to transient intermediate astrocyte precursor cells, resulting in mislocalized astrocytes in the dorsal neocortex. These ectopic astrocytes engage with neocortical neurons and acquire features reminiscent of dorsal neocortical astrocytes. Furthermore, Tcf4 functions as a suppressor of astrocyte fate during the differentiation of oligodendrocyte precursor cells derived from the ventral telencephalon, thereby restricting the fate to the oligodendrocyte lineage in the dorsal neocortex. Together, our findings highlight a previously unappreciated role for Tcf4 in regulating astrocyte allocation, offering additional insights into the mechanisms underlying neurodevelopmental disorders linked to Tcf4 mutations.

DOR activation in mature oligodendrocytes regulates α-ketoglutarate metabolism leading to enhanced remyelination in aged mice

The decreased ability of mature oligodendrocytes to produce myelin negatively affects remyelination in demyelinating diseases and aging, but the underlying mechanisms are incompletely understood. In the present study, we identify a mature oligodendrocyte-enriched transcriptional coregulator diabetes- and obesity-related gene (DOR)/tumor protein p53-inducible nuclear protein 2 (TP53INP2), downregulated in demyelinated lesions of donors with multiple sclerosis and in aged oligodendrocyte-lineage cells. Dor ablation in mice of both sexes results in defective myelinogenesis and remyelination. Genomic occupancy in oligodendrocytes and transcriptome profiling of the optic nerves of wild-type and Dor conditional knockout mice reveal that DOR and SOX10 co-occupy enhancers of critical myelinogenesis-associated genes including Prr18, encoding an oligodendrocyte-enriched, proline-rich factor. We show that DOR targets regulatory elements of genes responsible for α-ketoglutarate biosynthesis in mature oligodendrocytes and is essential for α-ketoglutarate production and lipid biosynthesis. Supplementation with α-ketoglutarate restores oligodendrocyte-maturation defects in Dor-deficient adult mice and improves remyelination after lysolecithin-induced demyelination and cognitive function in 17-month-old wild-type mice. Our data suggest that activation of α-ketoglutarate metabolism in mature oligodendrocytes can promote myelin production during demyelination and aging.

The positive role of transforming growth factor-β1 in ischemic stroke

Ischemic stroke is one of the most disabling and fatal diseases around the world. The damaged brain tissues will undergo excessive autophagy, vascular endothelial cells injury, blood-brain barrier (BBB) impairment and neuroinflammation after ischemic stroke. However, there is no unified viewpoint on the underlying mechanism of brain damage. Transforming growth factor-β1 (TGF-β1), as a multi-functional cytokine, plays a crucial role in the intricate pathological processes and helps maintain the physiological homeostasis of brain tissues through various signaling pathways after ischemic stroke. In this review, we summarize the protective role of TGF-β1 in autophagic flux, BBB, vascular remodeling, neuroinflammation and other aspects after ischemic stroke. Based on the review, we believe that TGF-β1 could serve as a key target for treating ischemic stroke.

Astrogenesis in the hypothalamus: A life-long process contributing to the development and plasticity of neuroendocrine networks

Astrocytes are now recognized as integral components of neural circuits, regulating their maturation, activity and plasticity. Neuroendocrinology has provided fertile ground for revealing the diverse strategies used by astrocytes to regulate the physiological and behavioural outcomes of neural circuit activity in response to internal and environmental inputs. However, the development of astrocytes in the hypothalamus has received much less attention than in other brain regions such as the cerebral cortex and spinal cord. In this review, we synthesize our current knowledge of astrogenesis in the hypothalamus across various life stages. A distinctive feature of hypothalamic astrogenesis is that it persists all throughout lifespan, and involves multiple cellular sources corresponding to radial glial cells during early development, followed by tanycytes, parenchymal progenitors and locally dividing astrocytes. Astrogenesis in the hypothalamus is closely coordinated with the maturation of hypothalamic neurons. This coordination is exemplified by recent findings in neurons producing gonadotropin-releasing hormone, which actively shape their astroglial environment during infancy to integrate functionally into their neural network and facilitate sexual maturation, a process vulnerable to endocrine disruption. While hypothalamic astrogenesis shares common principles with other brain regions, it also exhibits specific features in its dynamics and regulation, both at the inter- and intra-regional levels. These unique properties emphasize the importance of further exploration. Additionally, we discuss the experimental strategies used to assess astrogenesis in the hypothalamus and their potential bias and limitations. Understanding the mechanisms of hypothalamic astrogenesis throughout life will be crucial for comprehending the development and function of the hypothalamus under both physiological and pathological conditions.

Transcription Factors Sox8 and Sox10 Contribute with Different Importance to the Maintenance of Mature Oligodendrocytes

Myelin-forming oligodendrocytes in the vertebrate nervous system co-express the transcription factor Sox10 and its paralog Sox8. While Sox10 plays crucial roles throughout all stages of oligodendrocyte development, including terminal differentiation, the loss of Sox8 results in only mild and transient perturbations. Here, we aimed to elucidate the roles and interrelationships of these transcription factors in fully differentiated oligodendrocytes and myelin maintenance in adults. For that purpose, we conducted targeted deletions of Sox10, Sox8, or both in the brains of two-month-old mice. Three weeks post-deletion, none of the resulting mouse mutants exhibited significant alterations in oligodendrocyte numbers, myelin sheath counts, myelin ultrastructure, or myelin protein levels in the corpus callosum, despite efficient gene inactivation. However, differences were observed in the myelin gene expression in mice with Sox10 or combined Sox8/Sox10 deletion. RNA-sequencing analysis on dissected corpus callosum confirmed substantial alterations in the oligodendrocyte expression profile in mice with combined deletion and more subtle changes in mice with Sox10 deletion alone. Notably, Sox8 deletion did not affect any aspects of the expression profile related to the differentiated state of oligodendrocytes or myelin integrity. These findings extend our understanding of the roles of Sox8 and Sox10 in oligodendrocytes into adulthood and have important implications for the functional relationship between the paralogs and the underlying molecular mechanisms.

Targeted DeSUMOylation as a therapeutic strategy for multiple sclerosis

SUMO (small ubiquitin like modifier) conjugated proteins have emerged as an important post translational modifier of cellular function. SUMOylation modulates several cellular processes involved in transcriptional regulation of genes, protein-protein interactions and DNA damage and repair. Since abnormalities in SUMOylation has been observed in neoplastic and neurodegenerative disorders, the SUMO pathway has become an attractive site for targeting of new therapies to regulate SUMOylation and reduce disease burden. Conjugation of SUMO to their respective substrates is orchestrated by an enzymatic cascade involving three main enzymes, E1, activation enzyme, E2, conjugating enzyme and E3, a protein ligase. Each of these enzymes are therefore potential "druggable" sites for future therapeutics. SUMOylation is a well-known mechanism by which the innate immune response is regulated in response to viral infections and in the adaptive immune response to tumor immunity. We have shown that small molecules which inhibit the SUMO activation pathway are also capable of inhibiting autoimmune response. TAK981 which forms adducts with SUMO and anacardic acid which inhibits the E1 enzyme of the SUMO pathway were effective in preventing the development of experimental allergic encephalitis (EAE), a mouse model of multiple sclerosis. Anacardic acid and TAK981 inhibited activation of TH17 cells and reduced clinical and pathological injury in IL-17 mediated myelin oligodendrocyte glycoprotein (MOG) induced EAE. Ginkgolic acid, another known inhibitor of SUMO pathway, was also shown to be effective in reducing the severity of inflammatory arthropathies which is also IL-17 mediated. In addition, the increase in the transcription of myelin genes with TAK981 and anacardic acid improved remyelination in experimental models of demyelination. In the present review paper, we examine the mechanism of action of inhibitors of the SUMO pathway on regulating the immune response and the possibility of the use of these agents as therapeutics for MS.

LY2940094, an NOPR antagonist, promotes oligodendrocyte generation and myelin recovery in an NOPR independent manner

The myelin sheath plays crucial roles in brain development and neuronal functions. In the central nervous system, myelin is generated by oligodendrocytes, that differentiate from oligodendrocyte progenitor cells (OPC). In demyelinating diseases, the differentiation capacity of OPC is impaired and remyelination is dampened. Boosting remyelination by promoting OPC differentiation is a novel strategy for the treatment of demyelinating diseases. The opioid system, which consists of four receptors and their ligands, has been implicated in OPC differentiation and myelin formation. However, the exact roles of each opioid receptor and the relevant pharmacological molecules in OPC differentiation and myelin formation remain elusive. In the present study, specific agonists and antagonists of each opioid receptor were used to explore the function of opioid receptors in OPC differentiation. Nociceptin/orphanin FQ receptor (NOPR) specific antagonist LY2940094 was found to stimulate OPC differentiation and myelination in both in vitro and in vivo models. Unexpectedly, other NOPR ligands did not affect OPC differentiation, and NOPR knockdown did not mimic or impede the effect of LY2940094. LY2940094 was found to modulate the expression of the oligodendrocytes differentiation-associated transcription factors ID4 and Myrf, although the exact mechanism remains unclear. Since LY2940094 has been tested clinically to treat depression and alcohol dependency and has displayed an acceptable safety profile, it may provide an alternative approach to treat demyelinating diseases.

Single-cell and Spatial Transcriptomics Reveals Ferroptosis as The Most Enriched Programmed Cell Death Process in Hemorrhage Stroke-induced Oligodendrocyte-mediated White Matter Injury

Intracerebral hemorrhage (ICH) is a severe stroke subtype with limited therapeutic options. Programmed cell death (PCD) is crucial for immunological balance, and includes necroptosis, pyroptosis, apoptosis, ferroptosis, and necrosis. However, the distinctions between these programmed cell death modalities after ICH remain to be further investigated. We used single-cell transcriptome (single-cell RNA sequencing) and spatial transcriptome (spatial RNA sequencing) techniques to investigate PCD-related gene expression trends in the rat brain following hemorrhagic stroke. Ferroptosis was the main PCD process after ICH, and primarily affected mature oligodendrocytes. Its onset occurred as early as 1 hour post-ICH, peaking at 24 hours post-ICH. Additionally, ferroptosis-related genes were distributed in the hippocampus and choroid plexus. We also elucidated a specific interaction between lipocalin-2 (LCN2)-positive microglia and oligodendrocytes that was mediated by the colony stimulating factor 1 (CSF1)/CSF1 receptor pathway, leading to ferroptosis induction in oligodendrocytes and subsequent neurological deficits. In conclusion, our study highlights ferroptosis as the primary PCD mechanism, emerging as early as 1 hour post-ICH. Early therapeutic intervention via the suppression of microglial LCN2 expression may alleviate ferroptosis-induced damage in oligodendrocytes and associated neurological deficits, thus offering a promising neuroprotective strategy following ICH.

The combined administration of LNC-encapsulated retinoic acid and calcitriol stimulates oligodendrocyte progenitor cell differentiation in vitro and in vivo after intranasal administration

Intranasal administration is an efficient strategy for bypassing the BBB, favoring drug accumulation in the brain, and improving its efficiency. Lipid nanocapsules (LNC) are suitable nanocarriers for the delivery of lipophilic drugs via this route and can be used to encapsulate lipophilic molecules such as retinoic acid (RA) and calcitriol (Cal). As the hallmarks of multiple sclerosis (MS) are neuroinflammation and oligodendrocyte loss, our hypothesis was that by combining two molecules known for their pro-differentiating properties, encapsulated in LNC, and delivered by intranasal administration, we would stimulate oligodendrocyte progenitor cells (OPC) differentiation into oligodendrocytes and provide a new pro-remyelinating therapy. LNC loaded with RA (LNC-RA) and Cal (LNC-Cal) were stable for at least 8 weeks. The combination of RA and Cal was more efficient than the molecules alone, encapsulated or not, on OPC differentiation in vitro and decreased microglia cell activation in a dose-dependent manner. After the combined intranasal administration of LNC-RA and LNC-Cal in a mouse cuprizone model of demyelination, increased MBP staining was observed in the corpus callosum. In conclusion, intranasal delivery of lipophilic drugs encapsulated in LNC is a promising strategy for myelinating therapies.

Single-cell multi-omics analysis reveals cooperative transcription factors for gene regulation in oligodendrocytes

Oligodendrocytes are the myelinating cells within the central nervous system. Many oligodendrocyte genes have been associated with brain disorders. However, how transcription factors (TFs) cooperate for gene regulation in oligodendrocytes remains largely uncharacterized. To address this, we integrated scRNA-seq and scATAC-seq data to identify the cooperative TFs that co-regulate the target gene (TG) expression in oligodendrocytes. First, we identified co- binding TF pairs whose binding sites overlapped in oligodendrocyte-specific regulatory regions. Second, we trained a deep learning model to predict the expression level of each TG using the expression levels of co-binding TFs. Third, using the trained models, we computed the TF importance and TF-TF interaction scores for predicting TG expression by the Shapley interaction scores. We found that the co-binding TF pairs involving known important TF pairs for oligodendrocyte differentiation, such as SOX10-TCF12, SOX10-MYRF, and SOX10-OLIG2, exhibited significantly higher Shapley scores than others (t-test, p-value < 1e-4). Furthermore, we identified 153 oligodendrocyte-associated eQTLs that reside in oligodendrocyte-specific enhancers or promoters where their eGenes (TGs) are regulated by cooperative TFs, suggesting potential novel regulatory roles from genetic variants. We also experimentally validated some identified TF pairs such as SOX10-OLIG2 and SOX10-NKX2.2 by co-enrichment analysis, using ChIP-seq data from rat peripheral nerve.

Oligodendrocyte Progenitors in Glial Scar: A Bet on Remyelination

Oligodendrocyte progenitor cells (OPCs) represent a subtype of glia, giving rise to oligodendrocytes, the myelin-forming cells in the central nervous system (CNS). While OPCs are highly proliferative during development, they become relatively quiescent during adulthood, when their fate is strictly influenced by the extracellular context. In traumatic injuries and chronic neurodegenerative conditions, including those of autoimmune origin, oligodendrocytes undergo apoptosis, and demyelination starts. Adult OPCs become immediately activated; they migrate at the lesion site and proliferate to replenish the damaged area, but their efficiency is hampered by the presence of a glial scar-a barrier mainly formed by reactive astrocytes, microglia and the deposition of inhibitory extracellular matrix components. If, on the one hand, a glial scar limits the lesion spreading, it also blocks tissue regeneration. Therapeutic strategies aimed at reducing astrocyte or microglia activation and shifting them toward a neuroprotective phenotype have been proposed, whereas the role of OPCs has been largely overlooked. In this review, we have considered the glial scar from the perspective of OPCs, analysing their behaviour when lesions originate and exploring the potential therapies aimed at sustaining OPCs to efficiently differentiate and promote remyelination.

Regulators of Oligodendrocyte Differentiation

Myelination has evolved as a mechanism to ensure fast and efficient propagation of nerve impulses along axons. Within the central nervous system (CNS), myelination is carried out by highly specialized glial cells, oligodendrocytes. The formation of myelin is a prolonged aspect of CNS development that occurs well into adulthood in humans, continuing throughout life in response to injury or as a component of neuroplasticity. The timing of myelination is tightly tied to the generation of oligodendrocytes through the differentiation of their committed progenitors, oligodendrocyte precursor cells (OPCs), which reside throughout the developing and adult CNS. In this article, we summarize our current understanding of some of the signals and pathways that regulate the differentiation of OPCs, and thus the myelination of CNS axons.

Targeting of KOR by famotidine promotes OPC maturation differentiation and CNS remyelination via STAT3 signaling pathway

This study aims to identify FDA-approved drugs that can target the kappa-opioid receptor (KOR) for the treatment of demyelinating diseases. Demyelinating diseases are characterized by myelin sheath destruction or formation that results in severe neurological dysfunction. Remission of this disease is largely dependent on the differentiation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes (OLGs) in demyelinating lesions. KOR is an important regulatory protein and drug target for the treatment of demyelinating diseases. However, no drug targeting KOR has been developed due to the long clinical trials for drug discovery. Here, a structure-based virtual screening was applied to identify drugs targeting KOR among 1843 drugs of FDA-approved drug libraries, and famotidine was screen out by its high affinity cooperation with KOR as well as the clinical safety. We discovered that famotidine directly promoted OPC maturation and remyelination using the complementary in vitro and in vivo models. Administration of famotidine was not only effectively enhanced CNS myelinogenesis, but also promoted remyelination. Mechanically speaking, famotidine promoted myelinogenesis or remyelination through KOR/STAT3 signaling pathway. In general, our study provided evidence of new clinical applicability of famotidine for the treatment of demyelinating diseases for which there is currently no effective therapy.

Spatial omics reveals molecular changes in focal cortical dysplasia type II

Focal cortical dysplasia (FCD) represents a group of diverse localized cortical lesions that are highly epileptogenic and occur due to abnormal brain development caused by genetic mutations, involving the mammalian target of rapamycin (mTOR). These somatic mutations lead to mosaicism in the affected brain, posing challenges to unravel the direct and indirect functional consequences of these mutations. To comprehensively characterize the impact of mTOR mutations on the brain, we employed here a multimodal approach in a preclinical mouse model of FCD type II (Rheb), focusing on spatial omics techniques to define the proteomic and lipidomic changes. Mass Spectrometry Imaging (MSI) combined with fluorescence imaging and label free proteomics, revealed insight into the brain's lipidome and proteome within the FCD type II affected region in the mouse model. MSI visualized disrupted neuronal migration and differential lipid distribution including a reduction in sulfatides in the FCD type II-affected region, which play a role in brain myelination. MSI-guided laser capture microdissection (LMD) was conducted on FCD type II and control regions, followed by label free proteomics, revealing changes in myelination pathways by oligodendrocytes. Surgical resections of FCD type IIb and postmortem human cortex were analyzed by bulk transcriptomics to unravel the interplay between genetic mutations and molecular changes in FCD type II. Our comparative analysis of protein pathways and enriched Gene Ontology pathways related to myelination in the FCD type II-affected mouse model and human FCD type IIb transcriptomics highlights the animal model's translational value. This dual approach, including mouse model proteomics and human transcriptomics strengthens our understanding of the functional consequences arising from somatic mutations in FCD type II, as well as the identification of pathways that may be used as therapeutic strategies in the future.

Transcription Factors Sox2 and Sox3 Directly Regulate the Expression of Genes Involved in the Onset of Oligodendrocyte Differentiation

Rapid information processing in the central nervous system requires the myelination of axons by oligodendrocytes. The transcription factor Sox2 and its close relative Sox3 redundantly regulate the development of myelin-forming oligodendrocytes, but little is known about the underlying molecular mechanisms. Here, we characterized the expression profile of cultured oligodendroglial cells during early differentiation and identified Bcas1, Enpp6, Zfp488 and Nkx2.2 as major downregulated genes upon Sox2 and Sox3 deletion. An analysis of mice with oligodendrocyte-specific deletion of Sox2 and Sox3 validated all four genes as downstream targets in vivo. Additional functional assays identified regulatory regions in the vicinity of each gene that are responsive to and bind both Sox proteins. Bcas1, Enpp6, Zfp488 and Nkx2.2 therefore likely represent direct target genes and major effectors of Sox2 and Sox3. Considering the preferential expression and role of these genes in premyelinating oligodendrocytes, our findings suggest that Sox2 and Sox3 impact oligodendroglial development at the premyelinating stage with Bcas1, Enpp6, Zfp488 and Nkx2.2 as their major effectors.

General anesthetic agents induce neurotoxicity through oligodendrocytes in the developing brain

General anesthetic agents can impact brain function through interactions with neurons and their effects on glial cells. Oligodendrocytes perform essential roles in the central nervous system, including myelin sheath formation, axonal metabolism, and neuroplasticity regulation. They are particularly vulnerable to the effects of general anesthetic agents resulting in impaired proliferation, differentiation, and apoptosis. Neurologists are increasingly interested in the effects of general anesthetic agents on oligodendrocytes. These agents not only act on the surface receptors of oligodendrocytes to elicit neuroinflammation through modulation of signaling pathways, but also disrupt metabolic processes and alter the expression of genes involved in oligodendrocyte development and function. In this review, we summarize the effects of general anesthetic agents on oligodendrocytes. We anticipate that future research will continue to explore these effects and develop strategies to decrease the incidence of adverse reactions associated with the use of general anesthetic agents.

Small-molecule-induced epigenetic rejuvenation promotes SREBP condensation and overcomes barriers to CNS myelin regeneration

Remyelination failure in diseases like multiple sclerosis (MS) was thought to involve suppressed maturation of oligodendrocyte precursors; however, oligodendrocytes are present in MS lesions yet lack myelin production. We found that oligodendrocytes in the lesions are epigenetically silenced. Developing a transgenic reporter labeling differentiated oligodendrocytes for phenotypic screening, we identified a small-molecule epigenetic-silencing-inhibitor (ESI1) that enhances myelin production and ensheathment. ESI1 promotes remyelination in animal models of demyelination and enables de novo myelinogenesis on regenerated CNS axons. ESI1 treatment lengthened myelin sheaths in human iPSC-derived organoids and augmented (re)myelination in aged mice while reversing age-related cognitive decline. Multi-omics revealed that ESI1 induces an active chromatin landscape that activates myelinogenic pathways and reprograms metabolism. Notably, ESI1 triggered nuclear condensate formation of master lipid-metabolic regulators SREBP1/2, concentrating transcriptional co-activators to drive lipid/cholesterol biosynthesis. Our study highlights the potential of targeting epigenetic silencing to enable CNS myelin regeneration in demyelinating diseases and aging.

Genetic background modulates the effect of glucocorticoids on proliferation, differentiation and myelin formation of oligodendrocyte lineage cells

Anxiety disorders are prevalent mental disorders. Their predisposition involves a combination of genetic and environmental risk factors, such as psychosocial stress. Myelin plasticity was recently associated with chronic stress in several mouse models. Furthermore, we found that changes in both myelin thickness and node of Ranvier morphology after chronic social defeat stress are influenced by the genetic background of the mouse strain. To understand cellular and molecular effects of stress-associated myelin plasticity, we established an oligodendrocyte (OL) model consisting of OL primary cell cultures isolated from the C57BL/6NCrl (B6; innately non-anxious and mostly stress-resilient strain) and DBA/2NCrl (D2; innately anxious and mostly stress-susceptible strain) mice. Characterization of naïve cells revealed that D2 cultures contained more pre-myelinating and mature OLs compared with B6 cultures. However, B6 cultures contained more proliferating oligodendrocyte progenitor cells (OPCs) than D2 cultures. Acute exposure to corticosterone, the major stress hormone in mice, reduced OPC proliferation and increased OL maturation and myelin production in D2 cultures compared with vehicle treatment, whereas only OL maturation was reduced in B6 cultures. In contrast, prolonged exposure to the synthetic glucocorticoid dexamethasone reduced OPC proliferation in both D2 and B6 cultures, but only D2 cultures displayed a reduction in OPC differentiation and myelin production. Taken together, our results reveal that genetic factors influence OL sensitivity to glucocorticoids, and this effect is dependent on the cellular maturation stage. Our model provides a novel framework for the identification of cellular and molecular mechanisms underlying stress-associated myelin plasticity.

Developmental trajectories of GABAergic cortical interneurons are sequentially modulated by dynamic FoxG1 expression levels

GABAergic inhibitory interneurons, originating from the embryonic ventral forebrain territories, traverse a convoluted migratory path to reach the neocortex. These interneuron precursors undergo sequential phases of tangential and radial migration before settling into specific laminae during differentiation. Here, we show that the developmental trajectory of FoxG1 expression is dynamically controlled in these interneuron precursors at critical junctures of migration. By utilizing mouse genetic strategies, we elucidate the pivotal role of precise changes in FoxG1 expression levels during interneuron specification and migration. Our findings underscore the gene dosage-dependent function of FoxG1, aligning with clinical observations of FOXG1 haploinsufficiency and duplication in syndromic forms of autism spectrum disorders. In conclusion, our results reveal the finely tuned developmental clock governing cortical interneuron development, driven by temporal dynamics and the dose-dependent actions of FoxG1.

MYRF: A unique transmembrane transcription factor- from proteolytic self-processing to its multifaceted roles in animal development

The Myelin Regulator Factor (MYRF) is a master regulator governing myelin formation and maintenance in the central nervous system. The conservation of MYRF across metazoans and its broad tissue expression suggest it has functions extending beyond the well-established role in myelination. Loss of MYRF results in developmental lethality in both invertebrates and vertebrates, and MYRF haploinsufficiency in humans causes MYRF-related Cardiac Urogenital Syndrome, underscoring its importance in animal development; however, these mechanisms are largely unexplored. MYRF, an unconventional transcription factor, begins embedded in the membrane and undergoes intramolecular chaperone mediated trimerization, which triggers self-cleavage, allowing its N-terminal segment with an Ig-fold DNA-binding domain to enter the nucleus for transcriptional regulation. Recent research suggests developmental regulation of cleavage, yet the mechanisms remain enigmatic. While some parts of MYRF's structure have been elucidated, others remain obscure, leaving questions about how these motifs are linked to its intricate processing and function.

Tackling myelin deficits in neurodevelopmental disorders using drug delivery systems

Interest in myelin and its roles in almost all brain functions has been greatly increasing in recent years, leading to countless new studies on myelination, as a dominant process in the development of cognitive functions. Here, we explore the unique role myelin plays in the central nervous system and specifically discuss the results of altered myelination in neurodevelopmental disorders. We present parallel developmental trajectories involving myelination that correlate with the onset of cognitive impairment in neurodevelopmental disorders and discuss the key challenges in the treatment of these chronic disorders. Recent developments in drug repurposing and nano/micro particle-based therapies are reviewed as a possible pathway to circumvent some of the main hurdles associated with early intervention, including patient's adherence and compliance, side effects, relapse, and faster route to possible treatment of these disorders. The strategy of drug encapsulation overcomes drug solubility and metabolism, with the possibility of drug targeting to a specific compartment, reducing side effects upon systemic administration.

Clinical phenotype and genetic function analysis of a family with hypomyelinating leukodystrophy-7 caused by POLR3A mutation

Hypomyelinating leukodystrophy (HLD) is a rare genetic heterogeneous disease that can affect myelin development in the central nervous system. This study aims to analyze the clinical phenotype and genetic function of a family with HLD-7 caused by POLR3A mutation. The proband (IV6) in this family mainly showed progressive cognitive decline, dentin dysplasia, and hypogonadotropic hypogonadism. Her three old brothers (IV1, IV2, and IV4) also had different degrees of ataxia, dystonia, or dysarthria besides the aforementioned manifestations. Their brain magnetic resonance imaging showed bilateral periventricular white matter atrophy, brain atrophy, and corpus callosum atrophy and thinning. The proband and her two living brothers (IV2 and IV4) were detected to carry a homozygous mutation of the POLR3A (NM_007055.4) gene c. 2300G > T (p.Cys767Phe), and her consanguineous married parents (III1 and III2) were p.Cys767Phe heterozygous carriers. In the constructed POLR3A wild-type and p.Cys767Phe mutant cells, it was seen that overexpression of wild-type POLR3A protein significantly enhanced Pol III transcription of 5S rRNA and tRNA Leu-CAA. However, although the mutant POLR3A protein overexpression was increased compared to the wild-type protein overexpression, it did not show the expected further enhancement of Pol III function. On the contrary, Pol III transcription function was frustrated (POLR3A, BC200, and tRNA Leu-CAA expression decreased), and MBP and 18S rRNA expressions were decreased. This study indicates that the POLR3A p.Cys767Phe variant caused increased expression of mutated POLR3A protein and abnormal expression of Pol III transcripts, and the mutant POLR3A protein function was abnormal.

The role of TSC1 and TSC2 proteins in neuronal axons

Tuberous Sclerosis Complex 1 and 2 proteins, TSC1 and TSC2 respectively, participate in a multiprotein complex with a crucial role for the proper development and function of the nervous system. This complex primarily acts as an inhibitor of the mechanistic target of rapamycin (mTOR) kinase, and mutations in either TSC1 or TSC2 cause a neurodevelopmental disorder called Tuberous Sclerosis Complex (TSC). Neurological manifestations of TSC include brain lesions, epilepsy, autism, and intellectual disability. On the cellular level, the TSC/mTOR signaling axis regulates multiple anabolic and catabolic processes, but it is not clear how these processes contribute to specific neurologic phenotypes. Hence, several studies have aimed to elucidate the role of this signaling pathway in neurons. Of particular interest are axons, as axonal defects are associated with severe neurocognitive impairments. Here, we review findings regarding the role of the TSC1/2 protein complex in axons. Specifically, we will discuss how TSC1/2 canonical and non-canonical functions contribute to the formation and integrity of axonal structure and function.

PRRC2B modulates oligodendrocyte progenitor cell development and myelination by stabilizing Sox2 mRNA

Oligodendrocyte progenitor cells (OPCs) differentiate into myelin-producing cells and modulate neuronal activity. Defects in OPC development are associated with neurological diseases. N6-methyladenosine (m6A) contributes to neural development; however, the mechanism by which m6A regulates OPC development remains unclear. Here, we demonstrate that PRRC2B is an m6A reader that regulates OPC development and myelination. Nestin-Cre-mediated Prrc2b deletion affects neural stem cell self-renewal and glial differentiation. Moreover, the oligodendroglia lineage-specific deletion of Prrc2b reduces the numbers of OPCs and oligodendrocytes, causing hypomyelination and impaired motor coordination. Integrative methylated RNA immunoprecipitation sequencing, RNA sequencing, and RNA immunoprecipitation sequencing analyses identify Sox2 as the target of PRRC2B. Notably, PRRC2B, displaying separate and cooperative functions with PRRC2A, stabilizes mRNA by binding to m6A motifs in the coding sequence and 3' UTR of Sox2. In summary, we identify the posttranscriptional regulation of PRRC2B in OPC development, extending the understanding of PRRC2 family proteins and providing a therapeutic target for myelin-related disorders.

Recognizing Alzheimer's disease from perspective of oligodendrocytes: Phenomena or pathogenesis?

BACKGROUND

Accumulation of amyloid beta, tau hyperphosphorylation, and microglia activation are the three highly acknowledged pathological factors of Alzheimer's disease (AD). However, oligodendrocytes (OLs) were also widely investigated in the pathogenesis and treatment for AD.

AIMS

We aimed to update the regulatory targets of the differentiation and maturation of OLs, and emphasized the key role of OLs in the occurrence and treatment of AD.

METHODS

This review first concluded the targets of OL differentiation and maturation with AD pathogenesis, and then advanced the key role of OLs in the pathogenesis of AD based on both clinic and basic experiments. Later, we extensively discussed the possible application of the current progress in the diagnosis and treatment of this complex disease.

RESULTS

Molecules involving in OLs' differentiation or maturation, including various transcriptional factors, cholesterol homeostasis regulators, and microRNAs could also participate in the pathogenesis of AD. Clinical data point towards the impairment of OLs in AD patients. Basic research further supports the central role of OLs in the regulation of AD pathologies. Additionally, classic drugs, including donepezil, edaravone, fluoxetine, and clemastine demonstrate their potential in remedying OL impairment in AD models, and new therapeutics from the perspective of OLs is constantly being developed.

CONCLUSIONS

We believe that OL dysfunction is one important pathogenesis of AD. Factors regulating OLs might be biomarkers for early diagnosis and agents stimulating OLs warrant the development of anti-AD drugs.

Massively parallel disruption of enhancers active in human neural stem cells

Changes in gene regulation have been linked to the expansion of the human cerebral cortex and to neurodevelopmental disorders, potentially by altering neural progenitor proliferation. However, the effects of genetic variation within regulatory elements on neural progenitors remain obscure. We use sgRNA-Cas9 screens in human neural stem cells (hNSCs) to disrupt 10,674 genes and 26,385 conserved regions in 2,227 enhancers active in the developing human cortex and determine effects on proliferation. Genes with proliferation phenotypes are associated with neurodevelopmental disorders and show biased expression in specific fetal human brain neural progenitor populations. Although enhancer disruptions overall have weaker effects than gene disruptions, we identify enhancer disruptions that severely alter hNSC self-renewal. Disruptions in human accelerated regions, implicated in human brain evolution, also alter proliferation. Integrating proliferation phenotypes with chromatin interactions reveals regulatory relationships between enhancers and their target genes contributing to neurogenesis and potentially to human cortical evolution.

RNF220-mediated K63-linked polyubiquitination stabilizes Olig proteins during oligodendroglial development and myelination

Maldevelopment of oligodendroglia underlies neural developmental disorders such as leukodystrophy. Precise regulation of the activity of specific transcription factors (TFs) by various posttranslational modifications (PTMs) is required to ensure proper oligodendroglial development and myelination. However, the role of ubiquitination of these TFs during oligodendroglial development is yet unexplored. Here, we find that RNF220, a known leukodystrophy-related E3 ubiquitin ligase, is required for oligodendroglial development. RNF220 depletion in oligodendrocyte lineage cells impedes oligodendrocyte progenitor cell proliferation, differentiation, and (re)myelination, which consequently leads to learning and memory defects. Mechanistically, RNF220 targets Olig1/2 for K63-linked polyubiquitination and stabilization during oligodendroglial development. Furthermore, in a knock-in mouse model of leukodystrophy-related RNF220R365Q mutation, the ubiquitination and stabilization of Olig proteins are deregulated in oligodendroglial cells. This results in pathomimetic oligodendroglial developmental defects, impaired myelination, and abnormal behaviors. Together, our evidence provides an alternative insight into PTMs of oligodendroglial TFs and how this essential process may be implicated in the etiology of leukodystrophy.

Hypoxic postconditioning drives protective microglial responses and ameliorates white matter injury after ischemic stroke

BACKGROUND

Ischemic stroke (IS) is a cerebrovascular disease with high incidence and mortality. White matter repair plays an important role in the long-term recovery of neurological function after cerebral ischemia. Neuroprotective microglial responses can promote white matter repair and protect ischemic brain tissue.

AIMS

The aim of this study was to investigate whether hypoxic postconditioning (HPC) can promote white matter repair after IS, and the role and mechanism of microglial polarization in white matter repair after HPC treatment.

MATERIALS & METHODS

Adult male C57/BL6 mice were randomly divided into three groups: Sham group (Sham), MCAO group (MCAO), and hypoxic postconditioning group (HPC). HPC group were subjected to 45 min of transient middle cerebral artery occlusion (MCAO) immediately followed by 40 min of HPC.

RESULTS

The results showed that HPC reduced the proinflammatory level of immune cells. Furthermore, HPC promoted the transformation of microglia to anti-inflammatory phenotype on the third day after the procedure. HPC promoted the proliferation of oligodendrocyte progenitors and increased the expression of myelination-related proteins on the 14th day. On the 28th day, HPC increased the expression of mature oligodendrocytes, which enhanced myelination. At the same time, the motor neurological function of mice was restored.

DISCUSSION

During the acute phase of cerebral ischemia, the function of proinflammatory immune cells was enhanced, long-term white matter damage was aggravated, and motor sensory function was decreased.

CONCLUSION

HPC promotes protective microglial responses and white matter repair after MCAO, which may be related to the proliferation and differentiation of oligodendrocytes.

Single-nucleus transcriptomic analysis reveals the relationship between gene expression in oligodendrocyte lineage and major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is a common mental illness that affects millions of people worldwide and imposes a heavy burden on individuals, families and society. Previous studies on MDD predominantly focused on neurons and employed bulk homogenates of brain tissues. This paper aims to decipher the relationship between oligodendrocyte lineage (OL) development and MDD at the single-cell resolution level.

METHODS

Here, we present the use of a guided regularized random forest (GRRF) algorithm to explore single-nucleus RNA sequencing profiles (GSE144136) of the OL at four developmental stages, which contains dorsolateral prefrontal cortex of 17 healthy controls (HC) and 17 MDD cases, generated by Nagy C et al. We prioritized and ordered differentially expressed genes (DEGs) based on Nagy et al., which could predominantly discriminate cells in the four developmental stages and two adjacent developmental stages of the OL. We further screened top-ranked genes that distinguished between HC and MDD in four developmental stages. Moreover, we estimated the performance of the GRRF model via the area under the curve value. Additionally, we validated the pivotal candidate gene Malat1 in animal models.

RESULTS

We found that, among the four developmental stages, the onset development of OL (OPC2) possesses the best predictive power for distinguishing HC and MDD, and long noncoding RNA MALAT1 has top-ranked importance value in candidate genes of four developmental stages. In addition, results of fluorescence in situ hybridization assay showed that Malat1 plays a critical role in the occurrence of depression.

CONCLUSIONS

Our work elucidates the mechanism of MDD from the perspective of OL development at the single-cell resolution level and provides novel insight into the occurrence of depression.

The bone transcription factor Osterix controls extracellular matrix- and node of Ranvier-related gene expression in oligodendrocytes

Oligodendrocytes are the primary producers of many extracellular matrix (ECM)-related proteins found in the CNS. Therefore, oligodendrocytes play a critical role in the determination of brain stiffness, node of Ranvier formation, perinodal ECM deposition, and perineuronal net formation, all of which depend on the ECM. Nevertheless, the transcription factors that control ECM-related gene expression in oligodendrocytes remain unknown. Here, we found that the transcription factor Osterix (also known as Sp7) binds in proximity to genes important for CNS ECM and node of Ranvier formation and mediates their expression. Oligodendrocyte-specific ablation of Sp7 changes ECM composition and brain stiffness and results in aberrant node of Ranvier formation. Sp7 is known to control osteoblast maturation and bone formation. Our comparative analyses suggest that Sp7 plays a conserved biological role in oligodendrocytes and in bone-forming cells, where it mediates brain and bone tissue stiffness by controlling expression of ECM components.

Identification of Molecular Correlations of GSDMD with Pyroptosis inAlzheimer's Disease

AIM

An analysis of bioinformatics and cell experiments was performed to verify the relationship between gasdermin D (GSDMD), an executive protein of pyroptosis, and Alzheimer's disease (AD).

METHODS

The training set GSE33000 was utilized to identify differentially expressed genes (DEGs) in both the AD group and control group, as well as in the GSDMD protein high/low expression group. Subsequently, the weighted gene co-expression network analysis (WGCNA) and the least absolute shrinkage and selection operator (LASSO) regression analysis were conducted, followed by the selection of the key genes for the subsequent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. The association between GSDMD and AD was assessed and confirmed in the training set GSE33000, as well as in the validation sets GSE5281 and GSE48350. Immunofluorescence (IF) was employed to detect the myelin basic protein (MBP), a distinctive protein found in the rat oligodendrocytes (OLN-93 cells). A range of concentrations (1-15 μmol/L) of β-amyloid 1-42 (Aβ1-42) were exposed to the cells, and the subsequent observations were made regarding cell morphology. Additionally, the assessments were conducted to evaluate the cell viability, the lactate dehydrogenase (LDH) release, the cell membrane permeability, and the GSDMD protein expression.

RESULTS

A total of 7,492 DEGs were screened using GSE33000. Subsequently, WGCNA analysis identified 19 genes that exhibited the strongest correlation with clinical traits in AD. Additionally, LASSO regression analysis identified 13 key genes, including GSDMD, AFF1, and ATOH8. Furthermore, the investigation revealed that the key genes were associated with cellular inflammation based on GO and KEGG analyses. Moreover, the area under the curve (AUC) values for the key genes in the training and validation sets were determined to be 0.95 and 0.70, respectively. Significantly, GSDMD demonstrated elevated levels of expression in AD across both datasets. The positivity of MBP expression in cells exceeded 95%. As the concentration of Aβ1-42 action gradually escalated, the detrimental effects on cells progressively intensified, resulting in a gradual decline in cell survival rate, accompanied by an increase in lactate dehydrogenase release, cell membrane permeability, and GSDMD protein expression.

CONCLUSION

The association between GSDMD and AD has been observed, and it has been found that Aβ1-42 can induce a significant upregulation of GSDMD in OLN-93 cells. This suggests that Aβ1-42 has the potential to induce cellular pyroptosis and can serve as a valuable cellular pyroptosis model for the study of AD.

EAAT3 impedes oligodendrocyte remyelination in chronic cerebral hypoperfusion-induced white matter injury

BACKGROUND

Chronic cerebral hypoperfusion-induced demyelination causes progressive white matter injury, although the pathogenic pathways are unknown.

METHODS

The Single Cell Portal and PanglaoDB databases were used to analyze single-cell RNA sequencing experiments to determine the pattern of EAAT3 expression in CNS cells. Immunofluorescence (IF) was used to detect EAAT3 expression in oligodendrocytes and oligodendrocyte progenitor cells (OPCs). EAAT3 levels in mouse brains were measured using a western blot at various phases of development, as well as in traumatic brain injury (TBI) and intracerebral hemorrhage (ICH) mouse models. The mouse bilateral carotid artery stenosis (BCAS) model was used to create white matter injury. IF, Luxol Fast Blue staining, and electron microscopy were used to investigate the effect of remyelination. 5-Ethynyl-2-Deoxy Uridine staining, transwell chamber assays, and IF were used to examine the effects of OPCs' proliferation, migration, and differentiation in vivo and in vitro. The novel object recognition test, the Y-maze test, the rotarod test, and the grid walking test were used to examine the impact of behavioral modifications.

RESULTS

A considerable amount of EAAT3 was expressed in OPCs and mature oligodendrocytes, according to single-cell RNA sequencing data. During multiple critical phases of mouse brain development, there were no substantial changes in EAAT3 levels in the hippocampus, cerebral cortex, or white matter. Furthermore, neither the TBI nor ICH models significantly affected the levels of EAAT3 in the aforementioned brain areas. The chronic white matter injury caused by BCAS, on the other hand, resulted in a strikingly high level of EAAT3 expression in the oligodendroglia and white matter. Correspondingly, blocking EAAT3 assisted in the recovery of cognitive and motor impairment as well as the restoration of cerebral blood flow following BCAS. Furthermore, EAAT3 suppression was connected to improved OPCs' survival and proliferation in vivo as well as faster OPCs' proliferation, migration, and differentiation in vitro. Furthermore, this study revealed that the mTOR pathway is implicated in EAAT3-mediated remyelination.

CONCLUSIONS

Our findings provide the first evidence that abnormally high levels of oligodendroglial EAAT3 in chronic cerebral hypoperfusion impair OPCs' pro-remyelination actions, hence impeding white matter repair and functional recovery. EAAT3 inhibitors could be useful in the treatment of ischemia demyelination.

Novel method of isolating nuclei of human oligodendrocyte precursor cells reveals substantial developmental changes in gene expression and H3K27ac histone modification

Oligodendrocyte precursor cells (OPCs) generate differentiated mature oligodendrocytes (MOs) during development. In adult brain, OPCs replenish MOs in adaptive plasticity, neurodegenerative disorders, and after trauma. The ability of OPCs to differentiate to MOs decreases with age and is compromised in disease. Here we explored the cell specific and age-dependent differences in gene expression and H3K27ac histone mark in these two cell types. H3K27ac is indicative of active promoters and enhancers. We developed a novel flow-cytometry-based approach to isolate OPC and MO nuclei from human postmortem brain and profiled gene expression and H3K27ac in adult and infant OPCs and MOs genome-wide. In adult brain, we detected extensive H3K27ac differences between the two cell types with high concordance between gene expression and epigenetic changes. Notably, the expression of genes that distinguish MOs from OPCs appears to be under a strong regulatory control by the H3K27ac modification in MOs but not in OPCs. Comparison of gene expression and H3K27ac between infants and adults uncovered numerous developmental changes in each cell type, which were linked to several biological processes, including cell proliferation and glutamate signaling. A striking example was a subset of histone genes that were highly active in infant samples but fully lost activity in adult brain. Our findings demonstrate a considerable rearrangement of the H3K27ac landscape that occurs during the differentiation of OPCs to MOs and during postnatal development of these cell types, which aligned with changes in gene expression. The uncovered regulatory changes justify further in-depth epigenetic studies of OPCs and MOs in development and disease.

Inherited white matter disorders: Hypomyelination (myelin disorders)

Hypomyelinating leukodystrophies are a subset of genetic white matter diseases characterized by insufficient myelin deposition during development. MRI patterns are used to identify hypomyelinating disorders, and genetic testing is used to determine the causal genes implicated in individual disease forms. Clinical course can range from severe, with patients manifesting neurologic symptoms in infancy or early childhood, to mild, with onset in adolescence or adulthood. This chapter discusses the most common hypomyelinating leukodystrophies, including X-linked Pelizaeus-Merzbacher disease and other PLP1-related disorders, autosomal recessive Pelizaeus-Merzbacher-like disease, and POLR3-related leukodystrophy. PLP1-related disorders are caused by hemizygous pathogenic variants in the proteolipid protein 1 (PLP1) gene, and encompass classic Pelizaeus-Merzbacher disease, the severe connatal form, PLP1-null syndrome, spastic paraplegia type 2, and hypomyelination of early myelinating structures. Pelizaeus-Merzbacher-like disease presents a similar clinical picture to Pelizaeus-Merzbacher disease, however, it is caused by biallelic pathogenic variants in the GJC2 gene, which encodes for the gap junction protein Connexin-47. POLR3-related leukodystrophy, or 4H leukodystrophy (hypomyelination, hypodontia, and hypogonadotropic hypogonadism), is caused by biallelic pathogenic variants in genes encoding specific subunits of the transcription enzyme RNA polymerase III. In this chapter, the clinical features, disease pathophysiology and genetics, imaging patterns, as well as supportive and future therapies are discussed for each disorder.

Enhanced oxidative phosphorylation, re-organized intracellular signaling, and epigenetic de-silencing as revealed by oligodendrocyte translatome analysis after contusive spinal cord injury

Reducing the loss of oligodendrocytes (OLs) is a major goal for neuroprotection after spinal cord injury (SCI). Therefore, the OL translatome was determined in Ribotag:Plp1-CreERT2 mice at 2, 10, and 42 days after moderate contusive T9 SCI. At 2 and 42 days, mitochondrial respiration- or actin cytoskeleton/cell junction/cell adhesion mRNAs were upregulated or downregulated, respectively. The latter effect suggests myelin sheath loss/morphological simplification which is consistent with downregulation of cholesterol biosynthesis transcripts on days 10 and 42. Various regulators of pro-survival-, cell death-, and/or oxidative stress response pathways showed peak expression acutely, on day 2. Many acutely upregulated OL genes are part of the repressive SUZ12/PRC2 operon suggesting that epigenetic de-silencing contributes to SCI effects on OL gene expression. Acute OL upregulation of the iron oxidoreductase Steap3 was confirmed at the protein level and replicated in cultured OLs treated with the mitochondrial uncoupler FCCP. Hence, STEAP3 upregulation may mark mitochondrial dysfunction. Taken together, in SCI-challenged OLs, acute and subchronic enhancement of mitochondrial respiration may be driven by axonal loss and subsequent myelin sheath degeneration. Acutely, the OL switch to oxidative phosphorylation may lead to oxidative stress that is further amplified by upregulation of such enzymes as STEAP3.

Erythropoietin regulates developmental myelination in the brain stimulating postnatal oligodendrocyte maturation

Myelination is a process tightly regulated by a variety of neurotrophic factors. Here, we show-by analyzing two transgenic mouse lines, one overexpressing EPO selectively in the brain Tg21(PDGFB-rhEPO) and another with targeted removal of EPO receptors (EPORs) from oligodendrocyte progenitor cells (OPC)s (Sox10-cre;EpoRfx/fx mice)-a key function for EPO in regulating developmental brain myelination. Overexpression of EPO resulted in faster postnatal brain growth and myelination, an increased number of myelinating oligodendrocytes, faster axonal myelin ensheathment, and improved motor coordination. Conversely, targeted ablation of EPORs from OPCs reduced the number of mature oligodendrocytes and impaired motor coordination during the second postnatal week. Furthermore, we found that EPORs are transiently expressed in the subventricular zone (SVZ) during the second postnatal week and EPO increases the postnatal expression of essential oligodendrocyte pro-differentiation and pro-maturation (Nkx6.2 and Myrf) transcripts, and the Nfatc2/calcineurin pathway. In contrast, ablation of EPORs from OPCs inactivated the Erk1/2 pathway and reduced the postnatal expression of the transcripts. Our results reveal developmental time windows in which EPO therapies could be highly effective for stimulating oligodendrocyte maturation and myelination.

The committed oligodendrocyte precursor cell, a newly-defined intermediate progenitor cell type in oligodendroglial lineage

In the central nervous system, oligodendrocytes (OLs) produce myelin sheaths that provide trophic support to neuronal axons and increase the propagation speed of action potential. OLs are constantly generated from OL precursor cells (OPCs) throughout life span. The production of myelinating OLs consists of three canonical stages: OPCs, newly-formed OLs (NFOs), and mature myelinating OLs. Recently, single-cell RNA transcriptomic analyses identified a new population of oligodendroglial cells, namely differentiation committed OPCs (COPs). COPs represent a critical intermediate population between OPCs and NFOs, as revealed by specific expression of G-protein coupled receptor 17 (GPR17). The dysregulation of COPs leads to the remyelination failure in demyelinating diseases and impairs the replacement of lost myelin sheaths due to aging. Hence, understanding the development of COPs and their underlying regulatory network will be helpful in establishing new strategies for promoting myelin repair in demyelinating diseases. This review summarizes the current knowledge on the development and functions of COPs under both physiological and pathological conditions. Overall, COPs function as "checkpoints" to prevent inappropriate precocious OL differentiation and myelination through expressing distinct regulatory factors. Deepening our understanding of COPs may not only advance our knowledge of how OL lineage progresses during development, but also open the door to new treatments for demyelinating diseases.

Developmental dynamics of the single nucleus regulatory landscape of pig hippocampus

The hippocampus is a brain region associated with memory, learning and spatial navigation, its aging-related dysfunction is a common sign of Alzheimer's disease. Pig is a good model for human neurodegenerative disease, but our understanding of the regulatory program of the pig hippocampus and its cross-species conservation in humans remains limited. Here, we profiled chromatin accessibility in 33,409 high-quality nuclei and gene expression in 8,122 high-quality nuclei of the pig hippocampus at four postnatal stages. We identified 510,908 accessible chromatin regions (ACRs) in 12 major cell types, among which progenitor cells such as neuroblasts and oligodendrocyte progenitor cells showed a dynamic decrease from early to later developmental stages. We revealed significant enrichment of transposable elements in cell type-specific ACRs, particularly in neuroblasts. We identified oligodendrocytes as the most prominent cell type with the greatest number of genes that showed significant changes during the development. We identified ACRs and key transcription factors underlying the trajectory of neurogenesis (such as POU3F3 and EGR1) and oligodendrocyte differentiation (RXRA and FOXO6). We examined 27 Alzheimer's disease-related genes in our data and found that 15 showed cell type-specific activity (TREM2, RIN3 and CLU), and 15 genes displayed age-associated dynamic activity (BIN1, RABEP1 and APOE). We intersected our data with human genome-wide association study results to detect neurological disease-associated cell types. The present study provides a single nucleus-accessible chromatin landscape of the pig hippocampus at different developmental stages and is helpful for the exploration of pigs as a biomedical model in human neurodegenerative diseases.

Primary cilia control oligodendrocyte precursor cell proliferation in white matter injury via Hedgehog-independent CREB signaling

Remyelination after white matter injury (WMI) often fails in diseases such as multiple sclerosis because of improper recruitment and repopulation of oligodendrocyte precursor cells (OPCs) in lesions. How OPCs elicit specific intracellular programs in response to a chemically and mechanically diverse environment to properly regenerate myelin remains unclear. OPCs construct primary cilia, specialized signaling compartments that transduce Hedgehog (Hh) and G-protein-coupled receptor (GPCR) signals. We investigated the role of primary cilia in the OPC response to WMI. Removing cilia from OPCs genetically via deletion of Ift88 results in OPCs failing to repopulate WMI lesions because of reduced proliferation. Interestingly, loss of cilia does not affect Hh signaling in OPCs or their responsiveness to Hh signals but instead leads to dysfunctional cyclic AMP (cAMP)-dependent cAMP response element-binding protein (CREB)-mediated transcription. Because inhibition of CREB activity in OPCs reduces proliferation, we propose that a GPCR/cAMP/CREB signaling axis initiated at OPC cilia orchestrates OPC proliferation during development and in response to WMI.

Compound from Magnolia officinalis Ameliorates White Matter Injury by Promoting Oligodendrocyte Maturation in Chronic Cerebral Ischemia Models

Chronic cerebral hypoperfusion leads to white matter injury (WMI), which subsequently causes neurodegeneration and even cognitive impairment. However, due to the lack of treatment specifically for WMI, novel recognized and effective therapeutic strategies are urgently needed. In this study, we found that honokiol and magnolol, two compounds derived from Magnolia officinalis, significantly facilitated the differentiation of primary oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes, with a more prominent effect of the former compound. Moreover, our results demonstrated that honokiol treatment improved myelin injury, induced mature oligodendrocyte protein expression, attenuated cognitive decline, promoted oligodendrocyte regeneration, and inhibited astrocytic activation in the bilateral carotid artery stenosis model. Mechanistically, honokiol increased the phosphorylation of serine/threonine kinase (Akt) and mammalian target of rapamycin (mTOR) by activating cannabinoid receptor 1 during OPC differentiation. Collectively, our study indicates that honokiol might serve as a potential treatment for WMI in chronic cerebral ischemia.

Neurovascular glial unit: A target of phytotherapy for cognitive impairments

BACKGROUND

Neurovascular glial unit (NVGU) dysfunction has been reported to be an early and critical event in the pathophysiology of Alzheimer's disease (AD) and vascular dementia (VD). Although herbal medicines, with their favorable safety profiles and low adverse effects, have been suggested to be useful for the treatment of cognitive impairment, the potential role of the NVGU as the target of the effects of herbal medicines is still unclear.

PURPOSE

This review aimed to retrieve evidence from experimental studies of phytopharmaceuticals targeting the NVGU for the treatment of cognitive impairment in AD and VD, and discussed the potential of phytopharmaceuticals to improve cognitive impairment from the perspective of the NVGU.

STUDY DESIGN AND METHODS

We systematically searched PubMed, Google Scholar, Web of Science, and CNKI. The keywords used for searching information on the NVGU in the treatment of cognitive impairments included "Alzheimer's disease," "Vascular dementia," "Herbal medicines," "Natural products," "Neurovascular," "Adverse reaction," and "Toxicity, etc." We selected studies on the basis of predefined eligibility criteria.

RESULTS

NVGU mainly consists of endothelial cells, pericytes, astrocytes, microglia, oligodendrocytes, and neurons, and damage to these cells can induce cognitive impairment by impairing the blood-brain barrier (BBB) and cerebral blood flow (CBF) as well as neuronal function. The active components of herbal medicines, including Ginkgo biloba L., Ginseng Radix et Rhizoma, Epimedium Folium, Chuanxiong Rhizoma, Carthami flos, and Acorus tatarinowii Schott, as well as traditional Chinese medicine prescriptions have shown the potential to improve BBB function and increase CBF to prevent cognitive impairment by inhibiting astrocyte and microglia activation, protecting oligodendrocyte myelin function, reducing neuronal apoptosis, and promoting angiogenesis.

CONCLUSIONS

Herbal medicines demonstrate great potential to prevent cognitive impairment. Multiple components from herbal medicines may function through different signaling pathways to target the NVGU. Future studies using novel drug-carrier or delivery systems targeting the NVGU will certainly facilitate the development of phytopharmaceuticals for AD and VD.