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Formation of myelin, the electrical insulation on axons produced by oligodendrocytes, is controlled by complex cell-cell signaling that regulates oligodendrocyte development and myelin formation on appropriate axons. If electrical activity could stimulate myelin induction, then neurodevelopment and the speed of information transmission through circuits could be modified by neural activity. We find that release of glutamate from synaptic vesicles along axons of mouse dorsal root ganglion neurons in culture promotes myelin induction by stimulating formation of cholesterol-rich signaling domains between oligodendrocytes and axons, and increasing local synthesis of the major protein in the myelin sheath, myelin basic protein, through Fyn kinase-dependent signaling. This axon-oligodendrocyte signaling would promote myelination of electrically active axons to regulate neural development and function according to environmental experience.

The Myelin Basic Protein (MBP) gene is essential for myelin sheath formation in the central nervous system. Coding and noncoding single-nucleotide polymorphisms (SNPs) can impair the protein structure and function, contributing to demyelinating diseases exemplified by multiple sclerosis. This study aimed to assess the impact of SNPs in the MBP gene on protein structure and function. We employed a comprehensive approach to investigate the impact of both noncoding and coding SNPs of the MBP gene. Initially, we utilized RegulomeDB to assess the regulatory roles of SNPs located in the 3' untranslated regions (3' UTRs). Subsequently, we examined the influence of the 3' UTR SNPs on microRNA (miRNA) binding sites using PolymiRTS. Furthermore, we analyzed the functional 3' UTR SNPs using RNAfold to evaluate their impact on RNA structure. To predict deleterious nonsynonymous SNPs (nsSNPs), various bioinformatics tools, including SIFT, PolyPhen-2, PROVEAN, META-SNP, ESNPs&GO, PANTHER, and AlphaMissense, were employed. Protein stability was assessed using I-Mutant2.0, MUpro, and DDMut. Structural modeling was performed with AlphaFold, and both wild-type and mutant proteins were visualized in UCSF ChimeraX. Conservation analysis was conducted using the ConSurf tool, and protein interaction networks were explored using the STRING database. Eight noncoding SNPs were identified as potential regulatory SNPs, affecting the miRNA binding sites. Moreover, three nsSNPs, rs1971676214 (D173E), rs1242552448 (D173H), and rs772570115 (G176W), were consistently predicted to be pathogenic and to destabilize the protein structure. These variants were located in highly conserved sites and disrupted hydrogen bonds. STRING analysis revealed interactions between MBP and other myelin-related, immune, and signaling proteins, linking it to CNS and autoimmune pathways. This study identified eight noncoding 3' UTR SNPs and three potentially pathogenic nsSNPs that may compromise gene expression and protein structure and function, respectively, offering insight into genetic mechanisms of demyelination.

Rapid and efficient protocols to generate oligodendrocytes (OL) from human induced pluripotent stem cells (iPSC) are currently lacking, but may be a key technology to understand the biology of myelin diseases and to develop treatments for such disorders. Here, we demonstrate that the induction of three transcription factors (SOX10, OLIG2, NKX6.2) in iPSC-derived neural progenitor cells is sufficient to rapidly generate O4⁺ OL with an efficiency of up to 70% in 28 d and a global gene-expression profile comparable to primary human OL. We further demonstrate that iPSC-derived OL disperse and myelinate the CNS of Mbpshi/shi Rag −/− mice during development and after demyelination, are suitable for in vitro myelination assays, disease modeling, and screening of pharmacological compounds potentially promoting oligodendroglial differentiation. Thus, the strategy presented here to generate OL from iPSC may facilitate the studying of human myelin diseases and the development of high-throughput screening platforms for drug discovery.

Immune dysregulation, specifically of inflammatory processes, has been linked to behavioral symptoms of depression in both human and rodent studies. Here, we evaluated the antidepressant effects of immunization with altered peptide ligands of myelin basic protein (MBP)—MBP87–99[A91, A96], MBP87–99[A91], and MBP87–99[R91, A96]—in different models of depression and examined the mechanism by which these peptides protect against stress-induced depression. We found that a single dose of subcutaneously administered MBP87–99[A91, A96] produced antidepressant-like effects by decreasing immobility in the forced swim test and by reducing the escape latency and escape failures in the learned helplessness paradigm. Moreover, immunization with MBP87–99[A91, A96] prevented and reversed depressive-like and anxiety-like behaviors that were induced by chronic unpredictable stress (CUS). However, MBP87–99[R91, A96] tended to aggravate CUS-induced anxiety-like behavior. Chronic stress increased the production of peripheral and central proinflammatory cytokines and induced the activation of microglia in the prelimbic cortex (PrL), which was blocked by MBP87–99[A91, A96]. Immunization with MBP-derived altered peptide ligands also rescued chronic stress-induced deficits in p11, phosphorylated cyclic adenosine monophosphate response element binding protein, and brain-derived neurotrophic factor expression. Moreover, microinjections of recombinant proinflammatory cytokines and the knockdown of p11 in the PrL blunted the antidepressant-like behavioral response to MBP87–99[A91, A96]. Altogether, these findings indicate that immunization with altered MBP peptide produces prolonged antidepressant-like effects in rats, and the behavioral response is mediated by inflammatory factors (particularly interleukin-6), and p11 signaling in the PrL. Immune–neural interactions may impact central nervous system function and alter an individual’s response to stress.

The myelin basic protein (MBP) is the most abundant intracellular protein of the myelin, which forms the electrically insulating sheath of axons of many actively functioning neurons. This protein binds the opposite membranes of the flattened processes of oligodendrocytes and plays a crucial role in myelin compaction. Here we show that MBP is present in amyloid form in the oligodendrocytes in the brain of vertebrates. It forms SDS-resistant insoluble aggregates and clearly colocalizes with Congo Red and Thioflavin S in vivo , ex vivo, and in vitro. The fibrils of MBP extracted from the brain are detected by electron microscopy and exhibit apple-green birefringence after Congo Red staining. We showed that the central region of MBP, spanning amino acid residues 60–119, is responsible for the formation of amyloid fibrils. Based on these data, we present a model in which MBP not only connects the opposite membranes of oligodendrocyte processes but also provides longitudinal amyloid stitching of myelin sheaths. Amyloid fibrils appear to be an ideal natural material for myelin compaction and axon insulation.

Multiple sclerosis (MS) is a devastating autoimmune disease that leads to the destruction of the myelin sheath in the human central nervous system (CNS). Infection by viruses and bacteria has been found to be strongly associated with the onset of MS or its severity. We postulated that the immune system’s attack on the myelin sheath could be triggered by viruses and bacteria antigens that resemble myelin sheath components. An in-silico bioinformatics approach was undertaken in order to identify viral and bacterial antigens that resemble myelin oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP). To this end, we simultaneously analyzed both protein structures and amino acid sequences from viral and bacterial proteins and compared them to MOG and MBP. Possible associations between MBP and human parvovirus B19 (HPV-B19) and adeno-associated virus 4 (AAV-4) capsid protein structures were identified. MBP and MOG were associated with antigens from different viruses and bacteria, including Aspergillus species , Lactobacillus , Burkholderia , Clostridium , Schizosaccharomyces , SARS-CoV-2, and some gut flora metabolites. We also identified similarities between MBP and MOG proteins and bile salt hydrolase (BSH), glycosyltransferase (WcfQ), and Wzy enzymes. Identical amino acids between MBP and BSH at the active site, and protected amino acids in MOG aligning with WcfQ and Wzy enzymes were observed. Overall, our results offer valuable insights into the role of different viral and bacterial protein antigens in MS pathogenesis and suggest the possibility of identifying new therapeutic targets using in silico bioinformatics approaches. Our proposed approach could also likely be adapted for other CNS diseases in order to develop new biological insights and treatments.

The transcriptional regulatory network governing the differentiation and functionality of oligodendrocytes (OLs) is essential for the formation and maintenance of the myelin sheath, and hence for the proper function of the nervous system. Perturbations in the intricate interplay of transcriptional effectors within this network can lead to a variety of nervous system pathologies. In this study, we identify Gtf2i -encoded general transcription factor II-I (Tfii-i) as a regulator of key myelination-related genes. Gtf2i deletion from myelinating glial cells in male mice leads to functional alterations in central nervous system (CNS) myelin, including elevated mRNA and protein expression levels of myelin basic protein (Mbp), the central myelin component, enhanced connectivity properties, and thicker myelin wrapping axons with increased diameters. These changes resulted in faster axonal conduction across the corpus callosum (CC), and improved motor coordination. Furthermore, we show that in mature OLs (mOLs), Tfii-i directly binds to regulatory elements of Sox10 and Mbp . In the peripheral nervous system (PNS), Gtf2i deletion from Schwann cells (SCs) leads to hypermyelination of the tibial branch of the sciatic nerve (SN). These findings add to our understanding of myelination regulation and specifically elucidate a cell-autonomous mechanism for Tfii-i in myelinating glia transcriptional network. The transcriptional regulation of oligodendrocytes has an essential role in myelin formation and maintenance. Here, the authors identify the transcription factor Tfii-i as a regulator of myelin genes expression in the nervous system and show that its loss enhances myelin thickness and nerve conduction.

•The role of MBP gene expression on white matter myelin elaboration was identified.•We validated a model-free reconstruction method for robust brain MWF mapping.•The findings were augmented with detailed, tract-wise measures of AWF.•Our hypomyelinated mouse models act as a tool for calibrated myelin-sensitive MRI. Non-invasive myelin water fraction (MWF) and g-ratio mapping using microstructural MRI have the potential to offer critical insights into brain microstructure and our understanding of neuroplasticity and neuroinflammation. By leveraging a unique panel of variably hypomyelinating mouse strains, we validated a high-resolution, model-free image reconstruction method for whole-brain MWF mapping. Further, by employing a bipolar gradient echo MRI sequence, we achieved high spatial resolution and robust mapping of MWF and g-ratio across the whole mouse brain. Our regional white matter-tract specific analyses demonstrated a graded decrease in MWF in white matter tracts which correlated strongly with myelin basic protein gene (Mbp) mRNA levels. Using these measures, we derived the first sensitive calibrations between MWF and Mbp mRNA in the mouse. Minimal changes in axonal density supported our hypothesis that observed MWF alterations stem from hypomyelination. Overall, our work strongly emphasizes the potential of non-invasive, MRI-derived MWF and g-ratio modeling for both preclinical model validation and ultimately translation to humans.

Quaking RNA binding protein (QKI) is essential for oligodendrocyte development as myelination requires myelin basic protein mRNA regulation and localization by the cytoplasmic isoforms (e.g., QKI-6). QKI-6 is also highly expressed in astrocytes, which were recently demonstrated to have regulated mRNA localization. Here, we define the targets of QKI in the mouse brain via CLIPseq and we show that QKI-6 binds 3′UTRs of a subset of astrocytic mRNAs. Binding is also enriched near stop codons, mediated partially by QKI-binding motifs (QBMs), yet spreads to adjacent sequences. Using a viral approach for mosaic, astrocyte-specific gene mutation with simultaneous translating RNA sequencing (CRISPR-TRAPseq), we profile ribosome associated mRNA from QKI-null astrocytes in the mouse brain. This demonstrates a role for QKI in stabilizing CLIP-defined direct targets in astrocytes in vivo and further shows that QKI mutation disrupts the transcriptional changes for a discrete subset of genes associated with astrocyte maturation. Quaking RNA binding protein (QKI) is known for its role in oligodendrocyte maturation. Here, the authors define the QKI targets in the mouse brain and show that loss of QKI disrupts the expression of cell maturation-associated genes in astrocytes in vivo.

The integrity of the myelin sheath of the spinal cord (SC) is essential for motor coordination. Seipin is an endoplasmic reticulum transmembrane protein highly expressed in adipose tissue and motor neurons in the SC. It was reported Seipin deficiency induced lipid dysregulation and neurobehavioral deficits, but the underlying mechanism, especially in SC, remains to be elucidated. In present study, we found that Seipin and myelin basic protein (MBP) increased synchronously in SC of developmental stage of mice. Demyelination impaired motor coordination as well as MBP and Seipin expression, which were alleviated by remyelination. Moreover, Seipin deficiency impaired motor coordination of mice, accompanied by hypomyelination in spinal cord. Mechanistically, we further demonstrated that myelin content as labeled by Fluormyelin, myelin basic protein (MBP) was down-regulated by Seipin deficiency. Seipin deficiency led to reduction of myelin-forming oligodendrocytes (OLs) density in spinal cord. Notably, administration of rosiglitazone (RG), a classic PPARγ activator, successfully restored the phenotypes manifested by Seipin deficiency including reduced OLs density, hypomyelination, as well as motor dyscoordination. In summary, present study revealed that Seipin deficiency disrupted motor coordination by compromising myelination in SC, and RG treatment could rescue the phenotypes. This study throws light on the mechanism underlying Seipin deficiency associated disorders and paves ways for developing therapeutics toward those diseases. Graphical Abstract Seipin deficiency leading to hypomyelination and motor dyscoordination.