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TET1-mediated DNA hydroxy-methylation regulates adult remyelination

ABSTRACT: Adult myelination is essential for brain function and response to injury, but the molecular mechanisms remain elusive. Here we identify DNA hydroxy-methylation, an epigenetic mark catalyzed by Ten-Eleven translocation (TET) enzymes, as necessary for adult myelin repair. While DNA hydroxy-methylation and high levels of TET1 were detected in young adult mice during myelin regeneration after demyelination, this process was defective in old mice. Constitutive or inducible lineage-specific ablation of Tet1 (but not of Tet2) recapitulated the age-related decline of DNA hydroxy-methylation and inefficient remyelination. Genome-wide hydroxy-methylation and transcriptomic analysis identified solute carrier gene families as TET1 targets. Lower transcripts for these genes in Tet1 mutants and old mice were associated with swelling at the neuroglial interface, a phenotype detected also in zebrafish Slc12a2b mutants. We conclude that TET1-mediated DNA hydroxy-methylation is necessary for adult myelination after injury, by modulating the levels of the solute carrier SLC12A2 at the axo-myelin interface.

ORGANISM(S): Mus musculus

PROVIDER: GSE137611 | GEO | 2020/03/14

REPOSITORIES: GEO

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Project description:DNA methylation is a key epigenetic regulator of mammalian embryogenesis and somatic cell differentiation. Using high-resolution genome-scale maps of methylation patterns, we show that the formation of myelin in the peripheral nervous system, proceeds with progressive DNA demethylation, which coincides with an upregulation of critical genes of the myelination process. More importantly, we found that, in addition to expression of DNA methyltransferases and demethylases, the levels of S-adenosylmethionine (SAMe), the principal biological methyl donor, could also play a critical role in regulating DNA methylation during myelination and in the pathogenesis of diabetic neuropathy. In summary, this study provides compelling evidence that SAMe levels need to be tightly controlled to prevent aberrant DNA methylation patterns, and together with recently published studies on the influence of SAMe on histone methylation in cancer and embryonic stem cell differentiation show that in diverse biological processes, the methylome, and consequently gene expression patterns, are critically dependent on levels of SAMe. Axonal myelination by Schwann cells in the peripheral nervous system is essential for rapid saltatory impulse conduction, and malformation or destruction of myelin sheaths can lead to severe motor and sensory disabilities (peripheral neuropathies). Using high-resolution genome-scale methylome maps, we found that DNA methylation could play a critical role in the generation of myelinated Schwann cells. This process was accompanied by a global DNA demethylation at most genomic elements. Notably, demethylation at gene-regulatory regions was associated with activation of critical myelination-specific genes. Furthermore, we found an aberrant DNA methylation pattern in a mouse model of diabetic neuropathy, which could be involved in the pathogenesis of the disease. Importantly, we found that these methylation patterns in both situations could be regulated by levels of S-adenosylmethionine (SAMe), the principal biological methyl donor. Together with recent studies on the influence of SAMe on histone methylation in diverse biological processes, we conclude that the methylation landscape of cells could be critically dependent on levels of SAMe. These provide a mechanistic link between metabolism and gene regulatory networks in normal and pathological situations. Sciatic nerves from post natal day 90 GNMT (wt and KO) mice of either sex were dissected and pooled together, 2 replicates per sample group.

Project description:DNA methylation is a key epigenetic regulator of mammalian embryogenesis and somatic cell differentiation. Using high-resolution genome-scale maps of methylation patterns, we show that the formation of myelin in the peripheral nervous system, proceeds with progressive DNA demethylation, which coincides with an upregulation of critical genes of the myelination process. More importantly, we found that, in addition to expression of DNA methyltransferases and demethylases, the levels of S-adenosylmethionine (SAMe), the principal biological methyl donor, could also play a critical role in regulating DNA methylation during myelination and in the pathogenesis of diabetic neuropathy. In summary, this study provides compelling evidence that SAMe levels need to be tightly controlled to prevent aberrant DNA methylation patterns, and together with recently published studies on the influence of SAMe on histone methylation in cancer and embryonic stem cell differentiation show that in diverse biological processes, the methylome, and consequently gene expression patterns, are critically dependent on levels of SAMe. Axonal myelination by Schwann cells in the peripheral nervous system is essential for rapid saltatory impulse conduction, and malformation or destruction of myelin sheaths can lead to severe motor and sensory disabilities (peripheral neuropathies). Using high-resolution genome-scale methylome maps, we found that DNA methylation could play a critical role in the generation of myelinated Schwann cells. This process was accompanied by a global DNA demethylation at most genomic elements. Notably, demethylation at gene-regulatory regions was associated with activation of critical myelination-specific genes. Furthermore, we found an aberrant DNA methylation pattern in a mouse model of diabetic neuropathy, which could be involved in the pathogenesis of the disease. Importantly, we found that these methylation patterns in both situations could be regulated by levels of S-adenosylmethionine (SAMe), the principal biological methyl donor. Together with recent studies on the influence of SAMe on histone methylation in diverse biological processes, we conclude that the methylation landscape of cells could be critically dependent on levels of SAMe. These provide a mechanistic link between metabolism and gene regulatory networks in normal and pathological situations. Sciatic nerves from C57Bl6J mice of either sex, were dissected and pooled together at different developmental stages, 3 replicates per sample group.

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TET1-mediated DNA hydroxy-methylation regulates adult remyelination

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