Unknown,Transcriptomics,Genomics,Proteomics

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Functional characterization of DNA methylation in the oligodendrocyte lineage [RNASeq_development]

ABSTRACT: Myelination in the CNS is modulated by interplay between transcription factors and recruitment of chromatin modifying enzymes. Using a network built from genome-wide DNA methylation and transcriptomic profiling of sorted oligodendrocyte lineage cells that integrates oligodendrocyte-specific ChIP-Seq data, we defined a crucial role of DNA methylation in coordinating the transition between progenitor cell cycle arrest and oligodendrocyte differentiation. We further identified DNA methyltransferase 1 (DNMT1) as key regulator of oligodendrocyte survival at this transition point, as we detected severe and extensive developmental hypomyelination only in Olig1cre/+;Dnmt1flox/flox but not in Olig1cre/+;Dnmt3aflox/flox mice or in Cnpcre/+;Dnmt1flox/flox. This phenotype was characterized by decreased expression of genes regulating myelination and lipid metabolism â despite the hypomethylation observed at these genetic loci Â â and upregulation of cell cycle and DNA-damage pathways. Therefore DNMT1 is a nodal point regulating proliferation, survival, and differentiation in the oligodendrocyte lineage, and is critical for cell number regulation in the developing brain. mRNA profiles of FAC-sorted P2 Pdgfra::GFP and P18 Plp1-GFP purified cell samples from mouse brains were generated by RNA-sequencing, in triplicate, using Illumina HiSeq 2000.

ORGANISM(S): Mus musculus

SUBMITTER: Sarah Moyon

PROVIDER: E-GEOD-66029 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Purpose: Epigenetic regulation contributes to pathogenesis of neurondegenerative disease. We found that dis-regulation of a 242-gene subnetwork related to DNA methylation regulated neuronal differentiation are common in AD and HD. There are two DNA methyltransferases, DNMT1 and DNMT3A, in the subnetwork. DNMT1 is one of top hub genes in the network and likely to play a key regulatory role in the subnetwork. To validate that DNMT1 is a key regulator for the subnetwork, and DNMT3A not as one, we constructed two brain-specific conditional knockout mice. Methods: Cortices were dissected from Dnmt1 conditional knockout (CKO), Dnmt3a CKO, and respective littermate control mice at 18 weeks. RNA was isolated from three biological replicates for each genotype using TRIzol (Invitrogen) extraction and isopropanol precipitation. RNA samples were resuspended in water and further purified with RNeasy columns with on-column DNase treatment (Qiagen). RNA purity was assessed by measuring the A260/A280 ratio using a NanoDrop and RNA quality checked using an Agilent 2100 Bioanalyzer (Agilent Technologies). Approximately 250 ng of total RNA per sample were used for library construction by the TruSeq RNA Sample Prep Kit (Illumina) and sequenced using the Illumina HiSeq 2500 instrument according to the manufacturer's instructions. Sequence reads were aligned to mouse genome assembly mm10 and quantified using Cufflinks. Results: Genes differentially expressed in CKO mice compared to littermate control mice, or the Dnmt1 CKO signature, including GSN (the genes with the largest number of connection in the subnetwork) and SOX10 (a key transcription factor of myelination), significantly overlaps with the subnetwork. Broadly, the Dnmt1 CKO signature is enriched for genes involved in GO biological processes immune response, lipid metabolism, endocytosis, glial cell differentiation, and nerve ensheatment, consistent with biological function of the subnetwork. Moreover, the Dnmt1 CKO mice show increased predilection to seizures, an incidence also increased in patients with AD (Amatniek et al, 2006) as well as juvenile form of HD (Cloud et al, 2012). In contrast, the Dnmt3a CKO signature does not overlap with the subnetwork (p=0.07) and is not enriched for any GO biological process. Conclusions: These results suggest the Dnmt1 regulates common genes related with AD and HD while Dnmt3a has little effect. All of the mice used in this study were handled in accordance with IACUC-approved protocols. Dnmt1flox/flox (Fan et al, 2001; Jackson-Grusby et al, 2001) and Dnmt3aflox/flox (Nguyen et al, 2007) mice were backcrossed onto a C57BL/6 background and crossed with Olig1-cre mice to generate Dnmt1 conditional knockout (Olig1cre/+;Dnmt1flox/flox) and littermate control (Olig1+/+;Dnmt1flox/flox) mice, and Dnmt3a conditional knockout (Olig1cre/+;Dnmt3aflox/flox) and littermate control (Olig1+/+;Dnmt3aflox/flox) mice.

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Functional characterization of DNA methylation in the oligodendrocyte lineage [RNASeq_development]

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