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Differential 5-methylcytosine and 5-hydroxymethylcytosine in Parkinson’s and Alzheimer’s Disease.

ABSTRACT: Background: 5-methylcytosine (5-mC) and its oxidized form, 5-hydroxymethylcytosine (5-hmC), are distinct epigenetic marks that help regulate gene expression in the mammalian brain. Existing studies have identified associations between 5-mC and neurodegenerative disease, but little work has examined the potential role of 5-hmC in Parkinson’s disease (PD) or Alzheimer’s disease (AD). Here, we utilized PD postmortem brain tissue and a public dataset from postmortem AD brains to analyze the effect of neurodegenerative disease on paired 5-mC and 5-hmC levels. Results: In PD samples, we measured genome-wide 5-mC and 5-hmC from control (n=3) and PD (n=6) brains using the Illumina EPIC array combined with bisulfite and oxidative bisulfite treatments (BS/oxBS-EPIC). In publicly sourced data, genome-wide 5-mC and 5-hmC were measured from control (n=25) and AD (n=62) human entorhinal cortex tissue using the Illumina 450K array combined with bisulfite and oxidative bisulfite treatment (BS/oxBS-450K). Paired 5-mC and 5-hmC beta values were generated using a custom pipeline of bioinformatics tools, and we modeled the effect of disease on paired 5-mC and 5-hmC data using a mixed effects beta regression model with a random effect for ID and an interaction term between disease category and DNA modification category (“5-mC” or “5-hmC”). We identified a number of CpG probes (AD: n=699, PD: total n = 80) that showed a significant interaction between disease status and DNA modification category (p-value < 2.4x10-7). Conclusions: While our PD data requires additional validation, our analyses suggest that there are widespread shifts in the balance between 5-mC and 5-hmC in Parkinson’s and Alzheimer’s disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE138597 | GEO | 2019/10/09

REPOSITORIES: GEO

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Project description:5-hydroxymethylcytosine (5hmC), converted from 5-methylcytosine (5mC) by Tet enzymes, has recently drawn attention as the ‘sixth base’ of DNA since it is considered to be an intermediate of the demethylation pathway. Nonetheless, it remains to be addressed how 5hmC is linked to the development of human imprinting disorders. In this regard, conventional bisulfite (BS) treatment is unable to differentiate 5hmC from 5mC. It is thus hypothesized that BS conversion-derived ‘hypermethylation’ at imprinting control regions (ICRs), which may cause human imprinting disorders, would in fact be attributable to excessively increased levels of 5hmC as well as 5mC. To test this hypothesis, we applied the newly developed oxidative BS (oxBS) treatment to detect 5hmC in blood samples from Kagami-Ogata syndrome (KOS14) patients caused by perturbed expression of clustered imprinted genes on 14q32.2 resulting from the hypermethylation of ICRs at this locus, IG-DMR and MEG3-DMR. oxBS with pyrosequencing and cloning-based sequencing revealed that there were few amounts of 5hmC at the hypermethylated IG-DMR in blood samples from KOS14 patients. oxBS with genome-wide methylation array analysis demonstrated that global levels of 5hmC were very low with similar distribution patterns in blood samples from KOS14 patients and normal controls. We also confirmed the presence of a large amount of 5hmC in the brain sample from a normal control. 5hmC is not a major component in abnormally hypermethylated ICRs or at a global level, at least in blood from KOS14 patients. As the brain sample contained a large amount of 5hmC, the neural tissues of KOS14 patients are promising candidates for analysis in elucidating the role of 5hmC in the neurodevelopmental context. We generated illumina 450k DNA methylation data for BS or oxBS converted samples of three KOS14 blood samples, one control pooled blood sample and one control brain sample with two technical replicates for each sample.

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Differential 5-methylcytosine and 5-hydroxymethylcytosine in Parkinson’s and Alzheimer’s Disease.

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