Geriatric Research, Education, and Clinical Center, VA Puget Sound Health Care System, Seattle, WA 98108, USA; Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Washington, Seattle, WA 98104, USA.
Geriatric Research, Education, and Clinical Center, VA Puget Sound Health Care System, Seattle, WA 98108, USA.
Brain Res. 2018 Nov 1;1698:179-186. doi: 10.1016/j.brainres.2018.08.006. Epub 2018 Aug 3.
The apolipoprotein E gene (APOE) is the strongest genetic risk factor for developing Alzheimer's disease (AD). Our recent identification of altered APOE DNA methylation in AD postmortem brain (PMB) prompted this follow-up study. Our goals were to (i) validate the AD-differential methylation of APOE in an independent PMB study cohort and (ii) determine the cellular populations (i.e., neuronal vs. non-neuronal) of AD PMB that contribute to this differential methylation. Here, we obtained an independent cohort of 57 PMB (42 AD and 15 controls) and quantified their APOE methylation levels from frontal lobe and cerebellar tissue. We also applied fluorescence-activated nuclei sorting (FANS) to separate neuronal nuclei from non-neuronal nuclei within the tissue of 15 AD and 14 control subjects. Bisulfite pyrosequencing was used to generate DNA methylation profiles of APOE from both bulk PMB and FANS nuclei. Our results provide independent validation that the APOE CGI holds lower DNA methylation levels in AD compared to control in frontal lobe but not cerebellar tissue. Our data also indicate that the non-neuronal cells of the AD brain, which are mainly composed of glia, are the main contributors to the lower APOE DNA methylation observed in AD PMB. Given that astrocytes are the primary producers of ApoE in the brain our results suggest that alteration of epigenetically regulated APOE expression in glia could be an important part of APOE's strong effect on AD risk.
载脂蛋白 E 基因（APOE）是阿尔茨海默病（AD）最强的遗传风险因素。我们最近在 AD 死后大脑（PMB）中发现了 APOE DNA 甲基化的改变，这促使我们进行了这项后续研究。我们的目标是：（i）在独立的 PMB 研究队列中验证 APOE 的 AD 差异甲基化；（ii）确定导致这种差异甲基化的 AD PMB 的细胞群体（即神经元与非神经元）。在这里，我们获得了一个独立的 PMB 队列，其中包含 57 个样本（42 个 AD 和 15 个对照），并从额叶和小脑组织中定量测定了它们的 APOE 甲基化水平。我们还应用荧光激活核分选（FANS）技术从 15 个 AD 和 14 个对照受试者的组织中分离神经元核和非神经元核。亚硫酸氢盐焦磷酸测序用于从 PMB 组织和 FANS 核中生成 APOE 的 DNA 甲基化图谱。我们的结果独立验证了 APOE CGI 在 AD 患者的额叶组织中比对照具有更低的 DNA 甲基化水平，但在小脑组织中没有这种差异。我们的数据还表明，AD 大脑中的非神经元细胞（主要由胶质细胞组成）是导致 AD PMB 中观察到的 APOE DNA 低甲基化的主要原因。鉴于星形胶质细胞是大脑中 ApoE 的主要产生者，我们的结果表明，胶质细胞中受表观遗传调控的 APOE 表达的改变可能是 APOE 对 AD 风险影响的重要组成部分。
