Department of Biochemistry, School of Medicine, Ewha Womans University, 911-1 Mok-6-dong, Yangcheon-ku, Seoul 158-710, Republic of Korea.
Biochem Biophys Res Commun. 2011 Nov 4;414(4):700-5. doi: 10.1016/j.bbrc.2011.09.136. Epub 2011 Oct 6.
The Swedish mutation of amyloid precursor protein (APP-sw) has been reported to dramatically increase beta amyloid production through aberrant cleavage at the beta secretase site, causing early-onset Alzheimer's disease (AD). DNA methylation has been reported to be associated with AD pathogenesis, but the underlying molecular mechanism of APP-sw-mediated epigenetic alterations in AD pathogenesis remains largely unknown. We analyzed genome-wide interplay between promoter CpG DNA methylation and gene expression in an APP-sw-expressing AD model cell line. To identify genes whose expression was regulated by DNA methylation status, we performed integrated analysis of CpG methylation and mRNA expression profiles, and identified three target genes of the APP-sw mutant; hypomethylated CTIF (CBP80/CBP20-dependent translation initiation factor) and NXT2 (nuclear exporting factor 2), and hypermethylated DDR2 (discoidin domain receptor 2). Treatment with the demethylating agent 5-aza-2'-deoxycytidine restored mRNA expression of these three genes, implying methylation-dependent transcriptional regulation. The profound alteration in the methylation status was detected at the -435, -295, and -271 CpG sites of CTIF, and at the -505 to -341 region in the promoter of DDR2. In the promoter region of NXT2, only one CpG site located at -432 was differentially unmethylated in APP-sw cells. Thus, we demonstrated the effect of the APP-sw mutation on alteration of DNA methylation and subsequent gene expression. This epigenetic regulatory mechanism may contribute to the pathogenesis of AD.
瑞典突变淀粉样前体蛋白(APP-sw)已被报道通过β 分泌酶位点的异常切割极大地增加β 淀粉样蛋白的产生,导致早发性阿尔茨海默病(AD)。已经报道 DNA 甲基化与 AD 发病机制有关,但 APP-sw 介导的 AD 发病机制中表观遗传改变的潜在分子机制在很大程度上仍然未知。我们分析了 APP-sw 表达的 AD 模型细胞系中启动子 CpG DNA 甲基化和基因表达之间的全基因组相互作用。为了鉴定受 DNA 甲基化状态调节的表达基因,我们对 CpG 甲基化和 mRNA 表达谱进行了综合分析,鉴定出 APP-sw 突变体的三个靶基因;低甲基化的 CTIF(CBP80/CBP20 依赖性翻译起始因子)和 NXT2(核输出因子 2)和高甲基化的 DDR2(盘状结构域受体 2)。用去甲基化剂 5-氮杂-2'-脱氧胞苷处理可恢复这三个基因的 mRNA 表达,表明存在甲基化依赖的转录调控。在 CTIF 的-435、-295 和-271 CpG 位点以及 DDR2 启动子的-505 至-341 区域检测到 CTIF 甲基化状态的深刻改变。在 NXT2 的启动子区域,仅位于-432 的一个 CpG 位点在 APP-sw 细胞中存在差异非甲基化。因此,我们证明了 APP-sw 突变对 DNA 甲基化改变和随后基因表达的影响。这种表观遗传调控机制可能有助于 AD 的发病机制。