Redefining the Role of APOE RNA Transcripts in Alzheimer's Disease

载脂蛋白E基因(ApoE)有三种遗传变异(即ε2、ε3和ε4)，以及ε4变异。 载脂蛋白E是阿尔茨海默病(AD)最强的遗传风险因素。这意味着APOE扮演着一个重要的角色 在阿尔茨海默病的发展中的作用。ApoE基因产物(信使核糖核酸和蛋白质)的表达水平是潜在的 这可能部分解释了APOE在AD中的影响。但关于载脂蛋白E在阿尔茨海默病中表达的研究一直 产生了相互矛盾的数据，对于ε4运营商产生的APOE是更高还是更低，还没有达成共识 信使核糖核酸/蛋白质这种相互矛盾的结果严重模糊了对APOE在 广告。显然，载脂蛋白E的表达、ε2/ε3/ε4等位基因和AD状态之间存在差距。有必要 更好地理解他们之间的关系。在我们的初步研究中，我们发现只有一小部分APOE 信使核糖核酸延伸到基因的全长，也就是说，大多数信使核糖核酸被提前终止，并且不能 产生功能性载脂蛋白E。我们还检测到APOE RNA中存在新的环状RNA 泳池。这些数据表明，APOE的RNA转录是复杂的，可能更具生物学意义 结果比之前认为的要好；过去的载脂蛋白基因表达研究可能存在缺陷 因为没有测量真正的功能全长的mrna。破译不同APOE RNA之间的相互作用 转录本、全长m RNA的产生以及ε2/ε3/ε4等位基因将使我们更好地理解 载脂蛋白E表达在AD发病中的作用。在这项研究中，我们假设只有一小部分APOE mRNA延长了 产生载脂蛋白E的全长基因；ε2/ε3/ε4等位基因对这些蛋白的产生有不同的调节作用 功能性全长mRNAs，从而增加了对AD风险的不同影响。我们的长期目标是充分了解 研究载脂蛋白E的基因调控，并利用这一知识开发预防和/或干预AD的策略。 我们的短期目标是澄清APOE RNA转录、ε2/ε3/ε4变体和 AD风险，并了解调控APOE RNA产生的分子机制。我们设计了 这项研究的三个具体目标。目标1将研究APOE RNA并将它们的表达水平与 ε2/ε3/ε4等位基因变异与人死后脑内AD状态的关系目标2将描述表观遗传学 调节人类细胞系中APOE RNA转录的机制。目标3将研究其功能， 新发现的载脂蛋白E环状RNA在人体细胞系和体液中的生物发生和分布。我们的 工作不会削弱apoE蛋白的作用；相反，它将剖析apoE RNA对apoE的贡献 蛋白质对补充载脂蛋白E基因在AD中的综合作用。

The apolipoprotein E gene (APOE) has three genetic variants (i.e., ε2, ε3, and ε4), and the ε4 variant of the APOE is the strongest genetic risk factor for Alzheimer's disease (AD). This means that APOE plays a major role in the development of AD. The expression levels of APOE gene products (mRNA and protein) are potential candidates that may partially explain APOE's effects in AD. But studies on APOE expression in AD have always yielded conflicting data, and there is no consensus on whether ε4 carriers produce higher or a lower APOE mRNA/protein. Such conflicting results have significantly obscured interpretation of APOE's expression role in AD. Clearly, gaps exist between APOE's expression, the ε2/ε3/ε4 alleles, and AD status. There is a need for better understanding their relationship. In our preliminary study, we have found that only a fraction of APOE mRNA extends the full length of the gene; that is, the majority of mRNAs are prematurely terminated and cannot produce functional apoE proteins. We have also detected the presence of novel circular RNAs in APOE RNA pools. These data suggest that APOE's RNA transcription is complex and may pose more biological consequences than previously thought; and that past APOE mRNA expression studies may have been flawed for not measuring the true functional full-length mRNA. Deciphering the interplay between various APOE RNA transcripts, the production of full-length mRNA, and the ε2/ε3/ε4 alleles will lead us to better understand the effects of APOE expression in AD. In this study, we hypothesize that only a fraction of APOE mRNA extend the full length of the gene to produce apoE protein; the ε2/ε3/ε4 alleles differentially modulate the production of these functional full-length mRNAs, thereby adding diverse effects to AD risk. Our long-term goal is to fully understand gene regulation of APOE and to use this knowledge to develop strategies for AD prevention and/or intervention. Our short-term goal is to clarify the relationship between APOE RNAs transcription, the ε2/ε3/ε4 variants, and AD risk and to understand the molecular mechanisms that regulate APOE RNAs production. We have designed three specific aims for the study. Aim 1 will investigate APOE RNAs and correlate their expression levels with the ε2/ε3/ε4 allele variants, and AD status in human postmortem brain. Aim 2 will characterize the epigenetic mechanisms that modulate the APOE RNAs transcription in human cell lines. Aim 3 will investigate the function, biogenesis, and distribution of the newly discovered APOE circular RNA in human cell lines and body fluid. Our work will not diminish the role of apoE protein; instead, it will dissect the contributions of APOE RNA from apoE protein to complement APOE gene's comprehensive effects in AD.