Genetic and epigenetic architecture of natural telomere length variation

项目摘要 端粒是进化上保守的蛋白质-DNA复合物，位于端粒的物理末端。 线性真核染色体。在大多数人类细胞中，端粒随着年龄的增长而缩短， 初始长度预先决定细胞寿命。端粒维持基因的突变导致 癌症、过早衰老和许多与年龄相关的疾病。而平均端粒长度在 人类表现出相当大的个体间差异，似乎是在强烈的遗传 尽管端粒长度设定值的精确控制是不确定的，但建立端粒长度设定值的因素的确切性质仍然是难以捉摸的。在我们 初步结果使用模式植物拟南芥，我们确定了一个主效QTL， 一个重组的近交群体，解释了48%的端粒长度变异，并绘制了这一图谱。 候选基因NOP2A。值得注意的是，人N0P2直系同源物的表达与以下相关： 肿瘤发生并作为肿瘤发展的预后标志物。在本提案中，我们 将利用遗传学、基因组学、生物化学和表观遗传学的方法来破译这一机制 AtNOP2A功能，并揭示其他遗传和表观遗传因素参与 端粒长度控制。在目标1中，通过一系列定量转基因拯救实验 我们将鉴定致病SNP并探索NOP2A影响端粒的机制 长度我们还将采用强大的拟南芥遗传学，基因组学和转录组学工具， 鉴定和表征NOP2A依赖性基因和反式调节子。在目标2中，我们 在1，001个拟南芥基因型中进行GWAS，并在一个双亲本中精细定位额外的QTL。 拟南芥RIL群体，以确定新的多态性，影响端粒长度。我们将 然后进行一系列敲除和转基因拯救实验， 表征候选基因并验证其在端粒生物学中的作用。在目标3中，我们将利用 一个独特的A.具有几乎相同DNA的拟南芥表观遗传重组近交群体 序列，但可变的甲基化和基因表达谱，以精细映射两个以前 确定了控制端粒长度的大效应表观QTL，并分析了可遗传的表观遗传 变异直接影响端粒长度。总的来说，这项研究的结果预计将 显著增加对端粒长度遗传差异理解 在自然拟南芥种群中的多态性。因为端粒调节的模式 高度保守，我们的数据也可能提供新的见解不同的分子基础， 人类的衰老率和易患疾病的倾向与端粒异常有关。

Project Summary Telomeres are evolutionarily conserved protein-DNA complexes at the physical ends of linear eukaryotic chromosomes. Telomeres shorten with age in most human cells, and their initial length pre-determines cellular lifespan. Mutations in telomere maintenance genes lead to cancer, premature aging and a number of age-related disorders. While mean telomere length in humans shows considerable inter-individual variation and appears to be under strong genetic control, the exact nature of factors establishing telomere length set point remains elusive. In our preliminary results using the model plant Arabidopsis thaliana we identify a major effect QTL in a recombinant inbred population that explains 48% of telomere length variation and map this QTL to a candidate gene, NOP2A. Notably, expression of the human NOP2 ortholog is linked to tumorigenesis and serves as a prognostic marker of tumor development. In this proposal, we will utilize genetic, genomic, biochemical and epigenetic approaches to decipher the mechanism of AtNOP2A function, and to uncover additional genetic and epigenetic factors involved in telomere length control. In Aim 1, through a series of quantitative transgenic rescue experiments we will identify the causal SNP and explore the mechanism by which NOP2A impacts telomere length. We will also employ powerful Arabidopsis genetic, genomic and transcriptomic tools to identify and characterize NOP2A-dependent genes and trans-regulators. In Aim 2, we will perform GWAS in 1,001 Arabidopsis genotypes and fine-map additional QTL in a bi-parental Arabidopsis RIL population to identify novel polymorphisms that affect telomere length. We will then perform a series of knock-out and transgenic rescue experiments to functionally characterize candidate genes and validate their role in telomere biology. In Aim 3, we will utilize a unique A. thaliana epigenetic recombinant inbred population with almost identical DNA sequences, but variable methylation and gene expression profiles, to fine-map two previously identified large-effect epi-QTL governing telomere length, and analyze how heritable epigenetic variation directly affects telomere length. Overall, the results of this study are expected to significantly increase understanding of genetic differences underlying telomere length polymorphism in natural Arabidopsis populations. Because modes of telomere regulation are highly conserved, our data may also provide novel insight into the molecular basis for different rates of aging and predisposition to diseases associated with telomere abnormalities in humans.