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复合体，位于 真核生物的线形染色体。在大多数人类细胞中，端粒随着年龄的增长而缩短，而且它们的端粒 初始长度预先确定了细胞的寿命。端粒维持基因突变导致 癌症、过早衰老和一些与年龄相关的疾病。而端粒的平均长度 人类表现出相当大的个体间差异，并似乎处于强烈的遗传 但是，端粒长度设定点的确定因素的确切性质仍然难以捉摸。在我们的 利用模式植物拟南芥的初步结果，我们确定了一个主效QTL。 一个可解释48%端粒长度变异的重组近交系群体并对其进行作图 QTL定位到一个候选基因NOP2A。值得注意的是，人类NOP2同源基因的表达与 肿瘤发生，并作为肿瘤发展的预后标记物。在这项提案中，我们 将利用遗传、基因组、生化和表观遗传学方法来破译这种机制 ，并发现更多的遗传和表观遗传因素参与 端粒长度控制。在目标1中，通过一系列量化的转基因救援实验 我们将确定原因SNP并探索NOP2A影响端粒的机制 长度。我们还将利用强大的拟南芥遗传、基因组和转录工具来 鉴定和鉴定NOP2A依赖的基因和反式调节因子。在目标2中，我们将 对1,001个拟南芥基因型进行GwA，并精细定位双亲中的额外QTL 拟南芥RIL群体识别影响端粒长度的新的多态。我们会 然后进行一系列的敲除和转基因抢救实验，从功能上 确定候选基因并验证它们在端粒生物学中的作用。在目标3中，我们将利用 一个DNA几乎相同的独一无二的刺参表观遗传重组近交系群体 序列，但变量甲基化和基因表达谱，以精细映射之前的两个 确定了控制端粒长度的大效表观QTL，并分析了可遗传性表观遗传 变异直接影响端粒长度。总体而言，这项研究的结果预计将 显著提高对端粒长度潜在遗传差异的理解 天然拟南芥种群的多态现象。因为端粒调节的方式是 高度保守，我们的数据也可能为不同的分子基础提供新的见解 与人类端粒异常有关的疾病的增龄率和易感性。

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.