Determining the role of ribosomal DNA in metazoan aging

摘要 核糖体RNA（rRNA）占所有细胞转录物的80%。rRNA由长串联核糖体编码， DNA重复序列（rDNA）。rDNA拷贝数的差异与转录组的变化有关， 线粒体丰度，这表明rDNA拷贝数可能与表型有关。两 rDNA拷贝数方面-基因组重复序列的数量和染色体外重复序列的数量 - 与衰老有关。具体来说，在小鼠中观察到基因组rDNA重复序列的减少。 一些老化的哺乳动物组织此外，染色体外环状rDNA（ecc-rDNA） 重复发生在酵母复制年龄。rDNA拷贝数本身是否影响衰老表型 仍然没有解决。虽然基因组rDNA拷贝数随年龄的减少已经在特定的 在有丝分裂后的哺乳动物组织中，目前还不清楚这种特征有多普遍，或者通过什么机制rDNA 拷贝可能在多细胞真核生物中丢失。此外，与年龄相关的ecc-rDNA的增加已经被证实。 在酵母中被广泛表征，但在后生动物中大部分未被探索。我提议利用 秀丽隐杆线虫作为衰老模型，以确定1）rDNA拷贝数是否影响衰老和2）如何影响衰老 衰老影响rDNA拷贝数。在目标1中，我将分两组评估寿命、生育能力和发育长度 重组自交系（RILs）。第一套RILs，我从一个C。野生秀丽隐翅虫 分离株和实验室菌株的衍生物，专门选择高（~420个拷贝）或低（~130个拷贝） rDNA拷贝数。第二组RILs是C.多亲实验进化 （Cefenic）panel，是从16个野生分离物的高级互交开发的，所述野生分离物经历了多个 在RIL开发之前的几轮实验进化。对于两组RILs，我将进行全基因组 关联分析，以确定rDNA拷贝数是否相加或上位性地影响衰老 表型在目标2中，我将评估两个基因组rDNA拷贝数和ecc-rDNA水平在老化过程中，在C。 优雅这些目标将共同确定后生动物系统中rDNA与衰老之间的关系， 包括rDNA拷贝数变化是否是衰老的普遍标志。

ABSTRACT Ribosomal RNA (rRNA) accounts for 80% of all cellular transcripts. rRNA is encoded by long tandem ribosomal DNA repeats (rDNA). Differences in rDNA copy number associate with changes in transcriptome and mitochondrial abundance, which suggests that rDNA copy number may have bearing on phenotype. Two aspects of rDNA copy number – the number of genomic repeats, and the number of extrachromosomal repeats – have been associated with aging. Specifically, a reduction of genomic rDNA repeats has been observed in some aging mammalian tissues. Additionally, an increase in extrachromosomal circular rDNA (ecc-rDNA) repeats occurs with yeast replicative age. Whether rDNA copy number itself influences aging phenotypes remains unresolved. While reductions in genomic rDNA copy number with age have been reported in specific post-mitotic mammalian tissues, it is unclear how prevalent this feature is, or by what mechanisms rDNA copies may be lost in a multicellular eukaryote. Furthermore, age-associated increases in ecc-rDNA have been extensively characterized in yeast but have been largely unexplored in metazoans. I propose to utilize Caenorhabditis elegans as an aging model to determine 1) If rDNA copy number influences aging and 2) How aging affects rDNA copy number. In Aim 1, I will assess lifespan, fertility, and length of development in two sets of recombinant inbred lines (RILs). The first set of RILs, which I developed from a cross of a C. elegans wild isolate and a derivative of the lab strain, were selected specifically for high (~420 copies) or low (~130 copies) rDNA copy number. The second set of RILs, part of the C. elegans Multiparental Experimental Evolution (CeMEE) panel, were developed from an advanced intercross of 16 wild isolates that underwent multiple rounds of experimental evolution prior to RIL development. For both sets of RILs, I will perform genome-wide association analyses to determine if rDNA copy number either additively or epistatically affects aging phenotypes. In Aim 2, I will assess both genomic rDNA copy number and ecc-rDNA levels during aging in C. elegans. Together these Aims will determine the relationship between rDNA and aging in a metazoan system, including if rDNA copy number changes are a universal hallmark of aging.