Determining the role of ribosomal DNA in metazoan aging

摘要 核糖体RNA(RRNA)占所有细胞转录本的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和 线粒体丰度，提示rDNA拷贝数可能与表型有关。二 RDNA拷贝数方面--基因组重复数和染色体外重复数 -与衰老有关。具体地说，已经观察到基因组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)增加 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 仍然悬而未决。而基因组rDNA拷贝数随着年龄的增加而减少的报道 有丝分裂后的哺乳动物组织，目前还不清楚这一特征有多普遍，也不清楚rdna是通过什么机制产生的。 在多细胞真核生物中，拷贝可能丢失。此外，与年龄相关的ECC-rDNA增加是 广泛存在于酵母中，但在后生动物中很大程度上未被发现。我建议利用 秀丽线虫作为衰老模型1)rDNA拷贝数是否影响衰老以及2)如何影响衰老 年龄影响rDNA拷贝数。在目标1中，我将分两组评估寿命、生育力和发育时间 重组自交系(RIL)。第一套RILS，我用野生线虫的杂交后代培育出来的 分离株和实验室菌株的衍生株，是专门为高拷贝(~420拷贝)或低拷贝(~130拷贝)选择的 RDNA拷贝数。线虫多亲本实验进化的第二套重组自交系 (CeMEE)面板，是从16个野生分离物的高级杂交中发展出来的，这些野生分离物经历了多次 在RIL开发之前经历了几轮实验进化。对于这两组RIL，我将在全基因组范围内执行 关联分析确定rDNA拷贝数是加性影响还是上位性影响衰老 表型。在目标2中，我将评估基因组rDNA拷贝数和ECC-rDNA水平在C。 优雅女装。这些目的共同决定了后生动物系统中rDNA和衰老之间的关系， 包括rDNA拷贝数的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.