Dissecting the influence of genetic background on aneuploidy tolerance in the model eukaryote Saccharomyces cerevisiae

摘要 染色体分离错误可以产生具有不正确数目的一个或多个染色体的细胞， 称为非整倍体。因此，非整倍性是一类特殊的突变，可以具有直接的表型 方面的影响.虽然非整倍体在哺乳动物发育过程中是有害的，但它在许多癌症中很常见 也是耐药肿瘤和真菌病原体进化的驱动因素。一个尚未解决的主要问题是 不同个体对非整倍体的耐受能力不同。了解基因如何 差异影响非整倍体耐受性对遗传学、人类生物学和 进化但研究哺乳动物系统这一主题极具挑战性，因为不可能 系统地操纵大量遗传背景中的核型。在这里，我们将解决 遗传变异如何影响细胞耐受染色体的能力 复制，在模型真核生物酿酒酵母。利用酵母遗传学的力量，我们 采用了一种方法，在几乎没有选择的情况下复制特定的酵母染色体。我们将应用 该方法旨在探索染色体重复耐受性遗传变异的广度和机制， （本文称为非整倍性）。Aim 1将使用这种方法复制16条染色体中的每一条， 酵母，在几十个非实验室菌株跨越酵母菌群。结果将表征 非整倍体耐受性的自然变异，并将测试这种变异是否由于罕见等位基因或 在特定谱系中的许多菌株中持续存在。初步结果表明， 非整倍体耐受性目的2将测试非整倍体敏感性的变化是否是由于 “普遍的”非整倍性耐受，其中细胞是敏感的，而不管哪个染色体被复制， 与染色体特异性敏感性相比，染色体特异性敏感性可能是由编码在 这些染色体。我们将测试如何以及染色体特异性的敏感性解释的添加剂 基因模型是基于测量的基因的过度表达的适应性成本，这里从一个 在每个菌株中表达的基因过表达文库。目标3将开始揭示生理和 变异非整倍体耐受性的遗传机制。我们将首先测试我们的假设，即遗传变异在 非整倍体耐受性是由于处理蛋白质稳态应激的能力的变化。我们会用大量的- 分离作图来研究该变异的遗传结构并鉴定偶然基因。酵母是一种 这是一个研究这个基本问题的杰出模型，因为许多细胞机制和遗传学 这些原则在包括人类在内的其他生物体中是保守的。这个项目将产生重要的见解 将对遗传学、人类健康和进化产生广泛影响。

ABSTRACT Chromosome segregation errors can produce cells with an incorrect number of one or more chromosomes, known as aneuploidy. Aneuploidy is therefore a special class of mutation that can have immediate phenotypic effects. Although aneuploidy is detrimental during mammalian development, it is common in many cancers and a driver in the evolution of drug resistant tumors and fungal pathogens. A major unaddressed question is the degree to which different individuals vary in their ability to tolerate aneuploidy. Understanding how genetic differences influence aneuploidy tolerance has far reaching implications for genetics, human biology, and evolution. But studying this topic mammalian systems is extremely challenging, since it is not possible to systematically manipulate karyotypes in a large number of genetic backgrounds. Here we will address the fundamental question of how genetic variation influences the ability of cells to tolerate chromosome duplications, in the model eukaryote Saccharomyces cerevisiae. Using the power of yeast genetics, we adapted a method to duplicate specific yeast chromosomes in the near absence of selection. We will apply this method to explore the breadth and mechanisms of genetic variation in tolerating chromosome duplications (herein referred to as aneuploidy). Aim 1 will use this approach to duplicate each of the 16 chromosomes in yeast, in dozens of non-laboratory strains across the yeast phylogeny. Results will characterize the range of natural variation in aneuploidy tolerance and will test if this variation occurs sporadically due to rare alleles or persists across many strains within specific lineages. Preliminary results suggest lineage-specific variation in aneuploidy tolerance. Aim 2 will test if variations in aneuploidy sensitivity are due to differences in “generalized” aneuploidy tolerance, in which cells are sensitive regardless of which chromosome is duplicated, versus chromosome-specific sensitivities that are likely driven by the effects of duplicated genes encoded on those chromosomes. We will test how well chromosome-specific sensitivities are explained by an additive gene model that is based on measured fitness costs of the genes’ over-expression, measured here from a gene over-expression library expressed in each strain. Aim 3 will begin to uncover the physiological and genetic mechanisms for variable aneuploidy tolerance. We will first test our hypothesis that genetic variation in aneuploidy tolerance is due to variations in the ability to manage proteostasis stress. We will then use bulk- segregant mapping to study the genetic architecture of that variance and identify casual genes. Yeast is an outstanding model in which to study this fundamental question, since many cellular mechanisms and genetic principles are conserved in other organisms including humans. This project will generate important insights into aneuploidy tolerance that will have broad implications for genetics, human health, and evolution.