The role of cohesion fatigue in chromosome instability

描述(申请人提供)：染色体不稳定(CIN)是几种人类健康问题的重要组成部分，包括癌症、出生缺陷和不孕不育。戈尔布斯基实验室发现了一种新的CIN来源，称为凝聚力疲劳。凝聚力疲劳是指延迟到中期的细胞中姐妹染色单体的渐进性、非同步分离。这个项目的总体目标是绘制凝聚力疲劳的下游后果图，染色单体放弃凝聚力的机制，以及调节细胞对凝聚力疲劳敏感性的上游途径。在目标1中，将使用单细胞水平和群体水平的先进显微镜来追踪因凝聚力疲劳而引起的染色体异常。凝聚力疲劳有可能同时产生在肿瘤发生过程中经常出现的两种类型的大染色体异常，即整个染色体数量的变化(非整倍体)和大片段染色体复制、缺失和易位。此外，凝聚力疲劳极有可能导致微核的形成，微核已被认为是大规模DNA损伤的部位。目的2将通过锁定粘附素蛋白复合体的单个关节的实验来确定凝聚力疲劳过程中粘附素的释放机制。此外，定量质谱学将被用来分析在衔接疲劳期间在翻译后修饰中被移除或改变的粘附素成分。目标3将绘制调节对凝聚力疲劳敏感性的上游通路，集中在转化细胞中可能加剧CIN的缺陷。转化的细胞经常表现出细胞周期调节的缺陷，而凝聚力基因是人类肿瘤中最常见的突变基因之一。因此，转化的细胞可能对凝聚力疲劳高度敏感。这一目标将测试细胞周期调节因子的变化如何导致中期延迟，以及这些延迟如何与纺锤体微管动力学和染色体凝聚力中的转化相关缺陷协同作用，以促进凝聚力疲劳。目的4将凝聚力疲劳的分析扩展到芽期酵母，以检验凝聚力疲劳调节因子在有丝分裂中的保守性，并检验凝聚力疲劳如何导致同源染色体在减数分裂过程中过早丧失凝聚力的具体假设。最近的证据表明，染色体凝聚力的衰退是母体年龄效应的一个因素，即老年妇女的卵母细胞显示非整倍体的发生率大大增加。在哺乳动物配子中，凝聚力疲劳可能是减数分裂非整倍体的一个重要原因，导致出生缺陷和不育。

DESCRIPTION (provided by applicant): Chromosome instability (CIN) is an important component in several human health problems including cancer, birth defects, and infertility. The Gorbsky lab discovered a new source of CIN that was termed cohesion fatigue. Cohesion fatigue is the progressive, asynchronous separation of sister chromatids in cells delayed at metaphase. The overall goals of this project are to map the downstream consequences of cohesion fatigue, the mechanisms by which chromatids surrender cohesion, and the upstream pathways that modulate the cell sensitivity to cohesion fatigue. In Aim 1, advanced microscopy at both the single cell level and population level will be used to track the chromosome abnormalities that arise from cohesion fatigue. Cohesion fatigue has the potential to simultaneously generate the two types of gross chromosome aberrations that often arise during oncogenesis, changes in whole chromosome number (aneuploidy) and large segmental chromosome duplications, deletions, and translocations. In addition, cohesion fatigue is highly likely to lead to the formation of micronuclei, which have been implicated as sites of massive DNA damage. Aim 2 will determine the mechanisms of cohesin release during cohesion fatigue through experiments that lock individual joints of the cohesin protein complex. In addition, quantitative mass spectrometry will be used to analyze cohesin components that are removed or altered in their post-translational modifications during cohesion fatigue. Aim 3 will map the upstream pathways that regulate sensitivity to cohesion fatigue, concentrating on defects in transformed cells that may exacerbate CIN. Transformed cells often exhibit defects in cell cycle regulators, and cohesion genes are among the most often mutated in human tumors. Thus, transformed cells may be highly susceptible to cohesion fatigue. This aim will test how alterations of cell cycle regulators induce metaphase delays and how these delays synergize with transformation-associated defects in spindle microtubule dynamics and chromosome cohesion to promote cohesion fatigue. Aim 4 extends the analysis of cohesion fatigue to budding yeast to examine the conservation of cohesion fatigue regulators in mitosis and to test specific hypotheses about how cohesion fatigue contributes to premature loss of cohesion between homologous chromosomes during meiosis. Recent evidence implicates decay in chromosome cohesion as a contributor to the maternal age effect, whereby the oocytes of older women show a greatly increased incidence of aneuploidy. In mammalian gametes, cohesion fatigue may be an important causative factor in meiotic aneuploidy, contributing to birth defects and infertility.