Genetic Analysis of Delayed Chromosome Replication Timing

描述(由申请人提供)：癌细胞在许多重要特征上与正常细胞不同，包括分化丧失、基因组不稳定性增加和药物敏感性降低。毫不奇怪，基因改变发生在大多数癌细胞中，如果不是所有的话，并且被认为是这些表型改变的核心。此外，遗传不稳定性被认为是产生癌细胞中发生的多种基因变化所必需的。我的实验室使用体细胞和分子遗传学来识别和描述在肿瘤细胞中发现的导致异常细胞表型的基因变化。通过使用这种方法，我的实验室已经发现了一种以前未知的染色体异常，它与某些染色体重排有关。这种染色体表型的特征是有丝分裂染色体凝集延迟，染色体复制时间延迟，染色体显著不稳定。具有这种表型的染色体在肿瘤来源的细胞系和原发肿瘤中很常见。此外，我们还发现，将细胞暴露在电离辐射下会产生具有这种表型的染色体。我们的发现支持这样一个模型，即在肿瘤细胞和暴露于电离辐射的细胞中发现的染色体不稳定性，源于某些染色体重排的复制时机缺陷。最近，我们开发了一种染色体工程策略，允许我们以高效和可重复的方式生成具有这种延迟复制和凝集表型的染色体。我们的发现表明，在所有的随机染色体易位中，约5%的人表现出这种异常表型。此外，在某些平衡易位上，只有一条衍生染色体表现出表型，这表明顺式作用机制导致了这种异常的染色体表型。这项建议的主要目标是描述这种顺式作用机制的功能，以延迟整个染色体的复制时间。这项建议利用‘染色体工程’策略，结合体细胞和分子遗传学方法，产生并表征具有这种延迟复制和凝聚表型的染色体。这些研究的长期目标是确定导致染色体不稳定的分子机制，染色体不稳定是在癌细胞中发现的最常见的遗传不稳定类型之一。与公共卫生相关：几乎所有类型的癌症都会发生基因变化。此外，不断进化的癌细胞基因组表明，潜在的遗传不稳定是存在的，并对这些正在进行的遗传变化负责。这项建议利用‘染色体工程’，结合体细胞和分子遗传学方法，来描述导致癌症遗传不稳定的机制之一。

DESCRIPTION (provided by applicant): Cancer cells differ from their normal cellular counterparts in many important characteristics, including loss of differentiation, increased genomic instability, and decreased drug sensitivity. Not surprisingly, genetic alterations occur in most, if not all cancer cells, and are thought to lie at the heart of these phenotypic alterations. Furthermore, genetic instability is thought to be required to generate the multiple genetic changes that occur in cancer cells. My laboratory uses somatic cell and molecular genetics to identify and characterize genetic alterations found in tumor cells that induce abnormal cellular phenotypes. By utilizing this approach, my lab has identified a previously unknown chromosomal abnormality that is associated with certain chromosomal rearrangements. This chromosomal phenotype is characterized by a delay in mitotic chromosome condensation, a delay in the chromosome replication timing, and significant chromosomal instability. Chromosomes with this phenotype are common in tumor derived cell lines and in primary tumors. Furthermore, we have found that exposing cells to ionizing radiation generates chromosomes with this phenotype. Our findings support a model in which the chromosomal instability found in tumor cells, and in cells exposed to ionizing radiation, stems from a defect in the replication timing of certain chromosomal rearrangements. Recently, we developed a chromosome engineering strategy that allows us to generate chromosomes with this delayed replication and condensation phenotype in an efficient and reproducible manner. Our findings indicate that ~5% of all random chromosome translocations display this abnormal phenotype. In addition, on certain balanced translocations only one of the derivative chromosomes displays the phenotype, indicating that a cis-acting mechanism is responsible for this abnormal chromosomal phenotype. The primary goal of this proposal is to characterize this cis-acting mechanism that functions to delay the replication timing of entire chromosomes. This proposal utilizes `chromosome engineering' strategies, combined with somatic cell and molecular genetic approaches, to generate and characterize chromosomes with this delayed replication and condensation phenotype. The long-term goal of these studies is to define the molecular mechanisms responsible for chromosomal instability, one of the most common types of genetic instabilities found in cancer cells. PUBLIC HEALTH RELEVANCE: Genetic changes occur in virtually all types of cancers. In addition, the continuously evolving genomes of cancer cells suggest that an underlying genetic instability is present and responsible for these ongoing genetic changes. This proposal utilizes `chromosome engineering', combined with somatic cell and molecular genetic approaches, to characterize one of the mechanisms responsible for genetic instability in cancer.