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，如果不是所有的癌细胞中，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遗传变化所必需的。我的实验室使用体细胞和分子遗传学来识别和表征肿瘤细胞中诱导异常细胞表型的遗传改变。通过利用这种方法，我的实验室已经确定了一种以前未知的与某些染色体重排相关的染色体异常。这种染色体表型的特征是有丝分裂染色体凝聚延迟，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衍生细胞系和原发肿瘤中很常见。此外，我们发现将细胞暴露于电离辐射会产生具有这种表型的染色体。我们的研究结果支持一个模型，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间缺陷。最近，我们开发了一种染色体工程策略，使我们能够以有效和可复制的方式产生具有这种延迟复制和冷凝表型的染色体。我们的研究结果表明，约5%的随机染色体易位表现出这种异常表型。此外，在某些平衡易位中，只有一条衍生染色体显示出这种表型，表明一种顺式作用机制导致了这种异常的染色体表型。本建议的主要目标是表征这种顺式作用机制，其功能是延迟整个染色体的复制时间。该建议利用“染色体工程”策略，结合体细胞和分子遗传学方法，产生和表征具有这种延迟复制和冷凝表型的染色体。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，染色体不稳定是癌细胞中最常见的遗传不稳定类型之一。公共卫生相关性：基因变化几乎发生在所有类型的癌症中。此外，癌细胞不断进化的基因组表明，存在潜在的遗传不稳定性，并对这些持续的遗传变化负责。该建议利用“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.