Genetic Analysis of Delayed Chromosome Replication Timing

描述（由申请人提供）：癌细胞与其正常细胞对应物在许多重要特征上不同，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）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鉴定和表征在肿瘤细胞中发现的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个以前未知的染色体异常，与某些染色体重排。这种染色体表型的特征在于有丝分裂染色体浓缩延迟、染色体复制时间延迟和显著的染色体不稳定性。具有这种表型的染色体在肿瘤衍生细胞系和原发性肿瘤中很常见。此外，我们还发现，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了一个模型，其中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的缺陷。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重复的方式产生具有这种延迟复制和浓缩表型的染色体。我们的研究结果表明，约5%的随机染色体易位显示这种异常表型。此外，在某些平衡易位，只有一个衍生染色体显示表型，表明顺式作用机制是负责这种异常的染色体表型。这项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。这项建议利用“染色体工程”战略，结合体细胞和分子遗传学方法，以产生和表征具有这种延迟复制和浓缩表型的染色体。这些研究的长期目标是确定染色体不稳定性的分子机制，这是癌细胞中最常见的遗传不稳定性之一。公共卫生相关性：几乎所有类型的癌症都会发生遗传变化。此外，癌细胞基因组的不断演变表明，潜在的遗传不稳定性是存在的，并负责这些正在进行的遗传变化。这项建议利用“染色体工程”，结合体细胞和分子遗传学方法，来确定癌症遗传不稳定性的机制之一。

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.