Genetic Analysis of Chromosomal Instability

癌细胞在许多重要特征上不同于其正常细胞对应物，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，我们发现DNA损伤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DNA损伤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。 本提案中描述的实验旨在确定导致这种异常染色体表型的遗传机制。 在具体目标1中，我们将描述电离辐射产生的染色体重排，这些重排与延迟复制时间和延迟有丝分裂凝聚有关。 在特定目标2和3中，我们将使用染色体工程策略，结合体细胞和分子遗传学，以产生显示这种异常染色体表型的特定染色体缺失和重排。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。

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 DNA damage generates chromosomes with this phenotype. Our findings support a model in which the chromosomal instability found in tumor cells, and in cells with DNA damage, stems from a defect in the replication timing of certain chromosomal rearrangements. The experiments described in this proposal are designed to determine the genetic mechanisms responsible for this abnormal chromosomal phenotype. In Specific Aim 1, we will characterize the chromosomal rearrangements generated by ionizing radiation that are associated with delayed replication timing and delayed mitotic condensation. In Specific Aims 2 and 3, we will use chromosome engineering strategies, combined with somatic cell and molecular genetics, to generate specific chromosome deletions and rearrangements that display this abnormal chromosomal 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.