Genetic Analysis of Chromosomal Instability

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，DNA损伤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DNA损伤细胞中发现的染色体不稳定，源于某些染色体重排的复制时机缺陷。这项建议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，我们将描述由电离辐射产生的染色体重排，这些重排与延迟的复制时间和延迟的有丝分裂凝聚有关。在特定的目标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，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。

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.