Spindle Assembly Checkpoint, Chromosomal Instability, and Cancer

描述（由申请人提供）：非整倍性是绝大多数人类实体肿瘤的标志。有丝分裂检查点基因（如BUB1、BUBR1或MAD2）的突变已被证明与非整倍体的产生有关。这些检查点基因产物形成了一个复杂的信号网络，称为纺锤体组装检查点（SAC），它延迟姐妹染色单体的分离，直到所有染色体都正确地附着在有丝分裂纺锤体上并在中期板上对齐。来自酵母菌等低等生物的研究已经清楚地表明，检查点功能的丧失会导致染色体不稳定，表现为染色体的增加或减少。从酵母和高等真核生物的分析中出现了更详细的SAC分子图谱。然而，SAC及其各个组成部分在机体水平上的功能仍有待阐明。同样，缺乏哺乳动物SAC的机械解剖。为了开始对哺乳动物中的SAC进行分子解剖，并确定其在防止染色体不稳定和致癌转化方面的功能，我们产生了不同程度的SAC缺陷小鼠品系。这些菌株是securin缺失、非磷酸化分离酶敲除蛋白和mad2非抑制Cdc20敲除蛋白（AAA-Cdc20）。我们发现我们的AAA-Cdc20小鼠易患肿瘤。我们建议解决AAA-Cdc20促进肿瘤发生的机制以及p53在限制SAC突变体肿瘤发展中的作用。公共卫生相关性：该项目侧重于纺锤体组装检查点在预防基因组不稳定和肿瘤发生中的作用。所提出的实验结果可能有助于癌症的治疗和诊断。

DESCRIPTION (provided by applicant): Aneuploidy is a hallmark of the vast majority of human solid tumors. Mutations in mitotic checkpoint genes such as BUB1, BUBR1 or MAD2 have been shown to be involved in generation of aneuploidy. These checkpoint gene products forms an intricate signaling network called spindle assembly checkpoint (SAC) that delays the segregation of sister chromatids until all chromosomes are properly attached to the mitotic spindle apparatus and aligned at the metaphase plate. Work from lower organisms such as yeast has clearly demonstrated that loss of the checkpoint function causes chromosomal instability manifested as gains or losses of chromosomes. A more detailed molecular picture of SAC is emerging from analyses in both yeast and higher eukaryotes. However, the function of SAC and its various components at an organismal level remains to be elucidated. Likewise, mechanistic dissection of SAC in mammals is lacking. In an effort to start to molecularly dissect SAC in mammals and to determine its function in preventing chromosomal instability and oncogenic transformation, we generated mouse strains that are defective in SAC to different extents. These strains are securin deletion, non-phosphorylable separase knockin, and Mad2-noninhibitable Cdc20 knockin (AAA-Cdc20). We have found that our AAA-Cdc20 mice were tumor-prone. We propose to address the mechanism by which AAA-Cdc20 promotes tumorigenesis and the role of p53 in limiting tumor development in SAC mutants. PUBLIC HEALTH RELEVANCE: This project focuses on spindle assembly checkpoint's role in the prevention of genome instability and tumorigenesis. Results obtained from the proposed experiments may help the treatment and diagnosis of cancer.