Further genetic analysis of the Mom1 locus

描述(申请人提供)：结直肠癌(CRC)是美国的主要恶性肿瘤之一，每年导致13万新发病例和5万多人死亡。值得注意的是，尽管在早期发现和治疗方面取得了进展，但在过去30年中，结直肠癌的发病率和死亡率保持相当稳定。为了开发有效的结直肠癌预防和治疗方法，癌症研究人员面临的一个紧迫挑战是识别和表征导致结直肠癌易感性的遗传因素。关键的研究工具是遗传定义的老鼠模型，如ApcMin/+鼠标。这一应用的主要研究人员和其他人已经使用致敏的Min小鼠定位了Most1基因座，这是小鼠四号染色体上的一个基因复合体，对Min诱导的肿瘤形成具有显著的抵抗力。我们已经在这个复合体中功能性地克隆了一个基因，分泌型磷脂酶Pla2g2a，它位于Mom1的近端。MOM1的末端修饰基因(S)位于大约8MB的区域。这项建议通过创建一组新的重组同源小鼠品系来扩展我们之前的工作，这些品系将被用于以高分辨率定位远端修饰基因，然后进行位置克隆。这项建议的第二个目的是通过创建一个有针对性的替换(来源于AKR菌株的)野生型Pla2g2a的拷贝到自然突变的C57BL/6遗传背景中来扩展我们以前对Pla2g2a的转基因研究。有一些证据表明突变的B6Pla2g2a蛋白保留了催化非依赖的功能，因此，在肿瘤健壮的B6遗传背景上对内源突变基因进行野生型替换应该可以更好地理解Pla2g2a在肿瘤耐药中的作用，因为野生型Pla2g2a的表达现在将在没有内源突变的B6Pla2g2a的情况下发生。

DESCRIPTION (provided by applicant): Colorectal cancer (CRC) is one of the major malignancies in the United States, accounting for 130,000 new cases and more than 50,000 deaths each year. Notably, the incidence and mortality rates from CRC have remained fairly constant over the past three decades despite advances in early detection and therapy. To develop effective prevention and therapeutic modalities for CRC an emergent challenge for cancer investigators is to identify and characterize the constellation of genetic factors that underlie CRC susceptibility. Key research tools are genetically defined mouse models such as the ApcMin/+ mouse. The principal investigator for this application and others have used the sensitized Min mouse to map the Mom 1 locus, a complex of genes on mouse chromosome four that confers significant resistance to Min-induced tumorigenesis. We have functionally cloned one gene in this complex, the secretory phospholipase Pla2g2a, which lies in the proximal region of Mom1. The distal modifier gene(s) of Mom1 lie in a region of approximately 8 MB. This proposal extends our previous work by creating a new panel of recombinant congenic mouse lines that will be used to map the distal modifier gene at high resolution, followed by its positional cloning. A second aim of this proposal is to expand upon our previous transgenic studies of Pla2g2a by creating a targeted replacement "knockin" of a wildtype copy of Pla2g2a (derived from the AKR strain) into the naturally mutant C57BL/6 genetic background. There is some evidence that the mutant B6 Pla2g2a protein retains catalytic-independent function, thus, wildtype replacement of the endogenous mutant genes on the tumor-robust B6 genetic background should provide a better understanding of Pla2g2a's role in tumor resistance as expression of wildtype Pla2g2a will now occur in the absence of endogenous mutant B6 Pla2g2a.