Further genetic analysis of the Mom1 locus

描述（由申请人提供）：结直肠癌（Colorectal cancer， CRC）是美国的主要恶性肿瘤之一，每年有130,000例新发病例和超过50,000例死亡。值得注意的是，尽管在早期发现和治疗方面取得了进展，但在过去三十年中，CRC的发病率和死亡率仍然相当稳定。为了开发有效的CRC预防和治疗模式，癌症研究者面临的一个紧迫挑战是识别和表征CRC易感性的遗传因素。关键的研究工具是遗传定义的小鼠模型，如ApcMin/+小鼠。这项应用的首席研究员和其他人已经使用敏化的Min小鼠来绘制Mom 1位点，这是小鼠4号染色体上的一个基因复合体，赋予Min诱导的肿瘤发生显著的抗性。我们已经克隆了这个复合体中的一个基因，分泌磷脂酶Pla2g2a，它位于Mom1的近端区域。Mom1的远端修饰基因位于大约8 MB的区域。该建议扩展了我们之前的工作，创建了一个新的重组同源小鼠系，将用于高分辨率地绘制远端修饰基因，然后进行其位置克隆。本提案的第二个目的是扩展我们之前对Pla2g2a的转基因研究，通过将Pla2g2a的野生型拷贝（来自AKR菌株）靶向“敲入”到自然突变的C57BL/6遗传背景中。有证据表明突变体B6 Pla2g2a蛋白保留了不依赖于催化的功能，因此，在肿瘤健壮的B6遗传背景上替换内源性突变基因的野生型应该可以更好地理解Pla2g2a在肿瘤抗性中的作用，因为在缺乏内源性突变体B6 Pla2g2a的情况下，野生型Pla2g2a的表达将会发生。

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.