Positionaing Cloning of Lung Cancer Modifier Gene Par2

描述（由申请人提供）：本提案的目标是鉴定Par2基因，该基因负责BALB/cByJ小鼠对化学致癌物质的肺肿瘤抗性。虽然肺癌在很大程度上与吸烟有关，但有强有力的证据表明遗传易感性和基因-环境相互作用在肺癌的发展中。由于遗传异质性和环境因子暴露水平的巨大差异使得人类肺癌易感位点的鉴定变得困难，因此近交小鼠模型提供了一种鉴定候选肺癌修饰因子的有效手段。在A/J小鼠和BALB/cByJ小鼠之间，一个主要的数量性状位点（QTL）被命名为肺腺瘤抵抗基因2 (Par2)，它负责50%的肿瘤多样性变异。通过将高肺肿瘤易感性（A/J）等位基因替换到BALB/cJ小鼠遗传背景上的同源菌株的产生，证实了QTL定位结果。在本提案中，我们将通过生产亚同源小鼠品系逐步减少QTL区域，将其缩小到约0.2-0.5 cM的大小，从而精细绘制Par2 QTL。整个狭窄区域的DNA序列将通过完整的小鼠基因组数据库获得。将根据A/J小鼠和BALB/cJ小鼠之间已知或推断的功能和/或表达差异，鉴定目标区域的新基因和已知基因，并寻找候选基因。然后，通过构建A/J Par2等位基因取代BALB/cJ等位基因的敲入小鼠来评估候选Par2基因的功能作用。由此产生的小鼠将进行肺癌发生试验以确认Par2基因。由于Par2已被证明是Pas1 QTL的负修饰子，我们将在存在或不存在Pas1位点的情况下产生含有Par2位点的双同源菌株。比较双基因和单基因对肺肿瘤的反应将有助于确定相关基因座之间的相互作用。这些研究的意义在于，它们将确定Par2基因，其人类同源物可能使某些个体易患肺癌。

DESCRIPTION (provided by applicant): The goal of this proposal is to identify the Par2 gene, which is responsible for lung tumor resistance in the BALB/cByJ mouse to chemical carcinogens. Although lung cancer is largely associated with smoking, there is strong evidence for genetic susceptibility and gene-environment interactions in the development of lung cancer. Inbred mouse models offer an effective means of identifying candidate lung cancer modifiers since genetic heterogeneity and enormous variation in exposure levels to environmental agents makes it difficult to identify lung cancer susceptibility loci in humans. A major quantitative trait loci (QTL) locus named pulmonary adenoma resistance gene 2 (Par2) responsible for 50% of variance in tumor multiplicity between the A/J mouse and the BALB/cByJ mouse has been mapped to mouse chromosomes 18. The QTL mapping result has been confirmed by the production of congenic strains in which high lung tumor susceptibility (A/J) allele was substituted onto the genetic background of the BALB/cJ mouse. In this proposal, we will fine map the Par2 QTL by progressively reducing the QTL region through the production of subcongenic mouse strains to narrow it to a size of around 0.2-0.5 cM. DNA sequences of the entire narrowed region will be obtained through completed mouse genomic databases. New and known genes in the target region will be identified and candidate genes will be sought based on known or deduced function and/or differences in expression between A/J mice and BALB/cJ mice. The functional role of the candidate Par2 gene will then be evaluated by constructing knock-in mice with the A/J Par2 allele replacing the BALB/cJ allele. The resulting mouse will be subjected to lung carcinogenesis assay to confirm the Par2 gene. Since the Par2 has been shown to be a negative modifier of the Pas1 QTL, we will produce double congenic strains that contain the Par2 locus in the presence or absence of the Pas1 locus. Comparisons of lung tumor response among double and single congenics will allow definition of interactions between the loci involved. The significance of these studies is that they will identify the Par2 gene whose human homologue may predispose some individuals to lung cancer.