Positionaing Cloning of Lung Cancer Modifier Gene Par2

描述(申请人提供)：这项建议的目标是确定PAR2基因，该基因负责BALB/cByJ小鼠对化学致癌物的肺癌抗性。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生发展中起作用。近交系小鼠模型提供了一种识别候选肺癌修饰基因的有效手段，因为遗传异质性和环境因素暴露水平的巨大差异使得识别人类肺癌易感基因变得困难。A/J小鼠和BALB/cByJ小鼠之间肿瘤多发性差异的50%是由肺腺瘤抗性基因2(PAR2)决定的，该QTL被定位在小鼠的18号染色体上。BALB/CJ小鼠的遗传背景上替换了高肺肿瘤易感性(A/J)等位基因的QTL定位结果得到了证实。在这项建议中，我们将通过生产亚基因小鼠品系逐步减少QTL区域，将其缩小到0.2-0.5厘米左右，从而精细定位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小鼠之间已知或推导的功能和/或表达差异，识别靶区新的和已知的基因，并寻找候选基因。然后将通过构建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。得到的小鼠将接受肺癌致癌实验，以确认PAR2基因。由于PAR2已被证明是PAS1 QTL的负修饰，我们将产生含有PAR2基因座的双同基因菌株，无论是否存在PAS1基因座。对双基因和单基因肺癌反应的比较将有助于确定所涉及的基因座之间的相互作用。这些研究的意义在于，他们将确定PAR2基因，其人类同源基因可能使一些人容易患肺癌。

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.