Tooth agenesis as a clinical marker for colon cancer

描述（由申请人提供）：这个R03申请的目标是确定结肠癌和牙齿发育之间的因果基因变异。结肠癌很常见，是世界上第二大致命癌症，全世界每年约有60万人死于结肠癌。牙齿发育不全被定义为不能长出一颗或多颗恒牙，是人类最常见的先天性异常。一份单一的报告显示，在一个四代芬兰家庭中，结肠癌和牙齿发育是分离的，这两种情况有共同的病因。然而，到目前为止，还没有系统的结肠癌家族牙齿发育的临床或分子研究来证实最初报告的发现，并在全基因组范围内发现导致组合表型的遗传变异。为此，我们检索了美国国立卫生研究院结肠癌家庭登记处的记录，并选择了20例结肠癌和牙齿发育不全的先证者，以及牙齿发育不全的家族史，用于下一代测序实验，以确定结肠癌和牙齿发育不全的因果基因变异。临床数据和DNA样本很容易在PI的实验室中获得。我们提出了两个目标来完成这个项目：(1)将对20个不相关先证者的DNA样本进行所有已知人类基因的全外显子组测序（WES），然后对捕获的目标进行大规模平行测序。WES是一种强大的方法，它彻底改变了我们识别致病突变的能力。变体的新颖性将通过使用公共数据库中可用的信息过滤变体来评估，不太可能引起疾病的变体将被过滤掉。生物信息学将用于候选基因的优先排序，基于

DESCRIPTION (provided by applicant): The goal for this R03 application is to identify causal gene variants linking colon cancer and tooth agenesis. Colon cancer is common and is the second most lethal cancer in the world, with approximately 600,000 related deaths/year worldwide. Tooth agenesis is defined as the failure to develop one or more permanent teeth, and is the most common congenital anomaly in humans. A single report showed the segregation of colon cancer and tooth agenesis in a four-generation Finnish family and suggested a common etiology between the two conditions. However, to date, there have been no systematic clinical or molecular studies of tooth agenesis in colon cancer families to confirm the findings of that initial report and to discover genetic variants contributing to a combined phenotype on a genome-wide scale. For this proposal, we have searched the records of the NIH Colon Cancer Family Registry and selected twenty probands presenting with colon cancer and tooth agenesis, and family history of tooth agenesis, for use in next generation sequencing experiments to identify causal gene variants linking colon cancer and tooth agenesis. Clinical data and DNA samples are readily available in the PI's laboratory. We propose two aims to accomplish this project: (1) DNA samples of the twenty unrelated probands will be subjected to whole exome sequencing (WES) of all known human genes followed by massively parallel sequencing of the captured targets. WES is a powerful approach that has revolutionized our ability to identify disease-causing mutations. Novelty of variants will be assessed by filtering th variants using information that are available in public databases and unlikely disease causing variants will be filtered out. Bioinformatics will be used for candidate gene prioritization, based on predicted functional impact and gene expression data; (2) Prioritized variants will be confirmed in probands and genotyped in selected relatives with tooth agenesis only using Sanger sequencing and/or Sequenom genotyping. The results of this study will allow the identification of gene(s) that are enriched with damaging mutations and thus likely to be contributing to the combined phenotype. Further, the results will delineate a broader phenotype spectrum to which tooth agenesis and colon cancer may belong, and determine if tooth agenesis may be considered an early clinical marker for colon cancer predisposition in susceptible families. The identified variants may be used as screening tools for increased colon cancer susceptibility in additional tooth agenesis families, allowing for improved identification o at-risk families, referral to genetic counseling, and ultimately cancer prevention. The study team presents the expertise and motivation necessary to lead the proposed research. This work will be the basis to a future R01 application to validate or find other variants in additional colon cancer families and tooth agenesis families, and to investigate the molecular mechanisms of the variants identified using in vitro and in vivo models. Finally, the results of this study may revea a paradigm-shifting approach with wide applicability in the dental profession, as dentists will play critical role in identifying families with tooth agenesis at risk for colon cancer.