The overall goal of the proposed study is to identify new genes harboring rare mutations that considerably increase the risk of colorectal cancer (CRC). These mutations can underlie the observed familial aggregation of Lynch syndrome-like colorectal cancer cases called Familial Colorectal Cancer Type X (FCCTX). FCCTX is a Mendelian cancer syndrome with dominant mode of inheritance and incomplete penetrance. The first aim of the mentored-phase of this application is to identify novel candidate genes associated with risk of colorectal cancer in FCCTX patients using selective capture of protein-coding sequences in the human genome ("exome") followed by massively parallel resequencing of 10 patients with FCCTX. This approach has recently been successful in identifying novel genes causing Mendelian diseases. The identified candidate variants will be genotyped in the family members of the individuals with sequenced exomes for segregation analysis. During independent (R00) phase, the candidate genes will be resequenced in a large number of colorectal cancer cases and controls to find the spectrum of mutations in sporadic colorectal cancer and their presence in general population. In addition, the candidate genes will be resequenced in a large cohort of FCCTX families to find other individuals carrying mutations in these genes. The new genes and potentially pathways involved into development of colorectal cancer can become potential targets for colorectal cancer therapy. The proposed study represents also a proof of concept for the new strategy of exome resequencing for detecting of cancer predisposing genes. The low-cost, high throughput technologies for exome resequencing may facilitate the discovery of new candidate genes and mutations in familial cancer. PUBLIC HEALTH RELEVANCE: The identification of novel genes and mutations associated with risk of hereditary colorectal cancer is likely to have a significant impact on cancer management and prevention in families carrying these mutations. It can also advance our understanding of colorectal cancer biology and has the potential to lead to new treatments.