Detecting APC Gene Mutations in Familial Adenomatous Polyposis (FAP)

Hereditary forms of colorectal cancer (CRC) account for up to 5% of total cases. Familial adenomatous polyposis (FAP) is an autosomal dominant condition affecting nearly 1 in 5000 people and accounts for only about 1% of all CRCs. It is characterized by the progressive development of hundreds to thousands of adenomatous colon polyps. The gene associated with FAP (APC) contains 15 coding exons. The mutation spectrum of the APC gene is broad in that 87% of causative mutations are point mutations (including other sequence variants) and around 10% to 15% are intragenic deletions and duplications. The strategy for molecular diagnostic testing for FAP involves initial full sequence analysis of APC for sequence variants followed by screening for deletion/duplications using microarray-based comparative genomic hybridization (array CGH) or Multiplex Ligation-dependent Probe Amplification (MLPA). Recently, next generation sequencing (NGS)-based targeted gene analysis has become clinically available for detection of point mutations and other sequence variants. This unit discusses detailed protocols for an NGS-based sequencing assay, PCR-based Sanger sequencing, and array CGH. © 2017 by John Wiley & Sons, Inc.