Mutation analysis of the APC gene in unrelated Korean patients with FAP: four novel mutations with unusual phenotype.
Germline mutations within the adenomatous polyposis coli (APC) gene are responsible for most cases of familial adenomatous polyposis (FAP), an autosomal dominantly inherited predisposition to colorectal cancer. To date more than 900 different APC germline mutations have been characterized worldwide demonstrating allelic heterogeneity. Here, we analyzed the APC gene in 23 DNA samples from unrelated Korean patients with the typical clinical symptoms of FAP by denaturing high-performance liquid chromatography (DHPLC) and direct sequencing. We identified 20 different APC sequence variants, including 9 truncating mutations, 1 missense mutation, 7 polymorphisms, and 3 intronic variants. Nine different truncating mutations, including four novel mutations (p.Leu180TyrfsX5, p.Gly567X, p.Ser1275PhefsX13, p.Leu1280CysfsX8), were detected. The most common mutation was a 5 bp deletion at codon 1,309 (p.Glu1309AspfsX4) as in Western studies. The next most common mutation was p.Ser1275PhefsX13 with a severe form of FAP with many extracolonic manifestations; this was a novel mutation identified in our study and may represent the second hot-spot mutation in a Korean population. Novel mutations are of particular interest because of the unusual phenotypic features shown by patients. In present study, we found new positions associated with thyroid cancer (codon 180) and desmoid tumor (codon 1,280), which have not been previously reported. The results of this molecular study have revealed the existence of novel pathogenic mutations in Korean patients with FAP. In addition to allowing phenotype-genotype correlations to be performed, these results are currently being used in genetic counseling and in patient care.
Division of Molecular Genetics, Department of Laboratory Medicine, Seoul Clinical Laboratories, Seoul Medical Science Institute, Yongsan-gu, Seoul, Korea.
Sung-Hee
SH
Han
Jae-Song
JS
Ryu
Young-Jin
YJ
Kim
Han-Ik
HI
Cho
Young-Ho
YH
Yang
Kyoung-Ryul
KR
Lee
D011125:Adenomatous Polyposis Coli / Q000235:genetics* / Q000473:pathology; D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics*; D000328:Adult; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D056726:Genetic Association Studies; D005838:Genotype; D006801:Humans; D007723:Korea; D008297:Male; D009154:Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011379:Prognosis
C555337:APC protein, human; D025601:Adenomatous Polyposis Coli Protein; D004273:DNA, Neoplasm