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Clin Genet. 2015 Oct;88(4):360-5. doi: 10.1111/cge.12503. Epub 2014 Oct 14.

APC promoter 1B deletion in seven American families with familial adenomatous polyposis.

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Huntsman Cancer Institute.
Division of Gastroenterology.
Division of Genetic Epidemiology, Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA.


Familial adenomatous polyposis (FAP) is a colorectal cancer predisposition syndrome caused by mutations in the adenomatous polyposis coli (APC) gene. Clinical genetic testing fails to identify disease causing mutations in up to 20% of clinically apparent FAP cases. Following the inclusion of multiplex ligation-dependent probe amplification (MLPA) probes specific for APC promoter 1B, seven probands were identified with a deletion of promoter 1B. Using haplotype analysis spanning the APC locus, the seven families appear to be identical by descent from a common founder. The clinical phenotype of 19 mutation carriers is classical FAP with colectomy at an average age of 24. The majority of cases had a large number of duodenal and gastric polyps. Measurements of allele-specific expression of APC mRNA using TaqMan assay confirmed that relative expression in the allele containing the promoter 1B deletion was reduced 42-98%, depending on tissue type. This study confirms the importance of APC promoter deletions as a cause of FAP and identifies a founder mutation in FAP patients from the United States.


APC; APC promoter 1B; allelic imbalance; colon cancer; familial adenomatous polyposis; founder mutation

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