Identification of mutation in 3'-end of exon 15 of APC gene in familial adenomatous polyposis patients

Familial adenomatous polyposis (FAP) is a hereditary precancerous syndrome and is characterized by the manifestation of adenomatous polyps in the colon and rectum at an early age. Germline mutations of APC gene cause FAP. This study aimed to investigate about the part of 3'-end of exon 15 of APC gene in FAP patients in Guilan, Ilam and Lorestan province in 2018.

In this descriptive cross-sectional study, 18 FAP patients were recognized and Blood sampling was done. After DNA extraction, a part 3'-end of exon 15 of APC gene was amplified by PCR method and underwent direct sequencing.

In this study one nonsense mutation (c.4606G>T, p.E1536X) in a classic FAP patient and one missense mutation (c.5465T>A, p.V1822D) in an AFAP as homozygote and four classic FAP patients as heterozygote was observed. Also, four silent mutations p.T1493T, p.G1678G, p.S1756S and p.P1960P were identified in these FAP patients.

It seems that mutation E1536X is the main reason of disease in a patient with severe polyposis. Also, mutation V1822D as homozygous can cause AFAP; but for classic FAP development a more destructive mutation is needed along with this mutation.