Detection of APC gene germline mutation in Chinese familial adenomatous polyposis by direct sequencing in combination with multiplex ligation-dependent probe amplification

Abstract

To investigate the characteristics of APC gene germline mutation in Chinese patients with familial adenomatous polyposis (FAP). The genomic DNA was extracted from peripheral venous blood drawn from probands of 14 Chinese FAP families from Beijing, Hebei, Henan, Anhui, Inner Mongolia, Shanxi and Fujian. The APC gene was amplified by PCR and underwent direct sequencing. Large fragment deletion was detected by multiplex ligation-dependent probe amplification (MLPA) only in micromutation-negative samples found by sequencing. APC gene micromutations were found in 9 probands and the micromutation detection rate was 64.3%, including 6 frameshift mutations, 2 splicing mutations and 1 nonsense mutation. Large fragment deletions of APC gene were detected in 2 probands (14.3%). The total mutation detection rate of micromutation and large fragment deletion was 78.6%. Four novel micromutations and 2 novel large fragment deletions were found, including c.2336-2337insT, c.3923-3929delAAGAAAA, c.532-2A > T, c.4179-4180GAdelinsT, large fragment deletions of exons 11 and 10A and large fragment deletion of exon 15 start. In Chinese FAP patients, the germline mutation type of APC gene is variable; the majority is of frameshift mutation. The most common mutation site is exon 15. The mutation detection rate of APC gene can be boosted effectively by direct sequencing in combination with MLPA.