一个家族性腺瘤性息肉病家系的APC基因突变分析

Analysis of APC gene mutation in a familial adenomatous polyposis pedigree

目的对1个家族性腺瘤性息肉病（familial adenomatous polyposis,FAP）家系的腺瘤性息肉病（adenomatons polyposis coli,APC）基因进行突变分析。方法通过临床表现、家族史、大肠息肉数、组织病理学等，临床诊断1例FAP患者。提取先证者外周血DNA，进行APC基因所有外显子的PCR扩增及序列分析，发现突变位点后，对先证者的家庭成员进行相应突变位点检测，并对相应PCR产物进行酶切验证，同时用酶切方法对100名无血缘关系的正常对照进行检测。结果该家系发现一新的无义突变：C．2891T〉G（L964X），该突变国际上未见报道。这一突变造成终止密码子提前出现，在100名无血缘关系的正常人中均未发现此突变。结论C．2891T〉G（L964x）为该家系的致病性突变。本研究采用测序技术和酶切方法相结合，确保了诊断的准确性。

Objective To analyze mutation of adenomatous polyposis coli （APC） gene in a family affected with familial adenomatous polyposis. Methods The diagnosis was made based on clinical manifestations, family history, presence of numerous polyps in the colon as well as pathological examination. Peripheral blood samples were collected, and genomic DNA was extracted. Potential mutation of the APC gene was detected by polymerase chain reaction （PCR） and DNA sequencing. After finding the mutation in the proband, the same mutation was screened among other family members. The mutation was also confirmed with PCR-restriction fragment length polymorphism （RFLP）, with which 100 unrelated healthy controls were examined. Results A novel heterozygous nonsense mutation c. 2891T〉G （L964X） of the APC gene was identified in this pedigree. The mutation has led to premature termination of translation. The same mutation was not detected among the 100 healthy controls. Conclusion The c. 2891T〉 G （L964X） of the APC gene probably underlies the familial adenomatous polyposis in this pedigree. The combined DNA sequencing and PCR-RFLP method is efficient and accurate for the diagnosis.