两个多发性内分泌腺瘤病2A型家系RET原癌基因突变方式的研究

Study of RET proto-oncogene mutations in two pedigrees affected with multiple endocrine neoplasia type 2A

目的探讨两个多发性内分泌腺瘤病2A型家系的RET原癌基因突变方式。方法提取2个家系成员外周血基因组DNA，对RET原癌基因外显子进行PCR扩增，PCR产物进行直接基因测序。首先对两个家系的先证者的RET原癌基因中发生突变率较高的第8、10、11、13、14、15和16这7个外显子的基因片段进行测序，再根据先证者发生突变的位点，对其家庭成员进行相应外显子测序。为排除合并其他位点的基因突变，对家系1中的先证者DNA的其余的14个外显子（第1、2、3、4、5、6、7、9、12、17、18、19、20、21）也进行了扩增测序。结果在家系1的3例患者（先证者及其一姐和一弟）及2名表型正常家系成员中，发现了RET原癌基因第11外显子存在1893-1895delCGA杂合突变，是一种新的突变类型。其他进行DNA测序的家庭成员未见以上突变。在家系2的2例患者（先证者及其兄）及3名表型正常家系成员，发现了RET原癌基因第11外显子存在Cys634Arg杂合突变，为已报道的发生率较高的一种突变类型。结论RET原癌基因第11外显子1893-1895delCGA杂合突变及Cys634Arg杂合突变，均为多发性内分泌腺瘤病2A型的致病基因，而前者是一种未见报道的新突变，丰富了人类基因突变谱。

Objective To study the pattern of RET proto-oncogene mutations in two pedigrees affected with multiple endocrine neoplasia type 2A （MEN2A）. Methods Peripheral blood samples were collected from members of the two pedigrees, with total genomic DNA extracted for polymerase chain reaction （PCR）. PCR products of 7 exons of the RET proto-oncogene （including exons 8, 10, 11, 13, 14, 15, 16） which have higher mutation rates were purified and subjected to direct sequencing. Suspected mutations in the 2 probands were verified in other members of the pedigrees. To exclude other mutations, PCR products of remaining 14 exons were sequenced in the proband from pedigree 1. Results A novel heterozygous mutation, 1893-1895delCGA, was detected in exon 11 of the RET proto-oncogene among 3 patients and 2 unaffected members from pedigree 1, while a heterozygous mutation, Cys634Arg, was detected in exon 11 among 2 patients and 1 unaffected family member from pedigree 2. Conclusion The heterozygous 1893-1895delCGA and Cys634Arg mutations of the RET proto-oncogene probably underlie the disease in the two pedigrees. Above discovery has enriched the human gene mutation database.