Objective To observe the mode of RET proto-oncogene mutation in a pedigree with multiple endocrine neoplasia type 2A (MEN2A).Methods Six members from a MEN2A family,including the proband,were enrolled.Genomic DNAs of these members were extracted from peripheral blood lymphocytes for polymerase chain reaction(PCR),PCR products of 21 exons of the RET proto-oncogene were purified and a direct gene sequence analysis was performed.DNA sequencing was performed on the related exon of the other family members after verifying the mutation site.Results The female proband sufferd from pheochromocytoma and medullary thyroid carcinoma since the age of 45,two missense mutations of TGC(Cys) to TCC(Ser) at codon 634 and CTG(Leu) to TTT(Phe) at codon 633 in exon 11 of the RET proto-oncogene were detected in the proband,while the other members remain unchanged.Conclusions Analysis of the RET proto-oncogene identifies a united mutation of TGC (Cys) to TCC (Ser) at codon 634 and CTG(Leu) to TTT(Phe) at codon 633 in the proband.The former is a proven mutation related to MEN2A,while the latter has never been reported before.%目的 探讨多发性内分泌腺瘤病2A型(MEN2A)的RET原癌基因突变方式.方法 一个MEN2A家系,提取包括先证者共6名成员的外周血淋巴细胞DNA,对先证者RET原癌基因的全部21个外显子进行聚合酶链反应(PCR),PCR产物进行直接基因测序分析,判定变异的位点及编码氨基酸序列的变化,测得突变所在的外显子后,将其他家系成员相应外显子的扩增产物进行测序.结果 该家系先证者系45岁起被先后确诊为肾上腺嗜铬细胞瘤和甲状腺髓样癌的女性患者.通过基因测序分析发现了该先证者RET原癌基因第11号外显子存在Cys (TGC) 634 Ser(TCC)错义突变同时合并Leu(CTG) 633 Phe(TTT)错义突变,其他家系成员基因测序结果未见异常.其中测序发现的突变点与Cariff医学遗传学院人类基因突变数据库收录的MEN2A相关的RET原癌基因突变比较,Leu(CTG) 633 Phe(TTT)错义突变为新突变点,而Cys(TGC)634 Ser(TCC)错义突变于1993年由Mulligan等首次报道,目前尚未发现同时合并这两种错义突变的报道.结论 本研究证实先证者存在外显子1 1的Cys(TGC) 634Ser(TCC)和Leu(CTG)633 Phe(TTT)两个联合的错义突变,前者即可导致其MEN2A的发生,第633位密码子的错义突变则未见报道.
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