X-连锁迟发性脊柱骨骺发育不良家系TRAPPC2基因突变分析

Detection of TRAPPC2 gene mutation in a Chinese pedigree of X-linked spondyloepiphysealdysplasia tarda

目的探讨使用PCR为基础的毛细管电泳法对1个中国X-连锁迟发性脊椎骨骺发育不良（X-SEDT）家系进行基因突变分析和携带者筛查的可行性。方法收集X-SEDT家系6名成员外周血样本，PCR扩增TRAPPC2基因第3、4、5和6外显子及侧翼DNA序列，采用琼脂糖电泳检测、荧光标记片段毛细管电泳分离方法进行片段分析，同时进行PCR产物直接毛细管电泳测序，检测TRAPPC2基因突变情况；使用荧光标记片段法进行携带者筛查，DNA直接测序对筛查结果进行验证。结果先证者和先证者母亲分别携带TRAPPC2基因c．262_266ddGACAT（D88del；189fXl2）缺失突变和杂合缺失突变，该突变在中国群体中为首次报道，先证者2个姐妹筛查结果显示，先证者大妹妹携带c．262_266delGACAT缺失杂合突变，先证者小妹妹未携带此突变。结论TRAPPC2基因。262-266delGACAT突变是该X-SEDT家系的致病原因，对TRAPPC2基因的微小缺失型突变，采用PCR结合毛细管电泳法进行DNA测序和片段分析可用于X-SEDT分子诊断和携带者筛查。

Objective To identify the mutation of trafficking protein particle complex 2 （TRAPPC2） gene in a large Chinese pedigree with X-linked spondyloepiphyseal dysplasia tarda by the PCR-based capillary electrophoresis methods. Methods The blood samples were collected from a large Chinese pedigree of three generations with six affected persons with X-SEDT. Four exons comprising the TRAPPC2 gene open reading frame as well as their exon/intron boundaries were analyzed by argrose eleetrophoresis and bi- directional direct sequencing of PCR products. Fluorescence labeled fragment analysis was performed by capillary electrophoresis. Results A 5-bp deletion mutation of TRAPPC2 gene in exon 5, c. 262_ 266de1GACAT （D88del; I89fX12） ,was identified in the proband and his unaffected mother（ a heterozygote） in the Chinese family with X-SEDT, but no other sequence change occurring in exons 3, 4 and 6 was detected. The old sister of proband was determined being carriers because she carries the deletion fragment allele of exon 5 PCR product and the young sister being normal individuals because she carries the wild allele of TRAPPC2 gene. Conclusions The mutation c. 262_266delGACAT （D88del; I89fX12） of TRAPPC2 gene was firstly reported in Chinese people. The mutation of e. 262 266deIGACAT（ D88del; I89fX12） in TRAPPC2 gene may be the pathologic cause of the patients in the X-SEDT pedigree. Fragment analysis combined with DNA sequencing by capillary electrophoresis method is effective laboratory test in the small deletion mutation analysis and carriers screening in X-SEDT family.