一个原发性肌张力障碍家系TOR1A基因的突变鉴定与产前诊断

Detection and prenatal diagnosis of TORIA gene mutation in a Chinese family affected with dystonia

目的应用PCR毛细管电泳法检测1个原发性肌张力障碍（primary torsion dystonia，PTD）家系TOR1A（TorsinA）基因的突变，为其家系的产前诊断依据提供。方法收集该家系先证者的外周血及羊水样本，应用PCR扩增样本TORlA基因第5外显子及侧翼DNA序列，之后通过琼脂糖电泳、荧光标记、毛细管电泳分离进行片段分析。用Sanger测序法验证TOR1A基因的突变。结果荧光标记片段毛细管电泳分离法和DNA直接测序均提示先证者及胎儿携带TOR1A基因-907—909delGAG（P．Glu303del）缺失突变，推测胎儿罹患与先证者相同的张力障碍的可能性较大。结论TOR1A基因C．907—909delGAG突变是该家系的致病原因。针对TOR1A基因的微小缺失型突变，可采用PCR结合毛细管电泳法进行DNA片段的分析。

Objective To explore the feasibility of using PCR based capillary electrophoresis method to analysis mutation of the TORJA gene in a family affected with primary torsion dystonia （PTD）. Methods Peripheral blood sample was collected from proband and amnionic fluid from her fetus for the extraction of DNA. The 5th exon of the TOR]A gene and its flanking sequences were amplified with PCR and analyzed with agarose electrophoresis, fluorescence labeled fragment analysis and Sanger sequencing. Results Fluorescence labeled fragment analysis was performed through capillary electrophoresis, which showed that the proband carried a e. 907909delGAG （p. Glu303del） deletional mutation of the TORIA gene. The result was verified by Sanger sequencing. The fetus DNA was also found with the same mutation by capillary electrophoresis, inferring that the fetus was probably affected with the disease. Conclusion The mutation of c. 907 909delGAG of the TOR1A gene was speculated as pathologic cause of proband in this family. Fragment analysis by capillary electrophoresis combined with DNA sequencing is an efficient test for small deletional mutations and feasible for its prenatal diagnosis.