西藏昌都藏族mtDNA高变Ⅰ和高变Ⅱ区序列多态性分析

Polymorphisms of mitochondrial DNA hypervariable regions HVR Ⅰ and HVR Ⅱ in Changdu Tibetan in China

目的探讨藏族人群线粒体DNA（mitochondrial DNA，mtDNA）控制区的两个高变区（hypervariable region，HVR）Ⅰ、Ⅱ的多态性。方法采用PCR扩增和末端标记荧光循环测序的方法，对97名西藏昌都地区藏族无关个体进行了序列分析。结果共观察到111个变异位点，序列变异包括了碱基的转换、颠换、插入、缺失等各种类型。其中，在HVRⅠ区（nt16024-nt 16365）内观察到68个变异位点，92种单倍型，基因多样性h值为0．9985；在HVRⅡ区（nt73-nt340）内观察到43变异位点，91种单倍型，基因多样性h值为0．9882；随机匹配概率在HVRⅠ和HVRⅡ区P值分别为0．0120和0．0118；联合两个高变区序列，可观察到97种不同的单倍型，随机匹配概率P值为0．0103。结论昌都藏族与其他群体比较有其独特的mtDNA序列遗传特点，与亚洲其他人种及白人有明显差异。mtDNA序列多态性在群体遗传学调查及法医学个体识别方面有广泛的应用前景。

Objective To analyze the sequence polymorphisms of mitochondrial DNA HVR Ⅰ and HVR Ⅱ in Tibetan population in Changdu area of Tibet. Methods mtDNAs obtained from 97 unrelated individuals were amplified and directly sequenced. Results One hundred and eleven variable sites were identified, including nucleotide transitions, transversions, insertions and deletions. In HVR Ⅰ region （nt16024-nt16365）, sixty-eight polymorphic sites and 92 haplotypes were observed, and the genetic diversity was 0.9985. In HVRⅡ region （nt73-nt340）, forty-three polymorphic sites and 91 haplotypes were detected, and the genetic diversity was 0. 9882. The random match probability of HVR Ⅰ and HVR Ⅱ regions were 0. 0120 and 0.0118, respectively. When the sequence analysis of HVR Ⅰ and HVR Ⅱ regions were combined, ninety-seven different haplotypes were found. The combined match probability of two unrelated persons having the same sequence was 0.0103. Conclusion There are some unique polymorphic loci in the Changdu Tibetan population. The results suggest that there are significant difference in the genetic structure in the mitochondrial DNA D-loop region between Changdu Tibetans and other Asian populations and Caucasians. Sequence pelymorphism in mitochondrial DNA HVR Ⅰand HVR Ⅱ can be used as a genetic marker for forensic individual identification and genetic analysis.