家马核基因组中线粒体核内插入序列分析

在各种真核生物核基因组中,存在一些由线粒体基因组转移进入核基因组中的DNA片段,这些被认为是分子化石的片段叫做线粒体核内插入序列(Numt)。由于Numt与真实的线粒体序列高度相似,因此它的存在必然会成为PCR扩增线粒体DNA的不利因素。利用已经公布的家马(Equus caballus)基因组序列(2007年9月公布,GenBank登录号为NC_009144-NC_009175)对家马Numt进行了深入分析,共发现200个可能的Numt,长度范围为29到3727bp,其中有10个的长度大于800bp。分析结果显示由于不存在线粒体控制区域的疑似Numt,因此对基于此区域的群体遗传学研究不会产生影响。本研究还发现在家马进化过程中,第1号和27号染色体更倾向于接受线粒体序列的转移。以上结果将为今后马科动物的研究提供重要的参考信息,有助于避免在线粒体DNA研究中由于Numt污染的存在而得出错误的实验结果。

Mitochondrial Introgressions into the Nuclear Genome of the Domestic Horse

The nuclear insertions of mitochondrial DNA (Numts), which originate from the integration of nuclear DNA by mtDNA, are found as molecular fossils in the nuclear genomes of various eukaryotes. Because integrated Numts tend to have a high sequence similarity to genuine organellar mtDNA sequences, inadvertent amplification of Numts can be a nuisance in studies of mtDNA variation. With the availability of the complete domestic horse genome sequence, we present the first comprehensive analysis of genome-wide distribution and frequency of Numts in the nuclear genome of domestic horse (Equus caballus). In the present paper, we detected 200 Numts ranging between 29 and 3 727 bp in size, which collectively representing only 0.002154% of the nuclear genome. Furthermore, ten of these segments were found to be longer than 800 bp. The absence of Numts in mitochondrial control region suggested that it would not influence the analysis of horse population genetics studies relating to this region. We also found that during horse evolution, Chromosomes 1 and 27 have been more susceptible to integration by Numts. The results in this study may provide valuable information for future mtDNA studies in Equidae species, including its use as a tool for avoiding Numt contaminations that may result in inauthentic results of experimentation.