Parasitology Section, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia.
PLoS One. 2013 Sep 13;8(9):e73329. doi: 10.1371/journal.pone.0073329. eCollection 2013.
The typical mitochondrial (mt) genomes of bilateral animals consist of 37 genes on a single circular chromosome. The mt genomes of the human body louse, Pediculus humanus, and the human head louse, Pediculus capitis, however, are extensively fragmented and contain 20 minichromosomes, with one to three genes on each minichromosome. Heteroplasmy, i.e. nucleotide polymorphisms in the mt genome within individuals, has been shown to be significantly higher in the mt cox1 gene of human lice than in humans and other animals that have the typical mt genomes. To understand whether the extent of heteroplasmy in human lice is associated with mt genome fragmentation, we sequenced the entire coding regions of all of the mt minichromosomes of six human body lice and six human head lice from Ethiopia, China and France with an Illumina HiSeq platform. For comparison, we also sequenced the entire coding regions of the mt genomes of seven species of ticks, which have the typical mitochondrial genome organization of bilateral animals. We found that the level of heteroplasmy varies significantly both among the human lice and among the ticks. The human lice from Ethiopia have significantly higher level of heteroplasmy than those from China and France (Pt<0.05). The tick, Amblyomma cajennense, has significantly higher level of heteroplasmy than other ticks (Pt<0.05). Our results indicate that heteroplasmy level can be substantially variable within a species and among closely related species, and does not appear to be determined by single factors such as genome fragmentation.
双侧动物的典型线粒体 (mt) 基因组由一条单环染色体上的 37 个基因组成。然而，人体虱和人头虱的 mt 基因组广泛碎片化，包含 20 个微染色体，每个微染色体上有一到三个基因。异质性，即个体 mt 基因组中的核苷酸多态性，已被证明在人体虱的 mt cox1 基因中显著高于人类和其他具有典型 mt 基因组的动物。为了了解人体虱中的异质性程度是否与 mt 基因组碎片化有关，我们使用 Illumina HiSeq 平台对来自埃塞俄比亚、中国和法国的 6 只人体虱和 6 只人头虱的所有 mt 微染色体的整个编码区进行了测序。作为比较，我们还对 7 种蜱的 mt 基因组的整个编码区进行了测序，这些蜱具有双侧动物的典型线粒体基因组结构。我们发现，人体虱和蜱之间的异质性水平差异很大。来自埃塞俄比亚的人体虱的异质性水平明显高于来自中国和法国的人体虱（Pt<0.05）。蜱，A. cajennense，的异质性水平明显高于其他蜱（Pt<0.05）。我们的结果表明，异质性水平在一个物种内和密切相关的物种之间可能有很大的差异，并且似乎不是由基因组碎片化等单一因素决定的。
