Mukai Yahiro, Horie Masayuki, Tomonaga Keizo
Laboratory of RNA Viruses, Department of Virus Research, Institute for Frontier Life and Medical Sciences (InFRONT), Kyoto University, Kyoto 606-8507, Japan.
Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.
J Vet Med Sci. 2018 Aug 30;80(8):1356-1363. doi: 10.1292/jvms.18-0211. Epub 2018 Jul 5.
Endogenous bornavirus-like elements (EBLs) are sequences derived from bornaviruses (the family Bornaviridae) that are integrated into animal genomes. They are formed through germline insertions of segments of bornaviral transcripts into animal genomes. Because EBLs are molecular fossils of bornaviruses, they serve as precious sources of information to understand the evolutionary history of bornaviruses. Previous studies revealed the presence of many EBLs in bat genomes, especially in vesper bats, and suggested the long-term association between bats and bornaviruses. However, insertion dates of EBLs are largely unknown because of the limitations of available bat genome sequences in the public database. In this study, through a combination of database searches, PCR, and sequencing approaches, we systematically determined the gene orthologies of 13 lineages of EBLs in bats of the genus Myotis and Eptesicus and family Vespertilionidae. Using the above data, we estimated their insertion dates: the EBLs in vesper bats were inserted approximately 14.2 to 53 million years ago. These results suggest that vesper bats have been repeatedly infected by bornaviruses at different points in time during evolution. This study provides novel insights into the evolutionary history of bornaviruses and demonstrates the robustness of combining database searches, PCR, and sequencing approaches to estimate insertion dates of bornaviruses.
内源性类博尔纳病毒元件（EBLs）是源自博尔纳病毒（博尔纳病毒科）并整合到动物基因组中的序列。它们是通过博尔纳病毒转录本片段的种系插入到动物基因组中形成的。由于EBLs是博尔纳病毒的分子化石，它们是了解博尔纳病毒进化历史的宝贵信息来源。先前的研究揭示了蝙蝠基因组中存在许多EBLs，尤其是在鼠耳蝠中，并表明蝙蝠与博尔纳病毒之间存在长期关联。然而，由于公共数据库中可用蝙蝠基因组序列的局限性，EBLs的插入日期在很大程度上尚不清楚。在本研究中，通过数据库搜索、PCR和测序方法的结合，我们系统地确定了鼠耳蝠属和棕蝠属以及蝙蝠科蝙蝠中13个EBLs谱系的基因直系同源性。利用上述数据，我们估计了它们的插入日期：鼠耳蝠中的EBLs大约在1420万至5300万年前插入。这些结果表明，在进化过程中，鼠耳蝠在不同时间点多次感染博尔纳病毒。本研究为博尔纳病毒的进化历史提供了新的见解，并证明了结合数据库搜索、PCR和测序方法来估计博尔纳病毒插入日期的稳健性。
