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日時：　２０２３年８月３０日（水）　１４：００～１５：３０
場所：　愛媛大学　工学部２号館　４階ゼミ室（４２１号室）

■講演１

演者：Artem BAIDALIUK, Ph.D.

         Research Engineer

         Department of Virology, Institut Pasteur, France

演題：Mosquito-specific viruses: diversity, evolution, and virus-host interactions.

要旨:

Mosquitoes are vectors for human and vertebrate animal pathogens, including viruses. Many of the prevalent mosquito virome constituents do not infect vertebrate animals and are transmitted vertically in mosquito populations. Exploration of the genetic diversity, geographic spread, host range, and evolutionary histories of mosquito-specific viruses is ongoing and necessary to obtain a comprehensive picture of the mosquito virome and its effects on mosquito populations and the pathogens they transmit. We initially focused on studying different aspects of one mosquito-specific virus, cell fusing agent virus (CFAV) that is found in Aedes aegypti mosquitoes. We demonstrated that CFAV could reduce dengue or Zika virus transmission potential in mosquitoes. We detected CFAV in mosquito laboratory colonies and field derived mosquitoes and, in the context of other available sequences, we noticed that the phylogeny of this vertically transmitted virus, found worldwide, did not follow its mosquito-host population structure in Southeast Asia. In another study, we showed that one CFAV-derived endogenous viral element (EVE) in Ae. aegypti genomes interacted with exogenous CFAV via the piRNA pathway and moderately reduced viral levels in mosquito ovaries. While investigating the CFAV – Ae. aegypti model continues, it is also important to boost the search for other mosquito-virus interaction models. We recently performed a virus discovery study in over 500 individual mosquitoes belonging to 21 morphologically assigned species of 6 genera collected across 5 locations in Cambodia. Novel genomic information allowed to broaden the host and geographic range of mosquito-specific virus groups, exposed examples of virus codivergence with mosquito host taxa or lack thereof, and strengthened the foundation for further studies of virus and mosquito ecology in Cambodia and worldwide.

■講演２

演者 : 中川 草 博士

         准教授

　　　東海大学医学部 分子生命科学

演題 : Dynamic evolution of endogenous retroviral envelope derived protein-coding genes in

　　　mammalian genomes.

要旨: 

Mammalian genomes contain a certain number of sequences derived from viruses, mainly retroviruses, which are called endogenous retroviruses (ERVs). As for the placenta, it is widely believed that ERV-derived genes, in particular for fusogenic genes derived from envelope genes of retroviruses (named “syncytins” in many cases), could be essential for placenta development. Therefore, the capture of syncytin genes from retroviruses are thought to be a pivotal step for the emergence of placenta in egg-laying ancestors. Indeed, the very small numbers of ERV-derived genes in the platypus (an egg-laying mammal) genomes arose the hypothesis that intensive invasion of therian genomes may facilitate the co-option of ERV-derived placental genes. Recently, accurate genome sequences of two egg-laying mammals, platypus and echidna, are decoded. We analyzed the genomes of the echidna and platypus and found various envelope genes derived from endogenous retroviruses (Kitao et al. MBE 2023). In particular, we revealed that an envelope gene of echidnas named env-Tac1 has fusogenic activity. These results strongly suggest that acquiring ERV-derived genes with fusion ability is an evolutionary requirement but not a sufficient condition for placenta acquisition. In this seminar, I would like to introduce the possibility of many unknown ERV-derived protein-coding genes based on our previously analyzed data (Nakagawa et al. Database 2016; Ueda et al. Mob DNA 2020).