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Faculty of Medicine School of Medicine Department of Infectious Diseases, Parasitology |
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Assistant Professor |
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Related SDGs |
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TANAKA Ryusei
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Papers 【 display / non-display 】
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Ishida M., Irie T., Tanaka R., Maruyama H., Yoshida A.
Infection Genetics and Evolution 135 105839 2025.11
Language：English Publishing type：Research paper (scientific journal) Publisher：Infection Genetics and Evolution
Strongyloides ratti is an intestinal nematode commonly found in rats. Unlike other Strongyloides species, the tissue-migrating third-stage larvae in S. ratti follow a unique route of invasion via the nasofrontal region before reaching the gut. Despite its importance in host invasion, the transcriptomic profile of this larval stage has not been characterized. In this study, we performed RNA sequencing (RNA-seq) to examine gene expression in head-derived tissue-migrating third-stage larvae (hL3) and infective third-stage larvae (iL3) of the S. ratti Tokyo strain. hL3 were collected from rat heads at 30 h post-infection. Differential expression analysis revealed 664 upregulated genes in hL3. Functional annotation showed enrichment of genes encoding astacin metalloproteases and sperm-coating protein/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) protein families—both associated with tissue invasion and immune modulation. Quantitative RT-PCR was used to validate selected differentially expressed genes. Seven hL3-specific astacin genes were identified, of which six belonged to the M12A group. One hL3-specific astacin gene showed domain similarity to strongylastacin, a known tissue-penetration protein. Two SCP/TAPS genes were unique to hL3 and were absent from parasitic females, suggesting distinct roles in larval migration. By contrast, G protein-coupled receptor genes, particularly those related to chemosensory functions, were not upregulated in hL3, indicating that these pathways may be less important during this stage. These results provide the first transcriptomic profile of hL3 in S. ratti, and identify potential molecular mechanisms driving larval migration and immune evasion during host infection.
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石田 まり, 入江 隆夫, 田中 龍聖, 丸山 治彦, 吉田 彩子
Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases 135 105839 2025.11
Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier BV
Strongyloides ratti is an intestinal nematode commonly found in rats. Unlike other Strongyloides species, the tissue-migrating third-stage larvae in S. ratti follow a unique route of invasion via the nasofrontal region before reaching the gut. Despite its importance in host invasion, the transcriptomic profile of this larval stage has not been characterized. In this study, we performed RNA sequencing (RNA-seq) to examine gene expression in head-derived tissue-migrating third-stage larvae (hL3) and infective third-stage larvae (iL3) of the S. ratti Tokyo strain. hL3 were collected from rat heads at 30 h post-infection. Differential expression analysis revealed 664 upregulated genes in hL3. Functional annotation showed enrichment of genes encoding astacin metalloproteases and sperm-coating protein/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) protein families-both associated with tissue invasion and immune modulation. Quantitative RT-PCR was used to validate selected differentially expressed genes. Seven hL3-specific astacin genes were identified, of which six belonged to the M12A group. One hL3-specific astacin gene showed domain similarity to strongylastacin, a known tissue-penetration protein. Two SCP/TAPS genes were unique to hL3 and were absent from parasitic females, suggesting distinct roles in larval migration. By contrast, G protein-coupled receptor genes, particularly those related to chemosensory functions, were not upregulated in hL3, indicating that these pathways may be less important during this stage. These results provide the first transcriptomic profile of hL3 in S. ratti, and identify potential molecular mechanisms driving larval migration and immune evasion during host infection.
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Protopoikilolaimus formosanus n. gen., n. sp. (Rhabditidae) isolated from Stylotermes halumicus from Taiwan Reviewed International coauthorship
Kanzaki N., Liang W.R., Tanaka R., Li H.F.
Nematology 27 ( 7 ) 729 - 745 2025.7
Language：English Publishing type：Research paper (scientific journal) Publisher：Nematology
An undescribed rhabditid species was isolated from the termite Stylotermes halumicus collected in Taiwan. The nematode was cultured using nematode growth medium seeded with Escherichia coli, and the cultured material was examined morphologically and molecularly. The nematode shares several typological characters with some Poikilolaimus spp.: namely, presence of stomatal flaps, posteriorly shifted amphid, hexagonal basal bulb, antidromously reflexed ovaries, pore-like female vulva, and lack of bursa or bursal flap. However, the species is distinguished from Poikilolaimus by its very short vs moderately-long pharyngeal sleeve, presence vs absence of deirid and post-deirid, filiform vs conical tail of both sexes, nine vs less than eight pairs of male genital papillae, and wide vs narrow lateral field. Phylogenetically, the species is located at a basal or a sister position to the clade represented by Poikilolaimus but is clearly separated from the genus by genetic distance. Therefore, the species is described herein as Protopoikilolaimus formosanus n. gen., n. sp.
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Kanzaki N., Tanaka R.
Nematology 27 ( 6 ) 697 - 715 2025.7
Language：English Publishing type：Research paper (scientific journal) Publisher：Nematology
Summary – An Aphelenchoides species was isolated from figs of Ficus septica collected from Okinawa, Japan. The nematode was morphologically and molecularly examined and found to be an undescribed species. Phylogenetic analyses based on near-full-length 18S (small subunit) and D2-D3 expansion segments of 28S (large subunit) ribosomal RNA revealed the species to be conspecific to an unidentified Aphelenchoides sp. isolated from pine cones in Japan and pine trees in China. The nematode is typologically characterised by a lateral field bearing three lines (two bands), a secretory-excretory pore positioned approximately at the level of the nerve ring, a relatively long pharyngeal gland lobe extending approximately 5-6 times the metacorpal length, an inconspicuous (not definitively confirmed) hemizonid, three pairs of male genital papillae (adcloacal papilliform P2, papilliform P3 at mid-tail, P5 gland papillae near the tail tip), and a somewhat stepwise appendage on the tail tip of both sexes, consisting of a thick basal part with numerous small nodule-like projections and a posterior part forming a simple spike. In terms of typical characteristics, this new species exhibits similarities to Aphelenchoides clarolineatus, A. emiliae and A. petersi. It shares the somewhat stepwise female tail appendage with these three species and the three-lined lateral field with A. petersi (lateral lines were not described for the former two species). However, the new species can be differentiated from these related species based on subtle differences in its typical characteristics and morphometric values. Based on prior isolation records, it is hypothesised that this new species inhabits the surface of woody plants and may occasionally enter the internal tissues through natural openings. Herein it is described as Aphelenchoides epiphyticus n. sp., with the species epithet derived from its presumed epiphytic habitat.
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Down-regulation of colon mucin production induced by Eimeria pragensis infection in mice Reviewed
小久保 美緒, 田中 龍聖, 長安 英治, 吉田 彩子, 丸山 治彦
Frontiers in Parasitology 4 1621486 2025.6
Language：English Publishing type：Research paper (scientific journal) Publisher：Frontiers Media S.A.
Introduction: Eimeria pragensis, an intestinal protozoa infecting mice, induces colitis and reduces goblet cell numbers in the large intestine. In the present study, we investigated the pathogenesis and the mechanisms underlying goblet cell down-regulation in the early phase of infection.
Methods: Male C57BL/6 mice were orally infected with 300 oocysts. Fecal oocyst shedding and body weight were monitored daily. Colon tissues were collected at 3, 8, and 13 days post-infection (dpi) to assess pathological changes. Parasite burden was assessed by histological analysis (H&E staining) and qPCR targeting 5S rRNA. Goblet cells were visualized using PAS-Alcian Blue staining and Muc2 immunohistochemistry. To elucidate mechanisms of goblet cell dysfunction, we performed RNA sequencing of large intestine tissue to examine host as well as parasite transcriptomes.
Results: Fecal oocyst excretion peaked at 8–9 dpi. Body weight decreased from 6 to 11 dpi, with recovery after 12 dpi. Maximal parasite accumulation in the proximal colon was observed at 8 dpi in histological examination as well as qPCR. Colon length was significantly shortened at 3 dpi. Goblet cell area significantly reduced at 8 dpi (p < 0.05). RNA sequencing of infected large intestines revealed that E. pragensis produced enzymes that were known to degrade mucin and tight junctions, and proteins that could activate the Notch–Hes1 signaling pathway. As for host responses, genes associated with Th1-type inflammation, epithelial barrier disruption, and immune regulation were up-regulated as early as 3 dpi.
Discussion: Our findings suggested that E. pragensis infection induces a mucosal barrier dysfunction in the early phase of the infection, which possibly causes the tissue invasion of bacteria in the large intestine. Th1-type inflammatory response, thus induced, reduces goblet cell numbers and mucin production. This model provides valuable insight into the mechanisms of mucosal barrier disruption during protozoan infection.
Books 【 display / non-display 】
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Nematodes Exploiting P. japonensis
Toyoshi Yoshiga, Ryusei Tanaka, Etsuko Okamura（ Role： Contributor）
Springer Nature 2022.10
Book type：Scholarly book
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生き物と音の辞典
高梨 琢磨 他（ Role： Joint author , 線虫の振動受容）
朝倉書店 2019.9
Total pages：441 Responsible for pages：336-337 Language：Japanese Book type：Scholarly book
音と音に類する刺激に対する様々な生物の反応の知見をまとめた著書。線虫の振動受容について担当。
Presentations 【 display / non-display 】
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線虫感染性 RNA ウイルスカタログの構築
千葉 悠斗, 田中 龍聖, 新屋 良治
日本線虫学会大会 2025.9.2
Event date： 2025.9.1 - 2025.9.3
Language：Japanese Presentation type：Oral presentation (general)
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A unique strain of Spirometra mansoni with the ability to proliferate in the host body
2025.3.18
Event date： 2025.3.18 - 2025.3.19
Language：Japanese Presentation type：Oral presentation (general)
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A sparganosis in which numerous plerocercoid were detected
Ryusei Tanaka, Mio Tanaka, Kanako Yamasaki, Eiji Nagayasu, Tomoaki Kubo, Haruhiko Maruyama
The 93rd Annual Meeting of the Japanese Society of Parasitology 2024.3.9
Event date： 2024.3.9 - 2024.3.10
Language：Japanese Presentation type：Oral presentation (general)
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ネズミ糞線虫Strongyloides rattiの自由生活世代と細菌の関係
田中龍聖・石田まり・太田有咲・地下勇矢・丸山治彦
第92回日本寄生虫学会大会 2022.5
Event date： 2022.5.30 - 2022.5.31
Presentation type：Poster presentation
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Relationship of Caenorhabditis inopinata with the wasp and bacteria in the fig ecosystem International conference
Ryusei Tanaka, Tanzila Afrin and Taisei Kikuchi
Seventh International Congress of Nematology 2022.5
Event date： 2022.5.1 - 2022.5.6
Presentation type：Poster presentation
Grant-in-Aid for Scientific Research 【 display / non-display 】
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線虫における種分化機構の複合的理解
Grant number：24K09595 2024.04 - 2027.03
独立行政法人日本学術振興会 科学研究費基金 基盤研究(C)
Authorship：Principal investigator
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線虫における種分化機構の複合的理解
Grant number：24K09595 2024.04 - 2027.03
基盤研究(C)
Authorship：Principal investigator
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イチジク果実内の生物群の共進化
Grant number：16K18608 2016.04 - 2019.03
科学研究費補助金 若手研究(B)
Authorship：Principal investigator