Kagoshima University · Division of Fisheries Sciences, School of Agriculture, Fisheries and Veterinary Medicine · 助教

Research keywordsphysiological resilience・Sirt1 signaling・MAPK signaling・hypoxia・reoxygenation・zebrafish embryos・visual physiology・neural differentiation

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• Liu T.Y., Yan J.J., Guh Y.J., Hayasaka O., Lin L.Y., Hwang P.P., Wu G.C., Chung M.T., Tseng Y.C. . Epigenetic insights into physiological resilience: Multigenerational readouts of CO2-induced2025 · 記述言語： 日本語 出版者・発行元： Iscience Anthropogenic CO<inf>2</inf> emissions are acidifying oceans, threatening marine organisms during early development. We investigated multigenerational effects of projected 2100 acidification (pH 7.6) on marine medaka (Oryzias melastigma) embryos across three generations using integrated phenotypic, physiological, transcriptomic, and epigenetic analyses. Prolonged acidification altered developmental trajectories, with F2 embryos showing size reductions. Metabolic responses were generation-specific: F0 embryos displayed decreased ammonium excretion, while F1 and F2 maintained stable profiles. Transcriptomic analysis revealed generational changes in neurotransmission, ion regulation, and epigenetic pathways. F2 embryos exhibited attenuated transcriptional perturbations and partial restoration of acid-base homeostasis, suggesting enhanced adaptability. Adaptive gene expression correlated with hypomethylation recovery of ion transport genes AE1a and NHE2 in F2 embryos. Increased hypomethylated AE1a promoter CpG sites in F1 and F2 generations aligned with elevated transcription, indicating epigenetically-driven enhancement. These results demonstrate epigenetic control's crucial role in multigenerational plasticity and adaptive responses to ocean acidification. DOI： 10.1016/j.isci.2025.113187 Scopus PubMed
• Cellular Energy Sensor Sirt1 Augments Mapk Signaling to Promote Hypoxia/Reoxygenation-Induced Catch-up Growth in Zebrafish Embryo2024 · 担当区分： 筆頭著者 記述言語： 英語
• Hayasaka O., Chang H.Y., Li L.C., Tseng Y.C., Shao Y.T. . Nocturnal Eyes in Slipper Lobsters (Decapoda Scyllaridae): Physiological and Ecological Implications of Habitat Depths for Visual Trai2022 · 記述言語： 日本語 出版者・発行元： Frontiers in Marine Science The light characteristics of an ecosystem drive evolutionary adaptations in visual traits, enhancing the diversity and abundance of species living there. The visual systems of crustaceans are highly diverse and often correspond to the optical properties of their preferred environments. Although habitat depth is known to greatly influence visual specialization in marine crustaceans, it remains unclear whether depth drives visual adaptions in nocturnal species. Slipper lobsters (Scyllaridae) are nocturnal benthic marine crustaceans distributed throughout a wide range of depths. In order to understand the visual adaptive capabilities of slipper lobsters inhabiting different depths, we characterized the eye structures of a shallow-water species (Parribacus japonicas), an intermediate-depth species (Scyllarides squammosus) and a deep-water species (Ibacus novemdentatus). Moreover, we measured by electroretinogram (ERG) the spectral sensitivities and temporal resolutions for each species using the following light stimuli: UV (λmax 386 nm), blue (λmax 462 nm), green (λmax 518 nm), yellow (λmax 590 nm), and red (λmax 632 nm). Our histological experiments show that all three species possess a typical superposition compound eye with square facets, and their ERG measurements revealed a single sensitivity peak for each species. Notably, peak spectral sensitivity corresponded to habitat depth, with the estimated peak for I. novemdentatus (493.0 ± 9.8 nm) being similar to that of S. squammosus (517.4 ± 2.1 nm), but lower than that of P. japonicus (537.5 ± 9.9 nm). Additionally, the absolute sensitivities at respective peak wavelengths for I. novemdentatus and P. japonicus were higher than that of S. squammosus. No differences were observed among the three species for maximum critical flicker fusion frequency (CFFmax) across light stimuli. However, P. japonicus had lower CFFmax values than the other two species. These data suggest that all three nocturnal slipper lobsters are likely monochromatic and well adapted to dim light environments. Significantly, the deep-water slipper lobster displayed higher spectral sensitivities at shorter wavelengths than the shallow water species, but temporal resolution was not compromised. DOI： 10.3389/fmars.2022.807347 Scopus
• Honda A., Hayasaka O., Mio K., Fujimura K., Kotani T., Komatsu M., Shiozaki K. . The involvement of Nile tilapia (Oreochromis niloticus) Neu4 sialidase in neural differentiation during early o2021 · 記述言語： 日本語 出版者・発行元： Biochimie Neurogenesis is an important process for the formation of the central nervous system during ontogenesis. Mammalian sialidases are involved in neurogenesis through desialylation of sialo-glycoconjugates. However, the significance of fish sialidases, unlike that of mammals, in neurogenesis has not been investigated. The present study focuses on Nile tilapia (Oreochromis niloticus) because of its unique profiles of sialidases related to enzymatic properties, subcellular localization, and tissue-specific gene expression. First, the fish were cultured under aphotic condition, which is known to cause the delayed development of the retina and brain in various fish. Next, we investigate the effect of aphotic condition on the levels of tilapia sialidases. Our results revealed that the tilapia showed a decrease in the number of ganglion cell in the retina. The expression level of neu4 mRNA is up-regulated in the eyes from tilapia reared in Dark accompanied by the increase of retinal differentiation markers. These results indicated that tilapia Neu4 is involved in retinal development in Nile tilapia. Furthermore, we tried to clarify the function of tilapia Neu4 in the neuronal cells using two neuroblast cell lines (SH-SY5Y and Neuro2a cell lines). Tilapia Neu4 decreased sialic acid level of both nuclear glycoproteins as well as glycolipids. Moreover, tilapia Neu4 accelerated neurite formation in both two neural cell lines and, increased the acetylcholinesterase activity, but it did not affect cell proliferation. Collectively, these results suggest that Neu4 accelerates neurite differentiation during ontogenesis in tilapia. DOI： 10.1016/j.biochi.2021.03.008 Scopus PubMed

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