title: Hypoxia alters testicular functions of marine medaka through microRNAs regulation.
abstract: Hypoxia is a global environmental concern and poses a significant threat to aquatic ecosystems, including the sustainability of natural fish populations. The deleterious effects of hypoxia on fish reproductive fitness, as mediated by disruption of sex hormones and gene expression along the Brain-Pituitary-Gonad axis, have been well documented. Recently, we further demonstrated that the observed disruption of steroidogenesis in the ovary of marine medaka Oryzias melastigma is mediated through microRNAs (miRNAs). More importantly, we reported the transgenerational epigenetic effect of hypoxia on the male reproductive impairment of marine medaka. This study attempts to elucidate the function of miRNAs and its potential role in the transgenerational effect of hypoxia in the male medaka testis, using small RNA sequencing. A total of 558 miRNAs were found in the testis, of which 9 were significant upregulated and 5 were downregulated by hypoxia. Bioinformatics analysis further revealed that among the 2885 genes targeted by the hypoxia-responsive miRNAs, many are closely related to stress response, cell cycle, epigenetic modification, sugar metabolism and cell motion. Furthermore, the integrated analysis of transcriptome data and the result of target gene prediction demonstrated 108 genes and 65 genes were concordantly upregulated and downregulated, respectively. In which, euchromatic histone-lysine N-methyltransferase 2, the epigenetic regulator of transgenerational reproductive impairment caused by hypoxia, is found to be targeted by miR-125-5p. The present findings not only reveal that miRNAs are crucial downstream mediators of hypoxic stress in fish male gonad, but also shed light on the underlying epigenetic mechanism for the reproductive impairments of hypoxia on male fish, including the observed transgenerational effects.
authors: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China. Electronic address: annatse@hku.hk.
authors: Anna Chung-Kwan
authors: AC
authors: Tse
authors: School of Life Sciences, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong SAR, China. Electronic address: marcowanger@gmail.com.
authors: Jing-Woei
authors: JW
authors: Li
authors: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China. Electronic address: bioywang@hku.hk.
authors: Simon Yuan
authors: SY
authors: Wang
authors: School of Life Sciences, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong SAR, China. Electronic address: tf.chan@cuhk.edu.hk.
authors: Ting-Fung
authors: TF
authors: Chan
authors: Department of Biology and Chemistry, City University of Hong Kong, Hong Kong SAR, China. Electronic address: kengplai@cityu.edu.hk.
authors: Keng Po
authors: KP
authors: Lai
authors: Department of Science and Environmental Studies, The Education University of Hong Kong, Hong Kong SAR, China; State Key Laboratory in Marine Pollution, Hong Kong. Electronic address: rudolfwu@ied.edu.hk.
authors: Rudolf Shiu-Sun
authors: RS
authors: Wu
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015536:Down-Regulation; D044127:Epigenesis, Genetic / Q000502:physiology; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D035683:MicroRNAs / Q000378:metabolism*; D009990:Oryzias / Q000235:genetics / Q000502:physiology*; D017423:Sequence Analysis, RNA; D013312:Stress, Physiological / Q000502:physiology*; D013737:Testis / Q000503:physiopathology*; D059467:Transcriptome; D015854:Up-Regulation; D014876:Water Pollution / Q000009:adverse effects*
chemical_list: D015415:Biomarkers; D035683:MicroRNAs
keywords: Hypoxia; MicroRNA; Small RNA sequencing; Testis