南极冰鱼血红细胞丢失的表观遗传调控与低氧适应机制研究

The molecular mechanism of hypoxia adaptation is a fundamental biological question, which has attracted wide attention from the world. Understanding of the hypoxia adaptation mechanism is significant in improving of agriculture and aquaculture. Antarctic icefish completely lost the hemoglobin during the evolutionary process in chronically freezing ambient. The oxygen binding ability of icefish is only 10% of the normal teleost. The hemoglobinless icefish with only very few unfunctional “red blood cells” provide us a perfect natural system to investigate hypoxia adaptation. By using comparative genomics and transcriptomics analysis, our previous studies revealed that the altered hematopoietic genetic programs in the Antarctic icefish head kidney (the main hematopoiesis tissue) in comparison with the red-blooded notothenioid fishes were identified. Genes involved in erythropoiesis were severely down-regulated, whereas those in lymphocytes and platelet development were significantly up-regulated in the icefish. It was reported that epigenetical regulation play important role in post-transcription. Our study will use up-to-date epigenetic techniques, such as genome-wide DNA methylation sequencing (MeDIP-seq) and Chromatin Immunoprecipitation sequencing (ChIP-seq) to detect variations of DNA-methylation and histone modifications in the Antarctic icefish genome. The functions of these epigenetical variations on erythropoiesis and hypoixa regulation will be studied by bioinformatic analysis and tested in cell lines and zebrafish. Our study will enlarge the datatbase of fish epigenetics, and provide important resourses for genetic and epigenetic intervention for hypoixa adaptation in fishes.

生物对低氧适应的分子机制是受到普遍关注的生物学基础问题，对促进农业和水产养殖的发展具有重要意义。南极冰鱼缺乏血红蛋白，仅具有极少量无功能“类红血球”，其运氧能力仅为具有血红蛋白硬骨鱼类的10%。南极冰鱼为研究鱼类低氧适应机制提供了极佳的实验体系。前期工作利用比较基因组学、跨物种转录组比较，首次揭示冰鱼血液发生主要组织头肾的基因表达程序出现大规模重建，红细胞发生过程被大大抑制，其他血细胞和血小板的发生被显著上调。在此基础上，本研究将采用全基因组DNA甲基化测序和染色体免疫沉淀结合测序技术，鉴定冰鱼基因组DNA甲基化和组蛋白修饰的特征性改变，分析这些改变对于冰鱼血红细胞丢失和低氧适应的影响，挖掘受表观遗传调控的血红细胞发生、低氧适应相关基因与信号通路，并在细胞系和斑马鱼体内进行功能验证，从而揭示鱼类如何在表观遗传学层次进行低氧适应。本研究将为鱼类低氧适应的遗传与表观遗传干预提供重要的理论依据。

南极冰鱼缺乏血红蛋白，仅具有极少量无功能“类红血球”，其运氧能力仅为具有血红蛋白硬骨鱼类的10%。南极冰鱼为研究鱼类低氧适应机制提供了极佳的实验体系。本课题主要以南极海域特有的血红蛋白缺失、血红细胞缺乏的独角雪冰鱼(Chionodraco hamatus)和两种含有血红蛋白但处于相同生境下近缘物种革首南极鱼(Notothenia coriiceps)和伯氏肩孔南极鱼(Trematomus bernacchi)为研究对象，对独角雪冰鱼和伯氏肩孔南极鱼血液发生主要组织头肾组织进行了甲基化DNA免疫共沉淀测序 (MeDIP-Seq)，分析获得两种南极鱼基因组DNA甲基化特征的差异；通过全基因组甲基化测序(Whole Genome Bisulfite Sequencing, WGBS)的方法，比较了独角雪冰鱼和革首南极鱼两种南极鱼心脏和皮肤组织的单碱基分辨率的甲基化组差异；比较了独角雪冰鱼、革首南极鱼和伯氏肩孔南极鱼三种南极鱼血液发生主要组织头肾全蛋白质组的差异，并分析了三种南极鱼头肾的蛋白质乙酰化、组蛋白乙酰化差异。针对在南极冰鱼心血管系统特异表达的多个microRNAs，验证了它们在血红细胞生成、心脏发育过程中的功能。通过大规模的转录组比较，揭示了低氧耐受的罗非鱼和低氧不耐受的斑马鱼在面临低氧胁迫时的分子应答机制的差异。筛选出一批与低氧适应相关的功能基因，为养殖鱼类的低氧育种指出了新的方向。