南湖新闻网讯（通讯员 张茹）2022年10月19日，我校生命科学技术学院、生物医学与健康学院精准营养与代谢团队陈振夏课题组联合中科院水生生物研究所孙永华团队在Advanced Science在线发表题为A Germline-specific Regulator of Mitochondrial Fusion is Required for Maintenance and Differentiation of Germline Stem and Progenitor Cells的论文。该论文发现了一个在生殖细胞中特异表达的线粒体融合调控因子-pld6。pld6缺失导致生殖细胞中线粒体动态失衡，线粒体形态及功能发生严重缺陷，进一步导致生殖干祖细胞命运的维持和分化受阻，最终形成缺乏生殖细胞的“空巢性腺”。该研究为生殖细胞发育的调控机制提供了新的见解，明确了线粒体融合对于生殖细胞命运决定的重要作用。
在全球范围，人类生育力呈明显下降趋势，而现代的辅助生殖技术面临着理论和技术瓶颈，关键问题是目前人类对调节生殖细胞、胚胎正常发育的分子机制认识有限。斑马鱼拥有与人相似的组织器官和系统，基因和信号通路与人类高度保守，生理、发育和代谢与哺乳动物高度相似。本研究以斑马鱼为模型，通过生物信息学及实验生物学手段系统研究了生殖细胞发育的调控途径。
首先，研究者对性腺分化阶段的精卵巢进行转录组分析，结果表明线粒体组装以及氧化磷酸化相关基因在卵巢组织中高量表达。通过scRNA-seq分析发现，调控线粒体融合的关键因子pld6不仅在卵巢组织的转录水平高于精巢，并且在生殖干祖细胞中特异表达。
随后，研究者建立pld6缺失的突变体模型，结果显示，纯合突变体全部发育为不可育的雄性。通过组织学染色以及对生殖细胞、生殖体细胞的标记基因的检测，研究者发现纯合突变体的性腺中生殖细胞完全丢失。为了明确突变体生殖细胞丢失的时间节点，研究者对突变体性腺发育进行连续追踪。结果表明，pld6缺失导致生殖干祖细胞既无法通过有丝分裂进行增殖，也无法通过减数分裂进行分化，继而在性腺发育的早期即走向细胞凋亡途径。
图1
研究人员进一步分析了突变体生殖干祖细胞中线粒体融合分裂的动态变化以及功能状态，结果表明，突变体中线粒体动态失衡，线粒体拷贝数以及ATP合成均显著减少。同时，生殖细胞中特有的线粒体云nuage在突变体中缺失，进而导致piRNA的合成受阻（图1）。
中科院水生所孙永华研究员和华中农业大学陈振夏教授为该文通讯作者。华中农业大学博士后张茹和博士生涂懿璇为该文并列第一作者。目前，陈振夏课题组已在两性间的表型差异以及导致性别差异的性别偏爱性基因的功能方面开展了多项研究。
【英文摘要】
Maintenance and differentiation of germline stem and progenitor cells (GSPCs) is important for sexual reproduction in multicellular organisms. Zebrafish initially form a bipotential juvenile gonad containing GSPCs that differentiate approximately at 28 days postfertilization (dpf). Here, we cross-analyzed the RNA sequencing results of zebrafish juvenile testes and ovaries, and found that the mitochondrial organization process was significantly enriched by Gene Ontology analysis. We further identified mitoPLD (zebrafish pld6) as a novel germline-specific gene related to mitochondrial fusion and generated pld6-knockout mutants. The mutants developed exclusively into infertile males with no sperm in testes. Zygotic disruption of pld6 did not affect the initial number of GSPCs, whereas the mutants had a small size in gonads at 25 dpf and the GSPCs failed to differentiate into early oocytes thereafter. The germ cells disappeared in the mutants after 35 dpf, eventually leading to masculinization and infertility of the mutants. Mitochondrial fusion in the pld6-depleted GSPCs was severely impaired, and the mutants exhibited defects in piRNA biogenesis and transposon suppression. Overall, this work uncovers zebrafish Pld6 as a novel germline-specific regulator of mitochondrial fusion, and highlights its essential role in the maintenance and differentiation of GSPCs as well as in gonadal development and gametogenesis.
论文链接：http://doi.org/10.1002/advs.202203631
审核人：陈振夏
