锌离子调节秀丽线虫精子细胞成熟和受精的机理研究

Zinc, acting as an essential trace element for all organisms, plays the important roles in various biological activities. Zinc is essential for the sperm maturation and motility in many species, and in vertebrates, zinc accumulates in the testis at high levels which are comparable to those in liver and kidney. Zinc deficiency results in the male infertility in human. Our previous data showed the Zinc in vitro triggered the spermatids maturating into spermatozoa in the nematode C.elegans. The Zinc staining assay indicated the intracellular zinc is dynamic and its distribution had changed during the spermatids maturing into spermatozoa. In addition, labile zinc is also detected in the reproductive tract of both hermaphrodites and males, indicating the vital roles of zinc plays on the C.elegans sperm maturation and motility. However, the regulating mechanism of zinc on sperm maturation and motility still keeps unclear. In this project, we will study the regulating roles that the zinc plays on the sperm maturation, motility and fertilization in the nematode C.elegans. On the one hand, we will analyze the pathway of zinc triggering sperm maturation, and study the relationship between the zinc stimulating signal and spe-8 pathway, which is involved in C.elegans sperm maturation. On the other hand, we will explore the effects of the zinc on the sperm development and subsequently fertilization by studying the zinc storage and secretion, and reveal the mechanism of sperm competition during the fertilization process. The expected results might not only promote people to learn the molecular mechanism of zinc regulating biological activity, keep the reproductive health, but also be useful to develop new strategies to enhance the cure of male sterile and nontoxic contraceptive.

锌离子作为生物体必须的微量营养元素，在多种生命活动中发挥重要的调控作用，对于多个物种的精子细胞成熟和运动都是必不可少的，人体锌匮乏可引起男性不育，我们在模式生物秀丽线虫中的研究显示锌离子体外可诱导精子细胞成熟为可运动的精子，体内锌染色发现锌离子在精子细胞成熟前后其胞内分布发生了明显改变，并在储精囊等生殖器官富集，说明锌离子对于秀丽线虫精子的发育和成熟同样至关重要。但是锌离子在线虫精子成熟和运动过程中的调控机理目前仍不清楚。本项目继续研究锌离子在秀丽线虫精子细胞成熟，运动及其受精过程中的调节作用，探讨锌离子诱导线虫精子细胞成熟的信号网络，分析其在线虫体内的储存，分泌及对精子细胞发育，成熟及随后受精的影响，揭示精子竞争和受精成功的分子机理。预期结果不仅进一步加深理解锌离子发挥作用的调控机理，而且对于揭示人类生殖生育的分子机理，维持生殖健康，治疗不育，开发无毒避孕药等具有重要的理论指导意义。

精子激活成熟即是精子细胞形态建成，涉及到细胞形态的、生理的、以及生化的一系列变化，最后成熟为功能性精子。其中任一个环节的调节异常都将导致精子受精失败。锌离子是生物体必须的微量元素，在多种生命活动中发挥重要的调控作用，对于精子的成熟运动也是必不可少的；锌离子既可以与蛋白结合调节蛋白活性，又可以作为信号分子或者第二信使参与生命活动的调节；胞质中锌离子的缺乏和过量都是有害的，但如何维持胞质中的锌平衡却知之甚少。本项目以线虫为材料，研究完成减数分裂的精子细胞响应激活因子的诱导信号，完成形态建成获得受精能力的调控机制，分析锌离子在精子激活中的调控作用，并探讨精子细胞中锌平衡调控的分子基础。主要成果包括： 1）确定了胞内钙离子以及MAPK信号通路对于锌离子诱导的精子激活是必须的（BBA- Molecular Cell Research，2014）。2）在C. elegans中鉴定到新的锌转运蛋白ZIPT-7.1，并研究了ZIPT-7.1在精子发育成熟中的调控机理（PLoS Biology，under reviewing）。3）发现了C. elegans线虫精子特异的膜器官MO是一个内质网-溶酶体复合体，作为胞内钙库调节精子激活运动，精子激活时钙库中钙离子的释放受到溶酶体钙通道类TPC和内质网钙通道类RyR的精确调节（In submitting）。4）探讨了精子激活时胞内生理环境改变的分子机理，获得了钠钾ATPase CATP-4蛋白调控线虫精子功能的分子机理（In submitting），发现了钠氢转运蛋白NHX-7和NHX-9协调调节精液pH以影响精子功能（In submitting）。5）在C.elegans线虫中鉴定到新的组蛋白二甲基转移酶SET-18并研究了SET-18调控线虫寿命和精子功能的信号网络（Cell Reports，Accepted）。6）受邀撰写了piRNA与精子发生相关的综述论文，发表于遗传杂志。这些结果的获得为人们维持生殖健康，治疗男性不育，理解锌离子调控的相关生命过程提供了重要的理论依据。目前受该项目资助已发表文章3篇，培养4名博士生毕业，组织项目成员参加国内外学术会议12人次。