The role of cleaved-protamine 2 in sperm chromatin dynamics.

对生殖的研究，无论是在医学上还是在进化的背景下，都非常重视与精子发育和功能有关的过程。这主要是由于这些过程在男性不育病例中所起的作用，以及对潜在基因的强大进化压力。父系DNA在精子细胞核中的包装及其在转运过程中的保护是精子正常功能的关键方面。成功的受精和胚胎存活依赖于在精子发生过程中父亲染色质的完全重组的正确执行，这是精子细胞特有的过程。组蛋白的凝聚不能提供通过男性和女性生殖道运输所需的尺寸缩小和屏蔽。因此，在染色质重组过程中，组蛋白被睾丸特有的精蛋白取代。哺乳动物的两种精蛋白(PRM1和PRM2)在男性不育和精子头部表型方面被广泛研究，并对精子功能起着至关重要的作用。然而，在精子染色质凝聚的谜题中，有一个重要的方面仍然是缺失的：PRM2的处理。虽然PRM2在其他方面与PRM1非常相似，但它是作为一种较长的前蛋白产生并加工的，将PRM2的C末端(DNA结合)部分和高度不同且功能未知的N末端结构域分开，该结构域被切割出来，而不是成熟精子中最终染色质包(裂解-PRM2)的一部分。已有研究表明，这一过程对于适当的染色质浓缩和防止DNA损伤是必不可少的，但我们对这一结构域及其功能的了解充其量是最基本的。我们建议在小鼠模型中研究裂解的PRM2的功能和作用，以及它与其他关键蛋白在调节和执行精子发生过程中染色质凝聚的相互作用。这项拟议的研究是一种跨学科的方法，结合了CRISPR/Cas基因编辑和比较进化方法。这将给我们提供独特的机会来深入了解父本基因组的组织和保护的分子基础，并促进我们对鱼精蛋白介导的DNA重组在男性不育中的参与的理解。

Studies on reproduction, be it in medical or evolutionary contexts, have always put a great emphasis on the processes involved in sperm development and function. This is mainly due to the role these processes play in cases of male infertility and the strong evolutionary pressures on underlying genes. The packaging of paternal DNA in the sperm cell nucleus and its protection during transit is a crucial aspect of correct sperm function. Successful fertilization and embryo survival depend on the correct execution of the complete reorganization of paternal chromatin during spermatogenesis, a process unique to sperm cells. Condensation by histones does not provide the size reduction and shielding necessary for transport through the male and female reproductive tracts. Histones are therefore replaced by testes specific protamines during chromatin reorganization. The two mammalian protamines (PRM1 and PRM2) have been studied extensively in the context of male infertility as well as sperm head phenotype and are crucial to sperm function. Yet there is an essential aspect that still is a missing piece in the puzzle of sperm chromatin condensation: the processing of PRM2. While otherwise very similar to PRM1, PRM2 is produced as a longer pre-protein and processed, separating the C-terminal (DNA binding) part of PRM2 and the highly different and functionally unexplored N-terminal domain, which is cleaved off and not part of the final chromatin package in mature sperm (cleaved-PRM2). It has been shown that this processing is imperative for proper chromatin condensation and the prevention of DNA damage, yet our knowledge about this domain and its function is rudimentary at best. We propose to study the function and role of cleaved-PRM2 and its interaction with other key proteins in the regulation and execution of chromatin condensation during spermiogenesis in a mouse model. The proposed study is designed as an interdisciplinary approach, combining CRISPR/Cas gene editing and comparative evolutionary methodologies. This will give us the unique opportunity to gain insight into the molecular basis of the organization and protection of the paternal genome and advance our understanding of the involvement of protamine-mediated DNA reorganization in male infertility.