Genome Architecture in Human Sperm Cells

哺乳动物精子是一种独特的细胞类型，其中的DNA排列成紧凑的遗传惰性状态。近年来，在人类精子中发现了一种明确的基因组空间结构——基因组结构（genome architecture， GA）：每条染色体占据不同的区域，所有着丝粒聚集成一个致密的染色质中心，埋藏在细胞核内，而所有端粒都暴露在外围并相互作用形成二聚体。一般的假设是，在成功受精过程中，非随机精子遗传决定并促进了有序的染色体退出和运动。特别是，在一些男性不育的病例中，GA缺陷可能对早期发育产生不利影响。长期目标是建立染色体在正常的、可生育的人类精子中是如何排列和排列的“标准”，并开发在辅助生殖过程中适当选择供体细胞的原位测试。第一个目标是揭示在已证实生育能力的供体精子中GA的未知特征。在初步实验中，提出了一种直接观察精子染色体组织的新方法。在本研究中，将建立单个染色体的核路径和高阶结构。接下来，将分析端粒二聚体的性质。初步数据表明，它们是由一条染色体两端的相互作用形成的。如果是这样，人类精核中的染色体就是环状的。此外，单个染色体的核定位将被确定。在初步研究中获得了精子细胞核中染色体非随机空间排列的强烈迹象。第二个目标是对接受IVF/ICSI治疗的精子形态异常男性精子中的GA进行系统研究。这些研究将确定染色体是如何在可育的人类精子中包装和排列的，并将使人们更好地理解男性基因组空间组织在受精中所起的作用。所获得的信息应有助于改进诊断分析和更好地预测辅助生殖的结果。最后，它将增加我们对人类细胞中染色体结构组织的基本知识。

The mammalian spermatozoa is a unique cell type in which the DNA is arranged into a compact and genetically inert state. Recently, the existence of a well-defined spatial organization of genome - genome architecture (GA) have been shown in spermatozoa of humans: each chromosome occupies distinct territory, all centromeres are clustered into a compact chromocenter buried within the nucleus, while all telomeres are exposed at the periphery and interact to form dimers. The general hypothesis is that non-random sperm GA determines and promotes an ordered chromosome withdrawal and movements during successful fertilization. In particular, defective GA in some cases of (male infertility may have an adverse impact on early development. The long-term goal is to establish the "standard" of how chromosomes are packed and arranged in normal, fertile human sperm, and to develop in situ tests for proper selection of donor cells during assisted reproduction. The first objective is to unravel as yet unknown characteristics of GA in sperm of donors with proven fertility. In preliminary experiments a new approach to directly observe chromosome organization in sperm has been developed. In the proposed study, nuclear path and higher- order structures of individual chromosomes will be established. Next, the nature of telomere dimers will be analyzed. Preliminary data indicate that these are formed by interactions between two ends of one chromosome. If so, chromosomes in human sperm nuclei are looped. Further, nuclear positioning of individual chromosomes will be determined. Strong indications towards non-random spatial arrangement of chromosomes in sperm nuclei have been obtained in preliminary studies. The second objective is a systematic study of GA in spermatozoa of men with abnormal sperm morphology undergoing treatment with IVF/ICSI. These studies will establish how chromosomes are packed and arranged in fertile human sperm and will lead to a better understanding of the role played by the male genome spatial organization at fertilization. The information obtained should contribute to an improvement of diagnostic assays and better prediction of the outcome of assisted reproduction. Finally it will add to our basic knowledge about structural organization of chromosomes in human cells.