Genome Architecture in Human Sperm Cells

哺乳动物精子是一种独特的细胞类型，其中DNA排列成致密和遗传惰性状态。最近，人类精子中存在着明确的基因组空间组织-基因组结构(GA)：每个染色体占据不同的区域，所有的着丝粒聚集在一个紧密的染色中心，埋在细胞核内，而所有的端粒暴露在外围，相互作用形成二聚体。一般的假设是，在成功的受精过程中，非随机的精子GA决定并促进了有序的染色体撤回和运动。尤其是在某些(男性不育)病例中，GA缺陷可能会对早期发育产生不利影响。长期目标是建立正常、有生育能力的人类精子中染色体如何包装和排列的“标准”，并开发原位测试，以便在辅助生殖过程中适当选择捐赠者细胞。第一个目标是揭开已证实有生育能力的捐赠者精子中GA尚不为人所知的特征。在初步实验中，开发了一种直接观察精子染色体组织的新方法。在这项拟议的研究中，将建立单个染色体的核路径和更高级别的结构。接下来，我们将分析端粒二聚体的性质。初步数据表明，这些染色体是由一条染色体两端的相互作用形成的。如果是这样的话，人类精子核中的染色体是环状的。此外，还将确定单个染色体的核定位。在初步研究中，已经获得了精子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的男性精子中的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，并将有助于更好地理解男性基因组空间组织在受精过程中所起的作用。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，它将增加我们关于人类细胞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.