Toshimori Kiyotaka
Department of Anatomy and Developmental Biology, Chiba University Graduate School of Medicine, Japan.
Adv Anat Embryol Cell Biol. 2009;204:5-94.
Mammalian spermatozoa have complex structures. The structure-function relationship of sperm has been studied from various viewpoints. Accumulated evidence has shown that the sperm components undergo sequential changes from the beginning of spermatogenesis to the time of fertilization/embryogenesis. Structural analyses have been performed using various new techniques of light and electron microscopy as well as immunohistochemistry and immunocytochemistry in combination with specific probes such as antibodies against sperm components. Recently developed gene-manipulation techniques have accelerated investigations on the events that govern the relationship between the structure and the molecular components of sperm. In addition, animal models with gene manipulations have been shown to exhibit various morphological and functional abnormalities that lead to infertility. In humans, male infertility is caused by a number of factors, such as the external environment, nutrient changes, genotoxins, and mutagens. These factors affect not only the development of germ cells during spermatogenesis but also the functions of mature sperm, ultimately impairing fertilization or embryogenesis. Typical phenotypes of impaired fertilization or embryogenesis are visible in conditions such as azoospermia, oligozoospermia, and teratozoospermia, which have been induced in model animals with gene deficiencies. Thus, comparative analyses of the phenotypes expressed by model animals carrying gene mutations and infertile human patients should be performed in relation to the normal (natural) fertilization process to clarify the etiology of infertility due to male factors. In this book, I discuss the events that occur in the normal sperm head and govern the structure-function relationship from the time of spermatogenesis to that of fertilization or egg activation. In this regard, I describe dynamic modifications and maturation events that occur in sperm-head components and compare the outcomes of these events with the outcomes of their failure.
哺乳动物的精子具有复杂的结构。人们已从各种角度研究了精子的结构与功能关系。越来越多的证据表明，从精子发生开始到受精/胚胎发生之时，精子成分会发生一系列变化。人们运用了光学显微镜、电子显微镜以及免疫组织化学和免疫细胞化学等各种新技术，并结合针对精子成分的特异性探针（如抗体）进行了结构分析。最近开发的基因操作技术加速了对控制精子结构与分子成分之间关系的相关事件的研究。此外，经基因操作的动物模型已显示出各种形态和功能异常，从而导致不育。在人类中，男性不育由多种因素引起，如外部环境、营养变化、基因毒素和诱变剂。这些因素不仅影响精子发生过程中生殖细胞的发育，还影响成熟精子的功能，最终损害受精或胚胎发生。在无精子症、少精子症和畸形精子症等情况下，可以看到受精或胚胎发生受损的典型表型，这些表型已在基因缺陷的模型动物中诱发。因此，应该针对正常（自然）受精过程，对携带基因突变的模型动物和不育人类患者所表现出的表型进行比较分析，以阐明男性因素导致不育的病因。在本书中，我将探讨正常精子头部发生的事件，以及从精子发生到受精或卵子激活这段时间内控制结构与功能关系的相关事件。在这方面，我将描述精子头部成分中发生的动态修饰和成熟事件，并将这些事件的结果与其失败的结果进行比较。
