Dynamics of the Mammalian Sperm Head: Modifications and Maturation Events From Spermatogenesis to Egg Activation (Advances in Anatomy, Embryology and Cell Biology Book 204)

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 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 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 occurring in sperm-head components and compare the outcomes of these events with the outcomes of their failure. List of Contents......Page 6 1. Introduction......Page 14 2.1 Structures, Domains, and Related Functions......Page 19 2.2.1 Periacrosomal and Subacrosomal Layers......Page 20 2.2.2 Postacrosomal Layer......Page 21 2.3 Membrane System......Page 22 3. Sperm-Head Formation and Factors Affecting It......Page 25 3.1.1 Stem-Cell Factor, Steel Factor, and the c-kit Receptor......Page 26 3.1.2 Intercellular Bridges......Page 28 3.1.3 Ectoplasmic Specialization......Page 30 3.2 IgSF Proteins......Page 31 3.2.2 IgSF Proteins Expressed on Germ Cells......Page 32 4.1 In the Epididymis......Page 34 4.2 In the Female Reproductive Tract......Page 36 5.1 Acrosome Biogenesis During Spermatogenesis......Page 37 5.1.2 Cap Phase (Steps 4–7 in Mice, Sb1–2 in Humans)......Page 38 5.1.3 Elongation Phase or Acrosome Phase (Steps 8–12 in Mice, Sc in Humans)......Page 39 5.2 Pathways for the Transport of Acrosomal Molecules......Page 40 5.4.2 Acrosomal Matrix......Page 42 5.4.3 Subcompartments......Page 43 5.5 Acrosomal Enzymes and Other Molecules......Page 44 5.6 Failure of Acrosome Biogenesis......Page 45 6.1 Biogenesis During Spermatogenesis......Page 48 6.2 Functions of Perinuclear Theca-Associating Molecules......Page 49 7.1 Formation and Maturation of the Nucleus......Page 50 7.2 Abnormal Nucleus Formation in Gene-KO Mice......Page 53 7.3.1 DNA Damage in Germ Cells and Mature Spermatozoa......Page 54 7.3.2 Evaluation of DNA Fragmentation......Page 55 8.1 Modifications in Sperm Plasma-Membrane Proteins......Page 57 8.2 Zona Pellucida Binding and the Acrosome Reaction......Page 59 8.4 The Acrosome Reaction......Page 60 8.5 Rapid and Slow Release of Acrosomal Molecules......Page 64 8.6 Secondary Binding to the Zona Pellucida and the Candidate Molecules Involved......Page 66 8.7 Priming for Gamete Membrane Fusion and the Candidate Molecules Involved......Page 70 8.8 Gamete Membrane Fusion......Page 72 9.1 Sperm (Cytoplasmic) Factor and Candidate Molecules Involved in Egg Activation......Page 75 9.2 Sperm Receptor......Page 78 9.3 After Egg Activation......Page 79 10. Status of Sperm-Head Components During Normal Fertilization, IVF, ICSI, and Round Spermatid Injection......Page 80 11. Conclusion......Page 82 References......Page 84 C......Page 98 I......Page 99 P......Page 100 S......Page 101 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 immunocytochemistry 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 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. This book discusses 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