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Capacitation, the Acrosome Reaction, and Motility in Mammalian Sperm
Published in Claude Gagnon, Controls of Sperm Motility, 2020
Susan S. Suarez, John W. Pollard
The acrosome is a membrane bounded organelle containing a variety of hydrolytic enzymes (see Reference 1 for a list). At least some of these enzymes, most notably acrosin,47 assist in the penetration of the zona pellucida by weakening its structure. The enzymes are evidently released via a reaction that resembles exocytosis. It was first reported in 1958 by Austin and Bishop,48 and the process was described in 1967 by Barros et al.49 The major events of the acrosome reaction can best be seen in electron micrographs as shown in Figure 2, taken from Suarez et al.50 The first sign of the acrosome reaction, which can occur in human spermatozoa within 1 min of the application of a stimulus, is the apparent decondensation of the acrosomal contents.51 This is followed by the fusion of the plasma membrane in limited areas with the underlying outer acrosomal membrane. Fenestration occurs at the points of fusion, followed by the formation of vesicles comprised of plasma and outer acrosomal membranes.51,52 Acrosomal enzymes may escape by passing between the vesicles or may be exposed after the vesicles are sloughed off. In the latter case, they may be adherent to the exposed surface of the inner acrosomal membrane.53
Regulation of fertility and infertility in humans
Published in C. Yan Cheng, Spermatogenesis, 2018
Nahid Punjani, Ryan Flannigan, Peter N. Schlegel
Successful sperm fertilization of an egg relies on numerous sperm parameters, described above, with the goal of penetrating the zona pellucida and fusion with an oocyte membrane, which is known as the acrosome reaction.124 Capacitation is the process that permits the acrosome reaction to occur and creates biochemical modifications to the acrosome of the sperm head, allowing penetration of the outer layer, and changes in the tail permitting greater mobility. These are ultimately facilitated by removal of sterols, glycoproteins, and increased permeability and influx of calcium.125 The acrosome is structurally located on the anterior half of the sperm head. Acrosome reaction involves the penetration of the corona radiata followed by the release of hyaluronidase and exposure of acrosin, which then digests the zona pellucida of the oocyte.126 These reactions are required for fertilization and defects in these steps have negative implications on fertility.
Preparation and evaluation of oocytes for intracytoplasmic sperm injection
Published in David K. Gardner, Ariel Weissman, Colin M. Howles, Zeev Shoham, Textbook of Assisted Reproductive Techniques, 2017
Having traversed the cumulus, the spermatozoon undergoes acrosome reaction and binds to the zona pellucida. Sperm-zona pellucida binding is mediated by specific sperm surface receptors. The primary ligand on the zona pellucida, ZP3, specifically binds to the plasma membrane of the acrosomal cap of the intact sperm. The secondary zona ligand, ZP2, binds to the inner acrosomal membrane of the spermatozoon (13–15). One of the inner acrosomal membrane sperm receptors was identified as acrosin (16–18). In order to penetrate the zona pellucida, the spermatozoon utilizes enzymatic as well as mechanical mechanisms. Specific enzymes that are released by the acrosome-reacted spermatozoon allow the invasion of the zona pellucida by local degradation of its components (19, 20). This enzymatic action is assisted by mechanical force generated by vigorous tail beatings that facilitate the penetration of the sharp sperm head (18–22).
Mapping the human sperm proteome – novel insights into reproductive research
Published in Expert Review of Proteomics, 2023
Mika Alexia Miyazaki, Raquel Lozano Guilharducci, Paula Intasqui, Ricardo Pimenta Bertolla
The consequences of the absence of Testis-expressed protein 101 (TEX101), a validated biomarker of male infertility, were also investigated, and it was noticed that in infertile men with a natural absence of TEX101. This protein is a glycosylphosphatidylinositol-anchored protein (GPI-AP) and in mice was found to be expressed in precursors of adult-type germ cells, spermatogenesis cells, and seminiferous tubules cells in mice [29,30]. Although knockout mice Tex101−/− background presented normal sperm morphology structure and motility, they were not fertile due to failure to induce pregnancy [31]. Other important proteins for fertilizing process were also downregulated, such as Acrosin, Acrosin-binding protein (ACRBP) and Izumo sperm-egg fusion protein 3 (IZUMO3), that participate in the acrosome structure and function, and Zona pellucida-binding protein 2 (ZPBP2), that acts in spermatozoa-zona pellucida binding [32]. IZUMO3 is a protein from protein family IZUMO, exclusively expressed on membrane of cells testes. In mice Izumo3-/- model, fertilization rates were lower compared to the wild-type and heterozygous mutants. Moreover, litter sizes were also significantly reduced. This outcome is likely due to a deficient acrosome [33]
Impact of nonionizing electromagnetic radiation on male infertility: an assessment of the mechanism and consequences
Published in International Journal of Radiation Biology, 2022
Rohit Gautam, Eepsita Priyadarshini, JayPrakash Nirala, Paulraj Rajamani
Mobile phone has become an integral part of daily life of human beings. As mobile phone is placed in pockets, exposure to the electromagnetic radiation emitted from these devices may affect reproductive system. A study focusing on analyzing the effect of 4 G mobile phone radiation (2.104 GHz frequency) and 3.0 W/kg SAR with respect to time period and distance, signified alteration in male reproductive parameters. Exposure of 18 hrs per day, at a distance of 3 cm for 28 days showed alterations in spermatogenesis with significant decrease in sperm cell, spermatogonia and leydig cells which effect the fertility (Oh et al. 2018). In an in vitro study, exposure of spermatozoa to 900 MHz radiation for one hour with a SAR value of 2.0 W/Kg affects sperm morphometry and binding to hemizona which decreases sperm fertilization capacity (Falzone et al. 2011). Similar results were also observed in another study performed on 124 semen samples, exposed to 850 MHz (SAR =1.46 W/kg) for one hour. Results showed a significant decrease in sperm motility, acrosin activity and sperm DNA fragmentation (Zalata et al. 2015).
Differentiation of spermatogonial stem cells by soft agar three-dimensional culture system
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Elham Mohammadzadeh, Tooba Mirzapour, Mohammad Reza Nowroozi, Hamid Nazarian, Abbas Piryaei, Fatemeh Alipour, Sayed Mostafa Modarres Mousavi, Marefat Ghaffari Novin
Acrosin is a serine protease that is used as a marker for spermatogenesis and it is in the acrosome of sperm as an enzyme passive zymogen. Acrosin gene is expressed in both pachytene spermatocyte and round spermatid [38]. In this study, the highest expression of Acrosin gene was observed on day 14 after culture in SACS group, which was significantly higher than that of day 7. Although the expression of Acrosin was higher on day 14 after culture in both gelatin and control groups than day 7, there was no significant difference between two days in two groups. The study of Ventela et al. (2000) showed that low expression of Acrosin in mice was seen in pachytene spermatocytes and after meiosis completion, Acrosin is aggregated in the cytoplasm and lead to strong expression in round spermatid [39]. So, higher expression of Acrosin in SACS group is probably related to a higher number of round spermatid on day 14.