[Show abstract][Hide abstract] ABSTRACT: Three major cytoskeletal proteins, actin, tubulin and spectrin, are present in the head of mammalian spermatozoa. Although cytoskeletal proteins are implicated in the regulation of capacitation and the acrosome reaction (AR), their exact role remains poorly understood. The aim of this study was to compare the distribution of the sperm head cytoskeleton before and after the AR in spermatozoa representing a range of acrosome size and shape. Spermatozoa from the human and three rodents (rat, hamster and grey squirrel) were fixed before and after the AR in appropriate medium in vitro. Indirect immunofluorescent localization of cytoskeletal proteins was undertaken with antibodies recognizing actin, spectrin and alpha-tubulin. Preparations were counterstained with propidium iodide and examined by epifluorescent and confocal microscopy. Our results clearly demonstrated changes in localization of cytoskeleton during the AR, mainly in the apical acrosome with further changes to the equatorial segment and post-acrosomal regions. The pattern of cytoskeletal proteins in the sperm head of all the species was similar in respect to various sub-compartments. These observations indicated that the sperm head cortical cytoskeleton exhibits significant changes during the AR and, therefore, support the image of cytoskeletal proteins as highly dynamic structures participating actively in processes prior to fertilization.
Full-text · Article · Aug 2005 · Reproduction (Cambridge, England)
[Show abstract][Hide abstract] ABSTRACT: Ubiquitination is a universal protein degradation pathway in which the molecules of 8.5-kDa proteolytic peptide ubiquitin are covalently attached to the epsilon-amino group of the substrate's lysine residues. Little is known about the importance of this highly conserved mechanism for protein recycling in mammalian gametogenesis and fertilization. The data obtained by the students and faculty of the international training course Window to the Zygote 2000 demonstrate the accumulation of ubiquitin-cross-reactive structures in the trophoblast, but not in the inner cell mass of the expanding bovine and mouse blastocysts. This observation suggests that a major burst of ubiquitin-dependent proteolysis occurs in the trophoblast of mammalian peri-implantation embryos. This event may be important for the success of blastocyst hatching, differentiation of embryonic stem cells into soma and germ line, and/or implantation in both naturally conceived and reconstructed mammalian embryos.
No preview · Article · Feb 2001 · Cloning and Stem Cells
[Show abstract][Hide abstract] ABSTRACT: Certain morphological changes such as rearrangement of cytoskeletal proteins of the mammalian spermatozoa are detectable during the AR. The type of changes differs according to the studied sperm species and follows the course of AR. Relocation of cytoskeletal structures was previously observed especially in the case of actin-, alpha-, gamma-tubulin- and spectrin-containing structures. To prove these findings we used specific inhibitors of cytoskeletal proteins (eg. colcemide, cytochalasine B, nocodazole and vinblastine). It has been shown that the AR is influenced by cytoskeletal inhibitors, but the obtained results also document that cytoskeletal proteins actin, tubulin and spectrin play a significant role in the course of AR in vitro. Our results of confocal and electron microscopy also demonstrate visible changes of actin-, tubulin- and spectrin-containing structures after the AR. Our data indicate that specific cytoskeletal inhibitors influence the AR and they prove the role of cytoskeletal proteins in this process.
[Show abstract][Hide abstract] ABSTRACT: Several cytoskeletal proteins (alpha-tubulin, beta-tubulin, actin, spectrin, tropomyosin, vimentin and cytokeratin) were studied in human and boar spermatozoa. Their localization was observed by means of specific antibodies using indirect immunofluorescence technique. Immunocytochemical results were confirmed by the Western blot technique. Cytoskeletal proteins were examined in ejaculated spermatozoa before and after acrosome reaction induced by the ionophore A23187. The immunofluorescence assay revealed that localization of the studied cytoskeletal proteins in human and boar spermatozoa differ remarkably. In human spermatozoa, the localization of actin and spectrin changed after acrosome reaction; on the other hand, in boar spermatozoa, the changes of localization concerned alpha-tubulin, beta-tubulin, actin and spectrin. The type of changes differs in the studied species and follows probably the course of acrosome reaction. The results suggest that cytoskeleton participates in the process of acrosome reaction of mammalian spermatozoa.