Jana Antalíková

Acrosomal and viability status of bovine spermatozoa evaluated by two staining methods

Artificial insemination with frozen-thawed spermatozoa is commonly used in cattle breeding. A simple and fast procedure is needed for routine evaluation of the acrosomal status of frozen-thawed bovine sperm. Therefore, the purpose of this study was to test two staining procedures used to determine the viability and integrity of acrosome of frozen-thawed bovine spermatozoa. Double staining and Hoechst/FITC-Pisum sativum agglutinin (FITC-PSA) labelling were tested for evaluating the viability and acrosome reaction induced by calcium ionophore of bull spermatozoa. In our experiments no significant differences were detected in the frequency of acrosome-reacted sperm either by double staining (37.98%) or by FITC-PSA labelling (39.33%). The viability of sperm stained by the double staining method was 67.17%, and a higher portion of viable sperm (82.67%) was observed by staining with the Hoechst procedure (P < 0.01). On the basis of the results obtained it is concluded that both methods can be used for detecting the acrosome reaction of frozen-thawed bovine spermatozoa.

Role of complement regulatory proteins CD46, CD55 and CD59 in reproduction

Abstract. In humans, CD46 has been detected on the acrosomal membrane in sperm, in contrast to widespread surface expression on somatic cells where it plays a key role in the protection from complement attack. In rodents, CD46 is expressed solely on the acrosomal membrane of mature sperm and their immediate precursors, spermatids. A monoclonal antibody against the short consensus repeat (SCR1) ectodomain of CD46 blocks binding of human sperm to zona-free oocytes in vitro. However, CD46-knockout mice are fertile and have an accelerated spontaneous acrosome reaction. Wild-caught field mice (Apodemus) also exhibit a rapid acrosome reaction and CD46 is not expressed in Apodemus sperm. CD46 may, therefore, play a role in stabilization of the acrosomal membrane. Two other complement regulatory proteins, CD55 and CD59, are localized on the plasma membrane of mammalian sperm. In human sperm, CD55 and CD59 are expressed also on the inner acrosomal membrane. It remains to be clarified what is the role of CD46, CD55 and CD59 during fertilization and what are the advantages of not expressing CD46 in field mice sperm.

Analysis of the expression of platelet antigens CD9 and CD41/61 in transgenic rabbits with the integrated human blood clotting factor VIII gene construct.

The objective of this research was to study the expression of cell membrane molecules CD9 and CD41/61 of transgenic rabbit with integrated human factor VIII (rhFVIII) gene construct. The expressions of these molecules have been monitored during two lactations of transgenic rabbits and simultaneously compared with the expression of the same molecules of non-transgenic rabbits. The immunochemical analysis by indirect immunofluorescence, ELISA and indirect immunoperoxidase staining of blood cells and udder tissues show that the insertion of the WAP-hFVIII gene construct into the rabbit genome, do not influence the expression of cell membrane antigens CD9 and CD41/61 on the blood platelets, polymorphonuclear blood cells, milk somatic cells and mammary gland tissues.

Characterization of tetraspanin protein CD81 in mouse spermatozoa and bovine gametes.

Sperm-egg interaction and fusion represent a key moment of fertilization. In mammals, it is not possible without the interaction of the tetraspanin superfamily proteins including CD81. A detailed immunohistochemical localization of CD81 was monitored in bovine oocytes during different maturation stages, as well as during early embryogenesis. In addition, characterization of CD81 was carried out in bovine and mouse sperm. In bovine eggs, CD81 was detected on the plasma membrane of the germinal vesicle, metaphase I and metaphase II oocytes. During fertilization, accumulation of CD81 molecules in the perivitelline space of fertilized oocytes, which appeared as vesicles associated with plasma membrane, was observed. In majority of bull-ejaculated sperm and caput, corpus and cauda epididymal sperm, as well as mouse cauda epididymal sperm, CD81 was found on the plasma membrane covering the apical acrosome. Although the process of capacitation did not influence the localization of CD81, it was lost from the surface of the acrosome-reacted spermatozoa in bull, in contrast to mouse sperm where there was a relocalization of the CD81 protein during acrosome reaction across the equatorial segment and later over the whole sperm head. The presented results highlight conservative unifying aspects of CD81 expression between cattle and mouse, together with mouse-specific traits in sperm CD81 behaviour, which emphasizes certain species-specific mechanisms of fertilization to be considered.

Comparative fluorescence analysis of the bovine sperm using IVA-520 (anti-CD46 antibody) and lectins: probable localisation of CD46 on bovine sperm membrane.

Membrane cofactor protein (CD46) is complement regulatory protein with probable function in the reproduction process. Expression of CD46 on human, mice, rat and guinea pig spermatozoa is restricted to the inner acrosomal membrane. In spite of the presence of anti-sperm antibodies and other potential complement activating agents in follicular fluid, CD46 is not expressed on the plasma membrane of spermatozoa as the other complement regulatory proteins (DAF and CD59) in human. Using dual immunofluorescence labelling with mAb IVA-520 (anti-bovine CD46) and various lectins with different binding pattern or monoclonal antibody ACR.4, targeted against intra-acrosomal protein, we excluded the expression of CD46 on the inner acrosomal membrane as well as in the acrosomal content but, we suggested the localization of this molecule on the outer acrosomal membrane and possibly on the plasma membrane of bovine sperm.

Identification of bovine CD52-like molecule by monoclonal antibody IVA-543: distribution of CD52-like molecule in the bull genital tract

The bovine maturation-associated sperm membrane antigen CD52-like molecule has been analysed using a mouse anti-sperm monoclonal antibody developed against bull spermatozoa. The antigen recognised by monoclonal antibody IVA-543 was detected on blood mononuclear cells (including lymphocytes and monocytes) and on a minor population of polymorphonuclear leukocytes. The bovine CD52-like molecule is secreted by the epididymal epithelium and then it is inserted into the sperm membrane during the epididymal transport in the distal part of epididymis. The CD52-like molecule was absent from spermatozoa derived from testes, and the highest proportion of IVA-543-reactive sperm was observed in the cauda epididymis (91.6%). This study has shown that the new molecule identified on bovine cells has properties analogous to those previously described for CD52 molecules in man, mouse, rat, monkey, and dog.

CD9 and CD81 Interactions and Their Structural Modelling in Sperm Prior to Fertilization

Proteins CD9 and CD81 are members of the tetraspanin superfamily and were detected in mammalian sperm, where they are suspected to form an active tetraspanin web and to participate in sperm–egg membrane fusion. The importance of these two proteins during the early stages of fertilization is supported by the complete sterility of CD9/CD81 double null female mice. In this study, the putative mechanism of CD9/CD81 involvement in tetraspanin web formation in sperm and its activity prior to fertilization was addressed. Confocal microscopy and colocalization assay was used to determine a mutual CD9/CD81 localization visualised in detail by super-resolution microscopy, and their interaction was address by co-immunoprecipitation. The species-specific traits in CD9 and CD81 distribution during sperm maturation were compared between mice and humans. A mutual position of CD9/CD81 is shown in human spermatozoa in the acrosomal cap, however in mice, CD9 and CD81 occupy a distinct area. During the acrosome reaction in human sperm, only CD9 is relocated, compared to the relocation of both proteins in mice. The structural modelling of CD9 and CD81 homologous and possibly heterologous network formation was used to propose their lateral Cis as well as Trans interactions within the sperm membrane and during sperm–egg membrane fusion.

Evaluation of protein phosphorylation in bull sperm during their maturation in the epididymis

Phosphorylation, or dephosphorylation, is one of the most frequent post-translational modifications regulating protein–protein activity in eukaryotic cells. Whereas mature spermatozoa (as specialized cells) are transcriptionally inactive and do not synthesize new proteins, phosphorylation of sperm proteins is very important for the regulation of the sperm function. Although the post-testicular maturation of spermatozoa is a process common to all mammals, comparative studies showed significant differences in sperm surface proteins and the mechanisms of protein modification during the epididymal maturation. In our study, the evaluation of tyrosine phosphorylation, represented by the fluorescent patterns of used anti-phosphotyrosine antibodies (P-Tyr-01 and 4G10), in spermatozoa isolated from different regions of the epididymis — caput, corpus and cauda — was performed. Although in general both antibodies detected almost the same reaction patterns, we observed some dissimilarity associated with the binding specificity of the antibodies and also the segment-dependent manner of phosphorylated protein localization. These data were filled up by immunohistochemical analysis of testes and epididymides cryosections. Additionally, our phosphoproteomic study focused on evaluation of the changes in the pattern of tyrosine-phosphorylated proteins during the post-testicular maturation of bull spermatozoa (PY20 antibody). To summarize the results, an increasing trend of tyrosine phosphorylation of proteins during the maturation of bull sperm in the epididymis was consistently observed in all the methods/experiments.