Characterization of β-defensin 42 expressed in principal cells at the initial segment of the rat epididymis

β-defensins, preferentially expressed in male reproductive tracts, particularly in the testes and epididymis with region-specific patterns, play an important role in both innate immunity and sperm fertility. Expressed in the caput region of epididymis, β-defensins have been known to contribute to innate immunity, sperm motility initiation, and maintenance. However, β-defensins of the initial region remain to be uncharacterized. In this study, rat β-defensin 42 (Defb42) was revealed to be exclusively located in the principal cells at the initial segment of the rat epididymis and its sperm's acrosome. Furthermore, the expression of Defb42 was dependent on luminal testicular factors and developmental phases. The recombinant Defb42 was predominantly antimicrobial not against Candida albicans, but against Escherichia coli and Staphylococcus aureus. Based on these findings, Defb42 was suggested to play a dual role in sperm fertility and host defense in rat epididymis.

Lectin staining and flow cytometry reveals female-induced sperm acrosome reaction and surface carbohydrate reorganization

All cells are covered by glycans, an individually unique layer of oligo- and polysaccharides that are critical moderators of self-recognition and other cellular-level interactions (e.g. fertilization). The functional similarity between these processes suggests that gamete surface glycans may also have an important, but currently overlooked, role in sexual selection. Here we develop a user-friendly methodological approach designed to facilitate future tests of this possibility. Our proposed method is based on flow cytometric quantification of female-induced sperm acrosome reaction and sperm surface glycan modifications in the Mediterranean mussel Mytilus galloprovincialis. In this species, as with many other taxa, eggs release water-soluble factors that attract conspecific sperm (chemoattraction) and promote potentially measurable changes in sperm behavior and physiology. We demonstrate that flow cytometry is able to identify sperm from other seawater particles as well as accurately measure both acrosome reaction and structural modifications in sperm glycans. This methodological approach can increase our understanding of chemically-moderated gamete-level interactions and individual-specific gamete recognition in Mytilus sp. and other taxa with similar, easily identifiable acrosome structure. Our approach is also likely to be applicable to several other species, since carbohydrate-mediated cellular-level interactions between gametes are universal among externally and internally fertilizing species.

Liprin α3: a putative estrogen regulated acrosomal protein

Liprin α3 was reported for the first time using sperm proteomics. Present study reports its localization on sperm and immunochemical characterization. Liprin α3 is identified as a 133 kDa protein in testis and epididymal protein extracts. In testis, immunohistochemical localization was seen in pachytenes, diplotenes, round spermatids whereas it was localized in the epithelial cells and luminal sperm in all the three regions of epididymis. Protein was localized in acrosome of rat sperm, which was further confirmed by sequential treatment of sperm with hypertonic solution. In the spermatogenic cells the protein was found to be located in developing acrosome as evident by its co-localization with Golgi marker. Protein was found to be developmentally regulated. In silico analysis of Liprin α3 revealed presence of the estrogen responsive elements upstream to initiation site and its regulation by estrogen was experimentally validated using a tamoxifen treated rat model. Western blot analysis of epididymosomes showed the presence of Liprin α3, indicating its involvement in trafficking of vesicle. The protein expression was seen in both mouse and human sperm indicating conserved nature and a probable role in acrosome reaction.

Identification and disruption of sperm-specific angiotensin converting enzyme-3 (ACE3) in mouse

BACKGROUND

IZUMO1 is the only sperm protein which is proven to be essential for sperm-egg fusion. However, the IZUMO1 is a structurally simple protein with single Ig domain and seems not to include either a "fusogenic peptide" or a fusion machinery domain. This led us to assume the existence of an IZUMO1-interacting protein(s) which makes a functional fusion machine interacting with IZUMO1.

METHODOLOGY/PRINCIPAL FINDINGS

We produced a transgenic mouse line which expresses His-tagged IZUMO1 in the Izumo1(-/-) genetic background. After solubilization of sperm membranes, we purified His-tagged IZUMO1 using anti-His affinity chromatography and found a protein that interacts with IZUMO1. After being separated on SDS-PAGE gel, the IZUMO1-interacting protein was subjected to LC-MS/MS analysis and from the partial fragments, we identified the protein as ACE3. We raised the antibody against ACE3 and found that ACE3 is localized on the acrosomal cap area as in the case of IZUMO1. However, ACE3 disappeared from sperm after acrosome reaction while IZUMO1 remained on sperm. In order to investigate the role of ACE3 in vivo, we generated Ace3-deficient mice by homologous recombination and examined the fertilizing ability of the males. Unexpectedly, the male mice showed no defect in fertilizing ability in in vivo or in an in vitro fertilization system.

CONCLUSIONS/SIGNIFICANCE

We identified an IZUMO1-interacting protein in sperm, which we identified as testis specific ACE homologue ACE3. We produced an Ace3 disrupted mouse line, and found the localization of IZUMO1 spread in a little wider area on sperm, but the elimination of ACE3 did not result in a loss of sperm fertilizing ability, differing from the case of ACE disruption.

Transgenic mouse sperm that have green acrosome and red mitochondria allow visualization of sperm and their acrosome reaction in vivo

In the present paper, we introduce a transgenic mouse line whose sperm express green fluorescent protein (GFP) in their acrosome and red fluorescent protein (RFP) in their mitochondria [B6D2F1- Tg(CAG/su9-DsRed2, Acr3-EGFP)RBGS002Osb]. The dual fluorescent sperm showed normal fertilizing ability in both in vivo and in vitro fertilization and the sperm could be observed through uterine and oviductal walls when female reproductive tracts were dissected out and placed under excitation light. This characteristic could facilitate examination of sperm migration inside the female reproductive tract as well as facilitating in situ live imaging of the acrosome reaction, the details of which have remained elusive.

PRESENCE OF N-ETHYL MALEIMIDE SENSITIVE FACTOR (NSF) ON THE ACROSOME OF MAMMALIAN SPERM

We have extended previous observations to show that the ATPase N-ethyl maleimide sensitive factor (NSF) an important regulator of membrane trafficking and fusion in somatic cells, is present on bovine, murine and rhesus macaque sperm. However, NSFs main effectors, alfa- and beta-SNAP, although present in the developing acrosome, could not be detected in the mature organelle. The fact that NSF localizes mainly to the acrosome suggests that this protein, together with other factors such as rabs and SNAREs, may be a common feature in the triggering/regulation of membrane merging during the mammalian acrosome reaction.

Relevance of glycosylation of human zona pellucida glycoproteins for their binding to capacitated human spermatozoa and subsequent induction of acrosomal exocytosis

To delineate the functional aspects of zona pellucida (ZP) glycoproteins during fertilization in human, in the present study, fluorochrome-conjugated Escherichia coli (E. coli)- and baculovirus-expressed recombinant human ZP glycoprotein-2 (ZP2), -3 (ZP3), and -4 (ZP4) were employed. In an immunofluorescence assay, capacitated human sperm exhibited binding of the baculovirus-expressed recombinant ZP3 as well as ZP4 to either acrosomal cap or equatorial region whereas acrosome-reacted sperm failed to show any binding to the acrosomal cap. Using double labeling experiments, simultaneous binding of ZP3 and ZP4 to the acrosomal cap was observed suggesting the possibility of different binding sites of these proteins on the sperm surface. No binding of ZP2 was observed to the capacitated sperm. However, acrosome-reacted sperm (20.00 +/- 1.93%) showed binding of ZP2 that was restricted to only equatorial region. Interestingly, E. coli-expressed recombinant human zona proteins also showed very similar binding profiles. Competitive inhibition studies with unlabeled recombinant human zona proteins revealed the specificity of the above binding characteristics. Binding characteristics have been further validated by an indirect immunofluorescence assay using native human heat solubilized isolated zona pellucida. Employing baculovirus-expressed recombinant ZP3 and ZP4 with reduced N-linked glycosylation and respective E. coli-expressed recombinant proteins, it was observed that glycosylation is required for induction of acrosomal exocytosis but its absence may not compromise on their binding ability. These studies have revealed the binding profile of individual human zona protein to spermatozoa and further strengthened the importance of glycosylation of zona proteins for acrosomal exocytosis in spermatozoa.

Expression of bisecting type and Lewisx/Lewisy terminated N-glycans on human sperm

Human sperm lack major histocompatibility class I molecules, making them susceptible to lysis by natural killer (NK) cells. Major histocompatibility class I negative tumor cells block NK cell lysis by expressing sufficient amounts of bisecting type N-glycans on their surfaces. Therefore, sperm could employ the same strategy to evade NK cell lysis. The total N-glycans derived from sperm were sequenced using ultrasensitive mass spectrometric and conventional approaches. Three major classes of N-glycans were detected, (i) high mannose, (ii) biantennary bisecting type, and (iii) biantennary, triantennary, and tetraantennary oligosaccharides terminated with Lewisx and Lewisy sequences. Immunostaining of normal sperm showed that glycoproteins bearing Lewisy sequences are localized to the acrosome and not the plasma membrane. In contrast, defective sperm showed distinct surface labeling with anti-Lewisy antibody. The substantial expression of high mannose and complex type N-glycans terminated with Lewisx and Lewisy sequences suggests that sperm glycoproteins are highly decorated with ligands for DC-SIGN. Based on previous studies, the addition of such carbohydrate signals should inhibit antigen-specific responses directed against sperm glycoproteins in both the male and female reproductive systems. Thus, the major N-glycans of human sperm are associated with the inhibition of both innate and adaptive immune responses. These results provide more support for the eutherian fetoembryonic defense system hypothesis that links the expression of carbohydrate functional groups to the protection of gametes and the developing human in utero. This study also highlights the usefulness of glycomic profiling for revealing potential physiological functions of glycans expressed in specific cell types.

Vezatin, a ubiquitous protein of adherens cell-cell junctions, is exclusively expressed in germ cells in mouse testis

In the male reproductive organs of mammals, the formation of spermatozoa takes place during two successive phases: differentiation (in the testis) and maturation (in the epididymis). The first phase, spermiogenesis, relies on a unique adherens junction, the apical ectoplasmic specialization linking the epithelial Sertoli cells to immature differentiating spermatids. Vezatin is a transmembrane protein associated with adherens junctions and the actin cytoskeleton in most epithelial cells. We report here the expression profile of vezatin during spermatogenesis. Vezatin is exclusively expressed in haploid germ cells. Immunocytochemical and ultrastructural analyses showed that vezatin intimately coincides, temporally and spatially, with acrosome formation. While vezatin is a transmembrane protein associated with adherens junctions in many epithelial cells, it is not seen at the ectoplasmic specializations, neither at the basal nor at the apical sites, in the seminiferous epithelium. In particular, vezatin does not colocalize with espin and myosin VIIa, two molecular markers of the ectoplasmic specialization. In differentiating spermatids, ultrastructural data indicate that vezatin localizes in the acrosome. In epididymal sperm, vezatin localizes also to the outer acrosomal membrane. Considering its developmental and molecular characteristics, vezatin may be involved in the assembly/stability of this spermatic membrane.

CD55 in rat male reproductive tissue: Differential expression in testis and expression of a unique truncated isoform on spermatozoa

CD55 is a key regulator of complement activation, expressed on most tissues and cells in man and other mammals. In the rat, alternative splicing in the gene encoding CD55 yields GPI-anchored (GPI-CD55) and transmembrane (TM-CD55) forms. Published Northern blot analysis indicated that while GPI-CD55 was broadly expressed, TM-CD55 was primarily expressed in the testis, although the precise site of expression was not identified. To clarify the distribution of CD55 isoforms in rat reproductive tissues, we first performed immunohistochemistry and Western blot analysis with an anti-rat CD55 mAb that recognized all reported CD55 isoforms, and a polyclonal immunoglobulin specific for TM-CD55. CD55 was absent in testis prior to puberty. Post-puberty, CD55 was expressed at high levels on all spermiogenic cells from step 6 spermatid onward, and on mature spermatozoa focussed on the acrosome, but was absent from support cells and early progenitors. Enzymatic digestion revealed that GPI-CD55 was predominant in testis and spermatozoa. Staining for TM-CD55 with specific immunoglobulin confirmed its absence from mature sperm and expression on spermatids only between steps 11 and 14 of development. GPI-CD55 on spermatozoa was of lower molecular weight than that in testis and other tissues; sequencing from spermatozoal mRNA identified a unique isoform of GPI-CD55 missing short consensus repeat 4. The predominant acrosome expression and presence of a unique, truncated isoform of CD55 on spermatozoa provides further support for the hypothesis that the acrosome is a highly specialized region in which closely regulated complement activation may contribute to reproductive function.

Sperm plasma membrane breakdown during Drosophila fertilization requires Sneaky, an acrosomal membrane protein

Fertilization typically involves membrane fusion between sperm and eggs. In Drosophila, however, sperm enter eggs with membranes intact. Consequently, sperm plasma membrane breakdown (PMBD) and subsequent events of sperm activation occur in the egg cytoplasm. We previously proposed that mutations in the sneaky (snky) gene result in male sterility due to failure in PMBD. Here we support this proposal by demonstrating persistence of a plasma membrane protein around the head of snkysperm after entry into the egg. We further show that snky is expressed in testes and encodes a predicted integral membrane protein with multiple transmembrane domains, a DC-STAMP-like domain, and a variant RING finger. Using a transgene that expresses an active Snky-Green fluorescent protein fusion (Snky-GFP), we show that the protein is localized to the acrosome, a membrane-bound vesicle located at the apical tip of sperm. Snky-GFP also allowed us to follow the fate of the protein and the acrosome during fertilization. In many animals, the acrosome is a secretory vesicle with exocytosis essential for sperm penetration through the egg coats. Surprisingly, we find that the Drosophila acrosome is a paternally inherited structure. We provide evidence that the acrosome induces changes in sperm plasma membrane, exclusive of exocytosis and through the action of the acrosomal membrane protein Snky. Existence of testis-expressed Snky-like genes in many animals, including humans, suggests conserved protein function. We relate the characteristics of Drosophila Snky, acrosome function and sperm PMBD to membrane fusion events that occur in other systems.

Proteomic analysis of sperm regions that mediate sperm-egg interactions

The sperm interacts with three oocyte-associated structures during fertilization: the cumulus cell layer surrounding the oocyte, the egg extracellular matrix (the zona pellucida), and the oocyte plasma membrane. Each of these interactions is mediated by the sperm head, probably through proteins both on the sperm surface and within the acrosome, a specialized secretory granule. In this study, we have used subcellular fractionation in order to generate a proteome of the sperm head subcellular compartments that interact with oocytes. Of the proteins we identified for which a gene knockout has been tested, a third have been shown to be essential for efficient reproduction in vivo. Many of the other presently untested proteins are likely to have a similarly important role. Twenty-five percent of the cell surface fraction proteins are previously uncharacterized. We have shown that at least two of these novel proteins are localized to the sperm head. In summary, we have identified over 100 proteins that are expressed on mature sperm at the site of sperm-oocyte interactions.

[Inhibin B and intraacrosomal proteins in men from the couples with fertility disorders]

THE AIM

To monitor the basic andrologic and immunologic sperm factors and the levels of inhibin B in serum and in seminal plasma in men from the couples with infertility disorders.

SETTING

Department of Gynecology and Obstetrics, Medical School, Charles University and University Hospital, Plzen, Institute of Molecular Genetics, AV CR, Prague, Institute of Clinical Immunology and Allergology, LF UK a FN, Plzen.

METHODS

We used conventional methods for estimation of sperm quality according to WHO and we detected the intra-acrosomal proteins by monoclonal antibodies (Hs8 and Hs14, immunofluorescent method), spermantibodies by direct mixed antiimunoglobulin reaction (MAR) test, and we examined inhibin B in serum (< or =400 pg/ml= A) and in seminal plasma (< or = 600 pg/ml= N) by ELISA in 355 men aged 21-52 years (ø 34 years) with normal levels of FSH, LH and testosterone. The control group was created by 56 health sperm donors.

RESULTS

We found 65% normospermatics in the group of 355 patients, 34.9% men with various kind of pathologies. Predominance of spermagglutinating antibodies was found in 15.77% in IgG, in 19.44% in IgA, in 8.44% in IgA and IgG together. Normal intraacrosomal proteins were reached in 74.65% for Hs8, in 20.85% pathologic, in 86.2% normal findings for Hs14, in 4.23% pathologic. The immunological results in control group were completaly negative. Pathological levels of inhibin B in seminal plasma was found in 37.2% (152 men), in 25% in serum, and in 5.6% in serum and in seminal plasma together. In 54.7% of patients we found physiological levels of inhibin B in both biological fluids. We also compared physiological 109/152 (71.71%), and pathological spermiogrammes 43/152 (28.29%) with abnormal levels of inhibin B in seminal plasma, with intraacrosomal proteins to levels of inhibin B in serum. Our detailed study shows high interidividual results, which must be studied in complex with diagnosis of decreased fertility in man.

CONCLUSION

Andrologic and immunologic analysis in the group of 355 men showed normal parameters of spermiogrammes in 231 patients (65%), in the rest of men the immunologic profil was in various parts pathologic. Only 105 men have got excellent spermiogrammes. Inhibin B as hormon regulates in back the secretion of FSH, and serves as good indicator in male reproductive failures.

Differential expression of glucose transporter GLUT8 during mouse spermatogenesis

GLUT8 is a facilitative glucose transporter expressed at high levels in the testis. In this study, we analyzed the GLUT8 expression in mouse testis during spermatogenesis by RT–PCR, Western blot and immunohistochemistry methods. Our results show that GLUT8 expression is limited to spermatids and spermatozoa in the testis. Expression begins when round spermatids are formed at postnatal day 24. The expression persists throughout spermiogenesis, and it is also detected in spermatozoa, but it is absent in more immature germ cells, Sertoli cells and interstitial tissue. GLUT8 immunoreactivity is always restricted to the acrosomic system in a manner that matches the acrosome system formation. The GLUT8 expression is mainly associated with the acrosomic membrane in the acrosome, although significant immunoreactivity is also found inside the acrosomic lumen. The specific GLUT8 location suggests that this transporter plays a pivotal role in the fuel supply of spermatozoa, and in the traffic of sugars during the capacitation and fertilization processes.

The RING-Finger Protein Haprin: Domains and Function in the Acrosome Reaction

The RBCC (RING finger, B-box type zinc finger, coiled-coil domain) motif family contains a large number of proteins implicated in many cellular processes, including vesicle exocytosis. The acrosome reaction, the sperm exocytotic event that is required for fertilization, involves essentially the same process of intracellular membrane fusions as vesicular exocytosis in somatic cells. We have previously isolated a haploid-germ-cell-specific gene designated haprin, which encodes a RBCC motif protein that plays a role in the acrosome reaction of sperm by mediating protein complex formation via the RBCC motif. In this review, we describe the potential role of Haprin in the molecular mechanisms of acrosome reaction, as compared with some other RBCC proteins. The conserved structure and localization of the Haprin protein in human and mouse suggest an indispensable role for Haprin in the functioning of mammalian sperm.

Histochemical analysis of glycoconjugates in the domestic cat testis

The localization and characterization of oligosaccharide sequences in the cat testis was investigated using 12 lectins in combination with the beta-elimination reaction, N-Glycosidase F and sialidase digestion. Leydig cells expressed O-linked glycans with terminal alphaGalNAc (HPA reactivity) and N-glycans with terminal/internal alphaMan (Con A affinity). The basement membrane showed terminal Neu5Acalpha2,6Gal/GalNAc, Galbeta1,3GalNAc, alpha/betaGalNAc, and GlcNAc (SNA, PNA, HPA, SBA, GSA II reactivity) in O-linked oligosaccharides, terminal Galbeta1,4GlcNAc (RCA120 staining) and alphaMan in N-linked oligosaccharides; in addition, terminal Neu5acalpha2,3Galbeta1,4GlcNac, Forssman pentasaccharide, alphaGal, alphaL-Fuc and internal GlcNAc (MAL II, DBA, GSA I-B4, UEA I, KOH-sialidase-WGA affinity) formed both O- and N-linked oligosaccharides. The Sertoli cells cytoplasm contained terminal Neu5Ac-Galbeta1,4GlcNAc, Neu5Ac-betaGalNAc as well as internal GlcNAc in O-linked glycans, alphaMan in N-linked glycoproteins and terminal Neu5Acalpha2,6Gal/ GalNAc in both O- and N-linked oligosaccharides. Spermatogonia exhibited cytoplasmic N-linked glycoproteins with alphaMan residues. The spermatocytes cytoplasm expressed terminal Neu5Acalpha2,3Galbeta1,4 GlcNAc and Galbeta1,3GalNAc in O-linked oligosaccharides, terminal Galbeta1,4GlcNAc and alpha/betaGalNAc in N-linked glycoconjugates. The Golgi region showed terminal Neu5Acalpha2,3Galbeta1,4GlcNac, Galbeta1,4GlcNAc, Forssman pentasaccharide, and alphaGalNAc in O-linked oligosaccharides, alphaMan and terminal betaGal in N-linked oligosaccharides. The acrosomes of Golgi-phase spermatids expressed terminal Galbeta1,3GalNAc, Galbeta1,4GlcNAc, Forssmann pentasaccharide, alpha/betaGalNAc, alphaGal and internal GlcNAc in O-linked oligosaccharides, terminal alpha/betaGalNAc, alphaGal and terminal/internal alphaMan in N-linked glycoproteins. The acrosomes of cap-phase spermatids lacked internal Forssman pentasaccharide and alphaGal, while having increased alpha/betaGalNAc. The acrosomes of elongated spermatids did not show terminal Galbeta1,3GalNAc, displayed terminal Galbeta1,4GlcNAc and alpha/betaGalNAc in N-glycans and Neu5Ac-Galbeta1,3GalNAc in O-linked oligosaccharides.

Identification of voltage-dependent Ca2+channels in sea urchin sperm

Functional evidence indicates that voltage-dependent Ca2+ (Cav) channels participate in sea urchin sperm motility and the acrosome reaction (AR), however, their molecular identity remains unknown. We have identified transcripts for two Ca2+ channel alpha1 subunits in sea urchin testis similar in sequence to Cav1.2 and Cav2.3. Antibodies against rat Cav1.2 and Cav2.3 channels differentially label proteins in the flagella and acrosome of mature sea urchin sperm. The Cav channel antagonists nifedipine and nimodipine, which inhibit the AR, diminish the intracellular Ca2+ elevation induced by a K+-induced depolarization in valinomycin-treated sperm. These findings reveal that Cav1.2 and Cav2.3 channels could participate in motility and/or the AR in sea urchin sperm.

Localization of phosphatidylserine in boar sperm cell membranes during capacitation and acrosome reaction

One of the essential properties of mammalian, including sperm, plasma membranes is a stable transversal lipid asymmetry with the aminophospholipids, phosphatidylserine (PS) and phosphatidylethanolamine (PE), typically in the inner, cytoplasmic leaflet. The maintenance of this nonrandom lipid distribution is important for the homeostasis of the cell. To clarify the relevance of lipid asymmetry to sperm function, we have studied the localization of PS in boar sperm cell membranes. By using labeled annexin V as a marker for PS and propidium iodide (PI) as a stain for nonviable cells in conjunction with different methods (flow cytometry, fluorescence and electron microscopy), we have assessed the surface exposure of PS in viable cells during sperm genesis, that is, before and during capacitation as well as after acrosome reaction. An approach was set up to address also the presence of PS in the outer acrosome membrane. The results show that PS is localized in the cytoplasmic leaflet of the plasma membrane as well as on the outer acrosome membrane. Our results further indicate the cytoplasmic localization of PS in the postacrosomal region. During capacitation and acrosome reaction of spermatozoa, PS does not become exposed on the outer surface of the viable cells. Only in a subpopulation of PI-positive sperm cells does PS became accessible upon capacitation. The stable cytoplasmic localization of PS in the plasma membrane, as well as in the outer acrosome membrane, is assumed to be essential for a proper genesis of sperm cells during capacitation and acrosome reaction.

Identification and characterization of rDJL, a novel member of the DnaJ protein family, in rat testis

Applying the method of segmentation of seminiferous tubules combined with DDRT-PCR and cDNA library screening, a novel DnaJ homologue, rDJL was identified in rat testis. The reading frame encodes a protein of 223 amino acid residues containing J domain in the NH2 terminal region. rDJL gene is expressed mainly in testis and rDJL protein was immunolocalized notably in the acrosome region of spermatozoa. Immunoprecipitation experiments showed that rDJL interacted with Hsc70 and clathrin protein. When CHO cells were treated with EGF, rDJL and clathrin protein were found to be colocalized and be concentrated as endosome vesicles. The present findings suggest that rDJL functions as co-chaperone to Hsc70, participates in vesicular trafficking and may play an important role in acrosomogenesis.

Effects of cryo-injury on progesterone receptor(s) of canine spermatozoa and its response to progesterone

The integrity of sperm progesterone (P4) receptor(s) and its response to steroid stimulation might be crucial for the maintenance of sperm fertilizing ability after cryopreservation. The aim of the current investigation was to study the effect of cryo-procedures on canine sperm P4 receptor(s). In addition, alteration of P4 receptor(s) at the molecular level and their functional integrity following cryo-procedures was evaluated. Fresh and frozen-thawed semen samples (n=6 same dogs) after capacitation were treated with 10 microg/mL P4 to induce the acrosome reaction (AR, FITC-PNA staining). Parallel samples were treated with 50% canine seminal plasma (SP) prior to AR induction with P4. The percentages of AR in capacitated fresh and frozen-thawed semen samples after treatment with P4 were 31.0+/-6.7 and 21.6+/-4.1% (P<0.05), respectively. The percentage of AR in fresh and frozen-thawed semen samples pretreated with SP and incubated with P4 was; 11.5+/-4.8 and 16.5+/-2.0% (P<0.05), respectively. The incidence of the spontaneous AR (P>0.05) in fresh and frozen-thawed semen samples at the onset (5.5+/-2.2 and 6.1+/-1.8%; respectively) and after a 2h (9.6+/-5.1 and 10.4+/-2.7%; respectively) capacitation, avoiding P4 stimulation, were not different. The percentage of progesterone-BSA-FITC staining over the acrosomal region was 18.3+/-10.3% in fresh semen, 36.0+/-11.9% in capacitated (P<0.05) and less than 5% in SP treated spermatozoa. This staining was barely visible in frozen-thawed spermatozoa regardless of capacitation status. In western blot analysis, mAb C262 recognized two bands (54 and 65 kDa). Digitonin treated fresh and frozen-thawed spermatozoa, labeled with [3H]-progesterone, revealed that the P4 binding capacity decreased from 6.0+/-4.4 in fresh to 3.0+/-2.1 nM in frozen-thawed spermatozoa. In nearly all samples tested (except one) 65 kDa protein band decreased significantly after freeze-thaw procedures while the 54kDa protein was increased. These results indicate that the reduced incidence of AR in response to P4 in frozen spermatozoa is possibly due to the conformational changes of P4 receptor(s) and/or reduced P4 receptor density derived from freezing injury.

SNARE proteins and caveolin-1 in stallion spermatozoa: possible implications for fertility

Proteins implicated in the "SNARE hypothesis" for membrane fusion have been characterized in the acrosome of several mammalian species, and a functional role for these proteins during the acrosome reaction has been proposed. We have investigated the presence of SNAREs in equine sperm, using semen samples obtained from stallions with varying fertility. Immunocytochemical analysis revealed that members of different SNARE families can be detected on the acrosome of equine sperm, notably in the acrosomal cap and equatorial segment. These proteins include the t-SNARE syntaxin, the v-SNARE synaptobrevin/VAMP, the calcium sensor synaptotagmin, and the ATPase NSF. Also present is caveolin-1, a component of lipid rafts. Stallions with fertility problems presented the worst quality of sperm and acrosomal membrane, and had less sperm cells stained positively for SNAREs and caveolin-1, than sperm from fertile donors (p < 0.001). Ubiquitin surface staining was also performed and it seemed to inversely correlate with stallion fertility, supporting data obtained with the negative staining technique. A male-related problem was confirmed when mares that had failed to impregnate with samples from an infertile stallion were successfully inseminated with sperm from a fertile donor. Furthermore NSF, synaptotagmin and caveolin-1 staining seemed to be useful in predicting stallion fertility, i.e. significantly more sperm cells stained positively for these proteins in samples from fertile males. Although these results need to be expanded on a larger scale, they suggest that acrosomal and surface staining of equine sperm with novel probes may constitute useful tools in predicting stallion fertility.

Actin polymerization in the equatorial and postacrosomal regions of guinea pig spermatozoa during the acrosome reaction is regulated by G proteins

The acrosome reaction (AR) is an exocytotic process of spermatozoa, and an absolute requirement for fertilization. During AR, actin polymerization is necessary in the equatorial and postacrosomal regions of guinea pig sperm for spermatozoa incorporation deep into the egg cytoplasm, but not for plasma membrane (PM) fusion nor the early steps of egg activation. To identify the mechanisms involved in this sperm actin polymerization, we searched for the protein members, known to be involved in a highly conserved model, that may apply to any cellular process in which de novo actin polymerization occurs from G protein activation. WASP, Arp 2/3, profilins I and II, and Cdc42, RhoA and RhoB GTPases were localized by indirect immunofluorescence (IIF) in guinea pig spermatozoa and their presence corroborated by Western blotting. WASP and profilin II were translocated to the postacrosomal region (Arp2/3 already were there) in long-term capacitated and acrosome-reacted spermatozoa, at the same time as actin polymerization occurred. These events were inhibited by GDP-beta-S and promoted by lysophosphatidic acid (LPA) and GTP-gamma-S, a small GTPase inhibitor and two activators, respectively. By immunoprecipitation, Cdc42-WASp association was identified in capacitated but not in noncapacitated gametes. Polymerized actin in the postacrosomal region is apparently anchored both to the postacrosomal perinuclear theca region and the overlying PM. Results suggest that GTPases are involved in sperm actin polymerization, in the postacrosomal region and the mechanism for polymerization might fit a previously proposed model (Mullins, 2000: Curr Opin Cell Biol 12:91-96).

The clathrin interacting protein Clint/epsinR in rat testicular germ cells

The plasma membrane and the trans-Golgi network (TGN) are major intracellular sites for clathrin-mediated membrane budding. Only recently has the clathrin interacting protein Clint/epsinR/enthoprotin been identified, which is thought to be involved in clathrin-dependent membrane budding from the TGN. Using immunocytochemistry, we now report the presence of Clint in the Golgi region of spermatocytes and spermatids of the rat testis. Together with subcellular fractionation experiments, our data show that, in male germ cells, Clint behaves as a peripheral membrane protein that is probably involved in TGN-related vesicle budding. Moreover, the immunostaining of the acrosome in round and elongating spermatids indicates that Clint operates in membrane traffic between the TGN and the acrosome. It may thus be speculated that the protein is involved in the biogenesis and shaping of acrosomal membranes.

Germ cell-specific localization of immunoreactive riboflavin carrier protein in the male golden hamster: appearance during spermatogenesis and role in sperm function

Riboflavin carrier protein (RCP) is a phosphoglycoprotein (37 kDa) that is well studied in chicken. An immunologically cross-reacting protein was identified in mammals and active immunization of male rats and bonnet monkeys with chicken RCP lead to an approximately 80% reduction in fertility. However, the physiological mechanism responsible for inhibition of male fertility has not been investigated. Moreover, information on the cell type-specific localization and the origin of immunoreactive RCP during spermatogenesis is extremely limited. Hence, studies were carried out to determine the pattern of expression of immunoreactive RCP during spermatogenesis and its role in sperm function in the golden hamster. Immunoreactive RCP was germ cell-specific, found to be associated with the acrosome-organizing region of early spermatids and showed interesting patterns of immunolocalization during late stages of spermiogenesis. Mature spermatozoa exhibited acrosome-specific localization, mainly in the peri-acrosomal membrane. The immunoreactive protein was undetectable in (non)gonadal somatic cells tested. The protein had a molecular mass of 45-55 kDa and was biosynthesized by round spermatids. The acrosome-specific localization of immunoreactive RCP was unchanged during capacitation, but it was substantially lost during acrosome reaction. Functional studies indicated that treatment of spermatozoa with anti-RCP antibodies did not have any effect on either capacitation or acrosome reaction, but markedly reduced the rate of sperm penetration into zona-free hamster oocytes. These results show the existence of male germ cell-specific immunoreactive RCP, having a potential role in sperm-egg interaction in hamsters. Also the pattern of immunoreactive-RCP localization makes it an ideal marker to monitor development of acrosome in mammalian spermatozoa.

Detection and bioimaging of nitric oxide in bovine oocytes and sperm cells

Mammalian gametes contain constitutive nitric oxide synthases (NOS) to synthesize nitric oxide (NO). The detection and bioimaging of NO in bovine gametes is important to determine the regulatory roles of NO during the different events of fertilization. Diaminofluoresceins, new fluorescence indicators for NO, were applied to detect the release of NO from bovine gametes. These compounds yield green fluorescent triazolofluoresceins, which provide the advantages of high specificity, sensitivity, and simplicity for the detection of NO. In this study, we mapped the expression of NOS in the bovine sperm and ova. NOS activity in sperm first appeared in the acrosome, then 60 min later in the head, middle piece, cytoplasmic droplet, and tail. Cow ova had high NO activity in the cytoplasm and in the surrounding corona cells, but not in the zona pellucida. These results show that for bovine gametes, the synthesis NO by the NOS system presents clear patterns of time and spatial distribution that may be important for the different events of fertilization.

Porcine spermatozoa contain more than one membrane progesterone receptor

Progesterone has been shown to be a physiologically relevant inducer of the sperm acrosome reaction. A novel protein intrinsic to microsomal membranes, membrane progesterone receptor (mPR, now termed progesterone membrane receptor component 1, PGMRC1) that binds progesterone with high affinity has been cloned from porcine liver previously, and corresponding antibodies mitigate the progesterone induced acrosome reaction. In this study we aimed at the localization of mPR in porcine spermatozoa. Immunostaining suggested the exclusive occurrence of mPR in a hardly accessible place, possibly the inner acrosomal membrane, with digitonin dramatically increasing the number of positively stained cells. Consistent with the structure prediction for mPR, its short N-terminus (NT) but not the large C-terminal part becomes accessible from outside after digitonin treatment as evidenced by the staining pattern of antibodies directed against different regions of the protein. However, digitonin treatment solubilizes a progesterone binding activity of approximately 140 kDa molecular weight, that is different from mPR, which remains in the cell membrane as demonstrated by Western blotting. Ligand binding studies confirm the dissimilarity of mPR and the digitonin-soluble progesterone binding protein. Chemical modification studies also indicate that the digitonin-soluble progesterone binding protein has a binding site that differs from that of mPR. It is concluded that more than one progesterone receptor is present in porcine spermatozoa.

[Proacrosin, an acrosomal marker for the detection of spermatogenic cells in ejaculates from azoospermic men]

Between January 2003 and April 2004, a prospective study was performed on ejaculates from non-obstructive azoospermic men (n = 95), for the identification of spermatogenic cells using an immunohistochemical labeling for proacrosin. 48.4% of ejaculates (46/95) displayed labeled spermatogenic cells. A 38/95 (40%) of men had testicular sperm extraction (TESE) followed by intracytoplasmic sperm injection (i.c.s.i.). Testicular spermatozoa were extracted from 21 men (52.5%). The sensitivity of detecting spermatogenic cells is 66.7% in predicting the presence of testicular spermatozoa, and its specificity is 76.5%. Compared to histopathological diagnostic testicular biopsy, the detection of spermatogenic cells using proacrosin immunohistochemical method offers a predictive parameter for successful TESE. The immunohistochemical method for proacrosin has the advantages of simplicity and low cost. It could be used to predict spermatogenesis from non-obstructive azoospermic men. Further evaluation is required with extensive results to improve sensitivity and specificity.

Characterisation of an epitope shared by an acrosomal acrosin-like protein and the surface of tammar wallaby (Macropus eugenii) spermatozoa

Monoclonal antibodies (mAb) have been raised against marsupial sperm proteins to provide insights into the molecular nature of marsupial spermatozoa, and the proteins that mediate sperm maturation and interaction with the oocyte. This study reports the production of a mAb, designated WSA-1, which bound acrosomal and surface determinants on tammar wallaby spermatozoa. The acrosomal antigen was first detected in the wallaby testis; however, ejaculated spermatozoa demonstrated whole cell WSA-1 immunoreactivity as a result of binding an epididymal protein. Ultrastructural and agglutination analyses localised the WSA-1 epitope to the acrosomal matrix and the whole sperm plasmalemma. The WSA-1 mAb bound three polypeptides with relative molecular weights of 35, 31 and 15 kDa on western blots under reducing conditions. The N-terminal amino acid sequence obtained for the 35 kDa wallaby sperm polypeptide demonstrated identity with the eutherian acrosomal protein acrosin. The 31 kDa polypeptide was of epididymal origin and will be the subject of a separate study. Further studies of the WSA-1 antigens are likely to provide useful insights into the function and maturation of marsupial sperm since proacrosin has a number of putative roles in eutherian fertilisation, and epididymal proteins are thought to mediate sperm maturation and storage.

The protein encoded by cancer/testis gene D40/AF15q14 is localized in spermatocytes, acrosomes of spermatids and ejaculated spermatozoa

We have previously identified and cloned a human gene, D40, that is preferentially expressed in testis among normal organs, while it is widely expressed in various human tumor cell lines and primary tumors derived from different organs. In this report, we have examined the expression and localization of this protein in human testis with an antibody specific to D40 protein. In Western analyses, the anti-D40 antibody recognized a major band with a molecular mass of 300 kDa and a minor band of 250 kDa. These bands were not observed in the testis lysates from patients with Sertoli-cell-only syndrome and with Kleinfelter syndrome, who lack germ cells of the testis, indicating that D40 protein is expressed in the germ cells of normal testis. Immunohistochemical studies have revealed that D40 protein is highly expressed in spermatocytes and in the pre-acrosome of round spermatids. In the acrosome, D40 protein expression is observed not inside but outside the acrosome membrane. This is consistent with the finding that the amino-acid sequence at the amino terminal of the D40 protein lacks a hydrophobic signal peptide that is required for proteins to translocate to the membrane. Expression of D40 protein is observed in the acrosome of ejaculated spermatozoa as well, although the level is low compared with that in the pre-acrosome of spermatids. These results suggest that D40 protein plays important roles in spermatogenesis, especially in the formation and maintenance of the acrosome.

Protein detection in spermatids and spermatozoa of the butterfly Euptoieta hegesia (Lepidoptera)

This study was undertaken to detect protein components in both sperm types of the butterfly Euptoieta hegesia. These spermatozoa possess complex extracellular structures for which the composition and functional significance are still unclear. In the apyrene sperm head, the proteic cap presented an external ring and an internal dense content; basic proteins were detected only in external portions. In the tail, the paracrystalline core of mitochondrial derivatives and the axoneme are rich in proteins. The extratesticular spermatozoa are covered by a proteic coat, which presented two distinct layers. In eupyrene spermatozoa, acrosome and nucleus were negatively stained, probably because of their high compaction. In the tail, there is no paracrystalline core and the axoneme presented a very specific reaction for basic proteins. The lacinate and reticular appendages are composed of cylindrical sub-units and presented a light reaction to E-PTA and a strong reaction to tannic acid. A complex proteic coat also covers the extratesticular spermatozoa. We found similarities between both extratesticular coats, indicating a possible common origin. Both spermatozoon types are rich in proteins, especially the eupyrene appendages and the extratesticular coats. We believe that both coats are related to the sperm maturation and capacitation processes.

alpha-SNAP and NSF are required in a priming step during the human sperm acrosome reaction

The acrosome is a membrane-limited granule that overlies the nucleus of the mature spermatozoon. In response to physiological or pharmacological stimuli it undergoes a special type of Ca2+-dependent exocytosis termed the acrosome reaction (AR), which is an absolute prerequisite for fertilization. Aided by a streptolysin-O permeabilization protocol developed in our laboratory, we have previously demonstrated requirements for Rab3A, N-ethylmaleimide-sensitive factor (NSF), several soluble NSF-attachment protein receptor (SNARE) proteins, and synaptotagmin VI in the human sperm AR. Here, we show that alpha-soluble NSF-attachment protein (alpha-SNAP), a protein essential for most fusion events through its interaction with NSF and the SNARE complex, exhibits a direct role in the AR. First, the presence of alpha-SNAP is demonstrated by the Western blot of human sperm protein extracts. Immunostaining experiments reveal an acrosomal localization for this protein. Second, the Ca2+ and Rab3A-triggered ARs are inhibited by anti-alpha-SNAP antibodies. Third, bacterially expressed alpha-SNAP abolishes exocytosis in a fashion that depends on its interaction with NSF. Fourth, we show a requirement for alpha-SNAP/NSF in a prefusion step early in the exocytotic pathway, after the tethering of the acrosome to the plasma membrane and before the efflux of intra-acrosomal Ca2+. These results suggest a key role for alpha-SNAP/NSF in the AR, and strengthen our understanding of the molecular players involved in the vesicle-to-plasma membrane fusion taking place during exocytosis.

Acrosomal Actin: Twists and Turns of a Versatile Filament

A new electron cryomicroscopic reconstruction of an actin-scruin bundle from Limulus sperm reveals details about the enormous structural plasticity within F-actin. The twist and tilt of the actin subunits show very large deviations from ideal F-actin, providing clues about actin dynamics.

Structure of the acrosomal bundle

In the unactivated Limulus sperm, a 60- micro m-long bundle of actin filaments crosslinked by the protein scruin is bent and twisted into a coil around the base of the nucleus. At fertilization, the bundle uncoils and fully extends in five seconds to support a finger of membrane known as the acrosomal process. This biological spring is powered by stored elastic energy and does not require the action of motor proteins or actin polymerization. In a 9.5-A electron cryomicroscopic structure of the extended bundle, we show that twist, tilt and rotation of actin-scruin subunits deviate widely from a 'standard' F-actin filament. This variability in structural organization allows filaments to pack into a highly ordered and rigid bundle in the extended state and suggests a mechanism for storing and releasing energy between coiled and extended states without disassembly.

[Significance of determination of intra-acrosomal proteins and sperm antibodies in human reproduction]

OBJECTIVE

Comparison of the positive intra-acrosomal proteins and spermagglutinating antibodies in human semen samples from various groups of patients.

DESIGN

Prospective study.

SETTING

Department of Gynecology and Obstetrics and Faculty Hospital, Charles University, Pilsen, Institute of Molecular Genetics, Czech Academy of Science, Prague.

METHODS

Monoclonal antibodies Hs-8 and Hs-14 (prepared in the Institute of Molecular Genetics, Prague) were used for detection of intra-acrosomal sperm proteins. Microscopic immunofluorescent methods detected the incidence, the character and the percentage of the spermatozoa specified by above-mentioned monoclonal antibodies. Direct mixed anti-immunoglobulin reactions test (MAR-test) for IgG, IgM, IgA, IgE was used for detection of spermagglutinating antibody. We examined 315 infertile patients from Special Consultation for Immunology of Reproduction and from the IVF programme, and sperm healthy donors (January 2002-March 2003).

RESULTS

Native donor's sperm cells had excellent positive intra-acrosomal proteins stained with monoclonal antibodies Hs8 and Hs14 and after thawing as well as. No spermagglutinating antibodies were found. In the group with normal sperm count and light microscopic morphology we found the presence of seminal spermagglutinating antibodies in 11% (IgG), in 14.5% (IgA), in 3.6% (IgM), in 5.2% (IgE). Significant positivity of intra-acrosomal protein stained with Hs8 monoclonal antibody was reached in 68.4%, and with Hs14 monoclonal antibody in even 81.3% of men. On the other hand, in oligoasthenospermatic patients we found significant increasing of spermagglutinating antibodies (for IgG 40.5%, for IgA 28.6%, for IgM 9.5%, for IgE 11.9%). Dominant good staining of intra-acrosomal proteins were seen only in 15.5% of men (for Hs8) and in 20.2% (for Hs14).

CONCLUSION

The quantitative detection of intra-acrosomal sperm proteins and spermagglutinating antibodies are used as important properties of human semen and serve for evaluation of acrosomal state, and male fertility together.

Bending Stiffness of a Crystalline Actin Bundle

The acrosomal process of the sperm of the horseshoe crab (Limulus polyphemus) is a unique crystalline actin bundle, consisting of multiple actin filaments cross-linked by the actin-bundling protein, scruin. For successful fertilization, the acrosomal bundle must penetrate through a 30 microm thick jelly coat surrounding the egg and thus it must be sufficiently stiff. Here, we present two measurements of the bending stiffness of a single crystalline bundle of actin. Results from these measurements indicate that the actin:scruin composite bundle has an average elastic modulus of 2 GPa, which is similar to that of a single actin filament, and a bending stiffness that is more than two orders of magnitude larger than that of a bundle of uncross-linked actin filaments due to stiffening by the scruin matrix.

SPRASA, a novel sperm protein involved in immune-mediated infertility

BACKGROUND

Antisperm antibodies (ASA) may be an important cause of infertility, but current tests for the detection of ASA have poor prognostic value. Identification of the sperm proteins that ASA bind to may aid the development of more useful diagnostic tests.

METHODS

One- and two-dimensional PAGE and western blotting analyses, as well as amino acid sequencing, were used to identify a novel sperm protein reactive with ASA (SPRASA) from infertile men. An antiserum reactive with SPRASA was produced by immunizing a rabbit with SPRASA excised from two-dimensional gels. This antiserum was used to demonstrate the localization of SPRASA on the sperm.

RESULTS

Amino acid sequences derived from SPRASA matched those of a theoretical protein, XP-085564. This protein is derived from the C-type lysozyme/alpha-lactalbumin gene family. Immunohisto chemistry indicates that SPRASA is localized to the acrosome. Western blot analysis revealed that 50 unselected individuals did not have antibodies that reacted with SPRASA.

CONCLUSION

Only ASA from infertile men react with SPRASA, suggesting that this novel protein may be important in the processes of fertility. The identification of SPRASA as the antigen for infertility-associated ASA raises the possibility of developing first, antigen-specific tests for ASA, and secondly, more targeted treatment for immune-mediated infertility.

Haprin, a novel haploid germ cell-specific RING finger protein involved in the acrosome reaction

The acrosome reaction (i.e. the exocytosis of the sperm vesicle) is a prerequisite for fertilization, but its molecular mechanism is largely unknown. We have identified a cDNA clone for a gene named haprin, which encodes a haploid germ cell-specific RING finger protein. This protein is a novel member of the RBCC (RING finger, B-box type zinc finger, and coiled-coil domain) motif family that has roles in several cellular processes, such as exocytosis. It is transcribed exclusively in testicular germ cells after meiotic division. Western blot and immunohistochemical analyses showed the molecular weight of Haprin protein to be Mr approximately 82,000. It was localized in the acrosomal region of elongated spermatids and mature sperm and was not present in acrosome-reacted sperm. The specific antibody against the RING finger domain of Haprin inhibited the acrosome reaction in permeabilized sperm. These results indicated that the novel RBCC protein Haprin plays a key role in the acrosome reaction and fertilization.

Kinks, rings, and rackets in filamentous structures

Carbon nanotubes and biological filaments each spontaneously assemble into kinked helices, rings, and "tennis racket" shapes due to competition between elastic and interfacial effects. We show that the slender geometry is a more important determinant of the morphology than any molecular details. Our mesoscopic continuum theory is capable of quantifying observations of these structures and is suggestive of their occurrence in other filamentous assemblies as well.

Lysosome and lysosome-related organelles responsible for specialized functions in higher organisms, with special emphasis on vacuolar-type proton ATPase

Mammals contain various cells differentiated in both morphology and function, which play vital roles in tissue-specific functions. Late endosome/lysosome and lysosomal-related organelles are involved in these specialized functions including antigen presentation, bone remodeling and hormone regulation. To fulfill these diverse roles, lysosomes are present at different levels in different tissues and cell types; however, their morphology within these different tissues varies and the regulation of their activities differs with lysosomal compartments in some cells also functioning as secretory compartments. The luminal acidification of these organelles is closely correlated with their functions. This review will discuss the functions of lysosomes and lysosomal-related organelles, with particular emphasis on the major proton pump, the vacuolar-type proton ATPase (V-ATPase), which is responsible for luminal acidification.

The role of F-actin cytoskeleton-associated gelsolin in the guinea pig capacitation and acrosome reaction

The acrosomal reaction (AR) is a regulated sperm exocytotic process that involves fusion of the plasma membrane (PM) with the outer acrosomal membrane (OAM). Our group has described F-actin cytoskeletons associated to these membranes. It has been proposed that in regulated exocytosis, a cortical cytoskeleton acts as a barrier that obstructs membrane fusion, and must be disassembled for exocytosis to occur. Actin-severing proteins from the gelsolin family have been considered to break this barrier. The present study attempted to determine if gelsolin has a function in guinea pig sperm capacitation and AR. By indirect immunofluorescence (IIF), gelsolin was detected in the apical and postacrosomal regions of the head and in the flagellum in both capacitated and non-capacitated guinea pig spermatozoa. By Western blotting, gelsolin was detected in isolated PM and OAM of non-capacitated spermatozoa. Gelsolin and actin were detected in a mixture of PM-OAM obtained by sonication, and both proteins were absent in membranes of capacitated spermatozoa. Inhibition of three different pathways of PIP2 hydrolysis during capacitation did not cancel gelsolin loss from membranes. Gelsolin was detected by Western blotting associated to membrane cytoskeletons obtained after phalloidin F-actin stabilization and Triton-X treatment; additionally, by immunoprecipitation, it was shown that gelsolin is associated with actin. By electron microscopy we observed that skeletons disassemble during capacitation, but phalloidin prevents disassembly. A three-dimensional skeleton was observed that apparently joins PM with OAM. Exogenous gelsolin stimulates AR assayed in a permeabilized spermatozoa model. Results suggest that gelsolin disassembles F-actin cytoskeletons during capacitation, promoting AR.

SLLP1, a unique, intra-acrosomal, non-bacteriolytic, c lysozyme-like protein of human spermatozoa

We report the presence of a unique, non-bacteriolytic, c (chicken or conventional type) lysozyme-like protein, SLLP1, in the acrosome of human sperm. C lysozymes are bacteriolytic and can also bind to N-acetylglucosamines linked by beta-1,4 glycosidic bonds. Most of the invariant residues (17 out of 20), including all the cysteines, were conserved in SLLP1, but the two catalytic residues E35 and D52 of c lysozymes were replaced with T and N, respectively. The full-length cDNA encodes a protein of 215 aa with a predicted protease cleavage site between A87 and K88. The processed form of SLLP1, which showed an exon-intron organization similar to human c lysozyme, was the major isoform in the acrosome of ejaculated sperm. As expected, based on its sequence, the mature protein secreted from yeast showed no bacteriolytic activity. A significant decrease (54%, P < or = 0.001) in the number of sperm bound to zona-free hamster eggs was observed in the presence of antisera to recombinant SLLP1. SLLP1 mRNA (size, approximately 1 kb) appeared to be expressed only in the testis and in the Burkitt lymphoma Raji cell line. The gene SPACA3 encodes SLLP1 and contains five exons at locus 17q11.2. Because of its typical c lysozyme-like sequence, genomic organization, conservation of putative substrate-binding sites even in the absence of catalytic residues, and localization in the acrosomal matrix, we hypothesize that, after acrosome reaction, SLLP1 could be a potential receptor for the egg oligosaccharide residue N-acetylglucosamine, which is present in the extracellular matrix over the egg plasma membrane, within the perivitelline space, pores of zona pellucida, and cumulus layers.

Tissue kallikrein and bradykinin B2 receptors in the reproductive tract of the male rat

The setting of a local tissue kallikrein kinin system (tKKS) within the reproductive organs of the male rat was investigated by analysing bradykinin subtype 2 receptor (B2R) gene expression and cellular distribution of B2R protein and the kinin-liberating protease tissue kallikrein (tK). Reverse transcription-polymerase chain reaction showed B2R expression in testis, epididymis and prostate from prepubertal and sexually mature rats. In mature testis, in situ hybridization and immunohistochemistry localized B2R mRNA and protein besides endothelial cells of blood vessels exclusively on pachytene spermatocytes and round and elongated spermatids. B2R expression within the seminiferous tubules was found to be dependent on the stage of the spermatogenic cycle. In pre-pubertal rat testis, B2R mRNA and protein were additionally located in peritubular cells. In the testis, specific staining for tK occurred in addition to endothelial cells of blood vessels on the acrosomal cap of round and elongated spermatids. This immunostaining was also stage-dependent. In the epididymis, tK was detected on epithelial cells near the apical surface. The stage-dependent specific expression of tK and bradykinin B2Rs in developing germ cells and peritubular cells suggests a potential role of the tKKS in the local regulation of spermatogenesis and seminiferous tubule function.

Tracing sperm acrosome differentiation in the testis and maturation in the epididymis of the tammar wallaby (Macropus eugenii) with a 45-kDa acrosome-membrane-associated protein

A 45-kDa protein was originally extracted from a depression, where the acrosome is lodged, on the anterior end of the sperm nucleus of ejaculated wallaby spermatozoa. Using immunofluorescent and confocal microscopes, this study demonstrates that the 45-kDa protein is persistently localized to the sperm acrosome throughout the periods of spermiogenesis, spermiation, epididymal maturation and ejaculation in the tammar wallaby. The distribution of the 45-kDa protein is always on the perimeter of the acrosome and associated with the acrosomal membrane, so that changes in the shape of the 45-kDa immunofluorescent labelling mirror changes in the shape of the acrosome during its differentiation in the testis and epididymis. Thus, the 45-kDa protein may be used as a molecular marker to study the marsupial acrosome differentiation and to chart the events of testicular and epididymal maturation of the spermatozoa. Furthermore, the behaviour of the 45-kDa protein during the immunostaining process suggests that this protein is a largely insoluble and detergent-resistant protein and may play an important role in attachment of the acrosome to the nucleus during sperm formation, similar to those inner acrosomal-membrane-associated proteins that have been reported in eutherian spermatozoa.

A human sex hormone-binding globulin isoform accumulates in the acrosome during spermatogenesis

Human sex hormone-binding globulin (SHBG) binds estradiol and testosterone with high affinity. Plasma SHBG is produced by hepatocytes, but the human SHBG gene is also expressed in the testis. Little is known about SHBG gene expression in the human testis, but human SHBG transcripts accumulate in a spermatogenic stage-dependent manner in the testes of mice containing an 11-kb human SHBG transgene. We have now found that human SHBG transcripts containing an alternative exon 1 sequence are located specifically in the testicular germ cells of these transgenic mice, whereas murine SHBG transcripts are confined to Sertoli cells. In addition, we have detected immunoreactive human SHBG in the acrosome during all stages of spermiogenesis in mice containing an 11-kb human SHBG transgene. Western blots of germ cell extracts from these transgenic mice and from human sperm indicate that the immunoreactive human SHBG in the acrosome composes electrophoretic variants, which are 3-5 kDa smaller than the major electrophoretic isoforms of human SHBG in the blood. This apparent size difference is due in part to differences in glycosylation of plasma and acrosomal SHBG isoforms. The function of the human SHBG isoform in the acrosome is unknown, but it binds steroid ligands with high affinity. This is the first demonstration that human SHBG transcripts encode an SHBG isoform that remains within a cellular compartment.

Progesterone Receptor as an Indicator of Sperm Function

Expression of progesterone receptor (PR) localization on spermatozoa was determined in men with normal and abnormal spermiograms. Studies were also carried out to evaluate the potential of PR as a marker of sperm function. Progesterone receptor expression on spermatozoa from men with normozoospermia (n = 8), oligozoospermia (n = 7), asthenozoospermia (n = 8), oligoasthenozoospermia (n = 7), and teratozoospermia (n = 11) was analyzed using an immunocytochemical method with monoclonal antibodies against PR, and flow cytometry using a cell-impermeable fluorescein-tagged progesterone coupled to BSA complex (P-FITC-BSA). Both methods revealed significantly fewer (P < 0.05) PR-positive spermatozoa in men with oligozoospermia, asthenozoospermia, oligoasthenozoospermia, and teratozoospermia compared with men with normozoospermia, thereby suggesting that down-regulation of PR expression in spermatozoa may be one of the causes of male infertility. Spermatozoa from men with normozoospermia (n = 12), oligozoospermia (n = 12), asthenozoospermia (n = 12), oligoasthenozoospermia (n = 9), and teratozoospermia (n = 10) were exposed to low osmotic conditions in the hypoosmotic swelling (HOS) test and then analyzed for PR expression using P-FITC-BSA complex. A significantly higher percentage (P < 0.05) of spermatozoa with physiologically active plasma membrane (HOS+) lacked PR expression (HOS+PR-) in all categories of men with infertility, thereby suggesting that compared to the HOS test, PR expression is a better indicator of sperm function. Furthermore, PR expression in spermatozoa showed a strong (P < 0.05) positive correlation with their ability to undergo an in vitro acrosome reaction. This was observed in all study groups (i.e., normozoospermia, r = 0.8545; oligozoospermia, r = 0.8711; asthenozoospermia, r = 0.7645; oligoasthenozoospermia, r = 0.9003; and teratozoospermia, r = 0.8676). This suggests a potential role for PR in the events leading to the acrosome reaction in sperm.

Comparative ultracytochemical study of the acrosome in four different Veneroida species from the Turkish coast

Cytoplasmic acidic phosphoproteins and complex polysaccharides were stained with ammoniacal silver nitrate-formalin and phosphotungstic acid-chromic acid, respectively. In Cerastoderma glaucum (Cardiacea), acrosomal vesicle contents are differentiated into an apical intermediate-dense component and a basal dense region. PTA stained the apical component and silver stained the basal region and the apex of the acrosome. In Spisula subtruncata (Mactracea) the acrosome showed a PTA-stained apical component and a silver-positive basal dense region. In the Veneracea, Chamelea gallina and Pitar rudis show a tripartite acrosomal vesicle, with apical light, outer dense and inner intermediate-dense regions. In both species, the apical and inner components were stained by PTA, whereas silver stained all regions of the acrosomal vesicle in C. gallina and the apical and outer regions in P. rudis. In midpiece, only C. glaucum showed a positive silver reaction at the centriolar fossa.

Identification of amplified restriction fragment length polymorphism markers linked to genes controlling boar sperm viability following cryopreservation

This study investigated two hypotheses: 1) that consistent between-boar variation in frozen semen quality exists and is genetically determined, and 2) molecular markers linked to genes controlling semen freezability can be identified using amplified restriction fragment length polymorphism (AFLP) technology. Five ejaculates were collected from each of 129 boars. Semen was diluted into a commercial freezing buffer (700 mOsm/kg, 3% glycerol) and five straws (0.5 ml) per ejaculate were cryopreserved (to -5 degrees C at 6 degrees C/min, then -5 degrees C to -80 degrees C at 40 degrees C/min). Semen was assessed for percentage of motile cells, motility characteristics (computer-aided semen analysis; CASA), plasma membrane integrity (SYBR-14 positive), and acrosome integrity (positive for fluorescein-labeled peanut agglutinin; PNA). Consistent between-boar variability was detected for postthaw sperm motility (P < 0.01), membrane integrity (P < 0.01), acrosome integrity (P < 0.01), and all CASA characteristics (P < 0.05). There was no significant difference between ejaculates (P > 0.05) or straws (P > 0.05) for any viability assessment. Multivariate pattern analysis of the viability data set highlighted three groups of boars producing spermatozoa with poor, average, and good postthaw recovery (42, 63, and 24 boars, respectively). DNA from Large White boars (n = 22) previously classified as good and poor freezers was screened for AFLP markers. Twenty-eight polymerase chain reaction primer combinations generated 2182 restriction fragment bands, of which 421 were polymorphic. Sixteen candidate genetic markers (P < 0.005) were identified by comparing the AFLP profile with semen freezability using logistic regression analysis. These findings support the hypothesis that there is a genetic basis for variation in postthaw semen quality between individuals, and that AFLP technology may be able to identify molecular markers linked to genes influencing this variation.

Isolation of the peri-acrosomal plasma membrane protein D40 enriched fraction from guinea pig spermatozoa using a monoclonal antibody

Membrane fragments were obtained from guinea pig spermatozoa by mechanical shearing. A membrane-enriched fraction was separated from other cellular debris, mainly sperm nuclei and tails, by centrifugation on 20% Ficoll 70 solution. Peri-acrosomal plasma membrane protein, D40, enriched fraction was separated from this membrane preparation using a mouse monoclonal antibody to D40 attached to magnetic beads. Enrichment of D40 antigen in this fraction was demonstrated by western blotting. The method provides a preparative route to a membrane, the constituents of which play an important role in sperm recognition of the zona pellucida and the acrosome reaction. Some constituents of the peri-acrosomal plasma membrane over the equatorial segment of the acrosome may also play a role in sperm docking with the oocyte plasma membrane and fusion of the two cells.

Lanosterol 14alpha-demethylase and MAS sterols in mammalian gametogenesis

The lanosterol 14alpha-demethylase protein complex is composed of a cytochrome P450 enzyme CYP51 and its redox partner NADPH cytochrome P450 reductase. The complex participates in cholesterol biosynthesis and produces folicular fluid meiosis activating sterol (FF-MAS) from lanosterol. FF-MAS is metabolized further by sterol Delta14-reductase to testis-meiosis activating sterol (T-MAS). Additional enzymatic steps are needed before cholesterol is produced. Using the anti-human CYP51 antibody we have studied CYP51 protein expression by confocal microscopy in male and female mouse gonads. Leydig cells and acrosomes of spermatids express the highest levels of the CYP51 protein. CYP51 protein is also detected in primary mouse oocytes of non-treated mice and in some granulosa cells. While regulatory mechanisms responsible for FF-MAS accumulation in the ovary are not yet established, two mechanisms contributing to production the of T-MAS in the testis have been found. Potential in vivo roles of FF-MAS and T-MAS in fertilization are discussed.