Cd52, known as a major maturation-associated sperm membrane antigen secreted from the epididymis, is not required for fertilization in the mouse

Evolution of a New Testis-Specific Functional Promoter Within the Highly Conserved Map2k7 Gene of the Mouse

Map2k7 (synonym Mkk7) is a conserved regulatory kinase gene and a central component of the JNK signaling cascade with key functions during cellular differentiation. It shows complex transcription patterns, and different transcript isoforms are known in the mouse (Mus musculus). We have previously identified a newly evolved testis-specific transcript for the Map2k7 gene in the subspecies M. m. domesticus. Here, we identify the new promoter that drives this transcript and find that it codes for an open reading frame (ORF) of 50 amino acids. The new promoter was gained in the stem lineage of closely related mouse species but was secondarily lost in the subspecies M. m. musculus and M. m. castaneus. A single mutation can be correlated with its transcriptional activity in M. m. domesticus, and cell culture assays demonstrate the capability of this mutation to drive expression. A mouse knockout line in which the promoter region of the new transcript is deleted reveals a functional contribution of the newly evolved promoter to sperm motility and the spermatid transcriptome. Our data show that a new functional transcript (and possibly protein) can evolve within an otherwise highly conserved gene, supporting the notion of regulatory changes contributing to the emergence of evolutionary novelties.

Stromal androgen and hedgehog signaling regulates stem cell niches in pubertal prostate development

Stromal androgen-receptor (AR) action is essential for prostate development, morphogenesis and regeneration. However, mechanisms underlying how stromal AR maintains the cell niche in support of pubertal prostatic epithelial growth are unknown. Here, using advanced mouse genetic tools, we demonstrate that selective deletion of stromal AR expression in prepubescent Shh-responsive Gli1-expressing cells significantly impedes pubertal prostate epithelial growth and development. Single-cell transcriptomic analyses showed that AR loss in these prepubescent Gli1-expressing cells dysregulates androgen signaling-initiated stromal-epithelial paracrine interactions, leading to growth retardation of pubertal prostate epithelia and significant development defects. Specifically, AR loss elevates Shh-signaling activation in both prostatic stromal and adjacent epithelial cells, directly inhibiting prostatic epithelial growth. Single-cell trajectory analyses further identified aberrant differentiation fates of prostatic epithelial cells directly altered by stromal AR deletion. In vivo recombination of AR-deficient stromal Gli1-lineage cells with wild-type prostatic epithelial cells failed to develop normal prostatic epithelia. These data demonstrate previously unidentified mechanisms underlying how stromal AR-signaling facilitates Shh-mediated cell niches in pubertal prostatic epithelial growth and development.

The conserved fertility factor SPACA4/Bouncer has divergent modes of action in vertebrate fertilization

Fertilization is the fundamental process that initiates the development of a new individual in all sexually reproducing species. Despite its importance, our understanding of the molecular players that govern mammalian sperm-egg interaction is incomplete, partly because many of the essential factors found in nonmammalian species do not have obvious mammalian homologs. We have recently identified the lymphocyte antigen-6 (Ly6)/urokinase-type plasminogen activator receptor (uPAR) protein Bouncer as an essential fertilization factor in zebrafish [S. Herberg, K. R. Gert, A. Schleiffer, A. Pauli, Science 361, 1029-1033 (2018)]. Here, we show that Bouncer's homolog in mammals, Sperm Acrosome Associated 4 (SPACA4), is also required for efficient fertilization in mice. In contrast to fish, in which Bouncer is expressed specifically in the egg, SPACA4 is expressed exclusively in the sperm. Male knockout mice are severely subfertile, and sperm lacking SPACA4 fail to fertilize wild-type eggs in vitro. Interestingly, removal of the zona pellucida rescues the fertilization defect of Spaca4-deficient sperm in vitro, indicating that SPACA4 is not required for the interaction of sperm and the oolemma but rather of sperm and the zona pellucida. Our work identifies SPACA4 as an important sperm protein necessary for zona pellucida penetration during mammalian fertilization.

Mouse CD52 is predominantly expressed in the cauda epididymis, regulated by androgen and lumicrine factors

Background:

Sperm maturation takes place through contact between sperm and proteins produced in the epididymal lumen. CD52 had been characterised in the sperm; however, the expression and its regulation in the epididymis are mostly unknown.

Aim:

This study aimed to analyse the expression and regulation of CD52 in the mouse epididymis.

Setting and Design:

Experimental design was used in this study.

Materials and Methods:

Epididymis tissues from mice strain Deutch Democratic Yokohama were used as sources of total RNA. Bioinformatic tool was used to predict signal peptides. Quantitative real-time reverse transcription–polymerase chain reaction was used to analyse tissue distribution, androgen, testicular factors dependency and postnatal development.

Statistical Analysis:

One-way analysis of variance was used to analyse differences between treatment and control untreated group. P < 0.05 was determined as a significant difference.

Results:

CD52 amino acid sequence contains a signal peptide, indicating it is a secretory protein. CD52 exhibited region-specific expression in the epididymis, with the highest level being in the cauda. CD52 expression was regulated by androgen indicated by a significant downregulation at day 1 and day 3 following a castration (P < 0.05). Dependency on androgen was confirmed by injection of exogenous testosterone which prevented downregulation by 50%. Moreover, lumicrine factors also influenced CD52 expression indicated by ligation of efferent duct which also reduced expression at day 1 to day 5 following the ligation (P < 0.05). CD52 expression was developmentally regulated. This was shown by increase in the level of expression starting at day 15 postnatally.

Conclusion:

CD52 shows characteristics of genes involved in sperm maturation in the epididymis.

CRISPR-Cas9-mediated mutation revealed BSPH2 protein is dispensable for male fertility

Members of the Binder of SPerm (BSP) superfamily have been identified in both human and mouse epididymis. These proteins are known to bind sperm membrane and promote sperm capacitation. Studies suggest that BSPH2 might play a different role in sperm functions from its counterparts; however, the role of BSPH2 remains mainly unexplored. To investigate whether the absence of one member of the BSP family could affect fertility, mice lacking Bsph2 expression were generated using clustered regularly interspaced short palindromic repeats (CRISPR) associated 9 (Cas9) technology. Knockout (KO) male mice were mated with wild-type (WT) females, and the number and weight of the pups were determined. Sperm motility in WT and KO was assessed using sperm class analyzer (SCA). Liquid chromatography tandem mass spectrometry (LC-MS/MS) was used for protein identification. Fertility analysis of null Bsph2 mice did not reveal any phenotype. No differences were noticed on average litter size or average pup weight. Normal testis weight and morphology were observed in Bsph2^+/- and Bsph2^-/- compared to the WT. Quantitative polymerase chain reaction analyses revealed that Bsph1 messenger RNA expression was increased in mutant mice, whereas LC-MS/MS analysis displayed no increase in protein expression level. Taken together, we show the existence of redundant function for murine BSPH2 and the lack of BSPH2 itself does not lead to sterility.

CD52 glycan binds the proinflammatory B box of HMGB1 to engage the Siglec-10 receptor and suppress human T cell function

Inflammation is a protective response of the body’s immune system against harmful stimuli such as pathogenic microorganisms, toxins, or damaged cells. However, if excessive or prolonged, inflammation may be harmful and therefore has to be regulated. Soluble CD52 is a natural sialoglycopeptide and immune regulator that suppresses inflammatory responses. We elucidated the mechanism of this effect by showing that soluble CD52 first sequesters a mediator of inflammation called HMGB1; in turn, this promotes binding of the sialylated CD52 glycan to an inhibitory receptor, sialic acid-binding immunoglobulin-like lectin (Siglec)-10, present on activated T cells and other immune cells. This concerted antiinflammatory mechanism driven by soluble CD52 may contribute to immune-inflammatory homeostasis and underscores the therapeutic potential of soluble CD52.

CD52, a glycophosphatidylinositol (GPI)-anchored glycoprotein, is released in a soluble form following T cell activation and binds to the Siglec (sialic acid-binding Ig-like lectin)-10 receptor on T cells to suppress their function. We show that binding of CD52-Fc to Siglec-10 and T cell suppression requires the damage-associated molecular pattern (DAMP) protein, high-mobility group box 1 (HMGB1). CD52-Fc bound specifically to the proinflammatory Box B domain of HMGB1, and this in turn promoted binding of the CD52 N-linked glycan, in α-2,3 sialic acid linkage with galactose, to Siglec-10. Suppression of T cell function was blocked by anti-HMGB1 antibody or the antiinflammatory Box A domain of HMGB1. CD52-Fc induced tyrosine phosphorylation of Siglec-10 and was recovered from T cells complexed with HMGB1 and Siglec-10 in association with SHP1 phosphatase and the T cell receptor (TCR). Thus, soluble CD52 exerts a concerted immunosuppressive effect by first sequestering HMGB1 to nullify its proinflammatory Box B, followed by binding to the inhibitory Siglec-10 receptor, triggering recruitment of SHP1 to the intracellular immunoreceptor tyrosine-based inhibitory motif of Siglec-10 and its interaction with the TCR. This mechanism may contribute to immune-inflammatory homeostasis in pathophysiologic states and underscores the potential of soluble CD52 as a therapeutic agent.

Factors controlling sperm migration through the oviduct revealed by gene-modified mouse models

Mammalian fertilization is comprised of many steps including sperm survival in the uterus, sperm migration in the female reproductive tract, physiological and morphological changes to the spermatozoa, and sperm-egg interaction in the oviduct. In vitro studies have revealed essential factors for these fertilization steps for over half a century. However, the molecular mechanism of fertilization has recently been revised by the emergence of genetically modified animals. Here, we focus on essential factors for sperm fertilizing ability and describe recent advances in our knowledge of the mechanisms of mammalian fertilization, especially of sperm migration from the uterus into the oviduct.

Human Globozoospermia-Related Gene Spata16 Is Required for Sperm Formation Revealed by CRISPR/Cas9-Mediated Mouse Models

A recent genetic analysis of infertile globozoospermic patients identified causative mutations in three genes: a protein interacting with C kinase 1 (PICK1), dpy 19-like 2 (DPY19L2), and spermatogenesis associated 16 (SPATA16). Although mouse models have clarified the physiological functions of Pick1 and Dpy19l2 during spermatogenesis, Spata16 remains to be determined. Globozoospermic patients carried a homozygous point mutation in SPATA16 at 848G→A/R283Q. We generated CRISPR/Cas9-mediated mutant mice with the same amino acid substitution in the fourth exon of Spata16 to analyze the mutation site at R284Q, which corresponded with R283Q of mutated human SPATA16. We found that the point mutation in Spata16 was not essential for male fertility; however, deletion of the fourth exon of Spata16 resulted in infertile male mice due to spermiogenic arrest but not globozoospermia. This study demonstrates that Spata16 is indispensable for male fertility in mice, as well as in humans, as revealed by CRISPR/Cas9-mediated mouse models.

Sialylation Facilitates the Maturation of Mammalian Sperm and Affects Its Survival in Female Uterus

Establishment of adequate levels of sialylation is crucial for sperm survival and function after insemination; however, the mechanism for the addition of the sperm sialome has not been identified. Here, we report evidence for several different mechanisms that contribute to the establishment of the mature sperm sialome. Directly quantifying the source of the nucleotide sugar CMP-beta-N-acetylneuraminic acid in epididymal fluid indicates that transsialylation occurs in the upper epididymis. Western blots for the low-molecular-mass sialoglycoprotein (around 20–50 kDa) in C57BL/6 mice epididymal fluid reflect that additional sialome could be obtained by glycosylphosphatidylinositol-anchored sialoglycopeptide incorporation during epididymal transit in the caput of the epididymis. Additionally, we found that in Cmah (CMP-N-acetylneuraminic acid hydroxylase)−/− transgenic mice, epididymal sperm obtained sialylated-CD52 from seminal vesicle fluid (SVF). Finally, we used Gfp (green fluorescent protein)+/+ mouse sperm to test the role of sialylation on sperm for protection from female leukocyte attack. There is very low phagocytosis of the epididymal sperm when compared to that of sperm coincubated with SVF. Treating sperm with Arthrobacter ureafaciens sialidase (AUS) increased phagocytosis even further. Our results highlight the different mechanisms of increasing sialylation, which lead to the formation of the mature sperm sialome, as well as reveal the sialome's function in sperm survival within the female genital tract.

GPI-AP release in cellular, developmental, and reproductive biology

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) contain a covalently linked GPI anchor located on outer cell membranes. GPI-APs are ubiquitously conserved from protozoa to vertebrates and are critical for physiological events such as development, immunity, and neurogenesis in vertebrates. Both membrane-anchored and soluble GPI-APs play a role in regulating their protein conformation and functional properties. Several pathways mediate the release of GPI-APs from the plasma membrane by vesiculation or cleavage. Phospholipases and putative substrate-specific GPI-AP-releasing enzymes, such as NOTUM, glycerophosphodiesterase 2, and angiotensin-converting enzyme, have been characterized in mammals. Here, the protein modifications resulting from the cleavage of the GPI anchor are discussed in the context of its physiological functions.

Evaluation of CD52 positive sperms in subfertile human semen samples: Is there any relationship with main semen parameters?

Background:

Sperm maturation and sperm membrane integration are the most important elements in male fertility. CD52 is one of the antigens. CD52 is a GPI (glycosylphosphatidylinositol) anchored that express on lymphocytes and epididymal cells. This antigen bind to sperm membrane during transition sperm from epididymal duct as well as its relationship with semenogelins in human seminal plasma. The aim of this study was to obtain any association between the percentage of CD52 positive sperms with main semen parameters such as percentage of motile sperms, percentage of sperm with normal morphology, and the presence of normal viscosity.

Materials and Methods:

Semen samples from subfertile men were analyzed, the samples totally were 45 that divided according to their motility into three groups, first one, more than 40%, second one 10-40%, and the third one under 10% total motility. Fifteen samples in each group were evaluated by semen analysis according to WHO 2010 guidelines for infertility laboratory. Sperms were washed by Ham's F-10 and immunostaining with the monoclonal antibody CAMPATH-1G and then analyzed by flow cytometry. We compared each of the groups based on their motility and the data were analyzed by SPSS 20.

Results:

Correlation between CD52 labeling and sperm motility was negatively significant, in the second group (r = –0.592, P = 0.020) and in the third group (r = –0.805, P = 0.00).

Conclusion:

Our results showed that the correlation between CD52 labeling and sperm motility was negatively significant, but we did not observe any relation with other semen parameters, such as sperm normal morphology, sperm concentration, and semen viscosity.

Immune regulation by CD52-expressing CD4 T cells

T-cell regulation by CD52-expressing CD4 T cells appears to operate by two different and possibly synergistic mechanisms. The first is by its release from the cell surface of CD4 T cells that express high levels of CD52 that then binds to the inhibitory sialic acid-binding immunoglobulin-like lectins-10 (Siglec-10) receptor to attenuate effector T-cell activation by impairing phosphorylation of T-cell receptor associated lck and zap-70. The second mechanism appears to be by crosslinkage of the CD52 molecules by an as yet unidentified endogenous ligand that is mimicked by a bivalent anti-CD52 antibody that results in their expansion.

SPACA1-deficient male mice are infertile with abnormally shaped sperm heads reminiscent of globozoospermia

SPACA1 is a membrane protein that localizes in the equatorial segment of spermatozoa in mammals and is reported to function in sperm-egg fusion. We produced a Spaca1 gene-disrupted mouse line and found that the male mice were infertile. The cause of this sterility was abnormal shaping of the sperm head reminiscent of globozoospermia in humans. Disruption of Spaca1 led to the disappearance of the nuclear plate, a dense lining of the nuclear envelope facing the inner acrosomal membrane. This coincided with the failure of acrosomal expansion during spermiogenesis and resulted in the degeneration and disappearance of the acrosome in mature spermatozoa. Thus, these findings clarify part of the cascade leading to globozoospermia.

Epididymal protein Rnase10 is required for post-testicular sperm maturation and male fertility

Eutherian spermatozoa are dependent on the environment of the proximal epididymis to complete their maturation; however, no specific epididymal factors that mediate this process have so far been identified. Here, we show that targeted disruption of the novel gene Rnase10 encoding a secreted proximal epididymal protein in the mouse results in a binding defect in spermatozoa and their inability to pass through the uterotubal junction in the female. The failure to gain the site of fertilization in the knockout spermatozoa is associated with a gradual loss of ADAM3 and ADAM6 proteins during epididymal transit. In the distal epididymis, these spermatozoa appear to lack calcium-dependent associations with the immobilizing glutinous extracellular material and are released as single, vigorously motile cells that display no tendency for head-to-head agglutination and lack affinity to the oviductal epithelium. In sperm-egg binding assay, they are unable to establish a tenacious association with the zona pellucida, yet they are capable of fertilization. Furthermore, these sperm show accelerated capacitation resulting in an overall in vitro fertilizing ability superior to that of wild-type sperm. We conclude that the physiological role of sperm adhesiveness is in the mechanism of restricted sperm entry into the oviduct rather than in sperm-egg interaction.—Krutskikh, A., Poliandri, A., Cabrera-Sharp, V., Dacheux, J. L., Poutanen, M., Huhtaniemi, I. Epididymal protein Rnase10 is required for post-testicular sperm maturation and male fertility.

Concordance of preclinical and clinical pharmacology and toxicology of therapeutic monoclonal antibodies and fusion proteins: cell surface targets

Monoclonal antibodies (mAbs) and fusion proteins directed towards cell surface targets make an important contribution to the treatment of disease. The purpose of this review was to correlate the clinical and preclinical data on the 15 currently approved mAbs and fusion proteins targeted to the cell surface. The principal sources used to gather data were: the peer reviewed Literature; European Medicines Agency 'Scientific Discussions'; and the US Food and Drug Administration 'Pharmacology/Toxicology Reviews' and package inserts (United States Prescribing Information). Data on the 15 approved biopharmaceuticals were included: abatacept; abciximab; alefacept; alemtuzumab; basiliximab; cetuximab; daclizumab; efalizumab; ipilimumab; muromonab; natalizumab; panitumumab; rituximab; tocilizumab; and trastuzumab. For statistical analysis of concordance, data from these 15 were combined with data on the approved mAbs and fusion proteins directed towards soluble targets. Good concordance with human pharmacodynamics was found for mice receiving surrogates or non-human primates (NHPs) receiving the human pharmaceutical. In contrast, there was poor concordance for human pharmacodynamics in genetically deficient mice and for human adverse effects in all three test systems. No evidence that NHPs have superior predictive value was found.

Mice expressing aberrant sperm-specific protein PMIS2 produce normal-looking but fertilization-incompetent spermatozoa

Eight kinds of gene-disrupted mice (Clgn, Calr3, Pdilt, Tpst2, Ace, Adam1a, Adam2, and Adam3) show impaired sperm transition into the oviducts and defective sperm binding to the zona pellucida. All of these knockout strains are reported to lack or show aberrant expression of a disintegrin and metallopeptidase domain 3 (ADAM3) on the sperm membrane. We performed proteomic analyses of the proteins of these infertile spermatozoa to clarify whether the abnormal function is caused exclusively by a deficiency in ADAM3 expression. Two proteins, named PMIS1 and PMIS2, were missing in spermatozoa from Clgn-disrupted mice. To study their roles, we generated two gene-disrupted mouse lines. Pmis1-knockout mice were fertile, but Pmis2-knockout males were sterile because of a failure of sperm transport into the oviducts. Pmis2-deficient spermatozoa also failed to bind to the zona pellucida. However, they showed normal fertilizing ability when eggs surrounded with cumulus cells were used for in vitro fertilization. Further analysis revealed that these spermatozoa lacked the ADAM3 protein, but the amount of PMIS2 was also severely reduced in Adam3-deficient spermatozoa. These results suggest that PMIS2 might function both as the ultimate factor regulating sperm transport into the oviducts and in modulating sperm-zona binding.

Molecular cloning and identification of mouse epididymis-specific gene mHong1, the homologue of rat HongrES1

Previous studies have shown that rat epididymis-specific gene HongrES1 plays important roles in sperm capacitation and fertility. In this study, we cloned the mouse homologue gene by sequence alignment and RT-PCR methods and designated it as mHong1. The mHong1 gene is located on chromosome 12p14, spanning five exons. The cDNA sequence consists of 1257 nucleotides and encodes a 419 amino-acid protein with a predicted N-terminal signal peptide of 20 amino acids. The mHong1 mRNA shows similarity with HongrES1 in the expression patterns: (i) specific expression in epididymal tissue, especially in the cauda region; and (ii) androgen-dependence but testicular fluid factor independence. Its protein product shows 71% similarity with HongrES1 and contains a classical serpin domain as does HongrES1. A polyclonal antibody against mHong1 with high specificity and sensitivity was raised. Like HongrES1, the mHong1 protein shows a checker-board expression pattern in the epididymal epithelium and is secreted into the epididymal lumen. The mHong1 protein shows higher glycosylation than HongrES1. Although both of them are deposited onto the sperm head surface, mHong1 is localized to the equatorial segment, which is different from that of HongrES1. The mHong1 protein can be removed from the sperm membrane by high ionic strength and therefore can be classed as an extrinsic membrane protein. Collectively, we conclude that mHong1 is the homologue of HongrES1 and the present work paves the way for establishing animal models to elucidate the precise functions of HongrES1 and mHong1.

The N-linked carbohydrate moiety of male reproductive tract CD52 (mrt-CD52) interferes with the complement system via binding to C1q

Antisperm antibody detected in infertile female patients' sera has been shown to correlate with reduced fertility. The antibody showed strong complement-dependent cytotoxicity as determined by the sperm immobilization test (SIT). CD52 is a human glycosylphosphatidylinositol (GPI)-anchored antigen present in lymphocytes and male reproductive tracts (mrt), including mature sperm and seminal plasma. Recently, purified mrt-CD52 from human seminal plasma has been reported to interfere with the classical complement pathway, but not lectin binding or alternative pathways of the complement system. The purpose of this study is to determine which stage of the classical pathway mrt-CD52 regulates. mrt-CD52 was purified from human seminal plasma or intact sperm membrane. Immunoprecipitation assay was performed with the reaction of mrt-CD52, human complement and mAb H6-3C4. Immunoprecipitate was formed by the carbohydrate moiety of mrt-CD52, but not by the GPI-anchor peptide. The C1q molecule (29 kDa) was detected in the immunoprecipitates by Western blotting analysis probed with anti C1q antibody, indicating that the carbohydrate moiety of mrt-CD52 binds to C1q. Also, the complement-dependent SIT revealed that purified CD52 inhibited sperm immobilization activity by antisperm antibody. These results suggest that mrt-CD52 protects sperm function from complement attack if antisperm antibody is generated in the female reproductive tracts.

Alemtuzumab and multiple sclerosis: therapeutic application

IMPORTANCE OF THE FIELD

The cause and cure for multiple sclerosis (MS) remain unknown. Immunomodulatory agents are only partially effective and many patients do not tolerate the side effects or fail them. Immunosuppressive agents act non-specifically and are associated with serious complications. An emerging group of biologic agents with great potential for treatment of immune-mediated disorders such as MS are monoclonal antibodies. A review of alemtuzumab in MS is presented.

AREAS COVERED IN THIS REVIEW

Mechanisms of action of alemtuzumab and the results of Phase II clinical trials in MS.

WHAT THE READER WILL GAIN

Alemtuzumab is a humanized mAb, which targets the surface molecule CD52 on all T cell populations and other cellular components of the immune system such as thymocytes, B cells, and monocytes. Alemtuzumab, which is administered intravenously, depletes T as well as B lymphocyte populations for extended periods. Adverse effects in MS patients such as thyroid disorders and idiopathic thrombocytopenic purpura are discussed.

TAKE HOME MESSAGE

Alemtuzumab may hold great promise for treatment of MS patients and serve as an option for patients refractory to immunomodulatory therapies. Due to its unique mechanism of action and profound effect on MS disease activity it enhances our knowledge about pathogenic mechanisms of MS.

Sperm equatorial segment protein 1, SPESP1, is required for fully fertile sperm in mouse

Mammalian fertilization is a multistep process that culminates in the fusion of the sperm and egg plasma membrane. It is widely accepted that the equatorial segment of the acrosome-reacted sperm is important in initiating fusion with the egg plasma membrane during fertilization. There are various proteins known to be distributed only in the equatorial segment of sperm. The role of these proteins must be clarified to understand the membrane fusion process. We produced a mouse line that lacked SPESP1 (sperm equatorial segment protein 1) and analyzed the fertilizing ability of the sperm. The average number of pups that were fathered by Spesp1(+/-) and Spesp1(-/-) males was significantly lower than that of wild-type fathers. In these mouse lines, fewer sperm were found to migrate into oviducts and fewer eggs were fertilized. The Spesp1(+/-) and Spesp1(-/-) sperm showed a lower fusing ability compared with the wild-type sperm. The disruption of Spesp1 was shown to cause an aberrant distribution of various sperm proteins. Moreover, scanning electron microscopy revealed that the membrane in the equatorial segment area, which usually forms an acrosomal sheath, disappears after acrosome reaction in Spesp1-deficient mice. It was demonstrated that SPESP1 is necessary to produce the fully 'fusion competent' sperm.

Novel epididymal proteins as targets for the development of post-testicular male contraception

Apart from condoms and vasectomy, modern contraceptive methods for men are still not available. Besides hormonal approaches to stop testicular sperm production, the post-meiotic blockage of epididymal sperm maturation carries lots of promise. Microarray and proteomics techniques and libraries of expressed sequence tags, in combination with digital differential display tools and publicly available gene expression databases, are being currently used to identify and characterize novel epididymal proteins as putative targets for male contraception. The data reported indicate that these technologies provide complementary information for the identification of novel highly expressed genes in the epididymis. Deleting the gene of interest by targeted ablation technology in mice or using immunization against the cognate protein are the two preferred methods to functionally validate the function of novel genesin vivo. In this review, we summarize the current knowledge of several epididymal proteins shown eitherin vivoorin vitroto be involved in the epididymal sperm maturation. These proteins include CRISP1, SPAG11e, DEFB126, carbonyl reductase P34H, CD52, and GPR64. In addition, we introduce novel proteinases and protease inhibitor gene families with potentially important roles in regulating the sperm maturation process. Furthermore, potential contraceptive strategies as well as delivery methods will be discussed. Despite the progress made in recent years, further studies are needed to reveal further details in the epididymal sperm maturation process and the factors involved, in order to facilitate the development of new epididymal contraceptives.