Deciphering dynamic interactions between spermatozoa and the ovarian microenvironment through integrated multi-omics approaches in viviparous Sebastes schlegelii

The ovarian microenvironment plays a crucial role in ensuring the reproductive success of viviparous teleosts. However, the molecular mechanism underlying the interaction between spermatozoa and the ovarian microenvironment has remained elusive. This study aimed to contribute to a better understanding of this process in black rockfish (Sebastes schlegelii) using integrated multi-omics approaches. The results demonstrated significant upregulation of ovarian complement-related proteins and pattern recognition receptors, along with remodeling of glycans on the surface of spermatozoa at the early spermatozoa-storage stage (1 month after mating). As spermatozoa were stored over time, ovarian complement proteins were progressively repressed by tryptophan and hippurate, indicating a remarkable adaptation of spermatozoa to the ovarian microenvironment. Before fertilization, a notable upregulation of cellular junction proteins was observed. The study revealed that spermatozoa bind to ZPB2a protein through GSTM3 and that ZPB2a promotes spermatozoa survival and movement in a GSTM3-dependent manner. These findings shed light on a key mechanism that influences the dynamics of spermatozoa in the female reproductive tract, providing valuable insights into the molecular networks regulating spermatozoa adaptation and survival in species with internal fertilization.

Update on the research on the antigens of anti-sperm antibodies over the last decade

This review summarizes the advancements over a decade of research on antigens of anti-sperm antibodies (ASAs), which are key to male immune infertility. Despite the progress in assisted reproductive technologies, understanding the roles and mechanisms of ASAs and their antigens remains vital for immune infertility management. We conducted a comprehensive literature search on PubMed from January 2013 to December 2023 using the following keywords: "anti-sperm antibody," "sperm antigen," and "immune infertility." In this review, we focus on the discoveries in sperm antigen identification and characterization through proteomics, gene disruption technology, and immunoinformatics, along with the development of fertility biomarkers. Here, we discuss the clinical applications of improved ASA detection methods and the progress in the development of immunocontraceptive vaccines. The intersection of advanced diagnostic techniques and vaccine development represents a promising frontier in reproductive health. The findings also highlight the need for standardized ASA detection methods and a comprehensive molecular-level approach to understanding ASA-related infertility. These insights underscore the significance of ongoing reproductive immunology research in enhancing clinical fertility outcomes and contraceptive vaccine development.

Insights into crucial molecules and protein channels involved in pig sperm cryopreservation

Cryopreservation is the most efficient procedure for long-term preservation of mammalian sperm; however, its use is not currently dominant for boar sperm before its use for artificial insemination. In fact, freezing and thawing have an extensive detrimental effect on sperm function and lead to impaired fertility. The present work summarises the basis of the structural and functional impact of cryopreservation on pig sperm that have been extensively studied in recent decades, as well as the molecular alterations in sperm that are related to this damage. The wide variety of mechanisms underlying the consequences of alterations in expression levels and structural modifications of sperm proteins with diverse functions is detailed. Moreover, the use of cryotolerance biomarkers as predictors of the potential resilience of a sperm sample to the cryopreservation process is also discussed. Regarding the proteins that have been identified to be relevant during the cryopreservation process, they are classified according to the functions they carry out in sperm, including antioxidant function, plasma membrane protection, sperm motility regulation, chromatin structure, metabolism and mitochondrial function, heat-shock response, premature capacitation and sperm-oocyte binding and fusion. Special reference is made to the relevance of sperm membrane channels, as their function is crucial for boar sperm to withstand osmotic shock during cryopreservation. Finally, potential aims for future research on cryodamage and cryotolerance are proposed, which might be crucial to minimise the side-effects of cryopreservation and to make it a more advantageous strategy for boar sperm preservation.

Anti-sperm Antibodies as an Increasing Threat to Male Fertility: Immunological Insights, Diagnostic and Therapeutic Strategies

It is a fact that sperm possess antigenic properties. Substantial scientific research suggests that specific antibodies that attach to sperm antigens can induce infertility in both humans and other species. Antisperm antibodies (ASA) represent a significant etiology of infertility in humans, leading to immunoinfertility. The association between ASA and infertility is multifaceted. The observation of sperm agglutination, although not conclusive for the diagnosis of immunological infertility, may suggest the presence of ASA. Nevertheless, ASA may also manifest in the lack of any sperm agglutination. Managing ASA from an andrological perspective depends on the underlying cause and the specific approaches healthcare professionals adopt. The precise etiology of male infertility resulting from ASA remains unclear. Current research has examined the impact of ASA and its prevalence among infertile males to understand the relationship between ASA and changes in semen parameters. However, the findings have been inconclusive. Numerous techniques have been documented for the management of immunoinfertility. This review examines the importance of ASA in the context of infertility, encompassing the postulated mechanisms underlying the development of ASA, the various assays employed for detecting them, and the available treatments.

Molecular functions of moonlighting proteins in cell metabolic processes

Moonlighting proteins have more than one physiologically significant role within one polypeptide chain. The multifunctionality of proteins was first described in 1987 by Joram Piatigorsky and Graeme Wistow. Cells can benefit from involvement of these proteins in biological processes in several ways, e.g. at the energy level. Furthermore, cells have developed a number of mechanisms to change these proteins' functions. Moonlighting proteins are found in all types of organisms, including prokaryotes, eukaryotes, and even viruses. These proteins include a variety of enzymes that serve as receptors, secreted cytokines, transcription factors, or proteasome components. Additionally, there are many combinations of functions, e.g. among receptors and transcription factors, chaperones and cytokines, as well as transcription factors within the ribosome. This work describes enzymes involved in several important metabolic processes in cells, namely cellular respiration, gluconeogenesis, the urea cycle, and pentose phosphate metabolism.

Decreased Klotho Expression Causes Accelerated Decline of Male Fecundity through Oxidative Injury in Murine Testis

Oxidative stress is the etiology for 30-80% of male patients affected by infertility, which is a major health problem worldwide. Klotho protein is an aging suppressor that functions as a humoral factor modulating various cellular processes including antioxidation and anti-inflammation, and its dysregulation leads to human pathologies. Male mice lacking Klotho are sterile, and decreased Klotho levels in the serum are observed in men suffering from infertility with lower sperm counts. However, the mechanism by which Klotho maintains healthy male fertility remains unclear. Klotho haplodeficiency (Kl+/-) accelerates fertility reduction by impairing sperm quality and spermatogenesis in Kl+/- mice. Testicular proteomic analysis revealed that loss of Klotho predominantly disturbed oxidation and the glutathione-related pathway. We further focused on the glutathione-S-transferase (GST) family which counteracts oxidative stress in most cell types and closely relates with fertility. Several GST proteins, including GSTP1, GSTO2, and GSTK1, were significantly downregulated, which subsequently resulted in increased levels of the lipid peroxidation product 4-hydroxynonenal and apoptosis in murine testis with low or no expression of Klotho. Taken together, the loss of one Kl allele accelerates male fecundity loss because diminished antioxidant capability induces oxidative injury in mice. This is the first study that highlights a connection between Klotho and GST proteins.

Human sperm cooperate to transit highly viscous regions on the competitive pathway to fertilization

Human sperm compete for fertilization. Here, we find that human sperm, unexpectedly, cooperate under conditions mimicking the viscosity contrasts in the female reproductive tract. Sperm attach at the head region to migrate as a cooperative group upon transit into and through a high viscosity medium (15-100 cP) from low viscosity seminal fluid. Sperm groups benefit from higher swimming velocity, exceeding that of individual sperm by over 50%. We find that sperm associated with a group possess high DNA integrity (7% fragmentation index) - a stark contrast to individual sperm exhibiting low DNA integrity (> 50% fragmentation index) - and feature membrane decapacitation factors that mediate sperm attachment to form the group. Cooperative behaviour becomes less prevalent upon capacitation and groups tend to disband as the surrounding viscosity reduces. When sperm from different male sources are present, related sperm preferentially form groups and achieve greater swimming velocity, while unrelated sperm are slowed by their involvement in a group. These findings reveal cooperation as a selective mode of human sperm motion - sperm with high DNA integrity cooperate to transit the highly viscous regions in the female tract and outcompete rival sperm for fertilization - and provide insight into cooperation-based sperm selection strategies for assisted reproduction.

Proteomic changes in human spermatozoa during in vitro capacitation and acrosome reaction in normozoospermia and asthenozoospermia

BACKGROUND

The cellular and molecular mechanisms of the events that help spermatozoa acquire their fertilizing capability during capacitation and acrosome reaction are not completely understood.

OBJECTIVE

This study was performed with a postulation that the identification of sperm proteins and their changes during in vitro capacitation and acrosome reaction will unravel unknown molecular aspects of fertilization that impact male fertility.

MATERIALS AND METHODS

Spermatozoa collected from sequential conditions, that is, separation of ejaculated spermatozoa by Percoll gradient centrifugation, in vitro capacitation, and acrosome reaction were processed for tandem mass spectrometric analysis, followed by protein identification, label-free quantitation, and statistical analysis.

RESULTS AND DISCUSSION

Collectively, a total of 1088 sperm proteins were identified. In comparison to ejaculated spermatozoa, 44 and 141 proteins were differentially expressed in capacitated and acrosome reacted spermatozoa, respectively. A large number of proteins were found downregulated, including clusterin, pyruvate dehydrogenase E1 component, semenogelin-1 and 2, heat shock protein 90, beta-microseminoprotein, and keratin. It was expected as sperm-membrane-associated proteins are removed during capacitation. There were significant proteomic alterations in asthenozoospermia compared to normozoospermia; however, variation was more noticeable among proteins of acrosome reacted spermatozoa and those released during the acrosome reaction. The processes enriched among downregulated proteins in asthenozoospermia included acrosome assembly, binding of spermatozoa to zona pellucida, nucleosome assembly, flagellated sperm motility, protein folding, oxidative phosphorylation, tricarboxylic acid cycle, chromatin silencing, gluconeogenesis, glycolytic process, and glycolysis.

CONCLUSION

The dynamic information generated about proteomic alterations in spermatozoa during capacitation and acrosome reaction and their variability in asthenozoospermia will contribute not only to enhancing our understanding of processes that prepare spermatozoa to acquire fertilization capability but also help in deciphering novel factors of male infertility.

The role of spermatozoa-zona pellucida interaction in selecting fertilization-competent spermatozoa in humans

Human fertilization begins when a capacitated spermatozoon binds to the zona pellucida (ZP) surrounding a mature oocyte. Defective spermatozoa-ZP interaction contributes to male infertility and is a leading cause of reduced fertilization rates in assisted reproduction treatments (ARTs). Human ejaculate contains millions of spermatozoa with varying degrees of fertilization potential and genetic quality, of which only thousands of motile spermatozoa can bind to the ZP at the fertilization site. This observation suggests that human ZP selectively interacts with competitively superior spermatozoa characterized by high fertilizing capability and genetic integrity. However, direct evidence for ZP-mediated sperm selection process is lacking. This study aims to demonstrate that spermatozoa-ZP interaction represents a crucial step in selecting fertilization-competent spermatozoa in humans. ZP-bound and unbound spermatozoa were respectively collected by a spermatozoa-ZP coincubation assay. The time-course data demonstrated that ZP interacted with a small proportion of motile spermatozoa. Heat shock 70 kDa protein 2 (HSPA2) and sperm acrosome associated 3 (SPACA 3) are two protein markers associated with the sperm ZP-binding ability. Immunofluorescent staining indicated that the ZP-bound spermatozoa had significantly higher expression levels of HSPA2 and SPACA3 than the unbound spermatozoa. ZP-bound spermatozoa had a significantly higher level of normal morphology, DNA integrity, chromatin integrity, protamination and global methylation when compared to the unbound spermatozoa. The results validated the possibility of applying spermatozoa-ZP interaction to select fertilization-competent spermatozoa in ART. This highly selective interaction might also provide diagnostic information regarding the fertilization potential and genetic qualities of spermatozoa independent of those derived from the standard semen analysis.

Elucidating breed-specific variants of native pigs in Korea: insights into pig breeds' genomic characteristics

Although conserving native pig breeds is important in Korea, research on the genomic aspects to identify breed-specific variations in native pig breeds is uncommon. Single nucleotide polymorphisms (SNPs) can be a powerful source for identifying breed-specific variants. We used whole genome sequencing data, including Jeju Native Pig (JNP), Korean Native Pig (KNP), Korean Wild Boar (KWB), and other western commercial pig breeds to determine native pig breed-specific SNPs. Furthermore, the goal was not only to determine the genomic specificity of native pig breeds but also to identify SNPs that carry breed-specific information (breed-informative SNPs) that can be related to breed characteristics. The representative characteristics of native pigs are their unique meat quality and disease resistance. We surveyed the gene ontology (GO) of native pigs with breed-specific SNPs. Examining the genes associated with GO may contribute to revealing the reasons for the unique characteristics of native pig breeds. The enriched GOs terms were neuron projection development, cell surface receptor signaling pathway, ion homeostasis in JNP, cell adhesion and wound healing in KNP, and DNA repair and reproduction in KWB. We expect that this study of breed-specific SNPs will enable us to gain a deeper understanding of native pigs in Korea.

Unbalanced Expression of Glutathione Peroxidase 4 and Arachidonate 15-Lipoxygenase Affects Acrosome Reaction and In Vitro Fertilization

Glutathione peroxidase 4 (Gpx4) and arachidonic acid 15 lipoxygenase (Alox15) are counterplayers in oxidative lipid metabolism and both enzymes have been implicated in spermatogenesis. However, the roles of the two proteins in acrosomal exocytosis have not been explored in detail. Here we characterized Gpx4 distribution in mouse sperm and detected the enzyme not only in the midpiece of the resting sperm but also at the anterior region of the head, where the acrosome is localized. During sperm capacitation, Gpx4 translocated to the post-acrosomal compartment. Sperm from Gpx4^+/Sec46Ala mice heterozygously expressing a catalytically silent enzyme displayed an increased expression of phosphotyrosyl proteins, impaired acrosomal exocytosis after in vitro capacitation and were not suitable for in vitro fertilization. Alox15-deficient sperm showed normal acrosome reactions but when crossed into a Gpx4-deficient background spontaneous acrosomal exocytosis was observed during capacitation and these cells were even less suitable for in vitro fertilization. Taken together, our data indicate that heterozygous expression of a catalytically silent Gpx4 variant impairs acrosomal exocytosis and in vitro fertilization. Alox15 deficiency hardly impacted the acrosome reaction but when crossed into the Gpx4-deficient background spontaneous acrosomal exocytosis was induced. The detailed molecular mechanisms for the observed effects may be related to the compromised redox homeostasis.

Glutathione S-transferase Mu 3 is associated to in vivo fertility, but not sperm quality, in bovine

In the dairy breeding industry, pregnancy of dairy cows is essential to initiate milk production, so that high fertility rates are required to increase their productivity. In this regard, sperm proteins that are indicative of sperm quality and/or fertility have become an important target of study. Glutathione S-transferase Mu 3 (GSTM3) has been established as a fertility and sperm quality parameter in humans and pigs and, consequently, it might be a potential biomarker in cattle. For this reason, the present work aimed to determine if GSTM3 could predict sperm quality and in vivo fertility in this species. Sperm quality was assessed with flow cytometry and computer-assisted sperm analysis. Immunoblotting and immunofluorescence analysis were performed to determine the presence and localisation pattern of sperm GSTM3. This enzyme was found to be present in bovine sperm and to be localised along the sperm tail and the equatorial segment of the head. No significant associations between sperm GSTM3 and sperm quality parameters were observed, except a negative association with morphologically abnormal sperm having a coiled tail. In addition, and more relevant, higher levels of GSTM3 in sperm were seen in bulls showing lower in vivo fertility rates. In conclusion, our data evidenced the presence of GSTM3 in bovine sperm. Moreover, we suggest that, despite not being associated with sperm quality, GSTM3 might be an in vivo subfertility biomarker in cattle sperm, and that high levels of this protein could be an indicative of defective spermatogenesis and/or epididymal maturation.

A loss-of-function variant in SSFA2 causes male infertility with globozoospermia and failed oocyte activation

Globozoospermia (OMIM: 102530) is a rare type of teratozoospermia (< 0.1%). The etiology of globozoospermia is complicated and has not been fully revealed. Here, we report an infertile patient with globozoospermia. Variational analysis revealed a homozygous missense variant in the SSFA2 gene (NM_001130445.3: c.3671G > A; p.R1224Q) in the patient. This variant significantly reduced the protein expression of SSFA2. Immunofluorescence staining showed positive SSFA2 expression in the acrosome of human sperm. Liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) and Coimmunoprecipitation (Co-IP) analyses identified that GSTM3 and Actin interact with SSFA2. Further investigation revealed that for the patient, regular intracytoplasmic sperm injection (ICSI) treatment had a poor prognosis. However, Artificial oocyte activation (AOA) by a calcium ionophore (A23187) after ICSI successfully rescued the oocyte activation failure for the patient with the SSFA2 variant, and the couple achieved a live birth. This study revealed that SSFA2 plays an important role in acrosome formation, and the homozygous c.3671G > A loss-of-function variant in SSFA2 caused globozoospermia. SSFA2 may represent a new gene in the genetic diagnosis of globozoospermia, especially the successful outcome of AOA-ICSI treatment for couples, which has potential value for clinicians in their treatment regimen selections.

The Proteomic Modification of Buck Ejaculated Sperm Induced by the Cryopreservation Process

Using two-dimensional electrophoresis along with mass spectroscopy, we have investigated how the cryopreservation process affected the protein profile of goat ejaculated sperm. In this study, five bucks were used for semen collection. After removal of seminal plasma, the Tris-based extender containing glycerol and egg yolk was used to freeze semen. The results indicated that the post-thaw sperm quality showed a significant reduction compared with fresh sperm. The numbers of protein spots acquired in fresh and post-thaw sperm were 2926 ± 57 and 3061 ± 81, respectively. Twenty-two different abundant proteins (DAPs) were identified between fresh sperm and frozen-thawed sperm (≥3.0-folds, p < 0.05). The abundances of 19 proteins were significantly higher in the fresh sperm than the post-thaw sperm. The results of the gene ontology annotation showed the primary location of the DAPs on sperm cytoskeleton, protein complex, cytoplasm, and mitochondria. In addition, these proteins were mainly involved in ion binding, small molecular metabolic processes, structure molecule activity, guanosine triphosphatase activity, oxidoreductase activity, and protein complex assembly. The interaction networks among these DAPs demonstrated that they may play roles in oxidoreductase activity, structure, acrosomal function, and motility of sperm. Collectively, the proteome of goat sperm was altered during the cryopreservation process, demonstrating that protein modification induced by cryopreservation may be associated with the reduced quality of goat sperm after thawing.

Chronic stress inhibits testosterone synthesis in Leydig cells through mitochondrial damage via Atp5a1

Stress is one of the leading causes of male infertility, but its exact function in testosterone synthesis has scarcely been reported. We found that adult male rats show a decrease in bodyweight, genital index and serum testosterone level after continual chronic stress for 21 days. Two-dimensional gel electrophoresis (2-DE) and MALDI-TOF-MS analysis identified 10 differentially expressed proteins in stressed rats compared with controls. A strong protein interaction network was found to be centred on Atp5a1 among these proteins. Atp5a1 expression significantly decreased in Leydig cells after chronic stress. Transfection of Atp5a1 siRNAs decreased StAR, CYP11A1, and 17β-HSD expression by damaging the structure of mitochondria in TM3 cells. This study confirmed that chronic stress plays an important role in testosterone synthesis by regulating Atp5a1 expression in Leydig cells.

Glutathione S-transferase kappa 1 is positively related with sperm quality of porcine sperm

The glutathione S-transferase (GST) superfamily members play an important role in the male reproductive tract and sperm physiology. However, the expression profiles of some members of this protein family and their effect on sperm quality remain unclear. In this study, we found that GST kappa 1 (GSTK1) encoded protein is abundant in the testes and capacitated sperm acrosome. Western blot analysis revealed that the decreased abundance of GSTK1 was observed in low motile spermatozoa; moreover, GSTK1 expression decreased in sperm stored at 17°C under a long preservation time. In vitro analyses revealed that GSTK1 had no significant effect on sperm motility, capacitation, or acrosome reaction. Notably, after capacitated sperm were incubated with 4 and 8 μg/ml anti-GSTK1 antibodies, the fertilization rate significantly decreased in vitro fertilization assay. The current study demonstrates that GSTK1 is correlated with sperm quality and is a promising marker for the assessment of sperm quality and provides a basis for understanding the potential molecular mechanism for targeting pathogenic factors in male infertility.

Influence of Risk Factors for Male Infertility on Sperm Protein Composition

Male infertility is a common health problem that can be influenced by a host of lifestyle risk factors such as environment, nutrition, smoking, stress, and endocrine disruptors. These effects have been largely demonstrated on sperm parameters (e.g., motility, numeration, vitality, DNA integrity). In addition, several studies showed the deregulation of sperm proteins in relation to some of these factors. This review inventories the literature related to the identification of sperm proteins showing abundance variations in response to the four risk factors for male infertility that are the most investigated in this context: obesity, diabetes, tobacco smoking, and exposure to bisphenol-A (BPA). First, we provide an overview of the techniques used to identify deregulated proteins. Then, we summarise the main results obtained in the different studies and provide a compiled list of deregulated proteins in relation to each risk factor. Gene ontology analysis of these deregulated proteins shows that oxidative stress and immune and inflammatory responses are common mechanisms involved in sperm alterations encountered in relation to the risk factors.

Moonlighting Biochemistry of Cysteine Synthase: A Species-specific Global Regulator

Cysteine Synthase (CS), the enzyme that synthesizes cysteine, performs non-canonical regulatory roles by binding and modulating functions of disparate proteins. Beyond its role in catalysis and regulation in the cysteine biosynthesis pathway, it exerts its moonlighting effect by binding to few other proteins which possess a C-terminal "CS-binding motif", ending with a terminal ILE. Therefore, we hypothesized that CS might regulate many other disparate proteins with the "CS-binding motif". In this study, we developed an iterative sequence matching method for mapping moonlighting biochemistry of CS and validated our prediction by analytical and structural approaches. Using a minimal protein-peptide interaction system, we show that five previously unknown CS-binder proteins that participate in diverse metabolic processes interact with CS in a species-specific manner. Furthermore, results show that signatures of protein-protein interactions, including thermodynamic, competitive-inhibition, and structural features, highly match the known CS-Binder, serine acetyltransferase (SAT). Together, the results presented in this study allow us to map the extreme multifunctional space (EMS) of CS and reveal the biochemistry of moonlighting space, a subset of EMS. We believe that the integrated computational and experimental workflow developed here could be further modified and extended to study protein-specific moonlighting properties of multifunctional proteins.

The search for molecular mimicry in proteins carried by extracellular vesicles secreted by cells infected with Plasmodium falciparum

Red blood cells infected with Plasmodium falciparum secrete extracellular vesicles in order to facilitate the survival and infection of human cells. Various researchers have studied the composition of these extracellular vesicles and identified the proteins contained inside. In this work, we used that information to detect potential P. falciparum molecules that could be imitating host proteins. We carried out several searches to detect sequences and structural similarities between the parasite and host. Additionally, the possibility of functional mimicry was explored in line with the potential role that each candidate can perform for the parasite inside the host. Lastly, we determined a set of eight sequences (mainly moonlighting proteins) with a remarkable resemblance to human proteins. Due to the resemblance observed, this study proposes the possibility that certain P. falciparum molecules carried by extracellular vesicles could be imitating human proteins to manipulate the host cell's physiology.

Protein Identification of Spermatozoa and Seminal Plasma in Bottlenose Dolphin (Tursiops truncatus)

Proteins play an important role in many reproductive functions such as sperm maturation, sperm transit in the female genital tract or sperm-oocyte interaction. However, in general, little information concerning reproductive features is available in the case of aquatic animals. The present study aims to characterize the proteome of both spermatozoa and seminal plasma of bottlenose dolphins (Tursiops truncatus) as a model organism for cetaceans. Ejaculate samples were obtained from two trained dolphins housed in an aquarium. Spermatozoa and seminal plasma were analyzed by means of proteomic analyses using an LC-MS/MS, and a list with the gene symbols corresponding to each protein was submitted to the DAVID database. Of the 419 proteins identified in spermatozoa and 303 in seminal plasma, 111 proteins were shared by both. Furthermore, 70 proteins were identified as involved in reproductive processes, 39 in spermatozoa, and 31 in seminal plasma. The five most abundant proteins were also identified in these samples: AKAP3, ODF2, TUBB, GSTM3, ROPN1 for spermatozoa and CST11, LTF, ALB, HSP90B1, PIGR for seminal plasma. In conclusion, this study provides the first characterization of the proteome in cetacean sperm and seminal plasma, opening the way to future research into new biomarkers, the analysis of conservation capacity or possible additional applications in the field of assisted reproductive technologies.

Moonlighting Proteins: The Case of the Hexokinases

Moonlighting proteins are defined as proteins with two or more functions that are unrelated and independent to each other, so that inactivation of one of them should not affect the second one and vice versa. Intriguingly, all the glycolytic enzymes are described as moonlighting proteins in some organisms. Hexokinase (HXK) is a critical enzyme in the glycolytic pathway and displays a wide range of functions in different organisms such as fungi, parasites, mammals, and plants. This review discusses HXKs moonlighting functions in depth since they have a profound impact on the responses to nutritional, environmental, and disease challenges. HXKs’ activities can be as diverse as performing metabolic activities, as a gene repressor complexing with other proteins, as protein kinase, as immune receptor and regulating processes like autophagy, programmed cell death or immune system responses. However, most of those functions are particular for some organisms while the most common moonlighting HXK function in several kingdoms is being a glucose sensor. In this review, we also analyze how different regulation mechanisms cause HXK to change its subcellular localization, oligomeric or conformational state, the response to substrate and product concentration, and its interactions with membrane, proteins, or RNA, all of which might impact the HXK moonlighting functions.

SERPIN A5 may have a potential as a biomarker in reflecting the improvement of semen quality in infertile men who underwent varicocele repair

We aimed to identify proteins that were differentially regulated in spermatozoal samples collected from fertile healthy men (FHM) and infertile patients with varicocele (IFPV) before and after varicocelectomy. Seminal samples were collected from 20 IFPV before and after varicocelectomy and from 14 FHM as controls. Samples underwent seminal examination and proteomic analysis. Extracted spermatozoal proteins were analysed using two-dimensional gel electrophoresis, and differentially regulated spermatozoal proteins (DRSPs) were identified. In particular, attention was placed on those DRSPs in which the concentration changed after varicocelectomy and corrected to approximate levels observed in FHM. Varicocelectomy significantly improved the sperm count and concentration in IFPV (p < 0.05). Proteomic analysis showed that 11 DRSPs were identified when comparisons were made among the three groups. Among these 11 proteins, change in the SERPIN A5 concentrations was notable because it was 100-fold downregulated in pre-operative IFPV samples and nearly resembled to control concentrations following varicocelectomy. Western blot analysis using an anti-SERPIN antibody validated the changes observed in SERPIN A5 levels before and after varicocelectomy operation. Increase in SERPIN A5 after varicocelectomy may be due to improvement in semen quality, suggesting that SERPIN A5 is a potential seminal biomarker for assessment of semen quality in varicocele-related infertility.

The inhibition of spermatic cystine/glutamate antiporter xCT (SLC7A11) influences the ability of cryopreserved stallion sperm to bind to heterologous zonae pellucidae

Sperm are redox-regulated cells, and deregulation of their redox status is considered to affect male fertility and to reduce their fertilizing ability following biotechnological procedures, such as cryopreservation. Cystine (CysS), after incorporation in sperm via SLC7A11 antiporter, has been demonstrated to increase intracellular GSH content, the most important non enzymatic antioxidant. This study was aimed at investigating the role of SLC7A11 antiporter on frozen-thawed stallion sperm ability to respond to in vitro capacitating environment after post-thaw incubation with CysS and/or Sulfasalazine (SS), a specific inhibitor of SLC7A11 antiporter. Viability, motility, immunolocalization of tyrosine phosphorylated proteins and the ability to bind to heterologous zonae pellucidae were evaluated. Thawed sperm from seven stallions (2 ejaculates/stallion) was washed and resuspended in Tyrodes media; each thawed ejaculate was divided in Control (CTR) and 3 samples supplemented with: 0.5 mM Cystine (CysS), 500 μM Sulfasalazine (SS) and 0.5 mM CysS + 500 μM SS (CysS + SS). After 1 h of incubation at 37 °C, samples were washed twice, resuspended in capacitating BWW medium and incubated at 38 °C under 5% CO₂. After 30 and 60 min, sperm motility, viability and tyrosine phosphorylated protein immunolocalization, used as capacitation status index, were evaluated. After 30 min of capacitation, 4 × 10⁵ sperm were co-incubated with denuded pig oocytes in capacitation medium for 30 min for the heterologous binding assay. None of the sperm parameters studied (motility, viability and tyrosine phosphorylation) showed any difference respective to control. The number of sperm bound per oocyte (mean ± SEM) tended to increase in CysS group (44.0 ± 12.3) respect CTR (40.8 ± 10.8) while decreased in SS group (32.4 ± 7.8) (p < 0.01). Moreover, CysS + SS group showed a lower binding rate (32.0 ± 10.0) compared to CysS (p < 0.001). Our results suggest that CysS supplementation of thawed stallion sperm can influence their ability to bind to heterologous zona pellucidae as the inhibition of CysS incorporation by SLC7A11 reduced the number of sperm bound per oocyte. This effect does not seem to be ascribed to a modification of sperm motility, membrane integrity and tyrosine phosphorylation.

Ligands and Receptors Involved in the Sperm-Zona Pellucida Interactions in Mammals

Sperm-zona pellucida (ZP) interaction, involving the binding of sperm surface ligands to complementary carbohydrates of ZP, is the first direct gamete contact event crucial for subsequent gamete fusion and successful fertilization in mammals. It is a complex process mediated by the coordinated engagement of multiple ZP receptors forming high-molecular-weight (HMW) protein complexes at the acrosomal region of the sperm surface. The present article aims to review the current understanding of sperm-ZP binding in the four most studied mammalian models, i.e., murine, porcine, bovine, and human, and summarizes the candidate ZP receptors with established ZP affinity, including their origins and the mechanisms of ZP binding. Further, it compares and contrasts the ZP structure and carbohydrate composition in the aforementioned model organisms. The comprehensive understanding of sperm-ZP interaction mechanisms is critical for the diagnosis of infertility and thus becomes an integral part of assisted reproductive therapies/technologies.

Elucidating the processes and pathways enriched in buffalo sperm proteome in regulating semen quality

Sperm carries a reservoir of proteins regulating the molecular functions to attain functional competence. Semen samples collected from buffalo bulls were assessed for sperm functional attributes (n = 11) and proteome profiling (n = 6). Sperm proteins were extracted and profiled by employing LC-MS/MS. Overall, the buffalo sperm contained 1365 proteins, of which 458 were common between the groups. The unique proteins were 477 and 430 in good and poor quality semen, respectively. In the whole proteome of buffalo sperm, sexual reproduction with phosphatidylethanolamine-binding protein1 (PEBP1), fetuin-B (FETUB) and acrosin (ACR) was the most enriched (p = 8.44E-19) biological process, also with thermogenesis (p = 0.003), oocyte meiosis (p = 0.007) and vascular smooth muscle contraction (p = 0.009) apart from metabolic pathways. In good quality semen, mesenchyme migration (p = 1.24E-07) and morphogenesis (p = 0.001) were abundant biological processes. In good quality semen, the fluid shear stress (p = 0.01) and, in poor quality semen, valine, leucine and isoleucine degradation (p = 3.8E-05) pathways were enriched. In good quality semen, 7 proteins were significantly (p < 0.05) upregulated and 33 proteins were significantly (p < 0.05) downregulated. On validating the abundantly expressed sperm proteins, serine protease inhibitor Kazal-type 2-like (SPINK2; 2.17-fold) and neddylin (NEDD8; 1.13-fold) were upregulated and YBX2 was downregulated (0.41-fold) in good quality semen as compared with poor quality semen (1-fold). The present findings revealed the importance of sperm proteins in oocyte maturation, fertilization process and early embryonic development. The variations in the proteomic composition can be used as potential markers for the selection of breeding bulls.

The triple role of glutathione S-transferases in mammalian male fertility

Male idiopathic infertility accounts for 15-25% of reproductive failure. One of the factors that has been linked to this condition is oxidative stress (OS), defined as the imbalance between antioxidants and reactive oxygen species. Amongst the different factors that protect the cell against OS, the members of the glutathione S-transferase (GST) superfamily play an important role. Interestingly, reduction or lack of some GSTs has been associated to infertility in men. Therefore, and to clarify the relationship between GSTs and male fertility, the aim of this work is to describe the role that GSTs play in the male reproductive tract and in sperm physiology. To that end, the present review provides a novel perspective on the triple role of GSTs (detoxification, regulation of cell signalling and fertilisation), and reports their localisation in sperm, seminal plasma and the male reproductive tract. Furthermore, we also tackle the existing correlation between some GST classes and male fertility. Due to the considerable impact of GSTs in human pathology and their tight relationship with fertility, future research should address the specific role of these proteins in male fertility, which could result in new approaches for the diagnosis and/or treatment of male infertility.

Proteomic Changes in Human Sperm During Sequential in vitro Capacitation and Acrosome Reaction

The male gamete is not completely mature after ejaculation and requires further events in the female genital tract to acquire fertilizing ability, including the processes of capacitation and acrosome reaction. In order to shed light on protein changes experienced by the sperm cell in preparation for fertilization, a comprehensive quantitative proteomic profiling based on isotopic peptide labeling and liquid chromatography followed by tandem mass spectrometry was performed on spermatozoa from three donors of proven fertility under three sequential conditions: purification with density gradient centrifugation, incubation with capacitation medium, and induction of acrosome reaction by exposure to the calcium ionophore A23187. After applying strict selection criteria for peptide quantification and for statistical analyses, 36 proteins with significant changes in their relative abundance within sperm protein extracts were detected. Moreover, the presence of peptide residues potentially harboring sites for post-translational modification was revealed, suggesting that protein modification may be an important mechanism in sperm maturation. In this regard, increased levels of proteins mainly involved in motility and signaling, both regulated by protein modifiers, were detected in sperm lysates following incubation with capacitation medium. In contrast, less abundant proteins in acrosome-reacted cell lysates did not contain potentially modifiable residues, suggesting the possibility that all those proteins might be relocated or released during the process. Protein-protein interaction analysis revealed a subset of proteins potentially involved in sperm maturation, including the proteins Erlin-2 (ERLIN2), Gamma-glutamyl hydrolase (GGH) and Transmembrane emp24 domain-containing protein 10 (TMED10). These results contribute to the current knowledge of the molecular basis of human fertilization. It should now be possible to further validate the potential role of the detected altered proteins as modulators of male infertility.

GSTM3, but not IZUMO1, is a cryotolerance marker of boar sperm

Background

Cryopreservation is currently the most efficient method for long-term preservation of mammalian gametes and is extensively used in swine artificial insemination (AI) centres. However, it is well-known that cryopreservation procedures induce changes in the water phase in both intra and extracellular compartments, which alter the content and localisation of several proteins and ends up curtailing the structural integrity of functional sperm (i.e., cryoinjuries). Alterations and deficiencies of sperm-oocyte binding proteins during gamete recognition are one of the causes of reproductive failure both in vitro and in vivo. In this sense, characterisation of cryopreservation effects upon oocyte-binding proteins of sperm, such as IZUMO1 and GSTM3, is essential when assessing the impact of this technique in swine reproduction.

Results

Cryopreservation was found to induce changes in the localisation of IZUMO1 and GSTM3 in boar sperm. However, the relative content of both proteins was not altered after thawing. Furthermore, whereas IZUMO1 content was found not to be related to the cryotolerance of boar sperm, GSTM3 content was observed to be higher in poor (PFE) than in good (GFE) freezability ejaculates in both pre-frozen (1.00 INT·mm² ± 0.14 INT·mm² vs. 0.72 INT·mm² ± 0.15 INT·mm²; P < 0.05) and post-thawed (0.96 INT·mm² ± 0.20 INT·mm² vs. 70 INT·mm² ± 0.19 INT·mm²; P < 0.05) samples. Moreover, GSTM3 levels were found to be higher in those spermatozoa that exhibited low mitochondrial activity, high reactive oxygen species (ROS) production, and high membrane lipid disorder post-thaw (P < 0.05).

Conclusions

The difference in GSTM3 content between GFE and PFE, together with this protein having been found to be related to poor sperm quality post-thaw, suggests that it could be used as a cryotolerance marker of boar spermatozoa. Furthermore, both IZUMO1 and GSTM3 relocate during cryopreservation, which could contribute to the reduced fertilising capacity of frozen-thawed boar sperm.

Electronic supplementary material

The online version of this article (10.1186/s40104-019-0370-5) contains supplementary material, which is available to authorized users.

Sperm Proteome Analysis and Identification of Fertility-Associated Biomarkers in Unexplained Male Infertility

Up to 30% of men with normal semen parameters suffer from infertility and the reason for this is unknown. Altered expression of sperm proteins may be a major cause of infertility in these men. Proteomic profiling was performed on pooled semen samples from eight normozoospermic fertile men and nine normozoospermic infertile men using LC-MS/MS. Furthermore, key differentially expressed proteins (DEPs) related to the fertilization process were selected for validation using Western blotting. A total of 1139 and 1095 proteins were identified in normozoospermic fertile and infertile men, respectively. Of these, 162 proteins were identified as DEPs. The canonical pathway related to free radical scavenging was enriched with upregulated DEPs in normozoospermic infertile men. The proteins associated with reproductive system development and function, and the ubiquitination pathway were underexpressed in normozoospermic infertile men. Western blot analysis revealed the overexpression of annexin A2 (ANXA2) (2.03 fold change; P = 0.0243), and underexpression of sperm surface protein Sp17 (SPA17) (0.37 fold change; P = 0.0205) and serine protease inhibitor (SERPINA5) (0.32 fold change; P = 0.0073) in men with unexplained male infertility (UMI). The global proteomic profile of normozoospermic infertile men is different from that of normozoospermic fertile men. Our data suggests that SPA17, ANXA2, and SERPINA5 may potentially serve as non-invasive protein biomarkers associated with the fertilization process of the spermatozoa in UMI.

An enzyme in the test tube, and a transcription factor in the cell: Moonlighting proteins and cellular factors that affect their behavior

In the cell, expression levels, allosteric modulators, post-translational modifications, sequestration, and other factors can affect the level of protein function. For moonlighting proteins, cellular factors like these can also affect the kind of protein function. This minireview discusses examples of moonlighting proteins that illustrate how a single protein can have different functions in different cell types, in different intracellular locations, or under varying cellular conditions. This variability in the kind of protein activity, added to the variability in the amount of protein activity, contributes to the difficulty in predicting the behavior of proteins in the cell.

Rainbow-Seq: Combining Cell Lineage Tracing with Single-Cell RNA Sequencing in Preimplantation Embryos

We developed the Rainbow-seq technology to trace cell division history and reveal single-cell transcriptomes. With distinct fluorescent protein genes as lineage markers, Rainbow-seq enables each single-cell RNA sequencing (RNA-seq) experiment to simultaneously decode the lineage marker genes and read single-cell transcriptomes. We triggered lineage tracking in each blastomere at the 2-cell stage, observed microscopically inequivalent contributions of the progeny to the two embryonic poles at the blastocyst stage, and analyzed every single cell at either 4- or 8-cell stage with deep paired-end sequencing of full-length transcripts. Although lineage difference was not marked unequivocally at a single-gene level, it became clear when the transcriptome was analyzed as a whole. Moreover, several groups of novel transcript isoforms with embedded repeat sequences exhibited lineage difference, suggesting a possible link between DNA demethylation and cell fate decision. Rainbow-seq bridged a critical gap between division history and single-cell RNA-seq assays.

Protein moonlighting: what is it, and why is it important?

Members of the GroEL/HSP60 protein family have been studied for many years because of their critical roles as ATP-dependent molecular chaperones, so it might come as a surprise that some have important functions in ATP-poor conditions, for example, when secreted outside the cell. At least some members of each of the HSP10, HSP70, HSP90, HSP100 and HSP110 heat shock protein families are also 'moonlighting proteins'. Moonlighting proteins exhibit more than one physiologically relevant biochemical or biophysical function within one polypeptide chain. In this class of multifunctional proteins, the multiple functions are not due to gene fusions or multiple proteolytic fragments. Several hundred moonlighting proteins have been identified, and they include a diverse set of proteins with a large variety of functions. Some participate in multiple biochemical processes by using an active site pocket for catalysis and a different part of the protein's surface to interact with other proteins. Moonlighting proteins play a central role in many diseases, and the development of novel treatments would be aided by more information addressing current questions, for example, how some are targeted to multiple cellular locations and how a single function can be targeted by therapeutics without targeting a function not involved in disease.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

Detection of sperm-reactive antibodies in wild sika deer and identification of the sperm antigens

Antisperm antibodies potentially inhibit sperm functions causing the sterility in humans and experimentally treated animals. However, there is no information about antisperm antibodies emerging spontaneously in wildlife. In this study, we searched for the sperm-reactive antibodies, spontaneously produced in wild sika deer (Cervus nippon), and identified the sperm antigens. We collected 529 fecal masses of sika deer in Japanese cities, from which we extracted the mucosal antibodies to test them for reactivities to deer sperm proteins by ELISA. Two of the extracts contained IgAs that were highly reactive to the sperm proteins. The molecular weights of the active IgAs, partially purified by DEAE-sephadex A-50, were estimated at more than 100 kDa, suggesting that the IgAs evaded drastic digestion in the gastrointestinal tract. Two-dimensional electrophoresis and immunoblotting detected three major antigens, and the following LC-MS/MS analysis identified them as alpha-enolase, phosphoglycerate kinase 2 and acrosin-binding protein. The antibodies were cross-reactive to a recombinant human acrosin-binding protein. To our knowledge, this is the first research to find that the sperm-reactive antibodies are produced spontaneously in wildlife and they recognize a common antigen found in humans.

Moonlighting proteins - nature's Swiss army knives

The human body is a complex biological machine with billions of cells and vast numbers of biochemical processes - but our genome only contains 22,000 protein-encoding genes. Moonlighting proteins provide one way to increase the number of cellular activities. Moonlighting proteins exhibit more than one physiologically relevant biochemical or biophysical function within one polypeptide chain. Already more than 300 moonlighting proteins have been identified, and they include a diverse set of proteins with a large variety of functions. This article discusses examples of moonlighting proteins, how one protein structure can perform two different functions, and how the multiple functions can be regulated. In addition to learning more about what our proteins do and how they work together in complex multilayered interaction networks and processes in our bodies, the study of moonlighting proteins can inform future synthetic biology projects in making proteins that perform new functions and new combinations of functions, for example, for synthesising new materials, delivering drugs into cells, and in bioremediation.

A system for detecting high impact-low frequency mutations in primary tumors and metastases

Tumor complexity and intratumor heterogeneity contribute to subclonal diversity. Despite advances in next-generation sequencing (NGS) and bioinformatics, detecting rare mutations in primary tumors and metastases contributing to subclonal diversity is a challenge for precision genomics. Here, in order to identify rare mutations, we adapted a recently described epithelial reprograming assay for short-term propagation of epithelial cells from primary and metastatic tumors. Using this approach, we expanded minor clones and obtained epithelial cell-specific DNA/RNA for quantitative NGS analysis. Comparative Ampliseq Comprehensive Cancer Panel sequence analyses were performed on DNA from unprocessed breast tumor and tumor cells propagated from the same tumor. We identified previously uncharacterized mutations present only in the cultured tumor cells, a subset of which has been reported in brain metastatic but not primary breast tumors. In addition, whole-genome sequencing identified mutations enriched in liver metastases of various cancers, including Notch pathway mutations/chromosomal inversions in 5/5 liver metastases, irrespective of cancer types. Mutations/rearrangements in FHIT, involved in purine metabolism, were detected in 4/5 liver metastases, and the same four liver metastases shared mutations in 32 genes, including mutations of different HLA-DR family members affecting OX40 signaling pathway, which could impact the immune response to metastatic cells. Pathway analyses of all mutated genes in liver metastases showed aberrant tumor necrosis factor and transforming growth factor signaling in metastatic cells. Epigenetic regulators including KMT2C/MLL3 and ARID1B, which are mutated in >50% of hepatocellular carcinomas, were also mutated in liver metastases. Thus, irrespective of cancer types, organ-specific metastases may share common genomic aberrations. Since recent studies show independent evolution of primary tumors and metastases and in most cases mutation burden is higher in metastases than primary tumors, the method described here may allow early detection of subclonal somatic alterations associated with metastatic progression and potentially identify therapeutically actionable, metastasis-specific genomic aberrations.

Oocyte Activation and Fertilisation: Crucial Contributors from the Sperm and Oocyte

This chapter intends to summarise the importance of sperm- and oocyte-derived factors in the processes of sperm-oocyte binding and oocyte activation. First, we describe the initial interaction between sperm and the zona pellucida, with particular regard to acrosome exocytosis. We then describe how sperm and oocyte membranes fuse, with special reference to the discovery of the sperm protein IZUMO1 and its interaction with the oocyte membrane receptor JUNO. We then focus specifically upon oocyte activation, the fundamental process by which the oocyte is alleviated from metaphase II arrest by a sperm-soluble factor. The identity of this sperm factor has been the source of much debate recently, although mounting evidence, from several different laboratories, provides strong support for phospholipase C ζ (PLCζ), a sperm-specific phospholipase. Herein, we discuss the evidence in support of PLCζ and evaluate the potential role of other candidate proteins, such as post-acrosomal WW-binding domain protein (PAWP/WBP2NL). Since the cascade of downstream events triggered by the sperm-borne oocyte activation factor heavily relies upon specialised cellular machinery within the oocyte, we also discuss the critical role of oocyte-borne factors, such as the inositol trisphosphate receptor (IP₃R), protein kinase C (PKC), store-operated calcium entry (SOCE) and calcium/calmodulin-dependent protein kinase II (CaMKII), during the process of oocyte activation. In order to place the implications of these various factors and processes into a clinical context, we proceed to describe their potential association with oocyte activation failure and discuss how clinical techniques such as the in vitro maturation of oocytes may affect oocyte activation ability. Finally, we contemplate the role of artificial oocyte activating agents in the clinical rescue of oocyte activation deficiency and discuss options for more endogenous alternatives.

Post-translational processing targets functionally diverse proteins in Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae is a genome-reduced, cell wall-less, bacterial pathogen with a predicted coding capacity of less than 700 proteins and is one of the smallest self-replicating pathogens. The cell surface of M. hyopneumoniae is extensively modified by processing events that target the P97 and P102 adhesin families. Here, we present analyses of the proteome of M. hyopneumoniae-type strain J using protein-centric approaches (one- and two-dimensional GeLC–MS/MS) that enabled us to focus on global processing events in this species. While these approaches only identified 52% of the predicted proteome (347 proteins), our analyses identified 35 surface-associated proteins with widely divergent functions that were targets of unusual endoproteolytic processing events, including cell adhesins, lipoproteins and proteins with canonical functions in the cytosol that moonlight on the cell surface. Affinity chromatography assays that separately used heparin, fibronectin, actin and host epithelial cell surface proteins as bait recovered cleavage products derived from these processed proteins, suggesting these fragments interact directly with the bait proteins and display previously unrecognized adhesive functions. We hypothesize that protein processing is underestimated as a post-translational modification in genome-reduced bacteria and prokaryotes more broadly, and represents an important mechanism for creating cell surface protein diversity.

Transcriptome profiling analysis of rare minnow (Gobiocypris rarus) gills after waterborne cadmium exposure

Rare minnow (Gobiocypris rarus) is a widely used experimental fish in risk assessments of aquatic pollutants in China. Cadmium (Cd) is one of the most toxic heavy metals in the world; however, few studies have used fish gills, a multi-functional organ. In this study, we characterized the differential expression of adult female rare minnow gills after sub-chronic waterborne Cd (75μg/L CdCl2) exposure for 35d. A total of 452 genes (209 up-regulated and 243 down-regulated) were identified by gene expression profiling using RNA-Seq before and after treatment. Of these differentially expressed genes, 75, 21, and 54 differentially expressed genes are related to ion transport, oxidation-reduction processes, and the immune response, respectively. The results of GO and KEGG enrichment analyses, together with the altered transcript levels of major histocompatibility complex (MHC) class I and class II molecules and the significant increases in the levels of serum tumor necrosis factor α (TNF-α), interleukin 1β (IL1β) and nuclear factor-κB (NF-κB), indicated a disruption of the immune system, particularly the induction of inflammation and autoimmunity. The significant down-regulation of coagulation factor XIII A1 polypeptide (F13A1), tripartite motif-containing protein 21 (TRIM21), and Golgi-associated plant pathogenesis-related protein (GAPr) during both acute (≤96h) and sub-chronic (35d) waterborne Cd exposure, as well as their dosage dependence, suggested that these three genes could be used as sensitive biomarkers for aquatic Cd risk assessment.

Antisperm protein targets in azoospermia men

BACKGROUND:

The number of couples that meet the definition of infertility at reproductive ages is increasing worldwide. One of the most known conditions of infertility in males is azoospermia, defined as complete absence of spermatozoa in the semen. Azoospermia manifests in two forms, namely obstructive and non-obstructive azoospermia. Although the presence of antisperm antibody (ASA) has been reported in 88% of the patients with obstructive azoospermia (OA), interestingly, there is no data regarding ASA targets in OA individuals.

AIM:

The present study aimed to identify sperm antibody targets in a group of OA men.

SETTINGS AND DESIGN:

The present study was carried out on 27 OA infertile men and 27 healthy fertile age-matched males as cases and controls, respectively.

SUBJECTS AND METHODS:

The sperm proteome was separated using two-dimensional gel electrophoresis technique, transferred onto the polyvinylidene fluoride membrane, and blotted with the sera of a group of OA men. Then, it was compared with the membranes blotted with the sera of a group of healthy fertile men. Matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI TOF/TOF) mass spectrometry was used to identify the different blotted spots and finally the results of the mass analysis were confirmed using reverse transcriptase polymerase chain reaction method.

RESULTS:

The results indicated that OA patients might produce antibody against two sperm proteins, Tektin-2 and triose phosphate isomerase. Moreover, the expressions of the two targeted proteins were confirmed at RNA level.

CONCLUSIONS:

The findings of the present study revealed two functionally important sperm proteins as antibody targets in azoospermic men.

Moonlighting proteins in sperm-egg interactions

Sperm-egg interaction is a highly species-specific step during the fertilization process. The first steps consist of recognition between proteins on the sperm head and zona pellucida (ZP) glycoproteins, the acellular coat that protects the oocyte. We aimed to determine which sperm head proteins interact with ZP2, ZP3 and ZP4 in humans. Two approaches were combined to identify these proteins: immunoblotting human spermatozoa targeted by antisperm antibodies (ASAs) from infertile men and far-Western blotting of human sperm proteins overlaid by each of the human recombinant ZP (hrZP) proteins. We used a proteomic approach with 2D electrophoretic separation of sperm protein revealed using either ASAs eluted from infertile patients or recombinant human ZP glycoproteins expressed in Chinese-hamster ovary (CHO) cells. Only spots highlighted by both methods were analysed by MALDI-MS/MS for identification. We identified proteins already described in human spermatozoa, but implicated in different metabolic pathways such as glycolytic enzymes [phosphokinase type 3 (PK3), enolase 1 (ENO1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), aldolase A (ALDOA) and triose phosphate isomerase (TPI)], detoxification enzymes [GST Mu (GSTM) and phospholipid hydroperoxide glutathione peroxidase (PHGPx) 4], ion channels [voltage-dependent anion channel 2 (VDAC2)] or structural proteins (outer dense fibre 2). Several proteins were localized on the sperm head by indirect immunofluorescence, and their interaction with ZP proteins was confirmed by co-precipitation experiments. These results confirm the complexity of the sperm-ZP recognition process in humans with the implication of different proteins interacting with the main three ZP glycoproteins. The multiple roles of these proteins suggest that they are multifaceted or moonlighting proteins.

Alteration of sperm protein profile induced by cigarette smoking

Cigarette smoking is associated with lower semen quality, but how cigarette smoking changes the semen quality remains unclear. The aim of this study was to screen the differentially expressed proteins in the sperm of mice with daily exposure to cigarette smoke. The 2D gel electrophoresis (2DE) and mass spectrometry (MS) analyses results showed that the mouse sperm protein profile was altered by cigarette smoking. And 22 of the most abundant proteins that correspond to differentially expressed spots in 2DE gels of the sperm samples were identified. These proteins were classified into different groups based on their functions, such as energy metabolism, reproduction, and structural molecules. Furthermore, the 2DE and MS results of five proteins (Aldoa, ATP5a1, Gpx4, Cs, and Spatc1) were validated by western blot analysis and reverse transcriptase-polymerase chain reaction. Results showed that except Spatc1 the other four proteins showed statistically significant different protein levels between the smoking group and the control group (P < 0.05). The expressions of three genes (Aldoa, Gpx4, and Spatc1) were significantly different (P < 0.05) at transcription level between the smoking group and the control group. In addition, five proteins (Aldoa, ATP5a1, Spatc1, Cs, and Gpx4) in human sperm samples from 30 male smokers and 30 non-smokers were detected by western blot analysis. Two proteins (Aldoa and Cs) that are associated with energy production were found to be significantly altered, suggesting that these proteins may be potential diagnostic markers for evaluation of smoking risk in sperm. Further study of these proteins may provide insight into the pathogenic mechanisms underlying infertility in smoking persons.

Study on the zona pellucida 4 (ZP4) gene sequence and its expression in the ovaries of patients with polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common endocrine disorder of unknown pathology, involving reproductive and metabolic abnormalities. Oocyte-specific genes are a group of genes expressed exclusively in ovarian tissue; therefore, they can play an important role in ovarian pathologies such as PCOS. The zona pellucida 4 (ZP4) gene encodes glycoprotein which is a part of the extracellular matrix of oocyte.

MATERIALS AND METHODS

We analyzed 87 patients with PCOS, which were divided into four groups depending on their phenotype. In each patient, we performed profound clinical and biochemical analysis, including the measurement of serum androgens. The ovarian tissue samples were used to perform a real-time polymerase chain reaction and immunohistochemical staining using anti-ZP4 monoclonal antibodies. The ZP4 gene was sequenced from peripheral lymphocytes.

RESULTS

The expression of ZP4 was present in early antral follicles and was stronger in mature follicles. The subgroup of patients with eumenorrhea and without hyperandrogenism presented the highest expression of ZP4 in ovarian tissue. In one case, we found a mutation of the ZP4 gene. No correlations were found between the ZP4 expression level and biochemical or clinical indices.

CONCLUSIONS

Data from this and animal studies suggest a possible relationship between androgens and ZP4 expression. ZP4 expression is highest among patients with PCOS and a regular cycle, and this is a consequence of the presence of mature follicles in this group. In some patients with PCOS and infertility, ZP4 mutation can be found.

Bovine sperm plasma membrane proteomics through biotinylation and subcellular enrichment

A significant proportion of mammalian fertilization is mediated through the proteomic composition of the sperm surface. These protein constituents can present as biomarkers to control and regulate breeding of agricultural animals. Previous studies have addressed the bovine sperm cell apical plasma membrane (PM) proteome with nitrogen cavitation enrichment. Alternative workflows would enable to expand the compositional data more globally around the entire sperm's surface. We used a cell surface biotin-labeling in combination with differential centrifugation to enrich sperm surface proteins. Using nano-LC MS/MS, 338 proteins were confidently identified in the PM-enriched proteome. Functional categories of sperm-egg interaction, protein turnover, metabolism as well as molecular transport, spermatogenesis, and signal transduction were represented by proteins with high quantitative signal in our study. A highly significant degree of enrichment was found for transmembrane and PM-targeted proteins. Among them, we also report proteins previously not described on bovine sperm (CPQ, CD58, CKLF, CPVL, GLB1L3, and LPCAT2B) of which CPQ and CPVL cell surface localization was further validated. A descriptive overview of the bovine sperm PM integral and peripheral proteins is provided to complement future studies on animal reproduction and its relation to sperm cell surface. All MS data have been deposited in the ProteomeXchange with identifier PXD001096 (http://proteomecentral.proteomexchange.org/dataset/PXD001096).