Systematic mapping and functional analysis of a family of human epididymal secretory sperm-located proteins

Bringing proteomics to bear on male fertility: key lessons

INTRODUCTION

Male infertility is a major public health concern globally. Proteomics has revolutionized our comprehension of male fertility by identifying potential infertility biomarkers and reproductive defects. Studies comparing sperm proteome with other male reproductive tissues have the potential to refine fertility diagnostics and guide infertility treatment development.

AREAS COVERED

This review encapsulates literature using proteomic approaches to progress male reproductive biology. Our search methodology included systematic searches of databases such as PubMed, Scopus, and Web of Science for articles up to 2023. Keywords used included 'male fertility proteomics,' 'spermatozoa proteome,' 'testis proteomics,' 'epididymal proteomics,' and 'non-hormonal male contraception.' Inclusion criteria were robust experimental design, significant contributions to male fertility, and novel use of proteomic technologies.

EXPERT OPINION

Expert analysis shows a shift from traditional research to an integrative approach that clarifies male reproductive health's molecular intricacies. A gap exists between proteomic discoveries and clinical application. The expert opinions consolidated here not only navigate the current findings but also chart the future proteomic applications for scientific and clinical breakthroughs. We underscore the need for continued investment in proteomic research - both in the technological and collaborative arenas - to further unravel the secrets of male fertility, which will be central to resolving fertility issues in the coming era.

A Narrative Review Discussing Vasectomy-Related Impact upon the Status of Oxidative Stress and Inflammation Biomarkers and Semen Microbiota

Background: Male contraceptive approaches besides tubal sterilization involve vasectomy and represent the method of choice among midlife men in developing countries thanks to many advantages. However, the subsidiary consequences of this intervention are insufficiently explored since the involved mechanisms may offer insight into a much more complex picture. Methods: Thus, in this manuscript, we aimed to reunite all available data by searching three separate academic database(s) (PubMed, Web of Knowledge, and Scopus) published in the past two decades by covering the interval 2000–2023 and using a predefined set of keywords and strings involving “oxidative stress” (OS), “inflammation”, and “semen microbiota” in combination with “humans”, “rats”, and “mice”. Results: By following all evidence that fits in the pre-, post-, and vasectomy reversal (VR) stages, we identified a total of n = 210 studies from which only n = 21 were finally included following two procedures of eligibility evaluation. Conclusions: The topic surrounding this intricate landscape has created debate since the current evidence is contradictory, limited, or does not exist. Starting from this consideration, we argue that further research is mandatory to decipher how a vasectomy might disturb 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.

Targeted Analysis of HSP70 Isoforms in Human Spermatozoa in the Context of Capacitation and Motility

HSP70s constitute a family of chaperones, some isoforms of which appear to play a role in sperm function. Notably, global proteomic studies analyzing proteins deregulated in asthenozoospermia, a main cause of male infertility characterized by low sperm motility, showed the dysregulation of some HSP70 isoforms. However, to date, no clear trend has been established since the variations in the abundance of HSP70 isoforms differed between studies. The HSPA2 isoform has been reported to play a key role in fertilization, but its dysregulation and possible relocation during capacitation, a maturation process making the spermatozoon capable of fertilizing an oocyte, is debated in the literature. The aim of the present study was to investigate the fate of all sperm HSP70 isoforms during capacitation and in relation to sperm motility. Using Multiple-Reaction Monitoring (MRM) mass spectrometry, we showed that the relative abundance of all detected isoforms was stable between non-capacitated and capacitated spermatozoa. Immunofluorescence using two different antibodies also demonstrated the stability of HSP70 isoform localization during capacitation. We also investigated spermatozoa purified from 20 sperm samples displaying various levels of total and progressive sperm motility. We showed that the abundance of HSP70 isoforms is not correlated to sperm total or progressive motility.

Distribution of the Novel RFRP-3/receptors system in the epididymis of the seasonal desert rodent, Gerbillus tarabuli, during sexual activity

RFamide-related peptide (RFRP-3), the Mammalian ortholog of the Avian gonadotropin-inhibitory hormone (GnIH), is a novel neuropeptide known for its inhibitory regulatory effect on reproduction in various mammalian species. However, a stimulatory action has been reported. This paper aims to: i) study the histology of the epididymis (caput) of Gerbillus tarabuli during the breeding period; and ii) to determine the distribution of the "RFRP-3/receptors system" in the epididymis (caput) of this desert rodent during the active season, and thus, to inspect its potential local interfering in sperm maturation. For that, immunohistochemistry was performed to detect the epididymal immunolocalizations of the three molecules, RFRP-3, GPR147, and GPR74. This is the first report of the epididymis histology in Gerbillus tarabuli, as it is the first evidence of the existence of the RFRP-3/Receptor system in the same organ of the same species. During the breeding season, moderate immunostaining of the RFRP-3/receptors system was present in the caput epididymis' epithelial parts (basal and principal cells) and spermatozoa. In contrast, these three molecules were absent in the peritubular and muscle coat's myoid cells and of the interstitial part of the caput epididymis. The results suggest that the epididymis is a potential source of RFRP-3 in the desert Rodent, Gerbillus tarabuli, which may function as a paracrine and/or autocrine factor affecting the main epididymis' function: sperm maturation.

A cross-species approach for the identification of Drosophila male sterility genes

Male reproduction encompasses many essential cellular processes and interactions. As a focal point for these events, sperm offer opportunities for advancing our understanding of sexual reproduction at multiple levels during development. Using male sterility genes identified in human, mouse, and fruit fly databases as a starting point, 103 Drosophila melanogaster genes were screened for their association with male sterility by tissue-specific RNAi knockdown and CRISPR/Cas9-mediated mutagenesis. This list included 56 genes associated with male infertility in the human databases, but not found in the Drosophila database, resulting in the discovery of 63 new genes associated with male fertility in Drosophila. The phenotypes identified were categorized into six distinct classes affecting sperm development. Interestingly, the second largest class (Class VI) caused sterility despite apparently normal testis and sperm morphology suggesting that these proteins may have functions in the mature sperm following spermatogenesis. We focused on one such gene, Rack 1, and found that it plays an important role in two developmental periods, in early germline cells or germline stem cells and in spermatogenic cells or sperm. Taken together, many genes are yet to be identified and their role in male reproduction, especially after ejaculation, remains to be elucidated in Drosophila, where a wealth of data from human and other model organisms would be useful.

Male reproductive systems of Macaca mulatta: Gonadal development, spermatogenesis and applications in spermatogonia stem cell transplantation

Rhesus macaque (Macaca mulatta) is widely applied in animal model construction of infertility, spermatogonia stem cell transplantation and male reproductive diseases. In this review, we describe the seasonal changes of the reproductive system in rhesus macaques, the regular pattern of spermatogenesis and spermatozoa maturation, and the differentiation of spermatogonia and spermatocytes. The duration of the M. mulatta spermatogenesis is approximately 10 days and seminiferous epithelium cycles mainly consist of 12 stages, which provide a suitable model for reproductive studies in non-human primates. Here, we summarize the features of gonadal development and sperm maturation in the rhesus monkeys, which provide important information in the studies of reproductive biology. Rhesus macaque is an excellent animal model in spermatogonia stem cell transplantation. We discuss the applications and progresses of assisted reproductive technologies in sperm liquefaction, semen cryopreservation and spermatogonia stem cell transplantation of rhesus macaques. Besides, we sort out recent proteomic analyses of male reproductive systems and semen samples in rhesus macaques. This review mainly focuses on male reproductive biology and application studies using M. mulatta, which would promote the development of new therapeutic interventions on assisted reproduction and reproductive disease studies in the future.

Vitamin E can promote spermatogenesis by regulating the expression of proteins associated with the plasma membranes and protamine biosynthesis

Vitamin E is generally believed to promote the production of ovine sperm mainly through its antioxidant effect. Our previous studies have shown that some non-antioxidant genes may also be key in mediating this process. The objective of this study was to identify key candidate proteins that were differentially expressed in response to a treatment with Vitamin E. Prepubertal ovine testicular cells were isolated and divided into two groups. They were either treated with 800 μM Vitamin E (based on our previous results) or used as a non-treated control. After 24 h, all the cells were harvested for proteomic analysis. We found 115 differentially expressed proteins, 4 of which were up-regulated and 111 were down-regulated. A GO term enrichment analysis identified 127 Biological Process, 63 Cell Component and 26 Molecular Function terms that were enriched. Within those terms, 13, 11 and 26 terms were significantly enriched, respectively. Terms related to membrane and enzyme activity including the inner acrosomal membrane, signal peptidase complex, cysteine-type endopeptidase activity, etc., were also markedly enriched, while none of the KEGG pathways were enriched. We found that many of the differentially expressed proteins, such as CD46 (membrane cofactor protein), FLNA (Filamin A), DYSF (Dysferlin), IFT20 (Intraflagellar transport 20), SPCS1 (Signal peptidase complex subunit 1) and SPCS3 (Signal peptidase complex subunit 3) were related to the acrosomal and plasma membranes. A parallel reaction monitoring (PRM) analysis verified that Vitamin E improved spermatogenesis by regulating the expression of FLNA, SPCS3, YBX3 and RARS, proteins that are associated with the plasma membranes and protamine biosynthesis of the spermatozoa.

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.

Quantitative Proteomic Analysis of Human Seminal Plasma from Normozoospermic and Asthenozoospermic Individuals

Seminal plasma is a complex mixture of secretions from various glands in the male genital tract. Compared to sperm cells, it contains important proteins that are both directly and indirectly associated with sperm motility. Here, we constructed quantitative proteomes of human seminal plasma from three normozoospermic and asthenozoospermic individuals. A total of 524 proteins were identified, and 366 of them were found to be quantified in all six samples. We first investigated the absolute expression features of these proteins and found that the variations of protein identification among different samples and other published datasets were mainly due to some lowly expressed proteins. By integration of various proteomic datasets and bioinformatics databases, we comprehensively annotated the biological functions, physiological originations, and disease associations of these proteins. We found that our dataset could benefit the studies of both male infertility and other male diseases. Finally, based on the relative expression values determined by chemical labeling, we identified a total of 29 differentially expressed proteins, which could be used as candidate targets for studying the molecular bases of sperm motility or developing precise diagnostic biomarkers of asthenozoospermia. We further successfully verified the expression trends of four representative proteins by Western blotting. Compared to a previous dataset based on label-free quantification, our results showed that most of the important proteins could be identified in the sample collected only once for each individual, providing the bases for personalized examination of seminal plasma proteins in clinic.

A Human Lectin Microarray for Sperm Surface Glycosylation Analysis

Glycosylation is one of the most abundant and functionally important protein post-translational modifications. As such, technology for efficient glycosylation analysis is in high demand. Lectin microarrays are a powerful tool for such investigations and have been successfully applied for a variety of glycobiological studies. However, most of the current lectin microarrays are primarily constructed from plant lectins, which are not well suited for studies of human glycosylation because of the extreme complexity of human glycans. Herein, we constructed a human lectin microarray with 60 human lectin and lectin-like proteins. All of the lectins and lectin-like proteins were purified from yeast, and most showed binding to human glycans. To demonstrate the applicability of the human lectin microarray, human sperm were probed on the microarray and strong bindings were observed for several lectins, including galectin-1, 7, 8, GalNAc-T6, and ERGIC-53 (LMAN1). These bindings were validated by flow cytometry and fluorescence immunostaining. Further, mass spectrometry analysis showed that galectin-1 binds several membrane-associated proteins including heat shock protein 90. Finally, functional assays showed that binding of galectin-8 could significantly enhance the acrosome reaction within human sperms. To our knowledge, this is the first construction of a human lectin microarray, and we anticipate it will find wide use for a range of human or mammalian studies, alone or in combination with plant lectin microarrays.

Association of polymorphisms in PATE1 gene with idiopathic asthenozoospermia in Sichuan, China

PURPOSE

Idiopathic Asthenozoospermia (AZS) is a common symptom of male infertility described as reduced forward motility or absence of sperm motility. The PATE1 is generally expressed in male genital tract and related to sperm development, maturation and fertilization. However, the single nucleotide polymorphisms (SNPs) of the PATE1 gene which contribute to AZS were still unknown. For this reason, the possible association between the single nucleotide polymorphisms of the PATE1 gene and idiopathic asthenozoospermia was investigated in this research.

METHODS

108 idiopathic asthenozoospermia were screened by karyotype analysis, detection of Y microdeletions and mutations in 5 other genes from 140 clinical AZS. The sequence analyses of the PATE1 gene were conducted in 108 idiopathic asthenozoospermia and 106 fertile men with normospermic parameters in Sichuan, China.

RESULTS

In this study, a total 108 patients without chromosomal abnormalities, Y microdeletions and selected genes mutation were confirmed. The 1423G (odds ratio [OR] 1.939, 95% confidence interval [CI] 1.320-2.848, P=0.001) was found to be increased significantly in idiopathic asthenozoospermic patients compared with their fertile counterparts. This mutation substitutes a highly conserved glutamic to arginine at the position of the 47th amino acid which was shown to be located on the flank of the pleated sheet domain in PATE1 protein by the 3D model given by the Protein Model Portal (PMP). Moreover, PolyPhen-2 analysis predicted that this variant was "probably damaging".

CONCLUSIONS

These results suggested that PATE1 variant (A1423G) was probably one of the high risk genetic factors for idiopathic asthenozoospermia among males in Sichuan, China.

The human epididymis: its function in sperm maturation

BACKGROUND

Spermatozoa acquire their fertilizing ability and forward motility properties during epididymal transit. Our knowledge of gamete physiology is based on studies conducted in laboratory and domestic species; our knowledge of these processes in humans is limited. Medical indications for assisted reproductive technologies (ART) have progressed to include male infertility. Surgical procedures allow collection of spermatozoa from all along the human excurrent ducts, and the former have been used with some success in reproductive medicine. This has raised questions over the role of the epididymis in human sperm physiology.

OBJECTIVE AND RATIONALE

To reanalyze what we now know about epididymal physiology in humans and to assess the relevance of laboratory animal models for understanding human physiology and the pathophysiology of the epididymis.

SEARCH METHODS

A systematic bibliographic search of PubMed for articles published in English before May 2015 was carried out using the search terms 'epididymis' and 'sperm maturation'. Literature on the consequences of vasectomy on the epididymis was also searched.

OUTCOMES

Whereas the proximal epididymis is almost exclusively occupied by efferent ducts, the sperm reservoir capacity is poorly developed in humans. At the molecular level, the human transcriptome and proteome show some segment specificity; conflicting results persist with regard to secretome variation along the tubule. The number of genes regulated along the excurrent ducts in men is lower when compared to rodent species, but remains significant. It is challenging to reconcile biochemical and physiological studies with clinical data obtained from men undergoing reanastomosis of the vas deferens at different points along the excurrent duct. We propose that vasectomy/vasovasostomy is a model to understand the consequences of obstruction on epididymis function in humans.

WIDER IMPLICATIONS

Despite the scarcity of biological material available, the interspecies variability of the male reproductive tract urges us to use modern molecular and cellular biology tools to better understand human epididymis physiology in order to apply ART in a more responsible manner.

Epididymal research: more warp than weft?

From a review of some aspects of epididymal structure, function and research done largely in my research area over the last 50 years, I conclude that more is known than is understood of sperm maturation and storage in the epididymis. Highly qualified technicians have not always applied sophisticated modern techniques in well-considered experiments to physiologically relevant and properly-prepared samples, so that our understanding of the biological problem of the nature of the epididymal epithelial influence on maturing epididymal spermatozoa has not kept pace with the outpouring of data generated, much of which is difficult to interpret. We stand at a crossroads of where to aim our limited resources and personnel: should we continue new technology-led studies in many directions, backtrack to test hypotheses and fill in gaps in our knowledge, or consider more biological directions to our research?

Proteome profiling of the sperm maturation milieu in the rhesus monkey (Macaca mulatta) epididymis

The mammalian spermatozoon acquires its fertilising potential during transit through the epididymis, where it interacts with epididymal luminal fluid proteins (the sperm maturation milieu). In order to highlight the epididymal-specific function of the rhesus monkey (Macaca mulatta) in sperm maturation, two-dimensional gel electrophoresis of epididymal luminal fluid proteins was followed by identification by Matrix-Assisted Laser Desorption/ Ionization Time of Flight Mass Spectrometry (MALDI-TOF/MS) or MALDI-TOF/TOF and revealed over five hundred spots, comprising 198 non-redundant proteins. Some mass spectrometric data were confirmed by western blotting identification. Some common epididymal fluid proteins were identified, such as clusterin, α-1-antitrypsin, malate dehydrogenase, L-lactate dehydrogenase B, α-1-acid glycoprotein 1 and α-mannosidase. More than 7% of all proteins were anti-oxidative, which might control oxidative stress within the male tract. When compared with bull and human epididymal luminal fluid proteins, those in the rhesus monkey had more overlap with the human, which provides evidence of a close evolutionary relationship between the rhesus monkey and man. This study provides new proteomic information on possible rhesus monkey epididymal functions and novel potential biomarkers for the noninvasive assessment of male fertility.

In-depth Proteomic mapping of mouse (Mus musculus) epididymal constructive basis for sperm maturation

BACKGROUND

The mouse epididymis performs an essential role in sperm maturation, but global protein expression data in mouse epididymis are still lacking. Here, we reported the first in-depth gel-based profiling of mouse epididymis proteome and established a 2-DE map.

RESULTS

A total of 832 protein spots were detected in the reproducible gels, and 625 spots corresponding to 355 unique protein entries have been successfully identified by MALDI-TOF-MS. The confidence of proteome data was validated by Western blot. Functional annotations showed that these proteins were mainly related to general metabolism, antioxidant and structural molecule activity. Immunohistochemistry disclosed two structural proteins (myosin regulatory light polypeptide 9 and alpha-2 type I collagen) continuously expressed in the myoid cell since postpartum.

CONCLUSION

This study provides a first-draft reference map of the mouse epididymis proteome, which will greatly expand the knowledge of the epididymal structural basis and contribute to the better understanding of those proteins in the process of mouse epididymal sperm maturation.

Influence of ejaculation frequency on seminal parameters

BACKGROUND

Several factors have been shown to influence semen parameters, one of which is sexual abstinence; a clinical criteria included in the semen evaluation to provide maximum sperm quality. The aim of the present study was to assess the effect of a daily ejaculation frequency on conventional and functional semen parameters.

METHODS

Semen samples were collected daily over a period of two weeks of which every second sample per person was processed and analyzed according to the World Health Organization guidelines. Furthermore, mitochondrial function, intracellular reactive oxygen species production and sperm DNA fragmentation were evaluated by flow cytometry.

RESULTS

Total sperm count and seminal volume per ejaculation declined and remained decreased for the duration of the daily ejaculation period. However, conventional parameters such as sperm concentration, motility, progressive motility, morphology, vitality and functional parameters such as sperm plasma membrane integrity, mitochondrial membrane potential and DNA fragmentation was not significantly affected and remained similar to the initial measurement throughout the daily ejaculation period. Despite intra- and inter individual variations, the average values of the basic semen parameters remained above the WHO (2010) reference values throughout the daily ejaculation period. Interestingly, a decreasing trend in intracellular ROS production was observed, although statistically not significant.

CONCLUSIONS

The study shows that an extended 2 week period of daily ejaculation does not have major clinical effects on conventional and functional seminal parameters.

In‑depth mapping of human testicular and epididymal proteins and their functional association with spermatozoa

The mammalian testis and epididymis are responsible for spermatozoa production and maturation, which contributes to male fertility. Predominantly expressed proteins in the testis and epididymis were suggested to be involved in the key functions or pathways in spermatogenesis and sperm maturation. To further investigate these proteins and their associations with sperm, large protein profiles of human testis and epididymis were mapped. Predominantly-expressed testicular (173) and epididymal (244) secreted proteins were further screened and functionally characterized. Differential expression levels of solute carrier family 2 (facilitated glucose transporter), member 3, solute carrier family 25 (carnitine/acylcarnitine translocase), member 20, WAP-type four-disulfide core domain protein 8 and prostate and testis expressed 1 were validated using western blot and immunohistochemical analyses. The results may provide novel insight into the understanding of testicular and epididymal physiology and function, and facilitate sperm maturation research.

Amyloid precursor protein interaction network in human testis: sentinel proteins for male reproduction

BACKGROUND

Amyloid precursor protein (APP) is widely recognized for playing a central role in Alzheimer's disease pathogenesis. Although APP is expressed in several tissues outside the human central nervous system, the functions of APP and its family members in other tissues are still poorly understood. APP is involved in several biological functions which might be potentially important for male fertility, such as cell adhesion, cell motility, signaling, and apoptosis. Furthermore, APP superfamily members are known to be associated with fertility. Knowledge on the protein networks of APP in human testis and spermatozoa will shed light on the function of APP in the male reproductive system.

RESULTS

We performed a Yeast Two-Hybrid screen and a database search to study the interaction network of APP in human testis and sperm. To gain insights into the role of APP superfamily members in fertility, the study was extended to APP-like protein 2 (APLP2). We analyzed several topological properties of the APP interaction network and the biological and physiological properties of the proteins in the APP interaction network were also specified by gene ontologyand pathways analyses. We classified significant features related to the human male reproduction for the APP interacting proteins and identified modules of proteins with similar functional roles which may show cooperative behavior for male fertility.

CONCLUSIONS

The present work provides the first report on the APP interactome in human testis. Our approach allowed the identification of novel interactions and recognition of key APP interacting proteins for male reproduction, particularly in sperm-oocyte interaction.

Proteomic analysis of meningiomas

Meningiomas represent one-third of all primary brain tumors and cause 35,000 new cases each year. Because of this high incidence, we sought to determine if there are proteomic differences between meningiomas and neighboring tissues. Two-dimensional gel electrophoresis and mass spectrometry were used to detect differentially expressed proteins in tumor samples, using arachnoid tissue as a control. Western blot analysis was used to validate the identified candidate proteins. We obtained quantitative data on 112 proteins, 17 of which were down-regulated and 26 of which were up-regulated in meningiomas relative to normal arachnoid tissue. Our analysis showed that the expression of galectin-3, vimentin, and endoplasmin was decreased significantly in meningiomas. The expression of 40S ribosomal protein S12, glutathione S-transferase P, and hypoxia up-regulated protein 1 was increased significantly (P < 0.05). The six above-mentioned differentially expressed proteins might be closely involved with the development of meningiomas. The results of this study provide basic insights into the proteome of meningiomas and provide a preliminary database for further research to enhance understanding of meningioma development.

Location and characterization of GAPDS in male reproduction

Sperm-specific glyceraldehyde 3-phosphate dehydrogenase (GAPDS) originates from spermatogenic cells of the human testis. A strong staining of GAPDS was detected in epididymal epithelium, especially in principal cells and basal cells of the epithelium. GAPDS also bound to the fibrous sheet of the sperm tail and inhibited the motility and penetration ability of sperms. The rat model showed that at postnatal day 28 the spermatogenic cells began to express GAPDS protein. By day 60 its expression decreased in spermatogenic cells while it increased in Sertoli cells. After sexual maturation (120 days) GAPDS protein was expressed in both Sertoli cells and elongated sperms. The expression of GAPDS gradually increased with age in the epididymis.

Comparative analysis of human reproductive proteomes identifies candidate proteins of sperm maturation

Male reproductive proteomes provide basis for studying gene products and its involvement or regulation in sperm physiology. Here, a comparative study between these proteomes was performed to find potential proteins and functions associated with human sperm maturation. Seven reproductive proteomes associated with human sperm physiology were integrated. Gene ontology analysis were performed using DAVID and Panther tools to determine enriched functions. Total of 270 proteins overlapped between epididymal, prostatic milieu and sperm proteome were thought to be candidate proteins involved in sperm maturation, and they showed enriched functions of proteasomal protein catabolic process and protein folding. 34 epididymal milieu proteins and 274 prostatic milieu proteins were contributed to the composition of seminal fluids proteome. Literatures have confirmed the involvements in sperm maturation of many of these proteins The spatial expressions of 24 epididymal milieu proteins involved in chaperone and antioxidant activity were authenticated by real-time RT-PCR. These proteins may serve as candidate molecules for future studies of sperm maturation and male infertility.

Differential proteomic analysis of pathway biomarkers in human breast cancer by integrated bioinformatics

The aim of this study was to better understand the altered functional modules in breast cancer at pathway and network levels. An integrated bioinformatics analysis of differentially expressed proteins in human breast cancer was performed. Breast cancer protein profiles were constructed by data mining proteins in literature and public databases, including 1031 proteins with 153 secretory and 69 cell surface proteins. An experimental investigation was performed by two-dimensional electrophoresis, and 4 proteins were further validated by western blotting. Enriched bioinformatics functions were clustered. This study may be used as a reference in further studies to help identify the underlying biological interactions associated with breast cancer and discover potential cancer targets.

Isolation and proteomic characterization of the mouse sperm acrosomal matrix

A critical step during fertilization is the sperm acrosome reaction in which the acrosome releases its contents allowing the spermatozoa to penetrate the egg investments. The sperm acrosomal contents are composed of both soluble material and an insoluble material called the acrosomal matrix (AM). The AM is thought to provide a stable structure from which associated proteins are differentially released during fertilization. Because of its important role during fertilization, efforts have been put toward isolating the AM for biochemical study and to date AM have been isolated from hamster, guinea pig, and bull spermatozoa. However, attempts to isolate AM from mouse spermatozoa, the species in which fertilization is well-studied, have been unsuccessful possibly because of the small size of the mouse sperm acrosome and/or its fusiform shape. Herein we describe a procedure for the isolation of the AM from caput and cauda mouse epididymal spermatozoa. We further carried out a proteomic analysis of the isolated AM from both sperm populations and identified 501 new proteins previously not detected by proteomics in mouse spermatozoa. A comparison of the AM proteome from caput and cauda spermatozoa showed that the AM undergoes maturational changes during epididymal transit similar to other sperm domains. Together, our studies suggest the AM to be a dynamic and functional structure carrying out a variety of biological processes as implied by the presence of a diverse group of proteins including proteases, chaperones, hydrolases, transporters, enzyme modulators, transferases, cytoskeletal proteins, and others.

Why are epididymal tumours so rare?

Epididymal tumour incidence is at most 0.03% of all male cancers. It is an enigma why the human epididymis does not often succumb to cancer, when it expresses markers of stem and cancer cells, and constitutively expresses oncogenes, pro-proliferative and pro-angiogenic factors that allow tumour cells to escape immunosurveillance in cancer-prone tissues. The privileged position of the human epididymis in evading tumourigenicity is reflected in transgenic mouse models in which induction of tumours in other organs is not accompanied by epididymal neoplasia. The epididymis appears to: (i) prevent tumour initiation (it probably lacks stem cells and has strong anti-oxidative mechanisms, active tumour suppressors and inactive oncogene products); (ii) foster tumour monitoring and destruction (by strong immuno-surveillance and -eradication, and cellular senescence); (iii) avert proliferation and angiogenesis (with persistent tight junctions, the presence of anti-angiogenic factors and misplaced pro-angiogenic factors), which together (iv) promote dormancy and restrict dividing cells to hyperplasia. Epididymal cells may be rendered non-responsive to oncogenic stimuli by the constitutive expression of factors generally inducible in tumours, and resistant to the normal epididymal environment, which mimics that of a tumour niche promoting tumour growth. The threshold for tumour initiation may thus be higher in the epididymis than in other organs. Several anti-tumour mechanisms are those that maintain spermatozoa quiescent and immunologically silent, so the low incidence of cancer in the epididymis may be a consequence of its role in sperm maturation and storage. Understanding these mechanisms may throw light on cancer prevention and therapy in general.

Presence of histone H3 acetylated at lysine 9 in male germ cells and its distribution pattern in the genome of human spermatozoa

During spermatogenesis, approximately 85% of histones are replaced by protamines. The remaining histones have been proposed to carry essential marks for the establishment of epigenetic information in the offspring. The aim of the present study was to analyse the expression pattern of histone H3 acetylated at lysine 9 (H3K9ac) during normal and impaired spermatogenesis and the binding pattern of H3K9ac to selected genes within ejaculates. Testicular biopsies, as well as semen samples, were used for immunohistochemistry. Chromatin immunoprecipitation was performed with ejaculated sperm chromatin. HeLa cells and prostate tissue served as controls. Binding of selected genes was evaluated by semiquantitative and real-time polymerase chain reaction. Immunohistochemistry of H3K9ac demonstrated positive signals in spermatogonia, spermatocytes, elongating spermatids and ejaculated spermatozoa of fertile and infertile men. H3K9ac was associated with gene promoters (CRAT, G6PD, MCF2L), exons (SOX2, GAPDH, STK11IP, FLNA, PLXNA3, SH3GLB2, CTSD) and intergenic regions (TH) in fertile men and revealed shifts of the distribution pattern in ejaculated spermatozoa of infertile men. In conclusion, H3K9ac is present in male germ cells and may play a role during the development of human spermatozoa. In addition, H3K9ac is associated with specific regions of the sperm genome defining an epigenetic code that may influence gene expression directly after fertilisation.

Sperm surface changes and physiological consequences induced by sperm handling and storage

Spermatozoa interact with their immediate environment and this contact remodels the sperm surface in preparation for fertilisation. These fundamental membrane changes will be critically covered in this review with special emphasis on the very specific surface destabilisation event, capacitation. This process involves very subtle and intricate modifications of the sperm membrane including removal of suppression (decapacitation) factors and changes in the lateral organisation of the proteins and lipids of the sperm surface. Processing of sperm for assisted reproduction (storage, sex-sorting, etc.) subjects spermatozoa to numerous stressors, and it is possible that this processing overrides such delicate processes resulting in sperm instability and cell damage. To improve sperm quality, novel mechanisms must be used to stabilise the sperm surface during handling. In this review, different types of membrane stress are considered, as well as novel surface manipulation methods to improve sperm stability.

Distinctive amino acid composition profiles in salivary proteins of the tick Ixodes scapularis

Bioinformatic analysis of the amino acid composition of proteins of the tick Ixodes scapularis showed that, in comparison to other secreted proteins, salivary proteins in general have higher frequencies of polar residues and lower frequencies of the non-polar residues leucine and valine. Computer prediction of linear B-cell epitopes showed that polar residues were associated with the presence of high-quality epitopes and that tick salivary proteins included significantly more proteins with predicted high-quality epitopes than did other secreted proteins. The results provided no evidence that salivary proteins as a whole have evolved characteristics minimizing their antigenicity to the vertebrate host. Certain salivary proteins may indeed have evolved low antigenicity, but the I. scapularis sialome include at least some apparently antigenic proteins that might be tested experimentally to determine whether they would be suitable candidates for anti-tick vaccines.

Preliminary proteomic analysis of human serum from patients with laryngeal carcinoma

To better evaluate the serum protein alterations in patients with laryngeal carcinoma during surgical treatment process, a comparative proteomic analysis of human serum from patients with laryngeal carcinoma between pre- and post-operation group was performed using two-dimensional gel electrophoresis, in combination with matrix-assisted laser desorption ionization time-of-flight mass spectrometry and database searching. Statistical analysis indicated that 16 gel spots corresponding to 12 proteins altered their expression significantly between the two groups of patients with laryngeal carcinoma. Of these 12 proteins, 6 proteins were up-regulated in the pre-operation group. The subsequent Western blot confirmed the results of proteome analysis. Measurement of MDA and SOD levels in serum combining with bioinformatics analysis indicated the potential roles of the oxidant stress and immune response as target in monitoring and treating laryngeal carcinoma. The study provides new insight into the laryngeal carcinoma development and treatment, and the identified proteins are warranted to be further studied.

A new analysis of testicular proteins through integrative bioinformatics

The testis is the male gonad responsible for spermatogenesis and steroidogenesis. Much remains to be known about the control of these events. In this study, we performed a new bioinformatic enrichment analysis of human testicular proteins selected from a protein database. Integrated function and pathway analyses were performed by Database for Annotation, Visualization and Integrated Discovery and Ingenuity Pathway Analysis programmes, and significant features were found to be clustered. Protein membrane organization and gene density on chromosomes were analyzed and discussed. The analysis could provide a basis for the understanding of testicular physiology and function, and facilitating biological interpretation of testicular functions in a network context.

Mapping of the human testicular proteome and its relationship with that of the epididymis and spermatozoa

The testis produces male gametes in the germinal epithelium through the development of spermatogonia and spermatocytes into spermatids and immature spermatozoa with the support of Sertoli cells. The flow of spermatozoa into the epididymis is aided by testicular secretions. In the epididymal lumen, spermatozoa and testicular secretions combine with epididymal secretions that promote sperm maturation and storage. We refer to the combined secretions in the epididymis as the sperm-milieu. With two-dimensional-PAGE matrix-assisted laser desorption ionization time-of-flight MS analysis of healthy testes from fertile accident victims, 725 unique proteins were identified from 1920 two-dimensional-gel spots, and a corresponding antibody library was established. This revealed the presence of 240 proteins in the sperm-milieu by Western blotting and the localization of 167 proteins in mature spermatozoa by ICC. These proteins, and those from the epididymal proteome (Li et al. 2010), form the proteomes of the sperm-milieu and the spermatozoa, comprising 525 and 319 proteins, respectively. Individual mapping of the 319 sperm-located proteins to various testicular cell types by immunohistochemistry suggested that 47% were intrinsic sperm proteins (from their presence in spermatids) and 23% were extrinsic sperm proteins, originating from the epididymis and acquired during maturation (from their absence from the germinal epithelium and presence in the epididymal tissue and sperm-milieu). Whereas 408 of 525 proteins in the sperm-milieu proteome were previously identified as abundant epididymal proteins, the remaining 22%, detected by the use of new testicular antibodies, were more likely to be minor proteins common to the testicular proteome, rather than proteins of testicular origin added to spermatozoa during maturation in the epididymis. The characterization of the sperm-milieu proteome and testicular mapping of the sperm-located proteins presented here provide the molecular basis for further studies on the production and maturation of spermatozoa. This could be the basis of development of diagnostic markers and therapeutic targets for infertility or targets for male contraception.