Delivering value from sperm proteomics for fertility

Quantitative proteomics analysis reveals the key proteins related to semen quality in Niangya yaks

BACKGROUND

Proteins related to sperm motility and sperm morphology have an important impact on sperm function such as metabolism, motility and fertilisation etc. An understanding of the key proteins related to semen quality in Niangya yaks would help to provide support for breeding. However, the key proteins that affect semen quality in Niangya yaks remain unclear.

METHODS

Herein, we applied tandem mass tag (TMT) labeling and liquid chromatography-tandem mass spectrometry (LC‒MS/MS) to analyze the expression levels of sperm proteins in groups of high- and low-quality semen from Niangya yaks. And fifteen differentially expressed proteins (DEPs) were randomly selected for expression level validation by parallel reaction monitoring (PRM).

RESULTS

Of the 2,092 quantified proteins, 280 were identified as DEPs in the high-quality group versus the low-quality group. Gene Ontology (GO) analysis revealed that in terms of biological pathways, the DEPs were mainly involved in metabolic processes, cell transformation processes, and single organism metabolic processes. In terms of cell composition, the DEPs were mainly located in the cell membrane, organelle, molecular complex. In terms of molecular functions, the most abundant functions of the DEPs were catalytic activity, binding activity, transport activity, and enzyme regulation activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the DEPs were mainly involved in the cytokine and cytokine receptor interaction, notch signaling pathway, lysine biosynthesis, renal function-related protein and proteasome pathway. From protein-protein interaction (PPI) analysis of DEPs involved in important pathways, 6 related proteins affecting the semen quality of Niangya yaks were identified. And the results of the PRM and TMT analysis were consistent.

CONCLUSIONS

The differential sperm proteomic analysis of high- and low-quality semen from Niangya yaks, revealed 6 proteins (PSMC5, PSMD8, PSMB3, HSP90AA1, UGP2 and HSPB1), were mainly concentrated in energy production and metabolism, might play important roles in semen quality, which could serve as candidates for the selection and breeding of Niangya yaks.

Sperm aminopeptidase N identifies the potential for high-quality blastocysts and viable embryos in oocyte-donation cycles

STUDY QUESTION

Is there a relationship between human sperm aminopeptidase N (APN) and embryo development in humans?

SUMMARY ANSWER

Human sperm APN could possibly become a new molecular biomarker for identifying the potential for high-quality and usable embryos.

WHAT IS KNOWN ALREADY

The diagnosis of male fertility is one of the major concerns of reproductive medicine. Approximately 30-40% of men with otherwise normal fertility parameters are still unable to achieve pregnancy. The predictive clinical value of semen analysis to identify fertile or infertile males is limited; therefore, new diagnostic methodologies for sperm are urgently required. Sperm APN may be a relevant molecular marker due to its high concentration in sperm cells and its important roles in sperm physiology, such as its functions in motility, acrosome reaction and embryo development.

STUDY DESIGN, SIZE, DURATION

This study included 81 couples who underwent oocyte-donation cycles at Clínica IVI Bilbao (Spain), yielding 611 embryos, between September 2014 and July 2015.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study was conducted in an assisted reproduction unit and an academic research laboratory. All the semen samples were examined and classified following World Health Organization guidelines. Spermatozoa were isolated from semen using the discontinuous colloidal silica gradient (45-90%) technique. Embryo quality and development were determined according to the Spanish Association of Reproduction Biology Studies (ASEBIR) criteria. Human sperm APN levels were analyzed by quantitative and semiquantitative flow cytometry.

MAIN RESULTS AND THE ROLE OF CHANCE

The most well-developed and usable blastocysts were associated with low sperm APN levels. Semen samples that had lower APN levels generated more expanded, hatched and usable blastocysts and fewer early, arrested and non-usable blastocysts. The cumulative probability of having well-developed blastocysts increased by 1.38-fold at Day 5 and 1.90-fold at Day 6 of embryo development, and the likelihood of having usable embryos increased by 1.48-fold, when semen samples with low APN levels were used during the ICSI technique.

LIMITATIONS, REASONS FOR CAUTION

The data were obtained from a single fertility clinic. A multicentre study will be required to confirm the results.

WIDER IMPLICATIONS OF THE FINDINGS

Human sperm APN has the potential to become a new molecular biomarker to help identify the potential for high-quality embryos and diagnose male infertility, especially when seminal parameters are close to the threshold values. It could be a crucial tool for couples for whom the number of usable blastocysts is critical for ART success.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Basque Government (GIC15/165) and the University of the Basque Country (UPV/EHU) (EHUA14/17). The authors declare that they have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Integration of Multiplied Omics, a Step Forward in Systematic Dairy Research

Due to their unique multi-gastric digestion system highly adapted for rumination, dairy livestock has complicated physiology different from monogastric animals. However, the microbiome-based mechanism of the digestion system is congenial for biology approaches. Different omics and their integration have been widely applied in the dairy sciences since the previous decade for investigating their physiology, pathology, and the development of feed and management protocols. The rumen microbiome can digest dietary components into utilizable sugars, proteins, and volatile fatty acids, contributing to the energy intake and feed efficiency of dairy animals, which has become one target of the basis for omics applications in dairy science. Rumen, liver, and mammary gland are also frequently targeted in omics because of their crucial impact on dairy animals’ energy metabolism, production performance, and health status. The application of omics has made outstanding contributions to a more profound understanding of the physiology, etiology, and optimizing the management strategy of dairy animals, while the multi-omics method could draw information of different levels and organs together, providing an unprecedented broad scope on traits of dairy animals. This article reviewed recent omics and multi-omics researches on physiology, feeding, and pathology on dairy animals and also performed the potential of multi-omics on systematic dairy research.

(Pro)renin Receptor Is Present in Human Sperm and It Adversely Affects Sperm Fertility Ability

Sperm fertility ability may be modulated by different molecular systems, such as the renin-angiotensin system (RAS). Although renin is one of its most relevant peptides, the presence and role of the (pro)renin receptor (PRR) is completely unknown. We have proved for the first time the existence of PRR and its transcript in human sperm by western blot and RT-PCR. Immunofluorescence studies showed that this receptor is mainly located in the apical region over the acrosome and in the postacrosomal region of the sperm head and along the sperm tail. In addition, this prospective cohort study also proves that semen samples with higher percentages of PRR-positive spermatozoa are associated with poor sperm motility, worse blastocyst development and no-viable blastocysts. Our results provide insight into how PRR play a negative role in sperm physiology that it may condition human embryo quality and development. An in-depth understanding of the role of PRR in sperm fertility can help elucidate its role in male infertility, as well as establish biomarkers for the diagnosis or selection of sperm to use during assisted reproductive techniques.

The Epigenetics of Gametes and Early Embryos and Potential Long-Range Consequences in Livestock Species-Filling in the Picture With Epigenomic Analyses

The epigenome is dynamic and forged by epigenetic mechanisms, such as DNA methylation, histone modifications, chromatin remodeling, and non-coding RNA species. Increasing lines of evidence support the concept that certain acquired traits are derived from environmental exposure during early embryonic and fetal development, i.e., fetal programming, and can even be "memorized" in the germline as epigenetic information and transmitted to future generations. Advances in technology are now driving the global profiling and precise editing of germline and embryonic epigenomes, thereby improving our understanding of epigenetic regulation and inheritance. These achievements open new avenues for the development of technologies or potential management interventions to counteract adverse conditions or improve performance in livestock species. In this article, we review the epigenetic analyses (DNA methylation, histone modification, chromatin remodeling, and non-coding RNAs) of germ cells and embryos in mammalian livestock species (cattle, sheep, goats, and pigs) and the epigenetic determinants of gamete and embryo viability. We also discuss the effects of parental environmental exposures on the epigenetics of gametes and the early embryo, and evidence for transgenerational inheritance in livestock.

Human sperm testicular angiotensin-converting enzyme helps determine human embryo quality

Angiotensin-converting enzyme functions in the male reproductive system, but the extent of its function in reproduction is not fully understood. The primary objective of this work was to investigate the relationship between the testicular isoform of angiotensin-converting enzyme present in human spermatozoa and semen parameters, human embryo quality, and assisted reproduction success. A total of 81 semen samples and 635 embryos from couples undergoing oocyte donation cycles at the IVI Bilbao Clinic were analyzed. Semen parameters, embryos quality, and blastocyst development were examined according to the World Health Organization standards and the Spanish Association of Reproduction Biology Studies criteria. The percentage of testicular angiotensin-converting enzyme-positive spermatozoa and the number of molecules per spermatozoon were analyzed by flow cytometry. Both parameters were inversely correlated with human sperm motility. Higher percentages of testicular angiotensin-converting enzyme-positive spermatozoa together with fewer enzyme molecules per spermatozoon were positively correlated with better embryo quality and development. Our results suggest that embryos with a higher implantation potential come from semen samples with higher percentages of testicular angiotensin-converting enzyme-positive cells and fewer enzyme molecules per spermatozoon. Based on these findings, we propose that testicular angiotensin-converting enzyme could be used to aid embryologists in selecting better semen samples for obtaining high-quality blastocysts during in vitro fertilization procedures.

Comparative Analysis of MicroRNA and mRNA Profiles of Sperm with Different Freeze Tolerance Capacities in Boar (Sus scrofa) and Giant Panda (Ailuropoda melanoleuca)

Post-thawed sperm quality parameters vary across different species after cryopreservation. To date, the molecular mechanism of sperm cryoinjury, freeze-tolerance and other influential factors are largely unknown. In this study, significantly dysregulated microRNAs (miRNAs) and mRNAs in boar and giant panda sperm with different cryo-resistance capacity were evaluated. From the result of miRNA profile of fresh and frozen-thawed giant panda sperm, a total of 899 mature, novel miRNAs were identified, and 284 miRNAs were found to be significantly dysregulated (195 up-regulated and 89 down-regulated). Combined analysis of miRNA profiling of giant panda sperm and our previously published data on boar sperm, 46, 21 and 4 differentially expressed (DE) mRNAs in boar sperm were believed to be related to apoptosis, glycolysis and oxidative phosphorylation, respectively. Meanwhile, 87, 17 and 7 DE mRNAs in giant panda were associated with apoptosis, glycolysis and oxidative phosphorylation, respectively. Gene ontology (GO) analysis of the targets of DE miRNAs showed that they were mainly distributed on membrane related pathway in giant panda sperm, while cell components and cell processes were tied to the targets of DE miRNAs in boar sperm. Finally, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of DE mRNAs indicated that most of these DE mRNAs were distributed in membrane signal transduction-related pathways in giant panda sperm, while those in boar sperm were mainly distributed in the cytokine-cytokine receptor interaction pathway and inflammatory related pathways. In conclusion, although the different freezing extenders and programs were used, the DE miRNAs and mRNAs involved in apoptosis, energy metabolism, olfactory transduction pathway, inflammatory response and cytokine-cytokine interactions, could be the possible molecular mechanism of sperm cryoinjury and freeze tolerance.

Functional insights into the role of seminal plasma proteins on sperm motility of buffalo

The objective of the present study was to describe the proteins from the seminal plasma of buffalo and correlate these proteins with sperm motility. Ejaculates from sixteen Murrah buffalo were used. Semen collection was performed by electroejaculation, and the ejaculate was evaluated by macroscopic (volume) and microscopic analysis (subjective motility and vigor, as well as sperm concentration). After the analysis, the samples were centrifuged (800g for 10 min and 10,000 for 30 min at 4 °C), and the supernatant (seminal plasma) was used to determine total protein concentration by the Bradford method. Based on total protein concentration, an aliquot (50 μg) was taken to conduct protein in-solution digestion for nano-LC-ESI-Q-TOF mass spectrometry analysis. Samples were divided into two groups, minimal (little sperm motility) and greater (typical sperm motility), based on non-hierarchical clustering considering motility and emPAI protein value. The data were analyzed by multivariate statistical analysis using principal component analysis (PCA) and partial analysis of minimum squares discrimination (PLS-DA). Forty-eight proteins were detected in the seminal plasma, and fifteen were common to two groups. There were six proteins that were significantly different between the groups. The main functions of proteins in seminal plasma were catalytic and binding activity. Spermadhesin protein, ribonuclease, 14-3-3 protein zeta/delta and acrosin inhibitor were in greater amounts in seminal plasma from the group with greater sperm motility; prosaposin and peptide YY were in greater amounts in the group with little sperm motility. The proteins detected in the greater motility group were correlated with sperm protection, including protection against oxidative stress, lipid peroxidation, protease inhibition and prevention of premature capacitation and acrosome reaction. In the group with little sperm motility, one of the identified proteins is considered to be an antifertility factor, whereas the function of other identified protein is not definitive. Results from the present study add to the knowledge base about the molecular processes related with sperm motility, and these findings can be used for determining potential markers of semen quality.

Functional SNPs of INCENP Affect Semen Quality by Alternative Splicing Mode and Binding Affinity with the Target Bta-miR-378 in Chinese Holstein Bulls

Inner centromere protein (INCENP) plays an important role in mitosis and meiosis as the main member of chromosomal passenger protein complex (CPC). To investigate the functional markers of the INCENP gene associated with semen quality, the single nucleotide polymorphisms (SNPs) g.19970 A>G and g.34078 T>G were identified and analyzed. The new splice variant INCENP-TV is characterized by the deletion of exon 12. The g.19970 A>G in the exonic splicing enhancer (ESE) motif region results in an aberrant splice variant by constructing two minigene expression vectors using the pSPL3 exon capturing vector and transfecting vectors into MLTC-1 cells. INCENP-TV was more highly expressed than INCENP-reference in adult bull testes. The g.34078 T>G located in the binding region of bta-miR-378 could affect the expression of INCENP, which was verified by luciferase assay. To analyze comprehensively the correlation of SNPs with sperm quality, haplotype combinations constructed by g.19970 A>G and g.34078 T>G, as well as g.-692 C>T and g.-556 G>T reported in our previous studies, were analyzed. The bulls with H1H12 and H2H2 exhibited a higher ejaculate volume than those with H2H10 and H9H12, respectively (P < 0.05). Bulls with H11H11 and H2H10 exhibited higher initial sperm motility than those with H2H2 (P < 0.05). The expression levels of INCENP in bulls with H1H12 and H11H11 were significantly higher than those in bulls with H9H12 (P < 0.05), as determined by qRT-PCR. Findings suggest that g.19970 A>G and g.34078 T>G in INCENP both of which appear to change the molecular and biological characteristics of the mRNA transcribed from the locus may serve as a biomarkers of male bovine fertility by affecting alternative splicing mode and binding affinity with the target bta-miR-378.

Sperm macromolecules associated with bull fertility

Bull fertility, ability of the sperm to fertilize and activate the egg that sustain embryo development, is vitally important for effective and efficient production of cattle. Fertility is a complex trait with low heritability. Despite recent advances in genomic selection and possibility of enormous paternal benefits to profitable cattle production, there exist no reliable tests for evaluating semen quality and predicting bull fertility. This review focuses on sperm macromolecules such as transcripts, proteins and the epigenome, i.e., the functional genome that are associated with bull fertility. Generating new information in these systems is important beyond agriculture because such progress advances the fundamental science of the mammalian male gamete while at the same time introduces biotechnology into livestock production. Sperm macromolecules and epigenome markers associated with bull fertility can be used alone or in combination with the current SNP microarrays to determine sperm quality and to indicate bull fertility.

Differences between high- and low-motility buffalo sperm identified by comparative proteomics

This study was undertaken to investigate differences in protein expression between high- and low-motility sperm of swamp buffalo. The research used two-dimensional gel electrophoresis (2DE) coupled to matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS) to analyse the different proteins. The results showed 18 different expression protein spots between high- and low-motility buffalo sperm; eight of these proteins were up-regulated in low-motility sperm, five were down-regulated, one deleted and four proteins specifically expressed. Finally, four proteins were successfully identified by MS as belonging to three unique proteins; they are outer dense fibre of sperm tails protein 2 (ODF2), ATP synthase subunit alpha (ATP5A1) and succinyl-CoA synthetase subunit beta (SUCLG2). In summary, these results help to develop an understanding of the molecular mechanisms associated with low-motility sperm and provide clues for finding molecular markers associated with sperm motility.

Analysis of the basal chordate Botryllus schlosseri reveals a set of genes associated with fertility

Background

Gonad differentiation is an essential function for all sexually reproducing species, and many aspects of these developmental processes are highly conserved among the metazoa. The colonial ascidian, Botryllus schlosseri is a chordate model organism which offers two unique traits that can be utilized to characterize the genes underlying germline development: a colonial life history and variable fertility. These properties allow individual genotypes to be isolated at different stages of fertility and gene expression can be characterized comprehensively.

Results

Here we characterized the transcriptome of both fertile and infertile colonies throughout blastogenesis (asexual development) using differential expression analysis. We identified genes (as few as 7 and as many as 647) regulating fertility in Botryllus at each stage of blastogenesis. Several of these genes appear to drive gonad maturation, as they are expressed by follicle cells surrounding both testis and oocyte precursors. Spatial and temporal expression of differentially expressed genes was analyzed by in situ hybridization, confirming expression in developing gonads.

Conclusion

We have identified several genes expressed in developing and mature gonads in B. schlosseri. Analysis of genes upregulated in fertile animals suggests a high level of conservation of the mechanisms regulating fertility between basal chordates and vertebrates.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1183) contains supplementary material, which is available to authorized users.

Qualitative and quantitative peptidomic and proteomic approaches to phenotyping chicken semen

Understanding of the avian male gamete biology is essential to improve the conservation of genetic resources and performance in farming. In this study, the chicken semen peptidome/proteome and the molecular phenotype related to sperm quality were investigated. Spermatozoa (SPZ) and corresponding seminal plasma (SP) from 11 males with different fertilizing capacity were analyzed using three quantitative strategies (fluid and intact cells MALDI-MS, SDS-PAGE combined to LC-MS/MS with spectral counting and XIC methods). Individual MALDI profiling in combination with top-down MS allowed to characterize specific profiles per male and to identify 16 biomolecules (e.g.VMO1, AvBD10 and AvBD9 including polymorphism). Qualitative analysis identified 1165 proteins mainly involved in oxidoreduction mechanisms, energy processes, proteolysis and protein localization. Comparative analyses between the most and the least fertile males were performed. The enzymes involved in energy metabolism, respiratory chain or oxido-reduction activity were over-represented in SPZ of the most fertile males. The SP of the most and the least fertile males differed also on many proteins (e.g. ACE, AvBD10 and AvBD9, NEL precursor, acrosin). Thus proteomic is a "phenomic molecular tool" that may help to discriminate avian males on their reproductive capacity. The data have been deposited with ProteomeXchange (identifiers PXD000287 and PXD001254).

BIOLOGICAL SIGNIFICANCE

This peptidomic and proteomic study i) characterized for the first time the semen protein composition of the main domestic avian species (Gallus gallus) by analysis of ejaculated spermatozoa and corresponding seminal plasma; ii) established a characteristic molecular phenotype distinguishing semen and males at an individual level; and iii) proposedthe first evidence of biomarkers related to fertility.

Semen analysis: update on clinical value, current needs and future perspectives

At present, evaluation of male reproductive function consists primarily of routine semen analysis, a collection of conventional microscopic assessments ideally performed following the guidelines set by the World Health Organization. While providing some insight into testicular function, these long-performed tests are limited in the information that they impart; more specifically, they are unable to predict true fertility potential. As a consequence, there is a need for the appraisal and consideration of newer semen parameters that may be more indicative of reproductive success. Although various novel assays have been introduced that broaden the scope of information available to both researcher and clinician, the utility of these tests remains limited due to the lack of standardisation of protocols and the absence of clinically established, dependable reference ranges. As such, it is not surprising that most of these parameters and their associated methods remain recommended for ‘research purposes only’. With the burgeoning ‘omics’ revolution, nanotechnology and the development of new analytical instruments, there is now an opportunity for the identification and measurement of previously unknown features that may prove to be more indicative of each sperm's true functional status and capability. Once optimised, simplified, clinically validated and made more readily accessible, these new approaches hold the promise of forming the fulcrum upon which andrological investigations can enter a new era.

Head and flagella subcompartmental proteomic analysis of human spermatozoa

Subcellular proteomics not only deepens our knowledge of what proteins are present within cells, but also opens our understanding as to where those proteins reside. Given the highly differentiated, cross-linked state of spermatozoa, such studies have proven difficult to perform. In this study we have fractionated spermatozoa into two components, consisting of either the head or flagellar region. Following SDS-PAGE, 1 mm slices were digested and used for LC-MS/MS analysis. In total, 1429 proteins were identified with 721 proteins being exclusively found in the tail and 521 exclusively in the head. Not only is this the largest reported proteomic analysis of human spermatozoa, but also it has provided novel insights into the compartmentalization of proteins, particularly receptors, never previously reported to be present in this cell type.

Proteomic analysis of human spermatozoa proteins with oxidative stress

BACKGROUND

Oxidative stress plays a key role in the etiology of male infertility. Significant alterations in the sperm proteome are associated with poor semen quality. The aim of the present study was to examine if elevated levels of reactive oxygen species cause an alteration in the proteomic profile of spermatozoa.

METHODS

This prospective study consisted of 52 subjects: 32 infertile men and 20 normal donors. Seminal ejaculates were classified as ROS+ or ROS- and evaluated for their proteomic profile. Samples were pooled and subjected to LC-MS/MS analysis through in-solution digestion of proteins for peptide characterization. The expression profile of proteins present in human spermatozoa was examined using proteomic and bioinformatic analysis to elucidate the regulatory pathways of oxidative stress.

RESULTS

Of the 74 proteins identified, 10 proteins with a 2-fold difference were overexpressed and 5 were underexpressed in the ROS+ group; energy metabolism and regulation, carbohydrate metabolic processes such as gluconeogenesis and glycolysis, protein modifications and oxidative stress regulation were some of the metabolic processes affected in ROS+ group.

CONCLUSIONS

We have identified proteins involved in a variety of functions associated with response and management of oxidative stress. In the present study we focused on proteins that showed a high degree of differential expression and thus, have a greater impact on the fertilizing potential of the spermatozoa. While proteomic analyses identified the potential biomarkers, further studies through Western Blot are necessary to validate the biomarker status of the proteins in pathological conditions.

Cell biology solves mysteries of reproduction

Reproduction and fertility have been objects of keen inquiry since the dawn of humanity. Medieval anatomists provided the first accurate depictions of the female reproductive system, and early microscopists were fascinated by the magnified sight of sperm cells. Initial successes were achieved in the in vitro fertilization of frogs and the artificial insemination of dogs. Gamete and embryo research was in the cradle of modern cell biology, providing the first evidence of the multi-cellular composition of living beings and pointing out the importance of chromosomes for heredity. In the 20th century, reproductive research paved the way for the study of the cytoskeleton, cell signaling, and the cell cycle. In the last three decades, the advent of reproductive cell biology has brought us human in vitro fertilization, animal cloning, and human and animal embryonic stem cells. It has contributed to the development of transgenesis, proteomics, genomics, and epigenetics. This Special Issue represents a sample of the various areas of reproductive biology, with emphasis on molecular and cell biological aspects. Advances in spermatology, ovarian function, fertilization, and maternal-fetal interactions are discussed within the framework of fertility and diseases such as endometriosis and diabetes.