Identification of differentially expressed proteins between bull X and Y spermatozoa

Exploring aptamers for targeted enrichment of X sperm in bovine: unraveling selective potential

Nucleic acid aptamers have been used in the past for the development of diagnostic methods against a number of targets such as bacteria, pesticides, cancer cells etc. In the present study, six rounds of Cell-SELEX were performed on a ssDNA aptamer library against X-enriched sperm cells from Sahiwal breed cattle. Sequencing was used to examine the aptamer sequences that shown affinity for sperm carrying the X chromosome in order to find any possible X-sperm-specific sequences. Out of 35 identified sequences, 14 were selected based on bioinformatics analysis like G-Score and Mfold structures. Further validation of their specificity was done via fluorescence microscopy. The interaction of biotinylated-aptamer with sperm was also determined by visualizing the binding of streptavidin coated magnetic beads on the head region of the sperm under bright field microscopy. Finally, a real-time experiment was designed for the validation of X-sperm enrichment by synthesized aptamer sequences. Among the studied sequences, aptamer 29a exhibited a higher affinity for X sperm compared to Y sperm in a mixed population of sperm cells. By using aptamer sequence 29a, we obtained an enrichment of 70% for X chromosome bearing sperm cells.

Proteomic Analysis of Differences in the Freezability of Porcine Sperm Identifies α-Amylase As a Key Protein

To investigate the mechanisms underlying the differences in the freezability of boar semen, Yorkshire boars with freezing-tolerant semen (YT, n = 3), Yorkshire boars with freezing-sensitive semen (YS, n = 3), Landrace boars with freezing-tolerant semen (LT, n = 3), and Landrace boars with freezing-sensitive semen (LS, n = 3) were selected for this study. Their sperm was subjected to protein extraction, followed by data-independent acquisition proteomics and functional bioinformatics analysis. A total of 3042 proteins were identified, of which 2810 were quantified. Some key KEGG pathways were enriched, such as starch and sucrose metabolism, carbohydrate digestion and absorption, mineral absorption, the HIF-1 signaling pathway, and the necroptosis pathways. Through PRM verification, we found that several proteins, such as α-amylase and epididymal sperm-binding protein 1, can be used as molecular markers of the freezing resistance of boar semen. Furthermore, we found that the addition of α-amylase to cryoprotective extender could significantly improve the post-thaw motility and quality of boar semen. In summary, this study revealed some molecular markers and potential molecular pathways contributing to the high or low freezability of boar sperm, identifying α-amylase as a key protein. This study is valuable for optimizing boar semen cryopreservation technology.

The role of CoQ10 in embryonic development

Coenzyme Q10 (CoQ10) is a natural component widely present in the inner membrane of mitochondria. CoQ10 functions as a key cofactor for adenosine triphosphate (ATP) production and exhibits antioxidant properties in vivo. Mitochondria, as the energy supply center of cells, play a crucial role in germ cell maturation and embryonic development, a complicated process of cell division and cellular differentiation that transforms from a single cell (zygote) to a multicellular organism (fetus). Here, we discuss the effects of CoQ10 on oocyte maturation and the important role of CoQ10 in the growth of various organs during different stages of fetal development. These allowed us to gain a deeper understanding of the pathophysiology of embryonic development and the potential role of CoQ10 in improving fertility quality. They also provide a reference for further developing its application in clinical treatments.

A novel regulatory sex-skewing method that inhibits testicular DPY30 expression to increase female rate of dairy goat offspring

The demand for goat milk products has increased exponentially with the growth of the global population. The shortage of dairy products will be addressed extraordinarily by manipulating the female rate of goat offspring to expand the goat population and goat milk yield. No studies have reported bioinformatic analyses of X- and Y-bearing sperm of dairy goats, although this will contribute to exploring novel and applied sex-skewing technologies. Regulatory subunit of the histone methyltransferase complex (DPY30) was determined to be the key differentially expressed protein (DEP) among 15 DEPs identified in the present study. The spatiotemporal expression of DPY30 strongly suggested a functional involvement of the protein in spermatogenesis. DPY30 promoted meiosis via upregulating SYCP3, which played a crucial role in mediating sex ratio skewing in goats. Although DPY30 suppressed the self-renewal of spermatogonia stem cells through AKT/PLZF, DPY30 inhibition in the testis did not induce testicular dysgenesis. Based on the biosafety assessment in mice testes, lentivirus-mediated DPY30 knockdown in bucks' testes increased X-bearing sperm proportion and female kids' rate (22.8 percentage points) without affecting sperm quality, pregnancy rate, and kidding rate. This study provides the first evidence of the DEGs in the sexed sperm of dairy goats. DPY30 inhibition in the testes of bucks increased the female kids' rate without influencing reproductive performance. The present study provides evidence for expanding the female dairy goat population to address the concern of dairy product shortage.

Boar fertility is controlled through systematic changes of mitochondrial protein expression during sperm capacitation

Vigorous activation of mitochondria in spermatozoa during capacitation induces the biological and morphological changes of spermatozoa to acquire fertilizing ability. To in-depth understand the dynamic roles of mitochondrial and male fertility, this study was to identify how the mitochondrial proteins are changed during sperm capacitation and regulate male fertility using boar spermatozoa. The mitochondrial proteins were differentially changed during sperm capacitation according to fertility status, i.e., superior litter size (SL) and normal litter size (NL). Following sperm capacitation, ubiquitin-cytochrome c reductase core protein (UQCRC1) and ATP synthase F1 (ATP5F1) increased in NL, while cytochrome c oxidase subunit 5B (COX5B), and cytochrome c1 (CYC1) proteins decreased. In contrast, only and ubiquinone oxidoreductase core subunit 8 (NDUFS8) protein was increased in SL following capacitation. The protein expression difference value of CYC1, COX5B, and NDUFS8 following sperm capacitation was lower in NL than SL boars. Based on these complicated changes during sperm capacitation, the accuracy for predicting male fertility of NDUFS8 was increased to 87 %. Overall, considering the systematic orchestration of mitochondrial protein expression according to sperm capacitation status, it will be possible to better understand male fertility.

Biochemical Features of X or Y Chromosome-Bearing Spermatozoa for Sperm Sexing

This review presents information on biochemical features of spermatozoa bearing X or Y chromosome, enabling production of a sperm fraction with pre-defined sex chromosome. The almost only technology currently used for such separation (called sexing) is based on the fluorescence-activated cell sorting of sperm depending on DNA content. In addition to the applied aspects, this technology made it possible to analyze properties of the isolated populations of spermatozoa bearing X or Y chromosome. In recent years, existence of the differences between these populations at the transcriptome and proteome level have been reported in a number of studies. It is noteworthy that these differences are primarily related to the energy metabolism and flagellar structural proteins. New methods of sperm enrichment with X or Y chromosome cells are based on the differences in motility between the spermatozoa with different sex chromosomes. Sperm sexing is a part of the widespread protocol of artificial insemination of cows with cryopreserved semen, it allows to increase proportion of the offspring with the required sex. In addition, advances in the separation of X and Y spermatozoa may allow this approach to be applied in clinical practice to avoid sex-linked diseases.

Sorted Bulls' X-Chromosome-Bearing Spermatozoa Show Increased GAPDHS Activity Correlating with Motility

Sperm sexing is a technique for spermatozoa sorting into populations enriched with X- or Y-chromosome-bearing cells and is widely used in the dairy industry. Investigation of the characteristics of sorted semen is of practical interest, because it could contribute to the enhancement of sexed semen fertility characteristics, which are currently lower than those of conventional semen. Comparison of a spermatozoa population enriched with X-chromosome-bearing cells to a mixed population is also intriguing in the context of potential differences that drive the mechanisms of primary sex-ratio determination. In this work, sexed (X spermatozoa) and conventional spermatozoa of Holstein bulls were analyzed for the content and enzymatic activity of GAPDHS, a sperm-specific isoform of glyceraldehyde-3-phosphate dehydrogenase that plays a significant role in the regulation of flagellar activity. No difference in the amount of this glycolysis enzyme per cell was revealed, but, notably, GAPDHS enzymatic activity in the sexed samples was significantly higher. Enzymatic activity among the group of sexed but not conventional sperm samples positively correlated with spermatozoa motility, which indicates the significant role of this enzyme for the sorted cells population.

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.

Mysteries and unsolved problems of mammalian fertilization and related topics

Mammalian fertilization is a fascinating process that leads to the formation of a new individual. Eggs and sperm are complex cells that must meet at the appropriate time and position within the female reproductive tract for successful fertilization. I have been studying various aspects of mammalian fertilization over 60 years. In this review, I discuss many different aspects of mammalian fertilization, some of my laboratory's contribution to the field, and discuss enigmas and mysteries that remain to be solved.

Advancements in mammalian X and Y sperm differences and sex control technology

Mammal sex determination depends on whether the X sperm or Y sperm binds to the oocyte during fertilization. If the X sperm joins in oocyte, the offspring will be female, if the Y sperm fertilizes, the offspring will be male. Livestock sex control technology has tremendous value for livestock breeding as it can increase the proportion of female offspring and improve the efficiency of livestock production. This review discusses the detailed differences between mammalian X and Y sperm with respect to their morphology, size, and motility in the reproductive tract and in in vitro conditions, as well as ’omics analysis results. Moreover, research progress in mammalian sex control technology has been summarized.

Proteomic fertility markers in ram sperm

Precise estimation of ram fertility is important for sheep farming to sustain reproduction efficiency and profitability of production. There, however, is no conventional method to accurately predict ram fertility. The objective of this study, therefore, was to ascertain proteomic profiles of ram sperm having contrasting fertility phenotypes. Mature rams (n = 66) having greater pregnancy rates than average (89.4 ± 7.2%) were assigned into relatively-greater fertility (GF; n = 31; 94.5 ± 2.8%) whereas those with less-than-average pregnancy rates were assigned into a lesser-fertility (LF; n = 25; 83.1 ± 5.73%; P = 0.028) group. Sperm samples from the outlier greatest- and least-fertility rams (n = 6, pregnancy rate; 98.4 ± 1.8% and 76.1 ± 3.9%) were used for proteomics assessments utilizing Label-free LC-MS/MS. A total of 997 proteins were identified, and among these, 840 were shared by both groups, and 57 and 93 were unique to GF and LF, respectively. Furthermore, 190 differentially abundant proteins were identified; the abundance of 124 was larger in GF while 66 was larger in LF rams. The GF ram sperm had 79 GO/pathway terms in ten major biological networks while there were 47 GO/pathway terms in six biological networks in sperm of LF rams. Accordingly, differential abundances of sperm proteins between sperm of GF and LF rams were indicative of functional implications of sperm proteome on male fertility. The results of this study emphasize there are potential protein markers for evaluation of semen quality and estimation of ram sperm fertilizing capacity.

Differential proteomic profile of X- and Y- sorted Sahiwal bull semen

The identification of differential proteins between X- and Y-sperm may be useful for immunological sexing of sperm. Hence, the present study was aimed to compare the protein profile of X- and Y-sorted Sahiwal bull semen using SDS-PAGE and Liquid Chromatography coupled with Mass Spectrometry (Nano LC-MS). Semen sample (n = 6) were categorized into three groups i.e., group I (X-sorted), group II (Y-sorted) and control group (both X- and Y- sperms). SDS PAGE revealed specific proteins of molecular weight between 18 and 24 kDa and between 30 and 37 kDa were present in X-sorted sperms. Also, band corresponding to 25 kDa was specific to Y-sorted sperms. Data obtained from Nano LC/MS is analysed by search engine database i.e., MASCOT and SEQUEST HT. Total, 241 proteins were identified, out of which 113 were differentially expressed between X- and Y-sorted sperms, in which 54 proteins showed at least two unique peptides. Out of 54 proteins, 27 were upregulated in X-sorted sample, 3 were upregulated in Y-sorted sample and 24 were differentially downregulated. Highly upregulated protein in X-sperm viz. Armadillo repeat containing 12 protein, NDC1 transmembrane nucleoporin, β-nerve growth factor, C-type natriuretic peptide, Nucleobindin-2, Phosphoglycerate mutase 2, Calmodulin along with one uncharacterised protein having accession number F1MN9 may have potential to be used as biomarker for separating X and Y sperm.

Bovine semen sexing: Sperm membrane proteomics as candidates for immunological selection of X- and Y-chromosome-bearing sperm

The use of sexed semen in dairy and beef farms ensures the production of animals of the desired sex, resulting in a reduction of costs and an improvement of environmental sustainability. Several methods have been developed over the years, but most of them were abandoned due to their limited efficacy. Currently, the only commercially available method for the separation of X- and Y-chromosome-bearing sperm is fluorescence-activated cell sorting. However, this technique is expensive and has limited usefulness for the industry, considering that it cannot produce doses of sexed semen with the desired number of sperm for artificial insemination. Immunological methods have emerged as an attractive alternative to flow cytometry and proteomic knowledge of X- and Y-sperm could be useful to the development of a new method. In this review, we identify the main applications of sexed semen, describe the existing methods and highlight future research opportunities in the field. We consider that immunological methods, based on sperm cell's surface proteins differentially expressed between X- and Y-sperm, could be an interesting and promising approach to semen sexing.

Differential proteins associated with plasma membrane in X- and/or Y-chromosome bearing spermatozoa in indicus cattle

The differential proteins associated with plasma membrane of spermatozoa are less known, identification of which shall help overcome limitations of currently used methods of sperm sexing, considered as a high priority for livestock sector of many countries. This study has reported plasma membrane proteomics of unsorted spermatozoa and differential expression of plasma membrane-associated proteins between X- and Y-chromosome bearing spermatozoa of indicus cattle (Bos indicus). Isolation of plasma membrane fraction using percoll gradient, relatively a rapid method, from bovine spermatozoa has been reported to enrich isolation of plasma membrane proteins. Significant enrichment for plasma membrane-associated proteins was observed in plasma membrane fraction (p < .05) as compared to the total cell lysate using LC-MS/MS. Furthermore, these experiments were conducted in flow cytometry sorted, sexed-semen samples. Thirteen proteins were identified as differentially abundant between X- and Y-sorted spermatozoa. Among these, two proteins were downregulated in Y-sorted spermatozoa compared to the X-sorted spermatozoa (p < .05), while four and seven proteins could be noted in X- and Y-sorted spermatozoa, respectively. Proteins that are presumed to support sperm capacitation and sperm migration velocity were found to be abundant in Y-sorted spermatozoa while those associated with structural molecule activity were identified as abundant in X-sorted spermatozoa in the present study. Our study provides better insight into the plasma membrane proteomics of spermatozoa of indicus cattle and furnishes data that might aid in design and development of alternate and open technology for sex-sorting of semen.

Enrichment of bovine X-sperm using microfluidic dielectrophoretic chip: A proof-of- concept study

The microfluidic dielectrophoretic (MF-DEP) chip is a new, economical and readily-available technology that might be used to enrich X-sperm for increasing female offspring in dairy farms. In this study, we sought to develop an MF-DEP chip to enrich X bovine sperm. The MF-DEP chip was composed of an electrode attached to a glass slide and a microchannel made from polydimethylsiloxane. Sex-sorted sperm from flow cytometry were used to identify optimal electric field conditions while unsorted sperm were later tested for sorting efficiency. The results show that during dielectrophoresis some sperm attached to the electrode (called positive DEP; pDEP) whereas other moved away from the electrode (called negative DEP; nDEP). X and Y-sperm responded to dielectrophoresis differently depending on various factors such as buffers, voltages, and frequencies. We found that the condition 4 V 1 MHz significantly reduced (P < 0.05) the percentage of Y-sperm to nearly 30 and therefore enriched X-sperm. The sorting efficiency was dependent on buffer, bull, sorting cycle, flow rate, electrical voltage, and frequency. Notably, the best sorting buffer found in this experiment was the conducting buffer, but this buffer significantly reduced sperm viability and motility. Other sperm-friendly buffers, TRIS and mHTF, were also used, but could not enrich X-sperm. In conclusion, this is a proof of concept that the MF-DEP chip can be effectively used to enrich bovine X-sperm. However, more research must be performed particularly to find the best sorting buffer to effectively sex-sort sperm while providing high motility and sperm viability.

The proteomic characterization of ram sperm during cryopreservation analyzed by the two-dimensional electrophoresis coupled with mass spectrometry

The aim of this study was to analyze the effects of the cryopreservation process on the protein profile of ram sperm using two-dimensional electrophoresis (2-DE) coupled with mass spectroscopy. Semen was collected from five rams and cryopreserved in a Tris-based extender supplemented with glycerol and egg yolk as the main cryoprotectants. The fresh and post-thaw sperm total proteins were extracted and purified, followed by the 2-DE. The differential proteins in the stained gel were determined by mass spectrometry. The results indicated that there were 39 differential proteins between fresh sperm and frozen-thawed sperm. Among these proteins, the abundance of 28 proteins in fresh sperm was higher than those in post-thaw sperm (P < 0.05). However, 11 proteins in post-thaw sperm were up-regulated instead. The gene ontology (GO) analysis showed that most of differential proteins were implicated in cellular process, metabolism and regulation of the biological process. The networks of protein-protein interaction indicated a strong interaction among these differential proteins, which may be involved in sperm metabolism, acrosomal function, sperm motility, and reducing ROS level. In conclusion, the cryopreservation process modifies the proteome of ram sperm, which may be directly associated with ram sperm cryodamage, consequently influencing their fertility. Additionally, these differential proteins can be used as biomarkers for evaluation of frozen ram semen quality.

Differences in small noncoding RNAs profile between bull X and Y sperm

The differences in small noncoding RNAs (sncRNAs), including miRNAs, piRNAs, and tRNA-derived fragments (tsRNAs), between X and Y sperm of mammals remain unclear. Here, we employed high-throughput sequencing to systematically compare the sncRNA profiles of X and Y sperm from bulls (n = 3), which may have a wider implication for the whole mammalian class. For the comparison of miRNA profiles, we found that the abundance of bta-miR-652 and bta-miR-378 were significantly higher in X sperm, while nine miRNAs, including bta-miR-204 and bta-miR-3432a, had greater abundance in Y sperm (p < 0.05). qPCR was then used to further validate their abundances. Subsequent functional analysis revealed that their targeted genes in sperm were significantly involved in nucleosome binding and nucleosomal DNA binding. In contrast, their targeted genes in mature oocyte were significantly enriched in 11 catabolic processes, indicating that these differentially abundant miRNAs may trigger a series of catabolic processes for the catabolization of different X and Y sperm components during fertilization. Furthermore, we found that X and Y sperm showed differences in piRNA clusters distributed in the genome as well as piRNA and tsRNA abundance, two tsRNAs (tRNA-Ser-AGA and tRNA-Ser-TGA) had lower abundance in X sperm than Y sperm (p < 0.05). Overall, our work describes the different sncRNA profiles of X and Y sperm in cattle and enhances our understanding of their potential roles in the regulation of sex differences in sperm and early embryonic development.

Proteomic comparison of non-sexed and sexed (X-bearing) cryopreserved bull semen

It is widely recognized that quality of spermatozoa in sexed semen (SS) samples is not as great as for conventional, non-sexed semen (NS). There are differences in qualitative and biochemical variables between spermatozoa in NS and SS. Information, however, is lacking on molecular differences, especially concerning spermatozoa proteomic differences is SS and NS. The objective of this study was to compare commercially available NS and SS bull semen by evaluating sperm quality variables in conjunction with a proteomics approach. Results from flow cytometry and computer-assisted sperm analyses indicated there was less sperm motility, viability, mitochondrial potential and acrosome integrity in sperm from SS. Results from proteomic analysis indicated sperm from NS and SS samples were characterized by different protein profiles. There was identification of 70 sperm proteins that differed in abundance and six protein spots that were different in extent of carbonylation. Sperm from SS had altered structures of enzymes involved in glycolysis, oxidative phosphorylation and maintenance of a constant adenylate energy charge. Furthermore, sperm from SS had alterations of several flagella substructures, especially outer dense fiber proteins, which were less abundant and more carbonylated than in sperm from NS. In sperm of SS, compared with NS, there were differences in abundance of proteins involved in capacitation, acrosome reaction and sperm-egg fusion as well as lesser abundances of sperm surface proteins. Results enable a greater understanding of differences between sperm from NS and SS samples, thereby contributing to development of improved protocols for more effective protection of sexed spermatozoa during processing.

New Biological Insights on X and Y Chromosome-Bearing Spermatozoa

A spermatozoon is a male germ cell capable of fertilizing an oocyte and carries genetic information for determining the sex of the offspring. It comprises autosomes and an X (X spermatozoa) or a Y chromosome (Y spermatozoa). The origin and maturation of both X and Y spermatozoa are the same, however, certain differences may exist. Previous studies proposed a substantial difference between X and Y spermatozoa, however, recent studies suggest negligible or no differences between these spermatozoa with respect to ratio, shape and size, motility and swimming pattern, strength, electric charge, pH, stress response, and aneuploidy. The only difference between X and Y spermatozoa lies in their DNA content. Moreover, recent proteomic and genomic studies have identified a set of proteins and genes that are differentially expressed between X and Y spermatozoa. Therefore, the difference in DNA content might be responsible for the differential expression of certain genes and proteins between these cells. In this review, we have compiled our present knowledge to compare X and Y spermatozoa with respect to their structural, functional, and molecular features. In addition, we have highlighted several areas that could be explored in future studies in this field.

Review on Sperm Sorting Technologies and Sperm Properties toward New Separation Methods via the Interface of Biochemistry and Material Science

Successful fertilization in mammals requires spermatozoa to efficiently traverse the female reproductive tract to meet the egg. This process naturally selects high quality sperm cells for fertilization, but when artificial reproductive technologies are used such as in vitro fertilization, intracytoplasmic sperm injection, or intrauterine insemination, other methods of sperm selection are required. Currently, technology enables sperm sorting based on motility, maturity as defined by zeta potential or hyaluronic acid binding site expression, absence of apoptotic factors, appropriate morphology, and even sex. This review summarizes current knowledge on all known methods of sperm cell sorting, compares their efficiency, and discusses the advantages and limitations of each technique. Scope for further refinement and improvement of current methods are discussed as is the potential to utilize a variety of materials to innovate new methods of sperm separation.

3D imaging of sex-sorted bovine spermatozoon locomotion, head spin and flagellum beating

With the advent of sperm sex sorting methods and computer-aided sperm analysis platforms, comparative 2D motility studies showed that there is no significant difference in the swimming speeds of X-sorted and Y-sorted sperm cells, clarifying earlier misconceptions. However, other differences in their swimming dynamics might have been undetectable as conventional optical microscopes are limited in revealing the complete 3D motion of free-swimming sperm cells, due to poor depth resolution and the trade-off between field-of-view and spatial resolution. Using a dual-view on-chip holographic microscope, we acquired the full 3D locomotion of 235X-sorted and 289 Y-sorted bovine sperms, precisely revealing their 3D translational head motion and the angular velocity of their head spin as well as the 3D flagellar motion. Our results confirmed that various motility parameters remain similar between X- and Y-sorted sperm populations; however, we found out that there is a statistically significant difference in Y-sorted bovine sperms' preference for helix-shaped 3D swimming trajectories, also exhibiting an increased linearity compared to X-sorted sperms. Further research on e.g., the differences in the kinematic response of X-sorted and Y-sorted sperm cells to the surrounding chemicals and ions might shed more light on the origins of these results.

Proteomic profile of sex-sorted bull sperm evaluated by SWATH-MS analysis

The identification of distinct proteins present on the membrane of spermatozoa with X and Y chromosomes allows the development of immuno-sexing techniques. The aim of this study, therefore, was to use mass spectrometry to analyze the protein profile of sperm previously categorized using flow cytometry into X or Y-bearing semen pools. Sex-sorted sperm samples (n = 6 X and n = 6 Y) were used. Proteins were extracted and analyzed by mass spectrometry using data independent acquisition (DIA). The data were searched against taxonomy Bos taurus in the Swiss Prot database. In total, 459 protein groups were identified. Of these, eight proteins were in differential abundances between the X- and Y-bearing sperm population. Among the major proteinsdetected, EF-hand domain-containing protein 1, a protein involved in embryonic development, is more abundant in Y-bearing spermatozoa. In addition, proteins FUN14, domain-containing protein 2, NADH dehydrogenase [ubiquinone] iron-sulfur protein 7 mitochondrial, cytochrome C oxidase subunit 2, acetyl -CoA carboxylase type beta were more abundant in X-bearing sperm. In conclusion, there were differences in abundance of proteins between X- and Y-bearing bull spermatozoa. This fact, may contribute to future studies related to sperm physiology and possibility development of immuno-sexing techniques.

Identification of differentially expressed proteins in testicular semen of sex-reversed female (XX) and normal male (XY) rainbow trout

Masculinized females, named sex-reversed females (SRF), have a male phenotype but retain the female genotype (XX) and all spermatozoa produced in their testes carry the X chromosome. Masculinization of females leads to incomplete testicular development and the production of lower-quality semen. The mechanism of masculinization is unknown at present. Therefore, the aim of our study was to identify differentially abundant proteins in testicular semen of normal males and SRF using a difference in-gel electrophoresis approach. Masculinization seemed to not lead to significant changes in the testicular seminal plasma proteome, but did have an impact on the proteome of SRF and normal male sperm. We identified 26 proteins enriched ( < 0.05) in testicular male spermatozoa compared to SRF. A total of 28 proteins were also found to be differentially expressed ( < 0.05) in testicular SRF sperm in comparison to normal males. Bioinformatic analysis highlighted pathways associated with energy production for normal male spermatozoa and pathways related to protein remodeling for SRF sperm. Normal male spermatozoa seemed to be equipped with proteins participating in diverse metabolic pathways, focusing on producing the energy required for sperm movement. On the other hand, SRF spermatozoa were characterized by the enhanced expression of proteins associated with cytoskeletal structures and those related to remodeling, which could indicate that spermatogenesis and spermiogenesis are not fully accomplished. These results can be the basis for further research on the molecular mechanisms of masculinization and toward the development of a method for separating X and Y fish sperm.

The bovine sex-determining region Y (Sry) gene and its mRNA transcript are present in Y sperm but not X sperm of bulls

The aims of this study were to establish whether the sex-determining region Y gene and its mRNA transcript are present in the Y sperm and X sperm of bulls and, if present, determine their cellular localization. Semen was collected from three bulls and sorted by flow cytometry into X- and Y-chromosome populations. Reverse transcription-polymerase chain reaction (RT-PCR) was used to determine Sry mRNA expression in X sperm and Y sperm. The presence and localization of Sry DNA and RNA were investigated by fluorescence in situ hybridization (FISH). RT-PCR detected a single Sry transcript of 142 bp in Y sperm but not in X sperm. In Y sperm, the FISH-positive rates for Sry DNA and Sry RNA did not differ significantly from the re-analyzed Y sperm purity. In further experiments, there were no significant differences between the FISH-positive rate for Sry RNA and the re-analyzed Y sperm purity for X-sorted, Y-sorted, or unsorted sperm. In conclusion, FISH analysis revealed that Sry transcripts are present at the edges of the sperm heads of Y sperm but are absent from X sperm.

Flow cytometric sex sorting affects CD4 membrane distribution and binding of exogenous DNA on bovine sperm cells

Bovine sex-sorted sperm have been commercialized and successfully used for the production of transgenic embryos of the desired sex through the sperm-mediated gene transfer (SMGT) technique. However, sex-sorted sperm show a reduced ability to internalize exogenous DNA. The interaction between sperm cells and the exogenous DNA has been reported in other species to be a CD4-like molecule-dependent process. The flow cytometry-based sex-sorting process subjects the spermatozoa to different stresses causing changes in the cell membrane. The aim of this study was to elucidate the relationship between the redistribution of CD4-like molecules and binding of exogenous DNA to sex-sorted bovine sperm. In the first set of experiments, the membrane phospholipid disorder and the redistribution of the CD4 were evaluated. The second set of experiments was conducted to investigate the effect of CD4 redistribution on the mechanism of binding of exogenous DNA to sperm cells and the efficiency of lipofection in sex-sorted bovine sperm. Sex-sorting procedure increased the membrane phospholipid disorder and induced the redistribution of CD4-like molecules. Both X-sorted and Y-sorted sperm had decreased DNA bound to membrane in comparison with the unsorted sperm; however, the binding of the exogenous DNA was significantly increased with the addition of liposomes. Moreover, we demonstrated that the number of sperm-bound exogenous DNA was decreased when these cells were preincubated with anti-bovine CD4 monoclonal antibody, supporting our hypothesis that CD4-like molecules indeed play a crucial role in the process of exogenous DNA/bovine sperm cells interaction.

An immunological approach of sperm sexing and different methods for identification of X- and Y-chromosome bearing sperm

Separation of X- and Y-chromosome bearing sperm has been practiced for selection of desired sex of offspring to increase the profit in livestock industries. At present, fluorescence-activated cell sorter is the only successful method for separation of X- and Y-chromosome bearing sperm. This technology is based on the differences in DNA content between these two types of sperm and has been commercialized for bovine sperm. However, this technology still has problems in terms of high economic cost, sperm damage, and lower pregnancy rates compared to unsorted semen. Therefore, an inexpensive, convenient, and non-invasive approach for sperm sexing would be of benefit to agricultural sector. Within this perspective, immunological sperm sexing method is one of the attractive choices to separate X- and Y-chromosome bearing sperm. This article reviews the current knowledge about immunological approaches, viz., H-Y antigen, sex-specific antigens, and differentially expressed proteins for sperm sexing. Moreover, this review also highlighted the different methods for identification of X- and Y-sperm.

Proteomic identification of cryostress in epididymal spermatozoa

Background

Cryopreservation of epididymal spermatozoa is important in cases in which it is not possible to collect semen using normal methods, as the sudden death of an animal or a catastrophic injury. However, the freezing and thawing processes cause stress to spermatozoa, including cold shock, osmotic damage, and ice crystal formation, thereby reducing sperm quality. We assessed the motility (%), motion kinematics, capacitation status, and viability of spermatozoa using computer-assisted sperm analysis and Hoechst 33258/chlortetracycline fluorescence staining. Moreover, we identified proteins associated with cryostress using a proteomic approach and performed western blotting to validate two-dimensional electrophoresis (2-DE) results using two commercial antibodies.

Results

Cryopreservation reduced viability (%), motility (%), straight-line velocity (VSL), average path velocity (VAP), amplitude of lateral head displacement (ALH), and capacitated spermatozoa, whereas straightness (STR) and the acrosome reaction increased after cryopreservation (P < 0.05). Nine proteins were differentially expressed (two proteins decreased and seven increased) (>3 fold, P < 0.05) before and after cryopreservation. The proteins differentially expressed following cryopreservation are putatively related to several signaling pathways, including the ephrinR-actin pathway, the ROS metabolism pathway, actin cytoskeleton assembly, actin cytoskeleton regulation, and the guanylate cyclase pathway.

Conclusion

The results of the current study provide information on epididymal sperm proteome dynamics and possible protein markers of cryo-stress during cryopreservation. This information will further the basic understanding of cryopreservation and aid future studies aiming to identify the mechanism of cryostress responses.

Effect of sex-sorting and cryopreservation on the post-thaw sperm quality of Iberian red deer spermatozoa

This study investigated the effect of sex-sorting and cryopreservation on post-thaw characteristics and fertility of red deer (Cervus elaphus) sperm for the first time. Semen was collected by electroejaculation from 10 mature stags during the breeding season, and each ejaculate split into four experimental groups: Bulk sorted spermatozoa, sorted but not sexed (BSS); sorted high purity X-spermatozoa (XSS); sorted high purity Y-spermatozoa (YSS); and, control non-sorted spermatozoa (NS). Following, all samples were frozen over liquid nitrogen. Two straws per stag and sample type were analyzed immediately post-thaw and following a 2-h incubation period at 37 °C. Post-thaw total motility (TM) as assessed by CASA was not different (P < 0.05) among NS, BSS and YSS sperm. For XSS, post-thaw TM was lower (39%, P < 0.05) than that for NS (54%) or BSS (50%), but similar (P > 0.05) to that of YSS (47%) sperm. The percentage of apoptotic spermatozoa as assessed by PI/YO-PRO-1 and flow cytometry analysis, was higher (17%, P ≤ 0.05) for XSS sperm than NS (12%), BSS (13%) and YSS (14%) sperm. Following incubation there were no differences (P > 0.05) in TM or percent apoptosis among treatments. Post-thaw chromatin stability calculated as the DNA fragmentation index (%DFI) was similar among treatments; following incubation %DFI increased in all except YSS, which displayed the lowest value (P < 0.05). Artificial insemination of synchronized hinds yielded 44, 52 and 62% delivery rates for YSS, NS and standard frozen-thawed sperm, respectively (P < 0.05). Notably, 93 and 55% of fawns born were males for the YSS and NS spermatozoa, respectively (P < 0.05). In summary, Y-sorted sperm displayed acceptable post-thaw sperm evaluation parameters and the expected offspring sex ratio. More studies are needed to understand the source of sperm damage that may compromise the fertility of Y-sorted red deer sperm.

Sperm proteome and reproductive technologies in mammals

Sperm is highly differentiated cell that can be easily obtained and purified. Mature sperm is considered to be transcriptionally and translationally silent and incapable of protein synthesis. Recently, a large number of proteins have been identified in sperm from different species by using the proteomic approaches. Clinically, sperm proteins can be used as markers for male infertility due to different protein profiles identified in sperm from fertile and infertile male animals. Recent evidences have shown that the conditions of sperm preservation in vitro can also change the sperm protein profiles. This paper reviews the recent scientific publications available to address sperm proteome and their relationship with sperm cryopreservation, capacitation, fertilization, and separation of X and Y sperm. Future directions in the application of sperm proteomics to develop or optimize reproductive technologies in mammals are also discussed.

Addition of Cryoprotectant Significantly Alters the Epididymal Sperm Proteome

Although cryopreservation has been developed and optimized over the past decades, it causes various stresses, including cold shock, osmotic stress, and ice crystal formation, thereby reducing fertility. During cryopreservation, addition of cryoprotective agent (CPA) is crucial for protecting spermatozoa from freezing damage. However, the intrinsic toxicity and osmotic stress induced by CPA cause damage to spermatozoa. To identify the effects of CPA addition during cryopreservation, we assessed the motility (%), motion kinematics, capacitation status, and viability of epididymal spermatozoa using computer-assisted sperm analysis and Hoechst 33258/chlortetracycline fluorescence staining. Moreover, the effects of CPA addition were also demonstrated at the proteome level using two-dimensional electrophoresis. Our results demonstrated that CPA addition significantly reduced sperm motility (%), curvilinear velocity, viability (%), and non-capacitated spermatozoa, whereas straightness and acrosome-reacted spermatozoa increased significantly (p < 0.05). Ten proteins were differentially expressed (two decreased and eight increased) (>3 fold, p < 0.05) after CPA, whereas NADH dehydrogenase flavoprotein 2, f-actin-capping protein subunit beta, superoxide dismutase 2, and outer dense fiber protein 2 were associated with several important signaling pathways (p < 0.05). The present study provides a mechanistic basis for specific cryostresses and potential markers of CPA-induced stress. Therefore, these might provide information about the development of safe biomaterials for cryopreservation and basic ground for sperm cryopreservation.

X and Y chromosome-bearing spermatozoa are equally able to uptake and internalize exogenous DNA by sperm-mediated gene transfer in swine

Since proteomic differences between male X/Y chromosome-bearing gametes have recently been described, a question has been raised: could these differences be responsible for different behavior between X and Y chromosome-bearing spermatozoa during the binding and internalization of exogenous DNA in the swine species? In order to investigate this hypothesis, our group studied the process of the uptake and internalization of exogenous DNA in X and Y chromosome-bearing sperm sub-populations. No significant differences were found between sperm types in both the uptake and internalization of exogenous DNA. The quantity of internalized exogenous DNA was significantly lower than that of the uptaken DNA. In conclusion, our results showed that X and Y chromosomes-bearing spermatozoa have the same binding capacity and internalization of DNA, and the proteomic differences between them do not seem to interfere with these complex processes.

Identification and characterization of genes differentially expressed in X and Y sperm using suppression subtractive hybridization and cDNA microarray

Differential expression of genes leads to variations in the phenotypes of X and Y sperm, although some differentially expressed gene products are shared through intercellular bridges. Genes differentially expressed in bovine X and Y sperm were identified by a combination of suppression subtractive hybridization (SSH), cDNA microarray, and sequence-homology analysis. Microarray data and Significance Analysis of Microarrays software were used to identify 31 differentially expressed genes, only four of which were previously identified. These genes are involved in fundamental life processes of mature sperm, and may be associated with the differences between X and Y sperm since 27 versus 4 were upregulated in X versus Y sperm, respectively. The levels of expression of seven genes-including the known genes UTY, DPH3, CYTB, and ISCU, and the unknown genes X + Y contig 41, X + Y contig 18, and Y + X contig 16-were validated by quantitative real-time PCR, and some genes were clearly differentially expressed by X and Y sperm, despite the presence of intercellular bridges among spermatids. These results provide a theoretical basis for research on gene expression during sperm development, as well as on sex control at the level of sperm.

The battle of the sexes starts in the oviduct: modulation of oviductal transcriptome by X and Y-bearing spermatozoa

BACKGROUND

Sex allocation of offspring in mammals is usually considered as a matter of chance, being dependent on whether an X- or a Y-chromosome-bearing spermatozoon reaches the oocyte first. Here we investigated the alternative possibility, namely that the oviducts can recognise X- and Y- spermatozoa, and may thus be able to bias the offspring sex ratio.

RESULTS

By introducing X- or Y-sperm populations into the two separate oviducts of single female pigs using bilateral laparoscopic insemination we found that the spermatozoa did indeed elicit sex-specific transcriptomic responses. Microarray analysis revealed that 501 were consistently altered (P-value < 0.05) in the oviduct in the presence of Y-chromosome-bearing spermatozoa compared to the presence of X-chromosome-bearing spermatozoa. From these 501 transcripts, 271 transcripts (54.1%) were down-regulated and 230 transcripts (45.9%) were up-regulated when the Y- chromosome-bearing spermatozoa was present in the oviduct. Our data showed that local immune responses specific to each sperm type were elicited within the oviduct. In addition, either type of spermatozoa elicits sex-specific signal transduction signalling by oviductal cells.

CONCLUSIONS

Our data suggest that the oviduct functions as a biological sensor that screens the spermatozoon, and then responds by modifying the oviductal environment. We hypothesize that there might exist a gender biasing mechanism controlled by the female.

Identification of differentially expressed proteins in fresh and frozen–thawed boar spermatozoa by iTRAQ-coupled 2D LC–MS/MS

Cryodamage is a major problem in semen cryopreservation, causing changes in the levels of proteins that influence the function and motility of spermatozoa. In this study, protein samples prepared from fresh and frozen–thawed boar spermatozoa were compared using the isobaric tags for relative and absolute quantification (iTRAQ) labeling technique coupled to 2D LC–MS/MS analysis. A total of 41 differentially expressed proteins were identified and quantified, including 35 proteins that were present at higher levels and six proteins that were present at lower levels in frozen–thawed spermatozoa by at least a mean of 1.79-fold (P<0.05). On classifying into ten distinct categories using bioinformatic analysis, most of the 41 differentially expressed proteins were found to be closely relevant to sperm premature capacitation, adhesions, energy supply, and sperm–oocyte binding and fusion. The expression of four of these proteins, SOD1, TPI1, ODF2, and AKAP3, was verified by western blot analysis. We propose that alterations in these identified proteins affect the quality of cryopreserved semen and ultimately lower its fertilizing capacity. This is the first study to compare protein levels in fresh and frozen–thawed spermatozoa using the iTRAQ technology. Our preliminary results provide an overview of the molecular mechanisms of cryodamage in frozen–thawed spermatozoa and theoretical guidance to improve the cryopreservation of boar semen.

Differential protein profile in sexed bovine semen: shotgun proteomics investigation

The preparation of sexed semen is based on the differential DNA content between the X and Y chromosome bearing sperm cells determined by fluorescence-activated cell sorting. In spite of its intrinsic limitations this represents the only effective method. However, the employment of sexed sperm for breeding food producing animals on a large scale requires additional knowledge in the protein repertoire for the development of improved methods to differentiate X and Y sperm cells maintaining high vitality. In order to address this issue, we performed a comparative shotgun proteomic investigation by nUPLC-MS/MS to characterize sexed bovine semen. The protein profiles of these two types of sperm cells have shown differential expression of proteins that may be directly associated with the main components of cytoskeletal structures of flagellum, as the axoneme, outer dense fibers and fibrous sheath, as well as glycolytic enzymes and calmodulin, involved in the energetic metabolism regulation. Overall these results may provide a base to a better comprehension of the biological features of sperm cells and may be useful to the development of alternative methods of separation.