Comparative Transcriptomic Analysis of Spermatozoa From High- and Low-Fertile Crossbred Bulls: Implications for Fertility Prediction

Stress Biomarkers Transferred Into the Female Reproductive Tract by Seminal Plasma Are Associated with ICSI Outcomes

This study aimed to determine whether male stress is related to seminal stress biomarkers and pregnancy achievement in women exposed to their partner's seminal plasma (SP) in the intracytoplasmic sperm injection (ICSI) cycle. In this pilot prospective study, 20 couples undergoing ICSI, as well as 5 fertile sperm donors and 10 saliva donors, were investigated. Women were exposed to their partner's SP via unprotected sexual intercourse during the ICSI cycle and intravaginal application on the day of ovum pick-up (Day-OPU). Semen samples were collected from male partners by masturbation on the Day-OPU. Saliva and serum samples were collected prior to masturbation. Body fluids were frozen at - 80 °C until assayed. Biomarkers of activity of the sympathetic adrenomedullary axis (salivary alpha-amylase and adrenaline), sympathetic neural axis (noradrenaline and dopamine), hypothalamic-pituitary-adrenal (HPA) system (cortisol), and immune system (C-reactive protein and interleukin (IL)-18) were estimated to examine their association with SP composition and clinical pregnancy achievement. The clinical pregnancy rate was 45.0%. In the unsuccessful ICSI group, blunted levels of salivary and serum cortisol were found compared to the successful ICSI group and the fertile sperm donors. With regard to seminal markers, decreased cortisol level and elevated noradrenaline, noradrenaline/cortisol ratio, and lL-18 levels were strongly associated with ICSI failure (areas under the ROC curves were, 0.813, 0.848, 0.899, and 0.828, respectively). These findings confirm that stress response systems activity affects SP composition, which in turn is associated with ICSI outcomes in women exposed to their partner's SP during an ICSI cycle.

Factors affecting the success of laparoscopic artificial insemination in sheep

Successful artificial breeding underpins rapid genetic and production gains in animal agriculture. In sheep, artificial insemination with frozen semen is performed via intrauterine laparoscopy as frozen-thawed spermatozoa do not traverse the cervix in sufficient numbers for high fertility and transcervical insemination is anatomically impossible in most ewes. Historically, laparoscopic artificial insemination has always been considered reasonably successful, but recent anecdotal reports of poor fertility place it at risk of warning adoption. Understanding the male, female and environmental factors that influence the fertility of sheep is warranted if the success of artificial insemination is to be improved and genetic progress maximised for the sheep industry. This review details the current practice of laparoscopic AI in sheep. It explores the effects of semen quantity and quality, the ewe, her preparation, and environmental conditions, on the fertility obtained following laparoscopic artificial insemination.

Genomics and Dairy Bull Fertility

Current evidence suggests that dairy bull fertility is influenced by genetic factors, and hence, it could be managed and improved by genetic means. There are major mutations that explain about 4% to 8% of the observed differences in conception rate between bulls segregating in most dairy breeds. Research has shown that genomic prediction of bull fertility is possible, and this could be used to make accurate genome-guided selection decisions, such as early culling of predicted subfertile bull calves. Inbreeding negatively influences bull fertility, and the increase in homozygosity seems an important risk factor for dairy bull subfertility.

Expression of sperm microRNAs related to bull fertility: A systematic review

In this study we proposed to address the following question: "Are there differentially expressed sperm microRNAs related to fertility in bulls?". A systematic review of scientific literature until November 2022 was performed, in accordance with PRISMA guidelines. The main outcome was differentially expressed sperm microRNA from bulls with low versus high fertility profiles identified by using different methods such as field fertility evaluation and sperm laboratory analysis. Were identified 786 documents, of which 13 were selected for qualitative analysis. A total of 182 unique differentially expressed miRNAs were identified, among these, 49 miRNAs were found in common between at least two studies. It is believed that from these 49 miRNAs, it is possible that miRNAs such as miR-10a, -10b, -103, -15b, -122, -125b, -126-5p, -151-5p, -193a-5p, -196a, -27a-5p and -99b could be potential universal biomarkers to assess the reproductive potential of males.

Single nucleotide polymorphisms cumulating to genetic variation for fertility in crossbred (Bos taurus × Bos indicus) bull spermatozoa

Spermatozoa from high-fertile (HF) and low-fertile (LF) breeding bulls were subjected to high-throughput next-generation sequencing to identify important Single nucleotide polymorphisms (SNPs) and novel variants associated with fertility. A total of 77,038 genome-wide SNPs were identified, among which, 10,788 were novel variants. A total of 42,290 and 34,748 variants were recorded with 6115 and 4673 novel variants in in HF and LF bulls, respectively. Higher number of SNPs were identified in HF compared to LF bulls. GO analysis of filtered genes with significant variations in HF bulls indicated their involvement in oxidative phosphorylation and metabolic pathways. GO analysis of filtered genes with significant variation in LF bulls revealed their involvement in Ca2++ ion binding, structural constituent of ribosome, and biological processes like translation and ribosomal small subunit assembly. The study identified SNPs in candidate genes including TPT1, BOLA-DRA, CD74, RPS17, RPS28, RPS29, RPL14, RPL13, and RPS27A, which are linked to sperm functionality, survival, oxidative stress, and bull fertility. The identified SNPs could be used in selection of bulls for high fertility and the variation in these genes could be established as an explanation for the fertility differences in bulls upon validation in large number of bulls.

Transcriptome Analysis Reveals Spermatogenesis-Related CircRNAs and LncRNAs in Goat Spermatozoa

Mammalian spermatozoa comprises both coding and non-coding RNAs, which are traditionally believed to be a residual of spermatogenesis. The differential expression level of spermatozoal RNAs is also observed between fertile and infertile human, thereby anticipated as potential molecular marker of male fertility. This study investigated the transcriptome profile of goat (Capra hircus) spermatozoa. The sperm transcriptome was analyzed by three different methods viz. RLM-RACE, long-read RNA sequencing (RNAseq) in Nanopore™ platform, and short-read RNAseq in Illumina™ platform. The Illumina™ sequencing discovered 16,604 transcripts with 357 mRNAs having FPKM (fragments per kilobase per million mapped reads) of more than five. The spermatozoal RNA suite included mRNA (94%), rRNA (3%), miscRNA (1%), circRNA (1%), miRNA (1%), etc. This study also predicted circRNAs (127), lncRNAs (655), and imprinted genes (160) that have potential role in male reproduction. The gene ontology analysis revealed the involvement of spermatozoal RNA in regulating male meiosis (TET3, STAT5B), capacitation (ACRBP, CATSPER4), sperm motility (GAS8, TEKT2), spermatogenesis (ADAMTS2, CREB3L4), etc. The spermatozoal RNA were also associated with different biological pathways viz. Wnt signaling pathway, cAMP signaling pathway, AMPK signaling pathway, and MAPK signaling pathways having potential role in spermatogenesis. Overall, this study enlightened the suite of spRNA transcripts in goat and their relevance in male fertility for diagnostic approach.

Effect of arginine-induced motility and capacitation on RNA population in goat spermatozoa

INTRODUCTION

In vitro capacitation is essential in assisted reproductive technologies (ART) for embryo production. Recently, arginine has been proven to enhance capacitation in mammalian spermatozoa. However, the detailed mechanism of action of arginine remains elusive.

AIM

This study investigated the effect of arginine-induced capacitation and motility enhancement on the spermatozoal RNA (spRNA) population in goats.

MATERIAL AND METHODS

Goat spermatozoa were treated with arginine for up to six hours and compared with non-treated or PHE (penicillamine, hypotaurine, and epinephrine)-treated spermatozoa at different intervals (0, 1, 2, 4, and 6 hours). Sperm parameters, including viability, individual motility, capacitation, acrosome reaction, and ROS production, were evaluated. The spRNA population was analyzed by short-read RNA sequencing (RNA-seq).

RESULTS

The percentage of capacitated (73.21 ± 4.22%) and acrosome reacted (18.35 ± 0.56%) spermatozoa was highest in arginine treatment, while PHE treatment showed the highest percentage (79.82 ± 4.31%) of motile spermatozoa from 0 to 4 hours of incubation. RNA-seq analysis identified 1,321 differentially expressed genes (DEGs) in arginine-treated spermatozoa compared to the control. The PGK2, RNASE10, ODF1, and ROPN1L genes involved in sperm motility and ACR, DKKL1, KCNJ11, and PRND genes involved in the capacitation process were upregulated in arginine-treated spermatozoa. The DEGs regulate sperm capacitation-related cAMP-PKA, PI3-Akt, calcium, and MAPK signaling pathways.

CONCLUSION

The arginine-induced capacitation and enhanced sperm motility were associated with the upregulation of several genes involved in sperm motility and capacitation pathways. The comparative study also suggests that arginine may be used in lieu of PHE for motility enhancement and in vitro capacitation of goat spermatozoa.

Review: Evaluation of bull fertility. Functional and molecular approaches

With the term "assisted reproduction technologies" in modern cattle farming, one could imply the collection of techniques that aim at the optimal use of bovine gametes to produce animals of high genetic value in a time- and cost-efficient manner. The accurate characterisation of sperm quality plays a critical role for the efficiency of several assisted reproduction-related procedures, such as sperm processing, in vitro embryo production and artificial insemination. Bull fertility is ultimately a collective projection of the ability of a series of ejaculates to endure sperm processing stress, and achieve fertilisation of the oocyte and production of a viable and well-developing embryo. In this concept, the assessment of sperm functional and molecular characteristics is key to bull fertility diagnostics and prognostics. Among others, functional features linked to sperm plasma membrane, acrosome and DNA integrity are usually assessed as a measure of the ability of sperm to express the phenotypes that will allow them to maintain their homeostasis and orchestrate-in a strict temporal manner-the course of events that will enable the delivery of their genetic content to the oocyte upon fertilisation. Nevertheless, measures of sperm functionality are not always adequate indicators of bull fertility. Nowadays, advancements in the field of molecular biology have facilitated the profiling of several biomolecules in male gametes. The molecular profiling of bovine sperm offers a deeper insight into the mechanisms underlying sperm physiology and, thus, can reveal novel candidate markers for bull fertility prognosis. In this review, the importance of three organelles (the nucleus, the plasma membrane and the acrosome) for the characterisation of sperm fertilising capacity and bull fertility is discussed at functional and molecular levels. In particular, information about sperm head morphometry, chromatin structure, viability as well as the ability of sperm to capacitate and undergo the acrosome reaction are presented in relation to the cryotolerance of male gametes and bull fertility. Finally, major spermatozoal coding and non-coding RNAs, and proteins that are involved in the above-mentioned aspects of sperm functionality are also summarised.

Analyzing the effect of heparin on in vitro capacitation and spermatozoal RNA population in goats

Heparin is a glycosaminoglycan polymer that is commonly used as an anticoagulant. Heparin also induces in vitro capacitation in spermatozoa, although its molecular mechanism is elusive. This study investigated the effect of heparin on in vitro capacitation and spermatozoal RNA (spRNA) population in goats. Goat spermatozoa were treated with 20 μM heparin for 0-6 h and evaluated for motility, capacitation, acrosome reaction, and spRNA population by RNA sequencing (RNA-seq). It was observed that heparin enhanced sperm motility up to 6 h of incubation (p < 0.05). Heparin also induced capacitation and acrosome reaction within 4 h. RNA-seq identified 1254 differentially expressed genes (DEGs) between heparin-treated and control spermatozoa. Most DEGs (1251 nos.) were upregulated and included 1090 protein-coding genes. A few genes (PRND, ITPR1, LLCFC1, and CHRM2) showed >5-fold increased expression in heparin-treated spermatozoa compared to the control. The upregulated genes were found to be involved in cAMP-PKA, PI3-Akt, calcium, MAPK signaling, and oxidative stress pathways. DCFDA staining confirmed the increased oxidative stress in heparin-treated spermatozoa compared to the control (p < 0.05). In conclusion, the results of the present study suggest that heparin enhances sperm motility and induces capacitation by upregulation of the spRNA population and oxidative stress pathway.

Effect of corn straw or corncobs in total mixed ration during peri-puberty on testis development in Hu lambs

Corn straw and corncobs contain large amounts of crude fibers and are widely used in mutton sheep husbandry in northwest China. The aim of this study was to determine whether feeding with corn straw or corncobs affects lamb testis development. A total of 50 healthy Hu lamb at two-month-old (average body weight of 22.3 ± 0.1 kg) were randomly and equally divided into two groups, and the lambs were equally allocated to five pens in each group. The corn straw group (CS) received a diet containing 20% corn straw, whereas the corncobs group (CC) received a diet containing 20% corncobs. After a 77-day feeding trial, the lambs, except the heaviest and lightest in each pen, were humanely slaughtered and investigated. Results revealed no differences in body weight (40.38 ± 0.45 kg vs. 39.08 ± 0.52 kg) between the CS and CC groups. Feeding diet containing corn straw significantly (P < 0.05) increased testis weight (243.24 ± 18.78 g vs. 167.00 ± 15.20 g), testis index (0.60 ± 0.05 vs. 0.43 ± 0.04), testis volume (247.08 ± 19.99 mL vs. 162.31 ± 14.15 mL), diameter of seminiferous tubule (213.90 ± 4.91 μm vs. 173.11 ± 5.93 μm), and the number of sperm in the epididymis (49.91 ± 13.53 × 10⁸/g vs. 19.34 ± 6.79 × 10⁸/g) compared with those in the CC group. The RNA sequencing results showed 286 differentially expressed genes, and 116 upregulated and 170 downregulated genes were found in the CS group compared with the CC group. The genes affecting immune functions and fertility were screened out. Corn straw decreased the mtDNA relative copy number in the testis (P < 0.05). These results suggest that compared with corncobs, feeding corn straw in the early reproductive development stage of lambs increased the testis weight, diameter of seminiferous tubule and the number of cauda sperm.

High-throughput proteomic characterization of seminal plasma from bulls with contrasting semen quality

Seminal plasma proteins are the major extrinsic factors that can modulate the sperm quality and functions. The present study was carried out to compare the proteomic profiles of seminal plasma from breeding bulls producing good and poor quality semen in an effort to understand the possible proteins associated with semen quality. A total of 910 and 715 proteins were detected in the seminal plasma of poor and good quality semen producing bulls, respectively. A total of 705 proteins were common to both the groups, in which 380 proteins were upregulated and 89 proteins were downregulated in the seminal plasma of poor quality semen, while 236 proteins were co-expressed. The proteins negatively influencing sperm functions such as CCL2, UQCRC2, and SAA1 were among the top ten upregulated proteins in the seminal plasma of poor quality semen. Proteins having a positive role in sperm functions (NGF, EEF1A2, COL1A2, IZUMO4, PRSS1, COL1A1, WFDC2) were among the top ten downregulated proteins in the seminal plasma of poor quality semen. The upregulation of oxidation-reduction process-related proteins, histone proteins (HIST3H2A, H2AFJ, H2AFZ, H2AFX, HIST2H2AB, H2AFV, HIST1H2AC, HIST2H2AC, LOC104975684, LOC524236, LOC614970, LOC529277), and ubiquinol-cytochrome-c reductase proteins (UQCRB, UQCRFS1, UQCRQ, UQCRC1, UQCRC2) indicate deranged oxidation-reduction equilibrium, chromatin condensation and spermatogenesis in poor quality semen producing bulls. The expression of proteins essential for motile cilium (CCDC114, CFAP206, TEKT4), chromatin integrity (PRM2), gamete fusion (IZUMO4, EQTN), hyperactivation, tyrosine phosphorylation, and capacitation [PI3K-Akt signalling pathway-related proteins (COL1A1, COL2A1, COL1A2, SPP1, PDGFA, NGF)] were down regulated in poor quality semen producing bulls.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03474-6.

Deciphering sperm functions using biological networks

The global human population is exponentially increasing, which requires the production of quality food through efficient reproduction as well as sustainable production of livestock. Lack of knowledge and technology for assessing semen quality and predicting bull fertility is hindering advances in animal science and food animal production and causing millions of dollars of economic losses annually. The intent of this systemic review is to summarize methods from computational biology for analysis of gene, metabolite, and protein networks to identify potential markers that can be applied to improve livestock reproduction, with a focus on bull fertility. We provide examples of available gene, metabolic, and protein networks and computational biology methods to show how the interactions between genes, proteins, and metabolites together drive the complex process of spermatogenesis and regulate fertility in animals. We demonstrate the use of the National Center for Biotechnology Information (NCBI) and Ensembl for finding gene sequences, and then use them to create and understand gene, protein and metabolite networks for sperm associated factors to elucidate global cellular processes in sperm. This study highlights the value of mapping complex biological pathways among livestock and potential for conducting studies on promoting livestock improvement for global food security.

Sperm Transcriptome Analysis Accurately Reveals Male Fertility Potential in Livestock

Nowadays, selection of superior male candidates in livestock as a source of frozen semen based on sperm quality at the cellular level is not considered accurate enough for predicting the potential of male fertility. Sperm transcriptome analysis approaches, such as messenger RNA levels, have been shown to correlate with fertility rates. Using this technology in livestock growth has become the principal method, which can be widely applied to predict male fertility potential in the livestock industry through the analysis of the sperm transcriptome. It provides the gene expression to validate the function of sperm in spermatogenesis, fertilization, and embryo development, as the parameters of male fertility. This review proposes a transcriptomic analysis approach as a high-throughput method to predict the fertility potential of livestock more accurately in the future.

Cryopreservation process alters the expression of genes involved in pathways associated with the fertility of bull spermatozoa

In bovines, cryopreserved semen is used for artificial insemination; however, the fertility of cryopreserved semen is far lower than that of fresh semen. Although cryopreservation alters sperm phenotypic characteristics, its effect on sperm molecular health is not thoroughly understood. The present study applied next-generation sequencing to investigate the effect of cryopreservation on the sperm transcriptomic composition of bull spermatozoa. While freshly ejaculated bull spermatozoa showed 14,280 transcripts, cryopreserved spermatozoa showed only 12,375 transcripts. Comparative analysis revealed that 241 genes were upregulated, 662 genes were downregulated, and 215 genes showed neutral expression in cryopreserved spermatozoa compared to fresh spermatozoa. Gene ontology analysis indicated that the dysregulated transcripts were involved in nucleic acid binding, transcription-specific activity, and protein kinase binding involving protein autophosphorylation, ventricular septum morphogenesis, and organ development. Moreover, the dysregulated genes in cryopreserved spermatozoa were involved in pathways associated with glycogen metabolism, MAPK signalling, embryonic organ morphogenesis, ectodermal placode formation, and regulation of protein auto-phosphorylation. These findings suggest that the cryopreservation process induced alterations in the abundance of sperm transcripts related to potential fertility-associated functions and pathways, which might partly explain the reduced fertility observed with cryopreserved bull spermatozoa.

Identification of differentially expressed mRNAs and miRNAs in spermatozoa of bulls of varying fertility

Bulls used in artificial insemination, with apparently normal semen quality, can vary significantly in their field fertility. This study aimed to characterize the transcriptome of spermatozoa from high (HF) and low (LF) fertility bulls at the mRNA and miRNA level in order to identify potential novel markers of fertility. Holstein-Friesian bulls were assigned to either the HF or LF group (n = 10 per group) based on an adjusted national fertility index from a minimum of 500 inseminations. Total RNA was extracted from a pool of frozen-thawed spermatozoa from three different ejaculates per bull, following which mRNA-seq and miRNA-seq were performed. Six mRNAs and 13 miRNAs were found differentially expressed (P < 0.05, FC > 1.5) between HF and LF bulls. Of particular interest, the gene pathways targeted by the 13 differentially expressed miRNAs were related to embryonic development and gene expression regulation. Previous studies reported that disruptions to protamine 1 mRNA (PRM1) had deleterious consequences for sperm chromatin structure and fertilizing ability. Notably, PRM1 exhibited a higher expression in spermatozoa from LF than HF bulls. In contrast, Western Blot analysis revealed a decrease in PRM1 protein abundance for spermatozoa from LF bulls; this was not associated with increased protamine deficiency (measured by the degree of chromatin compaction) or DNA fragmentation, as assessed by flow cytometry analyses. However, protamine deficiency was positively and moderately correlated with the percentage of spermatozoa with DNA fragmentation, irrespective of fertility group. This study has identified potential biomarkers that could be used for improving semen quality assessments of bull fertility.

Spermatozoan Metabolism as a Non-Traditional Model for the Study of Huntington’s Disease

Huntington’s Disease (HD) is a fatal autosomal dominant neurodegenerative disease manifested through motor dysfunction and cognitive deficits. Decreased fertility is also observed in HD animal models and HD male patients, due to altered spermatogenesis and sperm function, thus resulting in reduced fertilization potential. Although some pharmaceuticals are currently utilized to mitigate HD symptoms, an effective treatment that remedies the pathogenesis of the disease is yet to be approved by the FDA. Identification of genes and relevant diagnostic biomarkers and therapeutic target pathways including glycolysis and mitochondrial complex-I-dependent respiration may be advantageous for early diagnosis, management, and treatment of the disease. This review addresses the HD pathway in neuronal and sperm metabolism, including relevant gene and protein expression in both neurons and spermatozoa, indicated in the pathogenesis of HD. Furthermore, zinc-containing and zinc-interacting proteins regulate and/or are regulated by zinc ion homeostasis in both neurons and spermatozoa. Therefore, this review also aims to explore the comparative role of zinc in both neuronal and sperm function. Ongoing studies aim to characterize the products of genes implicated in HD pathogenesis that are expressed in both neurons and spermatozoa to facilitate studies of future treatment avenues in HD and HD-related male infertility. The emerging link between zinc homeostasis and the HD pathway could lead to new treatments and diagnostic methods linking genetic sperm defects with somatic comorbidities.

Integrated multi-omics analyses reveals molecules governing sperm metabolism potentially influence bull fertility

Bull fertility is of paramount importance in bovine industry because semen from a single bull is used to breed several thousands of cows; however, so far, no reliable test is available for bull fertility prediction. In the present study, spermatozoa from high- and low-fertility bulls were subjected to high-throughput transcriptomic, proteomic and metabolomic analysis. Using an integrated multi-omics approach the molecular differences between high- and low-fertility bulls were identified. We identified a total of 18,068 transcripts, 5041 proteins and 3704 metabolites in bull spermatozoa, of which the expression of 4766 transcripts, 785 proteins and 33 metabolites were dysregulated between high- and low-fertility bulls. At transcript level, several genes involved in oxidative phosphorylation pathway were found to be downregulated, while at protein level genes involved in metabolic pathways were significantly downregulated in low-fertility bulls. We found that metabolites involved in Taurine and hypotaurine metabolism were significantly downregulated in low-fertility bulls. Integrated multi-omics analysis revealed the interaction of dysregulated transcripts, proteins and metabolites in major metabolic pathways, including Butanoate metabolism, Glycolysis and gluconeogenesis, Methionine and cysteine metabolism, Phosphatidyl inositol phosphate, pyrimidine metabolism and saturated fatty acid beta oxidation. These findings collectively indicate that molecules governing sperm metabolism potentially influence bull fertility.

Deciphering the genetic basis of male fertility in Italian Brown Swiss dairy cattle

Improving reproductive performance remains a major goal in dairy cattle worldwide. Service sire has been recognized as an important factor affecting herd fertility. The main objective of this study was to reveal the genetic basis of male fertility in Italian Brown Swiss dairy cattle. Dataset included 1102 Italian Brown Swiss bulls with sire conception rate records genotyped with 454k single nucleotide polymorphisms. The analysis included whole-genome scans and gene-set analyses to identify genomic regions, individual genes and genetic mechanisms affecting Brown Swiss bull fertility. One genomic region on BTA1 showed significant additive effects. This region harbors gene RABL3 which is implicated cell proliferation and motility. Two genomic regions, located on BTA6 and BTA26, showed marked non-additive effects. These regions harbor genes, such as WDR19 and ADGRA1, that are directly involved in male fertility, including sperm motility, acrosome reaction, and embryonic development. The gene-set analysis revealed functional terms related to cell adhesion, cellular signaling, cellular transport, immune system, and embryonic development. Remarkably, a gene-set analysis also including Holstein and Jersey data, revealed significant processes that are common to the three dairy breeds, including cell migration, cell–cell interaction, GTPase activity, and the immune function. Overall, this comprehensive study contributes to a better understanding of the genetic basis of male fertility in cattle. In addition, our findings may guide the development of novel genomic strategies for improving service sire fertility in Brown Swiss cattle.

Genom-wide analysis identifies single nucleotide polymorphism variations and altered pathways associated with poor semen quality in breeding bulls

The reason for poor semen quality among the breeding bulls is not well understood. In the present study, we performed high-throughput RNAseq analysis of spermatozoa to identify the SNPs present in good and poor-quality semen-producing Holstein Friesian breeding bulls. A total of 21,360 and 44,650 SNPs were identified in good and poor-quality semen with a minimum read depth of 20, among which 4780 and 8710 novel variants were observed in good and poor-quality semen, respectively. Greater SNPs and indels variations were observed in poor compared to good-quality semen. In poor-quality semen, SNP variations were observed in ZNF280B, SLC26A2, DMXL1, OR52A1, MACROD2 and REV1 genes, which are associated with regulation of spermatogenesis, post-testicular maturation, Cl^- channel activity, V-ATPase-mediated intracellular vesicle acidification, a mono-ADP-ribosyl hydrolase and ATR-Chk1 checkpoint activation. GO analysis of filtered genes with significant variations between good and poor-quality semen showed enrichment in important pathways related to semen quality such as MAPK signalling pathway, Akt signalling pathway, focal adhesion, cAMP signalling pathway, and Rap1 signalling pathway. Network analysis of filtered genes in poor-quality semen showed variations in pathways of purine metabolism, pyrimidine metabolism, prolactin signalling pathway and RNA cap-binding complex. It is inferred that SNP in genes involved in maintaining sperm functions could be the reason for poor-quality semen production in bulls, and the identified SNPs hold potential to be used as biomarkers for semen quality in bulls.

High throughput deep proteomic analysis of seminal plasma from stallions with contrasting semen quality

Seminal plasma proteins and pathways associated with sperm motility have not been elucidated in stallions. Therefore, in the current study, using the high throughput LC/MS-MS approach, we profiled stallion seminal plasma proteins and identified the proteins and pathways associated with sperm motility. Seminal plasma from six stallions producing semen with contrasting sperm motility (n = 3 each high-and low-motile group) was utilized for proteomic analysis. We identified a total of 1687 proteins in stallion seminal plasma, of which 1627 and 1496 proteins were expressed in high- (HM) and low- motile (LM) sperm of stallions, respectively. A total number of 1436 proteins were co-expressed in both the groups; 191 (11%) and 60 (3.5%) proteins were exclusively detected in HM and LM groups, respectively. A total of 220 proteins were upregulated (>1-fold change) and 386 proteins were downregulated in SP from LM group stallions as compared to HM group stallions, while 830 proteins were neutrally expressed in both the groups. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed dysregulation of the important proteins related to mitochondrial function, acrosome, and sperm cytoskeleton in the seminal plasma of stallions producing ejaculates with low sperm motility. High abundance of peroxiredoxins and low abundance of seminal Chaperonin Containing TCP1 Complex (CCT) complex and Annexins indicate dysregulated oxidative metabolism, which might be the underlying etiology for poor sperm motility in LM group stallions. In conclusion, the current study identified the seminal plasma proteomic alterations associated with poor sperm motility in stallions; the results indicate that poor sperm motility in stallions could be associated with altered expression of seminal plasma proteins involved in oxidative metabolism.

Sperm Transcripts Associated With Odorant Binding and Olfactory Transduction Pathways Are Altered in Breeding Bulls Producing Poor-Quality Semen

Spermatozoa carries a reservoir of mRNAs regulating sperm functions and fertilizing potential. Although it is well recognized that a considerable proportion of high genetic merit breeding bulls produce poor-quality semen, the transcriptomic alterations in spermatozoa from such bulls are not understood. In the present study, comparative high-throughput transcriptomic profiling of spermatozoa from good and poor-quality semen-producing bulls was carried out to identify the transcripts associated with semen quality. Using next-generation sequencing (NGS), we identified 11,632 transcripts in Holstein Friesian bull spermatozoa; after total hit normalization, a total of 544 transcripts were detected, of which 185 transcripts were common to both good and poor-quality semen, while 181 sperm transcripts were unique to good quality semen, and 178 transcripts were unique to poor-quality semen. Among the co-expressed transcripts, 31 were upregulated, while 108 were downregulated, and 46 were neutrally expressed in poor-quality semen. Bioinformatics analysis revealed that the dysregulated transcripts were predominantly involved in molecular function, such as olfactory receptor activity and odor binding, and in biological process, such as detection of chemical stimulus involved in sensory perception, sensory perception of smell, signal transduction, and signal synaptic transmission. Since a majority of the dysregulated transcripts were involved in the olfactory pathway (85% of enriched dysregulated genes were involved in this pathway), the expression of selected five transcripts associated with this pathway (OR2T11, OR10S1, ORIL3, OR5M11, and PRRX1) were validated using real-time qPCR, and it was found that their transcriptional abundance followed the same trend as observed in NGS; the sperm transcriptional abundance of OR2T11 and OR10S1 differed significantly (p < 0.05) between good and poor-quality semen. It is concluded that poor-quality semen showed altered expression of transcripts associated with olfactory receptors and pathways indicating the relationship between olfactory pathway and semen quality in bulls.

Significance and Relevance of Spermatozoal RNAs to Male Fertility in Livestock

Livestock production contributes to a significant part of the economy in developing countries. Although artificial insemination techniques brought substantial improvements in reproductive efficiency, male infertility remains a leading challenge in livestock. Current strategies for the diagnosis of male infertility largely depend on the evaluation of semen parameters and fail to diagnose idiopathic infertility in most cases. Recent evidences show that spermatozoa contains a suit of RNA population whose profile differs between fertile and infertile males. Studies have also demonstrated the crucial roles of spermatozoal RNA (spRNA) in spermatogenesis, fertilization, and early embryonic development. Thus, the spRNA profile may serve as unique molecular signatures of fertile sperm and may play pivotal roles in the diagnosis and treatment of male fertility. This manuscript provides an update on various spRNA populations, including protein-coding and non-coding RNAs, in livestock species and their potential role in semen quality, particularly sperm motility, freezability, and fertility. The contribution of seminal plasma to the spRNA population is also discussed. Furthermore, we discussed the significance of rare non-coding RNAs (ncRNAs) such as long ncRNAs (lncRNAs) and circular RNAs (circRNAs) in spermatogenic events.

Cellular and Molecular Insights Into the Etiology of Subfertility/Infertility in Crossbred Bulls (Bos taurus × Bos indicus): A Review

Crossbreeding of indigenous cattle (Bos indicus) with improved (Bos taurus) breeds gained momentum and economic relevance in several countries to increase milk production. While production performance of the crossbred offspring is high due to hybrid vigor, they suffer from a high incidence of reproductive problems. Specifically, the crossbred males suffer from serious forms of subfertility/infertility, which can have a significant effect because semen from a single male is used to breed several thousand females. During the last two decades, attempts have been made to understand the probable reasons for infertility in crossbred bulls. Published evidence indicates that testicular cytology indices, hormonal concentrations, sperm phenotypic characteristics and seminal plasma composition were altered in crossbred compared to purebred males. A few recent studies compared crossbred bull semen with purebred bull semen using genomics, transcriptomics, proteomics and metabolomics; molecules potentially associated with subfertility/infertility in crossbred bulls were identified. Nevertheless, the precise reason behind the poor quality of semen and high incidence of sub-fertility/infertility in crossbred bulls are not yet well defined. To identify the underlying etiology for infertility in crossbred bulls, a thorough understanding of the magnitude of the problem and an overview of the prior art is needed; however, such systematically reviewed information is not available. Therefore, the primary focus of this review is to compile and analyze earlier findings on crossbred bull fertility/infertility. In addition, the differences between purebred and crossbred males in terms of testicular composition, sperm phenotypic characteristics, molecular composition, environmental influence and other details are described; future prospects for research on crossbred males are also outlined.

Epididymosomes: A potential male fertility influencer

During transit and storage in epididymis, spermatozoa undergo final maturation, acquire motility, functional competence and the ability to fertilise an oocyte. Epididymal secretions contain a complex biochemical milieu of diverse inorganic ions, proteins, metabolites and other molecules. Since it is believed that spermatozoa are translationally silent, proteins appearing in them are thought to be synthesised elsewhere, including epididymis, and then incorporated to the cells. One of the important mechanisms suggested to be involved in transfer of epididymal secretions to spermatozoa is through exosomes called epididymosomes. Epididymosomes released from the epididymal epithelium contain proteins, noncoding RNAs and distinct set of lipids that are transferred to spermatozoa while they pass through the different epididymal regions. Owing to the importance of these molecules for sperm maturation and fertilising ability, research on epididymosomes has gained increasing attention during the last decade. This review is focused on epididymosomes, with emphasis on recent advances in the understanding of mechanisms of epididymosomal cargo transfer to spermatozoa and potential roles of epididymosomes in sperm function and beyond. Possibilities of utilising the molecular signatures of epididymosomes as a tool for male fertility assessment are also discussed.