Biology of sperm chromatin structure and relationship to male fertility and embryonic survival

Prediction of Nili-Ravi buffalo bull fertility through Fourier harmonic analysis of sperm

Fourier harmonic analysis (FHA) is a robust method for identification of minute changes in sperm nuclear shape that are indicative of reduced fertility. The current study was designed to develop a fertility prediction model for Nili-Ravi buffalo bulls through FHA of sperm. In experiment I, FHA technique was standardized, average sperm nuclear perimeter was measured and sperm nuclear shape plot of buffalo bull was constructed. Sperm of buffalo bulls (n = 10) were stained with YOYO-1 and Hoechst-33342 to differentiate live and dead, and digital images were captured using phase contrast and fluorescent microscopy. The images were analyzed by ImageJ software and 100 sperm/bull were evaluated. The results are described as mean ± SEM values of mean harmonic amplitude (mharm), skewness harmonic amplitude (skharm), kurtosis harmonic amplitude (kurharm) and variance harmonic amplitude (varharm) at Fourier frequencies 0-5 along with the cartesian and polar coordinate plots of buffalo bull sperm. In experiment II, a fertility prediction model was developed based on FHA of buffalo bull sperm. Semen samples of low (n = 6), medium (n = 3) and high (n = 8) fertility bulls were investigated for FHA of sperm and harmonic amplitudes (HA) were generated. Firstly, to determine if live and dead sperm population have unique nuclear shape distribution; the mean, skewness, kurtosis and variance HA 0-5 of 1700 live and 1294 dead spermatozoa of 17 bulls were evaluated. T-test signified a difference in the mharm0 (2.363 ± 0.01 vs. 2.439 ± 0.02), skharm0 (-0.0002 ± 0.07 vs. -0.266 ± 0.09), kurharm0 (-0.156 ± 0.07 vs. 0.260 ± 0.18), kurharm2 (0.142 ± 0.11 vs. 1.031 ± 0.32) and varharm4 (0.109 ± 0.00 vs. 0.082 ± 0.00) of live vs. dead sperm population (p < 0.05). Therefore, 100 live sperm/bull were further evaluated for mean, skewness, kurtosis and variance HA 0-5 values among high (n = 6) and low-fertility (n = 6) groups. Results of T-test showed higher values of mharm2 (0.739 ± 0.01 vs. 0.686 ± 0.00), mharm4 (0.105 ± 0.001 vs. 0.007 ± 0.001), and skharm0 (0.214 ± 0.109 vs. -0.244 ± 0.097) in high vs. low-fertility group (p < 0.05). In next step, five significantly different combinations of discriminant measures between high and low-fertility groups were obtained by discriminant analysis. In conclusion, mharm4, skharm0 and varharm2 correctly identified 91.7 % of bulls into their respective fertility groups, and upon cross validation the value of the canonical correlation was 0.928.

Use of assisted reproductive technologies (ARTs) to shorten the generational interval in ruminants: current status and perspectives

The challenges posed by climate change and increasing world population are stimulating renewed efforts for improving the sustainability of animal production. To meet such challenges, the contribution of genomic selection approaches, in combination with assisted reproductive technologies (ARTs), to spreading and preserving animal genetics is essential. The largest increase in genetic gain can be achieved by shortening the generation interval. This review provides an overview of the current status and progress of advanced ARTs that could be applied to reduce the generation time in both female and male of domestic ruminants. In females, the use of juvenile in vitro embryo transfer (JIVET) enables to generate offspring after the transfer of in vitro produced embryos derived from oocytes of prepubertal genetically superior donors reducing the generational interval and acceleration genetic gain. The current challenge is increasing in vitro embryo production (IVEP) from prepubertal derived oocytes which is still low and variable. The two main factors limiting IVEP success are the intrinsic quality of prepubertal oocytes and the culture systems for in vitro maturation (IVM). In males, advancements in ARTs are providing new strategies to in vitro propagate spermatogonia and differentiate them into mature sperm or even to recapitulate the whole process of spermatogenesis from embryonic stem cells. Moreover, the successful use of immature cells, such as round spermatids, for intracytoplasmic injection (ROSI) and IVEP could allow to complete the entire process in few months. However, these approaches have been successfully applied to human and mouse whereas only a few studies have been published in ruminants and results are still controversial. This is also dependent on the efficiency of ROSI that is limited by the current isolation and selection protocols of round spermatids. In conclusion, the current efforts for improving these reproductive methodologies could lead toward a significant reduction of the generational interval in livestock animals that could have a considerable impact on agriculture sustainability.

Molecular and Functional Characterization of Human Sex-Determining Region on the Y Chromosome Variants Using Protamine 1 Promoter

The male sex-determining gene, sex-determining region on the Y chromosome (SRY), is expressed in adult testicular germ cells; however, its role in regulating spermatogenesis remains unclear. The role of SRY in the postmeiotic gene expression was investigated by determining the effect of SRY on the promoter of the haploid-specific Protamine 1 (PRM1) gene, which harbors five distinct SRY-binding motifs. In a luciferase reporter assay system, SRY upregulates PRM1 promoter activity in vitro in a dose-dependent manner. Through a gel-shift assay involving a 31-bp DNA fragment encompassing the SRY element within the PRM1 promoter, the third SRY-binding site on the sense strand (-373/-367) was identified as crucial for PRM1 promoter activation. This assay was extended to analyze 9 SRY variants found in the testicular DNA of 44 azoospermia patients. The findings suggest that SRY regulates PRM1 promoter activity by directly binding to its specific motif within the PRM1 promoter.

Aniline blue test for sperm protamination-a valuable add-on to the bull breeding soundness evaluation

Bull breeding soundness evaluation (BBSE) is the most common procedure used to predict bull potential fertility. However, the use of traditional methods for semen evaluation can affect its reliability. The inclusion of additional advanced test in BBSE may increase its accuracy. This study aimed to investigate the correlation between the degree of sperm protamination and BBSE main parameters of scrotal circumference (SC), progressive motility (PM), morphologically normal sperm (NS), and different categories of morphological defects. In addition, to determine the correlation between the three methods used for protamine assessment, five Brangus bulls were subjected to the BBSE. Semen samples were collected via electro-ejaculation and evaluated using traditional methods. Three different methods were used to determine the degree of sperm protamination: aniline blue (AB) staining, chromomycin A3 staining with fluorescent microscope (CMA3-FLM), and CMA3 with flow cytometry (CMA3-FCM). Sperm protamine deficiency assessed using the three methods exhibited significant differences among bulls according to their classification by BBSE, and showed significant negative correlation with semen quality parameters of NS and PM. A significant positive correlation was found between AB positivity and morphological abnormalities. The three methods used for protamine assessment also revealed significant positive correlations. Among the three tests, AB staining was the cheapest and easiest test that offers an objective assessment method for sperm protamination. Hence, it can be concluded that the assessment of protamination using AB staining test might serve as an additional valuable parameter or a replacement whenever detail sperm motility and morphology analyses in conducting BBSE to predict bull fertility are not possible.

R-loop landscape in mature human sperm: Regulatory and evolutionary implications

R-loops are three-stranded nucleic acid structures consisting of an RNA:DNA hybrid and a displaced DNA strand. While R-loops pose a potential threat to genome integrity, they constitute 5% of the human genome. The role of R-loops in transcriptional regulation, DNA replication, and chromatin signature is becoming increasingly clear. R-loops are associated with various histone modifications, suggesting that they may modulate chromatin accessibility. To potentially harness transcription-coupled repair mechanisms in the germline, nearly the entire genome is expressed during the early stages of male gametogenesis in mammals, providing ample opportunity for the formation of a transcriptome-dependent R-loop landscape in male germ cells. In this study, our data demonstrated the presence of R-loops in fully mature human and bonobo sperm heads and their partial correspondence to transcribed regions and chromatin structure, which is massively reorganized from mainly histone to mainly protamine-packed chromatin in mature sperm. The sperm R-loop landscape resembles characteristic patterns of somatic cells. Surprisingly, we detected R-loops in both residual histone and protamine-packed chromatin and localize them to still-active retroposons, ALUs and SINE-VNTR-ALUs (SVAs), the latter has recently arisen in hominoid primates. We detected both evolutionarily conserved and species-specific localizations. Comparing our DNA-RNA immunoprecipitation (DRIP) data with published DNA methylation and histone chromatin immunoprecipitation (ChIP) data, we hypothesize that R-loops epigenetically reduce methylation of SVAs. Strikingly, we observe a strong influence of R-loops on the transcriptomes of zygotes from early developmental stages before zygotic genome activation. Overall, these findings suggest that chromatin accessibility influenced by R-loops may represent a system of inherited gene regulation.

An Overview of Essential Microelements and Common Metallic Nanoparticles and Their Effects on Male Fertility

Numerous factors affect reproduction, including stress, diet, obesity, the use of stimulants, or exposure to toxins, along with heavy elements (lead, silver, cadmium, uranium, vanadium, mercury, arsenic). Metals, like other xenotoxins, can cause infertility through, e.g., impairment of endocrine function and gametogenesis or excess production of reactive oxygen species (ROS). The advancement of nanotechnology has created another hazard to human safety through exposure to metals in the form of nanomaterials (NMs). Nanoparticles (NPs) exhibit a specific ability to penetrate cell membranes and biological barriers in the human body. These ultra-fine particles (<100 nm) can enter the human body through the respiratory tract, food, skin, injection, or implantation. Once absorbed, NPs are transported to various organs through the blood or lymph. Absorbed NPs, thanks to ultrahigh reactivity compared to bulk materials in microscale size, disrupt the homeostasis of the body as a result of interaction with biological molecules such as DNA, lipids, and proteins; interfering with the functioning of cells, organs, and physiological systems; and leading to severe pathological dysfunctions. Over the past decades, much research has been performed on the reproductive effects of essential trace elements. The research hypothesis that disturbances in the metabolism of trace elements are one of the many causes of infertility has been unquestionably confirmed. This review examines the complex reproductive risks for men regarding the exposure to potentially harmless xenobiotics based on a series of 298 articles over the past 30 years. The research was conducted using PubMed, Web of Science, and Scopus databases searching for papers devoted to in vivo and in vitro studies related to the influence of essential elements (iron, selenium, manganese, cobalt, zinc, copper, and molybdenum) and widely used metallic NPs on male reproduction potential.

Comparative Proteomic Analyses of Poorly Motile Swamp Buffalo Spermatozoa Reveal Low Energy Metabolism and Deficiencies in Motility-Related Proteins

The acquisition of mammalian sperm motility is a main indicator of epididymal sperm maturation and helps ensure fertilization. Poor sperm motility will prevent sperm cells from reaching the fertilization site, resulting in fertilization failure. To investigate the proteomic profiling of normal and poorly motile buffalo spermatozoa, a strategy applying liquid chromatography tandem mass spectrometry combined with tandem mass targeting was used. As a result, 145 differentially expressed proteins (DEPs) were identified in poorly motile spermatozoa (fold change > 1.5), including 52 upregulated and 93 downregulated proteins. The upregulated DEPs were mainly involved in morphogenesis and regulation of cell differentiation. The downregulated DEPs were involved with transport, oxidation-reduction, sperm motility, regulation of cAMP metabolism and regulation of DNA methylation. The mRNA and protein levels of PRM1 and AKAP3 were lower in poorly motile spermatozoa, while the expressions of SDC2, TEKT3 and IDH1 were not correlated with motility, indicating that their protein changes were affected by transcription or translation. Such changes in the expression of these proteins suggest that the formation of poorly motile buffalo spermatozoa reflects a low efficiency of energy metabolism, decreases in sperm protamine proteins, deficiencies in motility-related proteins, and variations in tail structural proteins. Such proteins could be biomarkers of poorly motile spermatozoa. These results illustrate some of the molecular mechanisms associated with poorly motile spermatozoa and provide clues for finding molecular markers of these pathways.

Insights into the Mechanism of Bovine Spermiogenesis Based on Comparative Transcriptomic Studies

Simple Summary

Any irregularity in spermiogenesis reduces the quality of semen and may lead to male sterility in cattle and humans. Thus, we investigated the differential transcriptomics of spermatids from round spermatid to epididymal sperm and compared them with the transcriptomics of mice in the same period. We found differentially expressed genes (DEGs) involved in sperm head and tail formation, and epigenetic regulatory networks which regulated genetic material condensation, the deformation of the spermatid, and the expression of genes in it. According to the sterility report on the ART3 protein and its possible epigenetic function, we detected that it was localised outside the spermatocyte, in round and elongated spermatids. Interestingly, we observed that the ART3 protein on round and elongated spermatids was localised approximately to the lumen of seminiferous tubule. It was also localised on the head and tail part near the head in epididymal sperm, suggesting its important role in the deformation from round spermatids to sperm. Our findings provide new insights into the molecular mechanism underlying bovine spermiogenesis, thereby contributing to the improved reproductive potential of cattle and the development of strategies for the diagnosis and treatment of male infertility.

Abstract

To reduce subfertility caused by low semen quality and provide theoretical guidance for the eradication of human male infertility, we sequenced the bovine transcriptomes of round, elongated spermatids and epididymal sperms. The differential analysis was carried out with the reference of the mouse transcriptome, and the homology trends of gene expression to the mouse were also analysed. First, to explore the physiological mechanism of spermiogenesis that profoundly affects semen quality, homological trends of differential genes were compared during spermiogenesis in dairy cattle and mice. Next, Gene Ontology (GO), Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment, protein–protein interaction network (PPI network), and bioinformatics analyses were performed to uncover the regulation network of acrosome formation during the transition from round to elongated spermatids. In addition, processes that regulate gene expression during spermiogenesis from elongated spermatid to epididymal sperm, such as ubiquitination, acetylation, deacetylation, and glycosylation, and the functional ART3 gene may play important roles during spermiogenesis. Therefore, its localisation in the seminiferous tubules and epididymal sperm were investigated using immunofluorescent analysis, and its structure and function were also predicted. Our findings provide a deeper understanding of the process of spermiogenesis, which involves acrosome formation, histone replacement, and the fine regulation of gene expression.

In Vivo and In Vitro Evaluation of Bull Semen Processed with Zinc (Zn) Nanoparticles

Defective sperms cause fertilization failure under both in vivo and in vitro conditions. Therefore, providing optimal conditions during semen storage is a prerequisite for maintaining viability. The current study investigated bull semen quality in vitro and in vivo when zinc (Zn) nanoparticles were used as antioxidant during semen processing and cryopreservation. In total, 32 ejaculates were collected from four Holstein bulls. All ejaculates were pooled and diluted with Bioxcell-extender containing 0 (control group), 10^-6, 10^-5, 10^-4, 10^-3, and 10^-2 M of Zn nanoparticles. Several physical and biochemical sperm parameters were determined after freeze-thawing process. In vitro embryo development rate and pregnancy rate were monitored after in vitro fertilization or artificial insemination using semen treated with Zn nanoparticles. Plasma membrane integrity was improved (P < 0.05) in bull semen treated with 10^-6 M (69.3%), and 10^-2 (62.4%) of Zn nanoparticles compared to untreated group (51.3%). In addition, proportions of live spermatozoa with active mitochondria were increased (P < 0.05) in semen supplemented with Zn nanoparticles at concentration of 10^-6 M (67.3%), and 10^-2 (85.3%) compared to control group (49.8%). Moreover, the level of MDA was lower (P < 0.05) in semen with Zn nanoparticles at 10^-6 M (2.97 mol/mL) and 10^-2 (2.7 mol/mL) concentrations than control semen samples (3.77 mol/mL). However, sperm total and progressive motility, sperm viability, DNA fragmentation, and pregnancy rate were not affected by treatment of semen with Zn nanoparticles. On the other hand, supplementation of in vitro maturation media with 10^-6 M Zn nanoparticles has increased blastocyst rate (P < 0.05) compared to other experimental groups, while addition of Zn nanoparticles-treated sperm during in vitro fertilization did not affect embryo development rate. In conclusion, supplementation of Zn nanoparticles to semen has improved its quality without affecting embryo development rate in vitro. However, in vitro embryo development rate was increased when Zn nanoparticles were supplemented to IVM media. This support the notion of Zn nanoparticles beneficial action on improving bovine gametes quality without affecting pregnancy rate.

X chromosome variants are associated with male fertility traits in two bovine populations

BACKGROUND

Twenty-five phenotypes were measured as indicators of bull fertility (1099 Brahman and 1719 Tropical Composite bulls). Measurements included sperm morphology, scrotal circumference, and sperm chromatin phenotypes such as DNA fragmentation and protamine deficiency. We estimated the heritability of these phenotypes and carried out genome-wide association studies (GWAS) within breed, using the bovine high-density chip, to detect quantitative trait loci (QTL).

RESULTS

Our analyses suggested that both sperm DNA fragmentation and sperm protamine deficiency are heritable (h2 from 0.10 to 0.22). To confirm these first estimates of heritability, further studies on sperm chromatin traits, with larger datasets are necessary. Our GWAS identified 12 QTL for bull fertility traits, based on at least five polymorphisms (P < 10-8) for each QTL. Five QTL were identified in Brahman and another seven in Tropical Composite bulls. Most of the significant polymorphisms detected in both breeds and nine of the 12 QTL were on chromosome X. The QTL were breed-specific, but for some traits, a closer inspection of the GWAS results revealed suggestive single nucleotide polymorphism (SNP) associations (P < 10-7) in both breeds. For example, the QTL for inhibin level in Braham could be relevant to Tropical Composites too (many polymorphisms reached P < 10-7 in the same region). The QTL for sperm midpiece morphological abnormalities on chromosome X (QTL peak at 4.92 Mb, P < 10-17) is an example of a breed-specific QTL, supported by 143 significant SNPs (P < 10-8) in Brahman, but absent in Tropical Composites. Our GWAS results add evidence to the mammalian specialization of the X chromosome, which during evolution has accumulated genes linked to spermatogenesis. Some of the polymorphisms on chromosome X were associated to more than one genetically correlated trait (correlations ranged from 0.33 to 0.51). Correlations and shared polymorphism associations support the hypothesis that these phenotypes share the same underlying cause, i.e. defective spermatogenesis.

CONCLUSIONS

Genetic improvement for bull fertility is possible through genomic selection, which is likely more accurate if the QTL on chromosome X are considered in the predictions. Polymorphisms associated with male fertility accumulate on this chromosome in cattle, as in humans and mice, suggesting its specialization.

Human sperm decondensation in vitro is related to cleavage rate and embryo quality in IVF

PURPOSE

To investigate whether the ability of human spermatozoa to decondense in vitro in the presence of heparin (Hep) and glutathione (GSH) is related to assisted reproduction (ART) success.

METHODS

Cross-sectional pilot study involving male partners of 129 infertile couples undergoing ICSI with (45) or without (84) donor oocytes at two infertility clinics in CABA, Argentina, between October 2012 and December 2013. In vitro decondensation kinetics with Hep and GSH and DNA fragmentation (TUNEL) were determined on the same sample used for ICSI. The possible relationship of decondensation parameters (maximum decondensation and decondensation velocity) and TUNEL values with ART success was evaluated.

RESULTS

Embryo quality correlated positively with decondensation velocity (D60/D30) (Spearman's correlation, p < 0.05). According to D60/D30 values, patients were classified as slow decondensers (SlowD) (n = 68) or fast decondensers (FastD) (n = 61). Embryo quality was better in FastD (unpaired t test, p < 0.05). FastD and SlowD were subdivided according to use of donor oocytes. Among SlowD, biochemical and clinical pregnancy rates per transfer were significantly higher in donor (n = 19) vs. in non-donor (n = 31) cycles (Fisher's exact test, p < 0.05). TUNEL values were not related to embryo quality, but no clinical pregnancies or live births were achieved in TUNEL+ SlowD (n = 7).

CONCLUSION

Decondensation kinetics of human spermatozoa in vitro with Hep and GSH could be related to embryo quality and ART success.

Testicular spermatozoon is superior to ejaculated spermatozoon for intracytoplasmic sperm injection to achieve pregnancy in infertile males with high sperm DNA damage

The purpose of this study was to compare the clinical outcome of testicular spermatozoon versus ejaculated spermatozoon in the treatment of infertile males with high sperm DNA damage, referred as sperm DNA fragmentation index (DFI), that attending intracytoplasmic sperm injection (ICSI) programme in terms of clinical pregnancy, births delivered as the primary and pregnancy loss and embryo fertilisation as the secondary outcome. A total of 102 males fulfilling the inclusion criteria were enrolled in the present study. Of the 102 males, 61 infertile males underwent testicular spermatozoon combined with ICSI while the remaining 41 males applied ejaculated spermatozoa in their first ICSI cycles, and the data of them were collected and analysed. In a 18-month follow-up, testicular spermatozoon achieved higher pregnancy rate and deliver rate than those in ejaculated sperm group (pregnancy rate, 36% vs. 14.6%, p = 0.017; deliver rate, 38.5% vs. 9.8%, p = 0.001). Nevertheless, there were no significant differences in the number of oocytes aspirated and number of embryos transferred between the two groups. Additionally, the fertilisation rate in the testicular sperm study cohort (70.4%) was also similar to that in the ejaculated sperm group (75.0%). Based on the current data, we conclude that testicular spermatozoon is the prior option in the treatment of infertile males with high sperm DFI in ICSI programme. More high-quality studies with larger samples size are needed in the future due to the relative small size and the nonrandomized design of the present study.

Paternal factors contributing to embryo quality

PURPOSE

Advancing maternal and paternal age leads to a decrease in fertility, and hence, many infertile couples opt for assisted reproductive technologies [ART] to achieve biological parenthood. One of the key determinants of achieving a live outcome of ART, embryo quality, depends on both the quality of the oocyte and sperm that have created the embryo. Several studies have explored the effect of oocyte parameters on embryo quality, but the effects of sperm quality on the embryo have not been comprehensively evaluated.

METHOD

In this review, we assess the effect of various genetic factors of paternal origin on the quality and development of the embryo.

RESULTS

The effects of sperm aneuploidy, sperm chromatin structure, deoxyribonucleic acid [DNA] fragmentation, role of protamines and histones, sperm epigenetic profile, and Y chromosome microdeletions were explored and found to negatively affect embryo quality.

CONCLUSION

We propose that careful assessment of spermatozoal parameters is essential to achieve embryo development and a healthy live birth. However, the heterogeneity in test results and the different approaches of assessing a single sperm parameter highlight the need for more research and the development of standardized protocols to assess the role of sperm factors affecting embryo quality.

Multiple-trait genomewide mapping and gene network analysis for scrotal circumference growth curves in Brahman cattle

Fertility traits are economically important in cattle breeding programs. Scrotal circumference (SC) measures are repeatable, easily obtained, highly heritable, and positively correlated with female fertility traits and sperm quality traits in males. A useful approach to summarize SC measures over time is using nonlinear models, which summarize specific measures of SC in a few parameters with biological interpretation. This approach facilitates the selection of bulls with larger SC and maturity index (K), that is, early maturing animals. Because SC is a sex-limited trait, identifying the underlying genomics of growth curve parameters will allow selection across both males and females. We reported the first multitrait genomewide association study (GWAS) of estimated growth curve parameters for SC data in Brahman cattle. Five widely used nonlinear models were tested to fit a total of 3,612 SC records, measured at 6, 12, 18, and 24 mo of age. The von Bertalanffy model, individually fitted for each animal, best fit this SC data. Parameter estimates SC at maturity (A) and K as well as SC at all ages were jointly analyzed in a GWAS to identify 1-Mb regions most strongly associated with each trait. Heritabilities were 0.25 for K and 0.32 for A and ranged from 0.51 to 0.72 for SC at 6 (SC6), 12 (SC12), 18 (SC18), and 24 mo of age (SC24). An overlapping window on chromosome 14 explaining around 0.8% of genetic variance for K, SC12, SC18, and SC24 was observed. The major positional candidate genes within 1 Mb upstream and downstream of this overlapping window were , , , and . Windows of 1 Mb explaining more than 0.4% of each trait on chromosomes 1, 3, 6, 7, 14, 17, 18, 24, 25, and 26 were identified. Pathways and net-work analyses were indicated through transcription factors playing a role on fertility traits: , , , , , , and . Further validation studies on larger populations or other breeds are required to validate these findings and to improve our understanding of the biology and complex genetic architecture of traits associated with scrotal growth and male fertility in cattle.

Is transcription in sperm stationary or dynamic?

Transcriptional activity is repressed due to the packaging of sperm chromatins during spermiogenesis. The detection of numerous transcripts in sperm, however, raises the question whether transcriptional events exist in sperm, which has been the central focus of the recent studies. To summarize the transcriptional activity during spermiogenesis and in sperm, we reviewed the documents on transcript differences during spermiogenesis, in sperm with differential motility, before and after capacitation and cryopreservation. This will lay a theoretical foundation for studying the mechanism(s) of gene expression in sperm, and would be invaluable in making better use of animal sires and developing reproductive control technologies.

Viable offspring obtained from Prm1-deficient sperm in mice

Protamines are expressed in the spermatid nucleus and allow denser packaging of DNA compared with histones. Disruption of the coding sequence of one allele of either protamine 1 (Prm1) or Prm2 results in failure to produce offspring, although sperm with disrupted Prm1 or Prm2 alleles are produced. Here, we produced Prm1-deficient female chimeric mice carrying Prm1-deficient oocytes. These mice successfully produced Prm1(+/-) male mice. Healthy Prm1(+/-) offspring were then produced by transferring blastocysts obtained via in vitro fertilization using zona-free oocytes and sperm from Prm1(+/-) mice. This result suggests that sperm lacking Prm1 can generate offspring despite being abnormally shaped and having destabilised DNA, decondensed chromatin and a reduction in mitochondrial membrane potential. Nevertheless, these mice showed little derangement of expression profiles.

Presence of the Paternal Pronucleus Assists Embryo in Overcoming Cycloheximide Induced Abnormalities in Zygotic Mitosis

After fertilization, the maternal and paternal chromosomes independently proceed through pronuclear formation. These chromatin reconfigurations occur within a shared cytoplasm thus exposing both gametes to the same factors. Here, we report that continuous cycloheximide [40 μg/mL] treatment of parthenogenotes, androgenotes, and ICSI embryos reveals ORC2 pronuclear instability in the maternal (MPN) but not the paternal pronucleus (PPN). When released from CHX after 8 h, the MPN can recover ORC2 and proceed through replication, however, parthenogenotes encounter severe mitotic defects while both ICSI embryos and androgenotes are able to recover and develop at significantly higher rates. Taken together, these data suggest cycloheximide treatment promotes an environment that asymmetrically affects the stability of ORC2 on the MPN, and the ability of the MPN to develop. Furthermore, the presence of the PPN in the zygote can ameliorate both effects. These data suggest further evidence for crosstalk between the two pronuclei during the first cell cycle of the embryo. J. Cell. Biochem. 117: 1806-1812, 2016. © 2016 Wiley Periodicals, Inc.

Male factors in ART outcome prediction

Paternal influences on reproduction are significant causing about half of the infertile couples to turn to assisted reproductive techniques. Due to the increasing proportion of infertile couples adopting to conceive by in vitro fertilisation (IVF), predicting outcomes is of ever increasing importance. Since pregnancy rates following IVF are still quite low, prognostic information is very helpful in clinical decisions. Although significant research has been done on the maternal influence, male factor infertility is relatively understudied. To date, potential predictors include: method of fertilisation, age, reactive oxygen species, sperm quality parameters and DNA fragmentation. Predictors under investigation which show promising signs, even though there is no clear cut consensus on the predictive value to date include: folate and homocysteine, anti müllerian hormone measurement, environmental factors, body mass index, smoking, male age, stress, some subsets of antisperm antibodies and epigenetic features.

Sperm protamine-status correlates to the fertility of breeding bulls

During fertilization, spermatozoa make essential contributions to embryo development by providing oocyte activating factors, centrosomal components, and paternal chromosomes. Protamines are essential for proper packaging of sperm DNA; however, in contrast to the studies of oocyte-related female infertility, the influence of sperm chromatin structure on male infertility has not been evaluated extensively. The objective of this study was to determine the sperm chromatin content of bull spermatozoa by evaluating DNA fragmentation, chromatin maturity/protamination, PRM1 protein status, and nuclear shape in spermatozoa from bulls with different fertility. Relationships between protamine 1 (PRM1) and the chromatin integrity were ascertained in spermatozoa from Holstein bulls with varied (high vs. low) but acceptable fertility. Sperm DNA fragmentation and chromatin maturity (protamination) were tested using Halomax assay and toluidine blue staining, respectively. The PRM1 content was assayed using Western blotting and in-gel densitometry, flow cytometry, and immunocytochemistry. Fragmentation of DNA was increased and chromatin maturity significantly reduced in spermatozoa from low-fertility bulls compared to those from high-fertility bulls. Field fertility scores of the bulls were negatively correlated with the percentage of spermatozoa displaying reduced protamination and fragmented DNA using toluidine blue and Halomax, respectively. Bull fertility was also positively correlated with PRM1 content by Western blotting and flow cytometry. However, detection of PRM1 content by Western blotting alone was not predictive of bull fertility. In immunocytochemistry, abnormal spermatozoa showed either a lack of PRM1 or scattered localization in the apical/acrosomal region of the nuclei. The nuclear shape was distorted in spermatozoa from low-fertility bulls. In conclusion, we showed that inadequate amount and localization of PRM1 were associated with defects in sperm chromatin structure, coinciding with reduced fertility in bulls. These findings are highly significant because they reveal molecular and morphological phenotypes of mammalian spermatozoa that influence fertility.

Treatment of aromatase (CYP19A1) inhibitor reduces fertility in porcine sperm

To ascertain whether aromatase (CYP19A1) expression is linked to sperm fertility of pigs, the present study determined the expression of the CYP19A1 gene in porcine sperm and its relationship with fertilization in vitro. First, to investigate its role in fertility, the presence of CYP19A1 of mRNA and protein expression in porcine sperm were confirmed by real-time (RT) or quantitative polymerase chain reaction (q-PCR) and by western blots. The expression levels were determined quantitatively using two sperm groups recovered by a Percoll gradient, which revealed that the sperm group with a low density had a higher penetration rate than that of the high-density group (P < 0.05). However, the expression level of CYP19A1 was not significantly different between the two groups. Secondly, to examine the effect of aromatase activity on fertilization, fresh semen was treated with a steroidal inhibitor, exemestane (50 μM for 0.5 h), followed by the dose- and time-dependent viability test. Our results clearly showed that an exemestane treatment effect (P < 0.05) was found for both the sperm-penetration rate and the oocyte cleavage rate. These results indicated that CYP19A1 could be involved in sperm fertility and its expression in sperm plays an important role in fertilization.

Validation of the sperm chromatin dispersion (SCD) test in the amphibian Xenopus laevis using in situ nick translation and comet assay

The integrity of sperm DNA is becoming increasingly recognised as an important parameter of semen quality, but there are no published reports of this procedure for any amphibian. The primary aim of this study was to apply a modified sperm chromatin dispersion (SCD) test (Halomax) to an amphibian sperm model (African clawed frog; Xenopus laevis) and to validate the assay against in situ nick translation (ISNT) and the double-comet assay procedure. Inactivated spermatozoa were collected from fresh testes (n = 3). Sperm DNA fragmentation (SDF) for each sperm sample was conducted immediately following activation (T0) and again after 1 h (T1) and 24 h (T24) of incubation at room temperature in order to produce a range of spermatozoa with differing levels of DNA damage. The SCD procedure resulted in the production of three nuclear morphotypes; amphibian sperm morphotype 1 (ASM-1) and ASM-2 showed no evidence of DNA damage, whereas ASM-3 spermatozoa were highly fragmented with large halos of dispersed DNA fragments and a reduced nuclear core. ISNT confirmed that ASM-3 nuclei contained damaged DNA. There was a significant correlation (r = 0.9613) between the levels of ASM-3 detected by the SCD test and SDF revealed by the double-comet assay.

Sperm protamine deficiency correlates with sperm DNA damage in Bos indicus bulls

The primary purpose of spermatozoa is to deliver the paternal DNA to the oocyte at fertilization. During the complex events of fertilization, if the spermatozoon penetrating the oocyte contains compromised or damaged sperm chromatin, the subsequent progression of embryogenesis and foetal development may be affected. Variation in sperm DNA damage and protamine content in ejaculated spermatozoa was reported in the cattle, with potential consequences to bull fertility. Protamines are sperm-specific nuclear proteins that are essential to packaging of the condensed paternal genome in spermatozoa. Sperm DNA damage is thought to be repaired during the process of protamination. This study investigates the potential correlation between sperm protamine content, sperm DNA damage and the subsequent relationships between sperm chromatin and commonly measured reproductive phenotypes. Bos indicus sperm samples (n = 133) were assessed by two flow cytometric methods: the sperm chromatin structure assay (SCSA) and an optimized sperm protamine deficiency assay (SPDA). To verify the SPDA assay for bovine sperm protamine content, samples collected from testis, caput and cauda epididymidis were analyzed. As expected, mature spermatozoa in the cauda epididymidis had higher protamine content when compared with sperm samples from testis and caput epididymidis (p < 0.01). The DNA fragmentation index (DFI), determined by SCSA, was positively correlated (r = 0.33 ± 0.08, p < 0.05) with the percentage of spermatozoa that showed low protamine content using SPDA. Also, DFI was negatively correlated (r = -0.21 ± 0.09, p < 0.05) with the percentage of spermatozoa with high protamine content. Larger scrotal circumference contributes to higher sperm protamine content and lower content of sperm DNA damage (p < 0.05). In conclusion, sperm protamine content and sperm DNA damage are closely associated. Protamine deficiency is likely to be one of the contributing factors to DNA instability and damage, which can affect bull fertility.

Changeability of sperm chromatin structure during liquid storage of ovine semen in milk-egg yolk- and soybean lecithin-based extenders and their relationships to field-fertility

The aim of this experiment was to study the effect of semen extender on sperm chromatin structure and to correlate chromatin integrity with field-fertility of preserved ram semen. Ejaculates of at least 2 × 10(9) sperm/ml and 70 % progressive motility were collected using an artificial vagina from Chios rams (n = 11, 4-6 years old), split-diluted to 1 × 10(9) sperm/ml with milk-egg yolk- and soybean lecithin (Ovixcell®)-based extenders, packaged in 0.5-ml straws and examined after 6, 24 and 48 h of storage at 5 ± 1 °C. Evaluation endpoints were computer-assisted sperm motion analysis, fluorescence-based analysis of chromatin structure by chromomycin A3 and acridine orange assays, and 65-day pregnancy rate (PR) of 34- to 36-h preserved semen after intra-cervical insemination of ewes (n = 154) in progestagen-synchronized estrus. Neither extender nor storage time had any influence on incidence of decondensed chromatin. Unlike Ovixcell® extender, deterioration of sperm motility (P < 0.01) and chromatin stability (P < 0.005) was detected after 48 h of storage in milk-egg yolk extender. Sperm motility accounted for 14.4-18.5 % of variations in chromatin integrity (P < 0.001). No significant difference was found in PR of Ovixcell®- and milk-egg yolk-stored semen. Nevertheless, PR differed between rams (14.3-71.4 %; P < 0.025). Chromatin integrity explained 10.2-56.3 % of variations in PR (P < 0.05-0.01). A pronounced decline in PR (19.1 %) was observed when percentages of decondensed and destabilized chromatin have reached thresholds of 10.5-30 % and 4-9 %, respectively. In conclusion, Ovixcell® is superior to milk-egg yolk extender in preserving chromatin stability and motility. Chromatin defects are negatively associated with sperm fertility.

Molecular morphology and function of bull spermatozoa linked to histones and associated with fertility

Sub-par fertility in bulls is influenced by alterations in sperm chromatin, and it might not be solved with increased sperm concentration in artificial insemination. Appropriate histone retention during sperm chromatin condensation plays critical roles in male fertility. The objective of this study was to determine failures of sperm chromatin condensation associated with abnormal persistence or accessibility of histones by aniline blue (ANBL) test, expression levels, and cellular localizations of one variant and two core histones (H3.3, H2B, and H4 respectively) in the spermatozoa of low-fertility (LF) vs high-fertility (HF) bulls. The expression levels and cellular localizations of histones in spermatozoa were studied using immunoblotting, immunocytochemistry, and staining methods. The bioinformatics focused on the sequence identity and evolutionary distance of these proteins among three mammalian species: bovine, mouse, and human. We demonstrated that ANBL staining was different within the LF (1.73 (0.55, 0.19)) and HF (0.67 (0.17, 0.06)) groups (P<0.0001), which was also negatively correlated within vivobull fertility (r=−0.90,P<0.0001). Although these histones were consistently detectable and specifically localized in bull sperm cells, they were not different between the two groups. Except H2B variants, H3.3 and H4 showed 100% identity and were evolutionarily conserved in bulls, mice and humans. The H2B variants were more conserved between bulls and humans, than in mice. In conclusion, we showed that H2B, H3.3, and H4 were detectable in bull spermatozoa and that sperm chromatin condensation status, changed by histone retention, is related to bull fertility.

Reproductive effects of two neonicotinoid insecticides on mouse sperm function and early embryonic development in vitro

Acetamiprid (ACE) and imidacloprid (IMI) are two major members in the family of neonicotinoid pesticides, which are synthesized with a higher selectivity to insects. The present study determined and compared in vitro effects of ACE, IMI and nicotine on mammalian reproduction by using an integrated testing strategy for reproductive toxicology, which covered sperm quality, sperm penetration into oocytes and preimplantation embryonic development. Direct chemical exposure (500 µM or 5 mM) on spermatozoa during capacitation was performed, and in vitro fertilization (IVF) process, zygotes and 2-cell embryos were respectively incubated with chemical-supplemented medium until blastocyst formation to evaluate the reproductive toxicity of these chemicals and monitor the stages mainly affected. Generally, treatment of 500 µM or 5 mM chemicals for 30 min did not change sperm motility and DNA integrity significantly but the fertilization ability in in vitro fertilization (IVF) process, indicating that IVF process could detect and distinguish subtle effect of spermatozoa exposed to different chemicals. Culture experiment in the presence of chemicals in medium showed that fertilization process and zygotes are adversely affected by direct exposure of chemicals (P<0.05), in an order of nicotine>IMI>ACE, whereas developmental progression of 2-cell stage embryos was similar to controls (P>0.05). These findings unveiled the hazardous effects of neonicotinoid pesticides exposure on mammalian sperm fertilization ability as well as embryonic development, raising the concerns that neonicotinoid pesticides may pose reproductive risks on human reproductive health, especially in professional populations.

Alteration of poly(ADP-ribose) metabolism affects murine sperm nuclear architecture by impairing pericentric heterochromatin condensation

The mammalian sperm nucleus is characterized by unique properties that are important for fertilization. Sperm DNA retains only small numbers of histones in distinct positions, and the majority of the genome is protamine associated, which allows for extreme condensation and protection of the genetic material. Furthermore, sperm nuclei display a highly ordered architecture that is characterized by a centrally located chromocenter comprising the pericentromeric chromosome regions and peripherally positioned telomeres. Establishment of this unique and well-conserved nuclear organization during spermiogenesis is not well understood. Utilizing fluorescence in situ hybridization (FISH), we show that a large fraction of the histone-associated sperm genome is repetitive in nature, while a smaller fraction is associated with unique DNA sequences. Coordinated activity of poly(ADP-ribose) (PAR) polymerase and topoisomerase II beta has been shown to facilitate DNA relaxation and histone to protamine transition during spermatid condensation, and altered PAR metabolism is associated with an increase in sperm histone content. Combining FISH with three-dimensional laser scanning microscopy technology, we further show that altered PAR metabolism by genetic or pharmacological intervention leads to a disturbance of the overall sperm nuclear architecture with a lower degree of organization and condensation of the chromocenters formed by chromosomal pericentromeric heterochromatin.

Protamine and fertilin mRNA: potential biomarkers of assisted reproductive technology outcomes

We studied the relationship between the levels of protamines 1 and 2 (PRM1 and PRM2) and fertilin-β (ADAM-2) mRNA expression and outcomes of infertility treatment using assisted reproductive technologies was studied. Analysis of the relationships between the outcomes of in vitro fertilization and embryo transfer and profiles of the expression of seminal genes PRM1, PRM2, ADAM-2 mRNA, evaluated by reverse transcription quantitative PCR was carried out in 79 couples. Significant differences in the expression of seminal PRM1, PRM2, ADAM-2 mRNA were detected in couples with different outcomes of in vitro fertilization and embryo transfer. The levels of seminal gene expression are potential predictors of the efficiency of in vitro fertilization and embryo transfer.

Novel insights into the genetic and epigenetic paternal contribution to the human embryo

The integrity of the sperm genome and epigenome are critical for normal embryonic development. The advent of assisted reproductive technology has led to an increased understanding of the role of sperm in fertilization and embryogenesis. During fertilization, the sperm transmits not only nuclear DNA to the oocyte but also activation factor, centrosomes, and a host of messenger RNA and microRNAs. This complex complement of microRNAs and other non-coding RNAs is believed to modify important post-fertilization events. Thus, the health of the sperm genome and epigenome is critical for improving assisted conception rates and the birth of healthy offspring.

Estrogens and spermiogenesis: new insights from type 1 cannabinoid receptor knockout mice

Spermatogenesis is a complex mechanism which allows the production of male gametes; it consists of mitotic, meiotic, and differentiation phases. Spermiogenesis is the terminal differentiation process during which haploid round spermatids undergo several biochemical and morphological changes, including extensive remodelling of chromatin and nuclear shape. Spermiogenesis is under control of endocrine, paracrine, and autocrine factors, like gonadotropins and testosterone. More recently, emerging pieces of evidence are suggesting that, among these factors, estrogens may have a role. To date, this is a matter of debate and concern because of the agonistic and antagonistic estrogenic effects that environmental chemicals may have on animal and human with damaging outcome on fertility. In this review, we summarize data which fuel this debate, with a particular attention to our recent results, obtained using type 1 cannabinoid receptor knockout male mice as animal model.

The effects of different sugars on motility, morphology and DNA damage during the liquid storage of rat epididymal sperm at 4°C

This study evaluated the protective effects of supplementation with three different sugars on the motility, morphology and DNA integrity of rat epididymal sperm chilled and stored at 4°C Epididymides were obtained from each donor. Rat epididymal sperm was diluted in Ham's F10 plus raffinose, Ham's F10 plus trehalose, Ham's F10 plus fructose, and Ham's F10 medium for control purposes. Thereafter, the extended sperm were chilled and stored in liquid form at 4°C. Sperm motility, morphological abnormalities and DNA damage were determined at 0 and 12h after chilling. No significant difference was observed in any of the parameters evaluated at 0h, before storage (P>0.05). After 12h of storage, all sugar additives led to statistically higher motility, normal sperm morphology and DNA integrity in comparison to the control group. Raffinose gave the best motility percentages (32.86±1.84%) after 12h of storage at 4°C, compared to the other groups (P<0.001). In conclusion, Raffinose, trehalose and fructose provided a better protection of sperm functional parameters against chilling injury, in comparison to the control group.

The integrity of sperm chromatin in young tropical composite bulls

Sperm chromatin fragmentation is associated with subfertility, but its relationship with age progression in young bulls is poorly understood. The objective was to assess sperm chromatin fragmentation during the early post-pubertal development of 20 tropical composite bulls, using a sperm chromatin structure assay (SCSA) and sperm-bos-halomax (SBH). Bulls were subjected to bull breeding soundness evaluation (BBSE) at mean ages of 13, 18, and 24 mo. Traits measured included liveweight (WT), body condition score (BCS) and scrotal circumference (SC). Semen samples were collected by electroejaculation and assessed for mass activity (MA), motility (Mot), concentration (conc), sperm morphology and chromatin fragmentation. Concentration (r=0.34, P=0.0076), Mot (r=0.36, P=0.0041) and percentage of morphologic normal sperm (percent normal sperm (PNS); r=0.31, P=0.0132) were positively correlated with age. The percentage of sperm with proximal droplets (PD) was negatively correlated with age (r=-0.28, P=0.0348), whereas neither SCSA nor SBH results were significantly correlated with age. The percentage of sperm with chromatin fragmentation using SCSA was correlated with PNS (r=-0.53, P<0.0001), the percentage of sperm with head abnormalities (r=0.68, P<0.0001) and the percentage of intact sperm (Int) with SBH (r=-0.26, P=0.0456). In summary, for assessment of sperm chromatin fragmentation, samples could be equally collected at 13, 18 or 24 mo of age, as results did not vary with age.

Conserved properties of Drosophila and human spermatozoal mRNA repertoires

It is now well established that mature mammalian spermatozoa carry a population of mRNA molecules, at least some of which are transferred to the oocyte at fertilization, however, their function remains largely unclear. To shed light on the evolutionary conservation of this feature of sperm biology, we analysed highly purified populations of mature sperm from the fruitfly, Drosophila melanogaster. As with mammalian sperm, we found a consistently enriched population of mRNA molecules that are unlikely to be derived from contaminating somatic cells or immature sperm. Using tagged transcripts for three of the spermatozoal mRNAs, we demonstrate that they are transferred to the oocyte at fertilization and can be detected before, and at least until, the onset of zygotic gene expression. We find a remarkable conservation in the functional annotations associated with fly and human spermatozoal mRNAs, in particular, a highly significant enrichment for transcripts encoding ribosomal proteins (RPs). The substantial functional coherence of spermatozoal transcripts in humans and the fly opens the possibility of using the power of Drosophila genetics to address the function of this enigmatic class of molecules in sperm and in the oocyte following fertilization.

Using the product threshold model for estimating separately the effect of temperature on male and female fertility

Animals under environmental thermal stress conditions have reduced fertility due to impairment of some mechanisms involved in their reproductive performance that are different in males and females. As a consequence, the most sensitive periods of time and the magnitude of effect of temperature on fertility can differ between sexes. The objective of this study was to estimate separately the effect of temperature in different periods around the insemination time on male and on female fertility by using the product threshold model. This model assumes that an observed reproduction outcome is the result of the product of 2 unobserved variables corresponding to the unobserved fertilities of the 2 individuals involved in the mating. A total of 7,625 AI records from rabbits belonging to a line selected for growth rate and indoor daily temperature records were used. The average maximum daily temperature and the proportion of days in which the maximum temperature was greater than 25°C were used as temperature descriptors. These descriptors were calculated for several periods around the day of AI. In the case of males, 4 periods of time covered different stages of the spermatogenesis, the transit through the epididymus of the sperm, and the day of AI. For females, 5 periods of time covered the phases of preovulatory follicular maturation including day of AI and ovulation, fertilization and peri-implantational stage of the embryos, embryonic and early fetal periods of gestation, and finally, late gestation until birth. The effect of the different temperature descriptors was estimated in the corresponding male and female liabilities in a set of threshold product models. The temperature of the day of AI seems to be the most relevant temperature descriptor affecting male fertility because greater temperature records on the day of AI caused a decrease in male fertility (-6% in male fertility rate with respect to thermoneutrality). Departures from the thermal zone in temperature descriptors covering several periods before AI until early gestation had a negative effect on female fertility, with the pre- and peri-implantational period of the embryos being especially sensitive (from -5 to -6% in female fertility rate with respect to thermoneutrality). The latest period of gestation was unaffected by the temperature. Overall, magnitude and persistency of the temperatures reached in the conditions of this study do not seem to be great enough to have a large effect on male and female rabbit fertility.

A review of factors that impact on the capacity of beef cattle females to conceive, maintain a pregnancy and wean a calf-Implications for reproductive efficiency in northern Australia

A review of factors that may impact on the capacity of beef cattle females, grazing semi-extensive to extensive pastures in northern Australia, to conceive, maintain a pregnancy and wean a calf was conducted. Pregnancy and weaning rates have generally been used to measure the reproductive performance of herds. However, this review recognises that reproductive efficiency and the general measures associated with it more effectively describe the economic performance of beef cattle enterprises. More specifically, reproductive efficiency is influenced by (1) pregnancy rate which is influenced by (i) age at puberty; (ii) duration of post-partum anoestrus; (iii) fertilisation failure and (iv) embryo survival; while (2) weight by number of calves per breeding female retained for mating is influenced by (i) cow survival; (ii) foetal survival; and (iii) calf survival; and (3) overall lifetime calf weight weaned per mating. These measures of reproductive efficiency are discussed in depth. Further, a range of infectious and non-infectious factors, namely, environmental, physiological, breed and genetic factors and their impact on these stages of the reproductive cycle are investigated and implications for the northern Australian beef industry are discussed. Finally, conclusions and recommendations to minimise reproductive inefficiencies based on current knowledge are presented.