Identification of novel polymorphisms in the nuclear protein genes and their relationship with human sperm protamine deficiency and severe male infertility

Impact of tobacco smoking in association with H2BFWT, PRM1 and PRM2 genes variants on male infertility

Tobacco's genotoxic components can cause a wide range of gene defects in spermatozoa such as single- or double-strand DNA breaks, cross-links, DNA-adducts, higher frequencies of aneuploidy and chromosomal abnormalities. The aim in this study was to determine the correlation between sperm quality determined by standard parameters, sperm DNA maturity tested by Chromomycin A3 (CMA3) staining, sperm DNA fragmentation tested by TUNEL assay and tobacco smoking in association with the single nucleotides polymorphisms (SNP) of three nuclear protein genes in spermatozoa (H2BFWT, PRM1 and PRM2). In this study, semen samples of 167 male patients were collected and divided into 54 non-smokers and 113 smokers. The target sequences in the extracted sperm DNA were amplified by PCR followed by Sanger sequencing. The results showed the presence of three variants: rs7885967, rs553509 and rs578953 in H2BFWT gene in the study population. Only one variant rs737008 was detected in PRM1 gene, and three variants were detected in the PRM2 gene: rs2070923, rs1646022 and rs424908. No significant association was observed between the concentration, progressive motility, morphology and the occurrence of H2BFWT, PRM1 and PRM2 SNPs. However, sperm parameters were significantly lower in heavy smokers compared to controls (p < 0.01) (sperm count: 46.00 vs. 78.50 mill/ml, progressive motility: 15.00% vs. 22.00%, and morphology 4.00% vs. 5.00%, respectively). Moreover, the heavy smoker individuals exhibited a considerable increase in CMA3 positivity and sDF compared to non-smokers (p < 0.01) (29.50% vs. 20.50% and 24.50% vs. 12.00%, respectively). In conclusion, smoking altered sperm parameters and sperm DNA integrity, but did not show a linkage with genetic variants in H2BFWT, and protamine genes (PRM1 and PRM2).

Impact of heavy alcohol consumption and cigarette smoking on sperm DNA integrity

The purposes of the presents study were to investigate the impact of alcohol consumption and cigarette smoking on semen parameters and sperm DNA quality, as well as to determine whether tobacco smoking, or alcohol consumption causes more deterioration of sperm quality. Two hundred and eleven semen samples of men were included in this study. Four groups were studied: heavy smokers (N = 48), heavy drinkers (N = 52), non-smokers (n = 70), and non-drinkers (n = 41). Semen parameters were determined according to WHO guidelines, protamine deficiency assessed by chromomycin (CMA3) staining, and sperm DNA fragmentation (sDF) evaluated by TUNEL assay. Sperm parameters were significantly higher in non-smokers versus smokers and in non-drinkers versus drinkers (p < 0.005). However, protamine deficiency and sDF were significantly lower in non-smokers versus smokers and in non-drinkers versus drinkers (p < 0.0001). No significant difference in the semen analysis parameters was observed between heavy smokers and heavy drinkers (semen volume: 3.20 ± 1.43 vs. 2.81 ± 1.56 ml, semen count: 65.75 ± 31.32 vs. 53.51 ± 32.67 mill/ml, total motility: 24.27 ± 8.18 vs. 23.75 ± 1.75%, sperm vitality: 36.15 ± 18.57 vs. 34.62 ± 16.65%, functional integrity: 41.56 ± 18.57 vs. 45.96 ± 17.98% and the morphologically normal spermatozoa: 28.77 ± 11.82 vs. 27.06 ± 13.13%, respectively). However, protamine deficiency was significantly higher among drinkers than smokers (37.03 ± 9.75 vs. 33.27 ± 8.56%, p = 0.020). The sDF was also significantly higher among drinkers than smokers (22.37 ± 7.60 vs. 15.55 ± 3.33%, p < 0.0001). Thus, cigarette smoking, and heavy alcohol intake can deteriorate sperm quality. However, alcohol consumption deteriorates sperm maturity and damages DNA integrity at significantly higher rates than cigarette smoking.

Polymorphisms in the HSF2, LRRC6, MEIG1 and PTIP genes correlate with sperm motility in idiopathic infertility

The aim of this study was to investigate the association of 24 functionally important single nucleotide polymorphisms (SNPs) with male infertility. In this cross-sectional study, we genotyped 24 functionally important single nucleotide polymorphisms in 24 infertility candidate genes in 500 oligo-/astheno-/oligoastheno-/normo-zoospermic infertile men with idiopathic infertility. Sequenom iPlex gold assay was used for genotyping. Sperm count and motility were compared between prevalent genotypes at each test locus. We did not observe any significant difference in the average sperm count between the alternate genotypes for the loci in the KLK3, LRRC6, MEIG1, HSF2, ESR2 and PTIP genes. However, we observed a significant difference in sperm motility between the alternate genotypes for the loci in the LRRC6, MEIG1, HSF2 and PTIP genes. Polymorphisms in the LRRC6 (rs200321595), MEIG1 (rs150031795), HSF2 (rs143986686) and PTIP (rs61752013) genes show association with sperm motility.

Genetic variations as molecular diagnostic factors for idiopathic male infertility: current knowledge and future perspectives

INTRODUCTION

Infertility is a major health problem, worldwide, which affects 10-15% of couples. About half a percent of infertility cases are related to male-related factors. Male infertility is a complex disease that is the result of various insults as lifestyle issues, genetics, and epigenetic factors. Idiopathic infertility is responsible for 30% of total cases. The genetic factors responsible for male infertility include chromosomal abnormalities, deletions of chromosome Y, and mutations and genetic variations of key genes.

AREAS COVERED

In this review article, we aim to narrate performed studies on polymorphisms of essential genes involved in male infertility including folate metabolizing genes, oxidative stress-related genes, inflammation, and cellular pathways related to spermatogenesis. Moreover, possible pathophysiologic mechanisms responsible for genetic polymorphisms are discussed.

EXPERT OPINION

Analysis and assessment of these genetic variations could help in screening, diagnosis, and treatment of idiopathic male infertility.

Identification of the PRM1 gene mutations in oligoasthenoteratozoospermic men

Mutations or altered expression of PRM1 gene have been associated with male infertility. This study aimed to analyse pathogenic variations of PRM1 gene in Iranian Arab infertile men with oligoasthenoteratozoospermia that was carried out for the first time in this population. Genomic DNA was used to perform PCR sequencing in PRM1 untranslated regions, exons and intron. Also, bioinformatics analysis was recruited to discover the possible effect of detected variations. Two pathogenic variations were seen in two men with oligoasthenoteratozoospermia, which were not found in the control group. The cDNA.384G>C variation is novel and was located in the 3' untranslated region, and cDNA.42G>A variation is reported for the first time related to male infertility and was found in 5' untranslated regions. Bioinformatics analysis showed that the minimum free energy was increased from -19.9kcal/mol to -13.1kcal/mol due to the cDNA.384G>C variation at hsa-miR-4326's seed site. More analysis revealed cDNA.42G>A located in transcription factors binding site, E1 and MYOD, which was detected as a promoter-associated region, and generally have regulatory features for acetylation and methylation. In conclusion, two pathogenic variations were recognised in regulatory areas of PRM1 gene, which might interfere with some critical factors related to PRM1 gene expression, hence cause male infertility.

Evaluation of the association between polymorphisms of PRM1 and PRM2 and the risk of male infertility: a systematic review, meta-analysis, and meta-regression

Studies have reported the genetic gives rise to male infertility. The aim of the present meta-analysis was to evaluate the association between PRM1 (rs737008 and rs2301365) and PRM2 (rs1646022 and rs2070923) polymorphisms and susceptibility to male infertility. The association between PRM1 and PRM2 polymorphisms and the risk of male infertility was evaluated using specific search terms in the Web of Science, Cochrane Library, PubMed, and Scopus databases without language restriction until January 28, 2020. The association was determined by odds ratio (OR) and 95% confidence interval (CI) on five genetic models using Review Manager 5.3 software. The funnel plot analysis and sensitivity analysis were done by the Comprehensive Meta-analysis 2.0 software. Out of 261 records retrieved from the databases, 17 studies were analyzed in the meta-analysis, including the four PRM polymorphisms. The pooled results as OR (P-value) showed 0.96 (0.44), 1.04 (0.70), 0.94 (0.51), 0.94 (0.48), and 1.03 (0.72) for PRM1 rs737008 polymorphism and 1.67 (0.0007), 1.73 (0.06), 1.50 (0.007), 1.56 (0.004), and 1.62 (0.33) for PRM1 rs2301365 polymorphism in allele, homozygous, heterozygous, recessive, and dominant models, respectively. Moreover, the pooled results as OR (P-value) showed 1.19 (0.004), 1.15 (0.26), 1.08 (0.70), 1.05 (0.76), and 0.98 (0.82) for PRM2 rs1646022 and 0.88 (0.04), 0.84 (0.10), 1.05 (0.81), 0.90 (0.24), and 0.80 (0.02) for PRM2 rs2070923 in allele, homozygous, heterozygous, recessive, and dominant models, respectively. The results showed PRM1 rs2301365 and PRM2 rs1646022 polymorphisms were associated with an elevated risk of male infertility and PRM2 rs2070923 polymorphism had a protective role in infertile men.

The SSC15 QTL-Rich Region Mutations Affecting Intramuscular Fat and Production Traits in Pigs

One of the more interesting regions in the pig genome is on chromosome 15 (115,800,000-122,100,000, SSC15, Sus scrofa 11.1) that has high quantitative trait locus (QTL) density associated with fattening, slaughter and meat quality characteristics. The SSC15 region encodes over 80 genes and a few miRNA sequences where potential genetic markers can be found. The goal of the study was to evaluate the effects of SSC15 mutations associated with villin 1 (VIL1), tensin 1 (TNS1), obscurin-like 1 (OBSL1) genes and with one long non-coding RNA (lncRNA) on productive pig traits and to enrich the genetic marker pool in further selection purpose. The potential genetic markers were identified using the targeted enrichment DNA sequencing (TEDNA-seq) of chromosome 15 region. The selected mutations were genotyped by using HRM, PCR and PCRRFLP methods. The association study was performed using the general linear model (GLM) in the sas program that included over 600 pigs of 5 Polish populations. The rs332253419 VIL1 mutation shows a significant effect on intramuscular fat (IMF) content in Duroc population where AA pigs had a 16% higher level than heterozygotes. The IMF content is also affected by the OBSL1 mutation, and the differences between groups are even up to 30%, but it is strongly dependent on breed factor. The OBSL1 mutation also significantly influences the meat yellowness, backfat thickness and pH level. The performed study delivers valuable information that could be highly useful during the development of the high-throughput genotyping method for further selection purposes in pigs. The OBSL1 and VIL1 mutations seem to be the most promising DNA marker showing a high effect on IMF level.

The effect of vitamin C on the gene expression profile of sperm protamines in the male partners of couples with recurrent pregnancy loss: A randomized clinical trial

Objective

Since sperm abnormalities are known to be a major reason for recurrent pregnancy loss (RPL), any defects in DNA structure and chromatin condensation can place embryos at risk in the early stage of development and implantation. As antioxidants such as vitamin C may play a protective role against the destruction of protamine genes in sperm chromatin, this study was conducted to evaluate the effects of vitamin C on chromatin and the expression of protamine genes in the male partners of couples with RPL.

Methods

Twenty male partners of couples with RPL were selected as the intervention group and received vitamin C supplementation (250 mg daily for 3 months). Healthy fertile men (n=20) were included as controls. Sperm chromatin, DNA integrity, and the expression levels of protamine genes were evaluated before and after treatment.

Results

Significant differences were found in sperm morphology, protamine deficiency, and apoptosis between the two groups and before and after vitamin C administration. A significant change was found in mRNA levels of PRM1, PRM2, and the PRM1/PRM2 ratio after treatment.

Conclusion

Daily oral administration of vitamin C may improve human sperm parameters and DNA integrity by increasing protamine gene expression levels in the male partners of couples with RPL. The beneficial effects of vitamin C supplementation as an antioxidant for the male partners of couples with RPL could lead to improved pregnancy outcomes in these cases.

Sperm cellular and nuclear dynamics associated with bull fertility

The objective of this study was to ascertain cellular characteristics and the dynamics of the sperm chromatin proteins protamine 1 (PRM1) and protamine 2 (PRM2) in the sperm of Holstein bulls having a different fertility status. Important sperm variables were analyzed using computer-assisted sperm analysis (CASA). Sperm membrane, acrosome status, DNA integrity were also assessed using propidium iodide (PI), fluorescein isothiocyanate conjugated to Arachis hypogaea (FITC-PNA), and acridine orange (AO) followed by flow cytometry. In addition, abundances of PRM1 and PRM2 were analyzed using flow cytometry experiments. Differences in sperm decondensation capacity were assessed in bulls of varying fertility using a decondensation assay. As determined using CASA, average pathway velocity, amplitude of lateral head displacement and straightness were different (P < 0.05) for sperm from high and low fertility bulls. There, however, were no differences between the high and low fertility bulls for characteristics of sperm plasma membrane, acrosome, and DNA integrity (P >  0.05). Relative abundances of PRM1 and PRM2 in sperm from the high and low fertility bulls were inversely related (P <  0.0001). Percentages of decondensed sperm were different between high and low fertility bulls (P < 0.0001) and total numbers of decondensed sperm were greater in low fertility bulls than high fertility bulls (R² = 0.72). Results of the present study are significant because molecular and morphological phenotypes of sperm that were detected affect fertility in livestock species.

Dephosphorylation of protamine 2 at serine 56 is crucial for murine sperm maturation in vivo

The posttranslational modification of histones is crucial in spermatogenesis, as in other tissues; however, during spermiogenesis, histones are replaced with protamines, which are critical for the tight packaging of the DNA in sperm cells. Protamines are also posttranslationally modified by phosphorylation and dephosphorylation, which prompted our investigation of the underlying mechanisms and biological consequences of their regulation. On the basis of a screen that implicated the heat shock protein Hspa4l in spermatogenesis, we generated mice deficient in Hspa4l (Hspa4l-null mice), which showed male infertility and the malformation of sperm heads. These phenotypes are similar to those of Ppp1cc-deficient mice, and we found that the amount of a testis- and sperm-specific isoform of the Ppp1cc phosphatase (Ppp1cc2) in the chromatin-binding fraction was substantially less in Hspa4l-null spermatozoa than that in those of wild-type mice. We further showed that Ppp1cc2 was a substrate of the chaperones Hsc70 and Hsp70 and that Hspa4l enhanced the release of Ppp1cc2 from these complexes, enabling the freed Ppp1cc2 to localize to chromatin. Pull-down and in vitro phosphatase assays suggested the dephosphorylation of protamine 2 at serine 56 (Prm2 Ser⁵⁶) by Ppp1cc2. To confirm the biological importance of Prm2 Ser⁵⁶ dephosphorylation, we mutated Ser⁵⁶ to alanine in Prm2 (Prm2 S56A). Introduction of this mutation to Hspa4l-null mice (Hspa4l ^-/-; Prm2 ^S56A/S56A) restored the malformation of sperm heads and the infertility of Hspa4l ^-/- mice. The dephosphorylation signal to eliminate phosphate was crucial, and these results unveiled the mechanism and biological relevance of the dephosphorylation of Prm2 for sperm maturation in vivo.

Analysis of PRM1 and PRM2 Polymorphisms in Iranian Infertile Men with Idiopathic Teratozoospermia

Single nucleotide polymorphisms (SNPs) in a number of genes involved in sperm maturation are considered as one of the main factors for male infertility. The aim of the present case-control study was to examine the association of SNPs in protamine1 (PRM1) and protamine2 (PRM2) genes with idiopathic teratozoospermia. In this case-control study, some SNPs in PRM1 (c.49 C>T, c.102 G>T and c.230A>C) and PRM2 (rs545828790, rs115686767, rs201933708, rs2070923 and rs1646022) were investigated in 30 idiopathic infertile men with teratozoospermia (case group) in comparison with 35 fertile men (controls). Genotyping of SNPs was undertaken using polymerase chain reaction (PCR)-direct sequencing. For PRM1, c.230A>C, as a synonymous polymorphism, was detected in both teratozoo- spermic men (heterozygous n=26, homozygous minor n=1) allele frequency C(48) A(52) and controls (heterozygous n=15, homozygous minor n=4). All cases and controls were genotyped for rs545828790 in PRM2, a missense poly- morphism, as well as rs115686767 and rs201933708, both of which synonymous variants. The findings showed an intronic variant in PRM2 (rs2070923) was also present in both groups. Also, rs1646022, a missense polymorphism, occurred in teratozoospermic men (heterozygous n=10, homozygous minor n=5) and controls (heterozygous n=13, homozygous minor n=2). However, there were no significant differences in SNPs of PRM1 and PRM2 between the two groups, however, for c.230A>C, the frequency of the CA genotype was significantly higher in infertile men with teratozoospermia (P=0.001). We demonstrate that PRM2 G398C and A473C polymorphisms were associated with the teratozoospermia and its genetic variation was in relation to semen quality, sperm apoptosis, and morphology in the Iranian population. This study is a preliminary study and presenting data as part of a future comprehensive study to clinically establish whether these gene polymorphisms are biomarkers for susceptibility to teratozoospermia.

Nucleotide variability of protamine genes influencing bull sperm motility variables

Protamines (PRMs), important proteins of chromatin condensation in spermiogenesis, are promising candidate genes to explore markers of sperm motility. The coding and in-silico predicted promoter regions of these genes were investigated in 102 crossbred and 32 purebred cattle. Also, mRNA quantification was done to explore its possibility as diagnostic tool of infertility. The PCR-SSCP analysis indicated there were two band patterns only in fragment I of the PRM1 and fragment II of the PRM2 gene. The sequence analysis revealed A152G and G179A transitions in the PRM1 gene. Similarly, G35A, A49G and A64G transitions were identified in the PRM2 gene which resulted in altered amino acid sequences from arginine (R) to glutamine (Q), from arginine (R) to glycine (G) and from arginine (R) to glycine (G), respectively. This caused the reduction in molecular weight of PRM2 from 2157.66 to 1931.33 Da due to reduction in the number of basic amino acids. These altered properties of the PRM2 protein led to the reduction in Mass Motility (MM: P < 0.01), Initial Progressive Motility (IPM; P < 0.05) and Post Thaw Motility (PTM; P < 0.05) in crossbred bulls. The least squares analysis of variance indicated there was an effect of PRM2 haplotypes on MM (P = 0.0069), IPM (P = 0.0306) and PTM (P = 0.0500) in crossbred cattle and on PTM (P = 0.0408) in the overall cattle population. Based on the RT-qPCR analysis, however, there was not any significant variation of PRM1 and PRM2 gene expression among sperm of Vrindavani bulls with relatively lesser and greater sperm motility.

Systematic review and meta-analysis of the genetic association between protamine polymorphism and male infertility

While several previous studies have proposed an association between male infertility and protamine polymorphism, the reported findings have shown some inconsistency. To evaluate the potential association between the two most common single nucleotide polymorphisms (rs2301365 and rs1646022) in protamine and male infertility, we performed a meta-analysis involving 2713 cases and 2086 controls from 15 published case-controlled studies. Overall, our analysis showed significant associations between the specific protamine single-nucleotide polymorphism (rs2301365) and male infertility, and this association was indicated by all of the models we tested. Subgroup analysis revealed significant associations with a Caucasian background, PCR sequence, population-based, case size of > 150 and case size of < 150 subgroups. Similarly, significant associations were found between rs1646022 and male infertility in the hospital population and case size of < 200 subgroups. However, trial sequential analysis showed that the number of patients in the study did not reach optimal information size. Further studies with larger sample sizes are now warranted to clarify the potential roles of the two protamine polymorphisms in the pathogenesis of male infertility. This may help us to understand the precise molecular mechanisms underlying the effect of protamines upon male infertility.

Genetic Polymorphisms in PRM1, PRM2, and YBX2 Genes are Associated with Male Factor Infertility

AIMS

The etiology of infertility is still unknown in almost half of all male infertility patients. In sperm, DNA condensation differs from somatic and female gamete cells, with the protamine (PRM) gene and its transcription factor, Y-box binding protein 2 (YBX2), playing key roles in making the structure more compact. Protamine polymorphisms have been studied in different populations, but various results have been acquired.

MATERIALS AND METHODS

In our study, we examined, for the first time in a Turkish population, the association between protamine gene alleles (PRM1 c.-190C>A, PRM1 c.197G>T, and PRM2 c.248C>T), and YBX2 (c.187T>C and c.1095 + 16A>G) and male infertility. This was accomplished using polymerase chain reaction-restriction fragment length polymorphism analyses of 100 infertile and 100 fertile Turkish men. Sperm DNA fragmentation analysis was performed using the Comet technique.

RESULTS

We found that the AA and CA genotypes of the PRM1 c.-190C>A polymorphism had a significant association with infertility (p < 0.001) and the AA genotype was also highly significantly associated with high sperm DNA damage (p < 0.001).

CONCLUSION

This study demonstrates that the PRM1 c.-190C>A polymorphism is associated with sperm DNA fragmentation, which may impact male infertility in the Turkish population. Further research with larger groups and in various other study populations will be required to clarify the impact of protamine and YBX2 gene polymorphisms on male infertility.

Polymorphisms of protamine genes contribute to male infertility susceptibility in the Chinese Han population

Protamine (PRM) plays important roles in the packaging of DNA within the sperm nucleus. To investigate the role of PRM1/2 and transition protein 1 (TNP1) polymorphisms in male infertility, 636 infertile men and 442 healthy individuals were recruited into this case-controlled study of the Chinese Han population, using MassARRAY technology to analyze genotypes. Our analysis showed that there were no significant differences between controls and infertile cases among the five single nucleotide polymorphisms identified in PRM1, PRM2 and TNP1 [rs737008 (G/A), rs2301365 (C/A), rs2070923 (C/A), rs1646022 (C/G) and rs62180545 (A/G)]. However, we found that the PRM1 and PRM2 haplotypes GCTGC, TCGCA and TCGCC exhibited significant protective effects against male infertility compared to fertile men, while TCGGA, GCTCC and TCGGC represented significant risk factors for spermatogenesis. Our data showed that rs737008 and rs2301365 in PRM1, and rs1646022 in PRM2, were significantly associated with male infertility and that gene–gene interaction played a role in male infertility. A linkage disequilibrium plot for the five SNPs showed that rs737008 was strongly linked with both rs2301365 and rs2070923. These findings are likely to help improve our understanding of the etiology of male infertility. Further studies should include a larger number of genes and SNPs, particularly growing critical genes; such studies will help us to unravel the effect of individual genetic factors upon male infertility.

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.

Comparison of Protamine 1 to Protamine 2 mRNA Ratio and YBX2 gene mRNA Content in Testicular Tissue of Fertile and Azoospermic Men

Background

Although aberrant protamine (PRM) ratios have been observed in infertile men, the mechanisms that implicit the uncoupling of PRM1 and PRM2 expression remain unclear. To uncover these mechanisms, in this observational study we have compared the PRM1/PRM2 mRNA ratio and mRNA contents of two regulatory factors of these genes.

Materials and Methods

In this experimental study, sampling was performed by a multi-step method from 50 non-obstructive azoospermic and 12 normal men. After RNA extraction and cDNA synthesis, real-time quantitative polymerase chain reaction (RT- QPCR) was used to analyze the PRM1, PRM2, Y box binding protein 2 (YBX2) and JmjC-containing histone demethylase 2a (JHDM2A) genes in testicular biopsies of the studied samples.

Results

The PRM1/PRM2 mRNA ratio differed significantly among studied groups, namely 0.21 ± 0.13 in azoospermic samples and -0.8 ± 0.22 in fertile samples. The amount of PRM2 mRNA, significantly reduced in azoospermic patients. Azoospermic men exhibited significant under expression of YBX2 gene compared to controls (P<0.001). mRNA content of this gene showed a positive correlation with PRM mRNA ratio (R=0.6, P=0.007). JHDM2A gene expression ratio did not show any significant difference between the studied groups (P=0.3). We also observed no correlation between JHDM2A mRNA content and the PRM mRNA ratio (R=0.2, P=0.3).

Conclusion

We found significant correlation between the aberrant PRM ratio (PRM2 under expression) and lower YBX2 mRNA content in testicular biopsies of azoospermic men compared to controls, which suggested that downregulation of the YBX2 gene might be involved in PRM2 under expression. These molecules could be useful biomarkers for predicting male infertility.

Polymorphisms in Protamine 1 and Protamine 2 predict the risk of male infertility: a meta-analysis

Several studies have investigated the association between polymorphisms in protamine 1 and 2 genes and male infertility risk, with inconsistent results to date. This meta-analysis based on the 13 published case-control studies, including 7350 cases and 6167 controls, was performed to further establish the potential association between the 6 common single nucleotide polymorphisms (rs35576928, rs737008, rs35262993, rs2301365, rs1646022, rs2070923) in protamines 1 and 2 and male infertility. The -190C > A (rs2301365) polymorphism was identified as a risk factor for male infertility under all models. Interestingly, rs1646022 and rs737008 polymorphisms exerted protective effects against male sterility in Asian and population-based under some models. No associations between the remaining SNPs and male sterility were observed.

Sexual selection on protamine and transition nuclear protein expression in mouse species

Post-copulatory sexual selection in the form of sperm competition is known to influence the evolution of male reproductive proteins in mammals. The relationship between sperm competition and regulatory evolution, however, remains to be explored. Protamines and transition nuclear proteins are involved in the condensation of sperm chromatin and are expected to affect the shape of the sperm head. A hydrodynamically efficient head allows for fast swimming velocity and, therefore, more competitive sperm. Previous comparative studies in rodents have documented a significant association between the level of sperm competition (as measured by relative testes mass) and DNA sequence evolution in both the coding and promoter sequences of protamine 2. Here, we investigate the influence of sexual selection on protamine and transition nuclear protein mRNA expression in the testes of eight mouse species that differ widely in levels of sperm competition. We also examined the relationship between relative gene expression levels and sperm head shape, assessed using geometric morphometrics. We found that species with higher levels of sperm competition express less protamine 2 in relation to protamine 1 and transition nuclear proteins. Moreover, there was a significant association between relative protamine 2 expression and sperm head shape. Reduction in the relative abundance of protamine 2 may increase the competitive ability of sperm in mice, possibly by affecting sperm head shape. Changes in gene regulatory sequences thus seem to be the basis of the evolutionary response to sexual selection in these proteins.

Biomarkers of chemotherapy-induced testicular damage

Increasing numbers of men are having or wanting children after chemotherapy treatment. This can be attributed to improvements in cancer therapies that increase survival. However, a side effect of most chemotherapy drugs is disruption of spermatogenesis and a drastic reduction in sperm count and quality. Although many men eventually recover reproductive function, as indicated by normal semen analyses, there is no clinical test that can assess sperm quality at a high level of sensitivity. Sperm fluorescent in situ hybridization (i.e., FISH) and several different tests for deoxyribonucleic acid (DNA) fragmentation have been used infrequently in clinical assessment. Animal models of chemotherapy-induced testicular damage are currently being used to identify potential molecular biomarkers that may be translatable to humans-these include sperm messenger RNAs, microRNAs, histone modifications, and DNA methylation patterns. Changes in these molecular measurements are quantitative and sensitive, potentially making them important clinical biomarkers of testicular function after chemotherapy treatment.

MicroRNA-122 influences the development of sperm abnormalities from human induced pluripotent stem cells by regulating TNP2 expression

Sperm abnormalities are one of the main factors responsible for male infertility; however, their pathogenesis remains unclear. The role of microRNAs in the development of sperm abnormalities in infertile men has not yet been investigated. Here, we used human induced pluripotent stem cells to investigate the influence of miR-122 expression on the differentiation of these cells into spermatozoa-like cells in vitro. After induction, mutant miR-122-transfected cells formed spermatozoa-like cells. Flow cytometry of DNA content revealed a significant increase in the haploid cell population in spermatozoa-like cells derived from mutant miR-122-transfected cells as compared to those derived from miR-122-transfected cells. During induction, TNP2 and protamine mRNA and protein levels were significantly higher in mutant miR-122-transfected cells than in miR-122-transfected cells. High-throughput isobaric tags for relative and absolute quantification were used to identify and quantify the different protein expression levels in miR-122- and mutant miR-122-transfected cells. Among all the proteins analyzed, the expression of lipoproteins, for example, APOB and APOA1, showed the most significant difference between the two groups. This study illustrates that miR-122 expression is associated with abnormal sperm development. MiR-122 may influence spermatozoa-like cells by suppressing TNP2 expression and inhibiting the expression of proteins associated with sperm development.

Protamine-1 and -2 polymorphisms and gene expression in male infertility: an Italian study

BACKGROUND

Correct histone/protamine replacement is an important stage in chromatin condensation during spermiogenesis in humans. There are two types of protamines: protamine 1 (P1) and the protamine 2 family (P2, P3, and P4), coded by the genes PRM1 and PRM2.

AIM

We analyze the sequences and gene expression of PRM1 and PRM2 and their relationship with defective spermatogenesis.

MATERIALS AND METHODS

Sequence analysis was carried out on 163 patients attending our laboratory for analysis of seminal fluid. Patients were divided into three groups: normozoospermic (53), teratozoospermic (60), and azoospermic (50). Gene expression was analyzed in seven patients with azoospermia and one with cryptozoospermia.

RESULTS

Seven single nuclotide polymorphisms (SNP) were identified: G54A, G102T and C230A for PRM1, and C246T, G288C, G298C and C373A for PRM2. For C230A, the CA genotype was present in 38% of teratozoospermic vs 55% of normozoospermic and 64% of azoospermic patients; for C373A, CA was found in 37% of teratozoospermic vs 47% of normozoospermic and 64% of azoospermic patients. In contrast, for G298C, GC was more common in the teratozoospermic (63%) than in the normozoospermic (49%) or azoospermic (48%) groups. These differences could suggest a greater susceptibility of these patients to abnormal sperm morphology. In five patients the levels of transcripts were reduced with respect to the control.

CONCLUSION

These data suggest that premeiotic arrest is associated with extremely reduced protamine expression. New studies of both PRM1 and PRM2 and their mRNA expression could help us better understand the molecular mechanisms underlying the protamine transcription and translation processes.

PRM1 variant rs35576928 (Arg>Ser) is associated with defective spermatogenesis in the Chinese Han population

Protamine genes play important roles in DNA packaging within the sperm nucleus. In order to evaluate the association of PRM1, PRM2, KIT and KITLG variants with susceptibility to severely defective spermatogenesis, 309 male infertility patients (199 cases with non-obstructive azoospermia and 110 cases with severe oligozoospermia) and 377 controls were recruited in the Chinese Han population. This study genotyped 38 single-nucleotide polymorphisms (SNP) in PRM1, PRM2, KIT and KITLG using Sequenom iplex. The results showed that PRM1 variant rs35576928 (p.R34S) was significantly associated with severe oligozoospermia and played a protective role against the disease (P=0.0079, Bonferroni correction, OR 0.426). The dominant model (variant-containing genotypes) of the SNP was confirmed to protect against the occurrence of oligozoospermia (P=0.0078, Bonferroni correction, OR 0.387). Haplotype analysis of PRM1 and PRM2 in combination exhibited that haplotype TACCGGC exhibited a significant protective effect against the occurrence of oligozoospermia when compared with controls (P=0.002, Bonferroni correction, OR 0.602). Haplotype TACCTGC was strongly associated with risk of the clinical phenotype severe oligozoospermia (P=0.002, Bonferroni correction, OR 2.716). The findings indicated that PRM1 variant rs35576928 (p.R34S) was associated with severely defective spermatogenesis in the Chinese Han population. Male spermatogenic failure may be associated with gene variants. We demonstrated whether such genetic variation of PRM1 and PRM2 affected clinicopathological characteristics and conferred susceptibility to this entity. In this study, we found that PRM1 variant rs35576928 (Arg>Ser) played a protective role against severe oligozoospermia. The dominant model analysis (variant-containing genotypes) confirmed that the SNP was a risk factor of a spermatogenesis defect. Haplotype analysis of PRM1 and PRM2 showed that TACCGGC was a common factor protecting against severe oligozoospermia, while the haplotype TACCTGC was strongly associated with the risk of the severe oligozoospmeria. Our findings indicate that the PRM1 variant rs35576928 (Arg>Ser) is associated with spermatogenesis defect in the Chinese Han population.

Impact of protamine transcripts and their proteins on the quality and fertilization ability of sperm and the development of preimplantation embryos

Protamine 1 (PRM1) and 2 (PRM2) are major nuclear proteins in spermatozoa known to bind to chromatin during early spermatogenesis. The aim of this study was to evaluate the impact of protamine transcripts and proteins on human spermatozoa and their fertilization ability as well as the development of preimplantation embryos. Oocytes selected from 92 patients were fertilized in vitro (IVF) using their partners' sperm after evaluating its concentration, motility and morphology. Reverse transcription and real-time quantitative PCR (RQ-PCR) were applied to determine protamine mRNA level, while sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting were used to quantify the protamine protein concentration. Next, protamine mRNA and protein levels were correlated with sperm concentration, motility and morphology as well as with the fertilization ability of mature spermatozoa and embryos of different quality obtained from the IVF program. A significant correlation has been found between protamine transcripts/proteins and: sperm concentration, progressive sperm motility, sperm fertilization ability as well as embryo quality. Protamine transcripts and proteins contribute to the quality of spermatozoa, successful fertilization and may have a significant influence on the development of preimplantation embryos.

Use of diagnostic testing to detect infertility

The evaluation of the infertile male continues to be a clinical challenge of increasing significance with considerable emotional and financial burdens. Many physiological, environmental and genetic factors are implicated; however, the etiology of suboptimal semen quality is poorly understood. This review focuses on the diagnostic testing currently available, as well as future directions that will be helpful for the practicing urologist and other clinicians to fully evaluate the infertile male.

The use of transgenic mouse models in the study of male infertility

Over the past few decades with the rapid advances in embryo and embryonic stem cell manipulation techniques, transgenic mouse models have emerged as a powerful tool for the study of gene function and complex diseases including male infertility. In this review we give a brief history of the development of tools for the production of transgenic mouse models. This spans the advances from early pronuclear injection to the use of targeted embryonic stem cells to produce gene targeted, conditional, and inducible knockout mouse models. Lastly we provide a few examples to illustrate the utility of mouse models in the study of male infertility.

The human sperm epigenome and its potential role in embryonic development

Along with many of the genome-wide transitions in chromatin composition throughout spermatogenesis, epigenetic modifications on histone tails and DNA are continuously modified to ensure stage specific gene expression in the maturing spermatid. Recent findings have suggested that the repertoire of epigenetic modifications in the mature sperm may have a potential role in the developing embryo and alterations in the epigenetic profile have been associated with infertility. These changes include DNA demethylation and the retention of modified histones at important developmental, signaling and micro-RNA genes, which resemble the epigenetic state of an embryonic stem cell. This review assesses the significance of epigenetic changes during spermatogenesis, and provides insight on recent associations made between altered epigenetic profiles in the mature sperm and its relationship to infertility.

A common haplotype of protamine 1 and 2 genes is associated with higher sperm counts

Sperm chromatin compaction in the sperm head is achieved when histones are replaced by protamines during spermatogenesis. Haploinsufficiency of the protamine 1 (PRM1) or PRM2 gene causes infertility in mice. However, the published data remain inconclusive about a role of PRM1/2 variants in male infertility and their association with semen parameters. By full sequence analysis, we assessed the frequency of sequence variations in PRM1 and PRM2 in three groups of Caucasian patients with idiopathic teratozoospermia and normal (n = 88) or reduced sperm concentration (n = 83) and in men with a high percentage of normal sperm morphology and normal concentrations (n = 77). Two rare (c.54G>A and c.102G>T) and one common SNP (c.230A>C) were identified in PRM1. In PRM2, some rare heterozygous mutations and the two common intronic SNPs 298G>C and 373C>A were detected. None of the PRM1/2 variants was associated with teratozoospermia or individually with other semen parameters. However, significant linkage disequilibrium was detected between the common SNPs of PRM1 and PRM2 which formed haplotypes. Analysis of the pooled group (n = 248) revealed that homozygous carriers of the common haplotype ACC had a twofold higher sperm concentration and count than men lacking this haplotype, with sperm counts of heterozygotes for ACC being midway between the homozygotes. This markedly decreased sperm output might either be caused by spermatozoa lacking the ACC haplotype not being viable, or subject to negative selection. In addition, a significant deviation from Hardy-Weinberg-Equilibrium of these SNPs might indicate natural selection in favour of the ACC allele which leads to higher sperm output and therefore better fertility. In conclusion, for the first time we describe an association of a common haplotype formed by PRM1 and PRM2 with sperm output in a large group of men.

Two-stage genome-wide association study identifies integrin beta 5 as having potential role in bull fertility

Background

Fertility is one of the most critical factors controlling biological and financial performance of animal production systems and genetic improvement of lines. The objective of this study was to identify molecular defects in the sperm that are responsible for uncompensable fertility in Holstein bulls. We performed a comprehensive genome wide analysis of single nucleotide polymorphisms (SNP) for bull fertility followed by a second-stage replication in additional bulls for a restricted set of markers.

Results

In the Phase I association study, we genotyped the genomic sperm DNA of 10 low-fertility and 10 high-fertility bulls using Bovine SNP Gene Chips containing approximately 10,000 random SNP markers. In these animals, 8,207 markers were found to be polymorphic, 97 of which were significantly associated with fertility (p < 0.01). In the Phase II study, we tested the four most significant SNP from the Phase I study in 101 low-fertility and 100 high-fertility bulls, with two SNPs (rs29024867 and rs41257187) significantly replicated. Rs29024867 corresponds to a nucleotide change of C → G 2,190 bp 3' of the collagen type I alpha 2 gene on chromosome 4, while the rs41257187 (C → T) is in the coding region of integrin beta 5 gene on chromosome 1. The SNP rs41257187 induces a synonymous (Proline → Proline), suggesting disequilibrium with the true causative locus (i), but we found that the incubation of bull spermatozoa with integrin beta 5 antibodies significantly decreased the ability to fertilize oocytes. Our findings suggest that the bovine sperm integrin beta 5 protein plays a role during fertilization and could serve as a positional or functional marker of bull fertility.

Conclusion

We have identified molecular markers associated with bull fertility and established that at least one of the genes harboring such variation has a role in fertility. The findings are important in understanding mechanisms of uncompensatory infertility in bulls, and in other male mammals. The findings set the stage for more hypothesis-driven research aimed at discovering the role of variation in the genome that affect fertility and that can be used to identify molecular mechanisms of development.

Identification of genetic variation in the 5' and 3' non-coding regions of the protamine genes in patients with protamine deregulation

Deregulation of sperm nuclear protamine ratio (P1/P2) has been shown to correlate with male factor infertility in humans, but the cause of this abnormal protein expression has yet to be identified. Recent studies have shown that there is little genetic variability in the coding regions of either of the protamine gene sequences. However, these studies did not investigate the 5' or 3' non-coding regions of these genes for mutations that might account for changes in the transcriptional or translational regulation of the protamines. In an effort to determine if genetic variation in these non-coding regions may account for aberrant protamine expression, we have sequenced the 5' and 3' untranslated regions (UTRs) of both protamine 1 (P1) and protamine 2 (P2) genes in a population of infertile men with protamine deregulation, men presenting for infertility work-up with normal protamine ratios, and a population of unrelated, fertile men from the Utah Genetic Reference Project (UGRP). This analysis has identified 14 single nucleotide polymorphisms (SNPs), of which 13 were novel SNPs in the UTRs of P1 and P2, and verified the existence of a variable length repeat (VLR), GAn, in the P2 5' region. The SNP frequencies and VLR allelic frequencies did not achieve statistical significance between the populations, however, one of the SNPs identified in the 3' UTR of protamine 2 was found at a low frequency in the abnormal protamine patients, but was completely absent in men with verified normal protamine ratio and donors of known fertility. In conclusion, a number of SNPs have been reported in the protamine genes and the untranslated regions, however, these gene variants do not appear to be responsible for protamine deficiency. Hence, the underlying cause for aberrant protamine expression may possibly be due to abnormalities in candidate spermatogenic transcriptional/translational regulators, post-translational modifiers, or as-of-yet unidentified factors affecting the testicular environment.

Sequence alterations in the YBX2 gene are associated with male factor infertility

OBJECTIVE

To investigate YBX2 gene alterations in men with severe defects in spermatogenesis, including azoospermia or severe oligozoospermia, and protamine deregulation. MSY2 has been identified as a central component in the regulation of spermatogenesis in mice, but the potential role of its human orthologue, YBX2 or "Contrin," in human infertility is not known.

DESIGN

A prospective cohort study.

SETTING

University infertility clinic and associated research laboratory.

PATIENT(S)

A total of 288 men were evaluated. Diagnoses were made of complete azoospermia, severe oligozoospermia, and protamine deregulation, or men were of known paternity.

INTERVENTION(S)

Deoxyribonucleic acid (from peripheral blood) and semen samples were collected and analyzed for gene mutations and semen parameters respectively.

MAIN OUTCOME MEASURE(S)

YBX2 gene alterations.

RESULT(S)

YBX2 sequence analysis revealed 15 polymorphic sites, of which seven polymorphisms were present at a statistically higher frequency in one or both of the patient populations than in controls. Of these seven, two resulted in an amino acid substitution in the highly conserved cold shock domain and one resulted in a highly significant synonymous change in exon 8 of infertile patients. The frequency of single nucleotide polymorphisms was significantly elevated in patients with infertility, particularly in men with abnormal protamine expression.

CONCLUSION(S)

These data indicate a significant association between gene alterations in the YBX2 gene and abnormal spermatogenesis in humans, including a potential role in altering protamine expression, and implicate YBX2 gene alterations as a potential cause of male factor infertility.

The aetiology of sperm protamine abnormalities and their potential impact on the sperm epigenome

During the elongating spermatid stage of spermatogenesis, there is a step-wise replacement of nuclear histones with protamines 1 and 2. In fertile men, the ratio of protamine 1/protamine 2 (P1/P2) is within the narrow range of 0.8-1.2. Ratios above or below that range are associated with infertility, exhibiting a wide range of defects including decreased sperm counts, morphology, fertilization ability, and embryo implantation capacity. In this review, we highlight studies evaluating potential causes of abnormal protamine expression, including the sequencing of genes relevant to protamine expression in both affected patients and controls. While the variants of the protamine genes themselves do not appear to be responsible for most observed defects, variants of the Contrin gene, a transcription factor and translation repressor, appear to be contributory to some cases of abnormal expression. Additionally, we explore the potential effects of abnormal protamine replacement on the epigenome of human sperm. Ongoing studies are evaluating the role of retained histones and DNA methylation in sperm, which may be affected in sperm with aberrant protamine replacement. This important area of epigenetic research has profound clinical implications.

Gene polymorphisms and male infertility--a meta-analysis and literature review

Many genetic polymorphisms have been studied extensively to elucidate their role in the pathophysiology of male infertility. This article presents a review of the literature following a thorough search of PubMed, a compilation of meta-analyses of studies reporting an association with male fertility where the population(s) could be clearly identified as fertile and/or infertile, and a summary of all polymorphisms that have been investigated in single case-control studies to date. The meta-analyses revealed significant associations between polymorphism and male fertility only for AZF gr/gr deletions (OR 1.81, 1.46-2.24 CI, P<0.00001) and MTHFR 677C-->T (OR 1.39, 1.15-2.69 95% CI, P=0.0006) but not for POLG, DAZL, USP26 or FSHR. The influence of CAG repeat length in AR remains open and debated. Genes encoding nuclear proteins (PRM1/2, TNP1/2) and ER1 are possible candidates for further examination, while the role of TAF7L remains unclear. Polymorphisms in 16 other genes have been investigated in single studies, but the results remain doubtful due to often small and heterogeneous cohorts and in the absence of independent replications. The genetic studies performed so far emphasize the complexity of male infertility as a presumably polygenetic trait amended by environmental, lifestyle or occupational factors.

Genetic risk factors in male infertility

The etiopathogenesis of testicular failure remains unknown in about half of the cases and is referred to as "idiopathic infertility". "Idiopathic" testicular failure is of probable genetic origin since the number of genes involved in human spermatogenesis is likely thousands and only a small proportion of them have been identified and screened in infertile men. In parallel with studies aimed to identify mutations with a clear cause-effect relationship in spermatogenesis candidate genes, there is an increasing interest towards genetic susceptibility factors to male infertility. Despite many efforts, only a few clinically relevant polymorphisms have been identified. This is mainly related to the multifactorial nature of male infertility and to the inappropriate study design of the majority of the studies. The most promising polymorphisms are in genes involved in the endocrine regulation of spermatogenesis and on the Y chromosome, the "gr/gr" deletions. Polymorphisms are generally considered as co-factors. Their final effect on testis function and fertility is probably modulated by the genetic background of each individual and/or by the presence of certain environmental factors. In this review, recent findings concerning some of the most widely studied polymorphisms and male infertility will be discussed.

Organization of chromosomes in spermatozoa: an additional layer of epigenetic information?

Elaborate non-random organization of human sperm chromosomes at different structural levels, starting from the DNA packing by protamines up to the higher-order chromosome configuration and nuclear positioning of chromosome territories, has been discovered. Here, we put forward a hypothesis that the unique genome architecture in sperm provides a mechanism for orchestrated unpacking and ordered activation of the male genome during fertilization, thus offering an additional level of epigenetic information that will be deciphered in the descendant cells.

Mutations in the protamine 1 gene associated with male infertility

In elongating spermatids, human sperm chromatin undergoes a complex compaction in which the transition proteins are extensively replaced by the protamine proteins. Several human studies demonstrate that expression of the protamine proteins is altered in some men with male infertility. For this study, we screened the PRM1 (protamine 1) gene for mutations in a large cohort of 281 men seeking infertility treatment. We identified the c.102G>T transversion that results in an p.Arg34Ser amino acid change in two men. One of these patients presented with oligozoospermia associated with increased sperm DNA fragmentation. The second individual was normospermic but together with his partner sought treatment for idiopathic couple infertility. We also identified a novel missense mutation (c.119G>A, p.Cys40Tyr) in a man with oligoasthenozoospermia. These mutations were not observed in control populations. Interestingly, we also detected variants both 5' and 3' to the PRM1 open-reading frame specifically in infertile individuals. Four individuals with unexplained severe oligozoospermia were heterozygote for a c.-107G>C change that is located at -15 bp from the transcription initiation site of the gene. This mutation may influence PRM1 expression. In addition, a c.*51G>C variant was detected in the 3'UTR of PRM1 specifically in a man with severe oligoasthenozoospermia.