Spermatozoal RNA as Reservoir, Marker and Carrier of Epigenetic Information: Implications for Cloning

Significance and Relevance of Spermatozoal RNAs to Male Fertility in Livestock

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

The epigenetic alterations of human sperm cells caused by heroin use disorder

The molecular mechanisms of drug use on sexual health are largely unknown. We investigated, the relationship between heroin use disorder and epigenetic factors influencing histone acetylation in sperm cells. The volunteers included twenty-four 20- to 50-year-old men with a normal spermogram who did not consume any drugs and twenty-four age- to BMI-matched men who consume only the drug heroin for more than last four months. HDAC1 and HDAC11 mRNA expression levels in spermatozoa and miR-34c-5p and miR-125b-5p expression levels in seminal plasma were measured. The heroin-user group showed significantly increased white blood cell counts and decreased sperm motility and survival rates (8.61 ± 1.73, 21.50 ± 3.11, 69.90 ± 4.69 respectively) as compared to the control group (1.49 ± 0.32, 38.82 ± 3.05, 87.50 ± 0.99 respectively) (p ≤ .001). An increase in DNA fragmentation index (DFI) (heroin-user group: 41.93 ± 6.59% and control group: 10.14 ± 1.43%, p = .003), a change in frequency of HDAC1 (heroin-user group: 1.69 ± 0.55 and control group: 0.45 ± 0.14, p = .045) and HDAC11 (heroin-user group: 0.29 ± 0.13 and control group: 2.36 ± 0.76, p = .019) in spermatozoa and a significant decrease in seminal miR-125b-5p abundance (heroin-user group: 0.37 ± 0.11 and control group: 1.59 ± 0.47, p = .028) were reported in heroin consumers. Heroin use can lead to male infertility by causing leukocytospermia, asthenozoospermia, DFI elevation in sperm cells and alterations in seminal RNA profile.

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

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

Integrative DNA methylation and gene expression analyses identify DNA packaging and epigenetic regulatory genes associated with low motility sperm

Background

In previous studies using candidate gene approaches, low sperm count (oligospermia) has been associated with altered sperm mRNA content and DNA methylation in both imprinted and non-imprinted genes. We performed a genome-wide analysis of sperm DNA methylation and mRNA content to test for associations with sperm function.

Methods and Results

Sperm DNA and mRNA were isolated from 21 men with a range of semen parameters presenting to a tertiary male reproductive health clinic. DNA methylation was measured with the Illumina Infinium array at 27,578 CpG loci. Unsupervised clustering of methylation data differentiated the 21 sperm samples by their motility values. Recursively partitioned mixture modeling (RPMM) of methylation data resulted in four distinct methylation profiles that were significantly associated with sperm motility (P = 0.01). Linear models of microarray analysis (LIMMA) was performed based on motility and identified 9,189 CpG loci with significantly altered methylation (Q<0.05) in the low motility samples. In addition, the majority of these disrupted CpG loci (80%) were hypomethylated. Of the aberrantly methylated CpGs, 194 were associated with imprinted genes and were almost equally distributed into hypermethylated (predominantly paternally expressed) and hypomethylated (predominantly maternally expressed) groups. Sperm mRNA was measured with the Human Gene 1.0 ST Affymetrix GeneChip Array. LIMMA analysis identified 20 candidate transcripts as differentially present in low motility sperm, including HDAC1 (NCBI 3065), SIRT3 (NCBI 23410), and DNMT3A (NCBI 1788). There was a trend among altered expression of these epigenetic regulatory genes and RPMM DNA methylation class.

Conclusions

Using integrative genome-wide approaches we identified CpG methylation profiles and mRNA alterations associated with low sperm motility.

Pregnancy-specific {beta}-1-glycoprotein 1 and human leukocyte antigen-E mRNA in human sperm: differential expression in fertile and infertile men and evidence of a possible functional role during early development

BACKGROUND

Mature spermatozoa contain thousands of mRNA transcripts. It has been recently shown that human sperm can deliver RNA into the oocyte, suggesting that mRNAs might have a role before or after fertilization. Human embryos express PSG1 (pregnancy-specific beta-1-glycoprotein 1) and HLA-E (human leukocyte antigen-E), molecules playing a role in implantation and early development. We compared PSG1 and HLA-E sperm mRNA levels in fertile and infertile men and we tested the hypothesis that these transcripts are selectively retained in the newly formed zygote.

METHODS

Real-time RT-PCR was used to analyze sperm mRNA levels (n = 11 fertile, n = 31 infertile patients) of PSG1, HLA-E and PRM2 (protamine 2). The presence of PSG1 and HLA-E proteins was evaluated by western blot in sperm protein extracts (n = 3). Using ICSI of human sperm into hamster oocytes we evaluated the permanence of these mRNAs at different time points (n = 10 for each time) after fertilization.

RESULTS

PSG1, HLA-E and PRM2 transcripts were demonstrated in ejaculated sperm. The fertile group showed significantly higher levels of PSG1 and HLA-E mRNA (both P < 0.05) than the infertile group, whereas PRM2 levels were not significantly different. However, PSG1 and HLA-E proteins were not found in ejaculated sperm. Following ICSI, PRM2 was undetectable after fertilization; conversely, PSG1 and HLA-E transcripts remained detectable for at least 24 h of zygotic development.

CONCLUSIONS

We provide new evidence that indicates that human sperm deliver transcripts that may have a role in early embryo development and decreased levels of these transcripts may be associated with infertility.

Mitochondria in mammalian sperm physiology and pathology: a review

While, for a long time, the role of mitochondria in sperm physiology and pathology has been largely ignored, recent research points out the mitochondria as a major organelle with key roles in sperm function both under physiological and biotechnological conditions. This paper briefly reviews these novel findings regarding the role of mitochondria in sperm, paying special attention to the most practical, readily applicable, aspects of the topic such as their role as a major source of the sublethal damage that sperm experiments after cryopreservation.