ARRDC5 expression is conserved in mammalian testes and required for normal sperm morphogenesis

Genomic, transcriptomic and epigenomic analysis towards the understanding of porcine semen quality traits. Past, current and future trends

The importance of boar reproductive traits, including semen quality, in the sustainability of pig production system is increasingly being acknowledged by academic and industrial sectors. Research is needed to understand the biology and genetic components underlying these traits so that they can be incorporated into selection schemes and managerial decisions. This article reviews our current understanding of genome biology and technologies for genome, transcriptome and epigenome analysis which now facilitate the identification of causal variants affecting phenotypes more than ever before. Genetic and transcriptomic analysis of candidate genes, Genome-Wide Association Studies, expression microarrays, RNA-Seq of coding and noncoding genes and epigenomic evaluations have been conducted to profile the molecular makeups of pig sperm. These studies have provided insightful information for a several semen-related parameters. Nonetheless, this research is still incipient. The spermatozoon harbors a reduced transcriptome and highly modified epigenome, and it is assumed to be transcriptionally silent for nuclear gene expression. For this reason, the extent to which the sperm's RNA and epigenome recapitulate sperm biology and function is unclear. Hence, we anticipate that single-cell level analyses of the testicle and other male reproductive organs, which can reveal active transcription and epigenomic profiles in cells influencing sperm quality, will gain popularity and markedly advance our understanding of sperm-related traits. Future research will delve deeper into sperm fertility, boar resilience to environmental changes or harsh conditions, especially in the context of global warming, and also in transgenerational inheritance and how the environment influences the sperm transcriptome and epigenome.

Elevated Id2 expression causes defective meiosis and spermatogenesis in mice

BACKGROUND

Inhibitors of DNA binding (ID) proteins mainly inhibit gene expression and regulate cell fate decisions by interacting with E-proteins. All four ID proteins (ID1-4) are present in the testis, and ID4 has a particularly important role in spermatogonial stem cell fate determination. Several lines of evidence indicate that ID proteins are involved in meiosis; however, functional experiments have not been conducted to validate this observation.

RESULTS

In this study, we report that ID2 is enriched in spermatocytes and that forced ID2 expression in germ cells causes defects in spermatogenesis. A detailed analysis demonstrated that Id2 overexpression (Id2 OE) decreased the total number of spermatogonia and changed the dynamics of meiosis progression. Specifically, spermatocytes were enriched in the zygotene stage, and the proportion of pachytene spermatocytes was significantly decreased, indicating defects in the zygotene-pachytene transition. The number of MLH1-positive foci per cell was decreased in pachytene spermatocytes from Id2 OE testes, suggesting abnormalities in recombination. Transcriptome analysis revealed that forced Id2 expression changed the expression of a list of genes mainly associated with meiosis and spermatid development.

CONCLUSIONS

ID2 protein is expressed in spermatocytes, and its genetic ablation in the germline does not affect spermatogenesis, likely due to genetic compensation of its family members. However, forced Id2 expression changes meiosis progression and causes defects in spermiogenesis. These data provide important evidence that ID proteins play pivotal roles in male meiosis and spermatid development.

The uniqueness of on-demand male contraception

Because nearly half of pregnancies worldwide are unintended, available contraceptive methods are inadequate. Moreover, due to the striking imbalance between contraceptive options available for men compared to the myriad of options available to women, there is an urgent need for new methods of contraception for men. This review summarizes ongoing efforts to develop male contraceptives highlighting the unique aspects particular to on-demand male contraception, where a man takes a contraceptive only when and as often as needed.

Exploring the biological roles of DHX36, a DNA/RNA G-quadruplex helicase, highlights functions in male infertility: A comprehensive review

It is estimated that 15 % of couples at reproductive age worldwide suffer from infertility, approximately 50 % of cases are caused by male factors. Significant progress has been made in the diagnosis and treatment of male infertility through assisted reproductive technology and molecular genetics methods. However, there is still inadequate research on the underlying mechanisms of gene regulation in the process of spermatogenesis. Guanine-quadruplexes (G4s) are a class of non-canonical secondary structures of nucleic acid commonly found in genomes and RNAs that play important roles in various biological processes. Interestingly, the DEAH-box helicase 36 (DHX36) displays high specificity for the G4s which can unwind both DNA G4s and RNA G4s enzymatically and is highly expressed in testis, thereby regulating multiple cellular functions including transcription, pre-mRNA splicing, translation, telomere maintenance, genomic stability, and RNA metabolism in development and male infertility. This review provides an overview of the roles of G4s and DHX36 in reproduction and development. We mainly focus on the potential role of DHX36 in male infertility. We also discuss possible future research directions regarding the mechanism of spermatogenesis mediated by DHX36 through G4s in spermatogenesis-related genes and provide new targets for gene therapy of male infertility.

METTL3-m6A-SIRT1 axis affects autophagic flux contributing to PM2.5-induced inhibition of testosterone production in Leydig cells

Epidemiological studies have found that long-term inhalation of PM2.5 is closely related to spermatogenesis disorders and infertility, but the underlying molecular mechanism is still unidentified. Testosterone, an essential reproductive hormone produced by Leydig cells, whose synthesis is disrupted by multiple environmental pollutants. In the current study, we explored the role of METTL3-m6A-SIRT1 axis-mediated abnormal autophagy in PM2.5-induced inhibition of testosterone production in in vivo and in vitro models. Our in vivo findings shown that long-term inhalation of PM2.5 decreased sperm count, increased sperm deformity rates, and altered testicular interstitial morphology accompanied by reduced testosterone in serum and testes. Further, data from the in vitro model displayed that exposure to PM2.5 caused an increase in m6A modification and METTL3 levels, followed by a decrease in testosterone levels and autophagy dysfunction in Leydig cells. The knockdown of METTL3 promotes autophagy flux and testosterone production in Leydig cells. Mechanistically, PM2.5 increased METTL3-induced m6A modification of SIRT1 mRNA in Leydig cells, bringing about abnormal autophagy. Subsequently, administration of SRT1720 (a SIRT1 activator) enhanced autophagy and further promoted testosterone biosynthesis. Collectively, our discoveries indicate that METTL3-m6A-SIRT1 axis-mediated autophagic flux contributes to PM2.5-induced inhibition of testosterone biosynthesis. This research offers a novel viewpoint on the mechanism of male reproductive injury following PM2.5 exposure.

Spem2, a novel testis-enriched gene, is required for spermiogenesis and fertilization in mice

Spermiogenesis is considered to be crucial for the production of haploid spermatozoa with normal morphology, structure and function, but the mechanisms underlying this process remain largely unclear. Here, we demonstrate that SPEM family member 2 (Spem2), as a novel testis-enriched gene, is essential for spermiogenesis and male fertility. Spem2 is predominantly expressed in the haploid male germ cells and is highly conserved across mammals. Mice deficient for Spem2 develop male infertility associated with spermiogenesis impairment. Specifically, the insufficient sperm individualization, failure of excess cytoplasm shedding, and defects in acrosome formation are evident in Spem2-null sperm. Sperm counts and motility are also significantly reduced compared to controls. In vivo fertilization assays have shown that Spem2-null sperm are unable to fertilize oocytes, possibly due to their impaired ability to migrate from the uterus into the oviduct. However, the infertility of Spem2-/- males cannot be rescued by in vitro fertilization, suggesting that defective sperm-egg interaction may also be a contributing factor. Furthermore, SPEM2 is detected to interact with ZPBP, PRSS21, PRSS54, PRSS55, ADAM2 and ADAM3 and is also required for their processing and maturation in epididymal sperm. Our findings establish SPEM2 as an essential regulator of spermiogenesis and fertilization in mice, possibly in mammals including humans. Understanding the molecular role of SPEM2 could provide new insights into future therapeutic treatment of human male infertility and development of non-hormonal male contraceptives.

ARRDC5 deficiency impairs spermatogenesis by affecting SUN5 and NDC1

Sperm with normal morphology and motility are essential for successful fertilization, and the strong attachment of the sperm head-tail coupling apparatus to the nuclear envelope during spermatogenesis is required to ensure the integrity of sperm for capacitation and fertilization. Here, we report that Arrdc5 is associated with spermatogenesis. The Arrdc5 knockout mouse model showed male infertility characterized by a high bent-head rate and reduced motility in sperm, which led to capacitation defects and subsequent fertilization failure. Through mass spectrometry, we found that ARRDC5 affects spermatogenesis by affecting NDC1 and SUN5. We further found that ARRDC5 might affect the vesicle-trafficking protein SEC22A-mediated transport and localization of NDC1, SUN5 and other head-tail coupling apparatus-related proteins that are responsible for initiating the attachment of the sperm head and tail. We finally performed intracytoplasmic sperm injection as a way to explore therapeutic strategies. Our findings demonstrate the essential role and the underlying molecular mechanism of ARRDC5 in anchoring the sperm head to the tail during spermatogenesis.

The α-arrestin SUP-13/ARRD-15 promotes isoform turnover of actin-interacting protein 1 in Caenorhabditis elegans striated muscle

Precise arrangement of actin, myosin, and other regulatory components in a sarcomeric pattern is critical for producing contractile forces in striated muscles. Actin-interacting protein 1 (AIP1), also known as WD-repeat protein 1 (WDR1), is one of essential factors that regulate sarcomeric assembly of actin filaments. In the nematode Caenorhabditis elegans, mutation in unc-78, encoding one of the two AIP1 isoforms, causes severe disorganization of sarcomeric actin filaments and near paralysis, but mutation in sup-13 suppresses the unc-78-mutant phenotypes to restore nearly normal sarcomeric actin organization and worm motility. Here, we identified that sup-13 is a nonsense allele of arrd-15 encoding an α-arrestin. The sup-13/arrd-15 mutation suppressed the phenotypes of unc-78 null mutant but required aipl-1 that encodes a second AIP1 isoform. aipl-1 was normally expressed highly in embryos and downregulated in mature muscle. However, in the sup-13/arrd-15 mutant, the AIPL-1 protein was maintained at high levels in adult muscle to compensate for the absence of the UNC-78 protein. The sup-13/arrd-15 mutation caused accumulation of ubiquitinated AIPL-1 protein, suggesting that a normal function of sup-13/arrd-15 is to enhance degradation of ubiquitinated AIPL-1, thereby promoting transition of AIP1 isoforms from AIPL-1 to UNC-78 in developing muscle. These results suggest that α-arrestin is a novel factor to promote isoform turnover by enhancing protein degradation.

α-tocopherol ameliorates copper II oxide nanoparticles-induced cytotoxic, biochemical, apoptotic, and genotoxic damages in the rainbow trout gonad cells-2 (RTG-2) culture

We investigated the effects of α-tocopherol on oxidative stress-caused damage caused by copper II oxide nanoparticles (CuO NPs) on Oncorhynchus mykiss gonadal cells (RTG-2) for 24 and 48 h. α-Tocopherol reversed the cell death and alterations in the expressions of genes such as sod1, gpx1a, gpx4b, and igf2 caused by CuO NPs; it also supported the expressions of cat, igf1, and gapdh genes caused by CuO NPs for 24 h and promoted alterations in the expressions of the sod2, gh1, and igf1 genes for 48 h. Additionally, α-tocopherol reversed the caspase 3/7 activity increased by CuO NPs for 24 h and supported it's decrease for 48 h. α-Tocopherol supported the increase in tail DNA (%) affected by CuO NPs for 24 h and reversed it for 48 h. Therefore, α-tocopherol may have the potential to protect against cellular alterations induced by CuO NPs in a time-dependent manner.