Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 1: Background to spermatogenesis, spermatogonia, and spermatocytes

Reproductive cytotoxic and genotoxic impact of polystyrene microplastic on Paracentrotus lividus spermatozoa

In recent decades, industrialization, intensive agriculture, and urban development have severely impacted marine environments, compromising the health of aquatic and terrestrial organisms. Inadequate disposal results in hundreds of tons of plastic products released annually into the environment, which degrade into microplastics (MPs), posing health risks due to their ability to biomagnify and bioaccumulate. Among these, polystyrene MPs (PS-MPs) are significant pollutants in marine ecosystems, widely studied for their reproductive toxicological effects. This research aimed to evaluate the reproductive cytotoxic and genotoxic effects of PS-MPs on sea urchin (Paracentrotus lividus) spermatozoa in vitro. Results showed that PS-MPs significantly reduced sperm viability and motility without altering morphology, and induced sperm DNA fragmentation mediated by reactive oxygen species production. Furthermore, head-to-head agglutination of the spermatozoa was observed exclusively in the sample treated with the plastic agents, indicating the ability of microplastics to adhere to the surface of sperm cells and form aggregates with microplastics on other sperm cells, thereby impeding movement and reducing reproductive potential. These findings suggest that PS-MPs can adversely affect the quality of sea urchin sperm, potentially impacting reproductive events.

The Planar Cell Polarity Protein Fat1 in Sertoli Cell Function

Fat (FAT atypical cadherin) and Dchs (Dachsous cadherin-related protein) in adjacent Sertoli:Sertoli, Sertoli:spermatid, and spermatid:spermatid interfaces create an important intercellular bridge whose adhesive function is in turn supported by Fjx1, a nonreceptor Ser/Thr protein kinase. This concept is derived from earlier studies of Drosophila, which has been confirmed in this and earlier reports as well. Herein, we use the approach of knockdown of Fat1 by RNAi using primary cultures of Sertoli cells that mimicked the blood-testis barrier (BTB) in vivo, and a series of coherent experiments including functional assays to monitor the Sertoli cell tight junction (TJ) permeability barrier and a functional in vitro TJ integrity assay to assess the role of Fat1 in the testis. It was shown that planar cell polarity (PCP) protein Fat1 affected Sertoli cell function through its modulation of actin and microtubule cytoskeletal function, altering their polymerization activity through the Fat1/Fjx1 complex. Furthermore, Fat1 is intimately associated with β-catenin and α-N-catenin, as well as with Prickle 1 of the Vangl1/Prickle 1 complex, another PCP core protein to support intercellular interactions to confer PCP. In summary, these findings support the notion that the Fat:Dchs and the Vangl2:Fzd PCP intercellular bridges are tightly associated with basal ES/TJ structural proteins to stabilize PCP function at the Sertoli:Sertoli, Sertoli:spermatid, and spermatid:spermatid interface to sustain spermatogenesis.

The rapidly evolving X-linked MIR-506 family fine-tunes spermatogenesis to enhance sperm competition

Despite rapid evolution across eutherian mammals, the X-linked MIR-506 family miRNAs are located in a region flanked by two highly conserved protein-coding genes (SLITRK2 and FMR1) on the X chromosome. Intriguingly, these miRNAs are predominantly expressed in the testis, suggesting a potential role in spermatogenesis and male fertility. Here, we report that the X-linked MIR-506 family miRNAs were derived from the MER91C DNA transposons. Selective inactivation of individual miRNAs or clusters caused no discernible defects, but simultaneous ablation of five clusters containing 19 members of the MIR-506 family led to reduced male fertility in mice. Despite normal sperm counts, motility, and morphology, the KO sperm were less competitive than wild-type sperm when subjected to a polyandrous mating scheme. Transcriptomic and bioinformatic analyses revealed that these X-linked MIR-506 family miRNAs, in addition to targeting a set of conserved genes, have more targets that are critical for spermatogenesis and embryonic development during evolution. Our data suggest that the MIR-506 family miRNAs function to enhance sperm competitiveness and reproductive fitness of the male by finetuning gene expression during spermatogenesis.

The Rapidly Evolving X-linked miR-506 Family Finetunes Spermatogenesis to Enhance Sperm Competition

Despite rapid evolution across eutherian mammals, the X-linked miR-506 family miRNAs are located in a region flanked by two highly conserved protein-coding genes (Slitrk2 and Fmr1) on the X chromosome. Intriguingly, these miRNAs are predominantly expressed in the testis, suggesting a potential role in spermatogenesis and male fertility. Here, we report that the X-linked miR-506 family miRNAs were derived from the MER91C DNA transposons. Selective inactivation of individual miRNAs or clusters caused no discernable defects, but simultaneous ablation of five clusters containing nineteen members of the miR-506 family led to reduced male fertility in mice. Despite normal sperm counts, motility and morphology, the KO sperm were less competitive than wild-type sperm when subjected to a polyandrous mating scheme. Transcriptomic and bioinformatic analyses revealed that these X-linked miR-506 family miRNAs, in addition to targeting a set of conserved genes, have more targets that are critical for spermatogenesis and embryonic development during evolution. Our data suggest that the miR-506 family miRNAs function to enhance sperm competitiveness and reproductive fitness of the male by finetuning gene expression during spermatogenesis.

Purification by STA-PUT Technique of Male Germ Cells from Single Mouse and RNA-Extraction for Transcriptomic Analysis

Transcriptomic analyses of germ cells at different stages of differentiation have shed light on the transcriptional and post-transcriptional mechanisms regulating gene expression that ensure the correct progression of spermatogenesis and male fertility. In this chapter, we describe a method to isolate meiotic and post-meiotic germ cells, based on gravimetric sedimentation, starting from a testicular germ cell suspension isolated from a single adult mouse. We also describe how to assess the purity and quality of the collected fractions of germ cells and how to optimize the extraction from these samples of RNA for subsequent RNA-sequencing experiment. In our experience, this protocol is suitable for germ cell isolation and transcriptomic analysis for mouse models with spermatogenic defects, overcoming the limits that reduced fertility poses to the obtaining of experimental animals.

CAMSAP1 role in orchestrating structure and dynamics of manchette microtubule minus-ends impacts male fertility during spermiogenesis

The manchette is a crucial transient structure involved in sperm development, with its composition and regulation still not fully understood. This study focused on investigating the roles of CAMSAP1 and CAMSAP2, microtubule (MT) minus-end binding proteins, in regulating manchette MTs, spermiogenesis, and male fertility. The loss of CAMSAP1, but not CAMSAP2, disrupts the well-orchestrated process of spermiogenesis, leading to abnormal manchette elongation and delayed removal, resulting in deformed sperm nuclei and tails resembling oligoasthenozoospermia symptoms. We investigated the underlying molecular mechanisms by purifying manchette assemblies and comparing them through proteomic analysis, and results showed that the absence of CAMSAP1 disrupted the proper localization of key proteins (CEP170 and KIF2A) at the manchette minus end, compromising its structural integrity and hindering MT depolymerization. These findings highlight the significance of maintaining homeostasis in manchette MT minus-ends for shaping manchette morphology during late spermiogenesis, offering insights into the molecular mechanisms underlying infertility and sperm abnormalities.

Transcriptomic analysis of mechanism underlying the effect of induced molting on semen quality and reproductive performance in aged Houdan roosters

The reproductive performance of breeder roosters has significant economic importance in the poultry industry. Breeder roosters have severely reduced semen quality with age and will be at risk of culling in the following years. In order to extend the use of breeder roosters, we drew on the induced molting model of hens and selected 35 Houdan roosters aged 50 wk for induced molting. By comparing the body weight, testicular weight, semen quality, and reproductive performance before and after induced molting, we found that induced molting could restore the body weight and testicular weight to the levels before molting (P > 0.05). At the same time, it significantly improved sperm motility (P < 0.05) and also improved reproductive performance such as fertilization rate and hatching rate. To further reveal the mechanism underlying the effects of induced molting on semen quality and reproductive performance in aged Houdan roosters, we collected testes from 3 periods: 1 d before fasting (F0), 15 d after fasting (F15), and 32 d after recovery feeding (R32) for transcriptome sequencing analysis. A total of 5,671 genes were detected in F0, F15, and R32, and trend analysis of the 5,671 differential genes showed 2 significant trends (profile 5 and profile 2). KEGG enrichment analysis of the genes in the 2 profiles, revealed significantly enriched pathway regulation of actin cytoskeleton. In the regulation of actin cytoskeleton pathway, we found a protein kinase gene (SRC) and a senescence gene (ROCK2). SRC was highly expressed at F15, leading to the phosphorylation of key substrates, which in turn disrupted the Sertoli cell spermatid connection and the spermiogenesis process, resulting in no mature spermatozoa produced from F15, SRC expression was inhibited at R32, the expression level was reduced, and mature spermatozoa reappeared. The senescence gene ROCK2 was highly expressed at F15 compared to F0 and R32, which may have been responsible for inducing senescence atrophy in the testes.

Kinesin-14 KIFC1 promotes acrosome formation and chromatin maturation during mouse spermiogenesis

KIFC1, a member of kinesin-14 subfamily motors, is essential for meiotic cell division and acrosome formation during spermatogenesis. However, the functions of KIFC1 in the formation and maintenance of the acrosome in male germ cells remain to be elucidated. In this study, we report the structural deformities of acrosomes in the in vivo KIFC1 inhibition mouse models. The proacrosomal vesicles diffuse into the cytoplasm and form atypical acrosomal granules. This phenotype is consistent with globozoospermia patients and probably results from the failure of the Golgi-derived vesicle trafficking and actin filament organization. Moreover, the multinucleated and undifferentiated spermatogenic cells in the epidydimal lumen after KIFC1 inhibition reveal the specific roles of KIFC1 in regulating post-meiotic maturation. Overall, our results uncover KIFC1 as an essential regulator in the trafficking, fusion and maturation of acrosomal vesicles during spermiogenesis.

SYPL1 defines a vesicular pathway essential for sperm cytoplasmic droplet formation and male fertility

The cytoplasmic droplet is a conserved dilated area of cytoplasm situated at the neck of the sperm flagellum. Viewed as residual cytoplasm inherited from late spermatids, the cytoplasmic droplet contains numerous saccular elements as its key content. However, the origin of these saccules and the function of the cytoplasmic droplet have long been speculative. Here, we identify the molecular origin of these cytoplasmic droplet components by uncovering a vesicle pathway essential for formation and sequestration of saccules within the cytoplasmic droplet. This process is governed by a transmembrane protein SYPL1 and its interaction with VAMP3. Genetic ablation of SYPL1 in mice reveals that SYPL1 dictates the formation and accumulation of saccular elements in the forming cytoplasmic droplet. Derived from the Golgi, SYPL1 vesicles are critical for segregation of key metabolic enzymes within the forming cytoplasmic droplet of late spermatids and epididymal sperm, which are required for sperm development and male fertility. Our results uncover a mechanism to actively form and segregate saccules within the cytoplasmic droplet to promote sperm fertility.

LncRNA5251 inhibits spermatogenesis via modification of cell-cell junctions

BACKGROUND

Male factors-caused decline in total fertility has raised significant concern worldwide. LncRNAs have been identified to play various roles in biological systems, including spermatogenesis. This study aimed to explore the role of lncRNA5251 in mouse spermatogenesis.

METHODS

The expression of lncRNA5251 was modulated in mouse testes in vivo or spermatogonial stem cells (C18-4 cells) in vitro by shRNA.

RESULTS

The sperm motility in two generations mice after modulation of lncRNA5251 (muF0 and muF1) was decreased significantly after overexpression of lncRNA5251. GO enrichment analysis found that knockdown lncRNA5251 increased the expression of genes related to cell junctions, and genes important for spermatogenesis in mouse testes. Meanwhile, overexpressing lncRNA5251 decreased the gene and/or protein expression of important genes for spermatogenesis and immune pathways in mouse testes. In vitro, knockdown lncRNA5251 increased the expression of genes for cell junction, and the protein levels of some cell junction proteins such as CX37, OCLN, JAM1, VCAM1 and CADM2 in C18-4 cells. LncRNA5251 is involved in spermatogenesis by modulation of cell junctions.

CONCLUSION

This will provide a theoretical basis for improving male reproductive ability via lncRNA.

Deficiency of the Tmem232 Gene Causes Male Infertility with Morphological Abnormalities of the Sperm Flagellum in Mice

The axoneme and accessory structures of flagella are critical for sperm motility and male fertilization. Sperm production needs precise and highly ordered gene expression to initiate and sustain the many cellular processes that result in mature spermatozoa. Here, we identified a testis enriched gene transmembrane protein 232 (Tmem232), which is essential for the structural integrity of the spermatozoa flagella axoneme. Tmem232 knockout mice were generated for in vivo analyses of its functions in spermatogenesis. Phenotypic analysis showed that deletion of Tmem232 in mice causes male-specific infertility. Transmission electron microscopy together with scanning electron microscopy were applied to analyze the spermatozoa flagella and it was observed that the lack of TMEM232 caused failure of the cytoplasm removal and the absence of the 7th outer microtubule doublet with its corresponding outer dense fiber (ODF). Co-IP assays further identified that TMEM232 interacts with ODF family protein ODF1, which is essential to maintain sperm motility. In conclusion, our findings indicate that TMEM232 is a critical protein for male fertility and sperm motility by regulating sperm cytoplasm removal and maintaining axoneme integrity.

Role of Macroautophagy in Mammalian Male Reproductive Physiology

Physiologically, autophagy is an evolutionarily conserved and self-degradative process in cells. Autophagy carries out normal physiological roles throughout mammalian life. Accumulating evidence shows autophagy as a mechanism for cellular growth, development, differentiation, survival, and homeostasis. In male reproductive systems, normal spermatogenesis and steroidogenesis need a balance between degradation and energy supply to preserve cellular metabolic homeostasis. The main process of autophagy includes the formation and maturation of the phagophore, autophagosome, and autolysosome. Autophagy is controlled by a group of autophagy-related genes that form the core machinery of autophagy. Three types of autophagy mechanisms have been discovered in mammalian cells: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy is classified as non-selective or selective. Non-selective macroautophagy randomly engulfs the cytoplasmic components in autophagosomes that are degraded by lysosomal enzymes. While selective macroautophagy precisely identifies and degrades a specific element, current findings have shown the novel functional roles of autophagy in male reproduction. It has been recognized that dysfunction in the autophagy process can be associated with male infertility. Overall, this review provides an overview of the cellular and molecular basics of autophagy and summarizes the latest findings on the key role of autophagy in mammalian male reproductive physiology.

DOT1L promotes spermatid differentiation by regulating expression of genes required for histone-to-protamine replacement

Unique chromatin remodeling factors orchestrate dramatic changes in nuclear morphology during differentiation of the mature sperm head. A crucial step in this process is histone-to-protamine exchange, which must be executed correctly to avoid sperm DNA damage, embryonic lethality and male sterility. Here, we define an essential role for the histone methyltransferase DOT1L in the histone-to-protamine transition. We show that DOT1L is abundantly expressed in mouse meiotic and postmeiotic germ cells, and that methylation of histone H3 lysine 79 (H3K79), the modification catalyzed by DOT1L, is enriched in developing spermatids in the initial stages of histone replacement. Elongating spermatids lacking DOT1L fail to fully replace histones and exhibit aberrant protamine recruitment, resulting in deformed sperm heads and male sterility. Loss of DOT1L results in transcriptional dysregulation coinciding with the onset of histone replacement and affecting genes required for histone-to-protamine exchange. DOT1L also deposits H3K79me2 and promotes accumulation of elongating RNA Polymerase II at the testis-specific bromodomain gene Brdt. Together, our results indicate that DOT1L is an important mediator of transcription during spermatid differentiation and an indispensable regulator of male fertility.

Single-cell RNA sequencing reveals the fragility of male spermatogenic cells to Zika virus-induced complement activation

Zika virus (ZIKV) is a potential threat to male reproductive health but the mechanisms underlying its influence on testes during ZIKV infection remain obscure. To address this question, we perform single-cell RNA sequencing using testes from ZIKV-infected mice. The results reveal the fragility of spermatogenic cells, especially spermatogonia, to ZIKV infection and show that the genes of the complement system are significantly upregulated mainly in infiltrated S100A4 + monocytes/macrophages. Complement activation and its contribution to testicular damage are validated by ELISA, RT‒qPCR and IFA and further verify in ZIKV-infected northern pigtailed macaques by RNA genome sequencing and IFA, suggesting that this might be the common response to ZIKV infection in primates. On this basis, we test the complement inhibitor C1INH and S100A4 inhibitors sulindac and niclosamide for their effects on testis protection. C1INH alleviates the pathological change in the testis but deteriorates ZIKV infection in general. In contrast, niclosamide effectively reduces S100A4 + monocyte/macrophage infiltration, inhibits complement activation, alleviates testicular damage, and rescues the fertility of male mice from ZIKV infection. This discovery therefore encourages male reproductive health protection during the next ZIKV epidemic.

A Dynamic In vitro developing testis model reflects structures and functions of testicular development in vivo

To better define appropriate applications of our 3-dimensional testicular co-culture as a model for reproductive toxicology, we evaluated the ability of the model to capture structural and functional elements that can be targeted by reproductive toxicants. Testicular co-cultures were prepared from postnatal day 5 male rats and cultured with a Matrigel overlay. Following a 2-day acclimation period, we characterized functional pathway dynamics by evaluating morphology, protein expression, testosterone concentrations, and global gene expression at a range of timepoints from experimental days 0 to 21. Western blotting confirmed expression of Sertoli cell, Leydig cell, and spermatogonial cell-specific protein markers. Testosterone detected in cell culture media indicates active testosterone production. Quantitative pathway analysis identified Gene Ontology biological processes enriched among genes significantly changing over the course of 21 days. Processes enriched among genes significantly increasing through time include general developmental processes (morphogenesis, tissue remodeling, etc.), steroid regulation, Sertoli cell development, immune response, and stress and apoptosis. Processes enriched among genes significantly decreasing over time include several related to male reproductive development (seminiferous tubule development, male gonad development, Leydig cell differentiation, Sertoli cell differentiation), all of which appear to peak in expression between days 1 and 5 before decreasing at later timepoints. This analysis provides a temporal roadmap for specific biological process of interest for reproductive toxicology in the model and anchors the model to sensitive phases of in vivo development, helping to define the relevance of the model for in vivo processes.

Ex vivo effects of 17β-estradiol on the prepubertal rat testis

Although it is well established that testis produces estrogens, their precise effect is not fully documented, particularly during the prepubertal period. In a previous in vivo study, we demonstrated that an exposure of prepubertal rats (15-30 days post-partum (dpp)) to 17β-estradiol (E2) delays the establishment of spermatogenesis. In order to characterize the mechanisms of action and the direct targets of E2 on the immature testis, we developed an organotypic culture model of testicular explants obtained from prepubertal rats (15, 20 and 25 dpp). To determine the involvement of nuclear estrogen receptors (ERs) in the effect of E2, particularly that of ESR1 which is the major ER expressed in the prepubertal testis, a pre-treatment with the full antagonist of this type of ERs (ICI 182.780) was performed. Histological analyses, gene expression studies and hormonal assays were conducted to investigate the effects of E2 on steroidogenesis- and spermatogenesis-related endpoints. Testicular explants from 15 dpp rats were unresponsive to E2 exposure while E2 effects were observed in those obtained from 20 and 25 dpp rats. An E2 exposure of testicular explants obtained from 20 dpp rats seemed to accelerate the establishment of spermatogenesis, whereas an E2 exposure of 25 dpp testicular explants induced a delay of this process. These effects could be related to the E2-induced modulation of steroidogenesis, and involved both ESR1-dependent and -independent mechanisms of action. Overall, this ex vivo study demonstrated differential age- and concentration-related effects of E2 on the testis during the prepubertal period.

IAG Regulates the Expression of Cytoskeletal Protein-Encoding Genes in Shrimp Testis

Insulin-like androgenic gland hormone (IAG) is the master regulator of sexual differentiation and testis development in male crustaceans. However, the molecular mechanism on how IAG functions during testis development is still largely unknown. Here, the transcriptional changes were analyzed in the testes of shrimp after LvIAG knockdown in Litopenaeus vannamei. Differential expression analysis identified 111 differentially expressed genes (DEGs), including 48 upregulated DEGs and 63 downregulated DEGs, in testes of shrimp after LvIAG knockdown. Gene ontology (GO) analysis showed that these DEGs were apparently enriched in cytoskeleton-related GO items. Gene function analysis showed that genes enriched in these GO items mainly encoded actin, myosin, and heat shock protein. Interestingly, these genes were all downregulated in testis after LvIAG knockdown, which was confirmed by qRT-PCR detection. Furthermore, injection of LvIAG protein that was recombinantly expressed in insect cells upregulated the expression levels of these genes. The present study revealed that shrimp IAG might function in testis development through regulating the expression of cytoskeletal protein-encoding genes, which would provide new insights into understanding the functional mechanisms of IAG on male sexual development of crustaceans.

Changes on proteomic and metabolomic profiling of cryopreserved sperm effected by melatonin

Cryopreservation may reduce sperm fertility due to cryodamage including physical-chemical and oxidative stress damages. As a powerful antioxidant, melatonin has been reported to improve cryoprotective effect of sperm. However, the molecular mechanism of melatonin on cryopreserved ram sperm hasn't been fully understand. Give this, this study aimed to investigate the postthaw motility parameters, antioxidative enzyme activities and lipid peroxidation, as well as proteomic, metabolomic changes of Huang-huai ram spermatozoa with freezing medium supplemented with melatonin. Melatonin was firstly replenished to the medium to yield five different final concentrations: 0.1, 0.5, 1.0, 1.5, and 2.0 mM. A control (NC) group without melatonin replenishment was included. Protective effects of melatonin as evidenced by postthaw motility, activities of T-AOC, T-SOD, GSH-Px, CAT, contents of MDA, 4-HNE, as well as acrosome integrity, plasma membrane integrity, with 0.5 mM being the most effective concentration (MC group). Furthermore, 29 differentially abundant proteins involving in sperm functions were screened among Fresh, NC and MC groups of samples (n = 5) based on the 4D-LFQ, with 7 of them upregulated in Fresh and MC groups. 26 differentially abundant metabolites were obtained involving in sperm metabolism among the three groups of samples (n = 8) based on the UHPLC-QE-MS, with 18 of them upregulated in Fresh and MC groups. According to the bioinformatic analysis, melatonin may have positive effects on frozen ram spermatozoa by regulating the abundance changes of vital proteins and metabolites related to sperm function. Particularly, several proteins such as PRCP, NDUFB8, NDUFB9, SDHC, DCTN1, TUBB6, TUBA3E, SSNA1, as well as metabolites like L-histidine, L-targinine, ursolic acid, xanthine may be potential novel biomarkers for evaluating the postthaw quality of ram spermatozoa. In conclusion, a dose-dependent replenishment of melatonin to freezing medium protected ram spermatozoa during cryopreservation, which can improve motility, antioxidant enzyme activities, reduce levels of lipid peroxidation products, modify the proteomic and metabolomic profiling of cryopreserved ram spermatozoa through reduction of oxidative stress, maintenance of OXPHOS and microtubule structure. SIGNIFICANCE: Melatonin, a powerful antioxidant protects ram spermatozoa from cryopreservation injuries in a dose-dependent manner, with 0.5 mM being the most effective concentration. Furthermore, sequencing results based on the 4D-LFQ combined with the UHPLC-QE-MS indicated that melatonin modifies proteomic and metabolomic profiling of ram sperm during cryopreservation. According to the bioinformatic analysis, melatonin may have positive effects on frozen ram spermatozoa by regulating the expression changes of vital proteins and metabolites related to sperm metabolism and function. Particularly, several potential novel biomarkers for evaluating the postthaw quality of ram spermatozoa were acquired, proteins such as PRCP, NDUFB8, NDUFB9, SDHC, DCTN1, TUBB6, TUBA3E, SSNA1, as well as metabolites like L-histidine, L-targinine, ursolic acid, xanthine.

Changes in Organ Weight, Sperm Quality and Testosterone Levels After Aluminum (Al) and Indium (In) Administration to Wistar Rats

BACKGROUND

Aluminum and indium are widely used in industrial manufacturing, in pharmaceutical products, in medical treatments, and in food packaging, so they could reach organisms by different way. In order to clarify whether these elements are dangerous, we already demonstrated the ultrastructural modifications observed in the testicles, the epididymides, and the seminal vesicles of rat. Their pro-oxidative effect was also confirmed concomitantly to a decrease in anti-oxidant defenses in the blood, the testicles, and the liver. Thus, it seemed very logic to evaluate damages in the reproductive organs, especially on the exocrine and endocrine functions of the testicles.

METHODS

Aluminum and indium were intraperitoneally administered to male Wistar rats. Sperm solution was obtained from cauda epididymides. Motility, viability, density, and malformation of spermatozoa solution were assessed. Serum total unconjugated testosterone concentrations were measured using RIA technique.

RESULTS

Our results showed a decrease in weight of the testicles, epididymides, and seminal vesicles of indium-treated rats and an increase in the weight of their kidneys. A decrease in motility, viability, and density of epididymides stored sperm as well as generation of many spermatozoa malformations was also observed especially in indium-treated rats. Testosterone levels were increased in indium but were enhanced in aluminum group. This confirmed our previous studies showing that aluminum and indium are toxic for the testicular tissues. This could be explained by the generation of reactive oxygen species (ROS) affecting strongly the exocrine and the endocrine functions of the testicles.

CONCLUSION

Aluminum and indium are disturbing elements for the exocrine and endocrine functions of rat testicles.

Global warming and testis function: A challenging crosstalk in an equally challenging environmental scenario

Environmental pollution, accounting for both chemical and physical factors, is a major matter of concern due to its health consequences in both humans and animals. The release of greenhouse gases with the consequent increase in environmental temperature is acknowledged to have a major impact on the health of both animals and humans, in current and future generations. A large amount of evidence reports detrimental effects of acute heat stress on testis function, particularly on the spermatogenetic and steroidogenetic process, in both animal and human models, wich is largely related to the testis placement within the scrotal sac and outside the abdomen, warranting an overall scrotal temperature of 2°C-4°C lower than the core body temperature. This review will provide a thorough evaluation of environmental temperature's effect on testicular function. In particular, basic concepts of body thermoregulation will be discussed together with available data about the association between testis damage and heat stress exposure. In addition, the possible association between global warming and the secular decline of testis function will be critically evaluated in light of the available epidemiological studies.

Molecular machineries of ciliogenesis, cell survival, and vasculogenesis are differentially expressed during regeneration in explants of the demosponge Halichondria panicea

Sponges are interesting animal models for regeneration studies, since even from dissociated cells, they are able to regenerate completely. In particular, explants are model systems that can be applied to many sponge species, since small fragments of sponges can regenerate all elements of the adult, including the oscula and the ability to pump water. The morphological aspects of regeneration in sponges are relatively well known, but the molecular machinery is only now starting to be elucidated for some sponge species. Here, we have used an explant system of the demosponge Halichondria panicea to understand the molecular machinery deployed during regeneration of the aquiferous system. We sequenced the transcriptomes of four replicates of the 5-day explant without an osculum (NOE), four replicates of the 17-18-day explant with a single osculum and pumping activity (PE) and also four replicates of field-collected individuals with regular pumping activity (PA), and performed differential gene expression analysis. We also described the morphology of NOE and PE samples using light and electron microscopy. Our results showed a highly disorganised mesohyl and disarranged aquiferous system in NOE that is coupled with upregulated pathways of ciliogenesis, organisation of the ECM, and cell proliferation and survival. Once the osculum is formed, genes involved in "response to stimulus in other organisms" were upregulated. Interestingly, the main molecular machinery of vasculogenesis described in vertebrates was activated during the regeneration of the aquiferous system. Notably, vasculogenesis markers were upregulated when the tissue was disorganised and about to start forming canals (NOE) and angiogenic stimulators and ECM remodelling machineries were differentially expressed once the aquiferous system was in place (PE and PA). Our results are fundamental to better understanding the molecular mechanisms involved in the formation of the aquiferous system in sponges, and its similarities with the early onset of blood-vessel formation in animal evolution.

Involvement of testicular N-glycoproteome heterogeneity in seasonal spermatogenesis of the American mink (Neovison vison)

Spermatogenesis in the American mink is characterized by an annual cycle of transition involving completely inactive and fully activated stages. N-glycosylation of proteins has emerged as an important regulator as it affects protein folding, secretion, degradation, and activity. However, the function of protein N-glycosylation in seasonal spermatogenesis of the American mink remains unclear. In the present study, we established a proteome-wide stoichiometry of N-glycosylation in mink testes at various phases of spermatogenesis using N-linked glycosylated-peptide enrichment in combination with liquid chromatography-tandem mass spectrometry analysis. A total of 532 N-glycosylated sites matching the canonical Asn-X-Ser/Thr motif were identified in 357 testicular proteins. Both the number of glycoproteins and the sites of N-glycosylated proteins in mink testes were highly dynamic at different stages. Functional analyses showed that testicular proteins with different N-glycosylation might play a vital role in spermatogenesis by affecting their folding, distribution, stability, and activity. Overall, our data suggest that the dynamics of N-glycosylation of testicular proteins are involved in seasonal spermatogenesis in the American mink.

MARK2 and MARK4 Regulate Sertoli Cell BTB Dynamics Through Microtubule and Actin Cytoskeletons

Microtubule affinity-regulating kinases (MARKs) are nonreceptor Ser/Thr protein kinases known to regulate cell polarity and microtubule dynamics in Caenorhabditis elegans, Drosophila, invertebrates, vertebrates, and mammals. An earlier study has shown that MARK4 is present at the ectoplasmic specialization and blood-testis barrier (BTB) in the seminiferous epithelium of adult rat testes. Here, we report the function of MARK4 and another isoform MARK2 in Sertoli cells at the BTB. Knockdown of MARK2, MARK4, or MARK2 and MARK4 by RNAi using the corresponding siRNA duplexes without apparent off-target effects was shown to impair tight junction (TJ)-permeability barrier at the Sertoli cell BTB. It also disrupted microtubule (MT)- and actin-based cytoskeletal organization within Sertoli cells. Although MARK2 and MARK4 were shown to share sequence homology, they likely regulated the Sertoli cell BTB and MT cytoskeleton differently. Disruption of the TJ-permeability barrier following knockdown of MARK4 was considerably more severe than loss of MARK2, though both perturbed the barrier. Similarly, loss of MARK2 affected MT organization in a different manner than the loss of MARK4. Knockdown of MARK2 caused MT bundles to be arranged around the cell periphery, whereas knockdown of MARK4 caused MTs to retract from the cell edge. These differences in effects on the TJ-permeability barrier are likely from the unique roles of MARK2 and MARK4 in regulating the MT cytoskeleton of the Sertoli cell.

Androglobin, a chimeric mammalian globin, is required for male fertility

Spermatogenesis is a highly specialized differentiation process driven by a dynamic gene expression program and ending with the production of mature spermatozoa. Whereas hundreds of genes are known to be essential for male germline proliferation and differentiation, the contribution of several genes remains uncharacterized. The predominant expression of the latest globin family member, androglobin (Adgb), in mammalian testis tissue prompted us to assess its physiological function in spermatogenesis. Adgb knockout mice display male infertility, reduced testis weight, impaired maturation of elongating spermatids, abnormal sperm shape, and ultrastructural defects in microtubule and mitochondrial organization. Epididymal sperm from Adgb knockout animals display multiple flagellar malformations including coiled, bifid or shortened flagella, and erratic acrosomal development. Following immunoprecipitation and mass spectrometry, we could identify septin 10 (Sept10) as interactor of Adgb. The Sept10-Adgb interaction was confirmed both in vivo using testis lysates and in vitro by reciprocal co-immunoprecipitation experiments. Furthermore, the absence of Adgb leads to mislocalization of Sept10 in sperm, indicating defective manchette and sperm annulus formation. Finally, in vitro data suggest that Adgb contributes to Sept10 proteolysis in a calmodulin-dependent manner. Collectively, our results provide evidence that Adgb is essential for murine spermatogenesis and further suggest that Adgb is required for sperm head shaping via the manchette and proper flagellum formation.

RNA-Seq reveals the functional specificity of epididymal caput, corpus, and cauda genes of cattleyak

The first filial generation of the cattleyaks demonstrates hybrid vigor; however, the male cattleyaks are infertile and restrict productivity and breeding. The discovery of genes in a segment-specific approach offers valuable information and understanding concerning fertility status, yet the biology of cattleyak epididymis is still progressing. Comparative transcriptome analysis was performed on segment pairs of cattleyak epididymis. The caput versus corpus epididymis provided the highest (57.8%) differentially expressed genes (DEGs), corpus versus cauda (25.1%) followed, whereas caput versus cauda pair (17.1%) had the least DEGs. The expression levels of genes coding EPHB6, TLR1, MUC20, MT3, INHBB, TRPV5, EI24, PAOX, KIF12, DEPDC5, and KRT25, which might have the potentials to regulate the homeostasis, innate immunity, differentiation, motility, transport, and sperm maturation-related function in epididymal cells, were downregulated in the distal segment of epididymis. Top enriched KEGG pathways included mTOR, axon guidance, and taste transduction signaling pathways. EIF4B, EPHB6, and TAS2R42 were enriched in the pathways, respectively. Identifying key, new, and unexplored DEGs among the epididymal segments and further analyzing them could boost cattleyak fertility by maximizing sperm quality from genetically better sires and also facilitate better understanding of the epididymal biology.

SPATA33 affects the formation of cell adhesion complex by interacting with CTNNA3 in TM4 cells

Communication between Sertoli cell is essential during spermatogenesis and testicular development in mice, and the dynamic balance of this communication is regulated by some adhesion proteins. In this study, we found that SPATA33 and CTNNA3 were involved in this process. Quantitative real-time PCR and western blotting showed similar trend of expression of two proteins in the testis of mice of different ages. Subsequently, CRISPR-Cas9 technique was used to prepare Spata33 knockout cell lines with TM4 cells, cell wound scratch assay showed that Spata33 gene knockout affected cell migration, and flow cytometry assay showed that Spata33 knockout resulted in a decreased percentage of G1 phase cells in TM4 cell line. In addition, phalloidin staining assay showed that Spata33 gene knockout disrupted the formation of F-actin. Moreover, the protein immunoprecipitation experiment showed the interaction between SPATA33 and CTNNA3, which affected the interaction between CTNNA3 and CTNNB1. SPATA33 inhibits the formation of CDH1-CTNNB1-CTNNA3 complex through its interaction with CTNNA3, thus weakening adhesion between Sertoli cell and promoting cell migration.

PCSK9 Contributes to the Cholesterol, Glucose, and Insulin2 Homeostasis in Seminiferous Tubules and Maintenance of Immunotolerance in Testis

The PCSK9 contribution to cholesterol and immunotolerance homeostasis and response to glucose, and insulin in testis and hypophysis were studied using Pcsk9-deficient (-/-) and transgenic [Tg (PCSK9)] mice, and diabetic, obese ob/ob and db/db mice. The spermatids/spermatozoa acrosome, peritubular vessels, and epididymal adipocytes were PCSK9- and LDL-R-positive. The pro-PCSK9/PCSK9 ratio was high in interstitial tissue-fractions (ITf) and spermatozoa and low in seminiferous tubule-fractions (STf) in normal adult mice. This ratio decreased in ITf in ob/ob and db/db mice but increased in tubules in ob/ob mice. Deleting pcsk9 lowered cholesterol in serum but increased testicular cholesterol. Furthermore, HMGCoA-red, ACAT-2 and LDL-R turnover increased whereas SR-BI decreased in ITf; in tubules, ABCA1 decreased and 160 kDa LDL-R increased in Pcsk9 -/- mice. Excess testicular cholesterol could result from increased cholesterol synthesis and uptake with reduction in SR-BI-mediated efflux in ITf and from the overload of apoptotic cells, lowered ABCA1-mediated efflux and stimulated LDL-R protein synthesis in tubules in Pcsk9 -/- mice. Concomitantly with the cholesterol accumulation, tubules showed infiltrates of immune cells, elevated IL-17A and IL-17RA, and changes in the immunotolerance homeostasis. PCSK9 deficiency decreased glucose in tubules and spermatozoa while increasing insulin2 in ITf and tubules not serum. Moreover, IR-α, and IR-β augmented in tubules but decreased in the anterior pituitary; IR-α increased whereas IR-β decreased in ITf. The histology and cholesterol levels were normal in Tg (PCSK9) mouse testis. The excess cholesterol creates a milieu favorable to the action of high IL-17A and IL-17RA, the development of inflammatory conditions and self-tolerance breakdown in testis.

The function of nuclear hormone receptor 4A signaling in the human reproductive system: A review

AIM

This review aims to summarize the research focused upon the functions of nuclear hormone receptor 4A (NR4A) in the human reproductive system. The research questions addressed are to decipher what role the NR4A subfamily plays in the regulation of the human reproductive system and effects upon fertility issues through regulation of the expression of the NR4A subfamily.

METHODS

The electronic database PubMed was searched for studies published before November 2021. Keywords included "NR4A," "trophoblast," "decidualization," "folliculogenesis," "estrogen," "pregnancy," "Leydig cells," "fertility," and "reproductive." Relevant references from retrieved manuscripts and review articles were also searched manually.

RESULTS

NR4A subfamily are involved in trophoblast differentiation, endometrial decidualization, embryo adhesion, secretion of related hormones, and regulation of spontaneous term labor. Besides, many studies have provided strong evidence that they play critical roles in spermatogenesis. Furthermore, Multiple mechanisms can affect the expression of NR4As. Broadly, NR4A family receptors affect the human reproductive system in multiple ways.

CONCLUSIONS

Further research is needed to specifically dissect the functions and regulatory mechanisms of these receptors and their pharmaceutical antagonists and agonists. The connection between the NR4A subfamily and a variety of reproductive disorders needs to be proven experimentally such that further examination of human tissue is required to assess the role of these receptors in human reproductive diseases.

Transport of Acrosomal Enzymes by KIFC1 via the Acroframosomal Cytoskeleton during Spermatogenesis in Macrobrachium rosenbergii (Crustacea, Decapoda, Malacostracea)

Simple Summary

In crustaceans, the sperm have no tail, and spermatogenesis consists only of acrosomal formation and nuclear deformation. The mechanism of acrosome formation during spermatogenesis of Macrobrachium rosenbergii is one of the hot topics in reproductive biology. Many motor proteins are involved in spermatogenesis. KIFC1, as a member of the kinesin family, is one of the motor proteins that our lab has been focusing on. The acrosome contains a large number of acrosomal enzymes for the hydrolysis of the egg envelope. In order to understand how these acrosomal enzymes are transported to the acrosome cap after synthesis, we cloned the KIFC1 and the Acrosin of M. rosenbergii. By detecting the localization of KIFC1 and Acrosin, we found that Mr-KIFC1 may be involved in acrosomal enzyme transport during spermiogenesis of M. rosenbergii. This study is to propose the function of KIFC1 to transport acrosomal enzymes along the acroframosome structure during crustacean spermatogenesis.

Abstract

The spermatogenesis of crustaceans includes nuclear deformation and acrosome formation. The mechanism of acrosome formation is one focus of reproductive biology. In this study, Macrobrachium rosenbergii was selected as the research object to explore the mechanism of acrosome formation. The acrosome contains a large number of acrosomal enzymes for the hydrolysis of the egg envelope. How these acrosomal enzymes are transported to the acrosomal site after synthesis is the key scientific question of this study. The acroframosome (AFS) structure of caridean sperm has been reported. We hypothesized that acrosomal enzymes may be transported along the AFS framework to the acrosome by motor proteins. To study this hypothesis, we obtained the full-length cDNA sequences of Mr-kifc1 and Mr-Acrosin from the testis of M. rosenbergii. The Mr-kifc1 and Mr-Acrosin mRNA expression levels were highest in testis. We detected the distribution of Mr-KIFC1 and its colocalization with Mr-Acrosin during spermatogenesis by immunofluorescence. The colocalization of Mr-KIFC1 and microtubule indicated that Mr-KIFC1 may participate in sperm acrosome formation and nucleus maturation. The colocalization of Mr-KIFC1 and Mr-Acrosin indicated that Mr-KIFC1 may be involved in Acrosin transport during spermiogenesis of M. rosenbergii. These results suggest that Mr-KIFC1 may be involved in acrosomal enzymes transport during spermiogenesis of M. rosenbergii.

Overexpression of PD-L1 causes germ cells to slough from mouse seminiferous tubules via the PD-L1/PD-L1 interaction

Spermatogenesis is a cyclical process in which different generations of spermatids undergo a series of developmental steps at a fixed time and finally produce spermatids. Here, we report that overexpression of PD‐L1 (B7 homolog1) in the testis causes sperm developmental disorders and infertility in male mice, with severe malformation and sloughing during spermatid development, characterized by disorganized and collapsed seminiferous epithelium structure. PD‐L1 needs to be simultaneously expressed on Sertoli cells and spermatogonia to cause spermatogenesis failure. After that, we excluded the influence of factors such as the PD‐L1 receptor and humoral regulation, confirming that PD‐L1 has an intrinsic function to interact with PD‐L1. Studies have shown that PD‐L1 not only serves as a ligand but also plays a receptor‐like role in signal transduction. PD‐L1 interacts with PD‐L1 to affect the adhesive function of germ cells, causing malformation and spermatid sloughing. Taken together, these results indicate that PD‐L1 can interact with PD‐L1 to cause germ cell detachment and male infertility.

PCP Protein Inversin Regulates Testis Function Through Changes in Cytoskeletal Organization of Actin and Microtubules

Inversin is an integrated component of the Frizzled (Fzd)/Dishevelled (Dvl)/Diversin planar cell polarity (PCP) complex that is known to work in concert with the Van Gogh-like protein (eg, Vangl2)/Prickle PCP complex to support tissue and organ development including the brain, kidney, pancreas, and others. These PCP protein complexes are also recently shown to confer developing haploid spermatid PCP to support spermatogenesis in adult rat testes. However, with the exception of Dvl3 and Vangl2, other PCP proteins have not been investigated in the testis. Herein, we used the technique of RNA interference (RNAi) to examine the role of inversin (Invs) in Sertoli cell (SC) and testis function by corresponding studies in vitro and in vivo. When inversin was silenced by RNAi using specific small interfering RNA duplexes by transfecting primary cultures of SCs in vitro or testes in vivo, it was shown that inversin knockdown (KD) perturbed the SC tight junction-barrier function in vitro and in vivo using corresponding physiological and integrity assays. More important, inversin exerted its regulatory effects through changes in the organization of the actin and microtubule cytoskeletons, including reducing the ability of their polymerization. These changes, in turn, induced defects in spermatogenesis by loss of spermatid polarity, disruptive distribution of blood-testis barrier-associated proteins at the SC-cell interface, appearance of multinucleated round spermatids, and defects in the release of sperm at spermiation.

RAD51 is essential for spermatogenesis and male fertility in mice

The recombinase RAD51 catalyzes the DNA strand exchange reaction in homologous recombination (HR) during both mitosis and meiosis. However, the physiological role of RAD51 during spermatogenesis remains unclear since RAD51 null mutation is embryonic lethal in mice. In this study, we generated a conditional knockout mouse model to study the role of RAD51 in spermatogenesis. Conditional disruption of RAD51 in germ cells by Vasa-Cre led to spermatogonial loss and Sertoli cell-only syndrome. Furthermore, tamoxifen-inducible RAD51 knockout by UBC-Cre^ERT2 confirmed that RAD51 deletion led to early spermatogenic cells loss and apoptosis. Notably, inducible knockout of RAD51 in adult mice caused defects in meiosis, with accumulated meiotic double-strand breaks (DSBs), reduced numbers of pachytene spermatocytes and less crossover formation. Our study revealed an essential role for Rad51 in the maintenance of spermatogonia as well as meiotic progression in mice.

The tubulin code in mammalian sperm development and function

Microtubules are cytoskeletal elements that play key roles throughout the different steps of sperm development. As an integral part of the sperm flagellum, the molecular machine that generates sperm motility, microtubules are also essential for the progressive swimming of sperm to the oocyte, which is a prerequisite for fertilisation. Given the central role of microtubules in all steps of spermatogenesis, their functions need to be tightly controlled. Recent work has showcased tubulin posttranslational modifications as key players in sperm development and function, with aberrations often leading to male infertility with a broad spectrum of sperm defects. Posttranslational modifications are part of the tubulin code, a mechanism that can control microtubule functions by modulating the properties of their molecular building blocks, the tubulin proteins. Here we review the current knowledge on the implications of the tubulin code in sperm development and functions and its importance for male fertility.

Macroautophagy involved in testosterone synthesis in Leydig cells of male dairy goat (Capra hircus)

Testosterone is an important steroid hormone that is indispensable for male sexual development and the reproductive system. Leydig cells (LCs), where autophagy is extremely active, reside in the testicular interstitium and are the major sites of testosterone production. However, the ultrastructural characteristics and the functional role of autophagy in LCs of livestock remain unknown. In this study, the LCs of the dairy goats were investigated to identify the steroidogenic activity and autophagy levels at different ages of development by light microscopy, immunohistochemistry (IHC), immunofluorescence (IF), and transmission electron microscopy (TEM). Morphological results showed that the steroidogenic activity (3β-HSD staining) and ultrastructural characteristics of the LCs were changed with increasing age. TEM results demonstrated that the organelles involved in testosterone synthesis, e.g., smooth endoplasmic reticulum, mitochondria, and lipid droplets, were abundantly distributed within the cytoplasm of LCs in pubertal and adult testes. Moreover, autophagy activity was enhanced in the testes at pubertal and adult stages compared with that at the juvenile stage. Several different autophagic vacuoles, including pre-autophagosomes, autophagosomes, and autolysosomes, were observed within the cytoplasm of LCs from pubertal and adult testes. However, immunofluorescent staining and TEM results showed that no typical lipophagic or mitophagic vacuoles were observed in the cytoplasm of LCs. Furthermore, primary LCs from dairy goats were used to study the effect of autophagy on testosterone production. After treatment with 3-methyladenine (3-MA, an autophagy inhibitor), the primary LCs decreased testosterone production. In contrast, treatment with rapamycin (an autophagy activator), enhanced steroidogenesis in LCs. Collectively, these in vivo and in vitro results suggested that autophagy activity is related to steroidogenesis in LCs of dairy goats, which may ultimately influence the spermatogenesis and fertility of these animals.

Proteostasis regulated by testis-specific ribosomal protein RPL39L maintains mouse spermatogenesis

Maintaining proteostasis is important for animal development. How proteostasis influences spermatogenesis that generates male gametes, spermatozoa, is not clear. We show that testis-specific paralog of ribosomal large subunit protein RPL39, RPL39L, is required for mouse spermatogenesis. Deletion of Rpl39l in mouse caused reduced proliferation of spermatogonial stem cells, malformed sperm mitochondria and flagella, leading to sub-fertility in males. Biochemical analyses revealed that lack of RPL39L deteriorated protein synthesis and protein quality control in spermatogenic cells, partly due to reduced biogenesis of ribosomal subunits and ribosome homeostasis. RPL39/RPL39L is likely assembled into ribosomes via H/ACA domain containing NOP10 complex early in ribosome biogenesis pathway. Furthermore, Rpl39l null mice exhibited compromised regenerative spermatogenesis after chemical insult and early degenerative spermatogenesis in aging mice. These data demonstrate that maintaining proteostasis is important for spermatogenesis, of which ribosome homeostasis maintained by ribosomal proteins coordinates translation machinery to the regulation of cellular growth.

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Rpl39l deletion causes reduced spermatogenesis and subfertility in male mice

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SSC proliferation, mitochondria and sperm flagella compromised in Rpl39l^–/– mice

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Rpl39l deletion affects ribosomal LSU formation and protein quality control

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Aberrant proteostasis affects spermatogenesis and regeneration

In Silico Analysis of Sperm From Ejaculates with Different Semen Characteristics

Background:

Male infertility is associated with altered characteristics of the sperm within the ejaculate. It is possible to find molecular explanations for the observed phenotypes and their consequences. This study aimed to analyze, using a specialized software, a gene set of transcriptomic data from different types of ejaculates.

Methods:

Data from ejaculate samples categorized as normal, oligospermia, and teratozoospermia were obtained from Gene Expression Omnibus (GEO). After normalization, the data average for each sample category was calculated and analyzed independently using Ingenuity Pathway Analysis (IPA).

Results:

Five important canonical pathways are involved in normal and altered semen samples (Oligospermia and teratozoospermia) except sirtuin signaling and mitochondrial dysfunction pathways. The five most important biological processes are identified in all semen phenotypes, but the only difference is the genes connected with initiation of RNA transcription in oligospermic and asthenospermic samples.

Conclusion:

Surprisingly, different types of ejaculates share many pathways and biological processes; sperm proteomics as a new global approach gives clues for the development of strategies to explain the reason for observed phenotypes of ejaculated spermatozoa, their possible effect on fertility, and for implementing research strategies in the context of infertility diagnosis and treatment.

Biocompatible Nanomaterials as an Emerging Technology in Reproductive Health; a Focus on the Male

A growing body of research has confirmed that nanoparticle (NP) systems can enhance delivery of therapeutic and imaging agents as well as prevent potentially damaging systemic exposure to these agents by modifying the kinetics of their release. With a wide choice of NP materials possessing different properties and surface modification options with unique targeting agents, bespoke nanosystems have been developed for applications varying from cancer therapeutics and genetic modification to cell imaging. Although there remain many challenges for the clinical application of nanoparticles, including toxicity within the reproductive system, some of these may be overcome with the recent development of biodegradable nanoparticles that offer increased biocompatibility. In recognition of this potential, this review seeks to present recent NP research with a focus on the exciting possibilities posed by the application of biocompatible nanomaterials within the fields of male reproductive medicine, health, and research.

Yeast Two-Hybrid Screen Identifies PKA-Riα Interacting Proteins during Mouse Spermiogenesis

cAMP-dependent protein kinase (PKA) signaling plays various roles during mammalian spermatogenesis, ranging from the regulation of gene expression to the modulation of sperm motility. However, the molecular mechanisms that govern the multifaceted functions of PKA during spermatogenesis remain largely unclear. We previously found that PKA regulatory subunit I α (RIα) and catalytic subunit α (Cα) co-sediment with polyribosomal fractions of mouse testis lysate on sucrose gradient and the stimulation of PKA activity facilitates protein synthesis in post-meiotic elongating spermatids, indicating that type I PKA is intricately associated with protein translation machinery and regulates protein synthesis during mouse spermiogenesis. Since PKA activity is often regulated by interacting proteins that form complexes with its regulatory subunits, the identification of PKA-RIα interacting proteins in post-meiotic spermatogenic cells will facilitate our understanding of its regulatory roles in protein synthesis and spermiogenesis. In the present study, we applied a yeast two-hybrid screen to identify PKA-Riα-binding proteins using a cDNA library generated from mouse round and elongating spermatids. Numerous proteins were found to potentially interact with PKA-RIα, including proteostasis modulators, metabolic enzymes, cytoskeletal regulators, and mitochondrial proteins, many of which are specifically expressed in testes. Consistently, the examination of MENA (mouse ENA/VASP homolog) in developing mouse testes suggested that post-meiotic spermatogenic cells express a short isoform of MENA that interacts with PKA-RIα in yeast two-hybrid assay. The identification of PKA-RIα interacting proteins provides us solid basis to further explore how PKA signaling regulates protein synthesis and cellular morphogenesis during mouse spermatogenesis.

Three-dimensional morphological analysis of spermatogenesis in aged mouse testes

Spermatogenesis, which is a continuous process from undifferentiated spermatogonia to spermatozoa in the seminiferous tubules, declines with age. To investigate changes in spermatogenesis with aging, we reconstructed the seminiferous tubules of 12 mice aged 12 to 30 months from serial sections and examined age-related and region-specific alterations in the seminiferous epithelium and spermatogenic waves in three dimensions. The basic structure of the seminiferous tubules, including the numbers of tubules, terminating points, branching points, and total tubule length, did not change with age. Age-related alterations in spermatogenesis, primarily assessed by the formation of vacuoles in Sertoli cells, were detected in the seminiferous tubules at 12 months. The proportion of altered tubule segments with impaired spermatogenesis further increased by 24 months, but remained unchanged thereafter. Altered tubule segments were preferentially distributed in tubule areas close to the rete testis and those in the center of the testis. Spermatogenic waves became shorter in length with age. These results provide a basis for examining the decline of spermatogenesis not only with aging, but also in male infertility.

Acrylamide modulates the mouse epididymal proteome to drive alterations in the sperm small non-coding RNA profile and dysregulate embryo development

Paternal exposure to environmental stressors elicits distinct changes to the sperm sncRNA profile, modifications that have significant post-fertilization consequences. Despite this knowledge, there remains limited mechanistic understanding of how paternal exposures modify the sperm sncRNA landscape. Here, we report the acute sensitivity of the sperm sncRNA profile to the reproductive toxicant acrylamide. Furthermore, we trace the differential accumulation of acrylamide-responsive sncRNAs to coincide with sperm transit of the proximal (caput) segment of the epididymis, wherein acrylamide exposure alters the abundance of several transcription factors implicated in the expression of acrylamide-sensitive sncRNAs. We also identify extracellular vesicles secreted from the caput epithelium in relaying altered sncRNA profiles to maturing spermatozoa and dysregulated gene expression during early embryonic development following fertilization by acrylamide-exposed spermatozoa. These data provide mechanistic links to account for how environmental insults can alter the sperm epigenome and compromise the transcriptomic profile of early embryos.

Kpna6 deficiency causes infertility in male mice by disrupting spermatogenesis

Spermatogenesis is driven by an ordered series of events, which rely on trafficking of specific proteins between nucleus and cytoplasm. The karyopherin α family of proteins mediates movement of specific cargo proteins when bound to karyopherin β. Karyopherin α genes have distinct expression patterns in mouse testis, implying they may have unique roles during mammalian spermatogenesis. Here, we use a loss-of-function approach to determine specifically the role of Kpna6 in spermatogenesis and male fertility. We show that ablation of Kpna6 in male mice leads to infertility and has multiple cumulative effects on both germ cells and Sertoli cells. Kpna6-deficient mice exhibit impaired Sertoli cell function, including loss of Sertoli cells and a compromised nuclear localization of the androgen receptor. Furthermore, our data demonstrate devastating defects on spermiogenesis, including incomplete sperm maturation and a massive reduction in sperm number, accompanied by disturbed histone-protamine exchange, differential localization of the transcriptional regulator BRWD1 and altered expression of RFX2 target genes. Our work uncovers an essential role of Kpna6 in spermatogenesis and, hence, in male fertility.

Summary: Two different mouse models delineate the morphological and functional impact of Kpna6 on spermatogenesis and Sertoli cell function and show that this protein is crucial for fertility in male mice.

The Transformation of the Centrosome into the Basal Body: Similarities and Dissimilarities between Somatic and Male Germ Cells and Their Relevance for Male Fertility

The sperm flagellum is essential for the transport of the genetic material toward the oocyte and thus the transmission of the genetic information to the next generation. During the haploid phase of spermatogenesis, i.e., spermiogenesis, a morphological and molecular restructuring of the male germ cell, the round spermatid, takes place that includes the silencing and compaction of the nucleus, the formation of the acrosomal vesicle from the Golgi apparatus, the formation of the sperm tail, and, finally, the shedding of excessive cytoplasm. Sperm tail formation starts in the round spermatid stage when the pair of centrioles moves toward the posterior pole of the nucleus. The sperm tail, eventually, becomes located opposed to the acrosomal vesicle, which develops at the anterior pole of the nucleus. The centriole pair tightly attaches to the nucleus, forming a nuclear membrane indentation. An articular structure is formed around the centriole pair known as the connecting piece, situated in the neck region and linking the sperm head to the tail, also named the head-to-tail coupling apparatus or, in short, HTCA. Finally, the sperm tail grows out from the distal centriole that is now transformed into the basal body of the flagellum. However, a centriole pair is found in nearly all cells of the body. In somatic cells, it accumulates a large mass of proteins, the pericentriolar material (PCM), that together constitute the centrosome, which is the main microtubule-organizing center of the cell, essential not only for the structuring of the cytoskeleton and the overall cellular organization but also for mitotic spindle formation and chromosome segregation. However, in post-mitotic (G1 or G0) cells, the centrosome is transformed into the basal body. In this case, one of the centrioles, which is always the oldest or mother centriole, grows the axoneme of a cilium. Most cells of the body carry a single cilium known as the primary cilium that serves as an antenna sensing the cell's environment. Besides, specialized cells develop multiple motile cilia differing in substructure from the immotile primary cilia that are essential in moving fluids or cargos over the cellular surface. Impairment of cilia formation causes numerous severe syndromes that are collectively subsumed as ciliopathies. This comparative overview serves to illustrate the molecular mechanisms of basal body formation, their similarities, and dissimilarities, in somatic versus male germ cells, by discussing the involved proteins/genes and their expression, localization, and function. The review, thus, aimed to provide a deeper knowledge of the molecular players that is essential for the expansion of clinical diagnostics and treatment of male fertility disorders.

The coupling apparatus of the sperm head and tail†

A strong sperm head-tail coupling apparatus (HTCA) is needed to ensure the integrity of spermatozoa during their fierce competition to fertilize the egg. A lot of HTCA-specific components have evolved to strengthen the attachment of the tail to the implantation fossa at the sperm head. Defects in HTCA formation lead to acephalic spermatozoa syndrome and pathologies of some male infertility. Recent studies have provided insights into the pathogenic molecular mechanisms of acephalic spermatozoa syndrome. Here, we summarize the proteins involved in sperm neck development and focus on their roles in the formation of HTCA. In addition, we discuss the fine structures of the sperm neck in different species from an evolutionary view, highlighting the potential conservative mechanism of HTCA formation.

The multiple roles of RAB GTPases in female and male meiosis

BACKGROUND

RAB GTPases constitute the largest family of small GTPases and are found in all eukaryotes. RAB GTPases regulate components of the endomembrane system, the nucleus and the plasma membrane, and are involved in intracellular actin/tubulin-dependent vesicle movement, membrane fusion and cell growth in mitosis.

OBJECTIVE AND RATIONALE

RAB GTPases play multiple critical roles during both female and male meiosis. This review summarizes the progress made in our understanding of the role of RAB GTPases in female and male meiosis in different species. We also discuss the potential relationship between RAB GTPases and oocyte/sperm quality, which may help in understanding the mechanisms underlying oogenesis and spermatogenesis and potential genetic causes of infertility.

SEARCH METHODS

The PubMed database was searched for articles published between 1991 and 2020 using the following terms: 'RAB', 'RAB oocyte', 'RAB sperm' and 'RAB meiosis'.

OUTCOMES

An analysis of 126 relevant articles indicated that RAB GTPases are present in all eukaryotes, and ten subfamilies (almost 70 members) are expressed in human cells. The roles of 25 RAB proteins and orthologues in female meiosis and 12 in male meiosis have been reported. RAB proteins are essential for the accurate continuity of genetic material, successful fertilization and the normal growth of offspring. Distinct and crucial functions of RAB GTPases in meiosis have been reported. In oocytes, RAB GTPases are involved in spindle organization, kinetochore-microtubule attachment, chromosome alignment, actin filament-mediated spindle migration, cytokinesis, cell cycle and oocyte-embryo transition. RAB GTPases function in mitochondrial processes and Golgi-mediated vesicular transport during female meiosis, and are critical for cortical granule transport during fertilization and oocyte-embryo transition. In sperm, RAB GTPases are vital for cytoskeletal organization and successful cytokinesis, and are associated with Golgi-mediated acrosome formation, membrane trafficking and morphological changes of sperm cells, as well as the exocytosis-related acrosome reaction and zona reaction during fertilization.

WIDER IMPLICATIONS

Abnormal expression of RAB GTPases disrupts intracellular systems, which may induce diverse diseases. The roles of RAB proteins in female and male reproductive systems, thus, need to be considered. The mechanisms underlying the function of RAB GTPases and the binding specificity of their effectors during oogenesis, spermatogenesis and fertilization remain to be studied. This review should contribute to our understanding of the molecular mechanisms of oogenesis and spermatogenesis and potential genetic causes of infertility.

Key proteins of proteome underlying sperm malformation of rats exposed to low fenvalerate doses are highly related to P53

Fenvalerate (Fen) is an endocrine disruptor, capable of interfering with the activity of estrogen and androgen. Our objective was to explore the molecular mechanisms of Fen on sperm in vivo. Adult male Sprague-Dawley rats were orally exposed to 0, 0.00625, 0.125, 2.5, 30 mg/kg/day Fen for 8 weeks. Sperm morphology, differential proteomics of sperm and testes, bioinformatic analysis, western blotting (WB), and RT-PCR were used to explore the mechanism of Fen on sperm. Data showed that low Fen doses significantly induced sperm malformations. In sperm proteomics, 47 differentially expressed (DE) proteins were enriched in biological processes (BPs) related to energy metabolism, response to estrogen, spermatogenesis; and enriched in cellular components (CCs) relating to energy-metabolism, sperm fibrous sheath and their outer dense fibers. In testicular proteomics, 56 DE proteins were highly associated with mRNA splicing, energy metabolism; and enriched in CCs relating to vesicles, myelin sheath, microtubules, mitochondria. WB showed that the expression of selected proteins was identical to their tendency in 2D gels. Literature indicates that key DE proteins in proteomic profiles (such as Trap1, Hnrnpa2b1, Hnrnpk, Hspa8, and Gapdh) are involved in P53-related processes or morphogenesis or spermatogenesis. Also, P53 mRNA and protein levels were significantly increased by Fen; bioinformatic re-analysis showed that 88.5% DE proteins and P53 formed a complex interacting network, and the key DE proteins were coenriched with P53-related BPs. Results indicate that key DE proteins of proteome underlying sperm malformations of rats exposed to low Fen doses are highly related to P53.

Planar cell polarity (PCP) proteins support spermatogenesis through cytoskeletal organization in the testis

Few reports are found in the literature regarding the role of planar cell polarity (PCP) in supporting spermatogenesis in the testis. Yet morphological studies reported decades earlier have illustrated the directional alignment of polarized developing spermatids, most notably step 17-19 spermatids in stage V-early VIII tubules in the testis, across the plane of the epithelium in seminiferous tubules of adult rats. Such morphological features have unequivocally demonstrated the presence of PCP in developing spermatids, analogous to the PCP noted in hair cells of the cochlea in mammals. Emerging evidence in recent years has shown that Sertoli and germ cells express numerous PCP proteins, mostly notably, the core PCP proteins, PCP effectors and PCP signaling proteins. In this review, we discuss recent findings in the field regarding the two core PCP protein complexes, namely the Van Gogh-like 2 (Vangl2)/Prickle (Pk) complex and the Frizzled (Fzd)/Dishevelled (Dvl) complex. These findings have illustrated that these PCP proteins exert their regulatory role to support spermatogenesis through changes in the organization of actin and microtubule (MT) cytoskeletons in Sertoli cells. For instance, these PCP proteins confer PCP to developing spermatids. As such, developing haploid spermatids can be aligned and orderly packed within the limited space of the seminiferous tubules in the testes for the production of sperm via spermatogenesis. Thus, each adult male in the mouse, rat or human can produce an upward of 30, 50 or 300 million spermatozoa on a daily basis, respectively, throughout the adulthood. We also highlight critical areas of research that deserve attention in future studies. We also provide a hypothetical model by which PCP proteins support spermatogenesis based on recent studies in the testis. It is conceivable that the hypothetical model shown here will be updated as more data become available in future years, but this information can serve as the framework by investigators to unravel the role of PCP in spermatogenesis.

Loss of CEP70 function affects acrosome biogenesis and flagella formation during spermiogenesis

The spermatogenesis process is complex and delicate, and any error in a step may cause spermatogenesis arrest and even male infertility. According to our previous transcriptomic data, CEP70 is highly expressed throughout various stages of human spermatogenesis, especially during the meiosis and deformation stages. CEP70 is present in sperm tails and that it exists in centrosomes as revealed by human centrosome proteomics. However, the specific mechanism of this protein in spermatogenesis is still unknown. In this study, we found a heterozygous site of the same mutation on CEP70 through mutation screening of patients with clinical azoospermia. To further verify, we deleted CEP70 in mice and found that it caused abnormal spermatogenesis, leading to male sterility. We found that the knockout of CEP70 did not affect the prophase of meiosis I, but led to male germ-cell apoptosis and abnormal spermiogenesis. By transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analysis, we found that the deletion of CEP70 resulted in the abnormal formation of flagella and acrosomes during spermiogenesis. Tandem mass tag (TMT)-labeled quantitative proteomic analysis revealed that the absence of CEP70 led to a significant decrease in the proteins associated with the formation of the flagella, head, and acrosome of sperm, and the microtubule cytoskeleton. Taken together, our results show that CEP70 is essential for acrosome biogenesis and flagella formation during spermiogenesis.

A novel role for milk fat globule-EGF factor 8 protein (MFGE8) in the mediation of mouse sperm-extracellular vesicle interactions

Spermatozoa transition to functional maturity as they are conveyed through the epididymis, a highly specialized region of the male excurrent duct system. Owing to their transcriptionally and translationally inert state, this transformation into fertilization competent cells is driven by complex mechanisms of intercellular communication with the secretory epithelium that delineates the epididymal tubule. Chief among these mechanisms are the release of extracellular vesicles (EV), which have been implicated in the exchange of varied macromolecular cargo with spermatozoa. Here, we describe the optimization of a tractable cell culture model to study the mechanistic basis of sperm-extracellular vesicle interactions. In tandem with receptor inhibition strategies, our data demonstrate the importance of milk fat globule-EGF factor 8 (MFGE8) protein in mediating the efficient exchange of macromolecular EV cargo with mouse spermatozoa; with the MFGE8 integrin-binding Arg-Gly-Asp (RGD) tripeptide motif identified as being of particular importance. Specifically, complementary strategies involving MFGE8 RGD domain ablation, competitive RGD-peptide inhibition and antibody-masking of alpha V integrin receptors, all significantly inhibited the uptake and redistribution of EV-delivered proteins into immature mouse spermatozoa. These collective data implicate the MFGE8 ligand and its cognate integrin receptor in the mediation of the EV interactions that underpin sperm maturation.