Disruption of the ubiquitin ligase HERC4 causes defects in spermatozoon maturation and impaired fertility

SPEM1 Gene Mutation in a Case with Sperm Morphological Defects Leading to Male Infertility

The present study aimed at identifying the genetic mutation responsible for teratozoospermic infertility in a case with coiled sperm tails. A 33-year-old infertile male was diagnosed with teratozoospermic infertility, with sperm head in coiled (HIC) tail as the most common deformity. We employed whole exome sequencing to identify the genetic cause in this case. Exome sequencing data was filtered using the following criteria: MAF (< 0.003), ALFA project (< 0.001), 1000 Genomes (< 0.003), Granthem (> 50), Polyphen-2 (> 0.70), SIFT (< 0.03), and PhyloP (> = 0) scores. Shortlisted variants were looked in the in-house 29 exomes data available with us, and the variants that affected conserved amino acid residues or led to insertion/deletion or to protein-truncation with a Combined Annotation Dependent Depletion (CADD) score ≥ 10 were shortlisted. The variants thus populated were prioritized according to their roles in spermiogenesis. The study identified a heterozygous mutation c.826C > T (Arg276Trp) in the SPEM1 gene as a potential pathogenic variant that led to teratozoospermic infertility in the case under investigation. The mutation had a minor allele frequency of 0.00008176 in the gnomAd database and was absent in the Indian Genome Variations database. This is the first human study reporting a mutation in the SPEM1 gene as a cause of coiled sperm tails.

Fish HERC7: Phylogeny, Characterization, and Potential Implications for Antiviral Immunity in European Sea Bass

E3 ubiquitin ligases, key components of the ubiquitin proteasome system, orchestrate protein degradation through ubiquitylation and profoundly impact cellular biology. Small HERC E3 ligases (HERC3-6) have diverse functions in mammals, including roles in spermatogenesis, protein degradation, and immunity. Until now, only mammals' HERC3, HERC5, and HERC6 are known to participate in immune responses, with major involvement in the antiviral response. Interestingly, an exclusive HERC7 has been characterized in fish showing great molecular conservation and antiviral roles. Thus, this study identifies and characterizes the herc7 gene in the European sea bass teleost. The European sea bass herc7 gene and the putative protein show good conservation of the promoter binding sites for interferons and the RCC1 and HECT domains characteristic of HERC proteins, respectively. The phylogenetic analysis shows a unique cluster with the fish-exclusive HERC7 orthologues. During ontogeny, the herc7 gene is expressed from 3 days post-fertilization onwards, being constitutively and widely distributed in adult tissues. In vitro, stimulated leucocytes up-regulate the herc7 gene in response to mitogens and viruses, pointing to a role in the immune response. Furthermore, sea bass herc7 expression is related to the interferon response intensity and viral load in different tissues upon in vivo infection with red-grouper betanodavirus (RGNNV), suggesting the potential involvement of fish HERC7 in ISGylation-based antiviral activity, similarly to mammalian HERC5. This study broadens the understanding of small HERC proteins in fish species and highlights HERC7 as a potential contributor to the immune response in European sea bass, with implications for antiviral defense mechanisms. Future research is needed to unravel the precise actions and functions of HERC7 in teleost fish immunity, providing insights into direct antiviral activity and viral evasion.

Transcriptome analysis of reproductive tract tissues of male river prawn Macrobrachium americanum

BACKGROUND

The river prawn, Macrobrachium americanum (M. americanum), is one of the largest prawns of the genus in Latin America and is an amphidromous species distributed along the Pacific coast of America. This prawn has commercial value due to its size and taste, making it a good option for aquaculture production. Its culture has been attempted in ponds and concrete tanks, but no successful technique can still support commercial production. Understanding the mechanisms that regulate reproduction at the molecular level is very important. This knowledge can provide tools for manipulating transcripts, which could increase the number or size of animals in the culture. Our understanding of the mechanism that regulates the reproduction of M. americanum at the molecular level is limited.

AIM

Perform and analyze the transcriptome assembly of the testes, vas deferens, and terminal ampulla of M. americanum. to provide new molecular information about its reproduction.

METHODS AND RESULTS

The cDNA library was constructed and sequenced for each tissue to identify novel transcripts. A combined transcriptome with the three tissues was assembled using Trinity software. Unigenes were annotated using BLASTx and BLAST2GO. The transcriptome assembly generated 1,059,447 unigenes, of which 7222 genes had significant hits (e-value < 1 × 10-5) when compared against the Swiss-Prot database. Around 75 genes were related to sex determination, testis development, spermatogenesis, spermiogenesis, fertilization, maturation of testicular cells, neuropeptides, hormones, hormone receptors, and/or embryogenesis.

CONCLUSIONS

These results provide new molecular information about M. americanum reproduction, representing a reference point for further genetic studies of this species.

Cessation of chronic delta-9-tetrahydrocannabinol use partially reverses impacts on male fertility and the sperm epigenome in rhesus macaques

OBJECTIVE

To determine whether discontinuation of delta-9-tetrahydrocannabinol (THC) use mitigates THC-associated changes in male reproductive health using a rhesus macaque model of daily THC edible consumption.

DESIGN

Research animal study.

SETTING

Research institute environment.

PATIENT(S)

Adult male rhesus macaques (age, 8-10 years; n = 6).

INTERVENTION(S)

Chronic daily THC edible administration at medically and recreationally relevant contemporary doses followed by cessation of THC use.

MAIN OUTCOME MEASURE(S)

Testicular volume, serum male hormones, semen parameters, sperm deoxyribonucleic acid (DNA) fragmentation, seminal fluid proteomics, and whole genome bisulfite sequencing of sperm DNA.

RESULT(S)

Chronic THC use resulted in significant testicular atrophy, increased gonadotropin levels, decreased serum sex steroid levels, changes in seminal fluid proteome, and increased DNA fragmentation with partial recovery after discontinuation of THC use. For every increase of 1 mg/7 kg/day in THC dosing, there was a significant decrease in the total testicular volume bilaterally by 12.6 cm3 (95% confidence interval [CI], 10.6-14.5), resulting in a 59% decrease in volume. With THC abstinence, the total testicular volume increased to 73% of its original volume. Similarly, with THC exposure, there were significant decreases in the mean total testosterone and estradiol levels and a significant increase in the follicle-stimulating hormone level. With increasing THC dose, there was a significant decrease in the liquid semen ejaculate volume and weight of coagulum; however, no other significant changes in the other semen parameters were noted. After discontinuing THC use, there was a significant increase in the total serum testosterone level by 1.3 ng/mL (95% CI, 0.1-2.4) and estradiol level by 2.9 pg/mL (95% CI, 0.4-5.4), and the follicle-stimulating hormone level significantly decreased by 0.06 ng/mL (95% CI, 0.01-0.11). Seminal fluid proteome analysis revealed differential expression of proteins enriched for processes related to cellular secretion, immune response, and fibrinolysis. Whole genome bisulfite sequencing identified 23,558 CpGs differentially methylated in heavy-THC vs. pre-THC sperm, with partial restoration of methylation after discontinuation of THC use. Genes associated with altered differentially methylated regions were enriched for those involved in the development and function of the nervous system.

CONCLUSION(S)

This is the first study demonstrating that discontinuation of chronic THC use in rhesus macaques partially restores adverse impacts to male reproductive health, THC-associated sperm differentially methylated regions in genes important for development, and expression of proteins important for male fertility.

Inhibition of the NF-κB signaling pathway affects gonadal differentiation and leads to male bias in Paramisgurnus dabryanus

In recent years, sex-controlled breeding has emerged as an effective strategy to enhance the yields of economic animals with different growth characteristics, while increasing the economic benefits of aquaculture. It is known that the NF-κB pathway participates in gonadal differentiation and reproduction. Therefore, we used the large-scale loach as a research model for the present study and selected an effective inhibitor of the NF-κB signaling pathway (QNZ). This, to investigates the impacts of the NF-κB signaling pathway on gonadal differentiation during a critical period of gonad development and after maturation. Simultaneously, the sex ratio bias and the reproductive capacities of adult fish were analyzed. Our results indicated that the inhibition of the NF-κB signaling pathway influenced the expression of genes related to gonad development, regulated the gene expression related to the brain-gonad-liver axis of juvenile loaches, and finally impacted the gonadal differentiation of the large-scale loach and promoted a male-biased sex ratio. Meanwhile, high QNZ concentrations affected the reproductive abilities of adult loaches and inhibited the growth performance of offspring. Thus, our results deepened the exploration of sex control in fish and provided a certain research basis for the sustainable development of the aquaculture industry.

IKBA phosphorylation governs human sperm motility through ACC-mediated fatty acid beta-oxidation

The nuclear factor-κB (NF-κB) signaling pathway regulates specific immunological responses and controls a wide range of physiological processes. NF-κB inhibitor alpha (IKBA) is an NF-κB inhibitory mediator in the cytoplasm that modulates the nuclear translocation and DNA binding activities of NF-κB proteins. However, whether the upstream cascade of the canonical NF-κB signaling pathway has physiological roles independent of IKBA-mediated transcriptional activation remains unclear. Herein we investigated the function of IKBA in mature sperm in which transcriptional and translational events do not occur. IKBA was highly expressed in human sperm. The repression of IKBA phosphorylation by its inhibitor Bay117082 markedly enhanced sperm motility. On the contrary, lipopolysaccharide-stimulated IKBA phosphorylation significantly decreased sperm motility. Nevertheless, Bay117082 treatment did not affect the motility of IKBA-knockout sperm. Further, untargeted metabolomic analysis and pharmacological blocking assays revealed that the Bay117082-induced increase in sperm motility was attributable to fatty acid β-oxidation (FAO) enhancement. In addition, we found that IKBA phosphorylation inhibition resulted in a significant reduction of acetyl-CoA carboxylase levels in the FAO metabolic pathway. Our findings indicate that IKBA-mediated signaling orchestrates sperm motility program and improves our understanding of transcription-independent NF-κB signaling pathway in cells.

Infection of Trichinella spiralis Affects the Reproductive Capacity of ICR/CD-1 Male Mice by Reducing the Urine Pheromone Contents and Sperm Quality

Female mice can discriminate the urinary odors of male mice due to their olfactory acuity. Parasitic infection or subclinical infection can decrease the odor attractiveness of male mice and finally lead to aversion or avoidance responses in odor selection for female mice. Trichinella spiralis is a kind of tissue-parasitizing nematode that causes trichinellosis, a zoonotic parasitic disease that spreads throughout the world. However, the reproductive injury caused by Trichinella spiralis infection was not fully revealed. In this study, we explored the effect of Trichinella spiralis infection on the reproductive capacity in ICR/CD-1 male mice. We identified eight volatile compounds in urine by GC-MS analysis, and the results indicated that the contents of dimethyl sulfone, Z-7-tetradecen-1-ol, 6-Hydroxy-6-methyl-3-heptanone and (S)-2-sec-butyl-4,5-dihydrothiazole were significantly downregulated after parasitic infection, which might lead to the reduction of attractiveness of male mice urine to females. On the other hand, parasitic infection decreased sperm quality and downregulated the expression levels of Herc4, Ipo11, and Mrto4, and these genes were strongly related to spermatogenesis. In summary, this study revealed that the reproductive injury caused by Trichinella spiralis infection in ICR/CD-1 male mice could be associated with a decrease in urine pheromone content and sperm quality.

The evolution of the testis transcriptome in pregnant male pipefishes and seahorses

In many animals, sperm competition and sexual conflict are thought to drive the rapid evolution of male-specific genes, especially those expressed in the testes. A potential exception occurs in the male pregnant pipefishes, where females transfer eggs to the males, eliminating testes from participating in these processes. Here, we show that testis-related genes differ dramatically in their rates of molecular evolution and expression patterns in pipefishes and seahorses (Syngnathidae) compared to other fish. Genes involved in testis or sperm function within syngnathids experience weaker selection in comparison to their orthologs in spawning and livebearing fishes. An assessment of gene turnover and expression in the testis transcriptome suggests that syngnathids have lost (or significantly reduced expression of) important classes of genes from their testis transcriptomes compared to other fish. Our results indicate that more than 50 million years of male pregnancy have removed syngnathid testes from the molecular arms race that drives the rapid evolution of male reproductive genes in other taxa.

The Conceivable Functions of Protein Ubiquitination and Deubiquitination in Reproduction

Protein ubiquitination with general existence in virtually all eukaryotic cells serves as a significant post-translational modification of cellular proteins, which leads to the degradation of proteins via the ubiquitin-proteasome system. Deubiquitinating enzymes (DUBs) can reverse the ubiquitination effect by removing the ubiquitin chain from the target protein. Together, these two processes participate in regulating protein stability, function, and localization, thus modulating cell cycle, DNA repair, autophagy, and transcription regulation. Accumulating evidence indicates that the ubiquitination/deubiquitination system regulates reproductive processes, including the cell cycle, oocyte maturation, oocyte-sperm binding, and early embryonic development, primarily by regulating protein stability. This review summarizes the extensive research concerning the role of ubiquitin and DUBs in gametogenesis and early embryonic development, which helps us to understand human pregnancy further.

Ubiquitin-Proteasome System-Regulated Protein Degradation in Spermatogenesis

Spermatogenesis is a prolonged and highly ordered physiological process that produces haploid male germ cells through more than 40 steps and experiences dramatic morphological and cellular transformations. The ubiquitin proteasome system (UPS) plays central roles in the precise control of protein homeostasis to ensure the effectiveness of certain protein groups at a given stage and the inactivation of them after this stage. Many UPS components have been demonstrated to regulate the progression of spermatogenesis at different levels. Especially in recent years, novel testis-specific proteasome isoforms have been identified to be essential and unique for spermatogenesis. In this review, we set out to discuss our current knowledge in functions of diverse USP components in mammalian spermatogenesis through: (1) the composition of proteasome isoforms at each stage of spermatogenesis; (2) the specificity of each proteasome isoform and the associated degradation events; (3) the E3 ubiquitin ligases mediating protein ubiquitination in male germ cells; and (4) the deubiquitinases involved in spermatogenesis and male fertility. Exploring the functions of UPS machineries in spermatogenesis provides a global picture of the proteome dynamics during male germ cell production and shed light on the etiology and pathogenesis of human male infertility.

A Z-Linked E3 Ubiquitin Ligase Cs-rchy1 Is Involved in Gametogenesis in Chinese Tongue Sole, Cynoglossus semilaevis

Simple Summary

The sexual growth dimorphism prevails in animals and this phenomenon is even more obvious in marine fish, so understanding the mechanism of gonadal development and gametogenesis is of great importance for sex control, thus increased productivity in aquaculture. In mammal, ubiquitin ligase plays a versatile role in gonadal development and spermatogenesis, whereas its function in fish is little reported. Using Cynoglossus semilaevis (one-year-old female individual usually grows 2–4 times bigger than male) as the fish model, a Z-chromosome linked ubiquitin ligase neurl3 was previously identified and characterized, which suggested its involvement in spermatogenesis. However, in this study, characterization of another Z-chromosome linked ubiquitin ligase Cs-rchy1 suggested it might function both in spermatogenesis and oogenesis, as well as the potential role in growth. These data may provide the genetic resource for gene editing or marker exploration in future.

Abstract

Ubiquitin ligase (E3) plays a versatile role in gonadal development and spermatogenesis in mammals, while its function in fish is little reported. In this study, a Z-chromosome linked ubiquitin ligase rchy1 in C. semilaevis (Cs-rchy1) was cloned and characterized. The full-length cDNA was composed of 1962 bp, including 551 bp 5′UTR, 736 bp 3′UTR, and 675 bp ORF encoding a 224-amino-acid (aa) protein. Cs-rchy1 was examined among seven different tissues and found to be predominantly expressed in gonads. In testis, Cs-rchy1 could be detected from 40 days post hatching (dph) until 3 years post hatching (yph), but there was a significant increase at 6 months post hatching (mph). In comparison, the expression levels in ovary were rather stable among different developmental stages. In situ hybridization showed that Cs-rchy1 was mainly localized in germ cells, that is, spermatid and spermatozoa in testis and stage I, II and III oocytes in ovary. In vitro RNA interference found that Cs-rchy1 knockdown resulted in the decline of sox9 and igf1 in ovarian cell line and down-regulation of cyp19a in the testicular cell line. These data suggested that Cs-rchy1 might participate in gonadal differentiation and gametogenesis, via regulating steroid hormone synthesis.

Transcriptomic analysis revealed gene expression profiles during the sex differentiation of Chinese tongue sole (Cynoglossus semilaevis)

Sex differentiation in aquatic fish is important both for theoretical study and practical production, as growth dimorphism frequently appears in different sexes, especially in marine fish. The deciphered genome, identification of the male-determining gene dmrt1 and established genotypic sex screening method make Chinese tongue sole (Cynoglossus semilaevis) an ideal model to study sex differentiation in fish. In this study, comparative gonadal transcriptomic analyses were conducted for genetic females and males at 48, 68, and 108 days post hatching (dph), representing pre-, during- and post-gonadal differentiation stages, although the gonad is not completely differentiated and isolable in 48 and 68 dph individuals, while it is in 108 dph individuals. Altogether, 28 libraries were constructed, and a mean of 46.64 M clean reads was obtained. Differentially expressed gene (DEG) analysis revealed that 179 genes had similar expression patterns in males and females in all three stages. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis suggested that the enriched pathways included ubiquitin-mediated proteolysis, lysosomes, and RNA degradation. Moreover, weighted gene coexpression network analyses (WGCNA) identified 14 modules, one of which was closely correlated with female differentiation, exhibiting female-biased expression in all three stages (48, 68, 108 dph). An illustrated core gene interaction network of this module identified 50 genes, most of which are on W chromosomes. Six genes, including two ubiquitin conjugating enzymes, were selected for further investigation, and their female-biased expression was confirmed in even earlier stages, at 10 and 30 dph. These data facilitate our understanding of sex differentiation in fish and provide a genomic rationale for screening candidate genes (preferentially W-linked genes) that could be involved in the female differentiation process.

Co-expression analysis identifies neuro-inflammation as a driver of sensory neuron aging in Aplysia californica

Aging of the nervous system is typified by depressed metabolism, compromised proteostasis, and increased inflammation that results in cognitive impairment. Differential expression analysis is a popular technique for exploring the molecular underpinnings of neural aging, but technical drawbacks of the methodology often obscure larger expression patterns. Co-expression analysis offers a robust alternative that allows for identification of networks of genes and their putative central regulators. In an effort to expand upon previous work exploring neural aging in the marine model Aplysia californica, we used weighted gene correlation network analysis to identify co-expression networks in a targeted set of aging sensory neurons in these animals. We identified twelve modules, six of which were strongly positively or negatively associated with aging. Kyoto Encyclopedia of Genes analysis and investigation of central module transcripts identified signatures of metabolic impairment, increased reactive oxygen species, compromised proteostasis, disrupted signaling, and increased inflammation. Although modules with immune character were identified, there was no correlation between genes in Aplysia that increased in expression with aging and the orthologous genes in oyster displaying long-term increases in expression after a virus-like challenge. This suggests anti-viral response is not a driver of Aplysia sensory neuron aging.

SLC22A14 is a mitochondrial riboflavin transporter required for sperm oxidative phosphorylation and male fertility

Ablation of Slc22a14 causes male infertility in mice, but the underlying mechanisms remain unknown. Here, we show that SLC22A14 is a riboflavin transporter localized at the inner mitochondrial membrane of the spermatozoa mid-piece and show by genetic, biochemical, multi-omic, and nutritional evidence that riboflavin transport deficiency suppresses the oxidative phosphorylation and reprograms spermatozoa energy metabolism by disrupting flavoenzyme functions. Specifically, we find that fatty acid β-oxidation (FAO) is defective with significantly reduced levels of acyl-carnitines and metabolites from the TCA cycle (the citric acid cycle) but accumulated triglycerides and free fatty acids in Slc22a14 knockout spermatozoa. We demonstrate that Slc22a14-mediated FAO is essential for spermatozoa energy generation and motility. Furthermore, sperm from wild-type mice treated with a riboflavin-deficient diet mimics those in Slc22a14 knockout mice, confirming that an altered riboflavin level causes spermatozoa morphological and bioenergetic defects. Beyond substantially advancing our understanding of spermatozoa energy metabolism, our study provides an attractive target for the development of male contraceptives.

Observations on Dag-like defect of spermatozoa induced by treatment of the phytotherapeutic Quassia amara/quassin in the mouse model

Gross alterations in the morphology of spermatozoa, teratozoospermia, invariably render them incapable of fertilisation. One of the contributory factors to teratozoospermia is failure of spermatozoon to shed the cytoplasmic droplet even after their arrival at epididymis. Quassia amara and quassin are of medicinal value with special reference to malaria. Nevertheless, there are also reports implicating Quassia/quassin in male reproductive toxicity. We were interested in finding if its therapeutic application would jeopardise male fertility. So, we tested it for male reproductive toxicity by analysing, among other aspects, abnormal sperm morphologies, and made a systematic analysis of the spermatozoa of treated mice before they are spermiated and until they arrive at the cauda epididymis. The spermatozoa not only failed to shed the cytoplasmic droplet during epididymal transit but swell to a very large size and were angulated, resulting in Dag-like defect or lasso shape. A link between cytoplasmic droplet that was retained and lasso shape of tail was indicated. This article traces the structural changes in spermatozoa that lead to angulation, flexion and coiling of the tail, caused due to retention of cytoplasmic droplet, and explains one of the mechanisms of toxicant-induced teratozoospermia.

Reproductive injury in male BALB/c mice infected with Neospora caninum

Background

Neospora caninum is one of the main causes of abortion in pregnant animals. However, N. caninum-induced reproductive injury in male mice is still unclear.

Methods

Male BALB/c mice were infected with a bovine isolate of N. caninum, and the organ coefficients of the testis and epididymis were measured. Lesions in the testis and epididymis were observed by light microscopy and transmission electron microscopy. Expression of the spermatogenic cell apoptosis-related proteins p53 and caspase-3 was detected by western blot. The expression of spermatogenesis-related genes in the testis was detected by reverse transcription-PCR. Sperm morphology and motility were observed. The levels of nitric oxide (NO) and antisperm antibody (AsAb) in the testicular homogenates and hormones in the serum were detected by enzyme-linked immunosorbent assay. The reproductive capacity of the male mice was detected using a reproduction test.

Results

The organ coefficients of the testis and epididymis of the experimental group were significantly downregulated. Light microscopy examination revealed that the spermatogenic cells of the testis were arranged in a disordered manner, and the number was reduced. The number of sperm in the epididymal lumen was significantly reduced, and the cytoplasm exhibited vacuolation and degeneration. Ultrastructural studies revealed that the cells of the testis and epididymis tissues showed varying degrees of disease. The level of p53 and caspase-3 expression in the testis was significantly upregulated. The expression of the testicular spermatogenesis-related genes Herc4, Ipo11 and Mrto4 were strongly downregulated. Observation of sperm by microscopic examination revealed significantly reduced sperm density and sperm motility, and the number of sperm deformities was significantly increased. The level of NO and AsAb was significantly increased. The levels of luteinizing hormone, follicle-stimulating hormone and gonadotropin-releasing hormone were significantly upregulated, whereas the levels of testosterone, thyrotropin-releasing hormone, thyroxine and thyroid-stimulating hormone were significantly downregulated. After challenge, the infected male mice and healthy female mice were caged together: the subsequent fetal death rate was increased, and the conception rate, litter size, number of live births and the birth weight were significantly reduced.

Conclusions

Infection of male BALB/c mice with the bovine isolate of N. caninum induced varying degrees of injury to the testis, epididymis and sperm of the mice, destroyed spermatogenesis and affected the reproductive capacity.

Destruction or Reconstruction: A Subtle Liaison between the Proteolytic and Signaling Role of Protein Ubiquitination in Spermatogenesis

Ubiquitination is one of the most diverse forms of protein post-translational modification that changes the function of the landscape of substrate proteins in response to stimuli, without the need for "de novo" protein synthesis. Ubiquitination is involved in almost all aspects of eukaryotic cell biology, from the best-studied role in promoting the removal of faulty or unnecessary proteins by the way of the ubiquitin proteasome system and autophagy-lysosome pathway to the recruitment of proteins in specific non-proteolytic signaling pathways, as emerged by the more recent discoveries about the protein signature with peculiar types of ubiquitin chains. Spermatogenesis, on its own, is a complex cellular developmental process in which mitosis, meiosis, and cell differentiation coexist so to result in the continuous formation of haploid spermatozoa. Successful spermatogenesis is thus at the same time a mixed result of the precise expression and correct intracellular destination of structural proteins and enzymes, from one hand, and the fine removal by targeted degradation of unfolded or damaged proteins as well as of obsolete, outlived proteins, from the other hand. In this minireview, I will focus on the importance of the ubiquitin system all over the spermatogenic process, discussing both proteolytic and non-proteolytic functions of protein ubiquitination. Alterations in the ubiquitin system have been in fact implicated in pathologies leading to male infertility. Notwithstanding several aspects of the multifaceted world of the ubiquitin system have been clarified, the physiological meaning of the so-called ubiquitin code remains still partially elusive. The studies reviewed in this chapter provide information that could aid the investigators to pursue new promising discoveries in the understanding of human and animal reproductive potential.

The activation of the chymotrypsin-like activity of the proteasome is regulated by soluble adenyl cyclase/cAMP/protein kinase A pathway and required for human sperm capacitation

One of the first events of mammalian sperm capacitation is the activation of the soluble adenyl cyclase/cAMP/protein kinase A (SACY/cAMP/PKA) pathway. Here, we evaluated whether the increase in PKA activity at the onset of human sperm capacitation is responsible for the activation of the sperm proteasome and whether this activation is required for capacitation progress. Viable human sperm were incubated with inhibitors of the SACY/cAMP/PKA pathway. The chymotrypsin-like activity of the sperm proteasome was evaluated using a fluorogenic substrate. Sperm capacitation status was evaluated using the chlortetracycline assay and tyrosine phosphorylation. To determine whether proteasomal subunits were phosphorylated by PKA, the proteasome was immunoprecipitated and tested on a western blot using an antibody against phosphorylated PKA substrates. Immunofluorescence microscopy analysis and co-immunoprecipitation (IPP) were used to investigate an association between the catalytic subunit alpha of PKA (PKA-Cα) and the proteasome. The chymotrypsin-like activity of the sperm proteasome significantly increased after 5 min of capacitation (P < 0.001) and remained high for the remaining incubation time. Treatment with H89, KT5720 or KH7 significantly decreased the chymotrypsin-like activity of the proteasome (P < 0.001). IPP experiments indicated that PKA inhibition significantly modified phosphorylation of proteasome subunits. In addition, PKA-Cα colocalized with the proteasome in the equatorial segment and in the connecting piece, and co-immunoprecipitated with the proteasome. This is the first demonstration of sperm proteasome activity being directly regulated by SACY/PKA-Cα. This novel discovery extends our current knowledge of sperm physiology and may be used to manage sperm capacitation during assisted reproductive technology procedures.

LARP7-Mediated U6 snRNA Modification Ensures Splicing Fidelity and Spermatogenesis in Mice

U6 snRNA, as an essential component of the catalytic core of the pre-mRNA processing spliceosome, is heavily modified post-transcriptionally, with 2'-O-methylation being most common. The role of these modifications in pre-mRNA splicing as well as their physiological function in mammals have remained largely unclear. Here we report that the La-related protein LARP7 functions as a critical cofactor for 2'-O-methylation of U6 in mouse male germ cells. Mechanistically, LARP7 promotes U6 loading onto box C/D snoRNP, facilitating U6 2'-O-methylation by box C/D snoRNP. Importantly, ablation of LARP7 in the male germline causes defective U6 2'-O-methylation, massive alterations in pre-mRNA splicing, and spermatogenic failure in mice, which can be rescued by ectopic expression of wild-type LARP7 but not an U6-loading-deficient mutant LARP7. Our data uncover a novel role of LARP7 in regulating U6 2'-O-methylation and demonstrate the functional requirement of such modification for splicing fidelity and spermatogenesis in mice.

Comparative analysis of testis transcriptomes associated with male infertility in triploid cyprinid fish

Spermatogenesis involves a series of cellular transformations and thousands of regulated genes. Previously, we showed that the triploid fish (3nBY) cannot produce mature spermatozoa. In the present study, evaluation of the testis microstructure revealed that germ cells of 3nBY could develop into round spermatids, but then degenerated, resulting in male infertility. In this study we comparatively analysed the testis transcriptomes from 3nBY and its diploid parent YB and identified a series of differentially expressed genes (DEGs) that were enriched in the Wnt signalling pathway and the apoptotic and ubiquitin-mediated proteolysis processes in 3nBY. Gene ontology functional analyses revealed that some DEGs in 3nBY were directly associated with the process of gamete generation, development and sperm flagellum assembly. In addition, the expression of a number of genes related to meiosis (Inhibitor Of DNA Binding 2 (ID2), Ovo Like Transcriptional Repressor 1 (OVOL1)), mitochondria (ATP1b (ATPase Na+/K+ Transporting Subunit Beta 1), ATP2a (ATPase, Ca++ Transporting, Cardiac Muscle, Slow Twitch 2), ATP5a (ATP Synthase F1 Subunit Alpha), Mitochondrially Encoded Cytochrome C Oxidase I (COX1), NADH Dehydrogenase Subunit 4 (ND4)) and chromatin structure (Histone 1 (H1), Histone 2a (H2A), Histone 2b (H2B), Histone 3 (H3), Histone 4 (H4)) was lower in the testes of 3nBY, whereas the expression of genes encoding ubiquitin (Ubiquitin Conjugating Enzymes (UBEs), Ring Finger Proteins (RNFs)) and apoptosis (CASPs (Caspase 3, Caspase 7,Caspase 8), BCLs (B-Cell Lymphoma 3, B-Cell CLL/Lymphoma 2, B Cell CLL/Lymphoma 10)) proteins involved in spermatid degeneration was higher. These data suggest that the disrupted expression of genes associated with spermatogenesis and the increased expression of mitochondrial ubiquitin, which initiates cell apoptosis, may result in spermatid degeneration in male 3nBY. This study provides information regarding the potential molecular regulatory mechanisms underlying male infertility in polyploid fish.

CDK2 regulates the NRF1/Ehmt1 axis during meiotic prophase I

Palmer et al. identify NRF1 as a novel CDK2 interactor and substrate. This interaction was found to be important for the DNA-binding activity of NRF1. Their findings demonstrate that the loss of CDK2 expression impairs the regulation of NRF1 transcriptional activity, leading to inappropriate transcription during meiotic division.

Meiosis generates four genetically distinct haploid gametes over the course of two reductional cell divisions. Meiotic divisions are characterized by the coordinated deposition and removal of various epigenetic marks. Here we propose that nuclear respiratory factor 1 (NRF1) regulates transcription of euchromatic histone methyltransferase 1 (EHMT1) to ensure normal patterns of H3K9 methylation during meiotic prophase I. We demonstrate that cyclin-dependent kinase (CDK2) can bind to the promoters of a number of genes in male germ cells including that of Ehmt1 through interaction with the NRF1 transcription factor. Our data indicate that CDK2-mediated phosphorylation of NRF1 can occur at two distinct serine residues and negatively regulates NRF1 DNA binding activity in vitro. Furthermore, induced deletion of Cdk2 in spermatocytes results in increased expression of many NRF1 target genes including Ehmt1. We hypothesize that the regulation of NRF1 transcriptional activity by CDK2 may allow the modulation of Ehmt1 expression, therefore controlling the dynamic methylation of H3K9 during meiotic prophase.

A miRNA-HERC4 pathway promotes breast tumorigenesis by inactivating tumor suppressor LATS1

The E3 ligase HERC4 is overexpressed in human breast cancer and its expression levels correlated with the prognosis of breast cancer patients. However, the roles of HERC4 in mammary tumorigenesis remain unclear. Here we demonstrate that the knockdown of HERC4 in human breast cancer cells dramatically suppressed their proliferation, survival, migration, and tumor growth in vivo, while the overexpression of HERC4 promoted their aggressive tumorigenic activities. HERC4 is a new E3 ligase for the tumor suppressor LATS1 and destabilizes LATS1 by promoting the ubiquitination of LATS1. miRNA-136-5p and miRNA-1285-5p, expression of which is decreased in human breast cancers and is inversely correlated with the prognosis of breast cancer patients, are directly involved in suppressing the expression of HERC4. In summary, we discover a miRNA-HERC4-LATS1 pathway that plays important roles in the pathogenesis of breast cancer and represents new therapeutic targets for human breast cancer.

Rapid microevolution during recent range expansion to harsh environments

BACKGROUND

Adaptive evolution is one of the crucial mechanisms for organisms to survive and thrive in new environments. Recent studies suggest that adaptive evolution could rapidly occur in species to respond to novel environments or environmental challenges during range expansion. However, for environmental adaptation, many studies successfully detected phenotypic features associated with local environments, but did not provide ample genetic evidence on microevolutionary dynamics. It is therefore crucial to thoroughly investigate the genetic basis of rapid microevolution in response to environmental changes, in particular on what genes and associated variation are responsible for environmental challenges. Here, we genotyped genome-wide gene-associated microsatellites to detect genetic signatures of rapid microevolution of a marine tunicate invader, Ciona robusta, during recent range expansion to the harsh environment in the Red Sea.

RESULTS

The Red Sea population was significantly differentiated from the other global populations. The genome-wide scan, as well as multiple analytical methods, successfully identified a set of adaptive genes. Interestingly, the allele frequency largely varied at several adaptive loci in the Red Sea population, and we found significant correlations between allele frequency and local environmental factors at these adaptive loci. Furthermore, a set of genes were annotated to get involved in local temperature and salinity adaptation, and the identified adaptive genes may largely contribute to the invasion success to harsh environments.

CONCLUSIONS

All the evidence obtained in this study clearly showed that environment-driven selection had left detectable signatures in the genome of Ciona robusta within a few generations. Such a rapid microevolutionary process is largely responsible for the harsh environmental adaptation and therefore contributes to invasion success in different aquatic ecosystems with largely varied environmental factors.

Transcriptome profiling of the honeybee parasite Varroa destructor provides new biological insights into the mite adult life cycle

Background

The parasite Varroa destructor represents a significant threat to honeybee colonies. Indeed, development of Varroa infestation within colonies, if left untreated, often leads to the death of the colony. Although its impact on bees has been extensively studied, less is known about its biology and the functional processes governing its adult life cycle and adaptation to its host. We therefore developed a full life cycle transcriptomic catalogue in adult Varroa females and included pairwise comparisons with males, artificially-reared and non-reproducing females (10 life cycle stages and conditions in total).

Results

Extensive remodeling of the Varroa transcriptome was observed, with an upregulation of energetic and chitin metabolic processes during the initial and final phases of the life cycle (e.g. phoretic and post-oviposition stages), whereas during reproductive stages in brood cells genes showing functions related to transcriptional regulation were overexpressed. Several neurotransmitter and neuropeptide receptors involved in behavioural regulation, as well as active compounds of salivary glands, were also expressed at a higher level outside the reproductive stages. No difference was detected between artificially-reared phoretic females and their counterparts in colonies, or between females who failed to reproduce and females who successfully reproduced, indicating that phoretic individuals can be reared outside host colonies without impacting their physiology and that mechanisms underlying reproductive failure occur before oogenesis.

Conclusions

We discuss how these new findings reveal the remarkable adaptation of Varroa to its host biology and notably to the switch from living on adults to reproducing in sealed brood cells. By spanning the entire adult life cycle, our work captures the dynamic changes in the parasite gene expression and serves as a unique resource for deciphering Varroa biology and identifying new targets for mite control.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4668-z) contains supplementary material, which is available to authorized users.

HERC4 Is Overexpressed in Hepatocellular Carcinoma and Contributes to the Proliferation and Migration of Hepatocellular Carcinoma Cells

Recently, more and more evidences unveiled that ubiquitin-proteasome system (UPS) makes an important contribution to the occurrence and development of cancer. HERC4 is one identified Ubiqutin ligase E3, a member of UPS. Although some studies showed that HERC4 abnormally expresses in many cancer cells, till now, nothing has been reported about the function of HERC4 in the development of hepatoma carcinoma. To this end, in this study, we studied the function of HERC4 for the first time in hepatoma carcinoma cells. We detected the expression of HERC4 in tumor and normal tissues, and in hepatoma carcinoma cell lines by using qRT-PCR, Western blot, immunohistochemistry, and immunofluorescence. The data showed that tumor tissues expressed higher HERC4 than normal ones. HERC4 was expressed, although to a different extent, in hepatoma carcinoma cell lines. Colony formation assay, CCK-8 assay, EdU assay, wound healing assay, and FACS indicated that HERC4 plays a role in cell proliferative and migration ability. HERC4 overexpression increases the proliferative and migration ability and reduces apoptosis of hepatoma carcinoma cells; in contrast, knockdown of HERC4 decreases the proliferative and migration ability and increases the apoptosis rate of hepatoma carcinoma cells. Taken together, our findings showed that HERC4 has an effect on the occurrence and development of hepatoma carcinoma by promoting hepatoma carcinoma cell proliferation and migration, and by reducing cell apoptosis, further providing another therapeutic target for the intervention of related diseases.

Functional and pathological relevance of HERC family proteins: a decade later

The HERC gene family encodes proteins with two characteristic domains in their sequence: the HECT domain and the RCC1-like domain (RLD). In humans, the HERC family comprises six members that can be divided into two groups based on their molecular mass and domain structure. Whereas large HERCs (HERC1 and HERC2) contain one HECT and more than one RLD, small HERCs (HERC3-6) possess single HECT and RLD domains. Accumulating evidence shows the HERC family proteins to be key components of a wide range of cellular functions, including neurodevelopment, DNA damage repair, cell growth and immune response. Considering the significant recent advances made regarding HERC functionality, an updated review summarizing the progress is greatly needed at 10 years since the last HERC review. We provide an integrated view of HERC function and go into detail about its implications for several human diseases such as cancer and neurological disorders.

[RNA interference of HERC4 inhibits proliferation, apoptosis and migration of cervical cancer Hela cells]

OBJECTIVE

To explore the effects of silencing HERC4 on the proliferation, apoptosis, and migration of cervical cancer cell line Hela and the possible molecular mechanisms.

METHODS

Three HERC4-specific small interfering RNAs (siRNAs) were transfected into Hela cells, and HERC4 expression in the cells was examined with Western blotting. CCK-8 assay, annexin V-FITC/PI assay, and wound healing assay were used to assess the effect of HERC4 silencing on the proliferation, apoptosis and migration ability of Hela cells. The expression levels of cyclin D1 and Bcl-2 in the cells were detected using Western blotting.

RESULTS

Transfection of siRNA-3 resulted in significantly decreased HERC4 protein expression (P<0.01). HERC4 silencing by siRNA-3 markedly suppressed the proliferation and migration of Hela cells, increased the apoptosis rate (P<0.01) and reduced the expression levels of cyclin D1 and Bcl-2 (P<0.01).

CONCLUSION

Silencing of HERC4 efficiently inhibits the proliferation, migration, and invasion of Hela cells in vitro, and the underlying mechanisms may involve the down-regulation of cyclin D1 and Bcl-2.

The ubiquitin ligase HERC4 mediates c-Maf ubiquitination and delays the growth of multiple myeloma xenografts in nude mice

The transcription factor c-Maf is extensively involved in the pathophysiology of multiple myeloma (MM), a fatal malignancy of plasma cells. In the present study, affinity chromatography and mass spectrometry were used to identify c-Maf ubiquitination-associated proteins, from which the E3 ligase HERC4 was found to interact with c-Maf and catalyzed its polyubiquitination and subsequent proteasome-mediated degradation. HERC4 mediated polyubiquitination at K85 and K297 in c-Maf, and this polyubiquitination could be prevented by the isopeptidase USP5. Further analysis on the NCI-60 cell line collection revealed that RPMI 8226, a MM-derived cell line, expressed the lowest level of HERC4. Primary bone marrow analysis revealed HERC4 expression was high in normal bone marrow, but was steadily decreased during myelomagenesis. These findings suggested HERC4 played an important role in MM progression. Moreover, ectopic HERC4 expression decreased MM proliferation in vitro, and delayed xenograft tumor growth in vivo. Therefore, modulation of c-Maf ubiquitination by targeting HERC4 may represent a new therapeutic modality for MM.

Expression of HERC4 in lung cancer and its correlation with clinicopathological parameters

BACKGROUND

Growing evidence suggests that the members of the ubiquitin-proteasome system (UPS) are important for tumorigenesis. HERC4, one component, is a recently identified ubiqutin ligase. However, the expression level and function role of HERC4 in lung cancer remain unknown. Our objective was to investigate any correlation between HERC4 and development of lung cancer and its clinical significance.

MATERIALS AND METHODS

To determine HERC4 expression in lung cancer, an immunohistochemistry analysis of a tissue microarray containing samples of 10 lung normal tissues, 15 pulmonary neuroendocrine carcinomas, 45 squamous epithelial cancers and 50 adenocarcinomas was conducted. Receiver operating characteristic (ROC) curve analysis was applied to obtain a cut-off point of 52.5%, above which the expression of HERC4 was regarded as "positive".

RESULTS

On the basis of ROC curve analysis, positive expression of HERC4 was detected in 0/10 (0.0%) of lung normal tissues, in 4/15 (26.7%) of pulmonary neuroendocrine carcinomas, in 13/45 (28.9%) of squamous epithelial cancers and in 19/50 (38.0%) of adenocarcinomas. It showed that lung tumors expressed more HERC4 protein than adjacent normal tissues (χ2=4.675, p=0.031). Furthermore, HERC4 positive expression had positive correlation with pT status (χ2=44.894, p=0.000), pN status (χ2=43.628, p=0.000), histological grade (χ2=7.083, p=0.029) and clinical stage (χ2=72.484, p=0.000), but not age (χ2=0.910, p=0.340).

CONCLUSIONS

Our analysis suggested that HERC4 is likely to be a diagnostic biomarker for lung cancer.

Hippo Stabilises Its Adaptor Salvador by Antagonising the HECT Ubiquitin Ligase Herc4

Signalling through the Hippo (Hpo) pathway involves a kinase cascade, which leads to the phosphorylation and inactivation of the pro-growth transcriptional co-activator Yorkie (Yki). Despite the identification of a large number of pathway members and modulators, our understanding of the molecular events that lead to activation of Hpo and the downstream kinase Warts (Wts) remain incomplete. Recently, targeted degradation of several Hpo pathway components has been demonstrated as a means of regulating pathway activity. In particular, the stability of scaffold protein Salvador (Sav), which is believed to promote Hpo/Wts association, is crucially dependent on its binding partner Hpo. In a cell-based RNAi screen for ubiquitin regulators involved in Sav stability, we identify the HECT domain protein Herc4 (HECT and RLD domain containing E3 ligase) as a Sav E3 ligase. Herc4 expression promotes Sav ubiquitylation and degradation, while Herc4 depletion stabilises Sav. Interestingly, Hpo reduces Sav/Herc4 interaction in a kinase-dependent manner. This suggests the existence of a positive feedback loop, where Hpo stabilises its own positive regulator by antagonising Herc4-mediated degradation of Sav.

Mouse BRWD1 is critical for spermatid postmeiotic transcription and female meiotic chromosome stability

Exhibiting sexually dimorphic roles in mice, BRWD1 is essential for proper meiotic chromosome condensation and telomere structure during oogenesis and for haploid-specific gene transcription during postmeiotic sperm differentiation.

Postmeiotic gene expression is essential for development and maturation of sperm and eggs. We report that the dual bromodomain-containing protein BRWD1, which is essential for both male and female fertility, promotes haploid spermatid–specific transcription but has distinct roles in oocyte meiotic progression. Brwd1 deficiency caused down-regulation of ∼300 mostly spermatid-specific transcripts in testis, including nearly complete elimination of those encoding the protamines and transition proteins, but was not associated with global epigenetic changes in chromatin, which suggests that BRWD1 acts selectively. In females, Brwd1 ablation caused severe chromosome condensation and structural defects associated with abnormal telomere structure but only minor changes in gene expression at the germinal vesicle stage, including more than twofold overexpression of the histone methyltransferase MLL5 and LINE-1 elements transposons. Thus, loss of BRWD1 function interferes with the completion of oogenesis and spermatogenesis through sexually dimorphic mechanisms: it is essential in females for epigenetic control of meiotic chromosome stability and in males for haploid gene transcription during postmeiotic sperm differentiation.

The E3 ubiquitin protein ligase HERC2 modulates the activity of tumor protein p53 by regulating its oligomerization

The tumor suppressor p53 is a transcription factor that coordinates the cellular response to several kinds of stress. p53 inactivation is an important step in tumor progression. Oligomerization of p53 is critical for its posttranslational modification and its ability to regulate the transcription of target genes necessary to inhibit tumor growth. Here we report that the HECT E3 ubiquitin ligase HERC2 interacts with p53. This interaction involves the CPH domain of HERC2 (a conserved domain within Cul7, PARC, and HERC2 proteins) and the last 43 amino acid residues of p53. Through this interaction, HERC2 regulates p53 activity. RNA interference experiments showed how HERC2 depletion reduces the transcriptional activity of p53 without affecting its stability. This regulation of p53 activity by HERC2 is independent of proteasome or MDM2 activity. Under these conditions, up-regulation of cell growth and increased focus formation were observed, showing the functional relevance of the HERC2-p53 interaction. This interaction was maintained after DNA damage caused by the chemotherapeutic drug bleomycin. In these stressed cells, p53 phosphorylation was not impaired by HERC2 knockdown. Interestingly, p53 mutations that affect its tetramerization domain disrupted the HERC2-p53 interaction, suggesting a role for HERC2 in p53 oligomerization. This regulatory role was shown using cross-linking assays. Thus, the inhibition of p53 activity after HERC2 depletion can be attributed to a reduction in p53 oligomerization. Ectopic expression of HERC2 (residues 2292-2923) confirmed these observations. Together, these results identify HERC2 as a novel regulator of p53 signaling.

Ubiquitin-proteasome system in spermatogenesis

Spermatogenesis represents a complex succession of cell division and differentiation events resulting in the continuous formation of spermatozoa. Such a complex program requires precise expression of enzymes and structural proteins which is effected not only by regulation of gene transcription and translation, but also by targeted protein degradation. In this chapter, we review current knowledge about the role of the ubiquitin-proteasome system in spermatogenesis, describing both proteolytic and non-proteolytic functions of ubiquitination. Ubiquitination plays essential roles in the establishment of both spermatogonial stem cells and differentiating spermatogonia from gonocytes. It also plays critical roles in several key processes during meiosis such as genetic recombination and sex chromosome silencing. Finally, in spermiogenesis, we summarize current knowledge of the role of the ubiquitin-proteasome system in nucleosome removal and establishment of key structures in the mature spermatid. Many mechanisms remain to be precisely defined, but present knowledge indicates that research in this area has significant potential to translate into benefits that will address problems in both human and animal reproduction.

The expression and clinical significance of HERC4 in breast cancer

Background

Increasing evidence suggest that ubiquitin-proteasome system (UPS) plays a key role in tumorigenesis. HERC4 is a recently identified ubiqutin ligase. However, the expression status and biological functions of HERC4 in cancers are not clearly.

Methods

We evaluated the HERC4 expression in breast cancer cell lines and breast tumor tissues by quantitative real-time PCR and western blot analysis. To investigate the clinicopathological significance of HERC4, immunohistochemistry analysis for HERC4 was performed on a tissue microarray including 13 benign fibroadenoma, 15 intraductal carcinoma, 120 histologically confirmed invasive ductal carcinoma. Receiver operating characteristic (ROC) analysis was applied to determine the optimal cut-off score for positive expression of HERC4, when HERC4 positive expression percentage was above 60%, tumor was defined as “positive”.

Results

HERC4 was up-regulated in breast cancer cell lines and breast tumor tissues compared to non-tumorigenic cell line and adjacent normal breast tissues. According to ROC analysis, HERC4 positive expression was detected in 1/16 (6.3%) of normal breast tissue, in 3/13 (23.1%) of fibroadenoma, in 6/15 (40%) of intraductal carcinoma and 66/120 (55%) of invasive ductal carcinoma. Positive expression of HERC4 was positively correlated with pT status, pN status, clinical stage and histological grade of patients with invasive ductal carcinoma (p < 0.05).

Conclusions

Our findings suggest that HERC4 was a significant diagnostic marker for invasive ductal carcinoma of the breast.

Global impact of Salmonella pathogenicity island 2-secreted effectors on the host phosphoproteome

During the late stages of infection, Salmonella secretes numerous effectors through a type III secretion system that is encoded within Salmonella pathogenicity island 2 (SPI2). Despite the importance of SPI2 as a major virulence factor leading to the systemic spread of the bacteria and diseases, a global view of its effects on host responses is still lacking. Here, we measured global impacts of SPI2 effectors on the host phosphorylation and protein expression levels in RAW264.7 and in HeLa cells, as macrophage and nonphagocytic models of infection. We observe that SPI2 effectors differentially modulate the host phosphoproteome and cellular processes (e.g. protein trafficking, cytoskeletal regulation, and immune signaling) in a host cell-dependent manner. Our unbiased approach reveals the involvement of many previously unrecognized proteins, including E3 ligases (HERC4, RanBP2, and RAD18), kinases (CDK, SIK3, and WNK1), and histones (H2B1F, H4, and H15), in late stages of Salmonella infection. Furthermore, from this phosphoproteome analysis and other quantitative screens, we identified HSP27 as a direct in vitro and in vivo molecular target of the only type III secreted kinase, SteC. Using biochemical and cell biological assays, we demonstrate that SteC phosphorylates multiple sites in HSP27 and induces actin rearrangement through this protein. Together, these results provide a broader landscape of host players contributing to specific processes/pathways mediated by SPI2 effectors than was previously appreciated.

MARCH7 E3 ubiquitin ligase is highly expressed in developing spermatids of rats and its possible involvement in head and tail formation

Spermatogenesis is a highly complicated metamorphosis process of male germ cells. Recent studies have provided evidence that the ubiquitin-proteasome system plays an important role in sperm head shaping, but the underlying mechanism is less understood. In this study, we localized membrane-associated RING-CH (MARCH)7, an E3 ubiquitin ligase, in rat testis. Northern blot analysis showed that March7 mRNA is expressed ubiquitously but highly in the testis and ovary. In situ hybridization of rat testis demonstrated that March7 mRNA is expressed weakly in spermatogonia and its level is gradually increased as they develop. Immunohistochemical analysis detected MARCH7 protein expression in spermiogenic cells from late round spermatids to elongated spermatids and in epididymal spermatozoa. Moreover, MARCH7 was found to be localized to the caudal end of the developing acrosome of late round and elongating spermatids, colocalizing with β-actin, a component of the acroplaxome. In addition, MARCH7 was also detected in the developing flagella and its expression levels were prominent in elongated spermatids. We also showed that MARCH7 catalyzes lysine 48 (K48)-linked ubiquitination. Immunolocalization studies revealed that K48-linked ubiquitin chains were detected in the heads of elongating spermatids and in the acrosome/acroplaxome, neck, midpiece and cytoplasmic lobes of elongated spermatids. These results suggest that MARCH7 is involved in spermiogenesis by regulating the structural and functional integrity of the head and tail of developing spermatids.

Mouse RC/BTB2, a member of the RCC1 superfamily, localizes to spermatid acrosomal vesicles

Mouse RC/BTB2 is an unstudied protein of the RCC1 (Regulator of Chromosome Condensation) superfamily. Because of the significant remodeling of chromatin that occurs during spermiogenesis, we characterized the expression and localization of mouse RC/BTB2 in the testis and male germ cells. The Rc/btb2 gene yields two major transcripts: 2.3 kb Rc/btb2-s, present in most somatic tissues examined; and 2.5 kb Rc/btb2-t, which contains a unique non-translated exon in its 5'-UTR that is only detected in the testis. During the first wave of spermatogenesis, Rc/btb2-t mRNA is expressed from day 8 after birth, reaching highest levels of expression at day 30 after birth. The full-length protein contains three RCC1 domains in the N-terminus, and a BTB domain in the C-terminus. In the testis, the protein is detectable from day 12, but is progressively up-regulated to day 30 and day 42 after birth. In spermatids, some of the protein co-localizes with acrosomal markers sp56 and peanut lectin, indicating that it is an acrosomal protein. A GFP-tagged RCC1 domain is present throughout the cytoplasm of transfected CHO cells. However, both GFP-tagged, full-length RC/BTB2 and a GFP-tagged BTB domain localize to vesicles in close proximity to the nuclear membrane, suggesting that the BTB domain might play a role in mediating full-length RC/BTB2 localization. Since RCC1 domains associate with Ran, a small GTPase that regulates molecular trafficking, it is possible that RC/BTB2 plays a role in transporting proteins during acrosome formation.

Membrane-associated RING-CH 10 (MARCH10 protein) is a microtubule-associated E3 ubiquitin ligase of the spermatid flagella

Spermiogenesis is a complex and dynamic process of the metamorphosis of spermatids into spermatozoa. There is a great deal that is still unknown regarding the regulatory mechanisms for the formation of the sperm flagellum. In this study, we determined that the membrane-associated RING-CH 10 (March10) gene is predominantly expressed in rat testis. We isolated two March10 isoforms encoding MARCH10a and MARCH10b, which are generated by alternative splicing. MARCH10a is a long RING finger protein, and MARCH10b is a short RING finger-less protein. Immunohistochemical staining revealed that the MARCH10 proteins are specifically expressed in elongating and elongated spermatids, and the expression is absent in epididymal spermatozoa. MARCH10 immunoreactivity was observed in the cytoplasmic lobes as well as the principal piece and annulus of the flagella. When overexpressed in COS7 cells, MARCH10a was localized along the microtubules, whereas MARCH10b was distributed throughout the cytoplasm. An in vitro microtubule cosedimentation assay showed that MARCH10a is directly associated with microtubules. An in vitro ubiquitination assay demonstrated that the RING finger domain of MARCH10a exhibits an E3 ubiquitin ligase activity along with the E2 ubiquitin-conjugating enzyme UBE2B. Moreover, MARCH10a undergoes proteasomal degradation by autoubiquitination in transfected COS7 cells, but this activity was abolished upon microtubule disassembly. These results suggest that MARCH10 is involved in spermiogenesis by regulating the formation and maintenance of the flagella in developing spermatids.

Sperm proteasome and fertilization

The omnipresent ubiquitin–proteasome system (UPS) is an ATP-dependent enzymatic machinery that targets substrate proteins for degradation by the 26S proteasome by tagging them with an isopeptide chain composed of covalently linked molecules of ubiquitin, a small chaperone protein. The current knowledge of UPS involvement in the process of sperm penetration through vitelline coat (VC) during human and animal fertilization is reviewed in this study, with attention also being given to sperm capacitation and acrosome reaction/exocytosis. In ascidians, spermatozoa release ubiquitin-activating and conjugating enzymes, proteasomes, and unconjugated ubiquitin to first ubiquitinate and then degrade the sperm receptor on the VC; in echinoderms and mammals, the VC (zona pellucida/ZP in mammals) is ubiquitinated during oogenesis and the sperm receptor degraded during fertilization. Various proteasomal subunits and associated enzymes have been detected in spermatozoa and localized to sperm acrosome and other sperm structures. By using specific fluorometric substrates, proteasome-specific proteolytic and deubiquitinating activities can be measured in live, intact spermatozoa and in sperm protein extracts. The requirement of proteasomal proteolysis during fertilization has been documented by the application of various proteasome-specific inhibitors and antibodies. A similar effect was achieved by depletion of sperm-surface ATP. Degradation of VC/ZP-associated sperm receptor proteins by sperm-borne proteasomes has been demonstrated in ascidians and sea urchins. On the applied side, polyspermy has been ameliorated by modulating sperm-associated deubiquitinating enzymes. Diagnostic and therapeutic applications could emerge in human reproductive medicine. Altogether, the studies on sperm proteasome indicate that animal fertilization is controlled in part by a unique, gamete associated, extracellular UPS.

Mice lacking the USP2 deubiquitinating enzyme have severe male subfertility associated with defects in fertilization and sperm motility

The ubiquitin-proteasome system plays an important role in spermatogenesis. However, the functions of deubiquitinating enzymes in this process remain poorly characterized. We previously showed that the deubiquitinating enzyme USP2 is induced in late elongating spermatids. To identify its function, we generated mice lacking USP2. Usp2 -/- mice appeared normal, and the weights of major organs, including the testis, did not differ from wild type (Usp2 +/+). However, although the numbers of testicular spermatids and epididymal spermatozoa were normal in Usp2 -/- males, these animals had a severe defect in fertility, yielding only 12% as many offspring as Usp2 +/+ littermates. Spermatogenesis in Usp2 -/- mice was morphologically normal except for the presence of abnormal aggregations of elongating spermatids and formation of multinucleated cells in some tubules. The epididymal epithelium was morphologically normal in Usp2 -/- mice, but some abnormal cells other than sperm were present in the lumen. Usp2 -/- epididymal spermatozoa manifested normal motility when incubated in culture media, but rapidly became immotile when incubated in PBS in contrast to Usp2 +/+ spermatozoa, which largely maintained motility under this condition. Usp2 -/- and +/+ spermatozoa underwent acrosome reactions in vitro with similar frequency. In vitro fertilization assays demonstrated a severe defect in the ability of Usp2 -/- spermatozoa to fertilize eggs. This could be bypassed by intracytoplasmic sperm injection or removal of the zona pellucida, which resulted in fertilization rates similar to that of Usp2 +/+ mice. We demonstrate for the first time, using mouse transgenic approaches, a role for the ubiquitin system in fertilization.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors

As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.

The epididymis as a target for male contraceptive development

The epididymis is an excellent target for the development of a male contraceptive. This is because the process of sperm maturation occurs in this organ; spermatozoa become motile and are able to recognise and fertilise an egg once they have traversed the epididymal duct. However, a number of attempts to interfere in sperm maturation and epididymal function or both have not been successful. The use of transgenic animals has proved useful in identifying a few epididymal targets but has yet to open the doors for drug development. Continuous focus on identifying additional epididymal targets and sperm-specific and epididymal-specific drugs is key to bringing a male contraceptive acting on the epididymis to the public.

Post-translational modification of CASK leads to its proteasome-dependent degradation

CASK is a member of the membrane-associated guanylate kinase family. In mammals it is an essential protein, as CASK knockout mice die after birth and its deletion in humans has developmental consequences. CASK plays a role in the transcription of genes required for forebrain development, and in the nervous systems of Drosophila and C. elegans, it participates in receptor localization at the plasma membrane. This role in organizing supramolecular protein complexes to appropriate subcellular regions is shared in mammals and is regulated by phosphorylation. CASK is a kinase and regulator of cell proliferation and adhesion, which adds to an expanding list of roles. In this study we report for the first time that CASK is degraded in a characteristic fashion in mammalian cells. We found that CASK is a long-lived protein despite the fact that it contains three putative PEST sequences. Finally, we provide detailed evidence that CASK degradation is mediated through a ubiquitin-proteasome pathway and this is phosphorylation-dependent. Together, these results provide evidence that post-translational modifications to CASK are major regulatory steps leading to its proteasomal degradation. This regulation not only has important implications on how CASK participates in its many disparate roles, but highlights how altering this regulation may contribute to the pathogenesis of human disease.

[Influence of Tripterygium wilfordii on the expression of spermiogenesis related genes Herc4, Ipo11 and Mrto4 in mice]

The mechanism of Tripterygium wilfordii (GTW) inhibiting productive function was studied in the male mice. The male mice were randomly divided into control group and GTW group. GTW group had been given Tripterygium wilfordii for 8 weeks. The pregnancy rate was investigated after the male mice mated with the normal female mice (1ratio2) in one week. Also the pathological changes of the male mice testis were evaluated by the optical microscope and the expression of genes related to reproduction was investigated by Gene Chip Technology 8 weeks later. The results showed pregnancy rate of GTW group was obviously decreased compared with the control mice, and no pregnancy occurred in GTW group at 8 weeks. In the testis tissues of GTW group, the spermatogenic cells in the convoluted seminiferous tubules were obviously decreased and the lumen was obstructed by large deciduous spermatogenic cells. The number of abnormal expression genes in this group was 1 932. Among them, 354 genes were related to reproduction, including 112 up-regulated and 242 down-regulated genes. Genes Herc4, Ipo11, and Mrto4, which are closely associated with spermiogenesis, were expressed irregularly. The outcome indicates that the inhibitive reproduction of Tripterygium wilfordii in the male mice is associated with the abnormal expression of spermiogenesis genes.