Specific aspects of the ubiquitin system in spermatogenesis

Investigation of testis proteome alterations associated with male infertility in Dcaf17-deficient mice

Disruption of Dcaf17 in mice resulted in male infertility with severe spermatogenesis defects. To investigate the molecular basis of infertility phenotype, we examined testicular proteomes of wild-type (WT) and Dcaf17-/- mice using a mass spectrometry-based approach. We identified 727 and 525 differentially expressed proteins (DEPs) in 3- and 8-week old testes of Dcaf17-/- mice, respectively, with an adjusted p-value cut-off of ≤ 0.05. Among these, 299 and 298 DEPs had fold change of ≥ 1.5 between WT and Dcaf17-/- testes at -3- and 8-week old, respectively. In the 3-week old Dcaf17-/- testes, 59.5% of the DEPs were up-regulated, while 40.5% were down-regulated. Similarly, in the 8-week old Dcaf17-/- testes, 83.9% and 16.1% DEPs were up-regulated and down-regulated, respectively. Functional annotation and network analyses highlighted that many DEPs were associated with key biological processes, including ubiquitination, RNA processing, translation, protein folding, protein stabilization, metabolic processes, oxidation-reduction processes and sper-matogenesis. Subsequent immunohistochemistry and immunoblotting analyses showed higher ubiquitin levels in Dcaf17-/- testes compared to WT, suggesting potential impairment in ubiquitin proteasome system (UPS) due to DCAF17 loss of function. Our data provide a basis for further work to elucidate the molecular function(s) of DCAF17 in spermatogenesis and male fertility.

Antioncogenic roles of USP9Y and DDX3Y in lung cancer: USP9Y stabilizes DDX3Y by preventing its degradation through deubiquitination

In previous studies, downregulation of USP9Y and DDX3Y in lung cancer (LC) tissues was identified, while their function in LC progression remains elusive. In our current work, we intended to elucidate the effect and mechanisms of USP9Y and DDX3Y in LC. Gene downregulation has been confirmed in our LC tissues and cells. The effect of USP9Y or DDX3Y on LC cell malignancies was analyzed by functional assay. Both USP9Y and DDX3Y overexpression showed suppressive impact on LC cell malignancies. USP9Y overexpression has also been demonstrated to inhibit tumorigenesis in vivo. Based on GEPIA database, it was found that there was a positive correlation between the levels of USP9Y and DDX3Y in LC tissues. The mRNA expression of DDX3Y was not affected by USP9Y overexpression, while its protein levels were significantly up-regulated in USP9Y overexpressed LC cells. Moreover, USP9Y interacted with DDX3Y and has been demonstrated to stabilize DDX3Y expression by preventing its degradation via deubiquitination. In conclusion, USP9Y and DDX3Y exerted antioncogenic effects on the cell proliferation potential, cell cycle process, apoptosis, and tumorigenesis of LC. USP9Y binds to DDX3Y to prevent DDX3Y degradation through deubiquitination.

Disruption of male fertility-critical Dcaf17 dysregulates mouse testis transcriptome

During mammalian spermatogenesis, the ubiquitin proteasome system maintains protein homoeostasis (proteastasis) and spermatogenic cellular functions. DCAF17 is a substrate receptor in the ubiquitin CRL4 E3 Ligase complex, absence of which causes oligoasthenoteratozoospermia in mice resulting in male infertility. To determine the molecular phenomenon underlying the infertility phenotype caused by disrupting Dcaf17, we performed RNA-sequencing-based gene expression profiling of 3-weeks and 8-weeks old Dcaf17 wild type and Dcaf17 disrupted mutant mice testes. At three weeks, 44% and 56% differentially expressed genes (DEGs) were up- and down-regulated, respectively, with 32% and 68% DEGs were up- and down-regulated, respectively at 8 weeks. DEGs include protein coding genes and lncRNAs distributed across all autosomes and the X chromosome. Gene ontology analysis revealed major biological processes including proteolysis, regulation of transcription and chromatin remodelling are affected due to Dcaf17 disruption. We found that Dcaf17 disruption up-regulated several somatic genes, while germline-associated genes were down-regulated. Up to 10% of upregulated, and 12% of downregulated, genes were implicated in male reproductive phenotypes. Moreover, a large proportion of the up-regulated genes were highly expressed in spermatogonia and spermatocytes, while the majority of downregulated genes were predominantly expressed in round spermatids. Collectively, these data show that the Dcaf17 disruption affects directly or indirectly testicular proteastasis and transcriptional signature in mouse.

Insights into the Evolution of Spermatogenesis-Related Ubiquitin-Proteasome System Genes in Abdominal Testicular Laurasiatherians

During embryonic development in mammals, the testicles generally descend into the scrotum, making the testicular temperature 2–4 °C lower than the core temperature via heat exchange and clearance, and thus more beneficial for normal spermatogenesis. Failure to descend, known as cryptorchidism, carries a series of risks such as infertility and testicular cancer. However, some mammals have evolved abdominal testes while maintaining healthy reproduction. To explore the underlying molecular mechanism, we conducted comparative genomic analyses and functional assays on the spermatogenesis-related ubiquitin–proteasome system (UPS) genes essential to sperm formation in representative laurasiatherians. Here, positive selection and rapid evolution of spermatogenesis-related UPS genes were identified in the abdominal testicular laurasiatherians. Moreover, potential convergent amino acids were found between distantly related species with similar abdominal testicles and functional analyses showed RNF8 (V437I) in abdominal testicular species (437I) has a stronger ubiquitination ability, which suggests that the mammals with abdominal testes might exhibit enhanced sperm cell histone clearance to maintain sperm formation. This evidence implies that, in response to “cryptorchidism injury”, spermatogenesis-related UPS genes in the abdominal testicular species might have undergone adaptive evolution to stabilize sperm formation. Thus, our study could provide some novel insights into the reproductive adaptation in abdominal testicular mammals.

Novel Mutations in X-Linked, USP26-Induced Asthenoteratozoospermia and Male Infertility

Male infertility is a multifactorial disease with a strong genetic background. Abnormal sperm morphologies have been found to be closely related to male infertility. Here, we conducted whole-exome sequencing in a cohort of 150 Han Chinese men with asthenoteratozoospermia. Two novel hemizygous mutations were identified in USP26, an X-linked gene preferentially expressed in the testis and encoding a deubiquitinating enzyme. These USP26 variants are extremely rare in human population genome databases and have been predicted to be deleterious by multiple bioinformatics tools. Hematoxylin-eosin staining and electron microscopy analyses of the spermatozoa from men harboring hemizygous USP26 variants showed a highly aberrant morphology and ultrastructure of the sperm heads and flagella. Real-time quantitative PCR and immunoblotting assays revealed obviously reduced levels of USP26 mRNA and protein in the spermatozoa from men harboring hemizygous deleterious variants of USP26. Furthermore, intracytoplasmic sperm injections performed on infertile men harboring hemizygous USP26 variants achieved satisfactory outcomes. Overall, our study demonstrates that USP26 is essential for normal sperm morphogenesis, and hemizygous USP26 mutations can induce X-linked asthenoteratozoospermia. These findings will provide effective guidance for the genetic and reproductive counseling of infertile men with asthenoteratozoospermia.

DDB1- and CUL4-associated factor 8 plays a critical role in spermatogenesis

Cullin-RING E3 ubiquitin ligase (CRL)-4 is a member of the large CRL family in eukaryotes. It plays important roles in a wide range of cellular processes, organismal development, and physiological and pathological conditions. DDB1- and CUL4-associated factor 8 (DCAF8) is a WD40 repeat-containing protein, which serves as a substrate receptor for CRL4. The physiological role of DCAF8 is unknown. In this study, we constructed Dcaf8 knockout mice. Homozygous mice were viable with no noticeable abnormalities. However, the fertility of Dcaf8-deficient male mice was markedly impaired, consistent with the high expression of DCAF8 in adult mouse testis. Sperm movement characteristics, including progressive motility, path velocity, progressive velocity, and track speed, were significantly lower in Dcaf8 knockout mice than in wild-type (WT) mice. However, the total motility was similar between WT and Dcaf8 knockout sperm. More than 40% of spermatids in Dcaf8 knockout mice showed pronounced morphological abnormalities with typical bent head malformation. The acrosome and nucleus of Dcaf8 knockout sperm looked similar to those of WT sperm. In vitro tests showed that the fertilization rate of Dcaf8 knockout mice was significantly reduced. The results demonstrated that DCAF8 plays a critical role in spermatogenesis, and DCAF8 is a key component of CRL4 function in the reproductive system.

Network Medicine Approach for Analysis of Alzheimer's Disease Gene Expression Data

Alzheimer’s disease (AD) is the most widespread diagnosed cause of dementia in the elderly. It is a progressive neurodegenerative disease that causes memory loss as well as other detrimental symptoms that are ultimately fatal. Due to the urgent nature of this disease, and the current lack of success in treatment and prevention, it is vital that different methods and approaches are applied to its study in order to better understand its underlying mechanisms. To this end, we have conducted network-based gene co-expression analysis on data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. By processing and filtering gene expression data taken from the blood samples of subjects with varying disease states and constructing networks based on that data to evaluate gene relationships, we have been able to learn about gene expression correlated with the disease, and we have identified several areas of potential research interest.

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.

Ubiquitin-specific protease 26 (USP26) is not essential for mouse gametogenesis and fertility

Ubiquitin-specific protease 26 (USP26) is a deubiquitylating enzyme belonging to the USPs family with a transcription pattern restricted to the male germline. Since protein ubiquitination is an essential regulatory mechanism during meiosis, many efforts have been focused on elucidating the function of USP26 and its relationship with fertility. During the last decade, several studies have reported the presence of different polymorphisms in USP26 in patients with non-obstructive azoospermia (NOA) or severe oligozoospermia suggesting that this gene may be associated with human infertility. However, other studies have revealed the presence of these and novel polymorphisms, including nonsense mutations, in men with normal spermatogenesis as well. Thus, the results remain controversial and its function is unknown. In the present study, we describe the in vivo functional analysis of mice lacking USP26. The phenotypic analysis of two different Usp26-null mutants showed no overt-phenotype with both males and females being fertile. Cytological analysis of spermatocytes showed no defects in synapsis, chromosome dynamics, DNA repair, or recombination. Histopathological analysis revealed a normal distribution and number of the different cell types in both male and female mice. Finally, normal counts were observed in fertility assessments. These results represent the first in vivo evidence showing that USP26 is not essential for mouse gametogenesis.

Deletion of DDB1- and CUL4- associated factor-17 (Dcaf17) gene causes spermatogenesis defects and male infertility in mice

DDB1– and CUL4–associated factor 17 (Dcaf17) is a member of DCAF family genes that encode substrate receptor proteins for Cullin-RING E3 ubiquitin ligases, which play critical roles in many cellular processes. To unravel the function of DCAF17, we performed expression profiling of Dcaf17 in different tissues of wild type mouse by qRT-PCR and generated Dcaf17 knockout mice by gene targeting. Expression profiling of Dcaf17 showed highest expression in testis. Analyses of Dcaf17 transcripts during post-natal development of testis at different ages displayed gradual increase in Dcaf17 mRNA levels with the age. Although Dcaf17 disruption did not have any effect on female fertility, Dcaf17 deletion led to male infertility due to abnormal sperm development. The Dcaf17^−/− mice produced low number of sperm with abnormal shape and significantly low motility. Histological examination of the Dcaf17^−/− testis revealed impaired spermatogenesis with presence of vacuoles and sloughed cells in the seminiferous tubules. Disruption of Dcaf17 caused asymmetric acrosome capping, impaired nuclear compaction and abnormal round spermatid to elongated spermatid transition. For the first time, these data indicate that DCAF17 is essential for spermiogenesis.

Disruption of Ssp411 causes impaired sperm head formation and male sterility in mice

BACKGROUND

We previously cloned the Ssp411 gene. We found that the Ssp411 protein is predominantly expressed in elongated spermatids in the rat testis in a stage-dependent manner. Although our findings strongly suggested that Ssp411 might play an important role in mammalian spermatogenesis, this hypothesis has not been studied.

METHODS

We first used real-time PCR, Western blotting and immunohistochemistry to confirm that the expression pattern of Ssp411 in several murine tissues is similar to its expression pattern in corresponding rat tissues. To better understand the roles of Ssp411 in male reproduction in vivo, we identified and characterized an Ssp411 expression-disrupted murine strain (Ssp411^PB/PB) that was generated by piggyBac (PB) transposon insertion. We studied Ssp411-interacting proteins using proteome microarray, co-IP and GST pull-down assay.

RESULTS

Both Ssp411 mRNA and protein were detected exclusively in spermatids after step 9 during spermiogenesis in testis. Phenotypic analysis suggested that only Ssp411^PB/PB males are sterile. These males have smaller testes, reduced sperm counts, decreased sperm motility and deformed spermatozoa. Microscopy analysis indicated that the manchette, a structurally reshaped sperm head, is aberrant in Ssp411^PB/PB spermatids. The results of proteome microarray analysis and GST pull-down assays suggested that Ssp411 participates the ubiquitin-proteasome system by interacting with PSMC3. This has been reported to be manchette-associated and important for the head shaping of spermatids.

CONCLUSIONS

Our study suggested that Ssp411 is required for spermiogenesis. It seems to play a role in sperm head shaping. The lack of Ssp411 causes sperm deformation and results in male infertility.

GENERAL SIGNIFICANCE

Ssp411^PB/PB mouse strain is an animal model of idiopathic oligoasthenoteratozoospermia (iOAT), and the gene may represent a therapeutic target for iOAT patients.

Ubiquitin Carboxy-Terminal HydrolaseL3 Correlates with Human Sperm Count, Motility and Fertilization

Ubiquitin C-terminal hydrolase L3 (UCHL3) belongs to the group of deubiquitinating enzymes and plays a part in apoptosis of germ cells and the differentiation of spermatocytes into spermatids. However, the exact role of UCHL3 in human spermatogenesis and sperm function remains unknown. Here we examined the level and activity of UCHL3 in spermatozoa from men with asthenozoospermia (A), oligoasthenozoospermia (OA) or normozoospermia (N). Immunofluorescence indicated that UCHL3 was mainly localized in the acrosome and throughout the flagella, and western blotting revealed a lower level in A or OA compared with N (p < 0.05). The catalytic activity of UCHL3 was decreased in spermatozoa from A or OA (p < 0.05, p < 0.001, respectively). The level and activity of UCHL3 were positively correlated with sperm count, concentration and motility. The UCHL3 level was positively correlated with the normal fertilization rate (FR) and percentage of embryos suitable for transfer/cryopreservation of in vitro fertilization (IVF). The UCHL3 activity was also positively correlated with FR, the percentage of embryos suitable for transfer/cryopreservation and high-quality embryos rate of IVF. Aforementioned correlations were not manifested in intra-cytoplasmic sperm injection (ICSI). These findings suggest that UCHL3 may play a role in male infertility.

Single nucleotide polymorphisms of USP26 in azoospermic men

Some studies have focused on the association between male infertility and single nucleotide polymorphisms (SNPs) in the ubiquitin-specific protease 26 (USP26) gene, but the results are controversial. In this case-control study including both normozoospermic men and patients with nonobstructive azoospermia, we analyzed both the entire coding region and 5' and 3' untranslated regions of USP26 in order to identify genetic variants in this gene to investigate the role of USP26 on spermatogenesis. We reported variations in the USP26 gene sequence in 82% of azoospermic and in 50% normospermic men. The synonymous variation c.576G>A has a frequency significantly different in the azoospermic (60.2%) and normozoospermic (23.6%) groups, while the frequencies in the two groups of both c.1090C>T and c.1737G>A missense mutations did not reach statistical significance. A cluster mutation (c.371insACA, c.494T>C) was detected in 2 normozoospermic men (2.7%). In the 5'UTR we identified the -33C>T variation both in azoospermic (3.8%) and in normozoospermic (2.7%) men. In a normozoospermic man we detected the nonsense mutation c.882C>A, never reported to date. According to our results, we suggest that only the variation c.576G>A has a frequency significantly different in azoospermic compared to normozoospermic men. Moreover, the identification in a normozoospermic man of a nonsense mutation (c.882C>A) which causes the production of a truncated protein, suggests a marginal role of USP26 in male spermatogenesis. Additional studies may be useful as we cannot exclude that the other SNPs may represent risk factors for male fertility acting by an oligogenic/polygenic mechanism.

Post-Translational Modifications of Histones in Human Sperm

We examined the levels and distribution of post-translationally modified histones and protamines in human sperm. Using western blot immunoassay, immunofluorescence, mass spectrometry (MS), and FLIM-FRET approaches, we analyzed the status of histone modifications and the protamine P2. Among individual samples, we observed variability in the levels of H3K9me1, H3K9me2, H3K27me3, H3K36me3, and H3K79me1, but the level of acetylated (ac) histones H4 was relatively stable in the sperm head fractions, as demonstrated by western blot analysis. Sperm heads with lower levels of P2 exhibited lower levels of H3K9ac, H3K9me1, H3K27me3, H3K36me3, and H3K79me1. A very strong correlation was observed between the levels of P2 and H3K9me2. FLIM-FRET analysis additionally revealed that acetylated histones H4 are not only parts of sperm chromatin but also appear in a non-integrated form. Intriguingly, H4ac and H3K27me3 were detected in sperm tail fractions via western blot analysis. An appearance of specific histone H3 and H4 acetylation and H3 methylation in sperm tail fractions was also confirmed by both LC-MS/MS and MALDI-TOF MS analysis. Taken together, these data indicate that particular post-translational modifications of histones are uniquely distributed in human sperm, and this distribution varies among individuals and among the sperm of a single individual.

Stage-specific signaling pathways during murine testis development and spermatogenesis: A pathway-based analysis to quantify developmental dynamics

Shifting the field of developmental toxicology toward evaluation of pathway perturbation requires a quantitative definition of normal developmental dynamics. This project examined a publicly available dataset to quantify pathway dynamics during testicular development and spermatogenesis and anchor toxicant-perturbed pathways within the context of normal development. Genes significantly changed throughout testis development in mice were clustered by their direction of change using K-means clustering. Gene Ontology terms enriched among each cluster were identified using MAPPfinder. Temporal pathway dynamics of enriched terms were quantified based on average expression intensity for all genes associated with a given term. This analysis captured processes that drive development, including the peak in steroidogenesis known to occur around gestational day 16.5 and the increase in meiosis and spermatogenesis-related pathways during the first wave of spermatogenesis. Our analysis quantifies dynamics of pathways vulnerable to toxicants and provides a framework for quantifying perturbation of these pathways.

Bortezomib treatment causes long-term testicular dysfunction in young male mice

Background

With increased long-term survivors of childhood cancer patients, therapy-associated infertility has become one of the most common late side-effects and significantly affects their life-quality. Therefore, evaluation of anti-cancer agents on male reproduction and infertility prevention are urgently demanding. The proteasome inhibitor bortezomib has been launched in clinical trials for childhood cancers, however, its potential side effects on reproduction have so far been neither investigated experimentally nor reported in treated children. Thus the present study is designed to explore the impact of bortezomib on male reproductive function and to gain insights into how bortezomib exerts its adverse effects on man gonad, thereby providing pediatric oncologists relevant information.

Methods

35 day-old male mice were treated with one 11-day cycle of bortezomib and then sacrificed 2 days, 45 days, or 6 months later. A mating study was performed in the group followed for 6 months, and their pups were analyzed on postnatal day 50. Serum follicle-stimulating hormone (FSH) and testicular testosterone levels were measured. Testicular morphology was evaluated by light- and electron microscopy, and the underlying mechanisms and pathways of testis damage were investigated.

Results

Testicular damage was visible already 2 days after stopping bortezomib and increased in severity by day 45. Then 80% of seminiferous tubules exhibited hypospermatogenesis with arrest at the levels of spermatogonia, spermatocytes and round spermatids. Germ cells were specifically targeted by bortezomib as evidenced by increased apoptosis mediated through activation of p53 and caspases. Even six months after the bortezomib treatment, testis weight, sperm concentration and seminiferous tubule length remained at a decreased level, indicating that spermatogenesis and tubular outgrowth could not fully recover. Combined with persistently increased serum levels of FSH in these mice, our results demonstrate that bortezomib can have long-term effects on testicular function, although fertility of bortezomib-exposed males remained and their offspring looked healthy.

Conclusion

Bortezomib treatment causes long-term gonadal dysfunction in male mice. Careful monitoring of gonadal function in male childhood cancer patients treated with bortezomib is thus strongly recommended.

Ubiquitin Specific Protease 26 (USP26) expression analysis in human testicular and extragonadal tissues indicates diverse action of USP26 in cell differentiation and tumorigenesis

Ubiquitin specific protease 26 (USP26), a deubiquitinating enzyme, is highly expressed early during murine spermatogenesis, in round spermatids, and at the blood-testis barrier. USP26 has also been recognized as a regulator of androgen receptor (AR) hormone-induced action involved in spermatogenesis and steroid production in in vitro studies. Prior mutation screening of USP26 demonstrated an association with human male infertility and low testosterone production, but protein localization and expression in the human testis has not been characterized previously. USP26 expression analysis of mRNA and protein was completed using murine and human testis tissue and human tissue arrays. USP26 and AR mRNA levels in human testis were quantitated using multiplex qRT-PCR. Immunofluorescence colocalization studies were performed with formalin-fixed/paraffin-embedded and frozen tissues using primary and secondary antibodies to detect USP26 and AR protein expression. Human microarray dot blots were used to identify protein expression in extra-gonadal tissues. For the first time, expression of USP26 and colocalization of USP26 with androgen receptor in human testis has been confirmed predominantly in Leydig cell nuclei, with less in Leydig cell cytoplasm, spermatogonia, primary spermatocytes, round spermatids, and Sertoli cells. USP26 likely affects regulatory proteins of early spermatogenesis, including androgen receptor with additional activity in round spermatids. This X-linked gene is not testis-specific, with USP26 mRNA and protein expression identified in multiple other human organ tissues (benign and malignant) including androgen-dependent tissues such as breast (myoepithelial cells and secretory luminal cells) and thyroid tissue (follicular cells). USP26/AR expression and interaction in spermatogenesis and androgen-dependent cancer warrants additional study and may prove useful in diagnosis and management of male infertility.

Differential expression of speckled POZ protein, SPOP: putative regulation by miR-145

The speckle POZ protein, SPOP, is an adaptor of the Cul3-based ubiquitination process, and has been implicated in the carcinogenesis process. Despite recent elucidation of biological functions, regulation of SPOP gene expression has not been reported. In this study, the mRNA levels of the mouse SPOP (mSPOP) gene were first shown to vary noticeably in different tissues. However, the SPOP protein was detected in high abundance only in Purkinje cells of the cerebellum and seminiferous tubule of the testis, echoing previous reports of involvement of ubiquitination in neuron cells and in spermatogenesis. In other mouse tissues and human cancer cell lines analysed, only low SPOP protein levels were detected. The 3'-untranslated regions of both the mSPOP and human SPOP transcripts harbor a conserved putative miR-145 binding site (BS). In some tissues and cell lines, miR-145 and SPOP protein levels were in an inverse relationship suggesting miR-145 regulation. Luciferase assays of deletion and point mutation constructs of the miR-145 BS, and miR-145 induction by serum starvation that resulted in reduced endogenous SPOP levels provided further evidence that miR-145 is likely involved in post-transcriptional regulation of SPOP expression in selected tissues, and possibly with the participation of other miRNA species.

The polyubiquitin gene Ubi-p63E is essential for male meiotic cell cycle progression and germ cell differentiation in Drosophila

The ubiquitin proteasome system (UPS) regulates many biological pathways by post-translationally ubiquitylating proteins for degradation. Although maintaining a dynamic balance between free ubiquitin and ubiquitylated proteins is key to UPS function, the mechanisms that regulate ubiquitin homeostasis in different tissues through development are not clear. Here we show, via analysis of the magellan (magn) complementation group, that loss of function of the Drosophila polyubiquitin Ubi-p63E results specifically in meiotic arrest sterility in males. Ubi-p63E contributes predominantly to maintaining the free ubiquitin pool in testes. The function of Ubi-p63E is required cell-autonomously for proper meiotic chromatin condensation, cell cycle progression and spermatid differentiation. magn mutant germ cells develop normally to the spermatocyte stage but arrest at the G2/M transition of meiosis I, with lack of protein expression of the key meiotic cell cycle regulators Boule and Cyclin B. Loss of Ubi-p63E function did not strongly affect the spermatocyte transcription program regulated by the testis TBP-associated factor (tTAF) or meiosis arrest complex (tMAC) genes. Knocking down proteasome function specifically in spermatocytes caused a different meiotic arrest phenotype, suggesting that the magn phenotype might not result from general defects in protein degradation. Our results suggest a conserved role of polyubiquitin genes in male meiosis and a potential mechanism leading to meiosis I maturation arrest.

Ubiquitin-specific protease (USP26) gene alterations associated with male infertility and recurrent pregnancy loss (RPL) in Iranian infertile patients

BACKGROUND AND PURPOSE

The human X chromosome is enriched with testis-specific genes that may be crucial for male fertility. Mutations in USP26 gene have been proposed to be associated with male infertility. Moreover, the importance of the ubiquitin pathway during different stages of mammalian fertilization and even embryo development has been addressed. Some mutations and haplotypes on this gene have been proposed to be associated with male infertility. In this study, five different mutations on USP26 were investigated: 1737 G > A, 1090 C > T, 370-371ins ACA, 494 T > C and 1423 C > T.

METHODS

The study included 166 infertile men with non-obstructive azoospermia, 72 male partners of couples who had previously experienced ≥3 clinical first trimester spontaneous abortions and 60 fertile men. Besides family history of reproduction, hormonal evaluation and semen analysis were performed. DNA was extracted from blood samples. PCR-SSCP, PCR-RFLP and PCR Product Cloning methods were used and resumed by sequencing to insure about the mutations. Moreover, USP26 gene expression was studied by Real-Time PCR after RNA extraction followed by cDNA synthesis from 24 testis biopsies in obstructive and non-obstructive azoospermia patients.

RESULTS

The results indicate that there is a haplotype between three observed mutations in Iranian population include: 370-371insACA, 1423C > T and 494 T > C. This haplotype was seen in control group as well. Surprisingly, total frequency of mutations in men with history of idiopathic RPL and azoospermic cases were significantly higher than that of in control groups (p < 0.05). Serum testosterone concentrations and testicular volume did not differ in the mutation positive group compared with the non-mutation group. About the USP26 gene expression, there is a significant difference between the expression levels of obstructive azoospermia, complete maturation arrest samples and SCO samples (P < 0.05).

CONCLUSIONS

According to our results, the USP26 gene may play an important role in male reproduction. The alterations of this gene may be involved in male infertility and RPL in Iranian population and may negatively affect testicular function.

Cloning, genomic structure and expression analysis of ubc9 in the course of development in the half-smooth tongue sole (Cynoglossus semilaevis)

The small ubiquitin-like modifier (SUMO) pathway is an essential biological process in eukaryote, and Ubc9 is an important E2 conjugating enzyme (UBE2) for SUMO pathway and plays a critical role in cellular differentiation, development and sex modification in various species. However, the relationship between Ubc9 and sex modification and development in fish remains elusive. To elucidate the impact of Ubc9 on sex modification and development, the full length of the cDNA and genomic sequence was cloned from half-smooth tongue sole, Cynoglossus semilaevis. Real-time quantitative RT-PCR demonstrated that ubc9 was ubiquitously expressed in different tissues, and the expression levels varied in the different stages of embryonic and gonadal development. In addition, the expression level was significantly higher in the temperature-treated females than the normal females and males. Moreover, the PET-32-Ubc9 plasmid was constructed and the recombinant protein was expressed in Escherichia coli. Follistatin gene expression was initially up-regulated and FSE genes (cyp19a1a, ctnnb1, foxl2) were initially down-regulated after the injection of Ubc9 protein, prior to 96 h eventually recovered to normal levels. Taken together, the results show that Ubc9 is involved in embryogenesis, gametogenesis and sex modification, and exerts an effect on gene expression.

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.

The role of Drosophila hyperplastic discs gene in spermatogenesis

In Drosophila, the ubiquitin ligase Hyd (hyperplastic disc) is required for regulation of cell proliferation during development [Martin et al. (1977) Dev Biol 55, 213-232; Mansfield et al. (1994) Dev Biol 165, 507-526]. Earlier, we demonstrated that the Drosophila tumour suppressor Merlin participates not only in imaginal discs proliferation control, but also performs a separate Nebenkern structural function in Drosophila spermatogenesis [Dorogova et al. (2008) BMC Cell Biol 9, 1. Here, we show that the hyd mutants also have spermatogenesis defects: chromosome condensation and attachment to the spindle, centrosome behaviour and cytokinesis in meiosis. The process of spermatid elongation was also greatly affected: nuclei were scattered along the cyst and had an abnormal shape, Nebenkern-axoneme angular relation and attachment was distorted, axonemes themselves lost correct structure. Since Hyd and pAbp protein families share a common PABC [poly(A)-binding protein C-terminal] protein domain, we also studied spermatogenesis in pAbp homozygotes and found defects in cytokinesis and spermatid elongation. However, our study of hyd and pAbp genetic interaction revealed only the phenotype of defective nuclei shape at the final stage of spermatid differentiation. So, the PABC domain is unlikely to be responsible for meiotic defects. Thus, our data document that, in addition to the tumour suppressor Merlin, another tumour suppressor, Hyd, also has a function in spermatogenesis.

Knobbed acrosome defect is associated with a region containing the genes STK17b and HECW2 on porcine chromosome 15

BACKGROUND

Male infertility is an increasing problem in all domestic species including man. Localization and identification of genes involved in defects causing male infertility provide valuable information of specific events in sperm development. Correct condensation of the sperm head and development of the acrosome are required for fertile sperm. In the Finnish Yorkshire pig population a knobbed acrosome defect (KAD) has been reported which appears to be of genetic origin. In previous studies we have shown that a large number of affected spermatozoa have a cystic swelling anterior to the apical part of the acrosome.

RESULTS

Characterization of the knobbed acrosome affected sperm revealed that both the acrosomal granules and chromatin are affected. This type of KAD appears to be a previously unknown and serious form of the defect. A genome wide scan with PorcineSNP60 Genotyping BeadChip defined the KAD associated region within 0.7 Mbp on porcine chromosome 15. Two genes, STK17b and HECW2, located within this region were sequenced. The expression of these genes appeared comparable in KA-affected and control boars. The known function of HECW2 in acrosome development highlighted this gene as a good candidate responsible for the KAD. One nonsynonymous SNP was identified within the HECW2 gene. However, as this mutation was found in homozygous state in individuals with normal sperm, this is not likely to be the causal mutation.

CONCLUSIONS

In this study we identified two candidate genes for a severe defect affecting both the sperm acrosome and chromatin that causes infertility. One of these genes, HECW2, plays an important role in ubiquitination, a prerequisite for chromatin remodelling and acrosome formation, highlighting the involvement of this gene in the knobbed acrosome defect and male infertility.

Genetic dissection of the AZF regions of the human Y chromosome: thriller or filler for male (in)fertility?

The azoospermia factor (AZF) regions consist of three genetic domains in the long arm of the human Y chromosome referred to as AZFa, AZFb and AZFc. These are of importance for male fertility since they are home to genes required for spermatogenesis. In this paper a comprehensive analysis of AZF structure and gene content will be undertaken. Particular care will be given to the molecular mechanisms underlying the spermatogenic impairment phenotypes associated to AZF deletions. Analysis of the 14 different AZF genes or gene families argues for the existence of functional asymmetries between the determinants; while some are prominent players in spermatogenesis, others seem to modulate more subtly the program. In this regard, evidence supporting the notion that DDX3Y, KDM5D, RBMY1A1, DAZ, and CDY represent key AZF spermatogenic determinants will be discussed.

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.

Male infertility and the involvement of the X chromosome

BACKGROUND

Male infertility is a worldwide problem, keeping many researchers puzzled. Besides environmental factors, much attention is paid to single gene defects. In this view, the sex chromosomes are particularly interesting since men only have a single copy of these chromosomes. The involvement of the Y chromosome in male infertility is obvious since the detection of Yq microdeletions. The role of the X chromosome, however, remains less understood.

METHODS

Articles were obtained by searching PubMed until December 2008. A first search attempted to identify genes located on the X chromosome potentially important for spermatogenesis. A second part of the study was focused on those genes for which the role has already been studied in infertile patients.

RESULTS

Multiple genes located on the X chromosome are expressed in testicular tissues. The function of many genes, especially the cancer-testis genes, has not been studied so far. There were striking differences between mouse and human genes. In the second part of the study, the results of mutation analyses of seven genes (AR, SOX3, USP26, NXF2, TAF7L, FATE and AKAP4) are described. Except for AR, no infertility causing mutations have, thus far, been described. It cannot be excluded that some of the observed changes should be considered as risk factors for impaired spermatogenesis.

CONCLUSIONS

It can be concluded that, so far, the mutation analysis of X-linked genes in humans, presumed to be crucial for spermatogenesis or sperm quality, has been disappointing. Other approaches to learn more about male infertility are necessary.

The expression of Usp26 gene in mouse testis and brain

Deubiquitinating enzymes (DUBs) play an important role in ubiquitin-dependent processes as negative regulators of protein ubiquitination. Ubiquitin-specific protease 26 (USP26) is a member of this family. The expression of Usp26 in mammalian testis and in other tissues has yet to be fully elucidated. To study the expression of Usp26 mRNA and protein in various murine tissues, reverse transcription (RT)-PCR and immunohistochemistry analyses were carried out. The RT-PCR analysis showed that the Usp26 transcript was expressed in all of the tested tissues. USP26 protein localization was examined by immunohistochemistry, and it was shown that USP26 was not detectable at 20 days postpartum, with the expression restricted to the cytoplasm of condensing spermatids (steps 9-16), Leydig cells and nerve fibers in the brain. In addition, the USP26 protein was detected at moderate levels in myocardial cells, the corpus of epidydimis, epithelium of the renal tubules and the seminal gland of postnatal day 35 mice. Its spatial and temporal expression pattern suggests that Usp26 may play an important role in development or function of the testis and brain. Further research into these possibilities is in progress.

Association of USP26 haplotypes in men in Taiwan, China with severe spermatogenic defect

AIM

To complete comprehensive haplotype analysis of USP26 for both fertile and infertile men.

METHODS

Two hundred infertile men with severe oligospermia or non-obstructive azoospermia were subjected to sequence analysis for the entire coding sequences of the USP26 gene. Two hundred men with proven fertility were genotyped by primer extension methods. Allele/genotype frequencies, linkage disequilibrium (LD) characteristics and haplotypes of fertile men were compared with infertile men.

RESULTS

The allele frequencies of five single nucleotide polymorphisms (370-371insACA, 494T>C, 576G>A, ss6202791C>T, 1737G>A) were significantly higher in infertile patients than control subjects. The major haplotypes in infertile men were TACCGA (28% of the population), TGCCGA (15%), TACCAA (8%), TGCCAA (6%), TATCAA (5%) and CATCAA (5%). The major haplotypes for the control subjects were TACCGA (58% of the population), CACCGA (7%), CATCGA (6%) and TGCCGA (5%). Haplotypes TGCCGA, TATCAA, CATCAA, CATCGC, TACCAA and TGCCAA were over-transmitted in patients with spermatogenic defect, whereas haplotypes TACCGA, CACCGA, and CATCGA were under-transmitted in these patients.

CONCLUSION

Some USP26 alleles and haplotypes are associated with spermatogenic defect in the Han nationality in Taiwan, China.

Regulated expression of the ubiquitin protein ligase, E3(Histone)/LASU1/Mule/ARF-BP1/HUWE1, during spermatogenesis

A ubiquitin protein ligase (E3), E3(Histone)/LASU1 (Mule/ARF-BP1/HUWE1), was recently identified that mediates ubiquitination of core histones, the Mcl-1 anti-apoptotic protein, and the p53 tumor suppressor protein. However, the expression of E3(Histone)/LASU1 remains poorly studied. Because we identified E3(Histone)/LASU1 from the testis, we explored its regulation during spermatogenesis. In the first wave of rat spermatogenesis, E3(Histone)/LASU1 mRNA and protein had peak expression at days 10 and 20, respectively, and decreased with age. Consistent with these findings, immunohistochemistry revealed that E3(Histone)/LASU1 was highly expressed in nuclei from spermatogonia to mid-pachytene spermatocytes. There was no obvious staining in spermatids, when histones are ubiquitinated and degraded. E3(Histone)/LASU1 was also expressed in other tissues. However, except in neuronal cells of the brain, expression was cytoplasmic. Thus, E3(Histone)/LASU1 may play a role in chromatin modification in early germ cells of the testis, but also has functions in other tissues.

Biology of sperm chromatin structure and relationship to male fertility and embryonic survival

Embryonic mortality in mammals is typically thought to result from 'female factor' infertility. There is growing evidence, however, that the status of sperm chromatin (DNA) at the time of fertilisation can also influence embryonic survival. During the final stages of spermatogenesis (spermiogenesis) a number of unique biochemical, morphological and physiological processes take place that are associated with marked changes in the structure of sperm chromatin. In early stages of spermatogenesis, sperm DNA is associated with histone nucleoproteins and structured into classical nucleosome core particles similar to other somatic cells. As spermiogenesis proceeds, the histone nucleoproteins are replaced by transition proteins which are subsequently replaced by protamines. At the completion of spermiogenesis the chromatin of mature sperm has a toroidal structure that is tightly compacted and resistant to denaturation. The compaction is necessary to protect sperm chromatin during transit through the epididymis and female reproductive tract. Disruption to chromatin remodelling during spermiogenesis results in chromatin that is susceptible to denaturation. Inappropriate chromatin structure has been shown in a number of mammalian species to be related to male infertility, and specifically the failure of embryonic development. A range of techniques are available to assess chromatin status in sperm but arguably the most informative is the sperm chromatin structure assay (SCSA). The SCSA is a flow cytometric assay that uses the metachromatic properties of acridine orange to measure the susceptibility of sperm chromatin to acid-induced denaturation. A relationship has been demonstrated, primarily in men, between the SCSA outcome and the probability of continued embryonic development and the establishment of pregnancy after fertilisation. The contribution of sperm chromatin instability to reproductive wastage in both natural mating and assisted reproduction warrants further investigation as it may prove valuable as a means of decreasing the incidence of embryonic mortality. In this regard, it is possible that 'male factor' infertility may emerge as an even more important component in embryonic development.

The New Function of Two Ubiquitin C-Terminal Hydrolase Isozymes as Reciprocal Modulators of Germ Cell Apoptosis

Ubiquitination is required throughout all developmental stages of mammalian spermatogenesis. The two ubiquitin C-terminal hydrolase (UCH) enzymes, UCH-L1 and UCH-L3, deubiquitinate ubiquitin-protein conjugates and control the cellular balance of ubiquitin. These two UCH isozymes have 52% amino acid identity and share significant structural similarity. A new function of these two closely related UCH enzymes during spermatogenesis which is associated with germ cell apoptosis has been analyzed. Apoptosis, in general, is thought to be partly regulated by the ubiquitin-proteasome system. During spermatogenesis, apoptosis controls germ cell numbers and eliminates defective germ cells to facilitate testicular homeostasis. In this paper, I review the distinct function of the two UCH isozymes in the testis of gad and Uchl3 knockout mice, which are strongly but reciprocally expressed during spermatogenesis. In addition, the importance of UCHL1-dependent apoptosis for normal spermatogenesis and sperm quality control is discussed.

Alterations of the USP26 gene in Caucasian men

The Ubiquitin Specific Protease 26 gene is a testis-specific gene that is located on the X chromosome. Sequence variants of this gene were previously reported in men with azoospermia caused by defects at the level of spermatogenesis. Especially a cluster of three changes (c.370_371insACA, c.494T>C and c.1423C>T) was frequently observed. To further define the role of this cluster of sequence variants in the USP26 gene, we have now analysed 202 control samples and 146 patients of Caucasian origin with cryptozoospermia or oligozoospermia. The detection method was based on a restriction reaction, by which the change c.494T>C can be detected. In none of the patients, the change c.494T>C was observed. Only in one man with normal spermatogenesis this sequence variant was detected. Sequencing can confirm the presence of the three changes of the USP26 gene. These data indicate that the cluster of changes is not restricted to men with severe testicular dysfunction.

Pachytene asynapsis drives meiotic sex chromosome inactivation and leads to substantial postmeiotic repression in spermatids

Transcriptional silencing of the sex chromosomes during male meiosis (MSCI) is conserved among organisms with limited sex chromosome synapsis, including mammals. Since the 1990s the prevailing view has been that MSCI in mammals is transient, with sex chromosome reactivation occurring as cells exit meiosis. Recently, we found that any chromosome region unsynapsed during pachytene of male and female mouse meiosis is subject to transcriptional silencing (MSUC), and we hypothesized that MSCI is an inevitable consequence of this more general meiotic silencing mechanism. Here, we provide direct evidence that asynapsis does indeed drive MSCI. We also show that a substantial degree of transcriptional repression of the sex chromosomes is retained postmeiotically, and we provide evidence that this postmeiotic repression is a downstream consequence of MSCI/MSUC. While this postmeiotic repression occurs after the loss of MSUC-related proteins at the end of prophase, other histone modifications associated with transcriptional repression have by then become established.

The region-specific functions of two ubiquitin C-terminal hydrolase isozymes along the epididymis

We previously showed that gad mice, which are deficient for ubiquitin C-terminal hydrolase L1 (UCH-L1), have a significantly increased number of defective spermatozoa, suggesting that UCH-L1 functions in sperm quality control during epididymal maturation. The epididymis is the site of spermatozoa maturation, transport and storage. Region-specific functions along the epididymis are essential for establishing the environment required for sperm maturation. We analyzed the region-specific expression of UCH-L1 and UCH-L3 along the epididymis, and also assessed the levels of ubiquitin, which has specificity for UCH-L1. In wild-type mice, western blot analysis demonstrated a high level of UCH-L1 expression in the caput epididymis, consistent with ubiquitin expression, whereas UCH-L3 expression was high in the cauda epididymis. We also investigated the function of UCH-L1 and UCH-L3 in epididymal apoptosis induced by efferent duct ligation. The caput epididymides of gad mice were resistant to apoptotic stress induced by efferent duct ligation, whereas Uchl3 knockout mice showed a marked increase in apoptotic cells following ligation. In conclusion, the response of gad and Uchl3 knockout mice to androgen withdrawal suggests a reciprocal function of the two UCH enzymes in the caput epididymis.

Cullin3 is a KLHL10-interacting protein preferentially expressed during late spermiogenesis

Kelch-like 10 (KLHL10) is a member of the BTB (Bric-a-brac, Tramtrack, and Broad-Complex)-kelch protein superfamily essential for spermiogenesis and male fertility. In a search for KLHL10-interacting proteins using a yeast two-hybrid assay, we identified Cullin3 (CUL3) as one of multiple KLHL10-interacting partners. Yeast cotransformation assays revealed that CUL3 bound the BTB/POZ domain of KLHL10. Northern blot and quantitative RT-PCR analyses demonstrated that Cul3 mRNA was preferentially expressed in the testis. In situ hybridization analysis localized Cul3 mRNA to spermatids in the adult testis. CUL3 protein was detected in elongating and elongated spermatids (steps 10-16) by immunofluorescent microscopy. The expression pattern of CUL3 resembles KLHL10. CUL3 was coimmunoprecipated with KLHL10, and KLHL10 was also detected in the CUL3 immunoprecipitants using testis lysates. These findings suggest that KLHL10, like other BTB/kelch proteins, interacts with CUL3 to form a CUL3-based ubiquitin E3 ligase that functions specifically in the testis to mediate protein ubiquitination during spermiogenesis.

Possible role of USP26 in patients with severely impaired spermatogenesis

The ubiquitin-specific protease 26 (USP26) gene is an X-linked gene specifically expressed in testis tissue. This gene is therefore a potential infertility gene. In order to analyse its possible involvement in spermatogenesis and infertility, 42 patients with Sertoli cell-only syndrome were analysed for mutations in this gene. We found four patients with exactly the same three changes of the nucleotide and therefore also amino acid sequence. These patients showed 370-371insACA, 494T>C and 1423C>T causing T123-124ins, L165S and H475Y, respectively. These changes were not found in 10 control samples. Furthermore, two polymorphisms were observed which do not alter the amino-acid sequence. A restriction analysis that can make a distinction between a T and a C, at position 494, was set up in order to examine more patient and control samples. Another 69 patients with Sertoli cell-only syndrome, 32 patients with maturation arrest and 142 control samples were analysed using this method. None of the control samples or patients with maturation arrest featured the change at position 494. However, four more patients with Sertoli cell-only syndrome were identified with the three alterations. The frequency of alterations in this group is therefore 7.2% (8/111). One of the patients had a deletion of the long arm of the Y chromosome, while another patient had a varicocoele. These results indicate that these alterations might be involved in male infertility or might increase the risk of male infertility.

Replacement by Drosophila melanogaster protamines and Mst77F of histones during chromatin condensation in late spermatids and role of sesame in the removal of these proteins from the male pronucleus

Chromatin condensation is a typical feature of sperm cells. During mammalian spermiogenesis, histones are first replaced by transition proteins and then by protamines, while little is known for Drosophila melanogaster. Here we characterize three genes in the fly genome, Mst35Ba, Mst35Bb, and Mst77F. The results indicate that Mst35Ba and Mst35Bb encode dProtA and dProtB, respectively. These are considerably larger than mammalian protamines, but, as in mammals, both protamines contain typical cysteine/arginine clusters. Mst77F encodes a linker histone-like protein showing significant similarity to mammalian HILS1 protein. ProtamineA-enhanced green fluorescent protein (eGFP), ProtamineB-eGFP, and Mst77F-eGFP carrying Drosophila lines show that these proteins become the important chromosomal protein components of elongating spermatids, and His2AvDGFP vanishes. Mst77F mutants [ms(3)nc3] are characterized by small round nuclei and are sterile as males. These data suggest the major features of chromatin condensation in Drosophila spermatogenesis correspond to those in mammals. During early fertilization steps, the paternal pronucleus still contains protamines and Mst77F but regains a nucleosomal conformation before zygote formation. In eggs laid by sesame-deficient females, the paternal pronucleus remains in a protamine-based chromatin status but Mst77F-eGFP is removed, suggesting that the sesame gene product is essential for removal of protamines while Mst77F removal is independent of Sesame.

Expression and possible functions of DNA lesion bypass proteins in spermatogenesis

In mammalian cells, there is a complex interplay of different DNA damage response and repair mechanisms. Several observations suggest that, in particular in gametogenesis, proteins involved in DNA repair play an intricate role in and outside the context of DNA repair. Here, we discuss the possible roles of proteins that take part in replicative damage bypass (RDB) mechanisms, also known as post-replication DNA repair (PRR), in germ line development. In yeast, and probably also in mammalian somatic cells, RDB [two subpathways: damage avoidance and translesion synthesis (TLS)] prevents cessation of replication forks during the S phase of the cell cycle, in situations when the replication machinery encounters a lesion present in the template DNA. Many genes encoding proteins involved in RDB show an increased expression in testis, in particular in meiotic and post-meiotic spermatogenic cells. Several RDB proteins take part in protein ubiquitination, and we address relevant aspects of the ubiquitin system in spermatogenesis. RDB proteins might be required for damage avoidance and TLS of spontaneous DNA damage during gametogenesis. In addition, we consider the possible functional relation between TLS and the induction of mutations in spermatogenesis. TLS requires the activity of highly specialized polymerases, and is an error-prone process that may induce mutations. In evolutionary terms, controlled generation of a limited number of mutations in gametogenesis might provide a mechanism for evolvability.

Transcriptional analysis of testis maturation using trout cDNA macroarrays

The project seeks to identify genes involved in key stages of trout spermatogenesis and their regulation. Within the framework of the French project of farm animal genomics (AGENAE) we produced an original normalised trout testis cDNA library and obtained 1152 trout ESTs corresponding to 967 potential genes. To study the expression of those genes throughout first stages of spermatogenesis, we used nylon macroarray. Gonads in stage of immaturity (stage I), or at initiation of spermatogonial proliferation (stage II), meiosis (stage III) or spermiogenesis were selected by histological analysis. Total RNA was extracted and then used to produce complex targets labelled with [33P]dCTP and hybridised with cDNA arrays. After filtering and normalisation of hybridisation signals, genes presenting differential expression as revealed by ANOVA analysis were submitted to k-means clustering and hierarchical classification. Genes were separated into five clusters which presented distinct profiles. One cluster overexpressed in stage I could be involved in the initial events of spermatogenesis as seminiferous tubule organisation. The second cluster displays a transient increase at the beginning of testicular recrudescence (stage II). Three other clusters group several genes involved in cell proliferation and protein synthesis and modification. One is particularly down-expressed during stage I, the two others show increased expression during stages III and IV and appear to be involved in spermatogonial and meiotic proliferation and in protein metabolism linked to cellular growth. This allows us to plan further experiments to better understand the functional implication of some of the genes that are found to be significantly regulated like CDC2, hematological and neurological expressed gene 1-like protein, HCDI protein, Mago Nashi, a BMP-like, and a steroid receptor binding protein. These data demonstrate the applicability of the array based technology using our trout cDNA arrays and highlight genes that are potential targets for the control of puberty and fertility in farmed fish.

Ubiquitin-specific protease activity of USP9Y, a male infertility gene on the Y chromosome

Deletions of USP9Y have been observed among infertile males with defective spermatogenesis. Therefore, the gene has been designated as a male infertility gene on the Y chromosome. However, it remains to be determined how male infertility results from deletions of this gene. In order to initiate an investigation into the cellular functions of USP9Y in male germ cell development, in the present study we characterized the enzymatic specificity of USP9Y. Our results show that both USP9Y and Fam, the mouse infertility protein Usp9x, possess a protease activity specific to ubiquitin. These results suggest that, through de-ubiquitination, USP9Y may stabilize a specific target protein that is important for male germ cell development.

Ubiquitin C-terminal hydrolase L-1 is essential for the early apoptotic wave of germinal cells and for sperm quality control during spermatogenesis

Ubiquitination is required throughout all developmental stages of mammalian spermatogenesis. Ubiquitin C-terminal hydrolase (UCH) L1 is thought to associate with monoubiquitin to control ubiquitin levels. Previously, we found that UCHL1-deficient testes of gad mice have reduced ubiquitin levels and are resistant to cryptorchid stress-related injury. Here, we analyzed the function of UCHL1 during the first round of spermatogenesis and during sperm maturation, both of which are known to require ubiquitin-mediated proteolysis. Testicular germ cells in the immature testes of gad mice were resistant to the early apoptotic wave that occurs during the first round of spermatogenesis. TUNEL staining and cell quantitation demonstrated decreased germ cell apoptosis and increased numbers of premeiotic germ cells in gad mice between Postnatal Days 7 and 14. Expression of the apoptotic proteins TRP53, Bax, and caspase-3 was also significantly lower in the immature testes of gad mice. In adult gad mice, cauda epididymidis weight, sperm number in the epididymis, and sperm motility were reduced. Moreover, the number of defective spermatozoa was significantly increased; however, complete infertility was not detected. These data indicate that UCHL1 is required for normal spermatogenesis and sperm quality control and demonstrate the importance of UCHL1-dependent apoptosis in spermatogonial cell and sperm maturation.

Overexpression of ubiquitin carboxyl-terminal hydrolase L1 arrests spermatogenesis in transgenic mice

Ubiquitin carboxyl-terminal hydrolase 1 (UCH-L1) can be detected in mouse testicular germ cells, mainly spermatogonia and somatic Sertoli cells, but its physiological role is unknown. We show that transgenic (Tg) mice overexpressing EF1alpha promoter-driven UCH-L1 in the testis are sterile due to a block during spermatogenesis at an early stage (pachytene) of meiosis. Interestingly, almost all spermatogonia and Sertoli cells expressing excess UCH-L1, but little PCNA (proliferating cell nuclear antigen), showed no morphological signs of apoptosis or TUNEL-positive staining. Rather, germ cell apoptosis was mainly detected in primary spermatocytes having weak or negative UCH-L1 expression but strong PCNA expression. These data suggest that overexpression of UCH-L1 affects spermatogenesis during meiosis and, in particular, induces apoptosis in primary spermatocytes. In addition to results of caspases-3 upregulation and Bcl-2 downregulation, excess UCH-L1 influenced the distribution of PCNA, suggesting a specific role for UCH-L1 in the processes of mitotic proliferation and differentiation of spermatogonial stem cells during spermatogenesis.

HERC5, a HECT E3 ubiquitin ligase tightly regulated in LPS activated endothelial cells

By differential screening we isolated genes upregulated in inflammatory cytokine-stimulated human skin microvascular endothelial cells. One of these cDNAs encoded RCC1 (regulator of chromosome condensation 1)-like repeats and a HECT (homologous to E6-AP C-terminus) domain, representing a member of the HERC (HECT and RCC1 domain protein) family of ubiquitin ligases. The mRNA level of this member, HERC5, is specifically upregulated in endothelial cells by the pro-inflammatory cytokines tumor necrosis factor α and interleukin 1β, and by lipopolysaccharide (LPS), but is hardly expressed in other cells of the vascular wall such as primary smooth muscle cells and fibroblasts. Regulation of HERC5 gene expression suggests a critical role for the transcription factor NF-κB. In contrast to mRNA expression HERC5 protein is subject of enhanced degradation upon LPS stimulation of endothelial cells. The time course of LPS-induced changes in HERC5 protein and mRNA levels suggests that the initial drop in HERC5 protein is balanced by increased protein synthesis due to upregulation of HERC5 mRNA. This leads to recovery of HERC5 protein levels within 12 hours of LPS stimulation and points at a tight control of HERC5 protein. To analyze functional activity of this putative member of the ubiquitin-conjugating pathway we performed in vitro assays with different ubiquitin-conjugating enzymes. We found that HERC5 possesses ubiquitin ligase activity and requires the presence of the ubiquitin-conjugating enzyme UbcH5a for its activity. These data show for the first time that a functionally active HECT ubiquitin ligase exhibits a tightly controlled cytosolic level under inflammatory conditions in endothelial cells.