Tsga10 encodes a 65-kilodalton protein that is processed to the 27-kilodalton fibrous sheath protein

A novel homozygous TSGA10 missense variant causes acephalic spermatozoa syndrome in a Pakistani family

BACKGROUND

Acephalic spermatozoa syndrome is a rare type of teratozoospermia causing male infertility due to detachment of the sperm head and flagellum, which precludes fertilization potential. Although loss-of-function variations in several genes, including TSGA10, have been associated with acephalic spermatozoa syndrome, the genetic cause of many cases remains unclear.

RESULTS

We recruited a Pakistani family with two infertile brothers who suffered from acephalic spermatozoa syndrome. Through whole-exome sequencing (WES) followed by Sanger sequencing, we identified a novel missense variant in TSGA10 (c.1112T > C, p. Leu371Pro), which recessively co-segregated with the acephalic spermatozoa syndrome within this family. Ultrastructural analyses of spermatozoa from the patient revealed that 98% of flagellar cross-sections displayed abnormal axonemal ultrastructure, in addition to the head-flagellum detachment. Real-time quantitative PCR analysis revealed almost no detectable TSAG10 mRNA and western blot analysis also failed to detect TSAG10 protein in patient's sperm samples while TSGA10 expression was clearly detected in control samples. Consistently, immunofluorescence analysis demonstrated the presence of TSGA10 signal in the midpiece of sperm from the control but a complete absence of TSGA10 signal in sperm from the patient.

CONCLUSION

Altogether, our study identifies a novel TSGA10 pathogenic variant as a cause of acephalic spermatozoa syndrome in this family and provides information regarding the clinical manifestations associated with TSGA10 variants in human.

Gonadal transcriptomes reveal sex-biased expression genes associated with sex determination and differentiation in red-tail catfish (Hemibagrus wyckioides)

BACKGROUND

Red-tail catfish (Hemibagrus wyckioides) is an important commercially farmed catfish in southern China. Males of red-tail catfish grow faster than females, suggesting that all-male catfish will produce more significant economic benefits in aquaculture practice. However, little research has been reported on sex determination and gonadal development in red-tail catfish.

RESULTS

In this study, we performed the first transcriptomic analysis of male and female gonads at four developmental stages at 10, 18, 30, and 48 days post hatching (dph) using RNA-seq technology. A total of 23,588 genes were screened in 24 sequenced samples, of which 28, 213, 636, and 1381 differentially expressed genes (DEGs) were detected at four developmental stages, respectively. Seven candidate genes of sex determination and differentiation were further identified. Real-time quantitative PCR (RT-qPCR) further confirmed that anti-Mullerian hormone (amh), growth differentiation factor 6a (gdf6a), testis-specific gene antigen 10 (tsga10), and cytochrome P450 family 17 subfamily A (cyp17a) were highly expressed mainly in the male, while cytochrome P450 family 19 subfamily A polypeptide 1b (cyp19a1b), forkhead box L2 (foxl2), and hydroxysteroid 17-beta dehydrogenase 1 (hsd17b1) were highly expressed in the female. The KEGG pathway enrichment data showed that these identified DEGs were mainly involved in steroid hormone biosynthesis and TGF-β signaling pathways.

CONCLUSIONS

Based on RNA-seq data of gonads at the early developmental stages, seven DEGs shared by the four developmental stages were identified, among which amh and gdf6a may be the male-biased expression genes, while foxl2, cyp19a1b and hsd17b1 may be the female-biased expression genes in red-tail catfish. Our study will provide crucial genetic information for the research on sex control in red-tail catfish, as well as for exploring the evolutionary processes of sex determination mechanisms in fish.

Identification of TSGA10 and GGNBP2 splicing variants in 5' untranslated region with distinct expression profiles in brain tumor samples

Introduction

Brain tumors (BTs) are perceived as one of the most common malignancies among children. The specific regulation of each gene can play a critical role in cancer progression. The present study aimed to determine the transcripts of the TSGA10 and GGNBP2 genes, considering the alternative 5'UTR region, and investigating the expression of these different transcripts in BTs.

Material and methods

Public data on brain tumor microarray datasets in GEO were analyzed with R software to evaluate the expression levels of TSGA10 and GGNBP2 genes (the Pheatmap package in R was also used to plot DEGs in a heat map). In addition, to validate our in-silico data analysis, RT-PCR was performed to determine the splicing variants of TSGA10 and GGNBP2 genes in testis and brain tumor samples. The expression levels of splice variants of these genes were analyzed in 30 brain tumor samples and two testicular tissue samples as a positive control.

Results

In silico results show that the differential expression levels of TSGA10 and GGNBP2 were significant in the GEO datasets of BTs compared to normal samples (with adjusted p-value<0.05 and log fold change > 1). This study's experimental results showed that the TSGA10 gene produces four different transcripts with two distinct promoter regions and splicing exon 4. The relative mRNA expression of transcripts without exon 4 was higher than transcripts with exon 4 in BT samples (p-value<001). In GGNBP2, exon 2 in the 5'UTR region and exon 6 in the coding sequence were spliced. The expression analysis results showed that the relative mRNA expression of transcript variants without exon 2 was higher than other transcript variants with exon 2 in BT samples (p-value<001).

Conclusion

The decreased expression levels of transcripts with longer 5'UTR in BT samples than in testicular or low-grade brain tumor samples may decrease their translation efficiency. Therefore, decreased amounts of TSGA10 and GGNBP2 as potential tumor suppressor proteins, especially in high-grade brain tumors, may cause cancer development by angiogenesis and metastasis.

Identification of genes related to sexual differentiation and sterility in embryonic gonads of Mule ducks by transcriptome analysis

The key genes of avian gonadal development are of great significance for sex determination. Transcriptome sequencing analysis of Mule duck gonad as potential sterile model is expected to screen candidate genes related to avian gonad development. In this study, the embryonic gonadal tissues of Mule ducks, Jinding ducks, and Muscovy ducks were collected and identified. Six sample groups including female Mule duck (A), male Mule duck (B), female Jinding duck (C), male Jinding duck (D), female Muscovy duck (E), and male Muscovy duck (F) were subjected to RNA sequencing analysis. A total of 9,471 differential genes (DEGs) and 691 protein-protein interaction pairs were obtained. Totally, 12 genes (Dmrt1, Amh, Sox9, Tex14, Trim71, Slc26a8, Spam1, Tdrp, Tsga10, Boc, Cxcl14, and Hsd17b3) were identified to be specifically related to duck testicular development, and 11 genes (Hsd17b1, Cyp19a1, Cyp17a1, Hhipl2, Tdrp, Uts2r, Cdon, Axin2, Nxph1, Brinp2, and Brinp3) were specifically related to duck ovarian development. Seven genes (Stra8, Dmc1, Terb1, Tex14, Tsga10, Spam1, and Plcd4) were screened to be specifically involved in the female sterility of Mule ducks; eight genes (Gtsf1, Nalcn, Tat, Slc26a8, Kmo, Plcd4, Aldh4a1, and Hgd) were specifically involved in male sterility; and five genes (Terb1, Stra8, Tex14 Tsga10 and Spam1) were involved in both female and male sterility. This study provides an insight into the differential development between male and female gonads of ducks and the sterility mechanism of Mule ducks through function, pathway, and protein interaction analyses. Our findings provide theoretical basis for the further research on sex determination and differentiation of birds and the sterility of Mule ducks.

Application of CRISPR/Cas Technology in Spermatogenesis Research and Male Infertility Treatment

As the basis of animal reproductive activity, normal spermatogenesis directly determines the efficiency of livestock production. An in-depth understanding of spermatogenesis will greatly facilitate animal breeding efforts and male infertility treatment. With the continuous development and application of gene editing technologies, they have become valuable tools to study the mechanism of spermatogenesis. Gene editing technologies have provided us with a better understanding of the functions and potential mechanisms of action of factors that regulate spermatogenesis. This review summarizes the applications of gene editing technologies, especially CRISPR/Cas9, in deepening our understanding of the function of spermatogenesis-related genes and disease treatment. The problems of gene editing technologies in the field of spermatogenesis research are also discussed.

Pathogenesis of acephalic spermatozoa syndrome caused by splicing mutation and de novo deletion in TSGA10

PURPOSE

To identify the genetic causes for acephalic spermatozoa syndrome.

METHODS

Whole-exome sequencing was performed on the proband from a non-consanguineous to identify pathogenic mutations for acephalic spermatozoa syndrome. Quantitative real-time polymerase chain reaction and whole genome sequencing were subjected to detect deletion. The functional effect of the identified splicing mutation was investigated by minigene assay. Western blot and immunofluorescence were performed to detect the expression level and localization of mutant TSGA10 protein.

RESULTS

Here, we identified a novel heterozygous splicing mutation in TSGA10 (NM_025244: c.1108-1G > T), while we confirmed that there was a de novo large deletion in the proband. The splicing mutation led to the skipping of the exon15 of TSGA10, which resulted in a truncated protein (p. A370Efs*293). Therefore, we speculated that the splicing mutation might affect transcription and translation without the dosage compensation of a normal allele, which possesses a large deletion including intact TSGA10. Western blot and immunofluorescence demonstrated that the very low expression level of truncated TSGA10 protein led the proband to present the acephalic spermatozoa phenotype.

CONCLUSION

Our finding expands the spectrum of pathogenic TSGA10 mutations that are responsible for ASS and male infertility. It is also important to remind us of paying attention to the compound heterozygous deletion in patients from non-consanguineous families, so that we can provide more precise genetic counseling for patients.

Multifaceted roles of centrosomes in development, health, and disease

The centrosome is a membrane-less organelle consisting of a pair of barrel-shaped centrioles and pericentriolar material and functions as the major microtubule-organizing center and signaling hub in animal cells. The past decades have witnessed the functional complexity and importance of centrosomes in various cellular processes such as cell shaping, division, and migration. In addition, centrosome abnormalities are linked to a wide range of human diseases and pathological states, such as cancer, reproductive disorder, brain disease, and ciliopathies. Herein, we discuss various functions of centrosomes in development and health, with an emphasis on their roles in germ cells, stem cells, and immune responses. We also discuss how centrosome dysfunctions are involved in diseases. A better understanding of the mechanisms regulating centrosome functions may lead the way to potential therapeutic targeting of this organelle in disease treatment.

Genetic basis of acephalic spermatozoa syndrome, and intracytoplasmic sperm injection outcomes in infertile men: a systematic scoping review

PURPOSE

Acephalic spermatozoa syndrome (ASS) is known as a severe type of teratozoospermia, defined as semen composed of mostly headless spermatozoa that affect male fertility. In this regard, this systematic review aimed to discuss gene variants associated with acephalic spermatozoa phenotype as well as the clinical outcomes of intracytoplasmic sperm injection (ICSI) treatment for the acephalic spermatozoa-associated male infertility.

METHODS

A systematic search was performed on PubMed, Embase, Scopus, and Ovid databases until May 17, 2020. This systematic scoping review was reported in terms of the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) statement.

RESULTS

Twenty articles were included in this systematic review. Whole-exome and Sanger sequencing have helped in the identification of variants in SUN5, PMFBP1, BRDT, TSGA10, DNAH6, HOOK1, and CEP112 genes as possible causes of this phenotype in humans. The results of the ICSI are conflicting due to both positive and negative reports of ICSI outcomes.

CONCLUSION

ASS has a genetic origin, and several genetic alterations related to the pathogenesis of this anomaly have been recently identified. Notably, only SUN5 and PMFBP1 mutations are well-known to be implicated in ASS. Accordingly, more functional studies are needed to confirm the pathogenicity of other variants. ICSI could provide a promising treatment for acephalic spermatozoa-associated male infertility. Besides the importance of sperm head-tail junction integrity, some other factors, whether within the sperm cell or female factors, may be involved in the ICSI outcome.

Tsga10 is essential for arrangement of mitochondrial sheath and male fertility in mice

BACKGROUND

Male infertility is a major issue in human reproduction health, yet known genetic factors are only responsible for a small fraction of cases. TSGA10 is a testis-specific protein that is highly conserved among different species. A previous study has reported a homozygous mutation in TSGA10 in a male infertile patient; however, function analysis of Tsga10 genes in knockout mice has not yet been undertaken.

OBJECTIVES

The aim of the present work was to analyse the function of TSGA10 protein in the spermatogenesis of Tsga10+/- mice.

MATERIALS AND METHODS

Tsga10+/- mice were generated by CRISPR/Cas9 technology, in vitro fertilization (IVF), western blot, co-immunoprecipitation and other methods were used to the function analysis.

RESULTS

Heterozygous Tsga10 male mice created by CRISPR/Cas9 were infertile and presented significantly reduced sperm motility because of disordered mitochondrial sheath formation. Furthermore, TSGA10 can interact with GRP78 and NSUN2, which are associated with peri-implantation lethality and the gonadotropin-releasing hormone (GnRH) network.

DISCUSSION AND CONCLUSION

We demonstrate that deficiency of Tsga10 gene can lead to male infertility in mice. TSGA10 is involved in the correct arrangement of mitochondrial sheath in spermatozoa. Future studies on TSGA10 include an in-depth exploration of the underlying mechanisms of TSGA10 in spermatogenesis, early embryonic development and GnRH network.

The sperm centrioles

Centrioles are eukaryotic subcellular structures that produce and regulate massive cytoskeleton superstructures. They form centrosomes and cilia, regulate new centriole formation, anchor cilia to the cell, and regulate cilia function. These basic centriolar functions are executed in sperm cells during their amplification from spermatogonial stem cells during their differentiation to spermatozoa, and finally, after fertilization, when the sperm fuses with the egg. However, sperm centrioles exhibit many unique characteristics not commonly observed in other cell types, including structural remodeling, centriole-flagellum transition zone migration, and cell membrane association during meiosis. Here, we discuss five roles of sperm centrioles: orchestrating early spermatogenic cell divisions, forming the spermatozoon flagella, linking the spermatozoon head and tail, controlling sperm tail beating, and organizing the cytoskeleton of the zygote post-fertilization. We present the historic discovery of the centriole as a sperm factor that initiates embryogenesis, and recent genetic studies in humans and other mammals evaluating the current evidence for the five functions of sperm centrioles. We also examine information connecting the various sperm centriole functions to distinct clinical phenotypes. The emerging picture is that centrioles are essential sperm components with remarkable functional diversity and specialization that will require extensive and in-depth future studies.

Loss-of-function mutation in TSGA10 causes acephalic spermatozoa phenotype in human

Background

Acephalic spermatozoa is an extremely rare type of teratozoospermia that is associated with male infertility. Several genes have been reported to be relevant to acephalic spermatozoa. Thus, more genetic pathogenesis needs to be explored.

Methods

Whole‐exome sequencing was performed in a patient with acephalic spermatozoa. Then Sanger sequencing was used for validation in the patient and his family. The patient's spermatozoa sample was observed by papanicolaou staining and transmission electron microscopy. Western blot and immunofluorescence were performed to detect the level and localization of related proteins.

Results

A novel homozygous frameshift insertion mutation c.545dupT;p.Ala183Serfs*10 in exon 8 of TSGA10 (NM_001349012.1) was identified. Our results showed misarranged mitochondrial sheath and abnormal flagellum in the patient's spermatozoa. TSGA10 failed to be detected in the patient's spermatozoa. However, the expression of SUN5 and PMFBP1 remained unaffected.

Conclusion

These results suggest that the novel homozygous frameshift insertion mutation of TSGA10 is a cause of acephalic spermatozoa.

Gene Polymorphisms in Boar Spermatozoa and Their Associations with Post-Thaw Semen Quality

Genetic markers have been used to assess the freezability of semen. With the advancement in molecular genetic techniques, it is possible to assess the relationships between sperm functions and gene polymorphisms. In this study, variant calling analysis of RNA-Seq datasets was used to identify single nucleotide polymorphisms (SNPs) in boar spermatozoa and to explore the associations between SNPs and post-thaw semen quality. Assessment of post-thaw sperm quality characteristics showed that 21 boars were considered as having good semen freezability (GSF), while 19 boars were classified as having poor semen freezability (PSF). Variant calling demonstrated that most of the polymorphisms (67%) detected in boar spermatozoa were at the 3’-untranslated regions (3’-UTRs). Analysis of SNP abundance in various functional gene categories showed that gene ontology (GO) terms were related to response to stress, motility, metabolism, reproduction, and embryo development. Genomic DNA was isolated from sperm samples of 40 boars. Forty SNPs were selected and genotyped, and several SNPs were significantly associated with motility and membrane integrity of frozen-thawed (FT) spermatozoa. Polymorphism in SCLT1 gene was associated with significantly higher motility and plasma membrane integrity of FT spermatozoa from boars of the GSF group compared with those of the PSF group. Likewise, polymorphisms in MAP3K20, MS4A2, and ROBO1 genes were significantly associated with reduced cryo-induced lipid peroxidation and DNA damage of FT spermatozoa from boars of the GSF group. Candidate genes with significant SNP associations, including APPL1, PLBD1, FBXO16, EML5, RAB3C, OXSR1,PRICKLE1, and MAP3K20 genes, represent potential markers for post-thaw semen quality, and they might be relevant for future improvement in the selection procedure of boars for cryopreservation. The findings of this study provide evidence indicating that polymorphisms in genes expressed in spermatozoa could be considered as factors associated with post-thaw semen quality.

TSGA10 overexpression inhibits angiogenesis of HUVECs: A HIF-2α biased perspective

Testis-specific gene antigen 10 (TSGA10) is a protein overexpressed in most cancers; except for some certain types where its expression is reduced. TSGA10 overexpression in HeLa cells has been shown to disrupt hypoxia inducible factor-1α (HIF-1α) axis and exert potent inhibitory effects. Since HIF-1α is structurally and biochemically similar to HIF-2α, TSGA10 is expected to bind HIF-2α and inhibit its function as well. This study elucidated that increased expression of TSGA10 in manipulated human umbilical vein endothelial cells (HUVECs) decreased the proliferation and migration of these cells as affirmed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and wound healing tests, respectively. It also inhibited in vitro angiogenesis of these cells in 3D collagen-cytodex model. Expression levels of genes controlled by HIF-2α including autocrine vascular endothelial growth factor (VEGF) were also assessed using real-time PCR. Our bioinformatic analysis also showed that TSGA10 could bind HIF-2α. Moreover, flow cytometry results indicated a cell cycle arrest in G2/M. Therefore, this study showed that overexpression of TSGA10, as a tumor suppressor gene, in endothelial cells resulted in decreased proliferation, migration and therefore, angiogenic activity of HUVECs. Since angiogenesis is vital for tumor development and metastasis, our findings could be of clinical significance in cancer therapy.

Functional expression and impact of testis-specific gene antigen 10 in breast cancer: a combined in vitro and in silico analysis

Introduction: Testis-specific gene antigen 10 (TSGA10) is a less-known gene, which is involved in the vague biological paths of different cancers. Here, we investigated the TSGA10 expression using different concentrations of glucose under hypoxia and also its interaction with the hypoxia-inducible factor 1 (HIF-1). Methods: The breast cancer MDA-MB-231 and MCF-7 cells were cultured with different concentrations of glucose (5.5, 11.0 and 25.0 mM) under normoxia/hypoxia for 24, 48, and 72 hours and examined for the HIF-1α expression and cell migration by Western blotting and scratch assays. The qPCR was employed to analyze the expression of TSGA10. Three-dimensional (3D) structure and the energy minimization of the interacting domain of TSGA10 were performed by MODELLER v9.17 and Swiss-PDB viewer v4.1.0/UCSF Chimera v1.11. The UCSF Chimera v1.13.1 and Hex 6.0 were used for the molecular docking simulation. The Cytoscape v3.7.1 and STRING v11.0 were used for protein-protein interaction (PPI) network analysis. The HIF-1a related hypoxia pathways were obtained from BioModels database and reconstructed in CellDesigner v4.4.2. Results: The increased expression of TSGA10 was found to be significantly associated with the reduced metastasis in the MDA-MB-231 cells, while an inverse relationship was seen between the TSGA10 mRNA level and cellular migration but not in the MCF-7 cells. The C-terminal domain of TSGA10 interacted with HIF-1α with high affinity, resulting in PPI network with 10 key nodes (HIF-1α, VEGFA, HSP90AA1, AKT1, ARNT, TP53, TSGA10, VHL, JUN, and EGFR). Conclusions: Collectively, TSGA10 functional expression alters under the hyper-/hypo-glycemia and hypoxia, which indicates its importance as a candidate bio-target for the cancer therapy.

Contribution and prognostic value of TSGA10 gene expression in patients with acute myeloid leukemia (AML)

BACKGROUND

Different studies have investigated TSGA10 expression in various cancerous tissues but, so far no study has been conducted on newly diagnosed (ND) AML patients. The association of TSGA10 gene expression with hypoxia inducible factor (HIF) and angiogenic factors has remained to be fully elucidated and is still a controversial issue. The present study was designed to investigate this association in patients newly diagnosed with AML.

METHODS

We evaluated TSGA10, HIF-1α and VEGF mRNA levels in ND AML patients and healthy subjects using real-time PCR technique. Data were analyzed via comparative Livak method.

RESULTS

Based on the results of this study, TSGA10 gene expression was decreased in 28 out of 30 (93.3%) samples while VEGF and HIF-1α expression levels were increased in all ND AML patients compared to healthy controls. Diagnostic evaluation was performed by receiver operating characteristic (ROC) curve and area under the curve (AUC) calculation. Respectively, using cut-off relative quantification of 1.604, 0.0329, and 0.0042, the sensitivity values of TSGA10, VEGF, and HIF-1α gene expression were 86.7%, 90%, and 100%. Also, specificity values were 100%, 100% and 100%, respectively. TSGA10 expression was shown to be reduced in ND AML patients compared with healthy subjects and we found a negative correlation between TSGA10 and VEGF expression.

CONCLUSIONS

Since TSGA10 interacts with HIF-1 and affects its transcriptional activity, in ND AML patients with decreased TSGA10 expression, VEGF expression was high suggesting a TSGA10 mediated regulation of HIF-1 target genes. Altogether, the current study showed that TSGA10 could be considered as a tumor suppressor in AML patients.

Obtaining and characterization of anti-testis monoclonal antibodies: Invaluable tools toward the identification of testis antigens involved in fertilization

BACKGROUND

Generation and utilization of the specific monoclonal antibodies against testis antigens is reported to identify the antigens that are important in reproductive field.

OBJECTIVE

Current study aimed to introduce a hybridoma that producing a specific anti-testis monoclonal antibody to identify the testis antigens that can be important in the reproduction field.

METHODS

To make hybridoma against testis antigens, mice were immunized with testis cell lysate. After cell fusion, resulted hybridomas were screened by indirect ELISA, then cloned by limiting dilution and finally the produced monoclonal antibody were characterized by some of the molecular laboratory techniques such as immunohistochemistry, immunocytochemistry and western blot.

RESULTS

By using hybridoma technique, cell fusion was performed and ten (8A11, 8D6, 8D7, 9F6, 9G11, 10C3, 10B3, 10B2, 10C2 and 10H7) antibodies specific to the testis antigens were produced finally. Among the produced antibodies, 10C3 was found to cross-react with testis, but not detected in other tissues. mAb 10C3 recognized the sperm and testis antigens, specifically the intertestitial tissue of testis, spermatogonia, primary and secondary spermatocyte antigens, so they were most likely the target of generated mAb. Also our mAb could totally detect the mouse sperm antigens and the specific antigens of head and tail of human sperm. In western blotting analysis, mAb 10C3 could recognize the specific protein bands of sperm and testis extracts. Also in this study the testis specific genes that were target of generated mAb, were selected according to the mouse EST profile available at UniGene part of NCBI.

CONCLUSIONS

So this stable anti-testis mAb has a potential for laboratory researches and also for diagnostic procedures in fertilization. Thus it could be exploited as a suitable tool for target-specific diagnosis and research in several diseases.

Identification of oxidatively modified proteins due to cryopreservation of carp semen

During semen cryopreservation, spermatozoa are exposed to physical and chemical stressors that result in their functional and structural damage. Growing evidence suggests that most cryoinjuries result from oxidative stress accompanying sperm cryopreservation. Elevated amounts of reactive oxygen species (ROS) generated during cryopreservation can react with sperm macromolecules, including proteins. The goal of this study was to investigate the oxidative modifications (measured as carbonylation level changes) of carp spermatozoa proteins triggered by the cryopreservation process. Flow cytometry and computer-assisted sperm analysis were used to evaluate changes in viability, ROS level, and motility of spermatozoa. The spermatozoa proteins that were specifically carbonylated were identified and quantified by Western blotting, in conjunction with 2-dimensional electrophoresis (2D-oxyblot) and matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry. Cryopreservation decreased spermatozoa motility (P < 0.01) and viability (P < 0.0001) and significantly increased (P < 0.0001) the number of ROS-positive cells. We identified 25 protein spots, corresponding to 19 proteins, with increases (P < 0.05) in carbonylation level due to freezing/thawing. The identified proteins are involved in motility, metabolism, calcium-ion binding, signal transduction, protein folding, and intracellular transport. The results suggest that carbonylation of flagellar proteins can result in motility disorders and may contribute to the reduced percentage of motile spermatozoa and disturbances in movement trajectory after sperm cryopreservation. Moreover, cryopreservation may contribute to impaired cellular respiration, ATP regeneration, disturbances of Ca2+ turnover, unfolding of cytoplasmic or histone proteins, disturbances of cell signaling and intracellular transport, and reduced membrane stability. Our results contribute to the knowledge concerning cryoinjury and to further development of a modified cryopreservation procedure aimed at minimizing oxidative damage of carp sperm proteins.

TSGA10 is a novel candidate gene associated with acephalic spermatozoa

Acephalic spermatozoa is a rare teratozoospermia associated with male infertility. However, the pathogenesis of this disorder remains unclear. Here, we report a 27 years old infertile male from a consanguineous family, who presented with 99% headless sperm in his ejaculate. Electron microscopic and immunofluorescence analysis suggested breakage at the midpiece of the patient's sperm cells. Subsequent whole-exome sequencing analysis identified a homozygous deletion within TSGA10 (c.211delG; p.A71Hfs*12), which resulted in the production of truncated TSGA10 protein. TSGA10 is a testis-specific protein that localized to the midpiece in the spermatozoa of a normal control; however, immunostaining failed to detect TSGA10 protein in the patient's sperm. Western blot analysis also showed complete absence of TSGA10 protein in the patient. One cycle of in vitro fertilization-assisted reproduction was conducted, but pregnancy was not achieved after embryo transfer, possibly due to poor embryo quality. Therefore, we speculate that the presence of rare sequence variants within TSGA10 may be associated with acephalic spermatozoa in humans.

Tsga10 expression correlates with sperm profiles in the adult formalin-exposed mice

Testis-specific gene antigen10 (Tsga10), as a cytoskeletal protein in the sperm tail, impacts the sperm motility. This study investigates the correlation between sperm profile alterations and Tsga10 gene expression in adult mice exposed to formaldehyde (FA) and then treated with antioxidant effect of manganese (Mn²⁺ ). In this regard, we examined 35 NMRI adult male mice (6-8 weeks age) in 4 groups of control, sham, FA-exposed and FA+Mn²⁺ . The mice in FA+Mn²⁺ group were exposed to FA (10 mg kg^-1 twice a day) for 2 weeks and treated with daily Mn²⁺ administration (5 mg kg^-1 ) in the second week prior to sacrificing the mice for testis dissection. The right testis was dissected in each group and subjected to RNA extraction and cDNA syntheses for gene expression analysis by real-time PCR. The findings revealed that FA decreased sperm parameters and Tsga10 expression (52.6 ± 24.37%). However, the injected powerful manganese antioxidant improved sperm profile through overexpression of Tsga10 (121.6 ± 27.13%) under FA-induced stressful condition which proves the correlation between sperm profile and Tsga10 expression (P ≤ 0.05). This study also shows that Tsga10 expression protects sperm dysfunction in FA+Mn²⁺ group and resulting in better preservation of spermatozoa and improvement of male fertility.

Cancer-testis genes as candidates for immunotherapy in breast cancer

Cancer-testis (CT) antigens are tumor-associated antigens attracting immunologists for their possible application in the immunotherapy of cancer. Several clinical trials have assessed their therapeutic potentials in cancer patients. Breast cancers, especially triple-negative cancers are among those with significant expression of CT genes. Identification of CT genes with high expression in cancer patients is the prerequisite for any immunotherapeutic approach. CT genes have gained attention not only for immunotherapy of cancer patients, but also for immunoprevention in high-risk individuals. Many CT genes have proved to be immunogenic in breast cancer patients suggesting the basis for the development of polyvalent vaccines.

Effects and interactions of MiR-577 and TSGA10 in regulating esophageal squamous cell carcinoma

Testis specific 10 (TSGA10) was originally identified as a testis-specific protein and tumor-associated antigen in a number of cancer types. In this study, we found that down-regulation of TSGA10 was associated with increased malignancy and clinical features of esophageal squamous cell carcinomas (ESCCs). Moreover, increased expression of TSGA10 inhibited, while its knockdown promoted, tumor formation in vivo in nude mice. At the 3'UTR of the TSGA10 gene we identified two binding sites for microRNA-577 (miR-577). Further investigation demonstrated that expression levels of miR-577 and TSGA10 were negatively correlated to each other in ESCC cell lines and tumor samples. Moreover, manipulation of miR-577 and TSGA10 expression confirmed that miR-577 can regulate TSGA10 and in turn affect cell proliferation in vitro. Additionally, with flow cytometry and manipulation of the mir-577/TSGA10 axis, it was found that mir-577/TSGA10 axis influenced the growth of ESCC through regulating the G1-S phase transition. We also obtained evidence to establish that mir-577/TSGA10 axis activation was always accompanied by inactivation of the p53 pathway or the Rb pathway or both, thus, the latter two pathways are obligatory for progression of ESCCs with mir-577/TSGA10 axis activation. In addition, we found that such an interactive pathway in regulating cancer cell proliferation was restricted to a few cancer types including ESCC, but not uniformly applicable to other cancer types. This newly discovered regulatory mechanism provides a new dimension for ESCC diagnosis and therapy.

Over-Expression of the Testis-Specific GeneTSGA10in Cancers and Its Immunogenicity

The TSGA10 gene was originally isolated in normal testis by differential mRNA display. TSGA10 is located on chromosome 2q11.2 and consists of 19 exons extending over 3 kb. TSGA10 mRNA expression was investigated in normal and malignant tissues using quantitative real-time RT-PCR. It was predominantly expressed in the testis in adult normal tissues. In malignant tissues, TSGA10 was over-expressed in 4 of 20 hepatocellular carcinomas (HCC), 1 of 20 colon cancers, 7 of 20 ovarian cancers, 3 of 20 prostate cancers, 1 of 21 malignant melanomas, and 8 of 21 bladder cancers. Serological analysis revealed that 3 out of 346 patients with various types of cancer possessed antibody against recombinant TSGA10 protein. They included 2 patients with hepatocellular carcinoma and a patient with malignant melanoma.

BLD10/CEP135 is a microtubule-associated protein that controls the formation of the flagellum central microtubule pair

Cilia and flagella are involved in a variety of processes and human diseases, including ciliopathies and sterility. Their motility is often controlled by a central microtubule (MT) pair localized within the ciliary MT-based skeleton, the axoneme. We characterized the formation of the motility apparatus in detail in Drosophila spermatogenesis. We show that assembly of the central MT pair starts prior to the meiotic divisions, with nucleation of a singlet MT within the basal body of a small cilium, and that the second MT of the pair only assembles much later, upon flagella formation. BLD10/CEP135, a conserved player in centriole and flagella biogenesis, can bind and stabilize MTs and is required for the early steps of central MT pair formation. This work describes a genetically tractable system to study motile cilia formation and provides an explanation for BLD10/CEP135's role in assembling highly stable MT-based structures, such as motile axonemes and centrioles.

Expression of cancer-testis genes in brain tumors: implications for cancer immunotherapy

Cancer-testis (CT) genes have a restricted expression in normal tissues except testis and a wide range of tumor types. Testis is an immune-privileged site as a result of a blood barrier and lack of HLA class I expression on the surface of germ cells. Hence, if testis-specific genes are expressed in other tissues, they can be immunogenic. Expression of some CT genes in a high percentage of brain tumors makes them potential targets for immunotherapy. In addition, expression of CT genes in cancer stem cells may provide special targets for treatment of cancer recurrences and metastasis. The presence of antibodies against different CT genes in patients with advanced tumors has raised the possibility of polyvalent antitumor vaccine application.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 3: developmental changes in spermatid flagellum and cytoplasmic droplet and interaction of sperm with the zona pellucida and egg plasma membrane

Spermiogenesis constitutes the steps involved in the metamorphosis of spermatids into spermatozoa. It involves modification of several organelles in addition to the formation of several structures including the flagellum and cytoplasmic droplet. The flagellum is composed of a neck region and middle, principal, and end pieces. The axoneme composed of nine outer microtubular doublets circularly arranged to form a cylinder around a central pair of microtubules is present throughout the flagellum. The middle and principal pieces each contain specific components such as the mitochondrial sheath and fibrous sheath, respectively, while outer dense fibers are common to both. A plethora of proteins are constituents of each of these structures, with each playing key roles in functions related to the fertility of spermatozoa. At the end of spermiogenesis, a portion of spermatid cytoplasm remains associated with the released spermatozoa, referred to as the cytoplasmic droplet. The latter has as its main feature Golgi saccules, which appear to modify the plasma membrane of spermatozoa as they move down the epididymal duct and hence may be partly involved in male gamete maturation. The end product of spermatogenesis is highly streamlined and motile spermatozoa having a condensed nucleus equipped with an acrosome. Spermatozoa move through the female reproductive tract and eventually penetrate the zona pellucida and bind to the egg plasma membrane. Many proteins have been implicated in the process of fertilization as well as a plethora of proteins involved in the development of spermatids and sperm, and these are high lighted in this review.

Stepwise evolution of the centriole-assembly pathway

The centriole and basal body (CBB) structure nucleates cilia and flagella, and is an essential component of the centrosome, underlying eukaryotic microtubule-based motility, cell division and polarity. In recent years, components of the CBB-assembly machinery have been identified, but little is known about their regulation and evolution. Given the diversity of cellular contexts encountered in eukaryotes, but the remarkable conservation of CBB morphology, we asked whether general mechanistic principles could explain CBB assembly. We analysed the distribution of each component of the human CBB-assembly machinery across eukaryotes as a strategy to generate testable hypotheses. We found an evolutionarily cohesive and ancestral module, which we term UNIMOD and is defined by three components (SAS6, SAS4/CPAP and BLD10/CEP135), that correlates with the occurrence of CBBs. Unexpectedly, other players (SAK/PLK4, SPD2/CEP192 and CP110) emerged in a taxon-specific manner. We report that gene duplication plays an important role in the evolution of CBB components and show that, in the case of BLD10/CEP135, this is a source of tissue specificity in CBB and flagella biogenesis. Moreover, we observe extreme protein divergence amongst CBB components and show experimentally that there is loss of cross-species complementation among SAK/PLK4 family members, suggesting species-specific adaptations in CBB assembly. We propose that the UNIMOD theory explains the conservation of CBB architecture and that taxon- and tissue-specific molecular innovations, gained through emergence, duplication and divergence, play important roles in coordinating CBB biogenesis and function in different cellular contexts.

Effect of long-term administration of zinc after scrotal heating on mice spermatozoa and subsequent offspring quality

This study was set to investigate whether the adverse effects of heat on spermatozoa and subsequent foetuses could be prevented by long-term zinc administration. The scrotums of animals were immersed in water at either 43 degrees C (heat group) or 23 degrees C (control group). Half of the heat and control mice were given 10 mg kg(-1) zinc every other day for 60 days and the others received sterile saline instead of zinc. Heat stress significantly reduced sperm motility, concentration, hypoosmotic swelling-water test (HOS-WT) positive and chromomycin A(3) (CMA(3)) negative spermatozoa at the first 15 days, and the greatest decrease occurred at 30 days (P < 0.05). Sperm motility, concentration and HOS-WT positive spermatozoa were also reduced initially in the zinc administered group, but we did not observe any further decrease in the above mentioned parameters on day 30 (P < 0.05). The weight of foetuses obtained from the females mated with paternal heat treatment males was significantly lower than that of the control group (P < 0.05) and long-term zinc therapy caused a partial recovery (P > 0.05). This study demonstrates that the adverse effects of hyperthermia on semen parameters may be prevented by zinc therapy. Likewise, long-term administration of zinc could improve quality of litter obtained from the females mated with scrotal heat treatment males.

TSGA10 is Specifically Expressed in Astrocyte and Over-expressed in Brain Tumors

In this study TSGA10 has been demonstrated as a testis-specific human gene that encodes a protein localized in sperm-tail and conserved in ciliary structure. Further investigations showed TSGA10 signalling and expression during embryogenesis, brain development and some malignancies including brain tumors. Given the role of this protein in neuronal development and in certain tumors, it could potentially serve as a diagnostic marker and therapeutic target in brain tumors. Therefore, using immunohistochemistry, we evaluated the localization of TSGA10 in different regions of brain, and its pattern/level of expression in tissue microarray (Cybrdi) containing human brain tumors and normal brain. In rat specimens, TSGA10 was mainly expressed in subventricular zone, hippocampus and granular layer of cerebellum of the brain. The antibody also stained the diverse and different types of human brain cancers. The TSGA10 was strongly over-expressed in glioblastoma and astrocytoma when compared to normal human brain. The expression of TSGA10 was also confirmed in astrocyte derived from a human astroctyoma cell line by immunocytochemistry. This study indicates that TSGA10 can be used as an immunohistochemical marker for human neuroglia and astrocyte cells and is over-expressed in brain tumors.

Identification of novel p53 target genes by cDNA AFLP in glioblastoma cells

The p53 plays critical role in cellular functions such as cell cycle arrest and apoptosis. We overexpressed wild-type p53 (wt-p53) in U87 glioblastoma cells via recombinant adenovirus Ad-GFP-P53 which encodes p53 and green fluorescent protein. The transcript profiles were investigated using cDNA amplified fragment length polymorphism approach. Semi-quantitative RT-PCR and DNA sequencing results for the selected genes showed that Cathepsin B and cell cycle associated protein-1 or Caprin-I, genes were suppressed whereas Annexin-II gene overexpressed in response to the overexpression of wt-p53 gene. Our results suggest that these genes could be important mediators of p53-dependent tumor growth suppression in glioblastoma.

Protein Domains Govern the Intracellular Distribution of Mouse Sperm AKAP41

A-kinase anchor proteins (AKAPs) spatially restrict cAMP-dependent protein kinase by tethering it to various cellular structures. In the polarized sperm cell, various compartmentalized functions, such as motility generated by the flagellum, are modulated by cAMP-dependent protein kinase. This important regulatory enzyme is associated with AKAP4, the principal component of the fibrous sheath; AKAP4 is synthesized as a precursor, pro-AKAP4, which is cleaved into mature AKAP4 during fibrous sheath assembly. To define the domains responsible for the intracellular distribution and assembly of AKAP4 into a macromolecular complex, various AKAP4-green fluorescent protein (GFP) constructs were introduced into somatic cell lines. The presence of the pro domain, either alone or as part of pro-AKAP4, resulted in a diffuse cytoplasmic localization of the GFP fusion protein, suggesting that, the pro domain keeps the AKAP4 precursor unassembled in vivo until it is transported to the developing tail structure and incorporated into the fibrous sheath. When the mature AKAP4-GFP fusion protein was expressed, it localized in a punctate cytoplasmic pattern. Two domains critical for this punctate localization, T2a and T2b, are homologous to the T2-tethering domain of rat AKAP5 that is important for binding to the actin cytoskeleton in transfected HEK293 cells. In contrast to AKAP5, the distribution of AKAP4 was dependent on the microtubular cytoskeleton. The interaction of AKAP4 with the microtubular network provides evidence that the longitudinal columns of the fibrous sheath, which contain AKAP4, may interact directly with the outer microtubular doublets of the sperm axoneme.

TSGA10 prevents nuclear localization of the hypoxia-inducible factor (HIF)-1alpha

The hypoxia-inducible factor (HIF)-1 is a transcriptional regulator of genes involved in oxygen homeostasis. We previously described testis-specific isoforms of HIF-1alpha (mHIF-1alphaI.1 and hHIF-1alphaTe). Using mHIF-1alpha exon I.1 knock-out mice we confirmed the specific expression of mHIF-1alphaI.1 in the sperm tail. A protein-protein interaction between HIF-1alpha and the testis specific gene antigen 10 (TSGA10) was identified by yeast two-hybrid screening. TSGA10 is expressed in testis but also in other organs and malignant tissues. Immunofluorescence analysis indicated that the C-terminal part of TSGA10 accumulates in the midpiece of spermatozoa, where it co-localizes with HIF-1alpha. HIF-1alpha nuclear localization and HIF-1 transcriptional activity were significantly affected by overexpressed TSGA10.

New fibrous sheath anomaly in spermatozoa of men with consanguinity

OBJECTIVE

The cause of the sperm motility impairment was investigated in infertile men.

DESIGN

Case report.

SETTING

University-based andrology laboratory.

PATIENTS

Two unrelated consanguineous patients.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The sperm flagella lengths were measured using quantitative analysis software and their ultrastructural anomalies were quantitatively recorded.

RESULT(S)

A total of 67.5% of the flagella were truncated, and 100% lacked the medium region of the ribs of the fibrous sheath.

CONCLUSION(S)

The data suggested a morphogenetic anomaly at the stage where rib precursors are formed during spermiogenesis. The consanguinity of these patients suggested a genetic origin for this newly discovered anomaly of the human sperm's fibrous sheath. The family tree appears to indicate an autosomal recessive inheritance.

Expression of Tsga10 sperm tail protein in embryogenesis and neural development: From cilium to cell division

Tsga10 has been localised in sperm tail as a fibrous sheath protein. In this study, we showed its expression during developmental stages of mouse embryo, in adult mice brain, and in some malignancies. RT-PCR and immunohistochemistry study show that Tsga10 expression starts in 4.5-7.5 dpc mouse embryos and continues throughout embryogenesis. Then we showed that the Tsga10 is expressed in adult brain and in the cells with neural crest origin, olfactory epithelium, and human germ cell tumour. It is expressed with two transcripts in sperm and whole embryos but just with the long transcript in brain embryo as a result of its exon 16 splicing. Our finding of the Tsga10 perinuclear localisation and its expression pattern suggests that it may be involved in active cell division, differentiation, and migrating cells. The results of the experiments in this project hypothesize the presence of Tsga10 protein wherever there is a conserved ciliary structure.

The Mouse t Complex Gene Tsga2, Encoding Polypeptides Located in the Sperm Tail and Anterior Acrosome, Maps to a Locus Associated with Sperm Motility and Sperm-Egg Interaction Abnormalities1

Previous studies of sperm from mice heterozygous for a t haplotype (t) and heterospecific combinations of the t complex identified two tightly linked genetic factors responsible for t/t male sterility related to expression of the flagellar waveform aberration, curlicue. Dnahc8, an axonemal dynein heavy chain gene, is a strong candidate for the proximal factor, Ccua, but the identity of the distal factor, Ccub, is unknown. In the present study, we employ motility assays of sperm from males heterozygous for t and novel heterospecific combinations of the t complex to demonstrate that Ccub is a composite of at least two synergic elements, Ccub1, positioned within a genomic interval spanning approximately 0.6 Mb immediately distal to Dnahc8, and Ccub2, situated in a region approximately 4-7 Mb distal to Ccub1. We also show that Tsga2, a testis-restricted gene, fulfills many of the prerequisites required to make it a strong candidate for Ccub1. These include: 1) its location within the aforementioned genomic interval; 2) a highly reduced level of testis expression by its heterospecific allele relative to the level of expression of its t allele; 3) determination that TSGA2(t) carries numerous nonsynonymous mutations in residues otherwise highly conserved in all known orthologous proteins; 4) the detection of major TSGA2 polypeptides in sperm protein extracts; and 5) the apparent distribution of these polypeptides in major sperm tail structures. Surprisingly, these TSGA2 isoforms appear to localize in the vicinity of the anterior acrosome, as well, suggesting that Tsga2 may also play a role in sperm-egg interaction. Finally, our results indicate that a TSGA2 polypeptide with apparent similarities to the smaller of the two sperm isoforms is expressed by epididymal cells.

Expression of the testis-specific gene, TSGA10, in Iranian patients with acute lymphoblastic leukemia (ALL)

Testis-specific gene antigen (TSGA10) is expressed in fetus, testis and frequently in human solid cancers and acute leukemias, making it a candidate for immunotherapy and for detection of minimal residual disease (MRD). This gene is considered as a member of cancer-testis (CT) genes. We previously demonstrated TSGA10 expression during spermatogenesis. There is also evidence for potential TSGA10 involvement in cell proliferation. TSGA10 expression has been observed in a wide spectrum of cancers but not in hematopoietic neoplasm. Here we demonstrated expression of TSGA10 by semi-quantitative RT-PCR in 44 (84.6%) out of 52 bone marrow samples and all peripheral blood samples from patients with acute lymphoblastic leukemia (ALL). Twenty-seven (52%) cases had high level of gene expression and 16 (30.7%) cases had a lower expression level of the gene in the patients bone marrow. Presence of TSGA10 expression in ALL may open a window to functional study of mitotic checkpoint proteins in leukemia. RT-PCR of TSGA10 may help in detection of residual clonal cells leading to early diagnosis and better prognostic qualification of the disease.

Serological analysis of human renal cell carcinoma

Serological analysis of cDNA expression libraries (SEREX) has proven to be a useful technique in the quest to elucidate the repertoire of immunogenic gene products in human cancer. We have applied the SEREX method to human renal cell carcinoma (RCC) in order to identify associated immunogenic gene products. cDNA expression libraries were prepared from a RCC tumor, a RCC cell line and human testis. The 3 libraries were screened with sera from 35 RCC patients and 15 healthy controls. Approximately 4.5 x 10(6) phage plaques were screened resulting in 234 positive clones, which corresponded to 74 different gene products. The seroreactivity toward 49 of these antigens was assessed. Seroreactivity to 21 (43%) of the antigens was similar in RCC patients and healthy controls, 9 antigens (18%) elicited antibodies more frequently and 19 antigens (39%) solely in RCC patients. In the reverse setting, reactivity of RCC patients' sera was tested against a panel of 44 previously identified "tumor-associated" antigens via the SADA (serum antibody detection array) method; 6 antigens reacted with RCC patients' and healthy donors' sera, 8 were reactive only with RCC patients' sera. From the 27 antigens identified by SEREX and SADA, which did not react with sera from healthy controls, 10 antigens reacted with a significant proportion of RCC patients' sera and 77% of RCC patients' sera reacted at least with one of these antigens. Sera from patients with non-malignant renal diseases or an autoimmune disease did not react with these 10 antigens.

Identification of the testis-specific protein 10 (TSGA10) as serologically defined tumour-associated antigen in primary cutaneous T-cell lymphoma

BACKGROUND

The number of identified tumour-associated antigens for cutaneous lymphoma is still very restricted, which limits the elucidation of the tumour immunology of these malignancies and the development of specific immunotherapies and immunodiagnostics.

OBJECTIVES

To identify new serologically defined antigens associated with cutaneous lymphoma.

METHODS

A phage expression library of the human testis transcriptom was established and immunoscreened with sera from 100 patients with cutaneous lymphoma and nine with parapsoriasis, and 81 age-matched control donors. Positive expression clones were sequenced to identify the respective antigen.

RESULTS

The testis-specific protein 10 (TSGA10) was identified as an antigen recognized by sera of two patients with Mycosis fungoides but not by sera from healthy donors. By reverse transcription-polymerase chain reaction analysis, TSGA10 was found expressed in all cutaneous lymphoma samples tested, various tumour cell lines, testis, peripheral blood mononuclear cells, skin, isolated lymphocytes, keratinocytes and fibroblasts. TSGA10 overexpression had previously been reported for other cancers.

CONCLUSIONS

TSGA10 is a new tumour-associated antigen of cutaneous lymphoma.

Dissecting the axoneme interactome: the mammalian orthologue of Chlamydomonas PF6 interacts with sperm-associated antigen 6, the mammalian orthologue of Chlamydomonas PF16

The axoneme central apparatus is thought to control flagellar/ciliary waveform and maintain the structural integrity of the axoneme, but proteins involved in these processes have not been fully elucidated. Moreover the network of interactions among them that allows these events to take place in a compact space has not been defined. PF6, a component of the Chlamydomonas central apparatus, is localized to the 1a projection of the C1 microtubule. Mutations in the Chlamydomonas PF6 gene result in flagellar paralysis. We characterized human and murine orthologues of PF6. The murine Pf6 gene is expressed in a pattern consistent with a role in flagella and cilia, and the PF6 protein is indeed localized to the central apparatus of the sperm flagellar axoneme. We discovered that a portion of PF6 associates with the mammalian orthologue of Chlamydomonas PF16 (sperm-associated antigen 6 (SPAG6)), another central apparatus protein that is localized to the C1 microtubule in algae. A fragment of PF6 corresponding to the PF6 domain that interacts with SPAG6 in yeast two-hybrid assays and colocalizes with SPAG6 in transfected cells was missing from epididymal sperm of SPAG6-deficient mice. SPAG6 binds to the mammalian orthologue of PF20, which in Chlamydomonas is located in bridges connecting the C2 and C1 microtubules. Thus, PF6, SPAG6, and PF20 form a newly identified network that links together components of the axoneme central apparatus and presumably participates in its dynamic regulation of ciliary and flagellar beat.

A novel testicular RhoGAP-domain protein induces apoptosis

The GTPase-activating proteins (GAPs) accelerate the hydrolysis of GTP to GDP by small GTPases. The GTPases play diverse roles in many cellular processes, including proliferation, cell motility, endocytosis, nuclear import/export, and nuclear membrane formation. Little is known about GAP-domain proteins in spermatogenesis. We isolated a novel RhoGAP domain-containing tGAP1 protein from male germ cells that exhibits unusual properties. The tGAP1 is expressed at low levels in early spermatogonia. Robust transcription initiates in midpachytene spermatocytes and continues after meiosis. The 175-kDa tGAP1 protein localizes to the cytoplasm of spermatocytes and to the cytoplasm and nucleus in spermatids. The protein contains four GAP domain-related sequences, in contrast to all other GAP proteins that harbor one such domain. No activity toward RhoA, Rac1, or Cdc42 could be detected. Results of transfection studies in various somatic cells indicated that low-level tGAP1 expression significantly slows down the cell cycle. Expression of higher levels of tGAP1 by infection of somatic cells with recombinant adenoviruses demonstrated that tGAP1 efficiently induces apoptosis, which to our knowledge is the first such demonstration for a RhoGAP protein. Based on its subcellular location in spermatids and its activity, tGAP1 may play a role in nuclear import/export.