A novel testis-specific metallothionein-like protein, tesmin, is an early marker of male germ cell differentiation

Clinical Significance and Functional Insights of Tesmin in Hepatocellular Carcinoma

Background

Tesmin, a 60 kDa protein encoded by the metallothionein-like 5 (MTL5) gene, plays a vital role in spermatogenesis and oogenesis. Recent research has unveiled its potential involvement in malignancies, although its impact on HCC remains poorly understood.

Methods

In this study, we sought to elucidate the clinical significance of tesmin in HCC patients. We investigated the relationship between tesmin expression and the prognosis of individuals with hepatocellular carcinoma (HCC), as well as its potential role in tumor proliferation and invasion. Immunohistochemistry (IHC) was employed to assess the expression of tesmin in HCC tissues. Chi-square tests were conducted to analyze the correlation between tesmin expression and various clinicopathological features among HCC patients. For survival analysis, we employed the Kaplan-Meier method and conducted Cox regression analyses. To investigate the functional role of tesmin, we utilized shRNA constructs for transfection-mediated knockdown. Proliferation was assessed using the CCK-8 assay, and invasive capability was determined through Matrigel Transwell assays.

Results

IHC results indicated that tesmin expression was prominently observed in cancerous tissue. Notably, we observed a significant association between tesmin expression and tumor stage and invasion in HCC patients from both our medical center and TCGA dataset. Survival analysis further revealed that tesmin expression emerged as an independent prognostic factor for overall survival among individuals with HCC. Furthermore, cellular experiments demonstrated that knockdown of tesmin led to decreased proliferation and invasion of HCC cells.

Conclusions

Our findings suggest that tesmin may serve as a novel prognostic marker for HCC, highlighting its potential as a target for further research into HCC treatment. Additionally, the functional experiments support the notion that tesmin may participate in promoting the proliferation and invasion of HCC cells, warranting further investigations into its mechanistic involvement in HCC progression.

Metallothionein-like 5 expression is correlated with poor prognosis and promotes proliferation of cervical squamous cell carcinoma

Cervical cancer represents one of the most important female genital cancers. Cervical squamous cell carcinoma (CESC) accounts for about 90% of all cervical malignancies and the prognosis are unsatisfied. Here we aimed to investigate the clinical relevance of metallothionein-like 5 (MTL5), a novel metallothionein-like protein, in CESC. RT-qPCR and immunohistochemistry staining showed that MTL5 was upregulated in CESC tissues than nontumorous cervix tissues, which is consistent with the data from TCGA database. Kaplan-Meier survival analysis revealed that higher MTL5 can help predict worse prognosis. In addition, Cox hazard regression analysis verified an independent predictive role of MTL5 in CESC. To further investigate the involvement of MTL5 in CESC, we conducted knockdown experiments in two CESC cell lines. As a result, silencing MTL5g significantly inhibited proliferation of CESC cells. Finally, we validated that silencing MTL5 can suppress CESC tumor growth in vivo using the mice subcutaneous xenografts model. Taken together, higher MTL5 indicates worse survival of CESC after surgical resection. Targeting MTL5 represents a potential therapy of CESC by inhibiting tumor growth, which deserves further investigations.

Effect of Environmental Stressors, Xenobiotics, and Oxidative Stress on Male Reproductive and Sexual Health

This article examines the environmental factor-induced oxidative stress (OS) and their effects on male reproductive and sexual health. There are several factors that induce OS, i.e. radition, metal contamination, xenobiotic compounds, and cigarette smoke and lead to cause toxicity in the cells through metabolic or bioenergetic processes. These environmental factors may produce free radicals and enhance the reactive oxygen species (ROS). Free radicals are molecules that include oxygen and disbalance the amount of electrons that can create major chemical chains in the body and cause oxidation. Oxidative damage to cells may impair male fertility and lead to abnormal embryonic development. Moreover, it does not only cause a vast number of health issues such as ageing, cancer, atherosclerosis, insulin resistance, diabetes mellitus, cardiovascular diseases, ischemia-reperfusion injury, and neurodegenerative disorders but also decreases the motility of spermatozoa while increasing sperm DNA damage, impairing sperm mitochondrial membrane lipids and protein kinases. This chapter mainly focuses on the environmental stressors with further discussion on the mechanisms causing congenital impairments due to poor sexual health and transmitting altered signal transduction pathways in male gonadal tissues.

Tesmin, Metallothionein-Like 5, is Required for Spermatogenesis in Mice†

In mammals, more than 2000 genes are specifically or abundantly expressed in testis, but gene knockout studies revealed several are not individually essential for male fertility. Tesmin (Metallothionein-like 5; Mtl5) was originally reported as a testis-specific transcript that encodes a member of the cysteine-rich motif containing metallothionein family. Later studies showed that Tesmin has two splicing variants and both are specifically expressed in male and female germ cells. Herein, we clarified that the long (Tesmin-L) and short (Tesmin-S) transcript forms start expressing from spermatogonia and the spermatocyte stage, respectively, in testis. Furthermore, while Tesmin-deficient female mice are fertile, male mice are infertile due to arrested spermatogenesis at the pachytene stage. We were able to rescue the infertility with a Tesmin-L transgene, where we concluded that TESMIN-L is critical for meiotic completion in spermatogenesis and indispensable for male fertility.

Nuclear translocation of MTL5 from cytoplasm requires its direct interaction with LIN9 and is essential for male meiosis and fertility

Meiosis is essential for the generation of gametes and sexual reproduction, yet the factors and underlying mechanisms regulating meiotic progression remain largely unknown. Here, we showed that MTL5 translocates into nuclei of spermatocytes during zygotene-pachytene transition and ensures meiosis advances beyond pachytene stage. MTL5 shows strong interactions with MuvB core complex components, a well-known transcriptional complex regulating mitotic progression, and the zygotene-pachytene transition of MTL5 is mediated by its direct interaction with the component LIN9, through MTL5 C-terminal 443–475 residues. Male Mtl5^c-mu/c-mu mice expressing the truncated MTL5 (p.Ser445Arg fs*3) that lacks the interaction with LIN9 and is detained in cytoplasm showed male infertility and spermatogenic arrest at pachytene stage, same as that of Mtl5 knockout mice, indicating that the interaction with LIN9 is essential for the nuclear translocation and function of MTL5 during meiosis. Our data demonstrated MTL5 translocates into nuclei during the zygotene-pachytene transition to initiate its function along with the MuvB core complex in pachytene spermatocytes, highlighting a new mechanism regulating the progression of male meiosis.

Meiosis is essential for spermatogenesis and male fertility. However, the factors regulating the progression of meiosis remain largely unknown. We reported the testis specific protein MTL5 translocated into the nuclei of spermatocytes at the zygotene-pachytene transition by direct interaction with LIN9, which is an essential component of MuvB core complex, to promote meiotic progression beyond the pachytene stage. We also showed that MTL5 pulls down MYBL1 and all of the MuvB core complex (except LIN54) in spermatocytes. Given the known role of the MuvB core complex as a cell cycle regulator in mitotic cells, we suggested that MTL5 promotes meiotic progression along with the MuvB core complex to ensure male fertility. Our results indicated a novel function of the MuvB complex in male meiosis and also shed light on the master regulator proteins that control meiotic progression at the pachytene stage. MTL5 is a novel and germ-cell specific regulator of cell cycle progression to function at a specific stage by nuclear translocation in meiosis.

Functional characterization of RebL1 highlights the evolutionary conservation of oncogenic activities of the RBBP4/7 orthologue in Tetrahymena thermophila

Retinoblastoma-binding proteins 4 and 7 (RBBP4 and RBBP7) are two highly homologous human histone chaperones. They function in epigenetic regulation as subunits of multiple chromatin-related complexes and have been implicated in numerous cancers. Due to their overlapping functions, our understanding of RBBP4 and 7, particularly outside of Opisthokonts, has remained limited. Here, we report that in the ciliate protozoan Tetrahymena thermophila a single orthologue of human RBBP4 and 7 proteins, RebL1, physically interacts with histone H4 and functions in multiple epigenetic regulatory pathways. Functional proteomics identified conserved functional links for Tetrahymena RebL1 protein as well as human RBBP4 and 7. We found that putative subunits of multiple chromatin-related complexes including CAF1, Hat1, Rpd3, and MuvB, co-purified with RebL1 during Tetrahymena growth and conjugation. Iterative proteomics analyses revealed that the cell cycle regulatory MuvB-complex in Tetrahymena is composed of at least five subunits including evolutionarily conserved Lin54, Lin9 and RebL1 proteins. Genome-wide analyses indicated that RebL1 and Lin54 (Anqa1) bind within genic and intergenic regions. Moreover, Anqa1 targets primarily promoter regions suggesting a role for Tetrahymena MuvB in transcription regulation. RebL1 depletion inhibited cellular growth and reduced the expression levels of Anqa1 and Lin9. Consistent with observations in glioblastoma tumors, RebL1 depletion suppressed DNA repair protein Rad51 in Tetrahymena, thus underscoring the evolutionarily conserved functions of RBBP4/7 proteins. Our results suggest the essentiality of RebL1 functions in multiple epigenetic regulatory complexes in which it impacts transcription regulation and cellular viability.

Arabidopsis TCX8 functions as a senescence modulator by regulating LOX2 expression

TCX8 localizes to nucleus and has transcriptional repression activity. TCX8 binds to the promoter region of LOX2 encoding lipoxygenase, causing JA biosynthesis suppression, and thereby delays plant senescence. Conserved CXC domain-containing proteins are found in most eukaryotes. Eight TCX proteins, which are homologs of animal CXC-Hinge-CXC (CHC) proteins, were identified in Arabidopsis, and three of them, TSO1, TCX2/SOL2 and TCX3/SOL1, have been reported to affect cell-cycle control. TCX8, one of the TCX family proteins, was believed to be a TF but its precise function has not been reported. Yeast two-hybrid screening revealed TCP20, a TF that binds to the promoter of LOX2 encoding lipoxygenase, as a strong candidate for interaction with TCX8. We confirmed that TCX8 directly interacts with TCP20 using in vitro pull-down assay and in vivo BiFC and observed that TCX8, as a TF, localizes to nucleus. Using EMSA and by analyzing phenotypes of TCX8-overexpression lines, we demonstrated that TCX8 regulates the expression of LOX2 by binding to either cis-element of LOX2 promoter to which TCP20 or TCP4 binds, affecting JA biosynthesis, and thereby delaying plant senescence. Our study provides new information about the role of TCX8 in modulating plant senescence through regulating LOX2 expression.

Cellular and subcellular localization of endogenous phospholipase D6 in seminiferous tubules of mouse testes

Phospholipase D6 (PLD6) plays pivotal roles in mitochondrial dynamics and spermatogenesis, but the cellular and subcellular localization of endogenous PLD6 in testis germ cells is poorly defined. We examined the distribution and subcellular localization of PLD6 in mouse testes using validated specific anti-PLD6 antibodies. Ectopically expressed PLD6 protein was detected in the mitochondria of PLD6-transfected cells, but endogenous PLD6 expression in mouse testes was localized to the perinuclear region of pachytene spermatocytes, and more prominently, to the round (Golgi and cap phases) and elongating spermatids (acrosomal phase); these results suggest that PLD6 is localized to the Golgi apparatus. The distribution of PLD6 in the round spermatids partially overlapped with that of the cis-Golgi marker GM130, indicating that the PLD6 expression corresponded to the GM130-positive subdomains of the Golgi apparatus. Correlative light and electron microscopy revealed that PLD6 expression in developing spermatids was localized almost exclusively to several flattened cisternae, and these structures might correspond to the medial Golgi subcompartment; neither the trans-Golgi networks nor the developing acrosomal system expressed PLD6. Further, we observed that PLD6 interacted with tesmin, a testis-specific transcript necessary for successful spermatogenesis in mouse testes. To our knowledge, these results provide the first evidence of PLD6 as a Golgi-localized protein of pachytene spermatocytes and developing spermatids and suggest that its subcompartment-specific distribution within the Golgi apparatus may be related to the specific functions of this organelle during spermatogenesis.

The role of tesmin in the physiology and pathogenesis of human diseases

Tesmin (Testis-specific metallothionein-like protein) was first observed during meiotic division of spermatocytes in mouse testis. Expression of tesmin was also found in somatic cells of various organs. In addition to the suggested function of regulating the meiotic division of germ cells, the cysteine-rich domains in tesmin structure allow to bind heavy metal ions. In addition, this protein acts as a co-activator of the nuclear mineralocorticoid receptor, which may affect the expression of many other genes. Tesmin could also potentially play a role in disease states such as: chronic obstructive pulmonary disease, osteoporosis, AIDS encephalopathy, as well as neoplasms: acute lymphoblastic leukemia, prostate cancer or non-small cell lung cancer. The above reports on the multifaceted role of tesmin in various disease processes suggest that it could be an interesting direction for further research, what this paper aims to present.

Gene expression profiling informs HPV cervical histopathology but not recurrence/relapse after LEEP in ART-suppressed HIV+HPV+ women

Identification of factors associated with human papillomavirus (HPV) cervical histopathology or recurrence/relapse following loop electrosurgical excision procedure (LEEP) would allow for better management of the disease. We investigated whether gene signatures could (i) associate with HPV cervical histopathology and (ii) identify women with post-LEEP disease recurrence/relapse. Gene array analysis was performed on paraffin-embedded cervical tissue-isolated RNA from two cross-sectional cohorts of antiretroviral therapy (ART)-suppressed HIV+HPV+ coinfected women: (i) 55 women in South Africa recruited into three groups: high risk (HR) (-) (n = 16) and HR (+) (n = 15) HPV without cervical histopathology and HR (+) HPV with cervical intraepithelial neoplasia (CIN) grade 1/2/3 (n = 24), (ii) 28 women in Botswana with CIN2/3 treated with LEEP 12-month prior to recruitment and presenting with (n = 13) and without (n = 15) lesion recurrence/relapse (tissue was analyzed at first LEEP). Three distinct gene expression signatures identified were able to segregate: (i) HR+ HPV and CIN1/2/3, (ii) HR HPV-free and cervical histopathology-free and (iii) HR+ HPV and cervical histopathology-free. Immune activation and neoplasia-associated genes (n = 272 genes; e.g. IL-1A, IL-8, TCAM1, POU4F1, MCM2, SMC1B, CXCL6, MMP12) were a feature of cancer precursor dysplasia within HR HPV infection. No difference in LEEP tissue gene expression was detected between women with or without recurrence/relapse. In conclusion, distinctive gene signatures were associated with presence of cervical histopathology in tissues from ART-suppressed HIV+/HPV+ coinfected women. Lack of detection of LEEP tissue gene signature able to segregate subsequent post-LEEP disease recurrence/relapse indicates additional factors independent of local gene expression as determinants of recurrence/relapse.

Role of metallothionein-like cadmium-binding protein (MTLCdBP) in the protective mechanism against cadmium toxicity in the testis

The role of metallothionein (MT)-like cadmium (Cd) binding protein (MTLCdBP) in protecting the testes against Cd toxicity was examined. In the acute Cd exposure treatment, cadmium chloride was intraperitoneally injected at 2 mg Cd/kg to Wistar male rats. In the chronic Cd toxicity treatments, 20 mg Cd/kg/d was orally administered for 5 d a week for 5, 10, and 15 wk. MT (-I,-II) and MTLCdBP were measured using ELISA and Cd-Hem methods, respectively. Testicular tissues were immunostained with antibodies of MT-I,-II, MT-III, and MTLCdBP. Expression of HO1, OGG, iNOS, COX2, and p53 was measured by RT-PCR. Cd concentration in the testis increased dose-dependently in response to Cd exposure. MTLCdBP concentration increased markedly with increasing Cd accumulation. Significant increases in expression of iNOS, HO1, COX2, and OGG1 were observed in the acute exposure treatment. In the chronic oral administration group, expression of MT-I, MT-II, MT-III, iNOS, HO1, and COX2 did not change. Positive immunostaining of MTLCdBP was observed in testicular interstitial tissue. In the testis protected from Cd toxicity, MTLCdBP induction increased significantly with increasing Cd accumulation. Our results suggest that MTLCdBP plays an important role in protecting the testis against Cd toxicity.

Gene identification and antimicrobial activity analysis of a novel lysozyme from razor clam Sinonovacula constricta

Lysozymes are important immune effectors present in phylogenetically diverse organisms. They play vital roles in bacterial elimination during early immune responses. In the present study, a second invertebrate-type (i-type) lysozyme gene from razor clam Sinonovacula constricta (denoted as ScLYZ-2) was cloned by RACE and nested PCR methods. The full-length cDNA sequences of ScLYZ-2 were 1558 bp, including a 5' untranslated region (UTR) of 375 bp, an open reading frame of 426 bp, and a 3'-UTR of 757 bp with polyadenylation signal sequence (AATAAA) located upstream of the poly(A) tail. SMART analysis showed that ScLYZ-2 contains a signal peptide in the first 16 amino acid (AA) sequences and a destabilase domain located from 24 to 134 AA sequences. The deduced AA sequences of ScLYZ-2 were highly similar (42%-58%) to other known lysozyme genes of bivalve species. Multiple alignments of AA sequences showed that ScLYZ-2 possesses the classical i-type lysozyme family signature of two motifs ["MDVGSLSCGP(Y/F)QIK" and "CL(E/L/R/H)C(I/M)C"] and two catalytic residues (Glu³⁵ and Asp⁴⁶). Moreover, phylogenetic analysis showed that ScLYZ-2 is a new member of the i-type lysozyme family. In healthy razor clams, ScLYZ-2 was highly expressed in the hepatopancreas, followed by the gills, water pipes, and abdominal foot. Lysozyme activity and ScLYZ-2 expression levels were significantly upregulated in the hepatopancreas and gills after being infected with V. splendidus, V. harveyi, V. parahaemolyticus and S. aureus and M. luteus. Moreover, the recombinant ScLYZ-2 had strong antimicrobial activities against V. splendidus, V. harveyi, and V. parahaemolyticus. Furthermore, the minimal inhibitory concentration of the recombinant ScLYZ-2 against V. parahaemolyticus was 7.2 μmol/mL. Taken together, our results show that ScLYZ-2 plays an important role in the immune defense of razor clam by eliminating pathogenic microorganisms.

Zinc: A Necessary Ion for Mammalian Sperm Fertilization Competency

The importance of zinc for male fertility only emerged recently, being propelled in part by consumer interest in nutritional supplements containing ionic trace minerals. Here, we review the properties, biological roles and cellular mechanisms that are relevant to zinc function in the male reproductive system, survey available peer-reviewed data on nutritional zinc supplementation for fertility improvement in livestock animals and infertility therapy in men, and discuss the recently discovered signaling pathways involving zinc in sperm maturation and fertilization. Emphasis is on the zinc-interacting sperm proteome and its involvement in the regulation of sperm structure and function, from spermatogenesis and epididymal sperm maturation to sperm interactions with the female reproductive tract, capacitation, fertilization, and embryo development. Merits of dietary zinc supplementation and zinc inclusion into semen processing media are considered with livestock artificial insemination (AI) and human assisted reproductive therapy (ART) in mind. Collectively, the currently available data underline the importance of zinc ions for male fertility, which could be harnessed to improve human reproductive health and reproductive efficiency in agriculturally important livestock species. Further research will advance the field of sperm and fertilization biology, provide new research tools, and ultimately optimize semen processing procedures for human infertility therapy and livestock AI.

Long term impact of the endocrine disruptor tributyltin on male fertility following a single acute exposure

Declining rate of human fertility is a growing concern, where lifestyle and environmental factors play an important role. We recently demonstrated that tributyltin (TBT), an omnipresent endocrine disruptor, affects testicular cells in vitro. In this study, male Wistar rats were gavaged a single dose of 10, 20, and 30 mg/kg TBT-chloride (TBTC) (to mimic accidental exposure in vivo) and sacrificed on day 3 and day 7, respectively. TBT bioavailability was evaluated by estimating total tin content, and essential metal levels were analyzed along with redox molecules (ROS and GSH/GSSG) to understand the effect on physiological conditions. Blood-testicular barrier (BTB) disruption, levels of associated proteins and activity of proteolytic enzymes were evaluated to understand the effect on BTB. Histological analysis of tissue architecture and effect on protein expression of steroidogenic, stress and apoptotic markers were also evaluated. Widespread TBTC pollution can be an eventual threat to male fertility worldwide.

Functional relevance for associations between osteoporosis and genetic variants

Osteoporosis is characterized by increased bone loss and deterioration of bone microarchitecture, which will lead to reduced bone strength and increased risk of fragility fractures. Previous studies have identified many genetic loci associated with osteoporosis, but functional mechanisms underlying the associations have rarely been explored. In order to explore the potential molecular functional mechanisms underlying the associations for osteoporosis, we performed integrative analyses by using the publically available datasets and resources. We searched 128 identified osteoporosis associated SNPs (P<10-6), and 8 SNPs exert cis-regulation effects on 11 eQTL target genes. Among the 8 SNPs, 2 SNPs (RPL31 rs2278729 and LRP5 rs3736228) were confirmed to impact the expression of 3 genes (RPL31, CPT1A and MTL5) that were differentially expressed between human subjects of high BMD group and low BMD group. All of the functional evidence suggested the important functional mechanisms underlying the associations of the 2 SNPs (rs2278729 and rs3736228) and 3 genes (RPL31, CPT1A and MTL5) with osteoporosis. This study may provide novel insights into the functional mechanisms underlying the osteoporosis associated genetic variants, which will help us to comprehend the potential mechanisms underlying the genetic association for osteoporosis.

Family-based exome-wide assessment of maternal genetic effects on susceptibility to childhood B-cell acute lymphoblastic leukemia in hispanics

BACKGROUND

Children of Hispanic ancestry have a higher incidence of acute lymphoblastic leukemia (ALL) compared with other ethnic groups, but to the authors' knowledge, the genetic basis for these racial disparities remain incompletely understood. Genome-wide association studies of childhood ALL to date have focused on inherited genetic effects; however, maternal genetic effects (the role of the maternal genotype on phenotype development in the offspring) also may play a role in ALL susceptibility.

METHODS

The authors conducted a family-based exome-wide association study of maternal genetic effects among Hispanics with childhood B-cell ALL using the Illumina Infinium HumanExome BeadChip. A discovery cohort of 312 Guatemalan and Hispanic American families and an independent replication cohort of 152 Hispanic American families were used.

RESULTS

Three maternal single-nucleotide polymorphisms (SNPs) approached the study threshold for significance after correction for multiple testing (P<1.0 × 10^-6 ): MTL5 rs12365708 (testis expressed metallothionein-like protein [tesmin]) (relative risk [RR], 2.62; 95% confidence interval [95% CI], 1.61-4.27 [P = 1.8 × 10^-5 ]); ALKBH1 rs6494 (AlkB homolog 1, histone H2A dioxygenase) (RR, 3.77; 95% CI, 1.84-7.74 [P = 3.7 × 10^-5 ]); and NEUROG3 rs4536103 (neurogenin 3) (RR, 1.75; 95% CI, 1.30-2.37 [P = 1.2 × 10^-4 ]). Although effect sizes were similar, these SNPs were not nominally significant in the replication cohort in the current study. In a meta-analysis comprised of the discovery cohort and the replication cohort, these SNPs were still not found to be statistically significant after correction for multiple comparisons (rs12365708: pooled RR, 2.27 [95% CI, 1.48-3.50], P = 1.99 × 10^-4 ; rs6494: pooled RR, 2.31 [95% CI, 1.38-3.85], P = .001; and rs4536103: pooled RR, 1.67 [95% CI, 1.29-2.16] P = 9.23 × 10^-5 ).

CONCLUSIONS

In what to the authors' knowledge is the first family-based based exome-wide association study to investigate maternal genotype effects associated with childhood ALL, the results did not implicate a strong role of maternal genotype on disease risk among Hispanics; however, 3 maternal SNPs were identified that may play a modest role in susceptibility. Cancer 2016;122:3697-704. © 2016 American Cancer Society.

Structural basis for LIN54 recognition of CHR elements in cell cycle-regulated promoters

The MuvB complex recruits transcription factors to activate or repress genes with cell cycle-dependent expression patterns. MuvB contains the DNA-binding protein LIN54, which directs the complex to promoter cell cycle genes homology region (CHR) elements. Here we characterize the DNA-binding properties of LIN54 and describe the structural basis for recognition of a CHR sequence. We biochemically define the CHR consensus as TTYRAA and determine that two tandem cysteine rich regions are required for high-affinity DNA association. A crystal structure of the LIN54 DNA-binding domain in complex with a CHR sequence reveals that sequence specificity is conferred by two tyrosine residues, which insert into the minor groove of the DNA duplex. We demonstrate that this unique tyrosine-mediated DNA binding is necessary for MuvB recruitment to target promoters. Our results suggest a model in which MuvB binds near transcription start sites and plays a role in positioning downstream nucleosomes.

Decreased spermatogenesis led to alterations of testis-specific gene expression in male mice following nano-TiO2 exposure

Although TiO2 nanoparticles (NPs) exposure has been demonstrated to cross blood-testis barrier and accumulate in the testis resulting in the reduction of sperm numbers, limited data with respect to the molecular mechanism of decreased spermatogenesis caused by TiO2 NP exposure. In this research, testicular damage, sperm number and alterations in testis-specific gene expressions in male mice induced by intragastric administration with TiO2 NPs for six months were investigated. It was found out that TiO2 NPs could migrate to cells, deposit in the testis and epididymis and thus cause damages to relevant organs, which are, to be more specific, the reductions of total sperm concentrations and sperm motility and an enhancement in the number of abnormal sperms in the cauda epididymis. Furthermore, the individual expression regarding to the mRNAs and proteins of testis-specific genes, including Cdc2, Cyclin B1, Dmcl, TERT, Tesmin, TESP-1, XPD and XRCCI, were significantly declined, whereas Gsk3-β and PGAM4 expressions were greatly elevated in mouse testis due to the exposures, which in fact implied that the reduced spermatogenesis may be involved in the alternated testis-specific gene expressions in those exposed male mice.

Mechanism of Wnt signaling induced down regulation of mrhl long non-coding RNA in mouse spermatogonial cells

Long non coding RNAs (lncRNAs) have emerged as important regulators of various biological processes. LncRNAs also behave as response elements or targets of signaling pathway(s) mediating cellular function. Wnt signaling is important in regulating mammalian spermatogenesis. Mrhl RNA negatively regulates canonical Wnt pathway and gets down regulated upon Wnt signaling activation in mouse spermatogonial cells. Also, mrhl RNA regulates expression of genes pertaining to Wnt pathway and spermatogenesis by binding to chromatin. In the present study, we delineate the detailed molecular mechanism of Wnt signaling induced mrhl RNA down regulation in mouse spermatogonial cells. Mrhl RNA has an independent transcription unit and our various experiments like Chromatin Immunoprecipitation (in cell line as well as mouse testis) and shRNA mediated down regulation convincingly show that β-catenin and TCF4, which are the key effector proteins of the Wnt signaling pathway are required for down regulation of mrhl RNA. We have identified Ctbp1 as the co-repressor and its occupancy on mrhl RNA promoter depends on both β-catenin and TCF4. Upon Wnt signaling activation, Ctbp1 mediated histone repression marks increase at the mrhl RNA promoter. We also demonstrate that Wnt signaling induced mrhl RNA down regulation results in an up regulation of various meiotic differentiation marker genes.

Fractionation of human spermatogenic cells using STA-PUT gravity sedimentation and their miRNA profiling

Human spermatogenic cells have not yet been isolated, and notably, their global miRNA profiles remain unknown. Here we have effectively isolated human spermatogonia, pachytene spermatocytes and round spermatids using STA-PUT velocity sedimentation. RT-PCR, immunocytochemistry and meiosis spread assays revealed that the purities of isolated human spermatogonia, pachytene spermatocytes, and round spermatids were 90%, and the viability of these isolated cells was over 98%. MiRNA microarrays showed distinct global miRNA profiles among human spermatogonia, pachytene spermatocytes, and round spermatids. Thirty-two miRNAs were significantly up-regulated whereas 78 miRNAs were down-regulated between human spermatogonia and pachytene spermatocytes, suggesting that these miRNAs are involved in the meiosis and mitosis, respectively. In total, 144 miRNAs were significantly up-regulated while 29 miRNAs were down-regulated between pachytene spermatocytes and round spermatids, reflecting potential roles of these miRNAs in mediating spermiogenesis. A number of novel binding targets of miRNAs were further identified using various softwares and verified by real-time PCR. Our ability of isolating human spermatogonia, pachytene spermatocytes and round spermatids and unveiling their distinct global miRNA signatures and novel targets could provide novel small RNA regulatory mechanisms mediating three phases of human spermatogenesis and offer new targets for the treatment of male infertility.

Iron and copper in male reproduction: a double-edged sword

Iron and copper are essential trace nutrients playing important roles in general health and fertility. However, both elements are highly toxic when accumulating in large quantities. Their direct or indirect impact on the structure and function of male gonads and gametes is not completely understood yet. Excess or deficiency of either element may lead to defective spermatogenesis, reduced libido, and oxidative damage to the testicular tissue and spermatozoa, ultimately leading to fertility impairment. This review will detail the complex information currently available on the dual roles iron and copper play in male reproduction.

The protein Compromised Hydrolysis of Triacylglycerols 7 (CHT7) acts as a repressor of cellular quiescence in Chlamydomonas

Microalgae are prolific photosynthetic organisms that have the potential to sustainably produce high-value chemical feedstocks. However, an industry based on microalgal biomass still is faced with challenges. For example, microalgae tend to accumulate valuable compounds, such as triacylglycerols, only under stress conditions that limit growth. To investigate the fundamental mechanisms at the base of this conundrum--the inverse relationship between biomass production and storage compound accumulation-we applied a combination of cell biological and genetic approaches. Conceptually, nutrient deprivation, which commonly is used to induce the accumulation of triacylglycerol in microalgae, leads to a state of cellular quiescence defined by a halt of cell divisions that is reversible upon nutrient resupply. To identify factors that govern cellular quiescence, we screened for mutants of the model alga Chlamydomonas reinhardtii that, in contrast to wild-type cells placed under conditions of nitrogen deprivation, were unable to degrade triacylglycerols following nitrogen resupply. One of the mutants described here in detail, compromised hydrolysis of triacylglycerols 7 (cht7), was severely impaired in regrowth following removal of different conditions inducing cellular quiescence. The mutant carries a deletion affecting four genes, only one of which rescued the quiescence phenotype when reintroduced. It encodes a protein with similarity to mammalian and plant DNA binding proteins. Comparison of transcriptomes indicated a partial derepression of quiescence-related transcriptional programs in the mutant under conditions favorable to growth. Thus, CHT7 likely is a repressor of cellular quiescence and provides a possible target for the engineering of high-biomass/high-triacylglycerol microalgae.

LIN54 harboring a mutation in CHC domain is localized to the cytoplasm and inhibits cell cycle progression

The mammalian LIN complex (LINC) plays important roles in regulation of cell cycle genes. LIN54 is an essential core subunit of the LINC and has a DNA binding region (CHC domain), which consists of two cysteine-rich (CXC) domains separated by a short spacer. We generated various LIN54 mutants, such as CHC deletion mutant, and investigated their subcellular localizations and effects on cell cycle. Wild-type LIN54 was predominantly localized in the nucleus. We identified two nuclear localization signals (NLSs), both of which were required for nuclear localization of LIN54. Interestingly, deletion of one CXC domain resulted in an increased cytoplasmic localization. The cytoplasmic LIN54 mutant accumulated in the nucleus after leptomycin B treatment, suggesting CRM1-mediated nuclear export of LIN54. Point mutations (C525Y and C611Y) in conserved cysteine residues of CXC domain that abolish DNA binding activity also increased cytoplasmic localization. These data suggest that DNA binding activity of LIN54 is required for its nuclear retention. We also found that LIN54 (C525Y) and LIN54 (C611Y) inhibited cell cycle progression and led to abnormal nuclear morphology. Other CXC mutants also induced similar abnormalities in cell cycle progression. LIN54 (C525Y) led to a decreased expression of some G2/M genes, whose expressions are regulated by LINC. This cell cycle inhibition was partially restored by overexpression of wild-type LIN54. These results suggest that abnormal cellular localization of LIN54 may have effects on LINC activity.

Recessive antimorphic alleles overcome functionally redundant loci to reveal TSO1 function in Arabidopsis flowers and meristems

Arabidopsis TSO1 encodes a protein with conserved CXC domains known to bind DNA and is homologous to animal proteins that function in chromatin complexes. tso1 mutants fall into two classes due to their distinct phenotypes. Class I, represented by two different missense mutations in the CXC domain, leads to failure in floral organ development, sterility, and fasciated inflorescence meristems. Class II, represented by a nonsense mutation and a T-DNA insertion line, develops wild-type–like flowers and inflorescences but shows severely reduced fertility. The phenotypic variability of tso1 alleles presents challenges in determining the true function of TSO1. In this study, we use artificial microRNA, double mutant analysis, and bimolecular fluorescence complementation assay to investigate the molecular basis underlying these two distinct classes of phenotypes. We show that the class I mutants could be converted into class II by artificial microRNA knockdown of the tso1 mutant transcript, suggesting that class I alleles produce antimorphic mutant proteins that interfere with functionally redundant loci. We identified one such redundant factor coded by the closely related TSO1 homolog SOL2. We show that the class I phenotype can be mimicked by knocking out both TSO1 and its homolog SOL2 in double mutants. Such antimorphic alleles targeting redundant factors are likely prevalent in Arabidopsis and maybe common in organisms with many sets of paralogous genes such as human. Our data challenge the conventional view that recessive alleles are always hypomorphic or null and that antimorphic alleles are always dominant. This study shows that recessive alleles can also be antimorphic and can produce a phenotype more severe than null by interfering with the function of related loci. This finding adds a new paradigm to classical genetic concepts, with important implications for future genetic studies both in basic research as well as in agriculture and medicine.

Much of our current genetic concepts and terms came from early pioneering work in Drosophila melanogaster, which has a relatively simple genome with reduced gene sets. One noted example is the term antimorph or dominant-negative, which describes mutant proteins that antagonize the corresponding wild-type proteins in a dominant fashion. In the process of characterizing Arabidopsis thaliana tso1 mutants, we discovered a novel genetic phenomenon “recessive antimorphism,” where certain recessive and missense mutations interfere with functionally redundant genes in the genome to reveal a broader range of phenotypes than the corresponding loss-of-function or null alleles. Our work indicates a rarely noted strength of Arabidopsis as a genetic model for studying species with complex genome architecture, including humans that possess significant chromosome segmental or genome duplications and increased gene copy numbers. It adds a new paradigm to classical genetic concepts with important implications for modern genetics in both medicine and agriculture.

Zinc is an essential trace element for spermatogenesis

Zinc (Zn) plays important roles in various biological activities but there is little available information regarding its functions in spermatogenesis. In our current study, we further examined the role of Zn during spermatogenesis in the Japanese eel (Anguilla japonica). Human CG (hCG) was injected into the animals to induce spermatogenesis, after which the concentration of Zn in the testis increased in tandem with the progression of spermatogenesis. Staining of testicular cells with a Zn-specific fluorescent probe revealed that Zn accumulates in germ cells, particularly in the mitochondria of spermatogonia and spermatozoa. Using an in vitro testicular organ culture system for the Japanese eel, production of a Zn deficiency by chelation with N,N,N',N'-tetrakis (2-pyridylemethyl)ethylenediamine (TPEN) caused apoptosis of the germ cells. However, this cell death was rescued by the addition of Zn to the cultures. Furthermore, an induced deficiency of Zn by TPEN chelation was found to inhibit the germ cell proliferation induced by 11-ketotestosterone (KT), a fish specific androgen, 17alpha,20beta-dihydroxy-4-pregnen-3-one (DHP), the initiator of meiosis in fish, and estradiol-17beta (E2), an inducer of spermatogonial stem-cell renewal. We also investigated the effects of Zn deficiency on sperm motility and observed that TPEN treatment of eel sperm suppressed the rate and duration of their motility but that co-treatment with Zn blocked the effects of TPEN. Our present results thus suggest that Zn is an essential trace element for the maintenance of germ cells, the progression spermatogenesis, and the regulation of sperm motility.

Cadmium-induced testicular injury

Cadmium (Cd) is an environmental toxicant and an endocrine disruptor in humans and rodents. Several organs (e.g., kidney, liver) are affected by Cd and recent studies have illustrated that the testis is exceedingly sensitive to Cd toxicity. More important, Cd and other toxicants, such as heavy metals (e.g., lead, mercury) and estrogenic-based compounds (e.g., bisphenols) may account for the recent declining fertility in men among developed countries by reducing sperm count and testis function. In this review, we critically discuss recent data in the field that have demonstrated the Cd-induced toxicity to the testis is probably the result of interactions of a complex network of causes. This is likely to involve the disruption of the blood-testis barrier (BTB) via specific signal transduction pathways and signaling molecules, such as p38 mitogen-activated protein kinase (MAPK). We also summarize current studies on factors that confer and/or regulate the testis sensitivity to Cd, such as Cd transporters and metallothioneins, the impact of Cd on the testis as an endocrine disruptor and oxidative stress inducer, and how it may disrupt the Zn(2+) and/or Ca(2+) mediated cellular events. While much work is needed before a unified mechanistic pathway of Cd-induced testicular toxicity emerges, recent studies have helped to identify some of the likely mechanisms and/or events that take place during Cd-induced testis injury. Furthermore, some of the recent studies have shed lights on potential therapeutic or preventive approaches that can be developed in future studies by blocking or minimizing the destructive effects of Cd to testicular function in men.

Transcriptome analysis of differentiating spermatogonia stimulated with kit ligand

Kit ligand (KL) is a survival factor and a mitogenic stimulus for differentiating spermatogonia. However, it is not known whether KL also plays a role in the differentiative events that lead to meiotic entry of these cells. We performed a wide genome analysis of difference in gene expression induced by treatment with KL of spermatogonia from 7-day-old mice, using gene chips spanning the whole mouse genome. The analysis revealed that the pattern of RNA expression induced by KL is compatible with the qualitative changes of the cell cycle that occur during the subsequent cell divisions in type A and B spermatogonia, i.e. the progressive lengthening of the S phase and the shortening of the G2/M transition. Moreover, KL up-regulates in differentiating spermatogonia the expression of early meiotic genes (for instance: Lhx8, Nek1, Rnf141, Xrcc3, Tpo1, Tbca, Xrcc2, Mesp1, Phf7, Rtel1), whereas it down-regulates typical spermatogonial markers (for instance: Pole, Ptgs2, Zfpm2, Egr2, Egr3, Gsk3b, Hnrpa1, Fst, Ptch2). Since KL modifies the expression of several genes known to be up-regulated or down-regulated in spermatogonia during the transition from the mitotic to the meiotic cell cycle, these results are consistent with a role of the KL/kit interaction in the induction of their meiotic differentiation.

Gfra1 silencing in mouse spermatogonial stem cells results in their differentiation via the inactivation of RET tyrosine kinase

Spermatogenesis is the process by which spermatogonial stem cells divide and differentiate into sperm. The role of growth factor receptors in regulating self-renewal and differentiation of spermatogonial stem cells remains largely unclear. This study was designed to examine Gfra1 receptor expression in immature and adult mouse testes and determine the effects of Gfra1 knockdown on the proliferation and differentiation of type A spermatogonia. We demonstrated that GFRA1 was expressed in a subpopulation of spermatogonia in immature and adult mice. Neither Gfra1 mRNA nor GFRA1 protein was detected in pachytene spermatocytes and round spermatids. GFRA1 and POU5F1 (also known as OCT4), a marker for spermatogonial stem cells, were co-expressed in a subpopulation of type A spermatogonia from 6-day-old mice. In addition, the spermatogonia expressing GFRA1 exhibited a potential for proliferation and the ability to form colonies in culture, which is a characteristic of stem cells. RNA interference assays showed that Gfra1 small interfering RNAs (siRNAs) knocked down the expression of Gfra1 mRNA and GFRA1 protein in type A spermatogonia. Notably, the reduction of Gfra1 expression by Gfra1 siRNAs induced a phenotypic differentiation, as evidenced by the elevated expression of KIT, as well as the decreased expression of POU5F1 and proliferating cell nuclear antigen (PCNA). Furthermore, Gfra1 silencing resulted in a decrease in RET phosphorylation. Taken together, these data indicate that Gfra1 is expressed dominantly in mouse spermatogonial stem cells and that Gfra1 knockdown leads to their differentiation via the inactivation of RET tyrosine kinase, suggesting an essential role for Gfra1 in spermatogonial stem cell regulation.

Identification of differentially expressed genes in senescence-accelerated mouse testes by suppression subtractive hybridization analysis

Senescence-accelerated mouse (SAM) strains constitute a model of accelerated senescence coupled with a short lifespan and the early development of various age-related disorders. To identify differential gene expression in testes between senescence-accelerated SAMP1 and control SAMR1 mice, we performed suppression subtractive hybridization. We observed that the expression of three genes related to cell proliferation (myosin regulatory light chain B, aldolase 1A isoform, and cytochrome c oxidase subunit VIc) were upregulated and four genes implicated in spermatogenesis were downregulated in SAMP1 mice. Asb-8, a member of ankyrin repeat-containing proteins, was abundantly expressed in the testes and downregulated in SAMP1. The other three downregulated genes (germ cell-specific gene 1, T-complex polypeptide 1b, and activator of cAMP responsive element modulator in testis) have been reported to regulate late-stage spermatogenesis. These gene expression profiles might explain the findings of early testicular maturation and rapid decline in the ability to produce spermatozoa with advancing age in SAMP1 mice.

Identification and characteristics of a novel testis-specific gene, Tsc24, in human and mice

Testis-specific genes are essential for the spermatogenesis in mammalian male reproduction. We have identified a novel gene, Tsc24, from the results of the Affymetrix Genechip analysis in the developmental stage of days 4, 9, 18, 35, 54 and 6 months of postnatal Balb/C mouse testis. The scaling signal intensities of Tsc24 in the six stages of mouse testis showed that the expression of Tsc24 was not detected on day 4, 9 or 18 but on day 35, 54 and 6 months. The full cDNA length of mouse Tsc24 was 899 bp, with a 624 bp open reading frame encoding a 207 amino acid protein with a predicted molecular weight of 23.997 kDa. The results of semi-quantitative RT-PCR showed that the expression of mouse Tsc24 can only be detected after the mouse was 35 d old and the expressing level increased gradually from day 35 to 6 months. Of the eight tissues (liver, spleen, heart, lung, brain, kidney, epididymis, and testis) examined in mice, and of the 12 tissues (liver, kidney, muscle, brain, spleen, adipose, lung, heart, epididymis, testis, ovary and uterus) examined in human, Tsc24 was exclusively expressed in the testis, but in none of the other studied tissues. The result of subcellular localization of GFP-Tsc24 fusion protein in Cos-7 cells supports that Tsc24 protein is expressed in nuclear. Our study should be a basis for function characterization of the Tsc24 gene, leading to the elucidation of the molecular events underlying mammalian male reproduction.

The conserved cysteine-rich domain of a tesmin/TSO1-like protein binds zinc in vitro and TSO1 is required for both male and female fertility in Arabidopsis thaliana

Development of reproductive tissue and control of cell division are common challenges to all sexually reproducing eukaryotes. The Arabidopsis thaliana TSO1 gene is involved in both these processes. Mild tso1 mutant alleles influence only ovule development, whereas strong alleles have an effect on all floral tissues and cause cell division defects. The tso1 mutants described so far carry point mutations in a conserved cysteine-rich domain, the CRC domain, but the reason for the range of phenotypes observed is poorly understood. In the present study, the tesmin/TSO1-like CXC (TCX) proteins are characterized at the biochemical, genomic, transcriptomic, and functional level to address this question. It is shown that the CRC domain binds zinc, offering an explanation for the severity of tso1 alleles where cysteine residues are affected. In addition, the phylogenetic and expression analysis of the TCX genes suggested an overlap in function between AtTSO1 and the related gene AtTCX2. Their expression ratios indicated that pollen, in addition to ovules, would be sensitive to loss of TSO1 function. This was confirmed by analysis of novel tso1 T-DNA insertion alleles where the development of both pollen and ovules was affected.

Characteristics of 292 Testis-Specific Genes in Human

To explore their genomic and functional characteristics, 292 human testis-specific genes were obtained from a UniGene library and a full-scale analysis was made. Various bioinformatics tools were applied to analyze the gene ontology and chromosome location, and the expression profiles of eight selected candidates from the 292 genes were analyzed using RT-PCR for 12 adult human tissues. The results showed that of the total 292 genes, 153 were known (114 assigned genes and 39 named genes), and 139 were unknown. Of the 114 assigned genes, 63 were labeled to molecular function, 28 to cellular component, 23 to biological process. All 292 genes are distributed on human chromosomes at different gene density, lower gene density appears on chromosomes 21 (R=0.22), X (R=0.33), 14 (R=0.39), 10 (R=0.61), 8 (R=0.63), and 18 (R=0.67) and higher density on chromosomes 19 (R=3.65), 20 (R=1.83), 16 (R=1.74), and 17 (R=1.64). The expression profile of the eight selected genes in the 12 human tissues showed that five candidate genes: Hs.443729, Hs.115366, Hs.558087, Hs.534501, and Hs.132104 were expressed exclusively in human testis; Hs.132310, Hs.443299 were expressed highly in testis and also expressed weakly in human heart; Hs.160370 was expressed in human testis, ovary, uterus, and not expressed in other tissues. Our study can be a basis for characterization of the function of human testis-specific genes during male mammalian spermatogenesis.

Identification and characteristics of a novel testis-specific gene, Tsc21, in mice and human

Testis-specific genes are essential for spermatogenesis in mammalian male reproduction. We have identified a novel gene, Tsc21, exclusively expressed in mice and human testes from the results of the Affymetrix Genechip analysis in the six developmental stages of testis of postnatal Balb/C mice. The full cDNA length of Tsc21 was 810 bp, with a 543 bp open reading frame encoding a 180 amino acids protein with a predicted molecular weight of 21.040 kDa. A Blast search in the mouse genome database localized the Tsc21 gene to mice chromosome 6C3. Multiple amino acid sequence alignment of human, mouse, and rat homologous genes showed that mice Tsc21 protein was highly homologous with the human Tsc21 gene (70%) and rat Tsc21 gene (86%). The results of reverse transcriptase-polymerase chain reaction analysis showed that the mice Tsc21 is exclusively expressed in the testis and epididymis of mice, and its expression is only detected after the mice is 35 days old. Human Tsc21 is also exclusively expressed in testis of human. Considering the expression profile Tsc21 in mice and human, we propose that Tsc21 may play a role during mammalian male spermatogenesis. Our study should be a basis for function characterization of the Tsc21 gene, leading to the elucidation of the molecular events underlying mammalian male reproduction.

Insights into human CD34+ hematopoietic stem/progenitor cells through a systematically proteomic survey coupled with transcriptome

Hematopoietic stem cells are capable of self-renewal and differentiation into different hematopoietic lineages. To gain a comprehensive understanding of hematopoietic stem/progenitor cells, a systematic proteomic survey of human CD34+ cells collected from human umbilical cord blood was performed, in which the proteins were separated by 1- and 2-DE, as well as by nano-LC, and subsequently identified by MS. A total of 370 distinct proteins identified from those cells provided new insights into the potential of the stem/progenitor cells because the nerve, gonad, and eye-associated proteins were reliably identified. Interestingly, the transcripts of 133 (35.9%) identified proteins were not found by the prevalent transcriptome approaches, although several selected transcripts could be detected by RT-PCR. Moreover, the heterogeneity of 33 proteins identified from 2-DE was attributable primarily to post-translational processes rather than to alternative splicing at transcriptional level. Furthermore, the biosyntheses of 15 proteins identified in this study appears not to be completely interrupted in spite of the fact that corresponding antisense RNAs were found in the existing transcriptome data. The integrated proteomic and transcriptomic analyses employed here provided a unique view of the human stem/progenitor cells.

Cytokines and junction restructuring during spermatogenesis—a lesson to learn from the testis

In the mammalian testis, preleptotene and leptotene spermatocytes residing in the basal compartment of the seminiferous epithelium must traverse the blood-testis barrier (BTB) at late stage VIII through early stage IX of the epithelial cycle during spermatogenesis, entering the adluminal compartment for further development. However, until recently the regulatory mechanisms that regulate BTB dynamics remained largely unknown. We provide a critical review regarding the significance of cytokines in regulating the 'opening' and 'closing' of the BTB. We also discuss how cytokines may be working in concert with adaptors that selectively govern the downstream signaling pathways. This process, in turn, regulates the dynamics of either Sertoli-Sertoli tight junction (TJ), Sertoli-germ cell adherens junction (AJ), or both junction types in the epithelium, thereby permitting TJ opening without compromising AJs, and vice versa. We also discuss how adaptors alter their protein-protein association with the integral membrane proteins at the cell-cell interface via changes in their phosphorylation status, thereby altering adhesion function at AJ. These findings illustrate that the testis is a novel in vivo model to study the biology of junction restructuring. Furthermore, a molecular model is presented regarding how cytokines selectively regulate TJ/AJ restructuring in the epithelium during spermatogenesis.

Nuclear trafficking of metallothionein requires oxidation of a cytosolic partner

The present study revealed the mechanism underlying the nuclear trafficking of metallothionein (MT). Nuclear localization of MT in digitonin-permeabilized BALB 3T3 cells was enhanced in the presence of a cytosolic factor added as a rat red blood cell lysate by oxidation with H2O2 in a dose-dependent manner, but inhibited with excess glutathione. A cytosolic partner was assumed to bind MT and retain it in the cytoplasm, and its oxidation can mobilize MT to the nuclei on cellular oxidation. Pre-treatment of nuclei with H2O2 did not enhance the localization, and MT that had been localized in the nuclei was washed out, indicating that MT is in the nuclei as a result of a higher rate of uptake by the nuclei than the rate of diffusion from the nuclei. Nuclear localization of lysozyme and nuclear localization signal (NLS)-bearing allophycocyanin were not enhanced by the oxidation in the presence of cytosolic factor, suggesting that the nuclear traffic occurring on oxidation is specific to MT. Moreover, when cells were arrested the cell cycle at the S phase, MT was localized in the nuclei in response to coincidental generation of a feeble reactive oxygen species (ROS). These observations suggest that MT comes localized in the nuclei on the sensing of intracellular oxidation, whereby a cytosolic partner specific to MT comes oxidized as a cargo system, MT being localized as a result of enhanced uptake in the nuclei and re-localized in the cytoplasm diffusely. Nuclear MT was proposed to protect the nuclei from the oxidation occurring with progression of the cell cycle.

Dose and Dose-Rate Effects of Low-Dose Ionizing Radiation on Activation of Trp53 in Immortalized Murine Cells

A derivative of immortalized murine NIH/PG13Luc cells stably transfected with a Trp53-dependent luciferase reporter plasmid was used to study the transcriptional activity of Trp53 in response to radiation. The cell line was sensitive enough to detect the response of Trp53 to 0.2 cGy of (60)Co gamma radiation. To examine the biological effects of low-dose-rate (60)Co gamma radiation (from 0.1-10 cGy/h), we have analyzed the cell cycle, Trp53 transcriptional activity, and gene expression profiles of control and treated cells. Microarray analysis revealed up-regulation of six Trp53-mediated genes (Cdkn1a/ p21, Mdm2, Sip27, Ccng1/cyclin G1, Ei24/Pig8 and Dinb/ Polk) after exposure of cells to low-dose-rate radiation for 72 h. Using real-time PCR, a significant elevation in the expression of Ccng1/cyclin G1, Mdm2 and Cdkn1A/p21 was observed with low-dose-rate irradiation at dose rates over 5 cGy/ h. A dose-rate dependence was also observed for these three Trp53-mediated genes. The expression of Ccng1/cyclin G1 at high dose rates of gamma rays was higher than that for low dose rate. However, the expression of Mdm2 for low-dose-rate gamma rays was higher than for the high dose rate. Cells irradiated at low dose rates of 0.1 cGy/h and 1 cGy/h underwent G(1)-phase arrest. Furthermore, G(2)-phase growth arrest was observed in cells irradiated at the low dose rates of 5 cGy/h and 10 cGy/h, which correlated with Trp53-mediated Ccng1/cyclin G1 up-regulation. These results show that cellular response to radiation depended on the dose rate used; i.e., the responses seen at dose rates from 0.1-1 cGy/h were different from those observed at dose rates over 5 cGy/h.

Tesmin transcription is regulated differently during male and female meiosis

Tesmin is a protein with homology to the metal-binding motif of the metallothionein protein family. Tesmin has been described as a testis-specific transcript, which starts to accumulate in 8-day-old mouse spermatocytes. Herein, a differential display comparing meiotic gene expression in embryonic ovaries and mature testes also revealed the presence of the Tesmin transcript in fetal ovaries as well as in fetal and adult heart. Time-course experiments showed that Tesmin was expressed in a characteristic development-related manner in fetal ovaries. Only a weak expression was observed at E12(1/2), the strongest signal was reached at E14(1/2), whereas the signal declined between E14(1/2) and E16(1/2). This transitional expression coincides with the early stages of the female meiotic prophase I. In the male, however, Tesmin was expressed in all stages of meiotic prophase I except preleptonema and leptonema. In situ hybridization further showed that the mRNA level increased during prophase I in the male, with the strongest expression seen at the transition from mid- to late pachytema (Stage VII-VIII). Furthermore, initiation of Tesmin transcription paralleled that of the synaptonemal complex protein 1 transcript (Scp1) in the fetal ovary and prepubertal testis. We, therefore, propose that Tesmin is likely to have a function in both the male and female meiotic prophase I. Moreover, the distinct difference in both the timing and the level of mRNA accumulation in the two gender's meiotic prophase I suggests that Tesmin transcription may be controlled by two different mechanisms during male and female meiosis. Mol. Reprod. Dev. 67: 116-126, 2004.

A gene recommender algorithm to identify coexpressed genes in C. elegans

One of the most important uses of whole-genome expression data is for the discovery of new genes with similar function to a given list of genes (the query) already known to have closely related function. We have developed an algorithm, called the gene recommender, that ranks genes according to how strongly they correlate with a set of query genes in those experiments for which the query genes are most strongly coregulated. We used the gene recommender to find other genes coexpressed with several sets of query genes, including genes known to function in the retinoblastoma complex. Genetic experiments confirmed that one gene (JC8.6) identified by the gene recommender acts with lin-35 Rb to regulate vulval cell fates, and that another gene (wrm-1) acts antagonistically. We find that the gene recommender returns lists of genes with better precision, for fixed levels of recall, than lists generated using the C. elegans expression topomap.

Native tesmin is a 60-kilodalton protein that undergoes dynamic changes in its localization during spermatogenesis in mice

Tesmin is a testis-specific protein. Four mouse tesmin cDNAs so far reported encode a testis-specific, metallothionein-like, 30-kDa protein (tesmin-30). An antibody against tesmin-30, however, detected a protein of 60 kDa (tesmin-60) from the mouse testis. To resolve the relationship between the two, the immunoprecipitated native tesmin-60 was sequenced. The result indicated that tesmin-30 is not full-length but is part of the C-terminal half of tesmin-60. The full-length cDNA (2.2 kilobases [kb]) encoding tesmin-60 (475 amino acid residues) and its genomic DNA (23 kb) were cloned and sequenced. A search of databases indicated that tesmin is a member of the CXC-hinge-CXC family. Immunohistochemistry indicated that tesmin exhibits dynamic subcellular localization changes during spermatogenesis. Before meiosis, it was localized in the cytoplasm of early to late spermatocytes and then translocated into the nucleus just before meiotic division. After meiosis, it appeared in spermatids, starting from the acrosomal vesicles, moving to the nuclear membrane and then to the caudal end as the spermatids elongated, and finally relocating into the cytoplasm. Oxidative stress by cobalt chloride, as well as by diethylmaleate, induced both premature translocation of tesmin from the cytoplasm to the nucleus and apoptotic signals in spermatocytes. The persistent existence of tesmin and its temporally and spatially dynamic localization suggest that tesmin is involved in multiple stages of spermatogenesis and spermiogenesis, possibly during sperm maturation and/or morphogenesis.