Cloning and characterization of a novel human TEKTIN1 gene

Sperm Motility Annotated Genes: Are They Associated with Impaired Fecundity?

Sperm motility is a prerequisite for achieving pregnancy, and alterations in sperm motility, along with sperm count and morphology, are commonly observed in subfertile men. The aim of the study was to determine whether the expression level of genes annotated with the Gene Ontology (GO) term 'sperm motility' differed in sperm collected from healthy men and men diagnosed with oligoasthenozoospermia. Reverse transcription quantitative real-time PCR (RT-qPCR), quantitative mass spectrometry (LC-MS/MS), and enrichment analyses were used to validate a set of 132 genes in 198 men present at an infertility clinic. Out of the 132 studied sperm-motility-associated genes, 114 showed differentially expressed levels in oligoasthenozoospermic men compared to those of normozoospermic controls using an RT-qPCR analysis. Of these, 94 genes showed a significantly lower expression level, and 20 genes showed a significantly higher expression level. An MS analysis of sperm from an independent cohort of healthy and subfertile men identified 692 differentially expressed proteins, of which 512 were significantly lower and 180 were significantly higher in oligoasthenozoospermic men compared to those of the normozoospermic controls. Of the 58 gene products quantified with both techniques, 48 (82.75%) showed concordant regulation. Besides the sperm-motility-associated proteins, the unbiased proteomics approach uncovered several novel proteins whose expression levels were specifically altered in abnormal sperm samples. Among these deregulated proteins, there was a clear overrepresentation of annotation terms related to sperm integrity, the cytoskeleton, and energy-related metabolism, as well as human phenotypes related to spermatogenesis and sperm-related abnormalities. These findings suggest that many of these proteins may serve as diagnostic markers of male infertility. Our study reveals an extended number of sperm-motility-associated genes with altered expression levels in the sperm of men with oligoasthenozoospermia. These genes and/or proteins can be used in the future for better assessments of male factor infertility.

Single-cell-resolution transcriptome map revealed novel genes involved in testicular germ cell progression and somatic cells specification in Chinese tongue sole with sex reversal

Female-to-male sex reversals (pseudomales) are common in lower vertebrates and have been found in natural populations, which is a concern under rapid changes in environmental conditions. Pseudomales can exhibit altered spermatogenesis. However, the regulatory mechanisms underlying pseudomale spermatogenesis remain unclear. Here, we characterized spermatogenesis in Chinese tongue sole (Cynoglossus semilaevis), a species with genetic and environmental sex determination, based on a high-resolution single-cell RNA-seq atlas of cells derived from the testes of genotypic males and pseudomales. We identified five germ cell types and six somatic cell types and obtained a single-cell atlas of dynamic changes in gene expression during spermatogenesis in Chinese tongue sole, including alterations in pseudomales. We detected decreased levels of Ca²⁺ signaling pathway-related genes in spermatogonia, insufficient meiotic initiation in spermatocytes, and a malfunction of somatic niche cells in pseudomales. However, a cluster of CaSR genes and MAPK signaling factors were upregulated in undifferentiated spermatogonia of pseudomales. Additionally, we revealed that Z chromosome-specific genes, such as piwil2, dhx37, and ehmt1, were important for spermatogenesis. These results improve our understanding of reproduction after female-to-male sex-reversal and provide new insights into the adaptability of reproductive strategies in lower vertebrates.

Hdh-Tektin-4 Regulates Motility of Fresh and Cryopreserved Sperm in Pacific Abalone, Haliotis discus hannai

As structural components of sperm, tektins are thought to play a fundamental role in sperm flagellar motility. In this study, Tektin-4 (Hdh-TEKT4) gene was successfully cloned and characterized from the testis tissue in Pacific abalone, Haliotis discus hannai. The full-length cDNA of Hdh-TEKT4 was 1,983 bp, with a coding region of 1,350 bp encoding 51.83 kDa putative protein of 449 deduced amino acids. Hdh-TEKT4 contains a tektin domain including a nonapeptide signature motif (RPGVDLCRD). Fluorescence in situ hybridization revealed that Hdh-TEKT4 localized in the spermatids of Pacific abalone testis. qRT-PCR analysis showed that Hdh-TEKT4 was predominantly expressed in testis tissues. Hdh-TEKT4 mRNA expression was upregulated during the fully mature testicular developmental stage in both seasonal development and EAT exposed abalone. Furthermore, mRNA expression of Hdh-TEKT4 was significantly higher in sperm with higher motility than in sperm with lower motility during peak breeding season, induced spawning activity stages, and after cryopreservation in different cryoprotectants. Taken together, these results indicate that the expression of Hdh-TEKT4 in Pacific abalone sperm might have a positive correlation with sperm motility.

Downregulation of KIF2C and TEKT2 is associated with male infertility and testicular carcinoma

Background: Genetic factors are important in spermatogenesis and fertility maintenance, and are potentially significant biomarkers for the early detection of infertility. However, further understanding of these biological processes is required.

Methods: In the present study, we sought to identify associated genes by reanalyzing separate studies from Gene Expression Omnibus datasets (GSE45885, GSE45887 and GSE9210) and validation datasets (GSE4797, 145467, 108886, 6872). The differential genes were used the limma package in R language. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed by the clusterprofier package. The protein-protein interaction network was constructed by the STRING database. The interaction between mRNA and TF was predicted by miRWalk web. At last, The Cancer Genome Atlas data were used to identify hub gene expression levels in GEPIA web.

Results: The results showed that 27 shared genes associated with spermatogenesis. We effectively screen out two genes (KIF2C and TEKT2) and both validated by GSE4797, 145467, 108886 and 6872. Among 27 shared genes, KIF2C and TEKT2 both down-regulated in spermatogenesis. The network of TF-miRNA-target gene was established, we found KIF2C-miRNAs (has-miR-3154, 6075, 6760-5p, 1251-5p, 186-sp)-TFs (EP300, SP1) might work in spermatogenesis.

Conclusions: Our study might help to improve our understanding of the mechanisms in spermatogenesis and provide diagnostic biomarkers and therapeutics targets.

Influence of cryopreservation on the CATSPER2 and TEKT2 expression levels and protein levels in human spermatozoa

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The cryopreservation process could lead to a reduction in the expression levels of the CATSPER2 and TEKT2 gene in human spermatozoa.

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The cryopreservation process could lead to a down-regulation in the expression of CATSPER2 and TEKT2 gene in human spermatozoa.

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The cryopreservation process could lead to a reduction in the level of CatSper 2 and Tektin 2 protein in human spermatozoa.

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The CatSper 2 and Tektin 2 may be used as markers to explain the causes of motility loss in the spermatozoa after the cryopreservation process.

This study designed to assess the expression level of CATSPER2 and TEKT2 and to evaluate the levels of CatSper2 and Tektin2 proteins in human spermatozoa before and after cryopreservation. One hundred and twenty semen samples were included in this study. All the samples were subjected to qPCR and Western blot analysis. The results showed a significant reduction in the expression levels of CATSPER2 and TEKT2 in the cryopreserved compared to the fresh samples (P = 0.0039 and P = 0.0166, respectively), and the results showed down-regulation in the expression level of CATSPER2 and TEKT2 genes between the study groups. Moreover, the protein levels of the CatSper2 and Tektin2 were lower in cryopreserved samples compared to fresh samples (P = 0.0001). In conclusion, the reduction in the proteins level and expression level of the CATSPER2 and TEKT2 in cryopreserved samples could be used as an indicator of sperm motility loss.

RNAi-Mediated Knockdown of Tssk1 and Tektin1 Genes Impair Male Fertility in Bactrocera dorsalis

The genetic-based sterile insect technique (SIT) is an effective and environmentally safe strategy to diminish populations of agricultural and horticultural insect pests. Functional characterization of genes related to male fertility can enhance the genetic-based SIT. Tssk1 has been involved to control male fertility in both mammals and insects. Moreover, Tektin1 has also been revealed to influence male fertility in both human and mammals. These findings suggested that Tssk1 and Tektin1 identified from Bactrocera dorsalis could be required for male fertility in B. dorsalis. In this study, expression profiles of these two genes were studied at different developmental stages and in various tissues of adult males. Remarkably, it was found that Tssk1 and Tektin1 were highly expressed in the testis of mature adult males of B. dorsalis. Furthermore, Tssk1 and Tektin1 genes were downregulated by using the RNA interference (RNAi) method. Fertility assays including egg laying, hatching, and spermatozoa count were also performed to investigate male fertility of B. dorsalis. Results showed that knockdown of Tssk1 and Tektin1 caused male sterility up to 58.99% and 64.49%, respectively. As expected, the total numbers of spermatozoa were also significantly reduced by 65.83% and 73.9%, respectively. These results suggested that male sterility was happened wing to the low number of spermatozoa. In conclusion, we demonstrate that Tssk1 and Tektin1 are the novel agents that could be used to enhance the genetic-based SIT, or their double-stranded RNA (dsRNA) can be used as biopesticides to control the population of B. dorsalis.

Translocation of Tektin 3 to the equatorial segment of heads in bull spermatozoa exposed to dibutyryl cAMP and calyculin A

Tektins (TEKTs) are filamentous proteins associated with microtubules in cilia, flagella, basal bodies, and centrioles. Five TEKTs (TEKT1, -2, -3, -4, and -5) have been identified as components of mammalian sperm flagella. We previously reported that TKET1 and -3 are also present in the heads of rodent spermatozoa. The present study clearly demonstrates that TEKT2 is present at the acrosome cap whereas TEKT3 resides just beneath the plasma membrane of the post-acrosomal region of sperm heads in unactivated bull spermatozoa, and builds on the distributional differences of TEKT1, -2, and -3 on sperm heads. We also discovered that hyperactivation of bull spermatozoa by cell-permeable cAMP and calyculin A, a protein phosphatase inhibitor, promoted translocation of TEKT3 from the post-acrosomal region to the equatorial segment in sperm heads, and that TEKT3 accumulated at the equatorial segment is lost upon acrosome reaction. Thus, translocation of TEKT3 to the equatorial segment may be a capacitation- or hyperactivation-associated phenomenon in bull spermatozoa. Mol. Reprod. Dev. 84: 30-43, 2017. © 2016 Wiley Periodicals, Inc.

Identification and characterization of a bovine sperm acrosomal matrix protein and its mechanism of interaction with acrosomal hydrolases

Fertilization, the union of male and female gametes to create offspring, is an intricate biological process dependent upon several biochemical and physiological events. Our understanding of the functions of protein constituents of the outer acrosomal membrane-associated matrix complex (OMC) is limited. A highly purified OMC fraction isolated from bovine cauda sperm heads comprised 54, 50, 45, and 38-19 kDa polypeptides. The objective of this study is to identify and characterize the 45 kDa (OMC45) polypeptide, to define its role in binding acrosomal hydrolases, and to examine the fate of OMC45 polypeptide during the acrosome reaction. We isolated OMC45 polypeptide from the high-pH insoluble fraction of OMC. Proteomic analysis of OMC45 by MALDI-TOF-TOF yielded eight peptides that matched the NCBI database sequence of Tektin 3 (TEKT3). Triton X-100-permeabilized cauda sperm exhibited intense staining of the acrosomal segment with anti-OMC45 and anti-TEKT3. The OMC45 polypeptide was solubilized by radio-immunoprecipitation assay buffer extraction. The solubilized fraction was subjected to immunoprecipitation analysis. The OMC45 polypeptide was recovered in the anti-OMC45 immunoprecipitation pellet. An identical blot stained with anti-TEKT3 exhibited the presence of TEKT3 polypeptide in the anti-OMC45 pellet. Our immunofluorescence and biochemical studies confirm the proteomics identification of OMC45 polypeptide and that it exhibits a sequence similarity to TEKT3. OMC45 glycoprotein possesses both N-linked and O-linked oligosaccharides. Deglycosylated OMC45 revealed a significant reduction in both acrosin and N-acetylglucosaminidase (NAGA) binding in comparison with acrosin and NAGA binding to a native OMC45 polypeptide, demonstrating the important role of oligosaccharides in hydrolase binding. OMC45 polypeptide is not released during the acrosome reaction but remains in the particulate cell subfraction, associated with the hybrid membrane complex.

Effect of BMP4 preceded by retinoic acid and co-culturing ovarian somatic cells on differentiation of mouse embryonic stem cells into oocyte-like cells

Bone morphogenetic protein 4 (BMP4) and retinoic acid (RA) signaling are the key regulators for germ cell and meiosis induction, respectively. Gonadal tissue also provides an appropriate microenvironment for oocyte differentiation in vivo. The current study aimed to determine whether mimicking in vivo niche is more efficient for oocyte differentiation from embryonic stem (ES) cells. Here, differentiation of mouse ES cells toward oocyte-like cells using embryoid body (EB) and monolayer protocols was induced in the presence (+BMP4) or absence (-BMP4) of BMP4. On day 5, each group was co-cultured with ovarian somatic cells in the presence or absence of RA (+RA or -RA) for an additional 14 days. Our results showed a significant increase in expression of meiotic markers in the +BMP4 condition in EB differentiation protocol. Further differentiation with ovarian somatic cells led to a subpopulation of oocyte-like cell formation. Compared to the controls, the +RA condition resulted in a significant elevation of the meiotic gene expression in contrast to Oct4 that significantly decreased in both protocols. In the cells pre-treated with BMP4 and then exposed to RA in the monolayer differentiation protocol, the gene expression levels of germ cell, Mvh, and maturation markers, Cx37, Zp2, and Gdf9, were also upregulated significantly. Therefore, it can be concluded that +BMP4 and +RA along with ovarian somatic cell co-culture improved the rate of in vitro oocyte differentiation.

Identification of proteins involved in human sperm motility using high-throughput differential proteomics

Mammalian sperm motility is a prerequisite for in vivo fertilization, and alterations in this parameter are commonly observed in infertile males. However, we still do not have a complete understanding of the molecular mechanisms controlling it. The aim of this study was to identify proteins involved in human sperm motility deficiency by using TMT protein labeling and LC-MS/MS. Two complementary approaches were used: comparison between sperm samples differing in motility (asthenozoospermic versus normozoospermic) and comparison between sperm subpopulations of fractionated normozoospermic samples differing in motility (non-migrated versus migrated). LC-MS/MS resulted in the identification of 1157 and 887 proteins in the first and second approaches, respectively. Remarkably, similar proteomic alterations were detected in the two experiments, with 80 proteins differentially expressed in the two groups of samples and 93 differentially expressed in the two groups of subpopulations. The differential proteins were analyzed by GO, cellular pathways, and clustering analyses and resulted in the identification of core deregulated proteins and pathways associated with sperm motility dysfunction. These included proteins associated with energetic metabolism, protein folding/degradation, vesicle trafficking, and the cytoskeleton. Contrary to what is usually accepted, the outcomes support the hypothesis that several metabolic pathways (notably, mitochondrial-related ones) contribute toward regulating sperm motility.

Molecular cloning and subcellular localization of Tektin2-binding protein 1 (Ccdc 172) in rat spermatozoa

Tektins (TEKTs) are composed of a family of filament-forming proteins localized in cilia and flagella. Five types of mammalian TEKTs have been reported, all of which have been verified to be present in sperm flagella. TEKT2, which is indispensable for sperm structure, mobility, and fertilization, was present at the periphery of the outer dense fiber (ODF) in the sperm flagella. By yeast two-hybrid screening, we intended to isolate flagellar proteins that could interact with TEKT2, which resulted in the isolation of novel two genes from the mouse testis library, referred as a TEKT2-binding protein 1 (TEKT2BP1) and -protein 2 (TEKT2BP2). In this study, we characterized TEKT2BP1, which is registered as a coiled-coil domain-containing protein 172 (Ccdc172) in the latest database. RT-PCR analysis indicated that TEKT2BP1 was predominantly expressed in rat testis and that its expression was increased after 3 weeks of postnatal development. Immunocytochemical studies discovered that TEKT2BP1 localized in the middle piece of rat spermatozoa, predominantly concentrated at the mitochondria sheath of the flagella. We hypothesize that the TEKT2-TEKT2BP1 complex might be involved in the structural linkage between the ODF and mitochondria in the middle piece of the sperm flagella.

Serological identification of Tektin5 as a cancer/testis antigen and its immunogenicity

Background

Identification of new cancer antigens is necessary for the efficient diagnosis and immunotherapy. A variety of tumor antigens have been identified by several methodologies. Among those antigens, cancer/testis (CT) antigens have became promising targets.

Methods

The serological identification of antigens by the recombinant expression cloning (SEREX) methodology has been successfully used for the identification of cancer/testis (CT) antigens. We performed the SEREX analysis of colon cancer.

Results

We isolated a total of 60 positive cDNA clones comprising 38 different genes. They included 2 genes with testis-specific expression profiles in the UniGene database, such as TEKT5 and a CT-like gene, A kinase anchoring protein 3 (AKAP3). Quantitative real-time RT-PCR analysis showed that the expression of TEKT5 was restricted to the testis in normal adult tissues. In malignant tissues, TEKT5 was aberrantly expressed in a variety of cancers, including colon cancer. A serological survey of 101 cancer patients with different cancers by ELISA revealed antibodies to TEKT5 in 13 patients, including colon cancer. None of the 16 healthy donor serum samples were reactive in the same test.

Conclusion

We identified candidate new CT antigen of colon cancer, TEKT5. The findings indicate that TEKT5 is immunogenic in humans, and suggest its potential use as diagnostic as well as an immunotherapeutic reagent for cancer patients.

Subcellular localization of Tektin2 in rat sperm flagellum

Tektins are evolutionarily conserved filament-forming proteins localized in flagella and cilia, and have been reported to be involved in the stability and structural complexity of axonemal microtubules. Five mammalian Tektins (Tektin1-5) have been reported. Of these, Tektin2 (TEKT2) has been found to be required for normal flagellum structure and function. Tekt2-null sperm display flagellum bending and reduced motility, probably due to disruption of the dynein inner arm. However, the subcellular localization of TEKT2 in spermatozoa has not been clarified at the ultrastructural level. To elucidate the molecular localization of TEKT2 in flagella of rat spermatozoa, we performed confocal laser scanning microscopy, extraction of flagella followed by immunoblot analysis, and immunogold electron microscopy. Extraction of sperm flagella by SDS-EDTA resulted in complete extraction of axonemal tubulins, while TEKT2 was only partially released from flagella, suggesting that TEKT2 might be present in the peri-axonemal component, not directly associated with axonemal tubulins. Confocal laser scanning microscopy and pre-embedding immunoelectron microscopy revealed that TEKT2 is associated with the surface of outer dense fibers (ODFs). TEKT2 may function as an ODF-affiliated molecule required for flagellum stability and sperm motility.

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.

Characterization of Spetex-1, a new component of satellite fibrils associated with outer dense fibers in the middle piece of rodent sperm flagella

Spetex-1, which has been isolated by differential display as a haploid spermatid-specific gene, encodes a protein with two coiled-coil motifs located in the middle piece of flagella in rodent spermatozoa. The middle piece of flagella is composed of axoneme and peri-axonemal elements including outer dense fibers (ODFs) and satellite fibrils. Pre-embedding immunoelectron microscopy clearly demonstrated that Spetex-1 is located at satellite fibrils associated with ODFs in the middle piece of flagella of rat spermatozoa. Extraction of Spetex-1 from spermatozoa by SDS or urea required dithiothreitol, suggesting crosslinking by disulfide bond is involved in the assembly of satellite fibrils containing Spetex-1. We identified putative Spetex-1 orthologs in many animal species, and both cysteine residues and coiled-coil motifs were well conserved in mammalian orthologs of Spetex-1. When Spetex-1 was co-transfected into COS-7 cells with myc-tagged Tektin4, another filamentous protein associated with ODFs, the two molecules were co-localized in various sizes of aggregates in the cells. These data suggested that Spetex-1, a new component of satellite fibrils, might be involved in the structural stability of the sperm flagellar middle piece and functions in co-operation with Tektin4.

Male infertility caused by spermiogenic defects: lessons from gene knockouts

Spermiogenesis refers to the process by which postmeiotic spermatids differentiate into elongated spermatids and eventually spermatozoa. During spermiogenesis, round spermatids undergo dynamic morphologic changes, which include nuclear condensation and elongation, formation of flagella and acrosome, reorganization of organelles and elimination of cytoplasm upon spermiation. This cellular differentiation process is unique to male haploid germ cells, which may explain why approximately half of the testis-specific genes are exclusively expressed in spermiogenesis. The spermiogenesis-specific expression implies that these genes contribute to either structural or functional aspects of future sperm. Many such genes have been inactivated in mice and some of these gene knockout mice display male infertility due to nonfunctional sperm which display no or various degrees of structural abnormalities. Since the majority of these spermiogenesis-specific genes are highly conserved between mice and humans, findings from knockout mouse studies may be applicable to human infertility. Here, I briefly review some of these spermatid-specific gene knockouts. The mouse studies strongly suggest that sperm quality rather than quantity is a better indicator of male fertility and novel assays should be developed to determine sperm functionality.

In vitro germ cell differentiation from cynomolgus monkey embryonic stem cells

Background

Mouse embryonic stem (ES) cells can differentiate into female and male germ cells in vitro. Primate ES cells can also differentiate into immature germ cells in vitro. However, little is known about the differentiation markers and culture conditions for in vitro germ cell differentiation from ES cells in primates. Monkey ES cells are thus considered to be a useful model to study primate gametogenesis in vitro. Therefore, in order to obtain further information on germ cell differentiation from primate ES cells, this study examined the ability of cynomolgus monkey ES cells to differentiate into germ cells in vitro.

Methods and Findings

To explore the differentiation markers for detecting germ cells differentiated from ES cells, the expression of various germ cell marker genes was examined in tissues and ES cells of the cynomolgus monkey (Macaca fascicularis). VASA is a valuable gene for the detection of germ cells differentiated from ES cells. An increase of VASA expression was observed when differentiation was induced in ES cells via embryoid body (EB) formation. In addition, the expression of other germ cell markers, such as NANOS and PIWIL1 genes, was also up-regulated as the EB differentiation progressed. Immunocytochemistry identified the cells expressing stage-specific embryonic antigen (SSEA) 1, OCT-4, and VASA proteins in the EBs. These cells were detected in the peripheral region of the EBs as specific cell populations, such as SSEA1-positive, OCT-4-positive cells, OCT-4-positive, VASA-positive cells, and OCT-4-negative, VASA-positive cells. Thereafter, the effect of mouse gonadal cell-conditioned medium and growth factors on germ cell differentiation from monkey ES cells was examined, and this revealed that the addition of BMP4 to differentiating ES cells increased the expression of SCP1, a meiotic marker gene.

Conclusion

VASA is a valuable gene for the detection of germ cells differentiated from ES cells in monkeys, and the identification and characterization of germ cells derived from ES cells are possible by using reported germ cell markers in vivo, including SSEA1, OCT-4, and VASA, in vitro as well as in vivo. These findings are thus considered to help elucidate the germ cell developmental process in primates.

The tektin family of microtubule-stabilizing proteins

Tektins are insoluble a-helical proteins essential for the construction of cilia and flagella and are found throughout the eukaryotes apart from higher plants.

Transcriptomic analyses reveal novel genes with sexually dimorphic expression in the zebrafish gonad and brain

BACKGROUND

Our knowledge on zebrafish reproduction is very limited. We generated a gonad-derived cDNA microarray from zebrafish and used it to analyze large-scale gene expression profiles in adult gonads and other organs.

METHODOLOGY/PRINCIPAL FINDINGS

We have identified 116638 gonad-derived zebrafish expressed sequence tags (ESTs), 21% of which were isolated in our lab. Following in silico normalization, we constructed a gonad-derived microarray comprising 6370 unique, full-length cDNAs from differentiating and adult gonads. Labeled targets from adult gonad, brain, kidney and 'rest-of-body' from both sexes were hybridized onto the microarray. Our analyses revealed 1366, 881 and 656 differentially expressed transcripts (34.7% novel) that showed highest expression in ovary, testis and both gonads respectively. Hierarchical clustering showed correlation of the two gonadal transcriptomes and their similarities to those of the brains. In addition, we have identified 276 genes showing sexually dimorphic expression both between the brains and between the gonads. By in situ hybridization, we showed that the gonadal transcripts with the strongest array signal intensities were germline-expressed. We found that five members of the GTP-binding septin gene family, from which only one member (septin 4) has previously been implicated in reproduction in mice, were all strongly expressed in the gonads.

CONCLUSIONS/SIGNIFICANCE

We have generated a gonad-derived zebrafish cDNA microarray and demonstrated its usefulness in identifying genes with sexually dimorphic co-expression in both the gonads and the brains. We have also provided the first evidence of large-scale differential gene expression between female and male brains of a teleost. Our microarray would be useful for studying gonad development, differentiation and function not only in zebrafish but also in related teleosts via cross-species hybridizations. Since several genes have been shown to play similar roles in gonadogenesis in zebrafish and other vertebrates, our array may even provide information on genetic disorders affecting gonadal phenotypes and fertility in mammals.

A possible association of a human tektin-t gene mutation (A229V) with isolated non-syndromic asthenozoospermia: case report

Asthenozoospermia (AZS), characterized by grade A + B sperm motility (as in World Health Organization Guidelines) < or =50% or A <25% in fresh ejaculate, may exist as an isolated disorder, in combination with other sperm anomalies or as part of syndromic association. The majority of syndromic patients can be ascribed to mutations in dynein genes, while, to date, no genes have been described to be associated in humans with non-syndromic, isolated AZS. An interesting family of axonemal proteins, the tektins, has been recently identified in various mammals and they are thought to play a fundamental role in ciliary movement. Recently, the human tektin-t (or h-tekB1 or Tektin-2) gene has been cloned, showing specific expression in flagella of mature sperm. We report the screening of tektin-t gene in 90 isolated non-syndromic AZS patients. We found a heterozygous mutation (A229V) in one patient. Ultrastructural analysis showed anomalies in > or =80% of examined spermatozoa involving axoneme microtubules and mitochondria. Moreover, the viability and mitochondrial function of sperm were altered in the patient with the A229V mutation. This is the first description of human pathology linked to a tektin-family gene, since only murine models are available for these genes.

Integrative characterization of germ cell-specific genes from mouse spermatocyte UniGene library

Background

The primary regulator of spermatogenesis, a highly ordered and tightly regulated developmental process, is an intrinsic genetic program involving male germ cell-specific genes.

Results

We analyzed the mouse spermatocyte UniGene library containing 2155 gene-oriented transcript clusters. We predict that 11% of these genes are testis-specific and systematically identified 24 authentic genes specifically and abundantly expressed in the testis via in silico and in vitro approaches. Northern blot analysis disclosed various transcript characteristics, such as expression level, size and the presence of isoform. Expression analysis revealed developmentally regulated and stage-specific expression patterns in all of the genes. We further analyzed the genes at the protein and cellular levels. Transfection assays performed using GC-2 cells provided information on the cellular characteristics of the gene products. In addition, antibodies were generated against proteins encoded by some of the genes to facilitate their identification and characterization in spermatogenic cells and sperm. Our data suggest that a number of the gene products are implicated in transcriptional regulation, nuclear integrity, sperm structure and motility, and fertilization. In particular, we found for the first time that Mm.333010, predicted to contain a trypsin-like serine protease domain, is a sperm acrosomal protein.

Conclusion

We identify 24 authentic genes with spermatogenic cell-specific expression, and provide comprehensive information about the genes. Our findings establish a new basis for future investigation into molecular mechanisms underlying male reproduction.

Spetex-1: a new component in the middle piece of flagellum in rodent spermatozoa

Spetex-1 has recently been isolated by differential display and screening of cDNA library. It encodes a protein of 556 amino acid residues possessing coiled-coil motifs. In the rat seminiferous tubules (ST), Spetex-1 was expressed in the cytoplasm of elongating spermatids. To examine the subcellular distribution of Spetex-1 in mature spermatozoa, we performed biochemical and immunocytochemical approaches. We found that Spetex-1 that was synthesized in the cytoplasm of elongating spermatids was subsequently integrated as a middle piece component into spermatozoa during spermiogenesis. After integration, the majority of Spetex-1 in spermatozoa could be extracted by 6M urea under reduced condition but not released by the treatment of 1% Triton X-100. Immunoelectron microscopy demonstrated that Spetex-1 seemed to locate at the inner side of outer dense fibers (ODFs) in the middle piece or the narrow space between ODFs and axoneme. Spetex-1 might be involved in the stability of the structural complexity comprising axoneme and ODFs in the middle piece of sperm flagellum.

Tektin 4 is located on outer dense fibers, not associated with axonemal tubulins of flagella in rodent spermatozoa

Tektins, which are thought to be the constitutive proteins of microtubules in cilia, flagella, basal bodies, and centrioles, have been reported to be involved in the stability and structural complexity of axonemal microtubules. Four types of mammalian Tektins have been reported, and at least two types of Tektins, Tektin 2 and Tektin 4, have been verified to be present in sperm flagella. To elucidate the molecular localization of Tektin 4 in flagella of rodent spermatozoa, we performed immunocytochemistry, fractionation study followed by immunoblot analysis, and immunogold electron microscopy. Confocal laser scanning microscopy and immunogold electron microscopy indicated that Tektin 4 was associated with outer dense fibers (ODFs) in both the middle and principal piece of flagella in rat and mouse spermatozoa. Tektin 4 in rat spermatozoa is completely released by 6 M urea treatment, but not extracted by 1% Triton X-100 and 0.6 M potassium thiocyanate. Pre-embedding immunoelectron microscopy demonstrated that Tektin 4 located on the abaxial (convex) surface of ODFs in flagella, not associate with axonemal microtubules. Our data strongly suggested that Tektin 4 is not associated with axonemal tubulins but an ODFs-affiliated molecule in rodent spermatozoa.

Molecular cloning of a new member of TEKTIN family, Tektin4, located to the flagella of rat spermatozoa

Tektins are composed of a family of filament-forming proteins associated with ciliary and flagellar microtubules. A new member of the TEKTIN gene family, which was designated as rat Tektin4, was obtained by PCR technique combined with yeast two-hybrid screening. Rat Tektin4 cDNA consists of 1,341 bp encoding a 52 kDa protein of 447 amino acids. Tektin4 protein contains a Tektin domain including a nonapeptide signature sequence (RPNVELCRD), which is a prominent feature of Tektins. Its amino acid sequence showed 29% approximately 58% identities to that of other Tektin family proteins registered in the public databases. Tektin4 gene, which was mapped to rat chromosome 10q12, is composed of six exons and spanning 5 kb. Reverse-transcriptional-PCR (RT-PCR) analysis indicated that Tektin4 was predominantly expressed in testis and its expression was upregulated during testis development. In situ hybridization analysis showed that Tektin4 mRNA was localized in round spermatids in the seminiferous tubules of the rat testis. Tektin4 protein was predominantly localized in the flagella of spermatozoa, suggesting that it might works as a flagellar component requisite for flagellar stability or sperm motility.

Mice deficient in the axonemal protein Tektin-t exhibit male infertility and immotile-cilium syndrome due to impaired inner arm dynein function

The haploid germ cell-specific Tektin-t protein is a member of the Tektin family of proteins that form filaments in flagellar, ciliary, and axonemal microtubules. To investigate the physiological role of Tektin-t, we generated mice with a mutation in the tektin-t gene. The homozygous mutant males were infertile, while the females were fully fertile. Sperm morphology and function were abnormal, with frequent bending of the sperm flagella and marked defects in motility. In vitro fertilization assays showed that the defective spermatozoa were able to fertilize eggs. Electron microscopic examination showed that the dynein inner arm structure was disrupted in the sperm flagella of tektin-t-deficient mice. Furthermore, homozygous mutant mice had functionally defective tracheal cilia, as evidenced by altered dynein arm morphology. These results indicate that Tektin-t participates in dynein inner arm formation or attachment and that the loss of Tektin-t results in impaired motility of both flagella and cilia. Therefore, the tektin-t gene is one of the causal genes for immotile-cilium syndrome/primary ciliary dyskinesia.

Characterization of ciliated bronchial epithelium 1, a ciliated cell-associated gene induced during mucociliary differentiation

Lung epithelial structure is altered in asthma; however, the precise mechanisms underlying epithelial repair, including differentiation from basal to columnar epithelial cells, are not well defined. In the course of random sequencing of a cDNA library from human lung biopsies, we have identified a novel gene, ciliated bronchial epithelium 1 (CBE1). Expression of CBE1 was induced during in vitro differentiation of bronchial epithelial cells. Synchronous expression with tektin and hepatocyte nuclear factor 3/forkhead homologue 4, down-regulation by interleukin-13, and its tissue distribution strongly suggested that CBE1 is associated with ciliated cells. Two isoforms of the 0.7-kb full-length cDNA were identified, resulting in open reading frames with different carboxyl termini, with no homology to known proteins. Expression of CBE1 in ciliated epithelial cells was confirmed by immunohistochemistry. Quantitative reverse transcription-polymerase chain reaction analysis using bronchial biopsies showed no difference of expression of CBE1 between normal subjects and subjects with asthma. Expression studies showed that CBE1 is nuclear- or perinuclear-localized, depending on cell type. Regulated expression during differentiation and the subcellular localization of CBE1 suggest that it may play an important role in the differentiation and/or function of ciliated cells in human airways.