A Cre gene directed by a human TSPY promoter is specific for germ cells and neurons

Ovotesticular cords and ovotesticular follicles: New histologic markers for human ovotesticular syndrome

INTRODUCTION

The presence of an ovotestis is a rare difference of sex development. The diagnosis can be difficult with the gold standard being the presence of both testicular cords and ovarian follicles within the same gonad.

OBJECTIVE

Herein we describe two new markers of ovotesticular syndrome: ovotesticular cords and ovotesticular follicles.

STUDY DESIGN

Twenty human gonads with a previous diagnosis of ovotestis were re-stained with markers for testicular cords (SOX9, TSPY, SALL4, DDX4, cP450, AR, α-actin) and ovarian tissue (FOXL2, SALL4, DDX4). Ovotesticular cords were defined as structures expressing both testicular Sertoli cell marker (SOX9) and an ovarian follicular cell marker (FOXL2), and in Y chromosome positive specimens, TSPY-positive testicular germ cells. Ovotesticular follicles were defined as a hybrid ovarian follicle containing FOXL2-positive granulosa cells and a central oocyte, but also containing cells expressing the testicular Sertoli cell marker, SOX9, intermingled within FOXL2-positive granulosa cells and male and female germ cells.

RESULTS

Six of twenty ovotestis did not meet our criterion for the diagnosis of ovotestis lacking the histologic evidence of both testicular and ovarian tissue. The remaining 13 patients in which 14 separate specimens were evaluated, contained ovotestis defined by the presence of testicular cords and ovarian follicles. Eleven of the 14 ovotestis specimens (79 %) contained ovotesticular cords. Four of 11 ovotestis specimens (36 %) contained ovotesticular follicles.

DISCUSSION

We recommend using eight immunohistochemical markers to diagnose an ovotestis: 1) SOX9, TSPY, SALL4, DDX4, cytochrome P450, AR, smooth muscle α-actin for the testicular component and FOXL2 and SALL4, DDX4 for the ovarian component. SOX9 and TSPY (useful only in the presence of a Y karyotype) are specific testicular markers and FOXL2 the only specific ovarian marker. We found ovotesticular cords and ovotesticular follicles in both human bipolar and mixed ovotestis specimens both with and without the presence of the Y chromosome. The clinical significance of ovotesticular cords and follicles remains unknown. We did not observe any obvious abnormalities in cellular architecture with the juxtaposition of testicular cells and ovarian cells.

CONCLUSION

We have identified two new structures in humans with ovotestis, ovotesticular cords and ovotesticular follicles (Figure), which appears to be additional markers to facilitate the diagnosis of ovotesticular gonads.

Unlocking Genetic Mysteries during the Epic Sperm Journey toward Fertilization: Further Expanding Cre Mouse Lines

The spatiotemporal expression patterns of genes are crucial for maintaining normal physiological functions in animals. Conditional gene knockout using the cyclization recombination enzyme (Cre)/locus of crossover of P1 (Cre/LoxP) strategy has been extensively employed for functional assays at specific tissue or developmental stages. This approach aids in uncovering the associations between phenotypes and gene regulation while minimizing interference among distinct tissues. Various Cre-engineered mouse models have been utilized in the male reproductive system, including Dppa3-MERCre for primordial germ cells, Ddx4-Cre and Stra8-Cre for spermatogonia, Prm1-Cre and Acrv1-iCre for haploid spermatids, Cyp17a1-iCre for the Leydig cell, Sox9-Cre for the Sertoli cell, and Lcn5/8/9-Cre for differentiated segments of the epididymis. Notably, the specificity and functioning stage of Cre recombinases vary, and the efficiency of recombination driven by Cre depends on endogenous promoters with different sequences as well as the constructed Cre vectors, even when controlled by an identical promoter. Cre mouse models generated via traditional recombination or CRISPR/Cas9 also exhibit distinct knockout properties. This review focuses on Cre-engineered mouse models applied to the male reproductive system, including Cre-targeting strategies, mouse model screening, and practical challenges encountered, particularly with novel mouse strains over the past decade. It aims to provide valuable references for studies conducted on the male reproductive system.

Generation and Characterization of a Transgenic Mouse That Specifically Expresses the Cre Recombinase in Spermatids

Spermiogenesis is the step during which post-meiotic cells, called spermatids, undergo numerous morphological changes and differentiate into spermatozoa. Thousands of genes have been described to be expressed at this stage and could contribute to spermatid differentiation. Genetically-engineered mouse models using Cre/LoxP or CrispR/Cas9 are the favored approaches to characterize gene function and better understand the genetic basis of male infertility. In the present study, we produced a new spermatid-specific Cre transgenic mouse line, in which the improved iCre recombinase is expressed under the control of the acrosomal vesicle protein 1 gene promoter (Acrv1-iCre). We show that Cre protein expression is restricted to the testis and only detected in round spermatids of stage V to VIII seminiferous tubules. The Acrv1-iCre line can conditionally knockout a gene during spermiogenesis with a > 95% efficiency. Therefore, it could be useful to unravel the function of genes during the late stage of spermatogenesis, but it can also be used to produce an embryo with a paternally deleted allele without causing early spermatogenesis defects.

Development of the human ovary: Fetal through pubertal ovarian morphology, folliculogenesis and expression of cellular differentiation markers

A definition of normal human fetal and early postnatal ovarian development is critical to the ability to accurately diagnose the presence or absence of functional ovarian tissue in clinical specimens. Through assembling an extensive histologic and immunohistochemical developmental ontogeny of human ovarian specimens from 8 weeks of gestation through 16 years of postnatal, we present a comprehensive immunohistochemical mapping of normal protein expression patterns in the early fetal through post-pubertal human ovary and detail a specific expression-based definition of the early stages of follicular development. Normal fetal and postnatal ovarian tissue is defined by the presence of follicular structures and characteristic immunohistochemical staining patterns, including granulosa cells expressing Forkhead Box Protein L2 (FOXL2). However, the current standard array of immunohistochemical markers poorly defines ovarian stromal tissue, and additional work is needed to identify new markers to advance our ability to accurately identify ovarian stromal components in gonadal specimens from patients with disorders of sexual differentiation.

A model to study human ovotesticular syndrome

Ovotesticular syndrome is a rare disorder of sex development characterized by the presence of testicular and ovarian tissue. The histologic characteristics of human testicular tissue are well defined by the presence of seminiferous cords or tubules containing TSPY-positive germ cells and Sox9-positive Sertoli cells surrounded by interstitial tissue containing cytochrome P450-positive Leydig cells and smooth muscle α-actin-positive peritubular myoid cells. The histological characteristics of the ovary can be defined by germ cell nests and the development of follicles. In contrast to the testis, the ovary has a paucity of defined specific protein markers, with the granulosa cell marker FOXL2 being the most widely used. In practice, defining the ovarian component of the ovotestis can be quite difficult. We developed a model of human ovotesticular syndrome by combining fetal human testis and ovary in a xenograft model. Ovotesticular xenografts were grown under the renal capsules of gonadectomized athymic nude mice for 6-32 weeks along with age matched control grafts of fetal testis and ovary. Forty ovotesticular xenografts and their controls were analyzed by histology, immunohistochemistry, and fluorescent in situ hybridization to determine the protein expression and karyotype of the cells within the grafts. The ovotesticular xenografts exhibited recognizable testicular and ovarian tissue based on testis-specific and ovary-specific markers defined above. The xenografts simulated a bipolar ovotestis in which the testicular and ovarian elements retain their separate histological characteristics and are separated by a well-defined border. This contrasts with the compartmentalized ovotestis previously described in the literature where the testicular tissue is surrounded by ovarian tissue or a mixed histology where testicular and ovarian tissues are interspersed throughout the gonad. In conclusion, we have characterized a human model of ovotestis which will allow a deeper understanding of ovotestis development in humans and facilitate a more accurate diagnosis of the ovotesticular syndrome.

Comparison of Y-chromosome-linked TSPY, TSPY2, and PRAMEY genes in Taurus cattle, yaks, and interspecific hybrid bulls

Domestic yaks (Bos grunniens) and domestic Taurus cattle (Bos taurus) are closely related. An interesting phenomenon in interspecific crossings is male sterility in the F₁ hybrid (yattle) and F₂ backcross, with no late meiotic cells or spermatids in the seminiferous tubules. The mammalian Y chromosome is crucial for spermatogenesis and male fertility. This study investigated the copy number variations and mRNA of Y-transitional region genes TSPY2 (testis specific protein, Y-linked 2 and testis-specific Y-encoded protein 3-like) and PRAMEY (preferentially expressed antigen in melanoma, Y-linked), and Y-ampliconic region genes TSPY (testis-specific Y-encoded protein 1-like), ZNF280BY (zinc finger protein 280B, Y-linked) and HSFY (heat-shock transcription factor, Y-linked) in mature testes from Taurus cattle, yaks, and yattle. Phylogenetic trees divided 33 copies of TSPY into major 2 types (TSPY-T1 and TSPY-T2), 19 copies of TSPY2 into 2 types (TSPY2-T1 and T2), and 8 copies of PRAMEY into 4 types (PRAMEY-T1 to T4). Searching by the Basic Local Alignment Search Tool of the TSPY2 coding sequences in GenBank revealed that TSPY2 was conserved in Bovidae. The TSPY2-T2 sequences were absent, whereas PRAMEY-T2 and PRAMEY-T4 were amplified on the yak Y chromosome. The average copy numbers of TSPY-T2 and ZNF280BY were significantly different between cattle and yaks. The TSPY-T2, TSPY2, PRAMEY, ZNF280BY, and HSFY genes were uniquely or predominantly expressed in testes. Reverse-transcription quantitative PCR showed that the TSPY-T2, PRAMEY-T2, HSFY, ZNF280BY, protamine 1 (PRM1), and protamine 2 (PRM2) genes were almost not expressed in yattle. The PRM1 and PRM2 genes are used as positive markers for spermatozoa. Thus, our results showed that the genomic structure of the Y-transitional and Y-ampliconic region differed between Taurus cattle and yaks. Dysregulated expression of Y-ampliconic region genes TSPY-T2, HSPY, ZNF280BY, and Y-transitional region gene PRAMEY-T2 may be associated with hybrid male sterility in yattle.

Battle of the sexes: contrasting roles of testis-specific protein Y-encoded (TSPY) and TSPX in human oncogenesis

The Y-located testis-specific protein Y-encoded (TSPY) and its X-homologue TSPX originated from the same ancestral gene, but act as a proto-oncogene and a tumor suppressor gene, respectively. TSPY has specialized in male-specific functions, while TSPX has assumed the functions of the ancestral gene. Both TSPY and TSPX harbor a conserved SET/NAP domain, but are divergent at flanking structures. Specifically, TSPX contains a C-terminal acidic domain, absent in TSPY. They possess contrasting properties, in which TSPY and TSPX, respectively, accelerate and arrest cell proliferation, stimulate and inhibit cyclin B-CDK1 phosphorylation activities, have no effect and promote proteosomal degradation of the viral HBx oncoprotein, and exacerbate and repress androgen receptor (AR) and constitutively active AR variant, such as AR-V7, gene transactivation. The inhibitory domain has been mapped to the carboxyl acidic domain in TSPX, truncation of which results in an abbreviated TSPX exerting positive actions as TSPY. Transposition of the acidic domain to the C-terminus of TSPY results in an inhibitory protein as intact TSPX. Hence, genomic mutations/aberrant splicing events could generate TSPX proteins with truncated acidic domain and oncogenic properties as those for TSPY. Further, TSPY is upregulated by AR and AR-V7 in ligand-dependent and ligand-independent manners, respectively, suggesting the existence of a positive feedback loop between a Y-located proto-oncogene and male sex hormone/receptors, thereby amplifying the respective male oncogenic actions in human cancers and diseases. TSPX counteracts such positive feedback loop. Hence, TSPY and TSPX are homologues on the sex chromosomes that function at the two extremes of the human oncogenic spectrum.

The Y-linked proto-oncogene TSPY contributes to poor prognosis of the male hepatocellular carcinoma patients by promoting the pro-oncogenic and suppressing the anti-oncogenic gene expression

Background

Liver cancer is one of the major causes of cancer death worldwide, with significantly higher incidence and mortality among the male patients. Although sex hormones and their receptors could contribute to such sex differences, the story is incomplete. Genes on the male-specific region of the Y chromosome could play a role(s) in this cancer. TSPY is the putative gene for the gonadoblastoma locus on the Y chromosome (GBY) that is ectopically expressed in a subset of male hepatocellular carcinomas (HCCs). Although various studies showed that TSPY expression is associated with poor prognosis in the patients and its overexpression promotes cell proliferation of various cancer cell lines, it remains unclear how TSPY contributes to the clinical outcomes of the HCC patients. Identifying the downstream genes and pathways of TSPY actions would provide novel insights on its contribution(s) to male predominance in this deadly cancer.

Results

To determine the effects of TSPY on HCC, a TSPY transgene was introduced to the HCC cell line, HuH-7, and studied with RNA-Seq transcriptome analysis. The results showed that TSPY upregulates various genes associated with cell-cycle and cell-viability, and suppresses cell-death related genes. To correlate the experimental observations with those of clinical specimens, transcriptomes of male HCCs with high TSPY expression were analyzed with reference to those with silent TSPY expression from the Cancer Genome Atlas (TCGA). The comparative analysis identified 49 genes, which showed parallel expression patterns between HuH-7 cells overexpressing TSPY and clinical specimens with high TSPY expression. Among these 49 genes, 16 likely downstream genes could be associated with survival rates in HCC patients. The major upregulated targets were cell-cycle related genes and growth factor receptor genes, including CDC25B and HMMR, whose expression levels are negatively correlated with the patient survival rates. In contrast, PPARGC1A, SLC25A25 and SOCS2 were downregulated with TSPY expression, and possess favorable prognoses for HCC patients.

Conclusion

We demonstrate that TSPY could exacerbate the oncogenesis of HCC by differentially upregulate the expression of pro-oncogenic genes and downregulate those of anti-oncogenic genes in male HCC patients, thereby contributing to the male predominance in this deadly cancer.

Electronic supplementary material

The online version of this article (10.1186/s13578-019-0287-x) contains supplementary material, which is available to authorized users.

Aberrant activation of the human sex-determining gene in early embryonic development results in postnatal growth retardation and lethality in mice

Sexual dimorphisms are prevalent in development, physiology and diseases in humans. Currently, the contributions of the genes on the male-specific region of the Y chromosome (MSY) in these processes are uncertain. Using a transgene activation system, the human sex-determining gene hSRY is activated in the single-cell embryos of the mouse. Pups with hSRY activated (hSRY^ON) are born of similar sizes as those of non-activated controls. However, they retard significantly in postnatal growth and development and all die of multi-organ failure before two weeks of age. Pathological and molecular analyses indicate that hSRY^ON pups lack innate suckling activities, and develop fatty liver disease, arrested alveologenesis in the lung, impaired neurogenesis in the brain and occasional myocardial fibrosis and minimized thymus development. Transcriptome analysis shows that, in addition to those unique to the respective organs, various cell growth and survival pathways and functions are differentially affected in the transgenic mice. These observations suggest that ectopic activation of a Y-located SRY gene could exert male-specific effects in development and physiology of multiple organs, thereby contributing to sexual dimorphisms in normal biological functions and disease processes in affected individuals.

The Y-located proto-oncogene TSPY exacerbates and its X-homologue TSPX inhibits transactivation functions of androgen receptor and its constitutively active variants

The gonadoblastoma gene, testis-specific protein Y-encoded (TSPY), on the Y chromosome and its X-homologue, TSPX, are cell cycle regulators and function as a proto-oncogene and a tumor suppressor respectively in human oncogenesis. TSPY and TSPX competitively bind to the androgen receptor (AR) and AR variants, such as AR-V7, at their conserved SET/NAP domain, and exacerbate and repress the transactivation of the AR/AR-V7 target genes in ligand dependent and independent manners respectively. The inhibitory domain has been mapped to the carboxyl acidic domain of TSPX, truncation of which renders TSPX to be stimulatory while its transposition to the C-terminus of TSPY results in an inhibitory hybrid protein. TSPY and TSPX co-localize with the endogenous AR, in the presence of ligand, on the promoters and differentially regulate the expression of the endogenous AR target genes in the androgen-responsive LNCaP prostate cancer cells. Transcriptome analysis shows that TSPY and TSPX expressions differentially affect significant numbers of canonical pathways, upstream regulators and cellular functions. Significantly, among the common ones, TSPY activates and TSPX inhibits numerous growth-related and oncogenic canonical pathways and cellular functions in the respective cell populations. Hence, TSPY and TSPX exert opposing effects on the transactivation functions of AR and AR-Vs important for various physiological and disease processes sensitive to male sex hormone actions, thereby not only affecting the pathogenesis of male-specific prostate cancer but also likely contributing to sex differences in the health and diseases of man.

Spatiotemporal expression of UPK3B and its promoter activity during embryogenesis and spermatogenesis

Uroplakin (Upk) 3 is one of the main structural components of the urothelium tissue. Although expression of UPK3B is seen in a wider variety of the tissues and organs than UPK3A, tissue-specific expression has not yet been analyzed. Here, we analyzed the Cre recombinase activity driven by the Upk3b promoter in transgenic mice and the endogenous localization of UPK3B. We generated Tg(Upk3b-Cre)/R26^tdTomato mice by crossing ROSA26^{tm14(CAG-tdTomato)} (R26^tdTomato) mice with Tg(Upk3b-Cre) mice and investigated the spatiotemporal distribution of tdTomato in embryonic and adult mice. In embryos, we detected Cre recombinase activity in neural crest cells and the heart, liver, kidneys, and lungs. In adult mice, Cre recombinase activity was detected in male and female genital organs; however, the activity was absent in the bladder. Histological analyses revealed that both tdTomato and UPK3B were present in testicular and epididymal sperm; however, tdTomato was not present in the ductus epididymis, where the endogenous expression of UPK3B was detected. In female siblings, both tdTomato and UPK3B expressions were detected in the follicles of the ovary, whereas no tdTomato expression was found in the mucosal epithelium of the fallopian tubes, where the endogenous UPK3B was expressed. These data suggest that UPK3B may play a pivotal role in the maturation of gametes and gamete-delivery organs.

The potential contributions of a Y-located protooncogene and its X homologue in sexual dimorphisms in hepatocellular carcinoma

There is a significant sex disparity favoring males among hepatocellular carcinoma (HCC) patients. Although various risk factors have been identified, the exact etiology of such sexual dimorphism(s) in HCC is uncertain. Previous studies showed that overexpression of the Y-located protooncogene, testis-specific protein Y encoded (TSPY), promotes cell proliferation and oncogenesis whereas its X-located homologue, TSPYhomologue X (TSPX), retards cell cycle and oncogenic progression. Furthermore, TSPX promotes proteasomal degradation of hepatitis B virus-encoded X oncoprotein and hence could serve as a tumor suppressor in virus-associated HCC. Using immunohistochemistry and reverse-transcription polymerase chain reaction analysis, we had examined the expression of TSPY and TSPX with reference to other established biomarkers in HCC and related liver cancers. Our results demonstrated that 55 (19.2%) of 287 male cases were TSPY positive in immunohistochemistry of tissue arrays, and 15 (46.9%) of 32 male cases were TSPY positive in reverse-transcription polymerase chain reaction analysis of clinical samples. TSPY expression was closely associated with the expression of HCC biomarkers, such as glypican 3. In contrast, TSPX expression was down-regulated in 54.5% of total tumor/nontumorous paired samples (18/33) and negatively associated with those of TSPY, glypican 3, and forkhead box M1 (FOXM1) and was positively associated with that of a tumor suppressor, insulin-like growth factor binding protein 3. The present findings support the hypothesis that the oncogenic events leading to an ectopic activation of the Y-located protooncogene TSPY and/or inactivating mutation/epigenetic silencing of the X-located tumor suppressor gene TSPX could collectively contribute to the sexual dimorphism(s) in HCC and related liver cancers in male-biased manners.

The Y-located gonadoblastoma gene TSPY amplifies its own expression through a positive feedback loop in prostate cancer cells

The testis-specific protein Y-encoded (TSPY) is a repetitive gene located on the gonadoblastoma region of the Y chromosome, and has been considered to be the putative gene for this oncogenic locus on the male-only chromosome. It is expressed in spermatogonial cells and spermatocytes in normal human testis, but abundantly in gonadoblastoma, testicular germ cell tumors and a variety of somatic cancers, including melanoma, hepatocellular carcinoma and prostate cancer. Various studies suggest that TSPY accelerates cell proliferation and growth, and promotes tumorigenesis. In this report, we show that TSPY could bind directly to the chromatin/DNA at exon 1 of its own gene, and greatly enhance the transcriptional activities of the endogenous gene in the LNCaP prostate cancer cells. Domain mapping analyses of TSPY have localized the critical and sufficient domain to the SET/NAP-domain. These results suggest that TSPY could efficiently amplify its expression and oncogenic functions through a positive feedback loop, and contribute to the overall tumorigenic processes when it is expressed in various human cancers.

Over-expressed Testis-specific Protein Y-encoded 1 as a novel biomarker for male hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a male-predominant cancer. Previous studies have focused on the sex-related disparity in HCC, but the underlying mechanism remains unclear. Here, we aimed to discover characteristic biomarkers for male HCC. Clinical samples were subjected to iTRAQ labeling followed by 2DLC-ESI-MS/MS analysis. Seventy-three differential proteins containing 16 up-regulated and 57 down-regulated proteins were screened out in the male HCC group compared to that in female HCC group. Testis-specific Protein Y-encoded 1(TSPY1) is characteristically present in male HCC and was chosen for further investigation. The data from the functional effects of TSPY1 indicated that over-expression of TSPY1 could potentiate HCC cell proliferation, increase soft agar colonization, induce higher cell invasive ability and correlate with the metastatic potential of the HCC cell lines. In addition, TSPY1 and androgen receptor (AR) were co-expressed simultaneously in HCC cell lines as well as in HCC tissue. TSPY1 up- or down-regulation could lead to a high or low level expression of AR. These results implied that TSPY1 may be included in the regulation of AR expression involved in male HCC and it may act as a novel biomarker for male HCC.

Expression of a Y-located human proto-oncogene TSPY in a transgenic mouse model of prostate cancer

BACKGROUND

The human TSPY is the putative gene for the gonadoblastoma locus on the Y chromosome (GBY). Various molecular, pathological and transgenic mouse studies suggest that TSPY is a Y-located proto-oncogene contributing to the initiation/progression in human cancers, including germ cell tumors and various somatic cancers, such as prostate and liver cancer, and melanoma. The TgTSPY9 transgenic mouse line harbors a 8.2-kb human TSPY structural gene, which is tandemly integrated in the mouse Y chromosome, and expressed in a similar pattern as that of the endogenous gene in the human genome. This mouse model of human TSPY gene offers an opportunity to examine its behavior and potential contribution in various mouse models of human diseases, such as human cancers. We had investigated the expression of such TSPY-transgene in the LADY mouse model of prostate cancer, harboring a SV40 T antigen gene directed by a rat probasin promoter; and compared the expression pattern with those of endogenous TSPY gene and biomarkers in human prostate cancer specimens.

RESULTS

By introducing the Y-located TSPY-transgene to the LADY mice, we had examined the expression pattern of the human TSPY during prostatic oncogenesis in this mouse model of prostate cancer. Our results showed that the TSPY-transgene was activated in selected areas of the hypercellular stroma but not in the intraepithelial cells/neoplasia in the prostates of TgTSPY9/LADY mice. Using a specific biomarker, FOXA1, for epithelial cells, we demonstrated that TSPY-positive cells proliferated exclusively in the cancerous stroma in the LADY model at late stages of tumorigenesis. In contrast, in the human situation, TSPY was predominantly co-expressed with FOXA1 in the epithelial cells of PIN lesions and FOXA1 and another cancer biomarker, AMACR, in the adenocarcinoma cells in clinical prostate cancer samples of various degrees of malignancy.

CONCLUSIONS

Our data show that human TSPY could be abnormally activated during prostatic oncogenesis, and could possibly contribute to the heterogeneity of prostate cancer. The differential expression patterns of the human TSPY between the LADY mouse model and clinical prostate cancer suggest potential limitations of current mouse models for studies of either TSPY behavior in diseased conditions or prostate cancer development.

A Wisp3 Cre-knockin allele produces efficient recombination in spermatocytes during early prophase of meiosis I

Individuals with the autosomal recessive skeletal disorder Progressive Pseudorheumatoid Dysplasia have loss-of-function mutations in WISP3, and aberrant WISP3 expression has been detected in tumors from patients with colon and breast cancer. In mice however, neither absence nor over-expression of WISP3 was found to cause a phenotype, and endogenous Wisp3 expression has been difficult to detect. To confirm that Wisp3 knockout mice have no phenotype and to identify potential sites of endogenous Wisp3 expression, we generated mice with a knockin allele (Wisp3 (GFP-Cre)) designed to express Green Fluorescent Protein (GFP) and Cre-recombinase instead of WISP3. Heterozygous and homozygous knockin mice were fertile and indistinguishable from their wild-type littermates, confirming that mice lacking Wisp3 have no phenotype. We could not detect GFP-expression from the knockin allele, but we could detect Cre-expression after crossing mice with the knockin allele to Cre-reporter mice; the double heterozygous offspring had evidence of Cre-mediated recombination in several tissues. The only tissue that had high levels of Cre-mediated recombination was the testis, where recombination in spermatocytes occurred by early prophase of meiosis I. As a consequence, males that were double heterozygous for a Wisp3 (GFP-Cre) and a floxed allele only contributed a recombined allele to their offspring. We detected no evidence of Cre-mediated recombination in the female ovary, although when double heterozygous females contributed the reporter allele to their offspring it had recombined ~7% of the time. Wisp3 (GFP-Cre) expression therefore occurs less frequently and most likely at a later stage of oocyte development in female mice compared to male mice. We conclude that although WISP3 is dispensable in mice, male mice with a Wisp3 (GFP-Cre) allele (Jackson Laboratory stock # 017685) will be useful for studying early prophase of meiosis I and for efficiently recombining floxed alleles that are passed to offspring.

The promoter of the oocyte-specific gene, Oog1, functions in both male and female meiotic germ cells in transgenic mice

Oog1 is an oocyte-specific gene whose expression is turned on in mouse oocytes at embryonic day (E) 15.5, concomitant with the time when most of the female germ cells stop proliferating and enter meiotic prophase. Here, we characterize the Oog1 promoter, and show that transgenic GFP reporter expression driven by the 2.7 kb and 3.9 kb regions upstream of the Oog1 transcription start site recapitulates the intrinsic Oog1 expression pattern. In addition, the 3.9 kb upstream region exhibits stronger transcriptional activity than does the 2.7 kb region, suggesting that regulatory functions might be conserved in the additional 1.2 kb region found within the 3.9 kb promoter. Interestingly, the longer promoter (3.9 kb) also showed strong activity in male germ cells, from late pachytene spermatocytes to elongated spermatids. This is likely due to the aberrant demethylation of two CpG sites in the proximal promoter region. One was highly methylated in the tissues in which GFP expression was suppressed, and another was completely demethylated only in Oog1pro3.9 male and female germ cells. These results suggest that aberrant demethylation of the proximal promoter region induced ectopic expression in male germ cells under the control of 3.9 kb Oog1 promoter. This is the first report indicating that sex-dependent gene expression is altered according to the length and the methylation status of the promoter region. Additionally, our results show that individual CpG sites are differentially methylated and play different roles in regulating promoter activity and gene transcription.

Incomplete cre-mediated excision leads to phenotypic differences between Stra8-iCre; Mov10l1(lox/lox) and Stra8-iCre; Mov10l1(lox/Δ) mice

In the Cre-loxp system, expression level and activity of Cre recombinase in a Cre deleter line are critical because these determine not only the cell specificity of gene knockout (KO), but also the efficiency of Cre-mediated excision in a specific cell lineage. Although the spatiotemporal expression pattern of a Cre transgene is usually defined upon the generation of the mouse line, the Cre excision efficiency in a specific targeted cell lineage is rarely evaluated and often assumed to be 100%. Incomplete excision can lead to highly variable phenotypes owing to mosaicism (i.e., coexistence of cells with the flox or the recombined flox allele) and this problem has long been overlooked. Here, we report that Stra8-codon-improved Cre recombinase (iCre), a transgenic allele expressing iCre under the control of the male germ cell-specific Stra8 promoter, could efficiently delete one Mov10l1 flox allele in spermatogenic cells, whereas the excision was incomplete when two Mov10l1 flox alleles were present. The incomplete Cre-mediated excision led to a testicular phenotype that was much less severe than that in the true conditional KO (inactivation, 100%) mice. Our findings suggest that it is essential to determine the efficiency of Cre excision when Cre-loxp system is used for deleting genes in a specific cell lineage and the Cre; gene(lox) (/)(Δ) genotype should be used to evaluate phenotypes instead of Cre; gene(lox/lox) owing to the fact that the latter usually bears incomplete deletion of the flox allele(s).

Prevalence of c-KIT mutations in gonadoblastoma and dysgerminomas of patients with disorders of sex development (DSD) and ovarian dysgerminomas

Activating c-KIT mutations (exons 11 and 17) are found in 10–40% of testicular seminomas, the majority being missense point mutations (codon 816). Malignant ovarian dysgerminomas represent ∼3% of all ovarian cancers in Western countries, resembling testicular seminomas, regarding chromosomal aberrations and c-KIT mutations. DSD patients with specific Y-sequences have an increased risk for Type II Germ Cell Tumor/Cancer, with gonadoblastoma as precursor progressing to dysgerminoma. Here we present analysis of c-KIT exon 8, 9, 11, 13 and 17, and PDGFRA exon 12, 14 and 18 by conventional sequencing together with mutational analysis of c-KIT codon 816 by a sensitive and specific LightCycler melting curve analysis, confirmed by sequencing. The results are combined with data on TSPY and OCT3/4 expression in a series of 16 DSD patients presenting with gonadoblastoma and dysgerminoma and 15 patients presenting pure ovarian dysgerminomas without DSD. c-KIT codon 816 mutations were detected in five out of the total of 31 cases (all found in pure ovarian dysgerminomas). A synonymous SNP (rs 5578615) was detected in two patients, one DSD patient (with bilateral disease) and one patient with dysgerminoma. Next to these, three codon N822K mutations were detected in the group of 15 pure ovarian dysgerminomas. In total activating c-KIT mutations were found in 53% of ovarian dysgerminomas without DSD. In the group of 16 DSD cases a N505I and D820E mutation was found in a single tumor of a patient with gonadoblastoma and dysgerminoma. No PDGFRA mutations were found. Positive OCT3/4 staining was present in all gonadoblastomas and dysgerminomas investigated, TSPY expression was only seen in the gonadoblastoma/dysgerminoma lesions of the 16 DSD patients. This data supports the existence of two distinct but parallel pathways in the development of dysgerminoma, in which mutational status of c-KIT might parallel the presence of TSPY.

Sequence recombination in exon 1 of the TSPY gene in men with impaired fertility

AIM

The aim of this study was to evaluate TSPY (testis specific protein on the Y chromosome) gene and 5'UTR (UnTranslated Region) polymorphisms in men with impaired fertility compared to fertile controls.

METHODS

We analyzed 72 infertile men and 31 fertile controls usingconventional sequencing analysis to find crucial SNPs (single nucleotide polymorphism) and other changes.

RESULTS

The most remarkable changes were found in the 1(st) exon only. In one half of the both infertile men and fertile controls, the most frequent finding was 26 SNPs with a similar pattern. In the other half we found highly relevant changes, generating a stop codon in the first third of exon 1. Early termination cut down the protein by 78.5%. This kind of change was not found in the fertile controls. No correlation was found between the spermiogram and the changes leading to the stop codon. The distribution of men with deletions, insertion and higher gene copy number was not statistically different.

CONCLUSION

The changes found in exon 1 in infertile men could fundamentally affect the process of spermatogenesis. These findings could significantly enhance our understanding of the molecular-genetic causes of male infertility.

Delayed Recognition of Disorders of Sex Development (DSD): A Missed Opportunity for Early Diagnosis of Malignant Germ Cell Tumors

Disorders of sex development (DSD) are defined as a congenital condition in which development of chromosomal, gonadal or anatomical sex is atypical. DSD patients with gonadal dysgenesis or hypovirilization, containing part of the Y chromosome (GBY), have an increased risk for malignant type II germ cell tumors (GCTs: seminomas and nonseminomas). DSD may be diagnosed in newborns (e.g., ambiguous genitalia), or later in life, even at or after puberty. Here we describe three independent male patients with a GCT; two were retrospectively recognized as DSD, based on the histological identification of both carcinoma in situ and gonadoblastoma in a single gonad as the cancer precursor. Hypospadias and cryptorchidism in their history are consistent with this conclusion. The power of recognition of these parameters is demonstrated by the third patient, in which the precursor lesion was diagnosed before progression to invasiveness. Early recognition based on these clinical parameters could have prevented development of (metastatic) cancer, to be treated by systemic therapy. All three patients showed a normal male 46,XY karyotype, without obvious genetic rearrangements by high-resolution whole-genome copy number analysis. These cases demonstrate overlap between DSD and the so-called testicular dysgenesis syndrome (TDS), of significant relevance for identification of individuals at increased risk for development of a malignant GCT.

Mice overexpression of human augmenter of liver regeneration (hALR) in male germ cells shows abnormal spermatogenesis and reduced fertility

Human augmenter of liver regeneration (hALR) is a sulfhydryl oxidase that is highly expressed in spermatogonia and early spermatocytes. To investigate the physiological effects of hALR in spermatogenesis, we generated a hALR transgenic mouse model driven by the human TSPY (testis-specific protein, Y-encoded) promoter that allows the transgene to be specifically activated in the testes. hALR content was found to be increased in both germ cells. The histological and TUNEL analysis of transgenic testes revealed a number of spermatogenetic defects including primary spermatocyte overpopulation followed by depletion through apoptosis, degenerating and detached nucleated germ cells, haploid cell loss and intraepithelial vacuoles of varying sizes. In line with these features, adult transgenic male mice also displayed a reduction in fertility. Our data suggest that regulated spatial and temporal expression of hALR is required for normal testicular development and spermatogenesis, and overexpression of hALR results in influencing the sperm morphology and quantity and the eventual reduction in male fertility. Present findings in the mouse may be of interest to human male fertility.

Expression of the human TSPY gene in the brains of transgenic mice suggests a potential role of this Y chromosome gene in neural functions

The testis specific protein Y-encoded (TSPY) is a member of TSPY/SET/NAP1 superfamily, encoded within the gonadoblastoma locus on the Y chromosome. TSPY shares a highly conserved SET/NAP-domain responsible for protein--protein interaction among TSPY/SET/NAP1 proteins. Accumulating data, so far, support the role of TSPY as the gonadoblastoma gene, involved in germ cell tumorigenesis. The X-chromosome homolog of TSPY, TSPX is expressed in various tissues at both fetal and adult stages, including the brain, and is capable of interacting with the multi-domain adapter protein CASK, thereby influencing the synaptic and transcriptional functions and developmental regulation of CASK in the brain and other neural tissues. Similar to TSPX, we demonstrated that TSPY could interact with CASK at its SET/NAP-domain in cultured cells. Transgenic mice harboring a human TSPY gene and flanking sequences showed specific expression of the human TSPY transgene in both testis and brain. The neural expression pattern of the human TSPY gene overlapped with those of the endogenous mouse Cask and Tspx gene. Similarly with TSPX, TSPY was co-localized with CASK in neuronal axon fibers in the brain, suggesting a potential role(s) of TSPY in development and/or physiology of the nervous system.

Role of the Y-located putative gonadoblastoma gene in human spermatogenesis

The gonadoblastoma locus on the human Y chromosome (GBY) is postulated to serve normal functions in spermatogenesis, but could exert oncogenic properties in predisposing susceptible germ cells to tumorigenesis in incompatible niches such as streaked gonads in XY sex reversed patients or dysfunctional testis in males. The testis-specific protein Y-linked (TSPY) repeat gene has recently been demonstrated to be the putative gene for GBY, based on its location on the GBY critical region, expression patterns in early and late stages of gonadoblastoma and ability to induce gonadoblastoma-like structures in the ovaries of transgenic female mice. Over-expression of TSPY accelerates G(2)/M progression in the cell cycle by enhancing the mitotic cyclin B-CDK1 kinase activities. Currently the normal functions of TSPY in spermatogenesis are uncertain. Expression studies of TSPY, and its X-homologue, TSPX, in normal human testis suggest that TSPY is co-expressed with cyclin B1 in spermatogonia and various stages of spermatocytes while TSPX is principally expressed in Sertoli cells in the human testis. The co-expression pattern of TSPY and cyclin B1 in spermatogonia and spermatocytes suggest respectively that 1) TSPY is important for male spermatogonial cell replication and renewal in the testis; and 2) TSPY could be a catalyst/meiotic factor essential for augmenting the activities of cyclin B-cyclin dependent kinases, important for the differentiation of the spermatocytes in prophase I and in preparation for consecutive rounds of meiotic divisions without an intermediate interphase during spermatogenesis.

Good planning and serendipity: exploiting the Cre/Lox system in the testis

Over the past 20 years, genetic manipulation has revolutionised our understanding of male reproductive development and function. The advent of transgenic mouse lines has permitted elegant dissection of previously intractable issues. The development of the Cre/Lox system, which has permitted spatial and temporal localisation of genetic manipulation, has expanded upon this, and now makes up one of the primary approaches underpinning our increasing understanding of testis development and function. The success of conditional gene targeting is largely reliant upon the choice of Cre recombinase expressing mouse line, which is required to specifically target the correct cell type at the correct time. Presupposition that Cre lines will behave as expected has been one of the main oversights in the design of Cre/Lox experiments, as in practice, many Cre lines are prone to ectopic expression (both temporal and spatial), transgene silencing or genetic background effects. Empirical validation of the spatiotemporal profile of Cre expression prior to undertaking conditional gene targeting studies is essential and can be achieved through a combination of molecular and immunohistochemical approaches, along with in vivo examination of reporter gene expression in targeted tissues. This paper details the key considerations associated with exploitation of the Cre/Lox system and highlights a variety of validated Cre lines that have utility for conditional gene targeting within the testis.

TSPY and Male Fertility

Spermatogenesis requires the concerted action of thousands of genes, all contributing to its efficiency to a different extent. The Y chromosome contains several testis-specific genes and among them the AZF region genes on the Yq and the TSPY1 array on the Yp are the most relevant candidates for spermatogenic function. TSPY1 was originally described as the putative gene for the gonadoblastoma locus on the Y (GBY) chromosome. Besides its oncogenic properties, expression analyses in the testis and in vitro and in vivo studies all converge on a physiological involvement of the TSPY1 protein in spermatogenesis as a pro-proliferative factor. The majority of TSPY1 copies are arranged in 20.4 kb of tandemly repeated units, with different copy numbers among individuals. Our recent study addressing the role of TSPY1 copy number variation in spermatogenesis reported that TSPY1 copy number influences spermatogenic efficiency and is positively correlated with sperm count. This finding provides further evidence for a role of TSPY1 in testicular germ cell proliferation and stimulates future research aimed at evaluating the relationship between the copy number and the protein expression level of the TSPY1 gene.

Transgenic Mouse Studies to Understand the Regulation, Expression and Function of the Testis-Specific Protein Y-Encoded (TSPY) Gene

The TSPY gene, which encodes the testis-specific protein, Y-encoded, was first discovered and characterized in humans, but orthologous genes were subsequently identified on the Y chromosome of many other placental mammals. TSPY is expressed in the testis and to a much lesser extent in the prostate gland, and it is assumed that TSPY serves function in spermatogonial proliferation and/or differentiation. It is further supposed that TSPY is involved in male infertility and exerts oncogenic effects in gonadal and prostate tumor formation. As a member of the TSPY/SET/NAP protein family, TSPY is able to bind cyclin B types, and stimulates the cyclin B1-CDK1 kinase activity, thereby accelerating the G₂/M phase transition of the cell cycle of target cells. Because the laboratory mouse carries only a nonfunctional Y-chromosomal Tspy-ps pseudogene, a knockout mouse model for functional research analyses is not a feasible approach. In the last decade, three classical transgenic mouse models have been developed to contribute to our understanding of TSPY regulation, expression and function. The different transgenic mouse approaches and their relevance for studying TSPY regulation, expression and function are discussed in this review.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 5: intercellular junctions and contacts between germs cells and Sertoli cells and their regulatory interactions, testicular cholesterol, and genes/proteins associated with more than one germ cell generation

In the testis, cell adhesion and junctional molecules permit specific interactions and intracellular communication between germ and Sertoli cells and apposed Sertoli cells. Among the many adhesion family of proteins, NCAM, nectin and nectin-like, catenins, and cadherens will be discussed, along with gap junctions between germ and Sertoli cells and the many members of the connexin family. The blood-testis barrier separates the haploid spermatids from blood borne elements. In the barrier, the intercellular junctions consist of many proteins such as occludin, tricellulin, and claudins. Changes in the expression of cell adhesion molecules are also an essential part of the mechanism that allows germ cells to move from the basal compartment of the seminiferous tubule to the adluminal compartment thus crossing the blood-testis barrier and well-defined proteins have been shown to assist in this process. Several structural components show interactions between germ cells to Sertoli cells such as the ectoplasmic specialization which are more closely related to Sertoli cells and tubulobulbar complexes that are processes of elongating spermatids embedded into Sertoli cells. Germ cells also modify several Sertoli functions and this also appears to be the case for residual bodies. Cholesterol plays a significant role during spermatogenesis and is essential for germ cell development. Lastly, we list genes/proteins that are expressed not only in any one specific generation of germ cells but across more than one generation.

FIGLA, a basic helix-loop-helix transcription factor, balances sexually dimorphic gene expression in postnatal oocytes

Maintenance of sex-specific germ cells requires balanced activation and repression of genetic hierarchies to ensure gender-appropriate development in mammals. Figla (factor in the germ line, alpha) encodes a germ cell-specific basic helix-loop-helix transcription factor first identified as an activator of oocyte genes. In comparing the ovarian proteome of normal and Figla null newborn mice, 18 testis-specific or -enhanced proteins were identified that were more abundant in Figla null ovaries than in normal ovaries. Transgenic mice, ectopically expressing Figla in male germ cells, downregulated a subset of these genes and demonstrated age-related sterility associated with impaired meiosis and germ cell apoptosis. Testis-associated genes, including Tdrd1, Tdrd6, and Tdrd7, were suppressed in the transgenic males with a corresponding disruption of the sperm chromatoid body and mislocalization of MVH and MILI proteins, previously implicated in posttranscriptional processing of RNA. These data demonstrate that physiological expression of Figla plays a critical dual role in activation of oocyte-associated genes and repression of sperm-associated genes during normal postnatal oogenesis.

Partial rescue of the KIT-deficient testicular phenotype in KitW-v/KitW-v Tg(TSPY) mice

TSPY encodes the testis-specific protein Y-linked. In man, expression of TSPY is restricted to the testis, where TSPY is expressed in spermatogonia, primary spermatocytes, and round spermatids, and to the prostate gland. There is circumstantial evidence that TSPY is involved in spermatogonial proliferation and gonadal tumorigenesis. Because the laboratory mouse carries the Tspy gene in a naturally silenced state (Tspy-ps), we previously restored TSPY activity in mice and generated a TSPY transgenic mouse line in which the organization and expression of the human TSPY transgene follow the human pattern. In the present study, we generated TSPY transgenic KIT-deficient Kit(W-v)/Kit(W-v) mice and analyzed the histology of the testes and epididymides in order to contribute to understanding TSPY function in early germ cell development and spermatogenesis. The KIT receptor and its ligand KITL, previously called stem cell factor, have an indispensable role in hematopoiesis, melanogenesis, and gametogenesis. Homozygous Kit(W-v) mutant male mice on a C57BL/6J background with a mutation in the Kit gene are infertile due to an almost total loss of germ cells in the testes. In this study, histological analyses of testes and epididymides showed an increased number of meiotic and postmeiotic germ cells in Kit(W-v)/Kit(W-v) Tg(TSPY) mice compared with age-matched Kit(W-v)/Kit(W-v) controls. TSPY was able to restore fertility of some but not all TSPY transgenic Kit(W-v)/Kit(W-v) males. Our findings show that TSPY is able to partially rescue spermatogenesis and fertility of Kit(W-v)/Kit(W-v) mutants and thereby point to a putative role of TSPY in fetal and adult germ cell proliferation.

TSPY1 copy number variation influences spermatogenesis and shows differences among Y lineages

CONTEXT

TSPY1 is a tandemly-repeated gene on the human Y chromosome forming an array of approximately 21-35 copies. The testicular expression pattern and the inferred function of the TSPY1 protein suggest possible involvement in spermatogenesis. However, data are scarce on TSPY1 copy number variation in different Y lineages and its role in spermatogenesis.

OBJECTIVES

We sought to define: 1) the extent of TSPY1 copy number variation within and among Y chromosome haplogroups; and 2) the role of TSPY1 dosage in spermatogenic efficiency.

MATERIALS AND METHODS

A total of 154 idiopathic infertile men and 130 normozoospermic controls from Central Italy were analyzed. We used a quantitative PCR assay to measure TSPY1 copy number and also defined Y haplogroups in all subjects.

RESULTS

We provide evidence that TSPY1 copy number shows substantial variation among Y haplogroups and thus that population stratification does represent a potential bias in case-control association studies. We also found: 1) a significant positive correlation between TSPY1 copy number and sperm count (P < 0.001); 2) a significant difference in mean TSPY1 copy number between patients and controls (28.4 +/- 8.3 vs. 33.9 +/- 10.7; P < 0.001); and 3) a 1.5-fold increased risk of abnormal sperm parameters in men with less than 33 copies (P < 0.001).

CONCLUSIONS

TSPY copy number variation significantly influences spermatogenic efficiency. Low TSPY1 copy number is a new risk factor for male infertility with potential clinical consequences.

A novel SRY missense mutation affecting nuclear import in a 46,XY female patient with bilateral gonadoblastoma

Patients with disorders of sex development (DSD), especially those with gonadal dysgenesis and hypovirilization, are at risk of developing the so-called type II germ cell tumors (GCTs). Both carcinoma in situ and gonadoblastoma (GB) can be the precursor lesion, resulting in a seminomatous or non-seminomatous invasive cancer. SRY mutations residing in the HMG domain are found in 10-15% of 46,XY gonadal dysgenesis cases. This domain contains two nuclear localization signals (NLSs). In this study, we report a unique case of a phenotypical normal woman, diagnosed as a patient with 46,XY gonadal dysgenesis, with an NLS missense mutation, on the basis of the histological diagnosis of a unilateral GB. The normal role of SRY in gonadal development is the upregulation of SOX9 expression. The premalignant lesion of the initially removed gonad was positive for OCT3/4, TSPY and stem cell factor in germ cells, and for FOXL2 in the stromal component (ie, granulosa cells), but not for SOX9. On the basis of these findings, prophylactical gonadectomy of the other gonad was performed, also showing a GB lesion positive for both FOXL2 (ovary) and SOX9 (testis). The identified W70L mutation in the SRY gene resulted in a 50% reduction in the nuclear accumulation of the mutant protein compared with wild type. This likely explains the diminished SOX9 expression, and therefore the lack of proper Sertoli cell differentiation during development. This case shows the value of the proper diagnosis of human GCTs in identification of patients with DSD, which allows subsequent early diagnosis and prevention of the development of an invasive cancer, likely to be treated by chemotherapy at young age.

Gonadoblastoma locus and the TSPY gene on the human Y chromosome

The gonadoblastoma (GBY) locus is the only oncogenic locus on the human Y chromosome. It is postulated to serve a normal function in the testis, but could exert oncogenic effects in dysgenetic gonads of individuals with intersex and/or dysfunctional testicular phenotypes. Recent studies establish the testis-specific protein Y-encoded (TSPY) gene to be the putative gene for GBY. TSPY serves normal functions in male stem germ cell proliferation and differentiation, but is ectopically expressed in early and late stages of gonadoblastomas, testicular carcinoma in situ (the premalignant precursor for all testicular germ cell tumors), seminomas, and selected nonseminomas. Aberrant TSPY expression stimulates protein synthetic activities, accelerates cell proliferation, and promotes tumorigenicity in athymic mice. TSPY binds to type B cyclins, enhances an activated cyclin B-CDK1 kinase activity, and propels a rapid G(2)/M transition in the cell cycle. TSPY also counteracts the normal functions of its X-homologue, TSPX, which also binds to cyclin B and modulates the cyclin B-CDK1 activity to insure a proper G(2)/M transition in the cell cycle. Hence, ectopic expression and actions of the Y-located TSPY gene in incompatible germ cells, such as those in dysgenetic or ovarian environments and dysfunctional testis, disrupt the normal cell cycle regulation and predispose the host cells to tumorigenesis. The contrasting properties of TSPY and TSPX suggest that somatic cancers, such as intracranial germ cell tumors, melanoma, and hepatocellular carcinoma, with detectable TSPY expression could exhibit sexual dimorphisms in the initiation and/or progression of the respective oncogenesis.

Intratubular transplantation as a strategy for establishing animal models of testicular germ cell tumours

Testicular germ cell tumours (TGCTs) are prevalent cancers among young men. Currently, there is no reliable animal model for TGCTs. To establish such animal models, we have explored the possibility of intratubular testicular transplantation as means to deliver tumour cells into the seminiferous tubules of host animals. Our results demonstrated that transplanted cells could effectively populate the testis of a recipient mouse and develop into TGCTs. In addition, the donor cells could be transfected with a specific transgene before transplantation, thereby providing an approach to evaluate the specific effects of gene functions in the oncogenic processes. Hence, depending on selection of specific donor cells or mixtures of donor cells, transplantation models of TGCTs could be significant for studies on the pathogenesis, diagnosis and therapies of such a prevalent and important cancer in men.

The human Y-encoded testis-specific protein interacts functionally with eukaryotic translation elongation factor eEF1A, a putative oncoprotein

Testis-specific protein Y-encoded (TSPY) is the putative gene for the gonadoblastoma locus on the Y chromosome. TSPY is expressed in normal germ cells of fetal and adult testis and ectopically in tumor germ cells, including gonadoblastoma in intersex patients, testicular germ cell tumors, prostate cancer and other somatic cancers. It is a member of the TSPY/SET/NAP1 superfamily and harbors a highly conserved domain, termed SET/NAP domain. To explore its possible role(s) in tumorigenesis, we had performed a yeast two-hybrid screen of a fetal gonadal cDNA library and identified the translation elongation factor eEF1A as a binding partner for TSPY at the SET/NAP domain. TSPY and eEF1A were highly expressed and colocalized in tumor germ cells of human seminoma specimens, suggesting their possible interaction in germ cell tumors. They were colocalized in the cytoplasm and could be co-immunoprecipitated from transfected COS7 cells. Significantly, both eEF1A1 and eEF1A2 have postulated to be involved in various types of human cancer, including breast and prostate cancers. TSPY enhanced protein synthesis of a reporter gene, which was augmented by an overexpression of eEF1A. TSPY also increased the nuclear redistribution of eEF1A, resulting in a parallel increase in reporter gene transcripts. Our results suggest that TSPY could exert its oncogenic function(s) by interacting with eEF1As and stimulating gene expression via its enhancements in protein synthesis and gene transcription.

The Y-encoded TSPY protein: a significant marker potentially plays a role in the pathogenesis of testicular germ cell tumors

The testis-specific protein Y-encoded (TSPY) gene is the putative gene for the gonadoblastoma locus on the Y chromosome (GBY) that predisposes dysgenetic gonads of intersex patients to gonadoblastoma development. TSPY is expressed at high levels in gonadoblastoma tissues, supporting its possible oncogenic function in this type of germ cell tumors. To explore the possibility that this Y chromosome gene is also involved in pathogenesis of the more common testicular germ cell tumors (TGCTs), we have conducted various expression studies using immunohistochemistry, Western blotting, and reverse transcription-polymerase chain reaction analysis on 171 cases of TGCTs and selected normal testis controls. Our results demonstrated that TSPY protein is abundantly expressed in the precursor, carcinoma in situ or intratubular germ cell neoplasia unclassified, and seminoma, but only minimally or not expressed in various types of nonseminomas. TSPY coexpresses with established germ cell tumor markers (such as placental-like alkaline phosphatase, c-KIT, OCT4) and proliferative markers (such as Ki-67 and cyclin B1) in the same tumor cells at both RNA and protein levels. Ectopic TSPY expression in cultured cells up-regulates progrowth genes, including those at chromosome 12p13, frequently gained/amplified in TGCTs. Our results suggest that TSPY, in combination with other markers, could be an important marker for diagnosis and subclassification of TGCTs and support its role in the pathogenesis of both gonadoblastoma and TGCTs.

Testis-specific protein Y-encoded gene is expressed in early and late stages of gonadoblastoma and testicular carcinoma in situ

The testis-specific protein Y-encoded gene (TSPY) is a tandem repeat gene located at the critical region for the gonadoblastoma locus on Y chromosome that predisposes the dysgenetic gonads of intersex individuals to oncogenesis. The expression and molecular properties of TSPY suggest that it is the putative gene for the gonadoblastoma locus on Y chromosome. In this study, we examined the expression of TSPY and other germ cell tumor markers in 4 cases of gonadoblastoma using immunostaining techniques. Our results showed that TSPY expression was closely associated with initiation and various stages of gonadoblastoma development. TSPY protein localized with established germ cell tumor markers, such as the placental alkaline phosphatase, c-KIT, and OCT3/4, in the same tumor cells of both gonadoblastoma and adjacent carcinoma in situ, the precursor for germ cell tumors. These findings support the candidacy of TSPY as the gene for the gonadoblastoma locus on Y chromosome and suggest that TSPY could be a significant marker for these types of germ cell tumors.

Germ cell tumor showing partial trisomy 1 in a gonadectomized intersex child with monosomy X and double Y mosaicism

High incidence of germ cell tumors arising from dysgenetic gonads in patients with sexual chromosome abnormalities has been described, especially in patients with a Y chromosome bearing cell line. Here we report a 14-year-old patient with ambiguous genitalia. Constitutional karyotype showed 45,X/46,X,derY [?t(Yp;Yq)] mosaicism. The patient developed an abdominally located mixed malignant germ cell tumor 5 years after the removal of the dysgenetic gonads. Tumor karyotype showed partial trisomy 1q, a derivative 8q, and a hyperdiploidy with +X, +7, +12, +15, +19, +21, and an unidentified marker.

The rat Tspy is preferentially expressed in elongated spermatids and interacts with the core histones

The testis specific protein Y encoded (TSPY) gene is a tandemly repeated gene on the mammalian Y chromosome. It encodes several slightly variant proteins that harbor a conserved domain of approximately 170 amino acids, termed TSPY/SET/NAP1 domain, capable of binding to cyclin B. The human TSPY is preferentially expressed in spermatogonia and to lesser extent in the spermatids. Although rat harbors a single functional Tspy gene on its Y chromosome, the human and rat genes differ in their expression patterns, suggesting that they might serve different or variant functions in the testis. Transcripts of rTspy were first detected in the testis of 28-day-old rats, at which time the first wave of meiotic division was occurring. The rTspy protein was initially detected in stage-9 elongating spermatids and peaked at stage-13 spermatids in adult testis, but not in spermatogonia, unlike the expression pattern of the human TSPY gene. Using a GST pull-down assay, we demonstrated that rTspy could bind to the core histones H2A, H2B, H3, and H4. Rat Tspy co-localized with the histones in the cytoplasm of selected elongated spermatids. Our results suggest that the rTspy may play critical roles as a histone chaperone during maturation of the elongating spermatids in the rat testis.

Tspy is nonfunctional in the Mongolian gerbil but functional in the Syrian hamster

The TSPY gene is conserved in placental mammals and encodes the testis-specific protein, Y encoded. Within the testis, TSPY expression is restricted to germ cells, and it is assumed that TSPY plays a role in the proliferation of germ cells. Since it was first discovered in humans, TSPY orthologous gene families have been subsequently characterized in many mammalian lineages. In contrast to the situation in cattle and primates, in which TSPY is organized in a moderately repetitive cluster, including functional members and pseudogenes, a peculiar situation is observed in rodents, in which Tspy has been become low or single copy and degenerated to a pseudogene in some species of the subgenus Mus. We have extended this approach and investigated Tspy gene evolution in the Syrian hamster (Mesocricetus auratus) and the Mongolian gerbil (Meriones unguiculatus). Whereas the Syrian hamster Tspy is functionally conserved, organized in multiple copies, and expressed only in testis, the closely related Mongolian gerbil possesses a single-copy pseudogene that is unable to generate a functional transcript. Thus, the Tspy locus has degenerated at least twice at different points of rodent evolution, strongly supporting the hypothesis that the decay of Y-chromosomal genes is an intrinsic evolutionary process. TSPY is the first example of a Y-chromosomal tandem repetitive gene whose decay could be studied in two independent mammalian lineages.

Neuron-specific enolase-cre mouse line with cre activity in specific neuronal populations

To establish genetic tools for conditional gene deletion in mouse neurons, we generated two independent neuron-specific enolase (Nse)-cre transgenic lines. The transgenic line termed Nse-cre(CK1) showed cre activity in most neuronal regions in the nervous system, while the Nse-cre(CK2) line exhibited a unique cre activity that has not been reported in other cre transgenic lines. Nse-cre(CK2) cre activity was detectable from embryogenesis and mostly restricted to neuronal regions. In postnatal brain, the Nse-cre(CK2) line exhibited cre activity limited to differentiated neurons in the cerebral cortex and hippocampus. Cre activity was assayed in several internal organs and sporadic activity was limited to the kidney and testis. We conclude that these cre lines will be useful for studying loss of gene function in specific neuronal populations.

Conditional (loxP-flanked) allele for the gene encoding the retinoic acid-synthesizing enzyme retinaldehyde dehydrogenase 2 (RALDH2)

Retinoic acid, the active vitamin A derivative, has pleiotropic functions during vertebrate development and postnatal life. Retinaldehyde dehydrogenase 2 (RALDH2) acts as the main retinoic acid-synthesizing enzyme during development. Mouse Raldh2 germline null mutants are early embryonic lethal and exhibit complex abnormalities that include defective heart looping morphogenesis. To investigate later functions of this enzyme, we have engineered a "floxed" (loxP-flanked) allele allowing Cre-mediated somatic gene inactivations. Mice heterozygous or homozygous for the floxed Raldh2 allele are viable and fertile. We tested whether the novel Raldh2 allele behaves as a null mutation after Cre-mediated in vivo excision by crossing the conditional mutants with CMV-Cre transgenic mice. An embryonic lethal phenotype indistinguishable from that of germline mutants was obtained. The conditional allele described herein is a genetic tool for studying tissue-specific, RALDH2-dependent functions of retinoic acid during development and in adult life.

TSPY potentiates cell proliferation and tumorigenesis by promoting cell cycle progression in HeLa and NIH3T3 cells

Background

TSPY is a repeated gene mapped to the critical region harboring the gonadoblastoma locus on the Y chromosome (GBY), the only oncogenic locus on this male-specific chromosome. Elevated levels of TSPY have been observed in gonadoblastoma specimens and a variety of other tumor tissues, including testicular germ cell tumors, prostate cancer, melanoma, and liver cancer. TSPY contains a SET/NAP domain that is present in a family of cyclin B and/or histone binding proteins represented by the oncoprotein SET and the nucleosome assembly protein 1 (NAP1), involved in cell cycle regulation and replication.

Methods

To determine a possible cellular function for TSPY, we manipulated the TSPY expression in HeLa and NIH3T3 cells using the Tet-off system. Cell proliferation, colony formation assays and tumor growth in nude mice were utilized to determine the TSPY effects on cell growth and tumorigenesis. Cell cycle analysis and cell synchronization techniques were used to determine cell cycle profiles. Microarray and RT-PCR were used to investigate gene expression in TSPY expressing cells.

Results

Our findings suggest that TSPY expression increases cell proliferation in vitro and tumorigenesis in vivo. Ectopic expression of TSPY results in a smaller population of the host cells in the G₂/M phase of the cell cycle. Using cell synchronization techniques, we show that TSPY is capable of mediating a rapid transition of the cells through the G₂/M phase. Microarray analysis demonstrates that numerous genes involved in the cell cycle and apoptosis are affected by TSPY expression in the HeLa cells.

Conclusion

These data, taken together, have provided important insights on the probable functions of TSPY in cell cycle progression, cell proliferation, and tumorigenesis.