Detection of Recurrent Copy Number Loss at Yp11.2 Involving TSPY Gene Cluster in Prostate Cancer Using Array-Based Comparative Genomic Hybridization

Promoter hypermethylation of Y-chromosome gene PRKY as a potential biomarker for the early diagnosis of prostate cancer

Aim: To develop a methylation marker of Y-chromosome gene in the early diagnosis of prostate cancer (PCa).Materials & methods: We utilized bioinformatics analysis to identify the expression and promoter methylation of Y-chromosome gene PRKY in PCa and other common malignancies. Single-center experiments were conducted to validate the diagnostic value of PRKY promoter methylation in PCa.Results:  PRKY expression was significantly down-regulated in PCa and its mechanism may be related to promoter methylation. PRKY promoter methylation is highly specific for the diagnosis of early PCa, which may be superior to prostate-specific antigen, mpMRI and other excellent molecular biomarkers.Conclusion:  PRKY promoter methylation may be a potential marker for the early and accurate diagnosis of PCa.

Variations in BCO2 Coding Sequence Causing a Difference in Carotenoid Concentration in the Skin of Chinese Indigenous Chicken

Carotenoid consumption decreases the risk of cancer, osteoporosis, or neurodegenerative diseases through interrupting the formation of free radicals. The deposition of carotenoids in chicken skin makes the skin color turn from white into yellow. The enzyme β-carotene oxygenase 2 (BCO2) plays a key role during the degradation process of carotenoids in skin. How the BCO2 affects the skin color of the chicken and whether it is the key factor that results in the phenotypic difference between yellow- and white-skin chickens are still unclear. In this research, the measurement of the concentration of carotenoids in chicken skin by HPLC showed that the carotenoid concentration in chickens with a yellow skin was significantly higher than that in white-skin chickens. Moreover, there were significant differences in BCO2 gene expression in the back skin between yellow- and white-skin chickens. Scanning the SNPs in BCO2 gene revealed a G/A mutation in exon 6 of the BCO2 gene in white and yellow skin chicken. Generally, one SNP c.890A>G was found to be associated with the chicken skin color and may be used as a genetic marker in breeding for yellow skin in Chinese indigenous chickens.

Repetitive DNA Sequences in the Human Y Chromosome and Male Infertility

The male-specific Y chromosome, which is well known for its diverse and complex repetitive sequences, has different sizes, genome structures, contents and evolutionary trajectories from other chromosomes and is of great significance for testis development and function. The large number of repetitive sequences and palindrome structure of the Y chromosome play an important role in maintaining the stability of male sex determining genes, although they can also cause non-allelic homologous recombination within the chromosome. Deletion of certain Y chromosome sequences will lead to spermatogenesis disorders and male infertility. And Y chromosome genes are also involved in the occurrence of reproductive system cancers and can increase the susceptibility of other tumors. In addition, the Y chromosome has very special value in the personal identification and parentage testing of male-related cases in forensic medicine because of its unique paternal genetic characteristics. In view of the extremely high frequency and complexity of gene rearrangements and the limitations of sequencing technology, the analysis of Y chromosome sequences and the study of Y-gene function still have many unsolved problems. This article will introduce the structure and repetitive sequence of the Y chromosome, summarize the correlation between Y chromosome various sequence deletions and male infertility for understanding the repetitive sequence of Y chromosome more systematically, in order to provide research motivation for further explore of the molecules mechanism of Y-deletion and male infertility and theoretical foundations for the transformation of basic research into applications in clinical medicine and forensic medicine.

Y chromosome is moving out of sex determination shadow

Although sex hormones play a key role in sex differences in susceptibility, severity, outcomes, and response to therapy of different diseases, sex chromosomes are also increasingly recognized as an important factor. Studies demonstrated that the Y chromosome is not a 'genetic wasteland' and can be a useful genetic marker for interpreting various male-specific physiological and pathophysiological characteristics. Y chromosome harbors male‑specific genes, which either solely or in cooperation with their X-counterpart, and independent or in conjunction with sex hormones have a considerable impact on basic physiology and disease mechanisms in most or all tissues development. Furthermore, loss of Y chromosome and/or aberrant expression of Y chromosome genes cause sex differences in disease mechanisms. With the launch of the human proteome project (HPP), the association of Y chromosome proteins with pathological conditions has been increasingly explored. In this review, the involvement of Y chromosome genes in male-specific diseases such as prostate cancer and the cases that are more prevalent in men, such as cardiovascular disease, neurological disease, and cancers, has been highlighted. Understanding the molecular mechanisms underlying Y chromosome-related diseases can have a significant impact on the prevention, diagnosis, and treatment of diseases.

Identification of specific DNA methylation sites on the Y-chromosome as biomarker in prostate cancer

As a diagnostic biomarker, prostate special antigen (PSA) tests always generate false positive results and lead to unnecessary and/or repeat biopsies. Therefore, there is an urgent need for developing more sensitive, specific diagnostic biomarkers. We epigenotyped methylated sites in cancer tissues and adjacent normal tissues from 66 patients. In comparison with normal adjacent tissues, we observed that there were 6 aberrant methylation sites in prostate cancer tissues on the Y-chromosome. We further performed pyrosequencing using urine of PCa patients and we identified one methylated site (cg05163709) as a potential biomarker. We evaluated the predictive capacity of the aberrant methylated sites using the area under receiver operating characteristic (ROC) curve (AUC). The ROC analysis showed a higher AUC for cg05163709 (0.915) than prostate-specific antigen (PSA, 0.769). These results indicated that aberrant DNA methylation of cg05163709 on the Y-chromosome could serve as a potential diagnostic biomarker with high sensitivity and specificity.

Differential Regulation of Gene Expression of Alveolar Epithelial Cell Markers in Human Lung Adenocarcinoma-Derived A549 Clones

Stem cell therapy appears to be promising for restoring damaged or irreparable lung tissue. However, establishing a simple and reproducible protocol for preparing lung progenitor populations is difficult because the molecular basis for alveolar epithelial cell differentiation is not fully understood. We investigated an in vitro system to analyze the regulatory mechanisms of alveolus-specific gene expression using a human alveolar epithelial type II (ATII) cell line, A549. After cloning A549 subpopulations, each clone was classified into five groups according to cell morphology and marker gene expression. Two clones (B7 and H12) were further analyzed. Under serum-free culture conditions, surfactant protein C (SPC), an ATII marker, was upregulated in both H12 and B7. Aquaporin 5 (AQP5), an ATI marker, was upregulated in H12 and significantly induced in B7. When the RAS/MAPK pathway was inhibited, SPC and thyroid transcription factor-1 (TTF-1) expression levels were enhanced. After treatment with dexamethasone (DEX), 8-bromoadenosine 3′5′-cyclic monophosphate (8-Br-cAMP), 3-isobutyl-1-methylxanthine (IBMX), and keratinocyte growth factor (KGF), surfactant protein B and TTF-1 expression levels were enhanced. We found that A549-derived clones have plasticity in gene expression of alveolar epithelial differentiation markers and could be useful in studying ATII maintenance and differentiation.

Human Chromosome Y and Haplogroups; introducing YDHS Database

BACKGROUND

As the high throughput sequencing efforts generate more biological information, scientists from different disciplines are interpreting the polymorphisms that make us unique. In addition, there is an increasing trend in general public to research their own genealogy, find distant relatives and to know more about their biological background. Commercial vendors are providing analyses of mitochondrial and Y-chromosomal markers for such purposes. Clearly, an easy-to-use free interface to the existing data on the identified variants would be in the interest of general public and professionals less familiar with the field. Here we introduce a novel metadatabase YDHS that aims to provide such an interface for Y-chromosomal DNA (Y-DNA) haplogroups and sequence variants.

METHODS

The database uses ISOGG Y-DNA tree as the source of mutations and haplogroups and by using genomic positions of the mutations the database links them to genes and other biological entities. YDHS contains analysis tools for deeper Y-SNP analysis.

RESULTS

YDHS addresses the shortage of Y-DNA related databases. We have tested our database using a set of different cases from literature ranging from infertility to autism. The database is at http://www.semanticgen.net/ydhs

CONCLUSIONS

Y-chromosomal DNA (Y-DNA) haplogroups and sequence variants have not been in the scientific limelight, excluding certain specialized fields like forensics, mainly because there is not much freely available information or it is scattered in different sources. However, as we have demonstrated Y-SNPs do play a role in various cases on the haplogroup level and it is possible to create a free Y-DNA dedicated bioinformatics resource.

Copy number differences of Y chromosomal genes between superior and inferior quality semen producing crossbred (Bos taurus × Bos indicus) bulls

The removal of crossbred bulls from semen collection programs due to the production of poor quality semen causes substantial monetary losses to the dairy industry. Seminal quality, a quantitative trait, is greatly influenced by genome level variations. Deletion and/or duplication of Y chromosomal genes and subsequent changes in gene copy number have a major role in determining spermatogenic efficiency and, therefore, seminal quality. In this study, copy numbers of three Y chromosomal genes TSPY, DDX3Y, and USP9Y in genomic DNA were estimated and compared in two groups of crossbred (Bos taurus × Bos indicus) bulls of ten each, superior and inferior quality semen producing bulls, which were classified based on their seminal quality parameters. For TSPY gene, the inferior quality semen donor group has significantly lower copy number than superior quality semen donor group (p < 0.05). No significant difference was found in DDX3Y and USP9Y gene copy numbers between two groups (p > 0.05). In conclusion, this study demonstrates that the copy number of TSPY, a Y chromosomal spermatogenesis related gene, may be an important determinant to predict the quality of bull semen, facilitating better selection of bulls in a herd for semen collection program.

Y genetic variation and phenotypic diversity in health and disease

Sexually dimorphic traits arise through the combined effects of sex hormones and sex chromosomes on sex-biased gene expression, and experimental mouse models have been instrumental in determining their relative contribution in modulating sex differences. A role for the Y chromosome (ChrY) in mediating sex differences outside of development and reproduction has historically been overlooked due to its unusual genetic composition and the predominant testes-specific expression of ChrY-encoded genes. However, ample evidence now exists supporting ChrY as a mediator of other physiological traits in males, and genetic variation in ChrY has been linked to several diseases, including heart disease, cancer, and autoimmune diseases in experimental animal models, as well as humans. The genetic and molecular mechanisms by which ChrY modulates phenotypic variation in males remain unknown but may be a function of copy number variation between homologous X-Y multicopy genes driving differential gene expression. Here, we review the literature identifying an association between ChrY polymorphism and phenotypic variation and present the current evidence depicting the mammalian ChrY as a member of the regulatory genome in males and as a factor influencing paternal parent-of-origin effects in female offspring.

Mosaic loss of chromosome Y in peripheral blood is associated with shorter survival and higher risk of cancer

Incidence and mortality for sex-unspecific cancers is higher among men and is largely unexplained1,2. Furthermore, age-related loss of chromosome Y (LOY) is frequent in normal haematopoietic cells3,4, but the phenotypic consequences of LOY have been elusive5–10. From analysis of 1153 elderly men, we report that LOY was associated with risks of all-cause mortality (HR=1.91, 95% CI=1.17-3.13, events=637) and non-haematological cancer mortality (HR=3.62, CI=1.56-8.41, events=132). LOY affected at least 8.2% of subjects in this cohort and median survival among men with LOY was 5.5 years shorter. Risk of all-cause mortality and LOY was validated in an independent cohort (HR=3.66), in which 20.5% of subjects displayed LOY. These results illustrate the impact of post-zygotic mosaicism on disease risk, could explain why males are more frequently affected by cancer and suggest that chromosome Y is important in processes beyond sex determination. LOY in blood could become a predictive biomarker of male carcinogenesis.

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.

Analysis of clinical characteristics of 516 patients with non-Hodgkin's lymphoma in Shanghai area

The aim was to determine the clinical and cytogenetic characteristics of non-Hodgkin's lymphoma (NHL) in Shanghai. A retrospective analysis was conducted in 516 patients with NHL. Patient clinical data, including age, sex, diagnosis, immunophenotypes, and karyotypes, were collected. The median age was 58 years. There was a male predominance in all NHL, except extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. Patients with B cell NHL (1.5%) expressed CD3. T cell NHL patients (11.5%) expressed CD20. Epstein-Barr virus latent integral membrane protein 1, BCL6, CD10, Bcl-2, CD68, myeloperoxidase, CD99, CD30, CD15, and CD43 were present in various types of NHL. Complex karyotypes accounted for 92.3% of the 73.7% patients with abnormal karyotypes. Immunoglobin heavy chain gene translocation was present in 60.3% of B cell and 23.7% of T/NK cell neoplasms. Understanding the complex clinicopathological and molecular features of NHL may help with prognosis and serve as targets for treatments.

Absolute copy number differences of Y chromosomal genes between crossbred (Bos taurus × Bos indicus) and Indicine bulls

Background

The Y chromosome in mammal is paternally inherited and harbors genes related to male fertility and spermatogenesis. The unique intra-chromosomal recombination pattern of Y chromosome and morphological difference of this chromosome between Bos taurus and Bos indicus make it an ideal model for studying structural variation, especially in crossbred (Bos taurus × Bos indicus) bulls. Copy Number Variation (CNV) is a type of genomic structural variation that gives information complementary to SNP data. The purpose of this study was to find out copy number differences of four Y chromosomal spermatogenesis-related candidate genes in genomic DNA of crossbred and purebred Indicine bulls.

Result

Four Y chromosomal candidate genes of spermatogenesis namely, sex determining gene on Y chromosome (SRY), DEAD box polypeptide 3-Y chromosome (DDX3Y), Ubiquitin specific peptidase 9, Y-linked (USP9Y), testis-specific protein on Y chromosome (TSPY) were evaluated. Absolute copy numbers of Y chromosomal genes were determined by standard curve-based quantitative real time PCR. Copy numbers of SRY and TSPY genes per unit amount of genomic DNA are higher in crossbred than Indicine bulls. However, no difference was observed in DDX3Y and USP9Y gene copy numbers between two groups.

Conclusion

The present study demonstrates that the structural organization of Y chromosomes differs between crossbred and Indicine bulls which are reproductively healthy as observed from analysis of semen attributes. The absolute copy numbers of SRY and TSPY genes in unit mass of genomic DNA of crossbred bulls are significantly higher than Indicine bulls. No alteration in absolute copies of DDX3Y and USP9Y gene was found between the genome of crossbred and Indicine bulls. This study suggests that the DDX3Y and USP9Y are likely to be single copy genes in the genome of crossbred and Indicine bulls and variation in Y chromosome length between crossbred and Indicine bulls may be due to the copy number variation of SRY gene and TSPY array.

A significant effect of the TSPY1 copy number on spermatogenesis efficiency and the phenotypic expression of the gr/gr deletion

AZFc deletions cause a significant phenotypic heterogeneity with respect to spermatogenesis; however, the reason for this is poorly understood. Recently, testis-specific protein Y-encoded 1 (TSPY1) copy number variation (CNV) was determined to be a potential genetic modifier of spermatogenesis. We performed a large-scale cohort study to investigate the effect of TSPY1 CNV on spermatogenesis and to elucidate the possible contribution of TSPY1 genetic variation to the phenotypic expression of AZFc deletions. Haplogrouping of the Y-chromosome and quantification of the TSPY1 copy number were performed in 2272 Han Chinese males with different spermatogenic statuses (704 males with the b2/b4 or gr/gr deletion and 1568 non-AZFc-deleted males). Our data revealed that the TSPY1 copy number distributions were significantly different among non-AZFc-deleted males with different spermatogenic phenotypes. Lower sperm production and an elevated risk of spermatogenic failure were observed in males with fewer than 21 TSPY1 copies and in those with more than 55 copies relative to men with 21-35 copies. Similar results were observed in males with the gr/gr deletion. These findings indicate that TSPY1 CNV affects an individual's susceptibility to spermatogenic failure by modulating the efficiency of spermatogenesis and strongly suggest that there is a significant quantity effect of the TSPY1 copy number on the phenotypic expression of the gr/gr deletion. To our knowledge, this CNV is the first independent genetic factor that has been clearly observed to influence the spermatogenic status of gr/gr deletion carriers. A combined genetic analysis of the TSPY1 copy number and the gr/gr deletion could inform the clinical counselling of infertile couples.

A fresh look at the male-specific region of the human Y chromosome

The Chromosome-centric Human Proteome Project (C-HPP) aims to systematically map the entire human proteome with the intent to enhance our understanding of human biology at the cellular level. This project attempts simultaneously to establish a sound basis for the development of diagnostic, prognostic, therapeutic, and preventive medical applications. In Iran, current efforts focus on mapping the proteome of the human Y chromosome. The male-specific region of the Y chromosome (MSY) is unique in many aspects and comprises 95% of the chromosome's length. The MSY continually retains its haploid state and is full of repeated sequences. It is responsible for important biological roles such as sex determination and male fertility. Here, we present the most recent update of MSY protein-encoding genes and their association with various traits and diseases including sex determination and reversal, spermatogenesis and male infertility, cancers such as prostate cancers, sex-specific effects on the brain and behavior, and graft-versus-host disease. We also present information available from RNA sequencing, protein-protein interaction, post-translational modification of MSY protein-coding genes and their implications in biological systems. An overview of Human Y chromosome Proteome Project is presented and a systematic approach is suggested to ensure that at least one of each predicted protein-coding gene's major representative proteins will be characterized in the context of its major anatomical sites of expression, its abundance, and its functional relevance in a biological and/or medical context. There are many technical and biological issues that will need to be overcome in order to accomplish the full scale mapping.

Molecular mining of alleles in water buffalo Bubalus bubalis and characterization of the TSPY1 and COL6A1 genes

Background

Minisatellites are an integral part of eukaryotic genomes and show variation in the complexity of their organization. Besides their presence in non-coding regions, a small fraction of them are part of the transcriptome, possibly participating in gene regulation, expression and silencing. We studied the minisatellite (TGG)_n tagged transcriptome in the water buffalo Bubalus bubalis across various tissues and the spermatozoa, and characterized the genes TSPY1 and COL6A1 discovered in the process.

Results

Minisatellite associated sequence amplification (MASA) conducted using cDNA and oligonucleotide primer (TGG)₅ uncovered 38 different mRNA transcripts from somatic tissues and gonads and 15 from spermatozoa. These mRNA transcripts corresponded to several known and novel genes. The majority of the transcripts showed the highest level of expression either in the testes or spermatozoa with exception of a few showing higher expression levels in the lungs and liver. Transcript SR1, which is expressed in all the somatic tissues and gonads, was found to be similar to the Bos taurus collagen type VI alpha 1 gene (COL6A1). Similarly, SR29, a testis-specific transcript, was found to be similar to the Bos taurus testis-specific Y-encoded protein-1 representing cancer/testis antigen 78 (CT78). Subsequently, full length coding sequences (cds) of these two transcripts were obtained. Quantitative PCR (q-PCR) revealed 182-202 copies of theTSPY1 gene in water buffalo, which localized to the Y chromosome.

Conclusions

The MASA approach enabled us to identify several genes, including two of clinical significance, without screening an entire cDNA library. Genes identified with TGG repeats are not part of a specific family of proteins and instead are distributed randomly throughout the genome. Genes showing elevated expression in the testes and spermatozoa may prove to be potential candidates for in-depth characterization. Furthermore, their possible involvement in fertility or lack thereof would augment animal biotechnology.

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.

Testis-specific protein on Y chromosome (TSPY) represses the activity of the androgen receptor in androgen-dependent testicular germ-cell tumors

Testis-specific protein on Y chromosome (TSPY) is an ampliconic gene on the Y chromosome, and genetic interaction with gonadoblastoma has been clinically established. However, the function of the TSPY protein remains to be characterized in physiological and pathological settings. In the present study, we observed coexpression of TSPY and the androgen receptor (AR) in testicular germ-cell tumors (TGCTs) in patients as well as in model cell lines, but such coexpression was not seen in normal testis of humans or mice. TSPY was a repressor for androgen signaling because of its trapping of cytosolic AR even in the presence of androgen. Androgen treatment stimulated cell proliferation of a TGCT model cell line, and TSPY potently attenuated androgen-dependent cell growth. Together with the finding that TSPY expression is reduced in more malignant TGCTs in vivo, the present study suggests that TSPY serves as a repressor in androgen-induced tumor development in TGCTs and raises the possibility that TSPY could be used as a clinical marker to assess the malignancy of TGCTs.

Y chromosome TSPY copy numbers and semen quality

OBJECTIVE

To determine whether variation in testis-specific protein Y-encoded (TSPY) gene copy number affects semen quality.

DESIGN

Nested case-control study.

SETTING

University hospital.

PATIENT(S)

From a consecutive cohort of 1,016 male partners of subfertile couples, unselected for sperm counts, we selected as cases 100 men with the lowest total number of progressively motile sperm (TMC) and as controls, 100 men with the highest total number of progressively motile sperm.

INTERVENTION(S)

Quantitative real-time polymerase chain reaction (PCR) and Southern blot to determine TSPY copy number.

MAIN OUTCOME MEASURE(S)

TSPY copy number.

RESULT(S)

The quantitative PCR method showed excellent agreement with the Southern blot analysis. Cases had a median TSPY copy number of 35 (range 20-73), whereas controls had a median TSPY copy number of 34 (range 26-76). This difference was not statistically significant.

CONCLUSION(S)

We found no association between TSPY copy numbers and severe spermatogenic failure. The observed variation in TSPY copy number therefore appears to have no functional consequences for semen quality.

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.

Y chromosome structural and functional changes in human malignant diseases

The main Y chromosome abnormalities found in testicular cancer and other malignant diseases are microdeletions, entire chromosome loss and transcription deregulation of several genes mapping in the non-recombinant part of the Y chromosome. Yet, the role of these changes in the origin or evolution of malignancies is uncertain. The Y chromosome has experienced a long and intricate evolutionary history of deleterious, compensatory, and advantageous mutations. It is proposed that the compensatory mechanisms preventing Y decay in cancer cells are no longer working, and that deletions and gene down-expression reflect a very fast process of Y attrition. From this perspective, Y chromosome aberrations, mutations and unbalanced gene expression very likely play no role in the etiology of cell transformation, although in some forms of cancer, Y abnormalities may influence tumor progression.

Differentially expressed nucleolar transforming growth factor-beta1 target (DENTT) exhibits an inhibitory role on tumorigenesis

Differentially expressed nucleolar transforming growth factor-beta1 target (DENTT), also known as testis-specific protein Y-encoded-like (TSPYL-2) and cell division autoantigen-1, is a member of the testis-specific protein Y-encoded (TSPY)/TSPY-L/SET/nucleosome assembly protein-1 superfamily. DENTT is expressed in various tissues including normal human lung. Here, we investigate the involvement of DENTT in cancer promotion and progression. DENTT messenger RNA (mRNA) and protein levels were shown to be markedly downregulated in human and mouse primary tumors and in human tumor cell lines. Overexpression of DENTT in human lung (A549-DENTT) and breast (MCF-7-DENTT) cancer cells resulted in diminished growth potential in anchorage-dependent growth assays and reduced capacity to form colonies under anchorage-independent culture conditions. The migratory potential of A549-DENTT and MCF-7-DENTT cells was reduced when compared with empty vector control cells. Treating human lung cell lines with demethylating agents increased DENTT expression significantly. DENTT expression pattern paralleled that of transforming growth factor-beta1 (TGF-beta1) in normal and malignant tissue and ectopic expression or treatment with TGF-beta1 in lung cancer cells was followed by increased DENTT mRNA and protein levels. Collectively, our results suggest a role for DENTT as a suppressor of the tumorigenic phenotype.

Genome-wide expression profiling reveals transcriptomic variation and perturbed gene networks in androgen-dependent and androgen-independent prostate cancer cells

Previously, we have developed a unique in vitro LNCaP cell model, which includes androgen-dependent (LNCaP-C33), androgen-independent (LNCaP-C81) and an intermediate phenotype (LNCaP-C51) cell lines resembling the stages of prostate cancer progression to hormone independence. This model is advantageous in overcoming the heterogeneity associated with the prostate cancer up to a certain extent. We characterized and compared the gene expression profiles in LNCaP-C33 (androgen-dependent) and LNCaP-C81 (androgen-independent) cells using Affymetrix GeneChip array analyses. Multiple genes were identified exhibiting differential expression during androgen-independent progression. Among the important genes upregulated in androgen-independent cells were PCDH7, TPTE, TSPY, EPHA3, HGF, MET, EGF, TEM8, etc., whereas many candidate tumor suppressor genes (HTATIP2, CDKN2A, CDKN2B, CDKN1C, TP53, TP73, ICAM1, SOCS1/2, SPRY2, PPP2CA, PPP3CA, etc.) were decreased. Pathway prediction analysis identified important gene networks associated with growth-promoting and apoptotic signaling that were perturbed during androgen-independent progression. Further investigation of one of the genes, PPP2CA, which encodes the catalytic subunit of a serine phosphatase PP2A, a potent tumor suppressor, revealed that its expression was decreased in prostate cancer compared to adjacent normal/benign tissue. Furthermore, the downregulated expression of PPP2CA was significantly correlated with tumor stage and Gleason grade. Future studies on the identified differentially expressed genes and signaling pathways may be helpful in understanding the biology of prostate cancer progression and prove useful in developing novel prognostic biomarkers and therapy for androgen-refractory prostate cancer.

TSPY gene copy number as a potential new risk factor for male infertility

The human TSPY (testis-specific protein, Y-linked) gene family (30-60 copies) is situated in the MSY (male-specific) region of the Y chromosome. Testis-specific expression indicates that the gene plays a role in spermatogenesis. Refined quantitative fluorescence PCR (polymerase chain reaction) was applied to evaluate the relative number of TSPY copies compared with AMELY/X (amelogenin gene, Y-linked) genes in 84 stratified infertile men and in 40 controls. A significantly higher number of TSPY copies was found in infertile men compared with the controls (P = 0.002). The diagnostic discrimination potential of the relative number of TSPY copies was evaluated by receiver operating characteristic curve analysis. TSPY/AMELY was unambiguously found to be powerful in the diagnostic separation of both the control samples and the infertile men, reaching a good level of specificity (0.642) and sensitivity (0.732) at a cut-off point of 0.46. The findings were supported by independently repeated studies of randomly selected positive samples and controls. Evaluation of the TSPY copy number offers a completely new diagnostic approach in relation to the genetic cause of male infertility. The possible effect of the copy number of TSPY genes on spermatogenesis may explain indiscrete pathological alterations of spermatid quality and quantity.