Coordinated transcriptional regulation patterns associated with infertility phenotypes in men

HLA-DQB1 as a potential prognostic biomarker of hormonal therapy in patients with non-obstructive azoospermia

The gonadotropin treatment of infertile men may improve spermatogenesis and lead to sperm cell production, however, only a small fraction of treated patients positively responds to such therapy. To identify individual treatment prognostic biomarkers associated with responsiveness to gonadotropins, we compared the gene expression profiles of testicular oligobiopsies from 3 patients with non-obstructive azoospermia (NOA) who positively responded to therapy with a combination of human chorionic gonadotropin and recombinant follicle-stimulating hormone (hCG/rFSH) to those of 3 non-responders. We used Affymetrix Human Gene 1.0 ST microarrays. The results of the microarray evaluation were validated by the qPCR technique while gene variants of the HLA-DQB1 (major histocompatibility complex, class II, DQ beta 1) were subsequently sequenced. In our microarrays, we have identified most significantly 5 transcripts with different expression levels in responders versus non-responders groups. Our interest has been primarily focused on the transcript associated with the HLA-DQB1 gene. Because the expression of this gene was up-regulated in the non-responding patients and only patients with heterozygotic alleles of HLA-DQB1 turned out to be positive to gonadotropin therapy, we suggest that this gene may be a biomarker of potential significance for the gonadotropin treatment of male infertility. We also compared the testicular gene expression profile in one individual before and after gonadotropin treatment. In the re-biopsied sample, we have identified over 600 genes that showed differences in testicular expression; some of these genes are critical for spermiogenesis. Thus, we documented that the applied gonadotropins successfully stimulated the spermatogenetic wave in patients with NOA.

Transcriptomic signatures for human male infertility

Introduction: Male infertility is a common, complex disorder. A better understanding of pathogenesis and etiology is needed for timely diagnosis and treatment. The aim of this study, therefore, was to identify genes involved in the pathogenesis of idiopathic male infertility based on data from transcriptomic level supported with data from genomic level. Materials and methods: First, we performed whole gene expression analysis in 20 testis biopsy samples of patients with severely impaired (10) and normal spermatogenesis (10). Further, we have performed systematic review of comparable male infertility studies and overlapped the most significantly expressed genes identified in our study with the most differentially expressed genes from selected studies. Gene Ontology analysis and KEGG functional enrichment have been performed with Enrichr analysis tool. Additionally, we have overlapped these genes with the genes where rare variants have been identified previously. Results: In 10 patients with severely impaired spermatogenesis and 10 controls, we identified more than 1,800 differentially expressed genes (p < 0.001). With the systematic review of three previously performed microarray studies that have met inclusion criteria we identified 257 overlapped differentialy expressed genes (144 downregulated and 113 upregulated). Intersection of genes from transcriptomic studies with genes with identified rare variants revealed a total of 7 genes linked with male infertility phenotype (CYP11A1, CYP17A1, RSPH3, TSGA10, AKAP4, CCIN, NDNF). Conclusion: Our comprehensive study highlighted the role of four genes in pathogenesis of male infertility and provided supporting evidence for three promising candidate genes which dysfunction may result in a male infertility disorder.

Whole-genome sequencing identifies new candidate genes for nonobstructive azoospermia

BACKGROUND

Genetic causes that lead to spermatogenetic failure in patients with nonobstructive azoospermia (NOA) have not been yet completely established.

OBJECTIVE

To identify low-frequency NOA-associated single nucleotide variants (SNVs) using whole-genome sequencing (WGS).

MATERIALS AND METHODS

Men with various types of NOA (n = 39), including samples that had been previously tested with whole-exome sequencing (WES; n = 6) and did not result in diagnostic conclusions. Variants were annotated using the Ensembl Variant Effect Predictor, utilizing frequencies from GnomAD and other databases to provide clinically relevant information (ClinVar), conservation scores (phyloP), and effect predictions (i.e., MutationTaster). Structural protein modeling was also performed.

RESULTS

Using WGS, we revealed potential NOA-associated SNVs, such as: TKTL1, IGSF1, ZFPM2, VCX3A (novel disease causing variants), ESX1, TEX13A, TEX14, DNAH1, FANCM, QRICH2, FSIP2, USP9Y, PMFBP1, MEI1, PIWIL1, WDR66, ZFX, KCND1, KIAA1210, DHRSX, ZMYM3, FAM47C, FANCB, FAM50B (genes previously known to be associated with infertility) and ALG13, BEND2, BRWD3, DDX53, TAF4, FAM47B, FAM9B, FAM9C, MAGEB6, MAP3K15, RBMXL3, SSX3 and FMR1NB genes, which may be involved in spermatogenesis.

DISCUSSION AND CONCLUSION

In this study, we identified novel potential candidate NOA-associated genes in 29 individuals out of 39 azoospermic males. Note that in 5 out of 6 patients subjected previously to WES analysis, which did not disclose potentially causative variants, the WGS analysis was successful with NOA-associated gene findings.

A Comparative Cross-Platform Analysis to Identify Potential Biomarker Genes for Evaluation of Teratozoospermia and Azoospermia

Male infertility is a global public health concern. Teratozoospermia is a qualitative anomaly of spermatozoa morphology, contributing significantly to male infertility, whereas azoospermia is the complete absence of spermatozoa in the ejaculate. Thus, there is a serious need for unveiling the common origin and/or connection between both of these diseases, if any. This study aims to identify common potential biomarker genes of these two diseases via an in silico approach using a meta-analysis of microarray data. In this study, a differential expression analysis of genes was performed on four publicly available RNA microarray datasets, two each from teratozoospermia (GSE6872 and GSE6967) and azoospermia (GSE145467 and GSE25518). From the analysis, 118 DEGs were found to be common to teratozoospermia and azoospermia, and, interestingly, sperm autoantigenic protein 17 (SPA17) was found to possess the highest fold change value among all the DEGs (9.471), while coiled-coil domain-containing 90B (CCDC90B) and coiled-coil domain-containing 91 (CCDC91) genes were found to be common among three of analyses, i.e., Network Analyst, ExAtlas, and GEO2R. This observation indicates that SPA17, CCDC90B, and CCDC91 genes might have significant roles to play as potential biomarkers for teratozoospermia and azoospermia. Thus, our study opens a new window of research in this area and can provide an important theoretical basis for the diagnosis and treatment of both these diseases.

Predicting the testicular function in non-obstructive azoospermia via targeted gene panel

Background

Men with non-obstructive azoospermia constitute a challenging subgroup of male infertility patients in whom a genetic cause of defective spermatogenesis may be a contributing factor. The aim of this prospective observational cohort study was to determine whether assessment of meiotic nuclear division 1 (MND1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression (MND1/GAPDH) in testicular tissue could be a prognostic indicator for sperm retrieval and ICSI outcome in patients with non-obstructive azoospermia. The study participants underwent clinical evaluation, conventional semen analysis, serum follicular stimulating hormone (FSH), testosterone assay, scrotal ultrasound examination, microsurgical testicular sperm extraction (mTESE), and assessment of MND1/GAPDH gene expression levels in testicular tissue via quantitative polymerase chain reaction (qPCR) techniques.

Results

The MND1/GAPDH level was associated with the likelihood of identifying sperm in testicular biopsies (odds ratio (OR) 1.25, 95% confidence intervals (CI) 1.14 to 1.34, p < 0.0001), which was confirmed by the pairwise comparison of high vs. low levels of MND1/GAPDH (OR 5.34, 95% CI 1.97 to 13.16, p = 0.0006). The level of FSH was inversely associated with a lower chance of finding sperm (OR 0.37, 95% CI 0.20 to 0.65, p = 0.001). Compared with small testicular volume, normal volume was inversely associated with the chance of sperm presence (OR 0.16, 95% CI 0.06 to 0.47, p = 0.0002). However, there was no correlation between MND1/GAPDH levels and ICSI outcome.

Conclusion

Gene expression analysis to predict the likelihood of sperm retrieval following mTESE in patients with non-obstructive azoospermia provides a new avenue for future research, diagnosis and treatment of male factor infertility. Before its wider clinical application, however, this proof-of-concept should be tested in a large multinational, multicenter observational study.

Hypertension and reproductive dysfunction: a possible role of inflammation and inflammation-associated lymphangiogenesis in gonads

Hypertension is one of the most prevalent diseases that leads to end organ damage especially affecting the heart, kidney, brain, and eyes. Numerous studies have evaluated the association between hypertension and impaired sexual health, in both men and women. The detrimental effects of hypertension in men includes erectile dysfunction, decrease in semen volume, sperm count and motility, and abnormal sperm morphology. Similarly, hypertensive females exhibit decreased vaginal lubrication, reduced orgasm, and several complications in pregnancy leading to fetal and maternal morbidity and mortality. The adverse effect of hypertension on male and female fertility is attributed to hormonal imbalance and changes in the gonadal vasculature. However, mechanistic studies investigating the impact of hypertension on gonads in more detail on a molecular basis remain scarce. Hence, the aim of the current review is to address and summarize the effects of hypertension on reproductive health, and highlight the importance of research on the effects of hypertension on gonadal inflammation and lymphatics.

Gene alterations and expression spectrum of SPATA33 in nonobstructive azoospermic Iranian men

Genetic abnormalities have been considered a significant cause of male infertility. Increased expression of SPATA33 during the first wave of spermatogenesis indicates its possible association with the meiotic process. The aim of the current study was to investigate the genetic variations in the SPATA33 gene and its expression in patients with nonobstructive azoospermia (NOA). A total of 100 Iranian NOA men with idiopathic infertility were taken as the case group. The control group comprised 100 fertile men who had at least one child. The presence of nucleotide variations was analyzed in both groups using the standard polymerase chain reaction (PCR) sequencing technique. For mRNA and protein expression studies, testicular biopsy specimens from 27 patients were subdivided into three groups: nine obstructive azoospermic patients with hypospermatogenesis as control; nine maturation arrest (MA) and nine Sertoli cell-only syndromes (SCOS) as case groups. The expression of SPATA33 at both mRNA and protein levels was compared among these three groups using the reverse transcription PCR technique, the realtime-PCR technique, and immunohistochemistry. Mutation analysis of the SPATA33 gene revealed five nucleotide changes among the population studied. All but one showed no significant differences between the groups. The genotype distributions of rs112536073A > T in the transcription factor binding site region with heterozygote and homozygote genotypes were significantly different ( p < 0.05) between the two groups. More heterozygotes of this polymorphism were observed in patients, whereas more homozygotes were detected in controls. Accordingly, the current study illustrated that alterations in SPATA33 gene, at least those found in this study, may not impair spermatogenesis in patients with NOA. Reduction of gene expression at the level of mRNA in patients with SCOS can be interpreted by the absence of germ cells in the testicular tissue of these patients.

New transcriptomic tools to understand testis development and functions

The testis plays a central role in the male reproductive system - secreting several hormones including male steroids and producing male gametes. A complex and coordinated molecular program is required for the proper differentiation of testicular cell types and maintenance of their functions in adulthood. The testicular transcriptome displays the highest levels of complexity and specificity across all tissues in a wide range of species. Many studies have used high-throughput sequencing technologies to define the molecular dynamics and regulatory networks in the testis as well as to identify novel genes or gene isoforms expressed in this organ. This review intends to highlight the complementarity of these transcriptomic studies and to show how the use of different sequencing protocols contribute to improve our global understanding of testicular biology.

Recent advances in the genetics of testicular failure

Infertility affects approximately 15% of couples, and male factor is responsible for 30%-50% of all infertility. The most severe form of male infertility is testicular failure, and the typical phenotype of testicular failure is severely impaired spermatogenesis resulting in azoospermia or severe oligozoospermia. Although the etiology of testicular failure remains poorly understood, genetic factor typically is an underlying cause. Modern assisted reproductive techniques have revolutionized the treatment of male factor infertility, allowing biological fatherhood to be achieved by many men who would otherwise have been unable to become father to their children through natural conception. Therefore, identifying genetic abnormalities in male is critical because of the potential risk of transmission of genetic abnormalities to the offspring. Recently, along with other intense researches ongoing, whole-genome approaches have been used increasingly in the genetic studies of male infertility. In this review, we focus on the genetics of testicular failure and provide an update on the advances in the study of genetics of male infertility.

Integrated miRNA and mRNA expression profiling to identify mRNA targets of dysregulated miRNAs in non-obstructive azoospermia

The aim of this study was to identify mRNA targets of dysregulated miRNAs through the integrated analysis of miRNA and mRNA expression profiling in men with normal versus impaired spermatogenesis. The expression of mRNAs and miRNAs in testicular tissues obtained from males with non-obstructive azoospermia (NOA, n = 4) or obstructive azoospermia (OA, n = 3) with normal spermatogenesis was analyzed using microarray technology. Some of the most interesting results were validated by real time PCR using samples from the same cohort. Ninety-three miRNAs and 4172 mRNAs were differentially expressed in the NOA and normozoospermic OA patients. In addition to confirming that significantly dysregulated genes and miRNAs play pivotal roles in NOA, promising correlation signatures of these miRNA/mRNA pairs were discovered in this study. The functional classification of the miRNA/mRNA pairs revealed that differentially expressed genes were most frequently associated with spermatogenesis, the cell meiosis, the cell cycle, and the development of secondary male sexual characteristics. This is the first systematic profiling of both mRNA and miRNA in testicular tissues of patients with NOA and OA. Our results indicate that the phenotypic status of NOA is characterized by the dysfunction of normal spermatogenesis when compared with OA or normozoospermic males.

Altered gene expression signature of early stages of the germ line supports the pre-meiotic origin of human spermatogenic failure

The molecular basis of spermatogenic failure (SpF) is still largely unknown. Accumulating evidence suggests that a series of specific events such as meiosis, are determined at the early stage of spermatogenesis. This study aims to assess the expression profile of pre-meiotic genes of infertile testicular biopsies that might help to define the molecular phenotype associated with human deficiency of sperm production. An accurate quantification of testicular mRNA levels of genes expressed in spermatogonia was carried out by RT-qPCR in individuals showing SpF owing to germ cell maturation defects, Sertoli cell-only syndrome or conserved spermatogenesis. In addition, the gene expression profile of SpF was compared with that of testicular tumour, which is considered to be a severe developmental disease of germ cell differentiation. Protein expression from selected genes was evaluated by immunohistochemistry. Our results indicate that SpF is accompanied by differences in expression of certain genes associated with spermatogonia in the absence of any apparent morphological and/or numerical change in this specific cell type. In SpF testicular samples, we observed down-regulation of genes involved in cell cycle (CCNE1 and POLD1), transcription and post-transcription regulation (DAZL, RBM15 and DICER1), protein degradation (FBXO32 and TM9SF2) and homologous recombination in meiosis (MRE11A and RAD50) which suggests that the expression of these genes is critical for a proper germ cell development. Interestingly, a decrease in the CCNE1, DAZL, RBM15 and STRA8 cellular transcript levels was also observed, suggesting that the gene expression capacity of spermatogonia is altered in SpF contributing to an unsuccessful sperm production. Altogether, these data point to the spermatogenic derangement being already determined at, or arising in, the initial stages of the germ line.

Semen analysis: update on clinical value, current needs and future perspectives

At present, evaluation of male reproductive function consists primarily of routine semen analysis, a collection of conventional microscopic assessments ideally performed following the guidelines set by the World Health Organization. While providing some insight into testicular function, these long-performed tests are limited in the information that they impart; more specifically, they are unable to predict true fertility potential. As a consequence, there is a need for the appraisal and consideration of newer semen parameters that may be more indicative of reproductive success. Although various novel assays have been introduced that broaden the scope of information available to both researcher and clinician, the utility of these tests remains limited due to the lack of standardisation of protocols and the absence of clinically established, dependable reference ranges. As such, it is not surprising that most of these parameters and their associated methods remain recommended for ‘research purposes only’. With the burgeoning ‘omics’ revolution, nanotechnology and the development of new analytical instruments, there is now an opportunity for the identification and measurement of previously unknown features that may prove to be more indicative of each sperm's true functional status and capability. Once optimised, simplified, clinically validated and made more readily accessible, these new approaches hold the promise of forming the fulcrum upon which andrological investigations can enter a new era.

Potential biomarkers of nonobstructive azoospermia identified in microarray gene expression analysis

OBJECTIVE

To identify potential biomarkers of azoospermia to determine a particular stage of spermatogenetic differentiation.

DESIGN

GeneChip Human Gene 1.0 ST microarray with validation at mRNA and protein levels.

SETTING

Basic research laboratory.

PATIENT(S)

Men with various types of nonobstructive azoospermia (n = 18) and with normal spermatogenesis (n = 4).

INTERVENTION(S)

Obtaining 31 testicular biopsy samples.

MAIN OUTCOME MEASURE(S)

Gene expression analysis using the Affymetrix Human Gene 1.0 ST microarrays on 14 selected genes according to the highest fold change, verified with quantitative polymerase chain reaction and on independent set of microarray samples. Western blot and immunohistochemistry were additionally performed.

RESULT(S)

The comparative analysis of gene expression profiles in the infertile and control groups resulted in the selection of 4,946 differentially expressed genes. AKAP4, UBQLN3, CAPN11, GGN, SPACA4, SPATA3, and FAM71F1 were the most significantly down-regulated genes in infertile patients. Global analysis also led to identification of up-regulated genes-WBSCR28, ADCY10, TMEM225, SPATS1, FSCN3, GTSF1L, and GSG1-in men with late maturation arrest. Moreover, the results from quantitative polymerase chain reaction and Western blot largely confirmed the microarray data.

CONCLUSION(S)

The set of selected genes can be used to create a molecular diagnostic tool to determine the degree of spermatogenic impairment for men with idiopathic nonobstructive azoospermia.

Expression analysis of MND1/GAJ, SPATA22, GAPDHS and ACR genes in testicular biopsies from non-obstructive azoospermia (NOA) patients

BACKGROUND

High-throughput studies provide a wide spectrum of genes for use as predictive markers during testicular sperm extraction (TESE) in combination with ICSI. In this work, we used the specimens from testicular biopsies of men with non-obstructive azoospermia who underwent TESE to investigate the expression of spermatogenesis-related genes MND1, SPATA22, GAPDHS and ACR.

METHODS

Testicular biopsy specimens were subdivided into three groups: hypospermatogenesis (HS); maturation arrest (MA); and Sertoli cell-only syndrome (SCO). The levels of expression of the spermatogenesis-related genes MND1, SPATA22, GAPDHS and ACR in the testes were compared among these three groups using the reverse transcription polymerase chain reaction (RT-PCR) technique.

RESULTS

Analysis of the expression of spermatogenic genes in human testes with abnormal spermatogenesis showed different expression patterns in patients from different groups. Fertilization rate for studied set of patients was 66% and pregnancy rate 29%. For HS group fertilization rate was 72% and pregnancy rate 32%, while for MA group fertilization and pregnancy rates were 54% and 26%, respectively. Fertilization rates in relation to the studied genes were uniformly around 70%, pregnancy rates for ACR and GAPDHS genes were surprisingly low at 6% and 8% correspondingly.

CONCLUSIONS

Analysis of the expression of genes involved in spermatogenesis can be a fast additional test for the level of spermatogenesis in testicular samples.

Expression and localization of creatine kinase in the preimplantation embryo

Creatine Kinase (CK) catalyses the "creatine shuttle," the reversible conversion of creatine phosphate to creatine with the liberation of ATP. This article examines the potential role of the creatine shuttle in the provision of ATP during mouse preimplantation embryo development. Using quantitative PCR, transcripts of four subunit isoforms of CK--CKM, CKB, CKMT1, and CKMT2--were detectable at all developmental stages, from the presumptive zygote to late blastocyst, but there was no obvious pattern in gene expression. By contrast, total CK biochemical activity, measured by a novel method, was relatively constant from the 2- to 8-cell stage, before exhibiting a significant decrease in activity at the blastocyst stage. Immunocytochemical studies revealed a marked association of CKB with the mitotic spindle in 2- and 4-cell mouse embryos, consistent with the proposition that the creatine shuttle plays a key role in local delivery of ATP during cytokinesis. Endogenous creatine was detected in the blastocyst at a level of 0.53 pmol/embryo. In conclusion, we believe that creatine phosphate can now be added to the list of potential sources of ATP during preimplantation development.

A comprehensive review of genetics and genetic testing in azoospermia

Azoospermia due to obstructive and non-obstructive mechanisms is a common manifestation of male infertility accounting for 10-15% of such cases. Known genetic factors are responsible for approximately 1/3 of cases of azoospermia. Nonetheless, at least 40% of cases are currently categorized as idiopathic and may be linked to unknown genetic abnormalities. It is recommended that various genetic screening tests are performed in azoospermic men, given that their results may play vital role in not only identifying the etiology but also in preventing the iatrogenic transmission of genetic defects to offspring via advanced assisted conception techniques. In the present review, we examine the current genetic information associated with azoospermia based on results from search engines, such as PUBMED, OVID, SCIENCE DIRECT and SCOPUS. We also present a critical appraisal of use of genetic testing in this subset of infertile patients.

Global human tissue profiling and protein network analysis reveals distinct levels of transcriptional germline-specificity and identifies target genes for male infertility

BACKGROUND

Mammalian spermatogenesis is a process that involves a complex expression program in both somatic and germ cells present in the male gonad. A number of studies have attempted to define the transcriptome of male meiosis and gametogenesis in rodents and primates. Few human transcripts, however, have been associated with testicular somatic cells and germ cells at different post-natal developmental stages and little is known about their level of germline-specificity compared with non-testicular tissues.

METHODS

We quantified human transcripts using GeneChips and a total of 47 biopsies from prepubertal children diagnosed with undescended testis, infertile adult patients whose spermatogenesis is arrested at consecutive stages and fertile control individuals. These results were integrated with data from enriched normal germ cells, non-testicular expression data, phenotype information, predicted regulatory DNA-binding motifs and interactome data.

RESULTS

Among 3580 genes for which we found differential transcript concentrations in somatic and germ cells present in human testis, 933 were undetectable in 45 embryonic and adult non-testicular tissues, including many that were corroborated at protein level by published gene annotation data and histological high-throughput protein immunodetection assays. Using motif enrichment analyses, we identified regulatory promoter elements likely involved in germline development. Finally, we constructed a regulatory disease network for human fertility by integrating expression signals, interactome information, phenotypes and functional annotation data.

CONCLUSIONS

Our results provide broad insight into the post-natal human testicular transcriptome at the level of cell populations and in a global somatic tissular context. Furthermore, they yield clues for genetic causes of male infertility and will facilitate the identification of novel cancer/testis genes as targets for cancer immunotherapies.

The bioinformatics tool box for reproductive biology

Genetics and molecular biology have been instrumental for a better understanding of heritable defects causing human infertility over the past decades. More recently, the field of reproductive biology has harnessed genome biological approaches to gain insight into molecular processes underlying normal and pathological gametogenesis and gamete function. We are currently witnessing yet another quantum leap in our ability to monitor the flow of information from the genome via the transcriptome to the proteome: tiling arrays that cover both strands of a given target genome and RNA-Seq, a method based on ultra-high throughput DNA sequencing, enable us to study noncoding and protein-coding transcripts with unprecedented precision and depth at a reasonable cost. These technologies have spawned a thriving discipline within the bioinformatics field that employs information technology for managing and interpreting biological high-throughput data. This review outlines database projects and online analysis tools useful for life scientists in general and discusses in detail selected projects that have specifically been developed for researchers and clinicians in the field of reproductive biology. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure.

Key functional genes of spermatogenesis identified by microarray analysis

At present many couples face difficulties when trying to conceive that may have a genetic basis. The male factor is the cause of infertility as often as the female. Therefore it is important to identify key genes involved in spermatogenesis which may be linked to male infertility. This review discusses the identification of a range of genes associated with male fertility using microarrays. Based on differences in gene expression profiles between fertile and infertile male subgroups or between fetal and adult male gonads, many genes important for spermatogenesis have been discovered. Genes that are critical at particular stages of spermatogenesis were defined and can be considered as potential male fertility biomarkers. The studies described showed that microarrays may be potentially used as a diagnostic platform to increase the efficacy of diagnosis and perhaps treatment of infertile males.

A biopsy sample reduction approach to identify significant alterations of the testicular transcriptome in the presence of Y-chromosomal microdeletions that are independent of germ cell composition

Y-chromosomal microdeletions (YCMD) are the major genetic cause of male infertility. To date, it is not known which global changes are induced by the presence of AZFc or AZFb + c deletions in the human testicular transcriptome. We investigated this question by microarray analysis in which we had to eliminate the ‘germ cell effect’, i.e., the dominating effect of germ cell transcripts due to the quantitative difference in germ cell composition in samples with/without YCMD. This problem was tackled by selecting 26 samples from an initial cohort of 34 samples by their homogeneity in respect to cellular composition as obtained from gene expression clustering. This way, the ‘germ cell effect’ was minimized, and a distinct ‘deletion effect’ became more apparent. Several hundred genes are influenced by YCMD as shown on the three different phenotypes hypospermatogenesis, meiotic arrest, and Sertoli-cell only syndrome. We validated on an independent cohort of samples five genes by quantitative real-time PCR that are expressed in germ cells or the somatic compartment and which are exclusively altered by the presence of YCMD. We conclude that the deletion of Y-chromosomal genes has a significant effect on spermatogenesis by modulating the transcriptional network of the germ cell and somatic compartment.

The human RPS4 paralogue on Yq11.223 encodes a structurally conserved ribosomal protein and is preferentially expressed during spermatogenesis

Background

The Y chromosome of mammals is particularly prone to accumulate genes related to male fertility. However, the high rate of molecular evolution on this chromosome predicts reduced power to the across-species comparative approach in identifying male-specific genes that are essential for sperm production in humans. We performed a comprehensive analysis of expression of Y-linked transcripts and their X homologues in several human tissues, and in biopsies of infertile patients, in an attempt to identify new testis-specific genes involved in human spermatogenesis.

Results

We present evidence that one of the primate-specific Y-linked ribosomal protein genes, RPS4Y2, has restricted expression in testis and prostate, in contrast with its X-linked homologue, which is ubiquitously expressed. Moreover, we have determined by highly specific quantitative real time PCR that RPS4Y2 is more highly expressed in testis biopsies containing germ cells. The in silico analysis of the promoter region of RPS4Y2 revealed several differences relative to RPS4Y1, the more widely expressed paralogue from which Y2 has originated through duplication. Finally, through comparative modelling we obtained the three dimensional models of the human S4 proteins, revealing a conserved structure. Interestingly, RPS4Y2 shows different inter-domain contacts and the potential to establish specific interactions.

Conclusions

These results suggest that one of the Y-linked copies of the ribosomal protein S4 is preferentially expressed during spermatogenesis and might be important for germ cell development. Even though RPS4Y2 has accumulated several amino acid changes following its duplication from RPS4Y1, approximately 35 million years ago, the evolution of the Y-encoded RPS4 proteins is structurally constrained. However, the exclusive expression pattern of RPS4Y2 and the novelties acquired at the C-terminus of the protein may indicate some degree of functional specialisation of this protein in spermatogenesis.

The genetic causes of male factor infertility: a review

OBJECTIVE

To illustrate the necessity for an enhanced understanding of the genetic basis of male factor infertility, to present a comprehensive synopsis of these genetic elements, and to review techniques being utilized to produce new insights in fertility research.

BACKGROUND

Male factor infertility is a complex disorder that affects a large sector of the population; however, many of its etiologies are unknown. By elucidating the underlying genetic basis of infertile phenotypes, it may be possible to discover the causes of infertility and determine effective treatments for patients.

METHOD(S)

The PubMed database was consulted for the most relevant papers published in the last 3 years pertaining to male factor infertility using the keywords "genetics" and "male infertility."

RESULT(S)

Advances have been made in the characterization of the roles of specific genes, but further research is necessary before these results can be used as guidelines for diagnosing and treating male factor infertility. The accurate transmission of epigenetic information also has considerable influence on fertility in males and on the fertility of their offspring.

CONCLUSION(S)

Analysis of the genetic factors that impact male factor infertility will provide valuable insights into the creation of targeted treatments for patients and the determination of the causes of idiopathic infertility. Novel technologies that analyze the influence of genetics from a global perspective may lead to further developments in the understanding of the etiology of male factor infertility through the identification of specific infertile phenotype signatures.

Transcriptional profiling of luteinizing hormone receptor-deficient mice before and after testosterone treatment provides insight into the hormonal control of postnatal testicular development and Leydig cell differentiation

Luteinizing hormone (LH) is a key regulator of male fertility through its effects on testosterone secretion by Leydig cells. Transcriptional control of this is, however, currently poorly understood. Mice in which the LH receptor is knocked out (LuRKO) show reduced testicular size, reduced testosterone, elevated serum LH, and a spermatogenic arrest that can be rescued by the administration of testosterone. Using genome-wide transcription profiling of LuRKO and control testes during postnatal development and following testosterone treatment, we show that the transcriptional effects of LH insensitivity are biphasic, with an early testosterone-independent phase and a subsequent testosterone-dependent phase. Testosterone rescue re-enables the second, testosterone-dependent phase of the normal prepubertal transcription program and permits the continuation of spermatogenesis. Examination of the earliest responses to testosterone highlights six genes that respond rapidly in a dose-dependent fashion to the androgen and that are therefore candidate regulatory genes associated with the testosterone-driven progression of spermatogenesis. In addition, our transcriptional data suggest a model for the replacement of fetal-type Leydig cells by adult-type cells during testicular development in which a testosterone feedback switch is necessary for adult Leydig cell production. LH signaling affects the timing of the switch but is not a strict requirement for Leydig cell differentiation.

Unravelling the genetics of spermatogenic failure

Subfertility, defined as the inability to conceive within 1 year of unprotected intercourse, affects 10–15% of couples. In up to 55% of couples, the male partner is diagnosed with spermatogenic failure, i.e. one or more semen parameters fall below the WHO criteria for normozoospermia. In these cases, assisted reproductive technology is usually used to achieve pregnancy. Both genetic and environmental factors are thought to underlie spermatogenic failure. Despite years of research, only few genetic factors have clearly been shown to cause spermatogenic failure, and the identification of additional genetic causes or risk factors has proven to be extremely difficult. In this review, we will present an overview of established genetic causes of spermatogenic failure, describe pitfalls in searching for novel genetic factors and discuss research opportunities for the future.

Gene expression profiling in porcine maternal infanticide: a model for puerperal psychosis

The etiology of mental disorders remains largely unclear. Complex interactions between genetic and environmental factors are key to the development of such disorders. Puerperal psychosis is the most extreme form of postnatal mood disorder in women. Similarly, parturition in the pig can trigger extreme behavioral disturbances, including maternal infanticide. In this study, we have used a targeted cDNA microarray approach using the pig as a model to understand the genes and genetic pathways that are involved in these processes. Two subtracted cDNA libraries from porcine hypothalamus were constructed, which were enriched for genes that were over-expressed and under-expressed in the aberrant behavioral phenotype, compared to the matched control. In addition to this, a normalized library was constructed from hypothalamus and pituitary samples taken from pigs in a variety of reproductive states. The libraries were partially sequenced and combined represented approximately 5,159 different genes. Microarray analysis determined differences in gene expression between hypothalamus samples from nine matched pairs of infanticidal versus control animals, using a common reference design. Microarray analysis of variance (MAANOVA) identified 52 clones as being differentially expressed (P <or= 0.002) in the infanticide phenotype, a second analysis with friendly statistics package for microarray analysis (FSPMA) identified 9 genes in common to MAANOVA, and a further 16 genes. A rapid cross-species screen onto a human oligonucleotide array confirmed 3 genes and highlighted 61 more potential candidates. Some of these genes and the pathways in which they are involved were also implicated in a parallel QTL study on maternal infanticide.