Messenger RNA transcripts of the meiotic regulator BOULE in the testis of azoospermic men and their application in predicting the success of sperm retrieval

Proteome Profiling of Canine Epididymal Fluid: In Search of Protein Markers of Epididymal Sperm Motility

Sperm maturation in the epididymis is based on interactions with proteins from epididymal fluid (EF). The aim of the study was to profile canine EF proteome and investigate correlations between EF protein content and epididymal spermatozoa (ES) motion parameters. Twenty-three male dogs were divided into two groups: good sperm motility (GSM) and poor sperm motility (PSM). The total motility and progressive motility differed significantly (p = 0.031; p < 0.001, respectively) between the GSM group and the PSM group. The semen samples were centrifuged to separate the EF apart from the ES. The canine EF proteins were analyzed using nano-liquid chromatography, which was coupled with quadrupole time-of-flight mass spectrometry (NanoUPLC-Q-TOF/MS) and bioinformatic tools for the first time. A total of 915 proteins were identified (GSM-506; PSM-409, respectively). UniProt identification resulted in six unique proteins (UPs) in the GSM group of dogs and four UPs in the PSM group. A semi-quantitative analysis showed a higher abundance (p < 0.05) of four differentially expressed proteins in the GSM group (ALB, CRISP2, LCNL1, PTGDS). Motility-dependent variations were detected in the EF proteome and were related to important metabolic pathways, which might suggest that several proteins could be potential ES motility biomarkers.

Molecular characterization and functional analysis of Esr1 and Esr2 in gonads of Chinese soft-shelled turtle (Pelodiscus sinensis)

Estrogens and their receptors play crucial roles in regulating the gonadal development of vertebrates. To clarify the roles of estrogen receptors in the gonadal development of turtles, estrogen receptors (Esr1 and Esr2) in Chinese soft-shelled turtle (Pelodiscus sinensis) were identified and characterized, and their function in gonads was investigated by intraperitoneal injection of agonist propylpyrazoletriol (PPT) and diarylpropionitrile (DPN), and antagonist ICI 182,780 (ICI). Ps-Esr1 encoded a 588 amino acid protein and Ps-Esr2 encoded a 556 amino acid protein. The two receptors contained classic domains, including the DNA-binding domain and ligand-binding domain, and amino acid sequences showed high homology with other turtles. Ps-Esr1 showed the highest expression in the testis, followed by the ovary and liver. However, Ps-Esr2 showed the highest expression in the ovary, followed by the brain and testis. Ps-Esr1 expression showed an up-regulation trend in gonadal differentiation. Histomorphometric analysis showed that the number of follicles increased in female juvenile turtles treated with DPN or PPT. In addition, Tsc2, GnRH, and Fshβ were up-regulated in ovaries of turtles treated with agonists, while Sycp3 and Picalm were up-regulated in testes of turtles treated with agonists. Treatment with the antagonist decreased the number of sperm in matured turtles. Stra8, Scyp3, Dmc1, Picalm, Evl, Boule, and Cdk1 were up-regulated in testis after antagonist treatment. The results indicated that Esr1 might play an important role in gonadal differentiation, and the two estrogen receptors might be involved in the spermatogenesis of the turtle. These results could provide a reference for further research on the function of the estrogen signal in male vertebrates.

Multi-stage screening cell-free seminal mRNAs to diagnose completion of meiosis and predict testicular sperm retrieval in men with non-obstructive azoospermia

BACKGROUND

Differential diagnosis of men with subtypes of non-obstructive azoospermia (NOA) is important for their treatment. Many genes are transcripted during meiosis. We hypothesized that some of these genes can be detected in cell-free seminal mRNAs (cfs-mRNA) and be developed as non-invasive biomarkers for diagnosing NOA subtypes.

OBJECTIVE

To screen cfs-mRNA to diagnose the completion of meiosis and predict successful sperm retrieval (SR) in men with NOA.

MATERIALS AND METHODS

NOA patients who visited our institutes from September 2018 to December 2020 for testicular histopathological diagnosis (n = 109) or testicular SR (n = 92) were screened for participation in the study. Microarray and real-time quantitative PCR were used in five stages to obtain candidate cfs-mRNAs for comparisons between patients with early maturation arrest (eMA, meiosis not completed) and late MA or hypospermatogenesis (meiosis completed), and between NOA patients with successful SR and SR failure.

RESULTS

Twelve cfs-mRNAs were selected based on this comparison between men with eMA and hypospermatogenesis and their gene expression and function information. Of these, AKAP1, BOLL, TCP11, and SETX predominantly derived from testes and germ cells were proposed as candidate cfs-mRNAs. Further quantification in men with NOA demonstrated significantly higher levels of BOLL cfs-mRNA (P < 0.0001) in men with late MA or hypospermatogenesis (n = 23), compared with men with eMA (n = 51); and significantly higher levels (P < 0.0001) in patients with successful SR (n = 44) when compared with patients with SR failure (n = 37). Interestingly, with a similar cutoff value, BOLL cfs-mRNA showed high sensitivity and specificity in diagnosing late MA and hypospermatogenesis (>404 copies/mL) and predicting successful SR (>415 copies/mL). Correlation of BOLL mRNA levels was observed in paired semen and testicular tissues.

DISCUSSION AND CONCLUSIONS

We propose that BOLL cfs-mRNA is a promising non-invasive marker for diagnosing the completion of meiosis and predicting successful testicular SR in men with NOA. This article is protected by copyright. All rights reserved.

TXNDC2 joint molecular marker is associated with testis pathology and is an accurate predictor of sperm retrieval

The association of PRM1/2 with male azoospermia is well-documented, but the relationship between TXNDC2 deficiency and the azoospermia phenotype, sperm retrieval, and pathology has not been elucidated. Here we identified the association of TXNDC2 and protamines in evaluating testis pathology and sperm retrieval. An extensive microarray meta-analysis of men with idiopathic azoospermia was performed, and after undergoing several steps of data quality controls, the data passing QC were pooled and batch effect corrected. As redox imbalance has been shown to have a variable relationship with fertility, our relative expression studies began with candidate protamination and thioredoxin genes. We constructed a logistic regression model of TXNDC2 with PRM1 and PRM2 genes, and collective ROC analysis indicated a sensitivity of 96.8% and specificity of 95.5% with a ROC value of 0.995 (SE = 0.0070, 95% CI 0.982-1.000). These results demonstrate that TXNDC2, PRM1, and PRM2 combined have a robust power to predict sperm retrieval and correlate with severe azoospermia pathology.

Deficient Expression of DGCR8 in Human Testis is Related to Spermatogenesis Dysfunction, Especially in Meiosis I

Introduction

DiGeorge syndrome critical region gene 8 (DGCR8) contributes to miRNA biogenesis, and defects in its expression could lead to defects in spermatogenesis.

Methods

Here, we assess gene and protein expression levels of DGCR8 in the testicular biopsy specimens obtained from men with obstructive azoospermia (OA, n = 19) and various types of non-obstructive azoospermia (NOA) including maturation arrest (MA, n = 17), Sertoli cell-only syndrome (SCOS, n = 20) and hypospermatogenesis (HYPO, 18). Also, samples of men with NOA were divided into two groups based on successful and unsuccessful sperm recovery, NOA+ in 21 patients and NOA− in 34 patients.

Results

Examinations disclosed a severe decrease in DGCR8 in samples with MA and SCOS in comparison to OA samples (P < 0.001). Also, the results showed DGCR8 has significantly lower expression in testis tissues of NOA− group in comparison to NOA+ group (p<0.05). Western blot analysis confirmed that the DGCR8 protein was not expressed in SCOS samples and had a very low expression in MA and HYPO samples.

Discussion

The results of this survey showed that DGCR8 is an important gene for the entire spermatogenesis pathway. Moreover, DGCR8 gene plays an important role in the diagnosis of NOA subgroups, and also the expression changes in it might contribute to SCOS or MA phenotypes. This gene with considering other related genes can also be a predictor of sperm retrieval.

Identification and characterization of DAZ family genes in Chinese soft-shell turtle (Pelodiscus sinensis)

The DAZ family genes, including boule, dazl, and daz, play pivotal roles in germ cell development and differentiation during gametogenesis in organisms, which have been widely studied in mammals, reptiles, or fishes. Dazl was bisexual expressed in both mitotic and meiotic germ cells, daz was male premeiotic expressed, whereas boule exhibits largely in unisexual meiotic germ cells but bisexual expression in several fishes, however, there is lack of report on boule gene and the evolutionary conservation and divergence of dazl and boule in reptile. Here, both boule and dazl genes were characterized in Pelodiscus sinensis. The quantitative real-time polymerase chain reaction analysis showed that boule and dazl were abundantly expressed in adult ovary and testis but barely in somatic tissues, such as heart, brain, liver, spleen, and kidney. Moreover, through fluorescent in situ hybridization, bisexual and germline-specific expression profiles of boule and dazl messenger RNAs (mRNAs) were demonstrated. Boule mRNA exhibited a maximal meiotic expression in spermatocytes, and a relatively low, but distinct expression in oocytes at meiotic stages in P. sinensis, similar to the expression profile of human boule in ovary. However, dazl mRNA was richly distributed in male germ cells at almost all stages during spermatogenesis, and predominantly expressed in most of stages of oocytes including premeiotic and meiotic stages. These findings imply that boule and dazl would play distinct roles in the sexual differentiation of germ cells during turtle gametogenesis, and the major functions of daz family members involved in germ cell differentiation would be conserved across species including P. sinensis.

Histomorphological Comparisons and Expression Patterns of BOLL Gene in Sheep Testes at Different Development Stages

BOLL is implicated in mammalian testicular function maintenance and spermatogenesis. To understand the expression patterns and biological functions of sheep BOLL, we examined the expression and immunolocalization of BOLL in the developing testes of Small-Tail Han sheep aged 0 days (D0), 2 months (2M), 5 months (5M), 1 year (1Y), and 2 years (2Y), by qPCR, Western blot, and immunohistochemistry methods. Firstly, morphological studies revealed that, in addition to spermatogonia, ordered and clear spermatocytes, as well as round and elongated spermatids and sperm, were found in the 1Y and 2Y testicular seminiferous tubules of the sheep testes, compared with the D0, 2M, and 5M testes, as analyzed by hematoxylin and eosin (H&amp;E) staining. The diameter and area of the seminiferous tubules, epithelial thickness, and the area and perimeter of the tubule lumens gradually increased with age. BOLL was specifically expressed in testes and upregulation of BOLL transcript expression was higher in the testes of the 1Y and 2Y groups than in those of the D0, 2M, and 5M groups. Similarly, BOLL protein was expressed mainly in the 1Y and 2Y testes, ranging from primary spermatocytes to round spermatids, as well as in the spermatozoa. This study is the first demonstration that sheep BOLL might serve as a key regulator of the spermiogenesis involved in sperm maturity, in addition to its role as a crucial meiotic regulator.

Distinctive pattern of expression of spermatogenic molecular markers in testes of azoospermic men with non-mosaic Klinefelter syndrome

PURPOSE

Mature sperm cells can be found in testicular specimens extracted from azoospermic men with non-mosaic Klinefelter syndrome (KS). The present study evaluates the expression of various known molecular markers of spermatogenesis in a population of men with KS and assesses the ability of those markers to predict spermatogenesis.

METHODS

Two groups of men with non-obstructive azoospermia who underwent testicular sperm-retrieval procedures were included in the study: 31 had non-mosaic KS (KS group) and 91 had normal karyotype (NK group). Each group was subdivided into mixed atrophy (containing some mature sperm cells) or Sertoli cell only syndrome according to testicular histology and cytology observations. Semi-quantitative histological morphometric analysis (interstitial hyperplasia and hyalinization, tubules with cells and abnormal thickness of the basement membrane) and expression of spermatogenetic markers (DAZ, RBM, BOLL, and CDY1) were evaluated and compared among those subgroups.

RESULTS

Clear differences in the histological morphometry and spermatogenetic marker expression were noted between the KS and NK groups. There was a significant difference in the expression of spermatogenetic markers between the subgroups of the NK group (as expected), while no difference could be discerned between the two subgroups in the KS group.

CONCLUSION

We conclude that molecular spermatogenetic markers have a pattern of expression in men with KS that is distinctively different from that of men with NK, and that it precludes and limits their use for predicting spermatogenesis in the former. It is suggested that this difference might be due to the specific highly abnormal histological morphometric parameters in KS specimens.

Oncogenic Role of BOLL in Colorectal Cancer

BACKGROUND

Boule-like RNA-binding protein (BOLL protein) is the progenitor of the Deleted in Azoospermia (DAZ) gene family. To date, previous studies have focused on the reproductive function of BOLL. While we were identifying new DNA methylation biomarkers for colorectal cancer (CRC), we found that BOLL protein was overexpressed in CRC.

AIM

The aim of this study was to determine the role of BOLL in CRC by epigenetic and functional studies in vivo and in vitro.

METHODS

BOLL promoter methylation and expression were determined by MethyLight, RT-PCR, Western blot, and immunohistochemistry. The functional role of BOLL in CRC was evaluated by cell proliferation, colony formation, migration and invasion, cell cycle status, and tumor growth in a xenograft model.

RESULTS

BOLL promoter methylation was enhanced in CRC tissues compared with normal colorectal tissues [97/124 (78 %) vs. 2/124 (2 %)]. However, the mean immunoreactivity score of CRC tissues and paired adjacent normal tissues was 8.15 ± 0.18 (SD) and 3.35 ± 0.19 (SD), respectively (p < 0.01). No significant association was observed between immunoreactivity score and clinicopathological parameters, including age, gender, tumor size, tumor differentiation, and tumor node metastasis stage. Expression of BOLL in CRC cell lines significantly enhanced cell proliferation (p < 0.01), colony formation (p < 0.01), and migration (p < 0.01). In BOLL-expressing cells, the percentage of cells in S-phase of the cell cycle was significantly increased. Tumor volume in BOLL xenografted mice was significantly enhanced after subcutaneous implantation (p < 0.01).

CONCLUSIONS

Our study demonstrated an oncogenic role of BOLL in CRC despite tumor-specific promoter hypermethylation.

Epigenetic regulation of bovine spermatogenic cell-specific gene boule

Non-primate mammals have two deleted azoospermia (DAZ) family genes, DAZL and Boule; genes in this family encode RNA-binding proteins essential for male fertility in diverse animals. Testicular DAZL transcription is regulated by epigenetic factors such as DNA methylation. However, nothing is known about the epigenetic regulation of Boule. Here, we explored the role of DNA methylation in the regulation of the bovine Boule (bBoule) gene. We found that a long CpG island (CGI) in the bBoule promoter was hypermethylated in the testes of cattle-yak hybrids with low bBoule expression, whereas cattle had relatively low methylation levels (P < 0.01), and there was no difference in the methylation level in the short CGI of the gene body between cattle and cattle-yak hybrids (P > 0.05). We identified a 107 bp proximal core promoter region of bBoule. Intriguingly, the differences in the methylation level between cattle and cattle-yak hybrids were larger in the core promoter than outside the core promoter. An in vitro methylation assay showed that the core promoter activity of bBoule decreased significantly after M.SssI methylase treatment (P < 0.01). We also observed dramatically increased bBoule transcription in bovine mammary epithelial cells (BMECs) after treatment with the methyltransferase inhibitor 5-Aza-dC. Taken together, our results establish that methylation status of the core promoter might be involved in testicular bBoule transcription, and may provide new insight into the epigenetic regulation of DAZ family genes and clinical insights regarding male infertility.

Identification and characterization of yak (Bos grunniens) b-Boule gene and its alternative splice variants

Boule is responsible for meiotic arrest of sperms and male sterility during mammalian spermatogenesis. In the present study, we first identified yak b-Boule gene and its two alternative splice variants. The full length coding region of yak b-Boule is 888bp and encodes a 295-amino acid protein with a typical RNA-recognition motif (RRM) and a Deleted in Azoospermia (DAZ) repetitive sequence motif. Two alternative splice variants of yak b-Boule were generated following the consensus "GT-AG" rule and named b-Boule1 (36bp deletion in exon 3) and b-Boule2 (deletion of integral exon 7), respectively. In male yak, b-Boule, b-Boule1 and b-Boule2 were found to be exclusively expressed in the testes at a ratio of 81:0.1:1. Intriguingly, the mRNA expression levels of b-Boule and b-Boule1 in yak testis were significantly higher than those in cattle-yak, although no significant difference was observed for b-Boule2 expression between the yak and cattle-yak. These results suggest that b-Boule gene, which is partially regulated by alternative splicing, may be involved in the process of yak spermatogenesis.

Expression pattern of Boule in dairy goat testis and its function in promoting the meiosis in male germline stem cells (mGSCs)

Boule is a conserved gene in meiosis, which encodes RNA binding protein required for spermatocyte meiosis. Deletion of Boule was found to block meiosis in spermatogenesis, which contributes to infertility. Up to date, the expression and function of Boule in the goat testis are not known. The objectives of this study were to investigate the expression pattern of Boule in dairy goat testis and their function in male germline stem cells (mGSCs). The results first revealed that the expression level of Boule in adult testes was significantly higher than younger and immature goats, and azoospermia and male intersex testis. Over-expression of Boule promoted the expression of meiosis-related genes in dairy goat mGSCs. The expression of Stra8 was up-regulated by over-expression of Boule analyzed by Western blotting and Luciferase reporter assay. While, Cdc25a, the downstream regulator of Boule, was found not to affect the expression of Stra8, and our data illustrated that Cdc25a did not regulate meiosis via Stra8. The expression of Stra8 and Boule was up-regulated by RA induction. Taken together, results suggest the Boule plays an important role in dairy goat spermatogenesis and that over-expression of Boule may promote spermatogenesis and meiosis in dairy goat.

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.

The effects of Nanos2 on Boule and Stra8 in male germline stem cells (mGSCs)

The mitosis-meiosis switch is a key event in the differentiation of germ cells. Meiosis is important in development biology, however, it has not been clear what is the regulation mechanism in mammals. Our previous study showed that Boule could activate Stra8 directly and result in the meiosis initiation of dairy goat male germline stem cells (mGSCs). Nanos2, a RNA-binding protein, plays critical roles in the suppression of meiosis by preventing Stra8 expression and maintain the male germ cell development. The main purpose of this study was to explore whether Nanos2 represses Stra8 transcription through Boule or not. We found ectopic over-expression of Nanos2 in GC-1 and mGSCs down-regulated Stra8 transcription and translation, and Boule expression was not affected. It was in consistent with our expectation that RA could up-regulate Boule and Stra8 expression, but down-regulate Nanos2 expression in mGSCs. In dairy goat, the expression levels of Boule and Stra8 would rise with the increase of age, but the expression level of Nanos2 in 90 dpp and adult testis had not shown a clear change. In conclusion, Nanos2 represses Stra8 expression but not through Boule in dairy goat mGSCs.

Epigenetic disruption of the PIWI pathway in human spermatogenic disorders

Epigenetic changes are involved in a wide range of common human diseases. Although DNA methylation defects are known to be associated with male infertility in mice, their impact on human deficiency of sperm production has yet to be determined. We have assessed the global genomic DNA methylation profiles in human infertile male patients with spermatogenic disorders by using the Infinium Human Methylation27 BeadChip. Three populations were studied: conserved spermatogenesis, spermatogenic failure due to germ cell maturation defects, and Sertoli cell-only syndrome samples. A disease-associated DNA methylation profile, characterized by targeting members of the PIWI-associated RNA (piRNA) processing machinery, was obtained. Bisulfite genomic sequencing and pyrosequencing in a large cohort (n = 46) of samples validated the altered DNA methylation patterns observed in piRNA-processing genes. In particular, male infertility was associated with the promoter hypermethylation-associated silencing of PIWIL2 and TDRD1. The downstream effects mediated by the epigenetic inactivation of the PIWI pathway genes were a defective production of piRNAs and a hypomethylation of the LINE-1 repetitive sequence in the affected patients. Overall, our data suggest that DNA methylation, at least that affecting PIWIL2/TDRD1, has a role in the control of gene expression in spermatogenesis and its imbalance contributes to an unsuccessful germ cell development that might explain a group of male infertility disorders.

Sperm DNA fragmentation index does not correlate with the sperm or embryo aneuploidy rate in recurrent miscarriage or implantation failure patients

BACKGROUND

The aneuploidy rate is higher in poor-quality sperm samples, which also have higher DNA fragmentation index values. The aim of this study was to assess the relationship between sperm DNA fragmentation in samples from infertile men belonging to couples with recurrent miscarriage or implantation failure and the aneuploidy rate in spermatozoa as well as in embryos from patients.

METHODS

This prospective study evaluated DNA damage and the aneuploidy rate in fresh and processed (density gradient centrifugation) ejaculated sperm as well as the aneuploidy rate in biopsied embryos from fertility cycles. Fluorescence in situ hybridization was used for the aneuploidy analysis. Results were compared using linear regression and analysis of variance.

RESULTS

A total of 154 embryos were evaluated from 38 patients undergoing PGD cycles; 35.2% of the embryos were chromosomally normal. Analysis of the same sperm samples showed an increased DNA fragmentation after sperm preparation in 76% of the patients. There was no correlation between DNA fragmentation and the aneuploidy rate in embryos or in fresh or processed sperm samples.

CONCLUSIONS

Sperm DNA fragmentation is not related to chromosomal anomalies in embryos from patients with recurrent miscarriage or implantation failure. However, we cannot rule out the possibility that a relationship between DNA fragmentation and aneuploidy exists for other causes of infertility. Furthermore, the different methods used to evaluate DNA fragmentation may produce different results.

Posttranscriptional regulation of CDC25A by BOLL is a conserved fertility mechanism essential for human spermatogenesis

CONTEXT

Human BOLL is known as a meiotic regulator, and CDC25A is considered as a potential RNA target of BOLL.

OBJECTIVE

The aim of the study was to clarify the relationship between BOLL and CDC25A expressions in human testes and to explore the mechanism by which BOLL regulates CDC25A.

DESIGN AND SETTING

A prospective experimental study was conducted at a university-based medical center.

PARTICIPANTS AND INTERVENTIONS

BOLL protein, CDC25A mRNA, and CDC25A protein expressions, as well as spermatocyte numbers in the testes of 32 infertile men were measured. The interaction between BOLL protein and CDC25A mRNA was assessed in in vitro studies.

MAIN OUTCOME MEASURES

Protein and RNA expressions, relationships between expression profiles, CDC25A mRNA binding site for BOLL, and the effects of BOLL on CDC25A mRNA stability and translatability were measured.

RESULTS

The protein expressions of BOLL and CDC25A are significantly decreased in patients with spermatogenic failure, with the lowest levels detected in patients with meiotic arrest. Both protein expressions are significantly correlated with spermatocyte numbers. Expressional profiling analysis among BOLL protein, CDC25A mRNA, and CDC25A protein suggests a causal relationship between BOLL and CDC25A. BOLL specifically binds to a 21-nucleotide region of the CDC25A 3'UTR, and this region is evolutionarily conserved. A U-rich region within this 21-nucleotide sequence is crucial for binding. BOLL stimulates CDC25A translation, and this effect does not involve alteration of mRNA stability.

CONCLUSION

CDC25A is subject to translational control by BOLL, which is an evolutionarily conserved mechanism. A decreased CDC25A expression caused by lack or decrease of BOLL may be associated with male infertility.

Association of three isoforms of the meiotic BOULE gene with spermatogenic failure in infertile men

The complex process of spermatogenesis requires the expression and precise coordination of a multitude of genes. Abnormal function of such genes is frequently associated with male infertility. Among these candidates is the human BOULE gene that is a possible fundamental mediator of meiotic transition. In this study, we describe for the first time the existence of three BOULE transcript variants (B1, B2 and B3). We investigated their tissue specificity and mRNA transcript levels in 23 testis biopsies from infertile men. B1, B2 and B3 differed solely in their N-terminal sequences, which are encoded by three alternatively spliced exons 1. In humans, all three isoforms are exclusively expressed in the testes in a relative proportion of 80:220:1 for B1, B2 and B3, respectively. RT-PCR quantification revealed significantly reduced mRNA expression of all three variants in testicular biopsies with meiotic arrest (MA) compared with those with qualitatively complete spermatogenesis. Alteration of the B1/B2 and B1/B3 transcript ratios was correlated with reduced meiotic capacity of spermatocytes to produce round spermatids as assessed by flow cytometry. Furthermore, BOULE mRNA reduction in biopsies with MA paralleled the absence of BOULE protein as analysed by immunohistochemistry. In conclusion, the relative proportions of B1, B2 and B3 may serve as predictive markers for meiotic efficiency and thus the probability of finding haploid cells in the human testis. Among the three isoforms, B2 might have the major role for meiotic completion.

Decreased mRNA transcripts of M-phase promoting factor and its regulators in the testes of infertile men

BACKGROUND

M-phase promoting factor (MPF), which is comprised of Cyclin B and a catalytic subunit, Cdc2, is a key enzyme required for cells to enter M phase in both mitosis and meiosis. MPF activity is controlled by the stimulatory dephosphorylation of the Cdc25 family and the inhibitory phosphorylation of Wee1. We determined the levels of mRNA transcripts of MPF and its regulators in the testes of infertile men, and evaluated the relationship between the transcript levels and patients' testicular phenotypes and sperm retrieval results.

METHODS AND RESULTS

The mRNA transcript levels of CDC2, CCNB1, CCNB2, CDC25A, CDC25B, CDC25C and WEE1 in the testes of 37 azoospermic patients were examined by quantitative real-time polymerase chain reaction. Significant decreases in CDC2, CCNB1, CCNB2, CDC25A, CDC25C and WEE1 mRNA transcript levels were detected in patients with spermatogenic failure. CDC2 mRNA transcript levels correlated significantly with those of CCNB1 and CCNB2 mRNA. Significantly higher CDC2, CCNB1, CCNB2, CDC25C and WEE1 mRNA transcript levels were detected in 18 patients with successful sperm retrieval than in 11 patients with failed sperm retrieval.

CONCLUSIONS

We suggest that the decreased mRNA transcripts of MPF and its regulators play important roles in human spermatogenesis.