Genetic causes of spermatogenic failure

SOX30 is required for male fertility in mice

Male infertility is a major and growing problem and, in most cases, the specific root cause is unknown. Here we show that the transcription factor SOX30 plays a critical role in mouse spermatogenesis. Sox30-null mice are healthy and females are fertile, but males are sterile. In the absence of Sox30 meiosis initiates normally in both sexes but, in males, germ cell development arrests during the post-meiotic round spermatid period. In the mutant testis, acrosome and axoneme development are aberrant, multinucleated germ cells (symplasts) form and round spermatids unable to process beyond step 3 of spermiogenesis. No elongated spermatids nor spermatozoa are produced. Thus, Sox30 represents a rare example of a gene for which loss of function results in a complete arrest of spermatogenesis at the onset of spermiogenesis. Our results suggest that SOX30 mutations may underlie some instances of unexplained non-obstructive azoospermia in humans.

High frequency of microdeletion in TTY2 gene family in peripheral blood leukocytes of non-obstructive azoospermia patients

About 10-15% of non-obstructive azoospermia (NOA) patients show AZFc microdeletion in their blood leukocytes. However, if AZF genes were involved in impaired spermatogenesis, a higher frequency of chromosomal microdeletions was expected. In this study the frequency of AZFc microdeletion was compared with TTY2 gene family, i.e., TTY2A2A and TTY2A12A in blood leukocytes of NOA patients and normal fertile control. In the present study 30 normal fertile individuals with mean age of 35.0 ± 6.0 and 30 NOA patients with mean age of 34.0 ± 7.0 were screened for microdeletion of TTY2L2A and TTY2L12A at Yq11 and Yp11 respectively and sequence-tagged site (STS) markers for AZFc gene using multiplex PCR technique. At the first step karyotyping was done for all subjects using standard G-banding technique to identify patients with normal karyotype as well as non-affected normal controls for molecular analysis. Results showed no AZFc microdeletion in normal and NAO patients whereas one TTY2L2A microdeletion in normal control (3.3%) and 4 in NOA (13.3%) was observed (p < 0.05). However our data indicated that 6 of 30 NOA patients (20%) showed TTY2L12A microdeletion whereas there was no observed microdeletion in normal control (p < 0.01). Results indicate that the studied genes might be involved in impaired spermatogenesis more effective than the routinely screened AZF genes in infertile men. Therefore, screening these genes along with AZF genes might be valuable for infertile patients. The reason why these genes are deleted from Y chromosome is not known but might be associated with genomic instability induced by environmental physico-chemical genotoxic agents.

Association of the common SNPs in RNF212, STAG3 and RFX2 gene with male infertility with azoospermia in Chinese population

OBJECTIVE

The aim of this study was to explore the association between the SNP rs4045481 in RNF212 gene, rs1050482 and rs11531577 in STAG3 gene as well as rs2288846 in RFX2 gene and male infertility with azoospermia in Chinese population.

STUDY DESIGN

Two hundreds and twenty infertile patients with azoospermia and 248 fertile men were recruited in the present study. The four SNPs investigated were genotyped using polymerase chain reaction and restriction fragment length polymorphism assay. The differences in allelic and genotypic frequencies between patients and controls were evaluated by chi-square test.

RESULTS

No significant differences in allele and genotype frequencies of SNP rs1050482 and rs11531577 in STAG3 gene as well as rs2288846 in RFX2 gene between patients with azoospermia and controls were observed. However, the frequencies of allele C(43.6% vs. 34.1%, P = 0.003, OR = 1.498, 95% CI 1.150-1.192) and genotype CC (24.6% vs. 12.0%, P = 0.001, OR = 2.346, 95% CI 1.448-3.858) were significantly higher in patients with azoospermia than those in controls at the rs4045481 locus in RNF212 gene.

CONCULUSION

The polymorphism of SNP rs4045481 in RNF212 gene might be associated with azoospermia and genotype CC of this SNP may be a risk factor of azoospermia.

Comprehensive functional enrichment analysis of male infertility

Spermatogenesis is a multifactorial process that forms differentiated sperm cells in a complex microenvironment. This process involves the genome, epigenome, transcriptome, and proteome to ensure the stability of the spermatogonia and supporting cells. The identification of signaling pathways linked to infertility has been hampered by the inherent complexity and multifactorial aspects of spermatogenesis. Systems biology is a promising approach to unveil underlying signaling pathways and genes and identify putative biomarkers. In this study, we analyzed thirteen microarray libraries of infertile humans and mice, and different classes of male infertility were compared using differentially expressed genes and functional enrichment analysis. We found regulatory processes, immune response, glutathione transferase and muscle tissue development to be among the most common biological processes in up-regulated genes, and genes involved in spermatogenesis were down-regulated in maturation arrest (MArrest) and oligospermia cases. We also observed the overexpression of genes involved in steroid metabolism in post-meiotic and meiotic arrest. Furthermore, we found that the infertile mouse model most similar to human MArrest was the Dazap1 mutant mouse. The results of this study could help elucidate features of infertility etiology and provide the basis for diagnostic markers.

Detection of candidate nectin gene mutations in infertile men with severe teratospermia

PURPOSE

Approximately 40% of infertile men have an abnormal semen analysis, resulting from either abnormalities of sperm production (defective spermatogenesis) or sperm shape (defective spermiogenesis). This latter process is dependent upon the function of Sertoli cells, which maintain specialized junctional complexes with germ cells. Nectins, members of the immunoglobulin superfamily, participate in formation of these dynamic complexes. Male mice in which the nectin-2 or nectin-3 gene is knocked out are sterile. Their spermatozoa exhibit severe teratospermia, altered motility, and an impaired ability to fertilize eggs. We asked whether mutations in the protein coding regions of the nectin-2 (aka PVRL2) and nectin-3 (aka PVRL3) genes could be detected in men from infertile couples whose semen analysis revealed unimpaired sperm production, judged by normal sperm concentration, but severe abnormalities in sperm shape.

METHODS

Ejaculates were snap frozen in liquid nitrogen and later submitted for Sanger analysis of these two genes, to detect mutations in their protein coding regions.

RESULTS

Eighty-nine of 455 ejaculates (19.5%) met the inclusion criteria for study. Two of the 56 samples that were successfully analyzed for nectin-2 (3.6%) and one of 73 (1.3%) analyzed for nectin-3 possessed possibly damaging mutations.

CONCLUSIONS

Despite the small-scale nature of the study, at least two low-frequency deleterious variants were identified. These results suggest the need for a larger-scale study of sequence variants in the nectins in severe teratospermia.

Recurrent deletions of the X chromosome linked CNV64, CNV67, and CNV69 shows geographic differences across China and no association with idiopathic infertility in men

A recent study found that three recurrent deletions of X chromosome linked copy number variations (CNVs), CNV64, CNV67 and CNV69 were associated with idiopathic male infertility in Spanish and Italian populations, especially CNV67 resembling the azoospermia factor deletions. That merits further investigations among different populations. This study was conducted to examine the prevalence of the three CNVs deletions and their associations with idiopathic male infertility in Chinese Han population. The present study included a large population of 1550 Chinese Han subjects recruited between 2014 and 2016. In total, 714 infertile participants were diagnosed as idiopathic infertility with different conditions (288 with non-obstructive azoospermia, 210 oligozoospermia and 216 asthenospermia) and 836 fertile participants (vasectomized men). The fertile participants were recruited from the representative areas: the north (Hebei and Shanxi), center (Hubei and Jiangsu), and south (Guangdong) of China. All patients were recruited from Hubei province. A multiplex PCR system was established to screen the deletion of the three CNVs, and deletion was confirmed by general PCR. Similar rates of these deletions were observed in infertile men and fertile participants (Hubei), and among the different conditions of infertility. Moreover, CNV64 and CNV67 map distribution geographically differed across China. The three CNVs in fertile groups of other regions were similar, except for Guangdong. No association between the three CNVs deletions and idiopathic male infertility was observed. CNV67 is rare in central China, albeit large sample size study for confirmation is warranted. It seems that the association between these CNVs deletions and idiopathic male infertility is ethnic dependent. There is still need to screen the CNVs deletions in other ethnicities. We suggested to consider the stratification patterns and geographic differences when prescribing CNVs deletions screening as a test in male infertility.

Unraveling transcriptome dynamics in human spermatogenesis

Spermatogenesis is a dynamic developmental process that includes stem cell proliferation and differentiation, meiotic cell divisions and extreme chromatin condensation. Although studied in mice, the molecular control of human spermatogenesis is largely unknown. Here, we developed a protocol that enables next-generation sequencing of RNA obtained from pools of 500 individually laser-capture microdissected cells of specific germ cell subtypes from fixed human testis samples. Transcriptomic analyses of these successive germ cell subtypes reveals dynamic transcription of over 4000 genes during human spermatogenesis. At the same time, many of the genes encoding for well-established meiotic and post-meiotic proteins are already present in the pre-meiotic phase. Furthermore, we found significant cell type-specific expression of post-transcriptional regulators, including expression of 110 RNA-binding proteins and 137 long non-coding RNAs, most of them previously not linked to spermatogenesis. Together, these data suggest that the transcriptome of precursor cells already contains the genes necessary for cellular differentiation and that timely translation controlled by post-transcriptional regulators is crucial for normal development. These established transcriptomes provide a reference catalog for further detailed studies on human spermatogenesis and spermatogenic failure.

Highlighted Article: Using laser capture microscopy, a comprehensive transcriptomic dataset of well-defined and distinct germ cell subtypes based on morphology and localization in the human testis is generated.

HIWI2 rs508485 Polymorphism Is Associated with Non-obstructive Azoospermia in Iranian Patients

BACKGROUND

The PIWI-interacting RNA (piRNA) pathway has an essential role in transposon silencing, meiosis progression, spermatogenesis, and germline maintenance. HIWI genes are critical for piRNA biogenesis and function. Therefore, polymorphisms in HIWI genes contribute to spermatogenesis defects and can be considered as risk factors for male infertility. The aim of the present study was to investigate the association between the HIWI2 gene rs508485 polymorphism and non-obstructive azoospermia.

METHODS

A total of 121 Iranian men with idiopathic azoospermia and 100 fertile controls were genotyped for HIWI2 rs508485 (T>C) polymorphism using Tetra-ARMS PCR. The presence of eight sequence-tagged site (STS) markers from the Y chromosome AZF region was also investigated by Multiplex PCR (M-PCR).

RESULTS

Thirteen (10.74%) patients showed Y chromosome microdeletions and therefore were excluded from the study. rs508485 in the 3'UTR of HIWI2 was associated with increased risk of azoospermia in our studied population with a P-value of 0.035 and odds ratio of 2.00 (CI 95%: 1.04-3.86).

CONCLUSIONS

We provide evidence for an association between genetic variation in the HIWI2 gene involved in the piRNA pathway and idiopathic non-obstructive azoospermia in Iranian patients. Therefore, piRNA pathway gene variants can be considered as risk factors for male infertility.

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.

Induced pluripotent stem cell generation from a man carrying a complex chromosomal rearrangement as a genetic model for infertility studies

Despite progress in human reproductive biology, the cause of male infertility often remains unknown, due to the lack of appropriate and convenient in vitro models of meiosis. Induced pluripotent stem cells (iPSCs) derived from the cells of infertile patients could provide a gold standard model for generating primordial germ cells and studying their development and the process of spermatogenesis. We report the characterization of a complex chromosomal rearrangement (CCR) in an azoospermic patient, and the successful generation of specific-iPSCs from PBMC-derived erythroblasts. The CCR was characterized by karyotype, fluorescence in situ hybridization and oligonucleotide-based array-comparative genomic hybridization. The CCR included five breakpoints and was caused by the inverted insertion of a chromosome 12 segment into the short arm of one chromosome 7 and a pericentric inversion of the structurally rearranged chromosome 12. Gene mapping of the breakpoints led to the identification of a candidate gene, SYCP3. Erythroblasts from the patient were reprogrammed with Sendai virus vectors to generate iPSCs. We assessed iPSC pluripotency by RT-PCR, immunofluorescence staining and teratoma induction. The generation of specific-iPSCs from patients with a CCR provides a valuable in vitro genetic model for studying the mechanisms by which chromosomal abnormalities alter meiosis and germ cell development.

Single gene defects leading to sperm quantitative anomalies

Azoospermia, defined by the absence of sperm in the ejaculate, is estimated to affect up to 1% of men in the general population. Assisted reproductive technologies have revolutionized the treatment of infertility, and some azoospermic men, those with a post-meiotic defect, can conceive following the use of viable spermatoza recovered from testicular or epididymal biopsies. Although male infertility is a multifactorial disease, it is believed that genetic factors are predominant in the etiology of azoospermia and severe oligozoospermia. Despite that assumption, substantiated by the high number of infertile knockout (KO) mice and the even higher number of genes expressed essentially in the testis, little is known about the pathophysiology of reduced sperm production, its primary causes or the genetic and epigenetic consequences for the gamete and the future conceptus. The identification of genetic abnormalities is therefore paramount to understand spermatogenesis, to adopt the best course of action for the patient and to provide adequate genetic counseling. We provide here a review of the recent literature on the genetics of azoospermia and oligozoospermia, focusing on defects directly altering sperm production. New sequencing technologies are contributing to the rapid evolution of the recent field of infertility genetics.

Systematic Analysis of Protein Interaction Network Associated with Azoospermia

Non-obstructive azoospermia is a severe infertility factor. Currently, the etiology of this condition remains elusive with several possible molecular pathway disruptions identified in the post-meiotic spermatozoa. In the presented study, in order to identify all possible candidate genes associated with azoospermia and to map their relationship, we present the first protein-protein interaction network related to azoospermia and analyze the complex effects of the related genes systematically. Using Online Mendelian Inheritance in Man, the Human Protein Reference Database and Cytoscape, we created a novel network consisting of 209 protein nodes and 737 interactions. Mathematical analysis identified three proteins, ar, dazap2, and esr1, as hub nodes and a bottleneck protein within the network. We also identified new candidate genes, CREBBP and BCAR1, which may play a role in azoospermia. The gene ontology analysis suggests a genetic link between azoospermia and liver disease. The KEGG analysis also showed 45 statistically important pathways with 31 proteins associated with colorectal, pancreatic, chronic myeloid leukemia and prostate cancer. Two new genes and associated diseases are promising for further experimental validation.

The control of male fertility by spermatid-specific factors: searching for contraceptive targets from spermatozoon's head to tail

Male infertility due to abnormal spermatozoa has been reported in both animals and humans, but its pathogenic causes, including genetic abnormalities, remain largely unknown. On the other hand, contraceptive options for men are limited, and a specific, reversible and safe method of male contraception has been a long-standing quest in medicine. Some progress has recently been made in exploring the effects of spermatid-specifical genetic factors in controlling male fertility. A comprehensive search of PubMed for articles and reviews published in English before July 2016 was carried out using the search terms 'spermiogenesis failure', 'globozoospermia', 'spermatid-specific', 'acrosome', 'infertile', 'manchette', 'sperm connecting piece', 'sperm annulus', 'sperm ADAMs', 'flagellar abnormalities', 'sperm motility loss', 'sperm ion exchanger' and 'contraceptive targets'. Importantly, we have opted to focus on articles regarding spermatid-specific factors. Genetic studies to define the structure and physiology of sperm have shown that spermatozoa appear to be one of the most promising contraceptive targets. Here we summarize how these spermatid-specific factors regulate spermiogenesis and categorize them according to their localization and function from spermatid head to tail (e.g., acrosome, manchette, head-tail conjunction, annulus, principal piece of tail). In addition, we emphatically introduce small-molecule contraceptives, such as BRDT and PPP3CC/PPP3R2, which are currently being developed to target spermatogenic-specific proteins. We suggest that blocking the differentiation of haploid germ cells, which rarely affects early spermatogenic cell types and the testicular microenvironment, is a better choice than spermatogenic-specific proteins. The studies described here provide valuable information regarding the genetic and molecular defects causing male mouse infertility to improve our understanding of the importance of spermatid-specific factors in controlling fertility. Although a male contraceptive 'pill' is still many years away, research into the production of new small-molecule contraceptives targeting spermatid-specific proteins is the right avenue.

Relationship between AZFc deletions and testicular histology in infertile South Chinese men with azoospermia and severe oligospermia

BACKGROUND

The AZFc deletion has been associated with wide range of phenotypes including complete absence of germ cells in the testes (SCOS), reduction in germ cells hypospermatogenesis, and maturation arrest. The main objective of this study was to evaluate the relationship between AZFc microdeletions and testicular histology in South Chinese men with azoospermia or severe oligospermia.

FINDINGS

338 men presenting with idiopathic non-obstructive azoospermia or severe oligospermia were evaluated between March 2012 and April 2015. Thirty-nine of the patients examined had an AZFc deletion (10.9 %). Testicular cytopathology was examined in 25 patients with an AZFc microdeletion and 14 with an AZFc deletion. There was no significant difference in the testicular histology of patients with partial or complete AZFc deletions (Mann-Whitney U = 152.500, p = 0.515). There was an association between testicular histology and gr/gr, b1/b3 or b2/b3 deletion (Fisher's exact test, p = 0.013).

CONCLUSIONS

Men with a gr/gr partial deletion were at higher risk of having hypospermatogenesis or maturation arrest. Men with a b1/b3 partial deletion were at higher risk of having maturation arrest. Men with a b2/b3 partial deletion were at higher risk of having maturation arrest or complete absence of germ cells in the testes.

Semen quality of young adult ICSI offspring: the first results

STUDY QUESTION

What is the semen quality of young adult men who were conceived 18-22 years ago by ICSI for male infertility?

SUMMARY ANSWER

In this cohort of 54 young adult ICSI men, median sperm concentration, total sperm count and total motile sperm count were significantly lower than in spontaneously conceived peers.

WHAT IS KNOWN ALREADY

The oldest ICSI offspring cohort worldwide has recently reached adulthood. Hence, their reproductive health can now be investigated. Since these children were conceived by ICSI because of severe male-factor infertility, there is reasonable concern that male offspring have inherited the deficient spermatogenesis from their fathers. Previously normal pubertal development and adequate Sertoli and Leydig cell function have been described in pubertal ICSI boys; however, no information on their sperm quality is currently available.

STUDY DESIGN, SIZE, DURATION

This study was conducted at UZ Brussel between March 2013 and April 2016 and is part of a large follow-up project focussing on reproductive and metabolic health of young adults, between 18 and 22 years and conceived after ICSI with ejaculated sperm. Results of both a physical examination and semen analysis were compared between young ICSI men being part of a longitudinally followed cohort and spontaneously conceived controls who were recruited cross-sectionally.

PARTICIPANTS/MATERIALS, SETTING, METHOD

Results of a single semen sample in 54 young adult ICSI men and 57 spontaneously conceived men are reported. All young adults were individually assessed, and the results of their physical examination were completed by questionnaires. Data were analysed by multiple linear and logistic regression, adjusted for covariates. In addition, semen parameters of the ICSI fathers dating back from their ICSI treatment application were analysed for correlations.

MAIN RESULTS AND THE ROLE OF CHANCE

Young ICSI adults had a lower median sperm concentration (17.7 million/ml), lower median total sperm count (31.9 million) and lower median total motile sperm count (12.7 million) in comparison to spontaneously conceived peers (37.0 million/ml; 86.8 million; 38.6 million, respectively). The median percentage progressive and total motility, median percentage normal morphology and median semen volume were not significantly different between these groups. After adjustment for confounders (age, BMI, genital malformations, time from ejaculation to analysis, abstinence period), the statistically significant differences between ICSI men and spontaneously conceived peers remained: an almost doubled sperm concentration in spontaneously conceived peers in comparison to ICSI men (ratio 1.9, 95% CI 1.1-3.2) and a two-fold lower total sperm count (ratio 2.3, 95% CI 1.3-4.1) and total motile count (ratio 2.1, 95% CI 1.2-3.6) in ICSI men compared to controls were found. Furthermore, compared to men born after spontaneous conception, ICSI men were nearly three times more likely to have sperm concentrations below the WHO reference value of 15 million/ml (adjusted odds ratio (AOR) 2.7; 95% CI 1.1-6.7) and four times more likely to have total sperm counts below 39 million (AOR 4.3; 95% CI 1.7-11.3). In this small group of 54 father-son pairs, a weak negative correlation between total sperm count in fathers and their sons was found.

LIMITATIONS, REASONS FOR CAUTION

The main limitation is the small study population. Also, the results of this study where ICSI was performed with ejaculated sperm and for male-factor infertility cannot be generalized to all ICSI offspring because the indications for ICSI have nowadays been extended and ICSI is also being performed with non-ejaculated sperm and reported differences may thus either decrease or increase.

WIDER IMPLICATIONS OF THE FINDINGS

These first results in a small group of ICSI men indicate a lower semen quantity and quality in young adults born after ICSI for male infertility in their fathers.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by Methusalem grants and by grants from Wetenschappelijk Fonds Willy Gepts, all issued by the Vrije Universiteit Brussel (VUB). All co-authors except M.B. and H.T. declared no conflict of interest. M.B. has received consultancy fees from MSD, Serono Symposia and Merck. The Universitair Ziekenhuis Brussel (UZ Brussel) and the Centre for Medical Genetics have received several educational grants from IBSA, Ferring, Organon, Shering-Plough and Merck for establishing the database for follow-up research and organizing the data collection. The institution of H.T. has received research grants from the Research Fund of Flanders (FWO), an unconditional grant from Ferring for research on testicular stem cells and research grants from Ferring, Merck, MSD, Roche, Besins, Goodlife and Cook for several research projects in female infertility. H.T. has received consultancy fees from Finox, Abbott and ObsEva for research projects in female infertility.

DNA methyltransferases exhibit dynamic expression during spermatogenesis

DNA methylation is one of the epigenetic marks and plays critically important functions during spermatogenesis in mammals. DNA methylation is catalysed by DNA methyltransferase (DNMT) enzymes, which are responsible for the addition of a methyl group to the fifth carbon atom of the cytosine residues within cytosine-phosphate-guanine (CpG) and non-CpG dinucleotide sites. Structurally and functionally five different DNMT enzymes have been identified in mammals, including DNMT1, DNMT2, DNMT3A, DNMT3B and DNMT3L. These enzymes mainly play roles in two DNA methylation processes: maintenance and de novo. While DNMT1 is primarily responsible for maintenance methylation via transferring methyl groups to the hemi-methylated DNA strands following DNA replication, both DNMT3A and DNMT3B are capable of methylating unmodified cytosine residues, known as de novo methylation. However, DNMT3L indirectly participates in de novo methylation, and DNMT2 carries out methylation of the cytosine 38 in the anticodon loop of aspartic acid transfer RNA. To date, many studies have been performed to determine spatial and temporal expression levels and functional features of the DNMT in the male germ cells. This review article comprehensively discusses dynamic expression of the DNMT during spermatogenesis and their relationship with male infertility development in the light of existing investigations.

The polymorphism G4C14-to-A4T14 in p73 gene may affect the susceptibility to male infertility with severe spermatogenesis impairment in Chinese population

OBJECTIVE

The aim of this study was to explore the association between the polymorphism G4C14-to-A4T14 in the p73 gene and male infertility with severe spermatogenesis impairment in Chinese population.

STUDY DESIGN

Three hundreds and one infertile patients with severe spermatogenesis impairment (including azoospermia and severe oligospermia) and 252 fertile men were recruited in this study. The polymorphism G4C14-to-A4T14 in the p73 gene was genotyped using polymerase chain reaction and restriction fragment length polymorphism assay. The differences in allelic and genotypic frequencies between patients and controls were evaluated by chi-square test.

RESULTS

The frequency of allele AT (28.9% vs. 22.4%, P=0.017, OR=1.41, 95% CI=1.07-1.85) in patients with severe spermatogenesis impairment was significantly higher than that in controls, whereas the genotype GC/GC was significantly decreased in patients compared with controls (48.5% vs. 59.1%, P=0.048, OR=0.65, 95% CI=0.46-0.91).

CONCULUSION

The findings of this study suggested that the polymorphism G4C14-to-A4T14 in p73 gene might be associated with severe spermatogenesis impairment and could affect the susceptibility to male infertility with severe spermatogenesis impairment in Chinese population.

Transcriptome research on spermatogenic molecular drive in mammals

It is known that spermatogenic disorders are associated with genetic deficiency, although the primary mechanism is still unclear. It is difficult to demonstrate the molecular events occurring in testis, which contains germ cells at different developmental stages. However, transcriptomic methods can help us reveal the molecular drive of male gamete generation. Many transcriptomic studies have been performed on rodents by utilizing the timing of the first wave of spermatogenesis, which is not a suitable strategy for research in fertile men. With the development of separation methods for male germ cells, transcriptome research on the molecular drive of spermatogenesis in fertile men has seen great progress, and the results could be ultimately applied to improve the diagnosis and treatment for male infertility.

Prevalence of chromosomal abnormalities and Y chromosome microdeletion among men with severe semen abnormalities and its correlation with successful sperm retrieval

AIM

To estimate the prevalence of chromosomal abnormalities and Y chromosome microdeletion among men with azoospermia and severe oligozoospermia and its correlation with successful surgical sperm retrieval.

SETTING AND DESIGN

A prospective study in a tertiary level infertility unit.

MATERIALS AND METHODS

In a prospective observation study, men with azoospermia and severe oligozoospermia (concentration <5 million/ml) attending the infertility center underwent genetic screening. Peripheral blood karyotype was done by Giemsa banding. Y chromosome microdeletion study was performed by a multiplex polymerase chain reaction.

RESULTS

The study group consisted of 220 men, 133 of whom had azoospermia and 87 had severe oligozoospermia. Overall, 21/220 (9.5%) men had chromosomal abnormalities and 13/220 (5.9%) men had Y chromosome microdeletions. Chromosomal abnormalities were seen in 14.3% (19/133) of azoospermic men and Y chromosome microdeletions in 8.3% (11/133). Of the 87 men with severe oligozoospermia, chromosomal abnormalities and Y chromosome microdeletions were each seen in 2.3% (2/87). Testicular sperm aspiration was done in 13 men and was successful in only one, who had a deletion of azoospermia factor c.

CONCLUSIONS

Our study found a fairly high prevalence of genetic abnormality in men with severe semen abnormalities and a correlation of genetic abnormalities with surgical sperm retrieval outcomes. These findings support the need for genetic screening of these men prior to embarking on surgical sperm retrieval and assisted reproductive technology intracytoplasmic sperm injection.

Recurrent Microdeletions at Xq27.3-Xq28 and Male Infertility: A Study in the Czech Population

Background

Genetic causes of male infertility are hypothesized to involve multiple types of mutations, from single gene defects to complex chromosome rearrangements. Recently, several recurrent X-chromosome microdeletions (located in subtelomeric region of the long arm) were reported to be associated with male infertility in Spanish and Italian males. The aim of our study was to test their prevalence and infertility association in population of men from the Czech Republic.

Methods

107 males with pathological sperm evaluation resulting in nonobstructive infertility were compared to 131 males with normal fecundity. X-chromosome microdeletions were assessed by +/- PCR with three primer pairs for each region Xcnv64 (Xq27.3), Xcnv67 (Xq28) and Xcnv69 (Xq28). The latter microdeletion was further characterized by amplification across the deleted region, dividing the deletion into three types; A, B and C.

Results

We detected presence of isolated Xcnv64 deletion in 3 patients and 14 controls, and Xcnv69 in 3 patients and 6 controls (1 and 1 patient vs.4 and 1 control for types A and B respectively). There was one control with combined Xcnv64 and Xcnv69 type B deletions, and one patient with combination of Xcnv64 and Xcnv69 type C deletions. The frequency of the deletions was thus not higher in patient compared to control group, Xcnv64 was marginally associated with controls (adjusted Fisher´s exact test P = 0.043), Xcnv69 was not associated (P = 0.452). We excluded presence of more extensive rearrangements in two subjects with combined Xcnv64 and Xcnv69 deletions. There was no Xcnv67 deletion in our cohort.

Conclusion

In conclusion, the two previously reported X-linked microdeletions (Xcnv64 and Xcnv69) do not seem to confer a significant risk to impaired spermatogenesis in the Czech population. The potential clinical role of the previously reported patient-specific Xcnv67 remains to be determined in a larger study population.

Outcomes of intracytoplasmic sperm injection in oligozoospermic men with Y chromosome AZFb or AZFc microdeletions

We investigated whether the presence of Y chromosome azoospermia factor (AZF) microdeletions impacts upon the outcomes of intracytoplasmic sperm injection (ICSI) using fresh ejaculated spermatozoa. Sixteen oligozoospermia patients with Y chromosome AZFb or AZFc microdeletions and undergoing ICSI cycles between March 2013 and November 2014 were studied. Twenty-six infertile men with normal Y chromosomes and also undergoing IVF/ICSI in the same time period were used as controls. A retrospective case-control study approach was used. Among the 16 cases, 12 (75%, 12/16) had deletions of AZFc markers (sY152, sY254 and sY255), one (6.25%, 1/16) had a deletion of sY152, and two (12.5%, 2/16) had deletions of sY152, sY254, sY255 and sY157. AZFb microdeletions were found in one patient (6.25%, 1/16). There were no significant differences between groups for cleaved embryo rate, high-grade embryo rate, blastocyst formation rate, embryo implantation rate, clinical pregnancy rate and delivery rate. The clinical outcomes of ICSI for oligozoospermic patients with Y chromosome AZF microdeletion are comparable to those of infertile patients with normal Y chromosomes. Our findings indicate that ICSI should be offered to patients with an AZFc deletion and that oligozoospermia patients with AZFb microdeletions are likely to father children.

Association of a TDRD1 variant with spermatogenic failure susceptibility in the Han Chinese

PURPOSE

Piwi-interacting RNAs (piRNAs) are a broad group of noncoding small RNAs that have important biological functions in germline cells and can maintain genome integrity via silencing of retrotransposons. In this study, we aimed to explore the associations between genetic variants of important genes involved in piRNA biogenesis and male infertility with spermatogenic impairment.

METHODS

To this end, five single-nucleotide polymorphisms (SNPs) in the ASZ1, PIWIL1, TDRD1, and TDRD9 genes were genotyped by TaqMan allelic discrimination assays in 342 cases of nonobstructive azoospermia (NOA) and 493 controls.

RESULTS

The SNP rs77559927 in TDRD1 was associated with a reduced risk of spermatogenic impairment. The genotypes TC and TC + CC showed odds ratios and 95 % confidence intervals of 0.73 (0.55-0.98, P = 0.034) and 0.73 (0.56-0.97, P = 0.030), respectively, in patients with NOA compared with those in the controls.

CONCLUSION

Thus, our results provided the first epidemiological evidence supporting the involvement of TDRD1 genetic polymorphisms in piRNA processing genes in determining the risk of spermatogenic impairment in a Han Chinese population.

Knockout of BRD7 results in impaired spermatogenesis and male infertility

BRD7 was originally identified as a novel bromodomain gene and a potential transcriptional factor. BRD7 was found to be extensively expressed in multiple mouse tissues but was highly expressed in the testis. Furthermore, BRD7 was located in germ cells during multiple stages of spermatogenesis, ranging from the pachytene to the round spermatid stage. Homozygous knockout of BRD7 (BRD7^−/−) resulted in complete male infertility and spermatogenesis defects, including deformed acrosomal formation, degenerative elongating spermatids and irregular head morphology in postmeiotic germ cells in the seminiferous epithelium, which led to the complete arrest of spermatogenesis at step 13. Moreover, a high ratio of apoptosis was determined by TUNEL analysis, which was supported by high levels of the apoptosis markers annexin V and p53 in knockout testes. Increased expression of the DNA damage maker λH2AX was also found in BRD7^−/− mice, whereas DNA damage repair genes were down−regulated. Furthermore, no or lower expression of BRD7 was detected in the testes of azoospermia patients exhibiting spermatogenesis arrest than that in control group. These data demonstrate that BRD7 is involved in male infertility and spermatogenesis in mice, and BRD7 defect might be associated with the occurrence and development of human azoospermia.

Dynamics of the Transcriptome during Human Spermatogenesis: Predicting the Potential Key Genes Regulating Male Gametes Generation

Many infertile men are the victims of spermatogenesis disorder. However, conventional clinical test could not provide efficient information on the causes of spermatogenesis disorder and guide the doctor how to treat it. More effective diagnosis and treating methods could be developed if the key genes that regulate spermatogenesis were determined. Many works have been done on animal models, while there are few works on human beings due to the limited sample resources. In current work, testis tissues were obtained from 27 patients with obstructive azoospermia via surgery. The combination of Fluorescence Activated Cell Sorting and Magnetic Activated Cell Sorting was chosen as the efficient method to sort typical germ cells during spermatogenesis. RNA Sequencing was carried out to screen the change of transcriptomic profile of the germ cells during spermatogenesis. Differential expressed genes were clustered according to their expression patterns. Gene Ontology annotation, pathway analysis, and Gene Set Enrichment Analysis were carried out on genes with specific expression patterns and the potential key genes such as HOXs, JUN, SP1, and TCF3 which were involved in the regulation of spermatogenesis, with the potential value serve as molecular tools for clinical purpose, were predicted.

Deletion of GOLGA2P3Y but not GOLGA2P2Y is a risk factor for oligozoospermia

The AZFc locus on the human Y chromosome harbours several multicopy genes, some of which are required for spermatogenesis. It is believed that deletion of one or more copies of these genes is a cause of infertility in some men. GOLGA2LY is one of the genes in the AZFc locus and it exists in two copies, GOLGA2P2Y and GOLGA2P3Y. The involvement of GOLGA2LY gene copy deletions in male infertility, however, is unknown. This study aimed to investigate the association of deletions of GOLGA2P2Y and GOLGA2P3Y gene copies with male infertility and with sperm concentration and motility. The frequency of GOLGA2P3Y deletion was significantly higher in oligozoospermic men compared with normozoospermic men (7.7% versus 1.2%; P = 0.0001), whereas the frequency of GOLGA2P2Y deletion was comparable between oligozoospermic and normozoospermic men (10.3% versus 11.3%). The deletion of GOLGA2P3Y but not GOLGA2P2Y was significantly higher (P = 0.03) in men with gr/gr rearrangements, indicating that GOLGA2P3Y deletions increase the susceptibility of men with gr/gr rearrangements to oligozoospermia. Furthermore, men with GOLGA2P3Y deletion had reduced sperm concentration and motility compared with men without deletion or with deletion of GOLGA2P2Y. These findings indicate GOLGA2P3Y gene copy may be candidate AZFc gene for male infertility.

Prevalence of Y Chromosome Microdeletions in Idiopathic Azoospermia Cases in Central Indian Men

BACKGROUND

Genetic factor is important determinant of human male fertility, it is involved in 10-15% infertile males. Chromosome abnormalities and Y chromosome microdeletions are the main genetic causative factors for infertility. The frequency of male infertility & microdeletions in Y chromosome are also related to ethnic, geographical variations. In this study, we evaluated the prevalence of chromosomal abnormalities and microdeletions of Y chromosome in infertile azoospermia cases in central India to assess the geographical or population based variations.

MATERIALS AND METHODS

We have studied 160 non-obstructive azoospermia cases to find out frequency of chromosomal abnormalities and Y chromosome microdeletions of AZF locus. G-banding method was used for exclusion of chromosomal abnormalities. One hundred and forty eight azoospermic infertile men were screened using 12 sequence-tagged-sites (STS) primers of AZFa, AZFb, AZFc region and SRY gene (Yp) region by polymerase chain reactions.

RESULTS

Out of 160 azoospermic infertile males, 12 (7.5%) confirmed chromosomal abnormalities and Klinefelter's syndrome was predominantly cause of azoospermia. Of the 148 infertile males, 19 (12.8%) were shown microdeletions in different AZF regions. Deletions in AZFa region were 2.02% and 3.37% was in AZFb whereas high frequencies of deletions (6.08%) in AZFc were recorded in azoospermic males. In two azoospermic males were shown microdeletions in AZFb+c loci.

CONCLUSION

The prevalence of Y chromosome microdeletions in azoospermic men was 12.8% in this geographical region. Klinefelter's syndrome is important cause in male infertility. So, the screening of Y microdeletions is essential.

Blood-testis barrier and spermatogenesis: lessons from genetically-modified mice

The blood-testis barrier (BTB) is found between adjacent Sertoli cells in the testis where it creates a unique microenvironment for the development and maturation of meiotic and postmeiotic germ cells in seminiferous tubes. It is a compound proteinous structure, composed of several types of cell junctions including tight junctions (TJs), adhesion junctions and gap junctions (GJs). Some of the junctional proteins function as structural proteins of BTB and some have regulatory roles. The deletion or functional silencing of genes encoding these proteins may disrupt the BTB, which may cause immunological or other damages to meiotic and postmeiotic cells and ultimately lead to spermatogenic arrest and infertility. In this review, we will summarize the findings on the BTB structure and function from genetically-modified mouse models and discuss the future perspectives.

The sperm quality and clinical outcomes were not affected by sY152 deletion in Y chromosome for oligozoospermia or azoospermia men after ICSI treatment

Azoospermia factor (AZF) microdeletion plays a key role in the genetic etiology of male infertility. The relationship between sY152 deletion in the AZFc region and clinical outcomes is still unclear. This study was to determine the effects of sY152 deletion on the sperm parameters and clinical outcomes of non-obstructive azoospermia or oligozoospermia men after intracytoplasmic sperm injection (ICSI) treatment. A total of 61 infertile men with AZFc microdeletion of the Y chromosome from January 2008 to December 2012 were recruited in the present study. They were divided into two groups, the sY152 group (n=12) and the AZFc group (n=49), based upon whether they have deleted single sY152 marker or all AZFc markers. Fifty azoospermia or oligozoospermia patients without Y chromosome microdeletion were included as the control group. The sperm quality and clinical data were compared among the three groups. Retrospective cohort-control study was performed. The sperm concentration and motility in sY152 group were better than AZFc group (P<0.05), and were comparable to the control group (P>0.05); the morphology, seminal zinc, seminal fructose and seminal carnitine were similar among the three groups (P>0.05). Patients in both sY152 and AZFc groups had lower fertilization rates (68.40% and 70.63%, respectively) than those in the control group (74.91%), and the differences were statistically significant (P<0.05). No significant differences were found in terms of MII oocyte, high-grade embryo rate, 2PN zygote, number of available embryos and transferred embryos, clinical pregnancy rate, implantation rate, miscarriage rate, multiple pregnancy rate, delivery rate, preterm rate and the male/female ratio among the three groups (P>0.05). Single sY152 deletion might cause a lower fertilization rate, but no adverse effects on sperm quality and clinical outcomes were found. Our study may provide more information for consultation in these patients.

Susceptibility of gr/gr rearrangements to azoospermia or oligozoospermia is dependent on DAZ and CDY1 gene copy deletions

PURPOSE

The purpose of this study was to determine the association of AZFc subdeletions (gr/gr, b1/b3 and b2/b3) and deletion of DAZ and CDY1 gene copies with male infertility

METHODS

Three hundred twelve controls, 172 azoospermic and 343 oligozoospermic subjects were subjected to AZFc subdeletion typing by STS PCR. Deletion of DAZ and CDY1 gene copies was done using sequence family variant analysis. Sperm concentration and motility were compared between men with and without AZFc subdeletions. Effect of the AZFc subdeletions on ICSI outcome was evaluated.

RESULTS

Amongst the three AZFc subdeletions, the frequency of gr/gr was higher in oligozoospermic (10.5 %) and azoospermic (11.6 %) men as compared to controls (5.1 %). In men with AZFc subdeltions, loss of two DAZ and one CDY1 gene copy made them highly susceptible to azoospermia and severe oligozoospermia with OR of 29.7 and 26, respectively. These subdeletions had no effect on ICSI outcome, albeit there were an increased number of poor quality embryos in AZFc subdeleted group.

CONCLUSION

AZFc subdeletions are a major risk factor for male infertility in the Indian population. In the subjects with AZFc subdeletions, the deletion of DAZ and CDY1 gene copies increases its susceptibility to azoospermia or severe oligozoospermia. Since these deletions can be vertically transmitted to the future male offspring by ICSI, it will be essential to counsel the couples for the transmission of the genetic defect in the male offspring born after assisted reproduction and the risk of perpetuating infertility in future generation.

The genetic variation in monocarboxylic acid transporter 2 (MCT2) has functional and clinical relevance with male infertility

Monocarboxylic acid transporter 2 (MCT2) transports pyruvate and lactate outside and inside of sperms, mainly as energy sources and plays roles in the regulation of spermatogenesis. We investigated the association among genetic variations in the MCT2 gene, male infertility and MCT2 expression levels in sperm. The functional and genetic significance of the intron 2 (+28201A > G, rs10506398) and 3’ untranslated region (UTR) single nucleotide polymorphism (SNP) (+2626G > A, rs10506399) of MCT2 variants were investigated. Two MCT2 polymorphisms were associated with male infertility (n = 471, P < 0.05). In particular, the MCT2-3’ UTR SNP (+2626 G > A) had a strong association with the oligoasthenoteratozoospermia (OAT) group. The +2626GG type had an almost 2.4-fold higher sperm count than that of the +2626AA type (+2626GG; 66 × 10⁶vs +2626AA; 27 × 10⁶, P < 0.0001). The MCT2-3’ UTR SNP may be important for expression, as it is located at the MCT2 3’ UTR. The average MCT2 protein amount in sperm of the +2626GG type was about two times higher than that of the +2626AA type. The results suggest that genetic variation in MCT2 has functional and clinical relevance with male infertility.

A Cascade of epistatic interactions regulating teratozoospermia in mice

Infertility in humans and subfertility in domestic animals are two major reproductive problems. Among human couples, ~15% are diagnosed as infertile, and males are considered responsible in about 50% of the cases. To examine male fertility, various sperm tests including analyses of sperm morphology, sperm count and sperm mobility are usually performed. Teratozoospermia, a condition characterized by the presence of morphologically abnormal sperm, is considered as a symptom of infertility. B10.MOL-TEN1 (TEN1) mice (Mus musculus) show inherited teratozoospermia at high frequencies (~50%). In this study, the polygenic control of teratozoospermia in the TEN1 strain was analysed. A quantitative trait loci analysis indicated three statistically significant loci, Sperm-head morphology 3 (Shm3; logarithm of the odds (LOD) score, 29.25), Shm4 (LOD score, 6.80), and Shm5 (LOD score, 3.58). These three QTL peaks were mapped to 24.3 centimorgans (cM) on chromosome 1, 32.0 cM on chromosome X, and 63.8 cM on chromosome 6, respectively. Another locus that is yet to be determined was also predicted. Shm3 was found to be the major locus responsible for teratozoospermia, and a sequential cascade of interactions of the other three loci was apparent. These results are expected to help understand the mechanisms underlying reproductive problems in humans or domestic animals.

Polygenic expression of teratozoospermia and normal fertility in B10.MOL-TEN1 mouse strain

Subfertility and infertility are two major reproductive health problems in human and domestic animals. The contribution of the genotype to these conditions is poorly understood. To examine the genetic basis of male subfertility, we analyzed its relationship to sperm morphology in B10.MOL-TEN1 mice, which shows high-frequencies (about 50%) of morphologically abnormal sperm. Drastic histological changes were also found in the testis of the B10.MOL-TEN1. Segregation analysis showed that the abnormal sperm phenotype in B10.MOL-TEN1 was inherited and was predictably controlled by at least three loci. We also found that male fertility of this strain was normal. These findings indicate a complicated relationship between sperm morphology and male subfertility.

A mutation study of sperm head shape and motility in the mouse: lessons for the clinic

Mouse mutants that show effects on sperm head shape, the sperm tail (flagellum), and motility were analysed in a systematic way. This was achieved by grouping mutations in the following classes: manchette, acrosome, Sertoli cell contact, chromatin remodelling, and mutations involved in complex regulations such as protein (de)phosphorylation and RNA stability, and flagellum/motility mutations. For all mutant phenotypes, flagellum function (motility) was affected. Head shape, including the nucleus, was also affected in spermatozoa of most mouse models, though with considerable variation. For the mutants that were categorized in the flagellum/motility group, generally normal head shapes were found, even when the flagellum did not develop or only poorly so. Most mutants are sterile, an occasional one semi-sterile. For completeness, the influence of the sex chromosomes on sperm phenotype is included. Functionally, the genes involved can be categorized as regulators of spermiogenesis. When extrapolating these data to human sperm samples, in vivo selection for motility would be the tool for weeding out the products of suboptimal spermiogenesis and epididymal sperm maturation. The striking dependency of motility on proper sperm head development is not easy to understand, but likely is of evolutionary benefit. Also, sperm competition after mating can never act against the long-term multi-generation interest of genetic integrity. Hence, it is plausible to suggest that short-term haplophase fitness i.e., motility, is developmentally integrated with proper nucleus maturation, including genetic integrity to protect multi-generation fitness. We hypothesize that, when the prime defect is in flagellum formation, apparently a feedback loop was not necessary as head morphogenesis in these mutants is mostly normal. Extrapolating to human-assisted reproductive techniques practice, this analysis would supply the arguments for the development of tools to select for motility as a continuous (non-discrete) parameter.

New insights into the genetic basis of infertility

Infertility is a disease of the reproductive system characterized by inability to achieve pregnancy after 12 or more months of regular unprotected sexual intercourse. A variety of factors, including ovulation defects, spermatogenic failure, parental age, obesity, and infections have been linked with infertility, in addition to specific karyotypes and genotypes. The study of genes associated with infertility in rodent models has expanded the field of translational genetics in identifying the underlying cause of human infertility problems. Many intriguing aspects of the molecular basis of infertility in humans remain poorly understood; however, application of genetic knowledge in this field looks promising. The growing literature on the genetics of human infertility disorders deserves attention and a critical concise summary is required. This paper provides information obtained from a systematic analysis of the literature related to current research into the genetics of infertility affecting both sexes.

Decrease in fertilization and cleavage rates, but not in clinical outcomes for infertile men with AZF microdeletion of the Y chromosome

This study aimed to explore whether the presence of a Y chromosome azoospermia factor (AZF) microdeletion confers any adverse effect on embryonic development and clinical outcomes after intracytoplasmic sperm injection (ICSI) treatment. Fifty-seven patients with AZF microdeletion were included in the present study and 114 oligozoospermia and azoospermia patients without AZF microdeletion were recruited as controls. Both AZF and control groups were further divided into subgroups based upon the methods of semen collection: the AZF-testicular sperm extraction subgroup (AZF-TESE, n = 14), the AZF-ejaculation subgroup (AZF-EJA, n = 43), the control-TESE subgroup (n = 28) and the control-EJA subgroup (n = 86). Clinical data were analyzed in the two groups and four subgroups respectively. A retrospective case-control study was performed. A significantly lower fertilization rate (69.27 versus 75.70%, P = 0.000) and cleavage rate (89.55 versus 94.39%, P = 0.000) was found in AZF group compared with the control group. Furthermore, in AZF-TESE subgroup, the fertilization rate (67.54 versus 74.25%, P = 0.037) and cleavage rate (88.96 versus 94.79%, P = 0.022) were significantly lower than in the control-TESE subgroup; similarly, the fertilization rate (69.85 versus 75.85%, P = 0.004) and cleavage rate (89.36 versus 94.26%, P = 0.002) in AZF-EJA subgroup were significantly lower than in the control-EJA subgroup; however, the fertilization rate and cleavage rate in AZF-TESE (control-TESE) subgroup was similar to that in the AZF-EJA (control-EJA) subgroup. The other clinical outcomes were comparable between four subgroups (P > 0.05). Therefore, sperm from patients with AZF microdeletion, obtained either by ejaculation or TESE, may have lower fertilization and cleavage rates, but seem to have comparable clinical outcomes to those from patients without AZF microdeletion.

Association of common SNP rs1136410 in PARP1 gene with the susceptibility to male infertility with oligospermia

PURPOSE

This study aims to explore possible associations between polymorphisms of common SNP rs1136410 and rS1805405 in PARP1 gene and male infertility with spermatogenesis impairment.

METHODS

The polymorphic distributions of SNP rs1136410 and rS1805405 were investigated by polymerase chain reaction and restriction fragment length polymorphism analysis in a Chinese cohort including 371 infertile patients with idiopathic azoospermia or oligospermia and 231 controls.

RESULTS

Significant differences in the frequencies of allele and genotype of SNP rs1136410 were observed between patients with oligospermia and controls. The allele C (46.3 % vs. 36.4 %, P = 0.003) and genotype CC (22.6 % vs. 13.4 %, P = 0.014) significantly increased, whereas genotype TT (30 % vs. 40.7 %, P = 0.021) significantly decreased in patients with oligospermia compared with controls at this SNP locus.

CONCLUSIONS

These results indicated that genotype CC of SNP rs1136410 may increase the risk of oligosoermia and genotype TT of rs1136410 may have some protective effect from oligospermia, suggesting that the polymorphism of SNP rs1136410 in PARP1 gene may modify the susceptibility to male infertility with oligospermia.

High frequency of TTTY2-like gene-related deletions in patients with idiopathic oligozoospermia and azoospermia

Genes located on Y chromosome and expressed in testis are likely to be involved in spermatogenesis. TTTY2 is a Y-linked multicopy gene family of unknown function that includes TTTY2L2A and TTTY2L12A at Yq11 and Yp11 loci respectively. Using PCR amplification, we screened for TTTY2L2A- and TTTY2L12A-associated deletions, in 94 Greek men with fertility problems. Patients were divided into three groups as following: group A (n = 28) included men with idiopathic moderate oligozoospermia, group B (n = 34) with idiopathic severe oligozoospermia and azoospermia, and group C (n = 32) with oligo- and azoospermia of various known etiologies. No deletions were detected in group C patients and 50 fertile controls. However, two patients from group A had deletions in TTTY2L2A (7.1%) and six in TTTY2L12A (21.4%), whereas from group B, four patients had deletions in TTTY2L2A (11.8%) and 10 in TTTY2L12A (29.4%). In addition, five patients from both groups A and B (8%) appeared to have deletions in both studied TTTY2 genes, although these are located very far apart. These results indicate that the TTTY2 gene family may play a significant role in spermatogenesis and suggest a possible mechanism of nonhomologous recombinational events that may cause genomic instability and ultimately lead to male infertility.

Lack of association of KATNAL1 gene sequence variants and azoospermia in humans

PURPOSE

A recent experiment indicated that a loss of function mutation in the murine Katnal1 gene resulted in male factor infertility due to premature exfoliation of spermatids. This study investigated the relevance of this gene to infertility in humans.

METHODS

Multiple methods of genetic analysis were employed to investigate whether mutations in human KATNAL1 have a causative role in male infertility. This was a genetic association study, which included DNA samples from 105 men with non-obstructive azoospermia (NOA) and 242 anonymous sperm donor controls. 28 commercially available TaqMan SNP assays were used to haplotype samples from both groups and genetically tag regions of interest across the entire gene. AmpliSeq primers were then designed for identified regions so that targeted next-generation sequencing (NGS) could be used to identify causative variants.

RESULTS

Four SNPs in the 3'UTR demonstrated a putative association with NOA. The AmpliSeq primers designed for the 3'UTR provided 83 % coverage of the 7,202 basepairs within the regions of interest. Variant sites were analyzed against genetic models to identify sequence polymorphisms which associated with NOA. No variants met standard criteria for significance when tested between the groups.

CONCLUSIONS

This study suggests a lack of association of KATNAL1 gene sequence variants and azoospermia in humans.

Genetic causes of male infertility

Male infertility, affecting around half of the couples with a problem to get pregnant, is a very heterogeneous condition. Part of patients are having a defect in spermatogenesis of which the underlying causes (including genetic ones) remain largely unknown. The only genetic tests routinely used in the diagnosis of male infertility are the analyses for the presence of Yq microdeletions and/or chromosomal abnormalities. Various other single gene or polygenic defects have been proposed to be involved in male fertility. Yet, their causative effect often remains to be proven. The recent evolution in the development of whole genome-based techniques may help in clarifying the role of genes and other genetic factors involved in spermatogenesis and spermatogenesis defects.

Mutational screening of the NR5A1 in azoospermia

Nuclear receptor subfamily 5 group A member 1 (NR5A1) encodes a nuclear receptor that regulates transcription of multiple genes involved in adrenal and gonadal development, steroidogenesis and the reproductive axis. Human mutations in NR5A1were initially found in two 46, XY female patients suffering from severe gonadal dysgenesis and primary adrenal failure. However, more recent case reports have suggested that heterozygous mutations in NR5A1 may also contribute to the male infertility aetiology. We have analysed the coding sequence of NR5A1 in a cohort of 90 well-characterised idiopathic Iranian azoospermic infertile men versus 112 fertile men. Heterozygous NR5A1 mutations were found in 2 of 90 (2.2%) of cases. These two patients harboured missense mutations within the hinge region (p.P97T) and ligand-binding domain (p.E237K) of the NR5A1 protein. In silico analysis of the mutations showed that founded mutations could be detrimental. In conclusion, findings of the current and previous studies suggest that mutations in the NR5A1 gene are not common in azoospermia, and male infertility and inclusion of NR5A1 mutation screening in the diagnostic workup of male infertility may seem unnecessary.

Clinical genetic testing for male factor infertility: current applications and future directions

Spermatogenesis involves the aggregated action of up to 2300 genes, any of which, could, potentially, provide targets for diagnostic tests of male factor infertility. Contrary to the previously proposed common variant hypothesis for common diseases such as male infertility, genome-wide association studies and targeted gene sequencing in cohorts of infertile men have identified only a few gene polymorphisms that are associated with male infertility. Unfortunately, the search for genetic variants associated with male infertility is further hampered by the lack of viable animal models of human spermatogenesis, difficulty in robustly phenotyping infertile men and the complexity of pedigree studies in male factor infertility. In this review, we describe basic genetic principles involved in understanding the genetic basis of male infertility and examine the utility and proper clinical use of the proven genetic assays of male factor infertility, specifically Y chromosome microdeletions, chromosomal translocations, karyotype, cystic fibrosis transmembrane conductance regulator mutation analysis and sperm genetic tests. Unfortunately, these tests are only able to diagnose the cause of about 20% of male factor infertility. The remainder of the review will be devoted to examining novel tests and diagnostic tools that have the potential to explain the other 80% of male factor infertility that is currently classified as idiopathic. Those tests include epigenetic analysis of the spermatozoa and the evaluation of rare genetic variants and copy number variations in patients. Success in advancing to the implementation of such areas is not only dependent on technological advances in the laboratory, but also improved phenotyping in the clinic.