An association study of four candidate loci for human male fertility traits with male infertility

Intergenerational trends in reproduction: Infertility and pregnancy loss

This review article summarises the evidence for intergenerational trends observed to date within infertility and pregnancy loss. There appears to be evidence of intergenerational trends between mothers and daughters for the age at menopause, endometriosis, polycystic ovarian syndrome (PCOS), male factor infertility and miscarriage. At present, there is no evidence for a predisposition to stillbirth between mothers and daughters. One study found an association with familial predisposition for ectopic pregnancy. Very few studies have considered the potential for paternal transmission of risk of infertility or pregnancy loss. The majority of studies to date have significant limitations because of their observational design, risk of recall bias and risk of confounding. Therefore, high-quality well-designed research, with multi-centre collaboration and utilisation of registry-based data sources and individual patient data, is needed to understand whether infertility and pregnancy loss may have heritable factors. Epidemiological findings need to be followed up and investigated with translational research to determine the possible causalities as well as any implications for clinical practice.

Genome-Wide Association Screening Determines Peripheral Players in Male Fertility Maintenance

Deciphering the functional relationships of genes resulting from genome-wide screens for polymorphisms that are associated with phenotypic variations can be challenging. However, given the common association with certain phenotypes, a functional link should exist. We have tested this prediction in newly sequenced exomes of altogether 100 men representing different states of fertility. Fertile subjects presented with normal semen parameters and had naturally fathered offspring. In contrast, infertile probands were involuntarily childless and had reduced sperm quantity and quality. Genome-wide association study (GWAS) linked twelve non-synonymous single-nucleotide polymorphisms (SNPs) to fertility variation between both cohorts. The SNPs localized to nine genes for which previous evidence is in line with a role in male fertility maintenance: ANAPC1, CES1, FAM131C, HLA-DRB1, KMT2C, NOMO1, SAA1, SRGAP2, and SUSD2. Most of the SNPs residing in these genes imply amino acid exchanges that should only moderately affect protein functionality. In addition, proteins encoded by genes from present GWAS occupied peripheral positions in a protein-protein interaction network, the backbone of which consisted of genes listed in the Online Mendelian Inheritance in Man (OMIM) database for their implication in male infertility. Suggestive of an indirect impact on male fertility, the genes focused were indeed linked to each other, albeit mediated by other interactants. Thus, the chances of identifying a central player in male infertility by GWAS could be limited in general. Furthermore, the SNPs determined and the genes containing these might prove to have potential as biomarkers in the diagnosis of male fertility.

NBMA Promotes Spermatogenesis by Mediating Oct4 Pathway

Non-obstructive azoospermia is one of the most common causes of male infertility, but there is still no specific treatment drug. Given that the Oct4 (Octamer-binding transcription factor 4) has an important regulatory effect on spermatogenesis, activating it can effectively promote spermatogenesis, so it is of great value to develop Oct4-targeted drug design and elucidating its mechanism of action. Here, we screened out the Oct4-targeted drug molecule NBMA (N-benzyl-4-methoxy-2-(1-(4-(trifluoromethyl)phenyl)vinyl)aniline) by computer-assisted technology, and found that it has a significant promoting effect on spermatogenesis in the established mouse azoospermia model. Subsequently, through transcriptome sequencing and enrichment analysis, real-time fluorescent quantitative PCR (qPCR) and western blot experiments revealed that NBMA promotes the differentiation of spermatogonial stem cells by activating the Oct4 pathway, thereby promoting spermatogenesis. This study proves that NBMA is a molecule with great potential to be developed as a therapeutic drug for azoospermia. It also shows that computer-assisted, chemical and biological multidisciplinary methods play a very important role in innovative drug discovery.

Replicating a GWAS: two novel candidate markers for oligospermia in Greek population

Genome-wide association studies have paved the way for the discovery of new markers regarding many diseases, including male infertility. A previous study on Caucasians highlighted 172 polymorphisms for their putative association with male infertility and we attempted to replicate these findings on our dataset comprising of Greek male individuals (n = 360). We retrieved 59 out of 172 polymorphisms and tested for all association models on 278 normospermic men and 82 patients with an abnormal seminogram, later separated into oligozoospermic and asthenozoospermic groups. Our findings indicate that two SNPs (rs2296225 in KIF17, rs7224496 in SMYD4) are associated with male infertility in the Greek population and have not been recorded in literature as of yet. These novel markers need further validation via additional studies and an increased individual number. All in all, replication studies, possess the power to validate existing polymorphisms found across all population and thus increase both statistical significance as well as identify novel potentially diagnostic markers.

Genome medicine in male infertility: From karyotyping to single-cell analysis

Male infertility is a multifactorial pathological condition that affects half of infertile couples. The majority of cases are categorized as idiopathic, especially in cases of nonobstructive azoospermia (NOA). An increasing number of genetic abnormalities have been shown to cause spermatogenic impairment with the development of microarray technologies and next-generation sequencing (NGS), moving beyond classical karyotype and polymerase chain reaction analyses of targeted genes. However, the majority of gene mutations, such as Klinefelter syndrome, azoospermia factor microdeletion, or congenital bilateral absence of the vas deferens, fail to function in a one gene-one phenotype manner. Single-cell transcriptome analysis performed using human testicular samples has begun to be published, which has brought about a more comprehensive understanding of testicular pathology. NGS also enables omics approaches, which provide more powerful tools to interrogate the genome, epigenome, transcriptome, and proteome. Simultaneously, the involvement of environmental factors and comorbidities, which may potentially regulate epigenetic factors, has been shown, resulting in a more complex understanding of the pathophysiology of spermatic disorders, especially NOA. The combination of phenotypic data and large amounts of bioinformatical data obtained by NGS may provide a more comprehensive understanding of the pathophysiology of male infertility, which will contribute not only to a diagnosis but also to the proper selection of infertility treatment and the development of new treatment modalities for male infertility.

Evaluation of Male Fertility-Associated Loci in a European Population of Patients with Severe Spermatogenic Impairment

Infertility is a growing concern in developed societies. Two extreme phenotypes of male infertility are non-obstructive azoospermia (NOA) and severe oligospermia (SO), which are characterized by severe spermatogenic failure (SpF). We designed a genetic association study comprising 725 Iberian infertile men as a consequence of SpF and 1058 unaffected controls to evaluate whether five single-nucleotide polymorphisms (SNPs), previously associated with reduced fertility in Hutterites, are also involved in the genetic susceptibility to idiopathic SpF and specific clinical entities. A significant difference in the allele frequencies of USP8-rs7174015 was observed under the recessive model between the NOA group and both the control group (p = 0.0226, OR = 1.33) and the SO group (p = 0.0048, OR = 1.78). Other genetic associations for EPSTI1-rs12870438 and PSAT1-rs7867029 with SO and between TUSC1-rs10966811 and testicular sperm extraction (TESE) success in the context of NOA were observed. In silico analysis of functional annotations demonstrated cis-eQTL effects of such SNPs likely due to the modification of binding motif sites for relevant transcription factors of the spermatogenic process. The findings reported here shed light on the molecular mechanisms leading to severe phenotypes of idiopathic male infertility, and may help to better understand the contribution of the common genetic variation to the development of these conditions.

Association of single-nucleotide polymorphisms in antioxidant genes and their gene-gene interactions with risk of male infertility in a Chinese population

The antioxidant defense system protects DNA from the damaging effects of oxidative stress and is hypothesized to be associated with an increased risk of male infertility. Polymorphisms in antioxidant genes and the gene-gene interactions associated with the antioxidant system may increase the potential risk of male infertility. In the present case-controlled study, the individual link between seven gene polymorphisms (NQO1 rs1800566, SOD2 rs4880, GSTM3 rs1571858, rs3814309, rs7483, GSTM5 rs11807 and GSTP1 rs1695) and the risk of male infertility was investigated. A total of 248 idiopathic infertility patients and 310 fertile controls were selected, and genotyping was performed using the Mass ARRAY platform. There were no significant associations between the seven polymorphisms and risk of male infertility. However, the analysis of gene-gene interactions showed a decreased risk of male infertility in GSTM3 rs3814309/NQO1 rs1800566 [CC x CT/TT; odds ratio (OR)=0.56, 95% confidence interval (CI)=0.34-0.92; P=0.022), and a significant association between a gene-gene interaction in GSTM3 rs1571858/NQO1 rs1800566 and azoospermia (AG/GG x CC; OR=3.84, 95% CI=1.25-11.81; P=0.019).

The impact of male infertility or intracytoplasmic sperm injection technique on perinatal outcomes

Objective: The aim of this study was to evaluate the impact of male infertility or intracytoplasmic sperm injection (ICSI) technique on perinatal outcomes.Materials and methods: A retrospective cohort study included patients with singleton live births after fresh-cycle embryo transfer that occurred between 1^st January 2016 and 31^st May 2018. The patients were divided into four groups: (1) IVF treatment without male infertility; (2) ICSI treatment without male infertility; (3) ICSI treatment with male infertility; and (4) IVF treatment with male infertility.Result: In total, 2118 patients were analyzed. When comparing perinatal outcomes between the four groups, there were significant differences with regard to gender proportions of offspring and GDM. No statistically significant differences were reported in the incidence of preterm birth, gestational hypertension, placenta previa, fetal malformation, macrosomia, or low birthweight. A separate multiple logistic regression model was performed for each abnormal perinatal outcome to eliminate confounding factors, with the exception of GDM, the above abnormal perinatal outcomes still did not differ significantly when comparing the four groups. However, the incidence of GDM was higher in the third group than it was in the first group. The proportion of male births was significantly decreased in the third and fourth groups.Conclusion: The results showed that ICSI may be associated with the risk of GDM in abnormal perinatal outcomes, but the risk is not due to male infertility. However, male infertility may reduce the proportion of male births.

Genetic Landscape of Nonobstructive Azoospermia and New Perspectives for the Clinic

Nonobstructive azoospermia (NOA) represents the most severe expression of male infertility, involving around 1% of the male population and 10% of infertile men. This condition is characterised by the inability of the testis to produce sperm cells, and it is considered to have an important genetic component. During the last two decades, different genetic anomalies, including microdeletions of the Y chromosome, karyotype defects, and missense mutations in genes involved in the reproductive function, have been described as the primary cause of NOA in many infertile men. However, these alterations only explain around 25% of azoospermic cases, with the remaining patients showing an idiopathic origin. Recent studies clearly suggest that the so-called idiopathic NOA has a complex aetiology with a polygenic inheritance, which may alter the spermatogenic process. Although we are far from a complete understanding of the molecular mechanisms underlying NOA, the use of the new technologies for genetic analysis has enabled a considerable increase in knowledge during the last years. In this review, we will provide a comprehensive and updated overview of the genetic basis of NOA, with a special focus on the possible application of the recent insights in clinical practice.

Genome-wide association study identifies ERBB4 on 2q34 as a novel locus associated with sperm motility in Japanese men

Background

The decrease in sperm motility has a potent influence on fertilisation. Sperm motility, represented as the percentage of motile sperm in ejaculated sperms, is influenced by lifestyle habits or environmental factors and by inherited factors. However, genetic factors contributing to individual differences in sperm motility remain unclear. To identify genetic factors that influence human sperm motility, we performed a genome-wide association study (GWAS) of sperm motility.

Methods

A two-stage GWAS was conducted using 811 Japanese men in a discovery stage, followed by a replication study using an additional 779 Japanese men.

Results

In the two-staged GWAS, a single nucleotide polymorphism rs3791686 in the intron of gene for erb-b2 receptor tyrosine kinase 4 (ERBB4) on chromosome 2q34 was identified as a novel locus for sperm motility, as evident from the discovery and replication results using meta-analysis (β=−4.01, combined P=5.40×10⁻⁹).

Conclusions

Together with the previous evidence that Sertoli cell-specific Erbb4-knockout mice display an impaired ability to produce motile sperm, this finding provides the first genetic evidence for further investigation of the genome-wide significant association at the ERBB4 locus in larger studies across diverse human populations.

Association of TUSC1 and DPF3 gene polymorphisms with male infertility

PURPOSE

Recently, genome-wide association studies of a Hutterite population in the USA revealed that five single nucleotide polymorphisms (SNPs) with a significant association with sperm quality and/or function in ethnically diverse men from Chicago were significantly correlated with family size. Of these, three SNPs (rs7867029, rs7174015, and rs12870438) were found to be significantly associated with the risk of azoospermia and/or oligozoospermia in a Japanese population. In this study, we investigated whether the rs10966811 (located in an intergenic region between the TUSC1 and IZUMO3 genes) and rs10129954 (located in the DPF3 gene) SNPs, previously related to family size, are associated with male infertility. In addition, we performed association analysis between rs12348 in TUSC1 and rs2772579 in IZUMO3 and male infertility.

METHODS

We genotyped 145 patients with infertility (including 83 patients with azoospermia and 62 with oligozoospermia) and 713 fertile controls by PCR-RFLP technique for polymorphism. Because rs10966811 has no restriction sites, the SNP rs12376894 with strong linkage disequilibrium was selected as an alternative to rs10966811.

RESULTS

There was a statistically significant association between rs12376894 proxy SNP of rs10966811 and oligozoospermia. Also, a statistically significant association between rs10129954 and azoospermia, and oligozoospermia was observed. When we assessed the relationship between rs12348 in TUSC1 and rs2772579 in IZUMO3 and male infertility traits, we found that rs12348 in TUSC1 was significantly associated with azoospermia and oligozoospermia, but rs2772579 in IZUMO3 was not associated with male infertility.

CONCLUSION

We found that the polymorphisms in TUSC1 and DPF3 displayed strong associations with male infertility.

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.

An independent validation study of three single nucleotide polymorphisms at the sex hormone-binding globulin locus for testosterone levels identified by genome-wide association studies

Study question

Are the single nucleotide polymorphisms (SNPs) rs2075230, rs6259 and rs727428 at the sex hormone-binding globulin (SHBG) locus, which were identified by genome-wide association studies (GWASs) for testosterone levels, associated with testosterone levels in Japanese men?

Summary answer

The SNP rs2075230, but not rs6259 and rs727428, is significantly associated with testosterone levels in Japanese men.

What is already known

Previous GWASs have revealed that rs2075230 is associated with serum testosterone levels in 3495 Chinese men and rs6259 and rs727428 are associated with serum testosterone levels in 3225 men of European ancestry.

Study design, size, and duration

This is an independent validation study of 1687 Japanese men (901 in Cohort 1 and 786 in Cohort 2).

Participants/materials, setting and method

Cohort 1 (20.7 ± 1.7 years old, mean ± SD) and Cohort 2 (31.2 ± 4.8 years) included samples obtained from university students and partners of pregnant women, respectively. The three SNPs were genotyped using either TaqMan probes or restriction fragment length polymorphism PCR. Blood samples were drawn from the cubital vein of the study participants in the morning, and total testosterone and SHBG levels were measured using a time-resolved immunofluorometric assay. Association between each SNP and testosterone levels was evaluated by meta-analysis of the two Japanese male cohorts.

Main results and the role of chance

The age of the two cohorts was significantly different (P < 0.0001). We found that rs2075230 was significantly associated with serum testosterone levels (β_STD = 0.15, P = 7.2 × 10⁻⁶); however, rs6259 and rs727428 were not (β_STD = 0.17, P = 0.071; β_STD = 0.082, P = 0.017, respectively), after adjusting for multiple testing in a combined analysis of two Japanese male cohorts. Moreover, rs2075230, rs6259 and rs727428 were significantly associated with high SHBG levels (β_STD = 0.22, P = 3.4 × 10⁻¹²; β_STD = 0.23, P = 6.5 × 10⁻⁶ and β_STD = 0.21, P = 3.4 × 10⁻¹⁰, respectively).

Large scale data

Not applicable.

Limitations, reasons for caution

This study had differences in the age and background parameters of participants compared to those observed in previous GWASs. In addition, the average age of participants in the two cohorts in our study also differed from one another. Therefore, the average testosterone levels, which decrease with age, between studies or the two cohorts were different.

Wider implications of the findings

The three SNPs have a considerable effect on SHBG levels and hence may indirectly affect testosterone levels.

Study funding/competing interests

This study was supported partly by the Ministry of Health and Welfare of Japan (1013201) (to T.I.), Grant-in-Aids for Scientific Research (C) (26462461) (to Y.S.) and (23510242) (to A.Ta.) from the Japan Society for the Promotion of Science, the European Union (BMH4-CT96-0314) (to T.I.) and the Takeda Science Foundation (to A.Ta.). There are no conflicts of interest to declare.

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.

Genetics of male infertility: from research to clinic

Male infertility is a multifactorial complex disease with highly heterogeneous phenotypic representation and in at least 15% of cases, this condition is related to known genetic disorders, including both chromosomal and single-gene alterations. In about 40% of primary testicular failure, the etiology remains unknown and a portion of them is likely to be caused by not yet identified genetic anomalies. During the last 10 years, the search for 'hidden' genetic factors was largely unsuccessful in identifying recurrent genetic factors with potential clinical application. The armamentarium of diagnostic tests has been implemented only by the screening for Y chromosome-linked gr/gr deletion in those populations for which consistent data with risk estimate are available. On the other hand, it is clearly demonstrated by both single nucleotide polymorphisms and comparative genomic hybridization arrays, that there is a rare variant burden (especially relevant concerning deletions) in men with impaired spermatogenesis. In the era of next generation sequencing (NGS), we expect to expand our diagnostic skills, since mutations in several hundred genes can potentially lead to infertility and each of them is likely responsible for only a small fraction of cases. In this regard, system biology, which allows revealing possible gene interactions and common biological pathways, will provide an informative tool for NGS data interpretation. Although these novel approaches will certainly help in discovering 'hidden' genetic factors, a more comprehensive picture of the etiopathogenesis of idiopathic male infertility will only be achieved by a parallel investigation of the complex world of gene environmental interaction and epigenetics.

A replication study of a candidate locus for follicle-stimulating hormone levels and association analysis for semen quality traits in Japanese men

In men, follicle-stimulating hormone (FSH) acts on the seminiferous tubules and enhances spermatogenesis. Recently, a candidate locus (rs2414095) for FSH levels was identified by a genome-wide association study (GWAS) in Chinese men. The rs2414095 single-nucleotide polymorphism (SNP) is found on the third intron of the cytochrome P450, family 19, subfamily A, peptide 1 (CYP19A1) gene encoding an aromatase. In the present study, we performed a replication study in 1687 Japanese men (901 from cohort 1 and 786 from cohort 2) to assess whether this SNP is associated with circulating FSH levels. Furthermore, we investigated whether the rs2414095 SNP is correlated with semen quality traits in 2015 Japanese men (1224 from cohort 1 and 791 from cohort 2). The rs2414095 SNP was significantly associated with circulating FSH levels (β_STD=0.15, P=9.7 × 10^-5), sperm concentration (β_STD=0.073, P=0.032) and total sperm number (TSN) (β_STD=0.074, P=0.027) in a combined analysis of the two Japanese male cohorts. We successfully replicated, in Japanese men, the results of the previous GWAS for the rs2414095 SNP in Chinese men, and found that the rs2414095 SNP was related with sperm production.

A network-based method for the identification of putative genes related to infertility

BACKGROUND

Infertility has become one of the major health problems worldwide, with its incidence having risen markedly in recent decades. There is an urgent need to investigate the pathological mechanisms behind infertility and to design effective treatments. However, this is made difficult by the fact that various biological factors have been identified to be related to infertility, including genetic factors.

METHODS

A network-based method was established to identify new genes potentially related to infertility. A network constructed using human protein-protein interactions based on previously validated infertility-related genes enabled the identification of some novel candidate genes. These genes were then filtered by a permutation test and their functional and structural associations with infertility-related genes.

RESULTS

Our method identified 23 novel genes, which have strong functional and structural associations with previously validated infertility-related genes.

CONCLUSIONS

Substantial evidence indicates that the identified genes are strongly related to dysfunction of the four main biological processes of fertility: reproductive development and physiology, gametogenesis, meiosis and recombination, and hormone regulation.

GENERAL SIGNIFICANCE

The newly discovered genes may provide new directions for investigating infertility. This article is part of a Special Issue entitled "System Genetics" Guest Editor: Dr. Yudong Cai and Dr. Tao Huang.

Immune Infertility Should Be Positively Diagnosed Using an Accurate Method by Monitoring the Level of Anti-ACTL7a Antibody

Infertility is currently a major public health problem. Anti-sperm antibodies (ASAs) markedly reduce sperm quality, which can subsequently lead to male and/or female infertility. The accurate detection of ASAs derived from specific spermatozoa is, therefore, clinically useful. We have focused on the spermatozoa-specific expression protein ACTL7a for many years and have developed an enzyme-linked immunosorbent assay (ELISA) to detect the concentration of anti-ACTL7a antibodies in fertile sera (n = 267) and infertile sera (n = 193). Infertile sera were collected from the positive sera of tray agglutination tests (TAT), which is a routine ASA screening methodology. We found that the concentration of anti-ACTL7a antibodies was significantly higher in the infertile sera (than in the fertile sera, P < 0.0001) and much higher in the TAT ≥ 16 infertile sera. The ELISA was much better for male sera detection (AUC = 0.9899). If we set the standard at a strongly positive value (calculated by ROC curve), the positive predictive value of the antibody detection reached 100 percent, with a false positive rate of zero. The developed ELISA method for anti-ACTL7a antibody detection is therefore sensitive, accurate, and easy to perform, making it an excellent potential tool for future clinical use.

The "omics" of human male infertility: integrating big data in a systems biology approach

Spermatogenesis is a complex process in which >2300 genes are temporally and spatially regulated to form a terminally differentiated sperm cell that must maintain the ability to contribute to a totipotent embryo which can successfully differentiate into a healthy individual. This process is dependent on fidelity of the genome, epigenome, transcriptome, and proteome of the spermatogonia, supporting cells, and the resulting sperm cell. Infertility and/or disease risk may increase in the offspring if abnormalities are present. This review highlights the recent advances in our understanding of these processes in light of the "omics revolution". We briefly review each of these areas, as well as highlight areas of future study and needs to advance further.

CRISPR/Cas9-Mediated Rapid Generation of Multiple Mouse Lines Identified Ccdc63 as Essential for Spermiogenesis

Spermatozoa are flagellated cells whose role in fertilization is dependent on their ability to move towards an oocyte. The structure of the sperm flagella is highly conserved across species, and much of what is known about this structure is derived from studies utilizing animal models. One group of proteins essential for the movement of the flagella are the dyneins. Using the advanced technology of CRISPR/Cas9 we have targeted three dynein group members; Dnaic1, Wdr63 and Ccdc63 in mice. All three of these genes are expressed strongly in the testis. We generated mice with amino acid substitutions in Dnaic1 to analyze two specific phosphorylation events at S124 and S127, and generated simple knockouts of Wdr63 and Ccdc63. We found that the targeted phosphorylation sites in Dnaic1 were not essential for male fertility. Similarly, Wdr63 was not essential for male fertility; however, Ccdc63 removal resulted in sterile male mice due to shortened flagella. This study demonstrates the versatility of the CRISPR/Cas9 system to generate animal models of a highly complex system by introducing point mutations and simple knockouts in a fast and efficient manner.