Mendelian genetics of male infertility

S100a9 might act as a modulator of the Toll-like receptor 4 transduction pathway in chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyp (CRSwNP) is a highly prevalent disorder characterized by persistent nasal and sinus mucosa inflammation. Despite significant morbidity and decreased quality of life, there are limited effective treatment options for such a disease. Therefore, identifying causal genes and dysregulated pathways paves the way for novel therapeutic interventions. In the current study, a three-way interaction approach was used to detect dynamic co-expression interactions involved in CRSwNP. In this approach, the internal evolution of the co-expression relation between a pair of genes (X, Y) was captured under a change in the expression profile of a third gene (Z), named the switch gene. Subsequently, the biological relevancy of the statistically significant triplets was confirmed using both gene set enrichment analysis and gene regulatory network reconstruction. Finally, the importance of identified switch genes was confirmed using a random forest model. The results suggested four dysregulated pathways in CRSwNP, including "positive regulation of intracellular signal transduction", "arachidonic acid metabolic process", "spermatogenesis" and "negative regulation of cellular protein metabolic process". Additionally, the S100a9 as a switch gene together with the gene pair {Cd14, Tpd52l1} form a biologically relevant triplet. More specifically, we suggested that S100a9 might act as a potential upstream modulator in toll-like receptor 4 transduction pathway in the major CRSwNP pathologies.

Etiology of Male Infertility: an Update

Spermatogenesis is a complex process of germ cell division and differentiation that involves extensive cross-talk between the developing germ cells and the somatic testicular cells. Defective endocrine signaling and/or intrinsic defects within the testes can adversely affect spermatogenic progression, leading to subfertility/infertility. In recent years, male infertility has been recognized as a global public health concern, and research over the last few decades has elucidated the complex etiology of male infertility. Congenital reproductive abnormalities, genetic mutations, and endocrine/metabolic dysfunction have been demonstrated to be involved in infertility/subfertility in males. Furthermore, acquired factors like exposure to environmental toxicants and lifestyle-related disorders such as illicit use of psychoactive drugs have been shown to adversely affect spermatogenesis. Despite the large body of available scientific literature on the etiology of male infertility, a substantial proportion of infertility cases are idiopathic in nature, with no known cause. The inability to treat such idiopathic cases stems from poor knowledge about the complex regulation of spermatogenesis. Emerging scientific evidence indicates that defective functioning of testicular Sertoli cells (Sc) may be an underlying cause of infertility/subfertility in males. Sc plays an indispensable role in regulating spermatogenesis, and impaired functional maturation of Sc has been shown to affect fertility in animal models as well as humans, suggesting abnormal Sc as a potential underlying cause of reproductive insufficiency/failure in such cases of unexplained infertility. This review summarizes the major causes of infertility/subfertility in males, with an emphasis on infertility due to dysregulated Sc function.

Copy number variations (CNVs) and karyotyping analysis in males with azoospermia and oligospermia

BACKGROUND

Considering the essential roles that genetic factors play in azoospermia and oligospermia, this study aims to identify abnormal chromosomes using karyotyping and CNVs and elucidate the associated genes in patients.

METHODS

A total of 1157 azoospermia and oligospermia patients were recruited, of whom, 769 and 674 underwent next-generation sequencing (NGS) to identify CNVs and routine G-band karyotyping, respectively.

RESULTS

First, 286 patients were co-analyzed using CNV sequencing (CNV-seq) and karyotyping. Of the 725 and 432 patients with azoospermia and oligospermia, 33.8% and 48.9% had abnormal karyotypes and CNVs, respectively. In particular, 47,XXY accounted for 44.18% and 26.33% of abnormal karyotypes and CNVs, respectively, representing the most frequent genetic aberration in azoospermia and oligospermia patients. Nevertheless, big Y and small Y accounted for 7.46% and 16.67% of abnormal karyotypes, respectively. We also identified high-frequency CNVs-loci, such as Xp22.31 and 2p24.3, in azoospermia and oligospermia patients.

CONCLUSION

Sex chromosome and autosomal CNV loci, such as Xp22.31 and 2p24.3, as well as the associated genes, such as VCX and NACAP9, could be candidate spermatogenesis genes. The high-frequency abnormal karyotypes, CNV loci, and hot genes represent new targets for future research.

Transcriptomic signatures for human male infertility

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

A pathogenic variant in the uncharacterized RNF212B gene results in severe aneuploidy male infertility and repeated IVF failure

Quantitative and qualitative spermatogenic impairments are major causes of men's infertility. Although in vitro fertilization (IVF) is effective, some couples persistently fail to conceive. To identify causal variants in patients with severe male infertility factor and repeated IVF failures, we sequenced the exome of two consanguineous family members who underwent several failed IVF cycles and were diagnosed with low sperm count and motility. We identified a rare homozygous nonsense mutation in a previously uncharacterized gene, RNF212B, as the causative variant. Recurrence was identified in another unrelated, infertile patient who also faced repeated failed IVF treatments. scRNA-seq demonstrated meiosis-specific expression of RNF212B. Sequence analysis located a protein domain known to be associated with aneuploidy, which can explain multiple IVF failures. Accordingly, FISH analysis revealed a high aneuploidy rate in the patients' sperm cells and their IVF embryos. Finally, inactivation of the Drosophila orthologs significantly reduced male fertility. Given that members of the evolutionary conserved RNF212 gene family are involved in meiotic recombination and crossover maturation, our findings indicate a critical role of RNF212B in meiosis, genome stability, and in human fertility. Since recombination is completely absent in Drosophila males, our findings may indicate an additional unrelated role for the RNF212-like paralogs in spermatogenesis.

Transcriptional Differences in Identical Twins With Different Reproductive Capacities: A Case Report

Disorders of sperm production can be classified quantitatively as oligospermia (low sperm count) or azoospermia (no sperm during ejaculation). Numerous genes have been implicated in spermatogenesis. We describe a case of two identical twins who presented with different reproductive capabilities. One brother was infertile due to azoospermia, and the other, although oligospermic, previously naturally fathered a child. They were found to have differential gene expression based on RNA sequencing analysis. In the man with azoospermia, we found elevated E2F1 and HOXB9 gene expressions when compared with his brother, suggesting that the increased RNA expression of these genes could influence sperm production.

Decoding the Spermatogenesis Program: New Insights from Transcriptomic Analyses

Spermatogenesis is a complex differentiation process coordinated spatiotemporally across and along seminiferous tubules. Cellular heterogeneity has made it challenging to obtain stage-specific molecular profiles of germ and somatic cells using bulk transcriptomic analyses. This has limited our ability to understand regulation of spermatogenesis and to integrate knowledge from model organisms to humans. The recent advancement of single-cell RNA-sequencing (scRNA-seq) technologies provides insights into the cell type diversity and molecular signatures in the testis. Fine-grained cell atlases of the testis contain both known and novel cell types and define the functional states along the germ cell developmental trajectory in many species. These atlases provide a reference system for integrated interspecies comparisons to discover mechanistic parallels and to enable future studies. Despite recent advances, we currently lack high-resolution data to probe germ cell-somatic cell interactions in the tissue environment, but the use of highly multiplexed spatial analysis technologies has begun to resolve this problem. Taken together, recent single-cell studies provide an improvedunderstanding of gametogenesis to examine underlying causes of infertility and enable the development of new therapeutic interventions.

The transcript integrity index (TII) provides a standard measure of sperm RNA

Standardizing RNA quality is key to interpreting RNA-seq data as a compromised sample can mask the underlying biology. The challenge remains when evaluating RNA quality in samples with high RNA fragmentation. For example, programmed fragmentation and cytoplasmic expulsion, integral to sperm maturation, is a prime example of the complexities of interpreting RNA-seq data, given that fragmentation can be random and\or targeted. To meet this challenge, we developed an algorithm that accurately measures RNA quality in samples with high fragmentation, such as spermatozoa. The integrity of 1,000 previously identified abundant sperm transcripts were independently visualized and evaluated using the Transcript Integrity Index (TII) algorithm to identify intact transcripts. Full-length transcripts from visual and the TII algorithm were evaluated for testis preference in humans using the GTEx tissues database. Samples were then filtered by the Interquartile Range (IQR), identifying those in which the greatest number of transcripts failed to pass the visual or TII thresholds. Transcript lists were overlapped, forming the set of intact transcripts used as TII standards. Each sample was re-evaluated as a function of this TII set of intact transcripts, with poor quality samples identified as those failing in the largest number of transcripts. While ontologically enriched in roles related to spermatogenesis and/or fertilization, samples did not segregate based on birth outcome. The TII algorithm proved an effective means to identify samples of similar quality from sperm, a cell type enriched in biologically fragmented RNAs. The algorithm should facilitate other studies using samples compromised by high levels of RNA fragmentation, such as Formalin-Fixed Paraffin-Embedded samples. Requisite to assessing male health, TII provides a solution to the long-sought-after standard that identifies samples of similar quality.

Canary in the Coal Mine? Male Infertility as a Marker of Overall Health

Male factor infertility is a common problem. Evidence is emerging regarding the spectrum of systemic disease and illness harbored by infertile men who otherwise appear healthy. In this review, we present evidence that infertile men have poor overall health and increased morbidity and mortality, increased rates of both genitourinary and non-genitourinary malignancy, and greater risks of systemic disease. The review also highlights numerous genetic conditions associated with male infertility as well as emerging translational evidence of genitourinary birth defects and their impact on male infertility. Finally, parallels to the overall health of infertile women are presented. This review highlights the importance of a comprehensive health evaluation of men who present for an infertility assessment.

A new MEIOB mutation is a recurrent cause for azoospermia and testicular meiotic arrest

STUDY QUESTION

Are there genetic variants that can be used for the clinical evaluation of azoospermic men?

SUMMARY ANSWER

A novel homozygous frame-shift mutation in the MEIOB gene was identified in three azoospermic patients from two different families.

WHAT IS KNOWN ALREADY

Up to 1% of all men have complete absence of sperm in the semen, a condition known as azoospermia. There are very few tools for determining the etiology of azoospermia and the likelihood of sperm cells in the testis. The MEIOB gene codes for a single-strand DNA binding protein required for DNA double-strand breaks repair during meiosis. MEIOB appears to be exclusively expressed in human and mouse testis, and MeioB knockout mice are azoospermic due to meiotic arrest.

STUDY DESIGN, SIZE, DURATION

Two brothers with non-obstructive azoospermia (NOA) underwent whole-exome sequencing followed by comprehensive bioinformatics analyses. Candidate variations were further screened in infertile and fertile men, as well as in public and local reference databases.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study included 159 infertile and 77 fertile men. The exomes of two Arab men were completely sequenced. In addition, 213 other men of the same Arab ethnicity (136 infertile and 77 fertile men) underwent restriction fragment length polymorphism (RFLP) screening, as did 21 NOA men, of other ethnicities, with testicular impairment of spermatocyte arrest. All of the infertile men underwent Y-chromosome microdeletion and CFTR gene mutation assessments. Comprehensive bioinformatics analyses were designed to uncover candidate mutations associated with azoospermia.

MAIN RESULTS AND THE ROLE OF CHANCE

A novel homozygous frame-shift mutation in the MEIOB gene was identified in two brothers of Arab ethnicity. This frame-shift is predicted to result in a truncated MEIOB protein, which lacks the conserved C-terminal DNA binding domain. RFLP screening of the mutation in 157 infertile men, including 112 NOA patients of Arab ethnicity, identified an additional unrelated NOA patient with the same homozygous mutation and a similar testicular impairment. This mutation was not found in available public databases (n > 160 000), nor in the 77 proven fertile men, nor in our database of local Israeli population variations derived from exome and genome sequencing data (n = 500).

LIMITATIONS, REASONS FOR CAUTION

We have thus far screened for only two specific MEIOB probable pathogenic mutations in a relatively small local cohort. Therefore, the relative incidence of MEIOB mutations in azoospermia should be further assessed in larger and diverse cohorts in order to determine the efficiency of MEIOB sequence screening for clinical evaluations.

WIDER IMPLICATIONS OF THE FINDINGS

The relatively high incidence of likely NOA-causing mutations in MEIOB that was found in our cohort supports the idea that a complete screening of this gene might be beneficial for clinical evaluation of NOA patients.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported in part by a grant to EA from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC grant agreement (616088). There are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Familial Infertility (Azoospermia and Cryptozoospermia) in Two Brothers-Carriers of t(1;7) Complex Chromosomal Rearrangement (CCR): Molecular Cytogenetic Analysis

Structural aberrations involving more than two breakpoints on two or more chromosomes are known as complex chromosomal rearrangements (CCRs). They can reduce fertility through gametogenesis arrest developed due to disrupted chromosomal pairing in the pachytene stage. We present a familial case of two infertile brothers (with azoospermia and cryptozoospermia) and their mother, carriers of an exceptional type of CCR involving chromosomes 1 and 7 and three breakpoints. The aim was to identify whether meiotic disruption was caused by CCR and/or genomic mutations. Additionally, we performed a literature survey for male CCR carriers with reproductive failures. The characterization of the CCR chromosomes and potential genomic aberrations was performed using: G-banding using trypsin and Giemsa staining (GTG banding), fluorescent in situ hybridization (FISH) (including multicolor FISH (mFISH) and bacterial artificial chromosome (BAC)-FISH), and genome-wide array comparative genomic hybridization (aCGH). The CCR description was established as: der(1)(1qter->1q42.3::1p21->1q42.3::7p14.3->7pter), der(7)(1pter->1p2 1::7p14.3->7qter). aCGH revealed three rare genes variants: ASMT, GARNL3, and SESTD1, which were ruled out due to unlikely biological functions. The aCGH analysis of three breakpoint CCR regions did not reveal copy number variations (CNVs) with biologically plausible genes. Synaptonemal complex evaluation (brother-1; spermatocytes II/oligobiopsy; the silver staining technique) showed incomplete conjugation of the chromosomes. Associations between CCR and the sex chromosomes (by FISH) were not found. A meiotic segregation pattern (brother-2; ejaculated spermatozoa; FISH) revealed 29.21% genetically normal/balanced spermatozoa. The aCGH analysis could not detect smaller intergenic CNVs of few kb or smaller (indels of single exons or few nucleotides). Since chromosomal aberrations frequently do not affect the phenotype of the carrier, in contrast to the negative influence on spermatogenesis, there is an obvious need for genomic sequencing to investigate the point mutations that may be responsible for the differences between the azoospermic and cryptozoospermic phenotypes observed in a family. Progeny from the same parents provide a unique opportunity to discover a novel genomic background of male infertility.

A homozygous RPL10L missense mutation associated with male factor infertility and severe oligozoospermia

OBJECTIVE

To identify the genetic cause of male factor infertility characterized by severe oligozoospermia.

DESIGN

Genetic studies.

SETTING

Medical university.

PATIENT(S)

Two infertile brothers with severe oligozoospermia in a consanguineous Han Chinese family, 414 additional patients with oligo-/azoospermia, and 223 fertile (control) subjects.

INVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Genetic analyses using whole-exome and Sanger sequencing were performed for two brothers with severe oligozoospermia. The effects of an identified candidate causative mutation were investigated in silico and in vitro. Whole-exome sequencing screening for the candidate mutation was conducted in 414 patients with oligo-/azoospermia and 223 fertile subjects.

RESULT(S)

A homozygous missense variant (NM_080746:c.A257C: p.H86P) in RPL10L was identified in the two affected brothers and shown to cosegregate with the severe oligozoospermia phenotype. The mutation was absent in public databases, including the 1000 Genomes Project and the Exome Aggregation Consortium. All queried databases predicted the mutation to be damaging, consistent with the fact that it decreased protein levels in vitro. Subsequent mutation screening identified three additional heterozygous RPL10L mutations in three of 414 subjects with oligo-/azoospermia, but no RPL10L mutations among 223 fertile subjects.

CONCLUSION(S)

Our findings implicate RPL10L as a novel candidate gene in the pathogenesis of human male factor infertility and severe oligozoospermia.

Variation analysis of SOX8 gene in Chinese men with non-obstructive azoospermia or oligozoospermia

Sox8, encoding a SRY-related HMG box transcription factor, is essential in Sertoli cells for germ cell differentiation via regulation of integrity of the blood-testis barrier (BTB) as well as Sertoli-germ cell adhesion. Inactivation of Sox8 gene in mice causes postnatal progressive spermatogenic failure, resulting in male infertility. This study aims to investigate whether variants of SOX8 contribute to pathogenesis of idiopathic non-obstructive azoospermia (NOA) or oligozoospermia. A case-control genetic study was conducted in which all exons and exon-intron boundaries of SOX8 gene were screened in 190 NOA and 139 oligozoospermia cases by Sanger sequencing. The detected variants were examined in 284 normospermic controls. Nine known single-nucleotide polymorphisms (SNPs) of SOX8 gene were identified, and four of them exist simultaneously in oligo/azoospermia patients. A comparison of allele/genotype frequencies of these variants showed no significant difference between oligo/azoospermia cases and controls. The results indicate that deleterious variants in SOX8 gene may not be a common cause for oligo/azoospermia in Chinese men. Considering ethnic diversity, SOX8 could not be ruled out as a candidate gene for male infertility. The role of SOX8-mediated Sertoli cell function and BTB integrity played in the pathogenesis of male infertility needs to be further explored in other populations.

TBC1D20 Is Essential for Mouse Blood-Testis Barrier Integrity Through Maintaining the Epithelial Phenotype and Modulating the Maturation of Sertoli Cells

Sertoli cells are important for spermatogenesis not only by directly interacting with germ line cells in the seminiferous epithelium but also by constituting the blood-testis barrier (BTB) structure to create a favorable environment for spermatogenesis. Blind sterile (bs) male mice are infertile, with excessive germ cell apoptosis and spermatogenesis arrest. TBC1D20 (TBC1 domain family member 20) deficiency has been identified as the causative mutation in bs mice. However, whether TBC1D20 loss of function also impairs BTB integrity, which further contributes to the failed spermatogenesis of bs male mice, remains unclear. In the present study, biotin tracer assay and transmission electron microscopy showed severely disrupted BTB integrity in bs testes. Compared to the wild-type Sertoli cells, BTB components of cultured bs Sertoli cells in vitro was perturbed with downregulation of E-cadherin, ZO-1, β-catenin, and Claudin 11. The obvious rearrangement of F-actin indicated disrupted epithelial-mesenchymal balance in TBC1D20-deficient Sertoli cells. The ability of bs Sertoli cells to maintain the clone formation of spermatogonia stem cells was also obviously limited. Furthermore, the decreasing of SOX9 (sex-determining region Y box 9) and WT1 (Wilms' tumor 1) and increasing of vimentin in bs Sertoli cells indicated that TBC1D20 loss of function attenuated the differentiation progression of bs Sertoli cells. In summary, TBC1D20 loss of function impedes the maturation of adult Sertoli cells and resulted in impaired BTB integrity, which is further implicated in the infertile phenotype of bs male mice.

Karyotypic abnormalities and molecular analysis of Y chromosome microdeletion in Iranian Azeri Turkish population infertile men

Infertility is one of the major health-threatening problems in communities which may lead to psychological problems among couples. Y chromosome abnormalities and microdeletions have recently been considered as one of the male infertility factors. The aim of this study was to evaluate different chromosomal disorders and azoospermia factor b (AZFb), AZFc and AZFd microdeletions in idiopathic non-obstructive oligo or azoospermia infertile men. One hundred infertile (78 azoospermia and 22 oligospermia) and 100 fertile men were included in this study. Luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels were evaluated by electrochemiluminescence. Karyotyping was performed according to standard methods and interpreted using the International System for Human Cytogenetic Nomenclature (ISHCN) recommendation. For Y chromosome microdeletion analysis, a multiplex polymerase chain reaction (PCR) was performed using STS primers. Higher FSH (24.32 ± 15.32 versus 8.02 ± 3.37, p < 0.0001) and LH (14.97 ± 8.26 versus 5.42 ± 2.73, p < 0.0001) were observed in infertile patients compared to their fertile counterpart. Additionally, 14% of infertile patients exhibited abnormal karyotype. The  frequency of Y chromosome microdeletions in azoospermic and oligospermic patients was 32.05% (25/78) and 0% (0/22), respectively. Additionally, in azoospermic patients, the highest microdeletion frequency was related to the AZFc region (80%). Our data indicate the presence of chromosomal changes in the most infertile men, suggesting karyotype and molecular analysis of Y chromosome microdeletions for genetic counseling before assisted reproduction.Abbreviations: ART: assisted reproductive technology; AZF: azoospermia factor; DAZ: deleted in azoospermia; FCS: fetal calf serum; FSH: follicle stimulating hormone; LH: luteinizing hormone; PCR: polymerase chain reaction; SRY: sex-determining region Y; STS: sequence-tagged sites.

DNA variants are an unlikely explanation for the changing quality of spermatozoa within the same individual

It has recently been suggested that the human sperm genome is highly unstable, which may be a reasonable explanation as to why men, even fertile men, produce defective spermatozoa. Furthermore, an unstable genome may also explain why the semen profile of the same man changes from one ejaculate to the next. As such, we took multiple ejaculates (between 3 and 6) from 7 individuals over a 6-month period and isolated sperm through density gradients. We then compared the DNA of: (i) good and poor-quality spermatozoa within the same ejaculate; and (ii) from multiple ejaculates from the same individual. Our results suggest that on a global level, DNA present within spermatozoa is actually quite stable and similar between both good and poor sperm. This is important information for the assisted reproductive community when it comes to sperm selection.

The risk of birth defects is not associated with semen parameters or mode of conception in offspring of men visiting a reproductive health clinic

STUDY QUESTION

What is the relationship between semen parameters and birth defect (BD) rates in offspring of men evaluated for infertility?

SUMMARY ANSWER

Among men undergoing infertility evaluation, there is no significant relationship between semen parameters and defect rates in live or still births, even when considering mode of conception.

WHAT IS KNOWN ALREADY

Approximately 15% of couples have fertility difficulties, with up to a 50% male factor contribution. An increased risk of BDs exists in couples using ART, particularly IVF and ICSI, but it is unknown if this related to the ART procedures or an underlying male factor.

STUDY DESIGN, SIZE, DURATION

To determine if the severity of male factor infertilty, as assessed via sperm quality and mode of conception, is associated with BD rates, we performed a retrospective cohort study. Fathers with semen analysis data in the Baylor College of Medicine Semen Database (BCMSD) were linked with their offspring using Texas Birth Defects Registry (TBDFR) data between 1999 and 2009. In this 10-year period, a total of 1382 men were identified in linkage between the BCMSD and TBDFR. A total of 109 infants with and 2115 infants without BDs were identified.

PARTICIPANTS/MATERIALS, SETTING, METHODS

To determine the association between BDs and semen parameters, we used hierarchical linear modeling to determine odds ratios between BD rates, semen parameters, and mode of conception before and after adjustment for paternal, maternal and birth covariates. Semen parameters were stratified based on thresholds defined by the WHO fifth edition laboratory manual for the examination and processing of human semen.

MAIN RESULTS AND THE ROLE OF CHANCE

In total 4.9% of 2224 infants were identified with a BD. No statistically significant association was observed between BD rates and semen parameters, before or after adjustment for covariates. The association between sperm concentration and BDs demonstrated an odds ratio (OR) of 1.07 (95% confidence interval: 0.63-1.83); motility: OR 0.91 (0.52-2.22); and total motile count: OR 1.21 (0.70-2.08). Likewise, mode of conception, including infertility treatment and ART, did not affect BD rates (P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

BDs recorded in the TBDFR only include live born infants or still births after 20 weeks, our study did not evaluate the effect of impaired semen parameters on developmental defects prior to 20 weeks of gestation. With 109 BDs, our statistical analysis was powered to detect moderate differences associated with particular semen parameters. Additionally, data about mode of conception was not available for 1053 of 2224 births.

WIDER IMPLICATIONS OF THE FINDINGS

BD rates are not associated with semen quality or mode of conception. The current study suggests that the severity of male factor infertility does not impact the rate of congenital anomalies. This information is important when counseling couples concerned about the relationship between impaired semen quality and BDs.

STUDY FUNDING/COMPETING INTEREST(S)

Supported in part by the NIH Men's Reproductive Health Research (MRHR) K12 HD073917 (D.J.L.), the Multidisciplinary K12 Urologic Research (KURe) Career Development Program (D.J.L.), P01HD36289 from the Eunice Kennedy Shriver National Institute for Child Health and Human Development, NIH (D.J.L.), and by U01DD000494 from the Centers for Disease Control and Prevention and the Title V Block Grant to the Texas Department of State Health Services. A.W.P. is a National Institutes of Health K08 Scholar supported by a Mentored Career Development Award (K08DK115835-01) from the from the National Institute of Diabetes and Digestive and Kidney Diseases. This work is also supported in part through a Urology Care Foundation Rising Stars in Urology Award (to A.W.P.) None of the authors has a conflict of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

Taste Receptors: New Players in Sperm Biology

Taste receptors were first described as sensory receptors located on the tongue, where they are expressed in small clusters of specialized epithelial cells. However, more studies were published in recent years pointing to an expression of these proteins not only in the oral cavity but throughout the body and thus to a physiological role beyond the tongue. The recent observation that taste receptors and components of the coupled taste transduction cascade are also expressed during the different phases of spermatogenesis as well as in mature spermatozoa from mouse to humans and the overlap between the ligand spectrum of taste receptors with compounds in the male and female reproductive organs makes it reasonable to assume that sperm "taste" these different cues in their natural microenvironments. This assumption is assisted by the recent observations of a reproductive phenotype of different mouse lines carrying a targeted deletion of a taste receptor gene as well as the finding of a significant correlation between human male infertility and some polymorphisms in taste receptors genes. In this review, we depict recent findings on the role of taste receptors in male fertility, especially focusing on their possible involvement in mechanisms underlying spermatogenesis and post testicular sperm maturation. We also highlight the impact of genetic deletions of taste receptors, as well as their polymorphisms on male reproduction.

Sex chromosomes-linked single-gene disorders involved in human infertility

Human infertility is a healthcare problem that has a worldwide impact. Genetic causes of human infertility include chromosomal aneuploidies and rearrangements and single-gene defects. The sex chromosomes (X and Y) are critical players in human fertility since they contain several genes essential for sex determination and reproductive traits for both men and women. This paper provides a review of the most common sex chromosomes-linked single-gene disorders involved in human infertility and their corresponding phenotypes. In addition to the Y-linked SRY gene, which mutations may cause XY gonadal dysgenesis and sex reversal, the deletions of genes present in AZF regions of the Y chromosome (DAZ, RBMY, DBY and USP9Y genes) are implicated in varying degrees of spermatogenic dysfunction. Furthermore, a list of X-linked genes (KAL1, NR0B1, AR, TEX11, FMR1, PGRMC1, BMP15 and POF1 and 2 regions genes (XPNPEP2, POF1B, DACH2, CHM and DIAPH2)) were reported to have critical roles in pubertal and reproductive deficiencies in humans, affecting only men, only women or both sexes. Mutations in these genes may be transmitted to the offspring by a dominant or a recessive inheritance.

Taste receptor polymorphisms and male infertility

STUDY QUESTION

Are polymorphisms of taste receptor genes associated with male infertility?

SUMMARY ANSWER

This study has showed the associations between three single nucleotide polymorphisms (SNPs) in taste receptors genes (TASR) and male infertility.

WHAT IS KNOWN ALREADY

Recent studies showed the expression of taste receptors in the testis and in spermatozoa, suggesting their possible role in infertility. The vast genetic variability in taste genes results in a large degree of diversity in various human phenotypes.

STUDY DESIGN, SIZE, DURATION

In this study, we genotyped 19 SNPs in 12 taste related genes in a total of 494 Caucasian male patients undergoing semen evaluation at the Centre of Couple Sterility of the Siena University Hospital. Consecutive patients were enrolled during infertility investigations from October 2014 to February 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Median age of the patients was 36 years (18-58) and 141 were smokers. Genotyping was performed using the allele-specific PCR. The statistical analysis was carried out using generalized linear model (GLM) to explore the association between age, smoking, the genetic polymorphisms and sperm parameters.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed that the homozygous carriers of the (G) allele of the TAS2R14-rs3741843 polymorphism showed a decreased sperm progressive motility compared to heterozygotes and (A) homozygotes (P = 0.003). Moreover, the homozygous carriers of the (T) allele of the TAS2R3-rs11763979 SNP showed fewer normal acrosome compared with the heterozygous and the homozygous carriers of the (G) allele (P = 0.002). Multiple comparisons correction was applied and the Bonferroni-corrected critical P-value was = 0.003.

LIMITATIONS, REASONS FOR CAUTION

The analysis is restricted to SNPs within genes and to men of Caucasian ancestry.

WIDER IMPLICATIONS OF THE FINDINGS

In silico analyses strongly point towards a functional effect of the two SNPs: TAS2R14-rs3741843 regulates TAS2R43 expression, a gene that is involved in cilia motility and therefore could influences sperm mobility; the (T) allele of TAS2R3-rs11763979 increases the expression of the WEE2 antisense RNA one gene (WEE2-AS1). According to Genotype-Tissue Expression (GTEx) project the WEE2 gene is expressed in the testes where presumably it has the role of down regulating meiotic cell division. It is plausible to hypothesize that the WEE2-AS1 increased expression may down regulate WEE2 which in turn can alter the natural timing of sperm maturation increasing the number of abnormal sperm cells.

STUDY FUNDING/COMPETING INTEREST(S)

None.

Point-of-care whole-exome sequencing of idiopathic male infertility

PURPOSE

Nonobstructive azoospermia (NOA) affects 1% of the male population; however, despite state-of-the-art clinical assessment, for most patients the cause is unknown. We capitalized on an analysis of multiplex families in the Middle East to identify highly penetrant genetic causes.

METHODS

We used whole-exome sequencing (WES) in 8 consanguineous families and combined newly discovered genes with previously reported ones to create a NOA gene panel, which was used to identify additional variants in 75 unrelated idiopathic NOA subjects and 74 fertile controls.

RESULTS

In five of eight families, we identified rare deleterious recessive variants in CCDC155, NANOS2, SPO11, TEX14, and WNK3 segregating with disease. These genes, which are novel to human NOA, have remarkable testis-specific expression, and murine functional evidence supports roles for them in spermatogenesis. Among 75 unrelated NOA subjects, we identified 4 (~5.3%) with additional recessive variants in these newly discovered genes and 6 with deleterious variants in previously reported NOA genes, yielding an overall genetic etiology for 13.3% subjects versus 0 fertile controls (p = 0.001).

CONCLUSION

NOA affects millions of men, many of whom remain idiopathic despite extensive laboratory evaluation. The genetic etiology for a substantial fraction of these patients (>50% familial and >10% sporadic) may be discovered by WES at the point of care.

Autosomal single-gene disorders involved in human infertility

Human infertility, defined as the inability to conceive after 1 year of unprotected intercourse, is a healthcare problem that has a worldwide impact. Genetic causes of human infertility are manifold. In addition to the chromosomal aneuploidies and rearrangements, single-gene defects can interfere with human fertility. This paper provides a review of the most common autosomal recessive and autosomal dominant single-gene disorders involved in human infertility. The genes reviewed are CFTR, SPATA16, AURKC, CATSPER1, GNRHR, MTHFR, SYCP3, SOX9, WT1 and NR5A1 genes. These genes may be expressed throughout the hypothalamic-pituitary–gonadal-outflow tract axis, and the phenotype of affected individuals varies considerably from varying degrees of spermatogenic dysfunction leading to various degrees of reduced sperm parameters, through hypogonadotropic hypogonadism reslting in pubertal deficiencies, until gonadal dysgenesis and XY and XX sex reversal. Furthermore, congenital bilateral absence of the vas deferens, as well as premature ovarian failure, have been reported to be associated with some single-gene defects.

A familial study of azoospermic men identifies three novel causative mutations in three new human azoospermia genes

PURPOSE

Up to 1% of all men experience azoospermia, a condition of complete absence of sperm in the semen. The mechanisms and genes involved in spermatogenesis are mainly studied in model organisms, and their relevance to humans is unclear because human genetic studies are very scarce. Our objective was to uncover novel human mutations and genes causing azoospermia due to testicular meiotic maturation arrest.

METHODS

Affected and unaffected siblings from three families were subjected to whole-exome or whole-genome sequencing, followed by comprehensive bioinformatics analyses to identify mutations suspected to cause azoospermia. These likely mutations were further screened in azoospermic and normozoospermic men and in men proven to be fertile, as well as in a reference database of local populations.

RESULTS

We identified three novel likely causative mutations of azoospermia in three genes: MEIOB, TEX14, and DNAH6. These genes are associated with different meiotic processes: meiotic crossovers, daughter cell abscission, and possibly rapid prophase movements.

CONCLUSION

The genes and pathways we identified are fundamental for delineating common causes of azoospermia originating in mutations affecting diverse meiotic processes and have great potential for accelerating approaches to diagnose, treat, and prevent infertility.Genet Med advance online publication 16 February 2017.

The genetic basis and fitness consequences of sperm midpiece size in deer mice

An extensive array of reproductive traits varies among species, yet the genetic mechanisms that enable divergence, often over short evolutionary timescales, remain elusive. Here we examine two sister-species of Peromyscus mice with divergent mating systems. We find that the promiscuous species produces sperm with longer midpiece than the monogamous species, and midpiece size correlates positively with competitive ability and swimming performance. Using forward genetics, we identify a gene associated with midpiece length: Prkar1a, which encodes the R1α regulatory subunit of PKA. R1α localizes to midpiece in Peromyscus and is differentially expressed in mature sperm of the two species yet is similarly abundant in the testis. We also show that genetic variation at this locus accurately predicts male reproductive success. Our findings suggest that rapid evolution of reproductive traits can occur through cell type-specific changes to ubiquitously expressed genes and have an important effect on fitness.

Across species there are large changes in sperm morphology, yet how and why is unclear. Here, the authors show in Peromyscus mice, that the sperm midpiece length influences swimming speed and male fertility, and is regulated by cell-type specific expression of a ubiquitously expressed gene, Prkar1a.

Severe impairment of male reproductive organ development in a low SMN expressing mouse model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is caused by low levels of survival motor neuron (SMN), a multifunctional protein essential for higher eukaryotes. While SMN is one of the most scrutinized proteins associated with neurodegeneration, its gender-specific role in vertebrates remains unknown. We utilized a mild SMA model (C/C model) to examine the impact of low SMN on growth and development of mammalian sex organs. We show impaired testis development, degenerated seminiferous tubules, reduced sperm count and low fertility in C/C males, but no overt sex organ phenotype in C/C females. Underscoring an increased requirement for SMN expression, wild type testis showed extremely high levels of SMN protein compared to other tissues. Our results revealed severe perturbations in pathways critical to C/C male reproductive organ development and function, including steroid biosynthesis, apoptosis, and spermatogenesis. Consistent with enhanced apoptosis in seminiferous tubules of C/C testes, we recorded a drastic increase in cells with DNA fragmentation. SMN was expressed at high levels in adult C/C testis due to an adult-specific splicing switch, but could not compensate for low levels during early testicular development. Our findings uncover novel hallmarks of SMA disease progression and link SMN to general male infertility.

Evidences of Polymorphism Associated with Circadian System and Risk of Pathologies: A Review of the Literature

The circadian system is a supraphysiological system that modulates different biological functions such as metabolism, sleep-wake, cellular proliferation, and body temperature. Different chronodisruptors have been identified, such as shift work, feeding time, long days, and stress. The environmental changes and our modern lifestyle can alter the circadian system and increase the risk of developing pathologies such as cancer, preeclampsia, diabetes, and mood disorder. This system is organized by transcriptional/tranductional feedback loops of clock genes Clock, Bmal1, Per1-3, and Cry1-2. How molecular components of the clock are able to influence the development of diseases and their risk relation with genetic components of polymorphism of clock genes is unknown. This research describes different genetic variations in the population and how these are associated with risk of cancer, metabolic diseases such as diabetes, obesity, and dyslipidemias, and also mood disorders such as depression, bipolar disease, excessive alcohol intake, and infertility. Finally, these findings will need to be implemented and evaluated at the level of genetic interaction and how the environment factors trigger the expression of these pathologies will be examined.

TauCstF-64 Mediates Correct mRNA Polyadenylation and Splicing of Activator and Repressor Isoforms of the Cyclic AMP-Responsive Element Modulator (CREM) in Mouse Testis

Spermatogenesis is coordinated by the spatial and temporal expression of many transcriptional and posttranscriptional factors. The cyclic AMP-responsive element modulator (CREM) gene encodes both activator and repressor isoforms that act as transcription factors to regulate spermiogenesis. We found that the testis-expressed paralog of CstF-64, tauCstF-64 (gene symbol Cstf2t), is involved in a polyadenylation site choice switch of Crem mRNA and leads to an overall decrease of the Crem mRNAs that are generated from internal promoters in Cstf2t(-/-) mice. More surprisingly, loss of tauCstF-64 also leads to alternative splicing of Crem exon 4, which contains an important activation domain. Thus, testis-specific CREMtau2 isoform protein levels are reduced in Cstf2t(-/-) mice. Consequently, expression of 15 CREM-regulated genes is decreased in testes of Cstf2t(-/-) mice at 25 days postpartum. These effects might further contribute to the infertility phenotype of these animals. This demonstrates that tauCstF-64 is an important stage-specific regulator of Crem mRNA processing that modulates the spatial and temporal expression of downstream stage-specific genes necessary for the proper development of sperm in mice.

Genomic and genetic variation in E2F transcription factor-1 in men with nonobstructive azoospermia

OBJECTIVE

To identify gene dosage changes associated with nonobstructive azoospermia (NOA) using array comparative genomic hybridization (aCGH).

DESIGN

Prospective study.

SETTING

Medical school.

PATIENT(S)

One hundred ten men with NOA and 78 fertile controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The study has four distinct analytic components: aCGH, a molecular karyotype that detects copy number variations (CNVs); Taqman CNV assays to validate CNVs; mutation identification by Sanger sequencing; and histological analyses of testicular tissues.

RESULT(S)

A microduplication at 20q11.22 encompassing E2F transcription factor-1 (E2F1) was identified in one of eight men with NOA analyzed using aCGH. CNVs were confirmed and in an additional 102 men with NOA screened using Taqman CNV assays, for a total of 110 NOA men analyzed for CNVs in E2F1. Eight of 110 (7.3%) NOA men had microduplications or microdeletions of E2F1 that were absent in fertile controls.

CONCLUSION(S)

E2F1 microduplications or microdeletions are present in men with NOA (7.3%). Duplications or deletions of E2F1 occur very rarely in the general population (0.011%), but E2F1 gene dosage changes, previously reported only in cancers, are present in a subset of NOA men. These results recapitulate the infertility phenotype seen in mice lacking or overexpressing E2f1.

Targeted disruption of the mouse testis-enriched gene Znf230 does not affect spermatogenesis or fertility

The mouse testis-enriched Znf230 gene, which encodes a type of RING finger protein, is present primarily in the nuclei of spermatogonia, the acrosome and the tail of spermatozoa. To investigate the role of Znf230 in spermatogenesis, we generated Znf230-deficient mice by disrupting Znf230 exon-5 and exon-6 using homologous recombination. The homozygous Znf230-knockout (KO) mice did not exhibit Znf230 mRNA expression and Znf230 protein production. Znf230 KO mice exhibited no obvious impairment in body growth or fertility. Male Znf230 KO mice had integral reproductive systems and mature sperm that were regular in number and shape. The developmental stages of male germ cells of Znf230 KO mice were also normal. We further examined variations in the transcriptomes of testicular tissue between Znf230 KO and wild-type mice through microarray analysis. The results showed that the mRNA level of one unclassified transcript 4921513I08Rik was increased and that the mRNA levels of three other transcripts, i.e., 4930448A20Rik, 4931431B13Rik and potassium channel tetramerisation domain containing 14(Kctd14), were reduced more than two-fold in Znf230 KO mice compared with wild-type mice. Using our current examination techniques, these findings suggested that Znf230 deficiency in mice may not affect growth, fertility or spermatogenesis.

Reduced selection and accumulation of deleterious mutations in genes exclusively expressed in men

Sex-limited selection can moderate the elimination of deleterious mutations from the population and contribute to the high prevalence of common human diseases. Accordingly, deleterious mutations in autosomal genes that are exclusively expressed in only one of the sexes undergo sex-limited selection and can reach higher frequencies than mutations similarly selected in both sexes. Here we show that the number of deleterious SNPs in genes exclusively expressed in men is twofold higher than in genes that are selected in both sexes. Additional analyses suggest that the increased number of damaging mutations we found in male-specific genes is due to reduced selection in females. These results are noteworthy since many of these male-specific genes are known to be crucial for male reproduction, and are thus likely to be under strong purifying selection. We suggest that inheritance of male-infertility-causative mutations through unaffected female lineages contributes to the high incidence of male infertility.

Generation of male differentiated germ cells from various types of stem cells

Infertility is a major and largely incurable disease caused by disruption and loss of germ cells. It affects 10-15% of couples, and male factor accounts for half of the cases. To obtain human male germ cells 'especially functional spermatids' is essential for treating male infertility. Currently, much progress has been made on generating male germ cells, including spermatogonia, spermatocytes, and spermatids, from various types of stem cells. These germ cells can also be used in investigation of the pathology of male infertility. In this review, we focused on advances on obtaining male differentiated germ cells from different kinds of stem cells, with an emphasis on the embryonic stem (ES) cells, the induced pluripotent stem (iPS) cells, and spermatogonial stem cells (SSCs). We illustrated the generation of male differentiated germ cells from ES cells, iPS cells and SSCs, and we summarized the phenotype for these stem cells, spermatocytes and spermatids. Moreover, we address the differentiation potentials of ES cells, iPS cells and SSCs. We also highlight the advantages, disadvantages and concerns on derivation of the differentiated male germ cells from several types of stem cells. The ability of generating mature and functional male gametes from stem cells could enable us to understand the precise etiology of male infertility and offer an invaluable source of autologous male gametes for treating male infertility of azoospermia patients.

Genetic variation in circadian rhythm genes CLOCK and ARNTL as risk factor for male infertility

BACKGROUND

The circadian system has a major role in maintaining homeostasis and proper body functions including reproductive capacity. The aim of this study was to examine whether there is an association between genetic variability in the primary clock genes CLOCK and ARNTL and male infertility in humans.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a case-control study, where we searched for an association between polymorphisms of CLOCK and ARNTL genes and male infertility in 961 Slovenian and Serbian Caucasian men. The study group consisted of 517 patients with idiopathic infertility and a control group of 444 fertile men. A statistically significant difference was found in genotype distribution between the two groups in the CLOCK gene: rs11932595 (p = 6·10(-5), q = 4·10(-4), OR equaled 1.9 with 95% CI 1.4-2.7), rs6811520 (p = 2·10(-3), q = 8·10(-3), OR = 1.7 with 95% CI 1.2-2.2) and rs6850524 (p = 0.01, q = 0.02, OR = 1.4 with 95% CI 1.1-1.9). Further analyses of haplotypes were consistent with genotyping results.

CONCLUSIONS/SIGNIFICANCE

We provide evidence that genetic variability in the CLOCK gene might be associated with male infertility warranting further confirmation and mechanistic investigations.

The bioinformatics tool box for reproductive biology

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

Genome-wide association study identifies candidate genes for male fertility traits in humans

Despite the fact that hundreds of genes are known to affect fertility in animal models, relatively little is known about genes that influence natural fertility in humans. To broadly survey genes contributing to variation in male fertility, we conducted a genome-wide association study (GWAS) of two fertility traits (family size and birth rate) in 269 married men who are members of a founder population of European descent that proscribes contraception and has large family sizes. Associations between ∼250,000 autosomal SNPs and the fertility traits were examined. A total of 41 SNPs with p ≤ 1 × 10(-4) for either trait were taken forward to a validation study of 123 ethnically diverse men from Chicago who had previously undergone semen analyses. Nine (22%) of the SNPs associated with reduced fertility in the GWAS were also associated with one or more of the ten measures of reduced sperm quantity and/or function, yielding 27 associations with p values < 0.05 and seven with p values < 0.01 in the validation study. On the basis of 5,000 permutations of our data, the probabilities of observing this many or more small p values were 0.0014 and 5.6 × 10(-4), respectively. Among the nine associated loci, outstanding candidates for male fertility genes include USP8, an essential deubiquitinating enzyme that has a role in acrosome assembly; UBD and EPSTI1, which have potential roles in innate immunity; and LRRC32, which encodes a latent transforming growth factor β (TGF-β) receptor on regulatory T cells. We suggest that mutations in these genes that are more severe may account for some of the unexplained infertility (or subfertility) in the general population.

Studying nonobstructive azoospermia in cystinosis: histologic examination of testes and epididymis and sperm analysis in a Ctns⁻/⁻ mouse model

OBJECTIVE

To study the pathogenesis of male infertility in cystinosis due to nonobstructive azoospermia, using a Ctns(-/-) mouse model.

DESIGN

Observational case-control study.

SETTING

Academic research laboratory.

ANIMAL(S)

Male C57BL/6 Ctns(-/-) mice were compared with C57BL/6 wild-type (wt) mice.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Fertility was studied using litter size (n = 3 vs. n = 2). After animals were sacrificed, testes, epididymis, and vas deferens were removed for testicular cystine measurements (n = 5 vs. n = 6), histologic studies (n = 3 vs. n = 3), and sperm analysis (n = 3 vs. n = 3).

RESULT(S)

Mean testicular cystine content was significantly higher in Ctns(-/-) mice compared with wt mice (26.6 ± 1.22 vs. 0.1 ± 0.01 nmol cystine/mg protein). Testes of Ctns(-/-) mice had lower weight compared with wt mice (0.096 ± 0.009 g vs. 0.112 ± 0.004 g), but mice fertility was similar (litter size 6.6 ± 1.4 vs. 6.3 ± 2.6 pups). Neither histologic nor sperm abnormalities were found.

CONCLUSION(S)

The Ctns(-/-) mouse model generated on C57BL/6 background is not suitable for clarifying the pathogenesis of male infertility in cystinosis. The etiology of nonobstructive azoospermia in these patients remains unclear.