Genetic factors contributing to human primary ciliary dyskinesia and male infertility

Potential role of dynein-related genes in the etiology of male infertility: A systematic review and a meta-analysis

BACKGROUND

The dynein-related genes may have a role in the etiology of male infertility, particularly in cases of impaired sperm motility.

OBJECTIVES

The goal of this review is to compile a list of the most important dynein-related candidate genes that may contribute to male factor infertility.

MATERIALS AND METHODS

Databases were searched using the keywords "dynein", "male", "infertility" and by applying strict inclusion criteria. A meta-analysis was also performed by using the eligible case-control studies. The odd ratios (OR), the Z-test score, and the level of significance were determined using a fixed model with a p value of 0.05. Funnel plots were used to check for publication bias.

RESULTS

There were 35 studies that met the inclusion criteria. There were a total of fifteen genes responsible for the production of dynein structural proteins, the production of dynein assembling factors, and potentially associated with male infertility. A total of five case-control studies were eligible for inclusion in the meta-analysis. Variants in the dynein-related genes were linked to an increased the risk of male infertility (OR = 21.52, 95% Confidence Interval (CI) 8.34 - 55.50, Z test = 6.35, p < 0.05). The percentage of heterogeneity, I² , was 47.00%. The lack of variants in the dynein genes was an advantage and this was statistically significant.

DISCUSSION

The results from the present review illustrate that pathogenic variants in genes both for dynein synthesis and for dynein assembly factors could be associated with isolated cases of male infertility without any other symptoms.

CONCLUSIONS

The genes addressed in this study, which are involved in both the production and assembly of dynein, could be used as molecular targets for future research into the etiology of sperm motility problems. This article is protected by copyright. All rights reserved.

Correlation between serum levels of reproductive hormones and testicular spermatogenic function in men with azoospermia

To investigate the serum levels of reproductive hormones in men with azoospermia and explore the correlation between abnormal reproductive hormones and the results of testicular biopsy and seminiferous extraction. The serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T), and pituitary prolactin (PRL), were measured by Radio immunoassay. Testicular biopsy was used to determine whether patient's had spermatozoa. Spearman's correlation analysis was used to analyse the correlation between LH, FSH, testicular volume, and spermatogenic function. Receiver operator characteristic (ROC) curves were used to evaluate the efficacy and significance of LH and FSH for the detection of spermatozoa and copy number variation sequencing (CNV-seq). Compared with the control group, the serum levels of FSH and LH in the azoospermia group were significantly up-regulated (p < 0.001). Prolactin (PRL) and testosterone levels did not differ significantly between the two groups (p > 0.05). The serum levels of FSH and LH were negatively correlated with testicular spermatogenic function and testicular volume. The areas under the ROC curves for determining FSH and LH potency by testicular biopsy with or without spermatozoa were 0.640 and 0.622, respectively. The areas under the ROC curves for the potency of FSH and LH, as judged by CNV detection results, were 0.523 and 0.534, respectively. Serum levels of FSH and LH are associated with azoospermia and may be of predictive significance in the clinical setting for the acquisition of spermatozoa by testicular biopsy.

Distinct Roles of NANOS1 and NANOS3 in the Cell Cycle and NANOS3-PUM1-FOXM1 Axis to Control G2/M Phase in a Human Primordial Germ Cell Model

Nanos RNA-binding proteins are critical factors of germline development throughout the animal kingdom and their dysfunction causes infertility. During evolution, mammalian Nanos paralogues adopted divergent roles in germ cell biology. However, the molecular basis behind this divergence, such as their target mRNAs, remains poorly understood. Our RNA-sequencing analysis in a human primordial germ cell model-TCam-2 cell line revealed distinct pools of genes involved in the cell cycle process downregulated upon NANOS1 and NANOS3 overexpression. We show that NANOS1 and NANOS3 proteins influence different stages of the cell cycle. Namely, NANOS1 is involved in the G1/S and NANOS3 in the G2/M phase transition. Many of their cell cycle targets are known infertility and cancer-germ cell genes. Moreover, NANOS3 in complex with RNA-binding protein PUM1 causes 3′UTR-mediated repression of FOXM1 mRNA encoding a transcription factor crucial for G2/M phase transition. Interestingly, while NANOS3 and PUM1 act as post-transcriptional repressors of FOXM1, FOXM1 potentially acts as a transcriptional activator of NANOS3, PUM1, and itself. Finally, by utilizing publicly available RNA-sequencing datasets, we show that the balance between FOXM1-NANOS3 and FOXM1-PUM1 expression levels is disrupted in testis cancer, suggesting a potential role in this disease.

A novel CCDC39 mutation causes multiple morphological abnormalities of the flagella in a primary ciliary dyskinesia patient

RESEARCH QUESTION

Male infertility is a widespread symptom in patients with primary ciliary dyskinesia (PCD). PCD-related male infertility is often caused by asthenozoospermia, with barely normal sperm morphology. Multiple morphological abnormalities of the sperm flagella (MMAF) are a major cause of asthenozoospermia, characterized by various malformed morphologies of sperm flagella. To date, a limited number of genes have been suggested to be involved in the pathogenesis of both PCD and MMAF. What other genes associated with both PCD and MMAF are waiting to be discovered?

DESIGN

Whole-exome sequencing (WES) was performed to identify the pathogenic mutation associated with MMAF in a PCD patient. Peripheral venous blood and semen samples were collected from the PCD patient. Transmission electron microscopy (TEM), immunofluorescence staining and western blotting were conducted to confirm the pathogenicity of the identified mutation.

RESULTS

A novel homozygous mutation in CCDC39, c.983 T>C (p. Leu328Pro), was identified in two PCD-affected siblings of a consanguineous family showing a typical PCD phenotype, while the proband was infertile, which is associated with characterized MMAF. Furthermore, TEM revealed the abnormal ultrastructure of the patient's sperm flagella. Moreover, immunofluorescence staining revealed that CCDC39 was almost undetectable in the spermatozoa, which was further confirmed by western blotting. The outcome of intracytoplasmic sperm injection (ICSI) in the patient with the CCDC39 mutation was also favourable.

CONCLUSION

This study demonstrates that a novel loss-of-function mutation of CCDC39 is involved in the pathogenesis of PCD and MMAF and initially reported that ICSI treatment has a good outcome. Therefore, the novel variant of CCDC39 contributes to the genetic diagnosis, counselling and treatment of male infertility in PCD patients with MMAF phenotype.

A report of pregnancy following ICSI in one of two sisters with familiar primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a disorder of structure and function of motor ciliary and dyskinetic activity of ciliary in the fallopian tubes of affected women and could lead to infertility in some cases. In vitro fertilisation (IVF) is a choice of treatment in infertile women with PCD, which could conquer the tubal dysfunction. In this case study, we report a PCD affected woman with infertility who was treated by IVF and pregnancy was achieved but it failed due to the spontaneous abortion. We also performed whole-exome sequencing for this case and her PCD-affected sister, which did not reveal any genetic abnormality related to the PCD or infertility.

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.

Ultrastructural Sperm Flagellum Defects in a Patient With CCDC39 Compound Heterozygous Mutations and Primary Ciliary Dyskinesia/Situs Viscerum Inversus

Introduction: Primary ciliary dyskinesia (PCD) is a rare autosomal recessive disease characterized by structural or functional motile cilia abnormalities. Up to 40 different genes seem, at the moment, to be involved in the pathogenesis of PCD. A number of ultrastructural defects have also been reported in sperm flagella, but the sperm mitochondrial membrane potential (MMP) has never been described in these cases.

Aim: The aim of this study was to report the sperm MMP and ultrastructural abnormalities of the sperm flagella found in a patient with PCD and situs inversus (Kartagener syndrome) and its characterization from the genetic point of view.

Methods: Transmission electronic microscopy (TEM) analysis was used to evaluate flagella ultrastructure. The genetic testing was performed by next-generation sequencing. Sperm DNA fragmentation and MMP were also evaluated by flow cytometry.

Results: We report here the case of an 18-year-old male patient with PCD and situs inversus and severe oligo-astheno-teratozoospermia. TEM analysis of his spermatozoa showed an abnormal connecting piece. The mid piece appeared abnormally thickened, with cytoplasmic residue, dysplasia of fibrous sheath, loss of the outer dynein arms (ODAs), truncated inner dynein arms, and supernumerary outer fibers. The percentage of spermatozoa with fragmented DNA was normal, whereas a high percentage of spermatozoa had low MMP, suggesting an altered mitochondrial function. The genetic analysis showed the presence of c.610-2A > G, p.Arg811Cys compound heterozygous mutations in the CCDC39 gene.

Conclusion: The case herein reported suggests that the high percentage of sperm with low MMP may play a role in the pathogenesis of asthenozoospermia in patients with Kartagener syndrome. In addition, we report, for the first time, the missense variant p.Arg811Cys in the CCDC39 gene in a patient with Kartagener syndrome. Although in silico analysis predicts its damaging potential, its clinical meaning remains unclear.

Genetic disorders and male infertility

BACKGROUND

At present, one out of six couples is infertile, and in 50% of cases, infertility is attributed to male infertility factors. Genetic abnormalities are found in 10%-20% of patients showing severe spermatogenesis disorders, including non-obstructive azoospermia.

METHODS

Literatures covering the relationship between male infertility and genetic disorders or chromosomal abnormalities were studied and summarized.

MAIN FINDINGS RESULTS

Genetic disorders, including Klinefelter syndrome, balanced reciprocal translocation, Robertsonian translocation, structural abnormalities in Y chromosome, XX male, azoospermic factor (AZF) deletions, and congenital bilateral absence of vas deferens were summarized and discussed from a practical point of view. Among them, understanding on AZF deletions significantly changed owing to advanced elucidation of their pathogenesis. Due to its technical progress, AZF deletion test can reveal their delicate variations and predict the condition of spermatogenesis. Thirty-nine candidate genes possibly responsible for azoospermia have been identified in the last 10 years owing to the advances in genome sequencing technologies.

CONCLUSION

Genetic testing for chromosomes and AZF deletions should be examined in cases of severe oligozoospermia and azoospermia. Genetic counseling should be offered before and after genetic testing.

A DNAH17 missense variant causes flagella destabilization and asthenozoospermia

Using mice modelling patients’ variant, this study demonstrates that a homozygous DNAH17 missense variant causes asthenozoospermia and specifically destabilizes microtubule doublets 4–7 in flagella, which could be largely due to the storage of sperm in epididymis.

Asthenozoospermia is a common cause of male infertility, but its etiology remains incompletely understood. We recruited three Pakistani infertile brothers, born to first-cousin parents, displaying idiopathic asthenozoospermia but no ciliary-related symptoms. Whole-exome sequencing identified a missense variant (c.G5408A, p.C1803Y) in DNAH17, a functionally uncharacterized gene, recessively cosegregating with asthenozoospermia in the family. DNAH17, specifically expressed in testes, was localized to sperm flagella, and the mutation did not alter its localization. However, spermatozoa of all three patients showed higher frequencies of microtubule doublet(s) 4–7 missing at principal piece and end piece than in controls. Mice carrying a homozygous mutation (Dnah17^M/M) equivalent to that in patients recapitulated the defects in patients’ sperm tails. Further examinations revealed that the doublets 4–7 were destabilized largely due to the storage of sperm in epididymis. Altogether, we first report that a homozygous DNAH17 missense variant specifically induces doublets 4–7 destabilization and consequently causes asthenozoospermia, providing a novel marker for genetic counseling and diagnosis of male infertility.

Analysis of the sperm flagellar axoneme using gene-modified mice

Infertility is a global health issue that affects 1 in 6 couples, with male factors contributing to 50% of cases. The flagellar axoneme is a motility apparatus of spermatozoa, and disruption of its structure or function could lead to male infertility. The axoneme consists of a "9+2" structure that contains a central pair of two singlet microtubules surrounded by nine doublet microtubules, in addition to several macromolecular complexes such as dynein arms, radial spokes, and nexin-dynein regulatory complexes. Molecular components of the flagellar axoneme are evolutionally conserved from unicellular flagellates to mammals, including mice. Although knockout (KO) mice have been generated to understand their function in the formation and motility regulation of sperm flagella, the majority of KO mice die before sexual maturation due to impaired ciliary motility, which makes it challenging to analyze mature spermatozoa. In this review, we introduce methods that have been used to overcome premature lethality, focusing on KO mouse lines of central pair components.

Biallelic mutations of CFAP74 may cause human primary ciliary dyskinesia and MMAF phenotype

Primary ciliary dyskinesia (PCD) is a rare genetic disorder characterized by recurrent respiratory infections, nasosinusitis, tympanitis, and/or male infertility, all of which can severely impair the patient's quality of life. Multiple morphological abnormalities of the sperm flagella (MMAF) is one type of severe teratozoospermia and results from a variety of flagellar defects. In this study, we conducted whole-exome sequencing to identify and evaluate the genetic lesions in two patients with potential PCD and MMAF. Biallelic mutations in exon 10, c.983G>A; p.(Gly328Asp), and exon 29, c.3532G>A; p.(Asp1178Asn), of the CFAP74 (NM_001304360) gene were identified in patient 1 (P1), and biallelic mutations in exon 7, c.652C>T; p.(Arg218Trp), and exon 35, c. 4331G>C; p.(Ser1444Thr), of the same gene were identified in patient 2 (P2). Bioinformatic analysis suggested that these variants may be disease causing. Immunofluorescence confirmed that CFAP74 was absent in these patients' sperm samples. Intracytoplasmic sperm injection (ICSI) was carried out for P1, and his wife became pregnant after embryo transfer and gave birth to a healthy baby. To the best of our knowledge, this study is the first to identify the importance of CFAP74 in potential PCD and MMAF, contributing to the genetic diagnosis of these disorders and helping to predict pregnancy outcomes relevant in in vitro fertilization.

Male Infertility Diagnosis: Improvement of Genetic Analysis Performance by the Introduction of Pre-Diagnostic Genes in a Next-Generation Sequencing Custom-Made Panel

BACKGROUND

Infertility affects about 7% of the general male population. The underlying cause of male infertility is undefined in about 50% of cases (idiopathic infertility). The number of genes involved in human spermatogenesis is over two thousand. Therefore, it is essential to analyze a large number of genes that may be involved in male infertility. This study aimed to test idiopathic male infertile patients negative for a validated panel of "diagnostic" genes, for a wide panel of genes that we have defined as "pre-diagnostic."

METHODS

We developed a next-generation sequencing (NGS) gene panel including 65 pre-diagnostic genes that were used in 12 patients who were negative to a diagnostic genetic test for male infertility disorders, including primary spermatogenic failure and central hypogonadism, consisting of 110 genes.

RESULTS

After NGS sequencing, variants in pre-diagnostic genes were identified in 10/12 patients who were negative to a diagnostic test for primary spermatogenic failure (n = 9) or central hypogonadism (n = 1) due to mutations of single genes. Two pathogenic variants of DNAH5 and CFTR genes and three uncertain significance variants of DNAI1, DNAH11, and CCDC40 genes were found. Moreover, three variants with high impact were found in AMELY, CATSPER 2, and ADCY10 genes.

CONCLUSION

This study suggests that searching for pre-diagnostic genes may be of relevance to find the cause of infertility in patients with apparently idiopathic primary spermatogenic failure due to mutations of single genes and central hypogonadism.

Biallelic mutations in CFAP65 lead to severe asthenoteratospermia due to acrosome hypoplasia and flagellum malformations

Background

The genetic causes for most male infertility due to severe asthenozoospermia remain unclear.

Objective

Our objective was to identify unknown genetic factors in 47 patients with severe asthenozoospermia from 45 unrelated Chinese families.

Methods

We performed whole exome sequencing of 47 individuals with severe asthenozoospermia from 45 unrelated families. Mutation screening was performed in a control cohort of 637 individuals, including 219 with oligoasthenospermia, 195 with non-obstructive azoospermia and 223 fertile controls. Ultrastructural and immunostaining analyses of patients’ spermatozoa were performed to characterise the effect of variants.

Results

One homozygous non-sense mutation (NM_194302, c.G5341T:p.E1781X), two compound heterozygous mutations (c.C2284T:p.R762X and c.1751delC:p.P584fs) and two compound heterozygous mutations (c.5714_5721del:p.L1905fs and c.C3021A:p.N1007K) were identified in CFAP65 of three individuals with completely immotile spermatozoa, respectively. No biallelic deleterious variants of CFAP65 were detected in the control cohort of 637 individuals. Ultrastructural and immunostaining analyses of spermatozoa from two patients showed highly aberrant sperm morphology with severe defects such as acrosome hypoplasia, disruption of the mitochondrial sheath and absence of the central pair complex.

Conclusion

To the best of our knowledge, we are the first to report that CFAP65 mutations may cause spermatozoa to be completely immotile.

Where are we going with gene screening for male infertility?

Male infertility is a heterogenous disease process requiring the proper functioning and interaction of thousands of genes. Given the number of genes involved, it is thought that genetic causes contribute to most cases of infertility. Identifying these causes, however, is challenging. Infertility is associated with negative health outcomes, such as cancer, highlighting the need to further understand the genetic underpinnings of this condition. This paper describes the genetic and genomic tests currently available to identify the etiology of male infertility and then will discuss emerging technologies that may facilitate diagnosis and treatment of in the future.

New insights into the genetics of spermatogenic failure: a review of the literature

Genetic anomalies are known to affect about 15% of infertile patients with azoospermia or severe oligozoospermia. Despite a throughout diagnostic work-up, in up to the 72% of the male partners of infertile couples, no etiological factor can be found; hence, the cause of infertility remains unclear. Recently, several novel genetic causes of spermatogenic failure (SPGF) have been described. The aim of this review was to collect all the available evidence of SPGF genetics, matching data from in-vitro and animal models with those in human beings to provide a comprehensive and updated overview of the genes capable of affecting spermatogenesis. By reviewing the literature, we provided a list of 60 candidate genes for SPGF. Their investigation by Next Generation Sequencing in large cohorts of patients with apparently idiopathic infertility would provide new interesting data about their racial- and ethnic-related prevalence in infertile patients, likely raising the diagnostic yields. We propose a phenotype-based approach to identify the genes to look for.

Microtubular Dysfunction and Male Infertility

Microtubules are the prime component of the cytoskeleton along with microfilaments. Being vital for organelle transport and cellular divisions during spermatogenesis and sperm motility process, microtubules ascertain functional capacity of sperm. Also, microtubule based structures such as axoneme and manchette are crucial for sperm head and tail formation. This review (a) presents a concise, yet detailed structural overview of the microtubules, (b) analyses the role of microtubule structures in various male reproductive functions, and (c) presents the association of microtubular dysfunctions with male infertility. Considering the immense importance of microtubule structures in the formation and maintenance of physiological functions of sperm cells, this review serves as a scientific trigger in stimulating further male infertility research in this direction.

Ran-binding protein M is associated with human spermatogenesis and oogenesis

The aim of the present study was to explore the underlying mechanism and diagnostic potential of Ran-binding protein M (RanBPM) in human spermatogenesis and oogenesis. RanBPM expression in human testis and ovaries was analysed using polymerase chain reaction (PCR) and western blotting, and immunofluorescence was performed on testis and ovary tissue sections during different developmental stages of spermatogenesis and oogenesis using RanBPM antibodies. Interactions with a variety of functional proteins were also investigated. RanBPM mRNA and protein expression levels were determined by PCR and western blotting in the tissue sections. Results revealed that the mRNA expression levels were highest in the testis followed by the ovary. The RanBPM protein was predominantly localized in the nucleus of germ cells, and the expression levels were highest in pachytene spermatocytes and cells surrounding spermatids in testis tissue. In ovary cells, RanBPM was localized in the nucleus and cytoplasm. In conclusion, the results suggested that RanBPM may have multiple roles in the regulation of germ cell proliferation during human spermatogenesis and oogenesis. This research may provide a novel insight into the underlying molecular mechanism of RanBPM and may have implications for the clinical diagnosis and treatment of human 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.