Defective Spermatogenesis Research Articles

Male infertility in Sertoli cell-only syndrome: An investigation of autosomal gene defects.

To detect autosomal genetic defects and to determine candidate genes in Sertoli cell-only syndrome infertile men. Single-nucleotide polymorphism+comparative genomic hybridization microarray technology was carried out on 39 Sertoli cell-only syndrome infertile patients in the present study. Array comparative genomic hybridization compares the patient's genome against a reference genome, and identifies uncover deletions, amplifications and loss of heterozygosity. A link between defective spermatogenesis genes and infertility was examined, and amplifications and deletions in several genes were detected, including homeobox gene; synaptonemal complex element protein1; collagen, typeI, alpha1; imprinted maternally expressed transcript; and potassium voltage-gated channel subfamilyQ member1. The present data suggest that several genes can play an important role in spermatogenesis and progression of Sertoli cell-only syndrome.

Transgenerational Epigenetic Inheritance Is Negatively Regulated by the HERI-1 Chromodomain Protein.

Transgenerational epigenetic inheritance (TEI) is the inheritance of epigenetic information for two or more generations. In most cases, TEI is limited to a small number of generations (two to three). The short-term nature of TEI could be set by innate biochemical limitations to TEI or by genetically encoded systems that actively limit TEI. In Caenorhabditis elegans, double-stranded RNA (dsRNA)-mediated gene silencing [RNAi (RNA interference)] can be inherited (termed RNAi inheritance or RNA-directed TEI). To identify systems that might actively limit RNA-directed TEI, we conducted a forward genetic screen for factors whose mutation enhanced RNAi inheritance. This screen identified the gene heritable enhancer of RNAi (heri-1), whose mutation causes RNAi inheritance to last longer (> 20 generations) than normal. heri-1 encodes a protein with a chromodomain, and a kinase homology domain that is expressed in germ cells and localizes to nuclei. In C. elegans, a nuclear branch of the RNAi pathway [termed the nuclear RNAi or NRDE (nuclear RNA defective) pathway] promotes RNAi inheritance. We find that heri-1(-) animals have defects in spermatogenesis that are suppressible by mutations in the nuclear RNAi Argonaute (Ago) HRDE-1, suggesting that HERI-1 might normally act in sperm progenitor cells to limit nuclear RNAi and/or RNAi inheritance. Consistent with this idea, we find that the NRDE nuclear RNAi pathway is hyperresponsive to experimental RNAi treatments in heri-1 mutant animals. Interestingly, HERI-1 binds to genes targeted by RNAi, suggesting that HERI-1 may have a direct role in limiting nuclear RNAi and, therefore, RNAi inheritance. Finally, the recruitment of HERI-1 to chromatin depends upon the same factors that drive cotranscriptional gene silencing, suggesting that the generational perdurance of RNAi inheritance in C. elegans may be set by competing pro- and antisilencing outputs of the nuclear RNAi machinery.

Genetic Dissection of Hybrid Male Sterility Across Stages of Spermatogenesis.

Hybrid sterility is a common form of reproductive isolation between nascent species. Although hybrid sterility is routinely documented and genetically dissected in speciation studies, its developmental basis is rarely examined, especially in generations beyond the F1 generation. To identify phenotypic and genetic determinants of hybrid male sterility from a developmental perspective, we characterized testis histology in 312 F2 hybrids generated by intercrossing inbred strains of Mus musculus domesticus and M. m. musculus, two subspecies of house mice. Hybrids display a range of histologic abnormalities that indicate defective spermatogenesis. Among these abnormalities, we quantified decreased testis size, reductions in spermatocyte and spermatid number, increased apoptosis of meiosis I spermatocytes, and more multinucleated syncytia. Collectively, our phenotypic data point to defects in meiosis I as a primary barrier to reproduction. We identified seven quantitative trait loci (QTL) controlling five histologic traits. A region of chromosome 17 that contains Prdm9, a gene known to confer F1 hybrid male sterility, affects multinucleated syncytia and round spermatids, potentially extending the phenotypic outcomes of this incompatibility. The X chromosome also plays a key role, with loci affecting multinucleated syncytia, apoptosis of round spermatids, and round spermatid numbers. We detected an epistatic interaction between QTL on chromosomes 17 and X for multinucleated syncytia. Our results refine the developmental basis of a key reproductive barrier in a classic model system for speciation genetics.

Depletion of SMC5/6 sensitizes male germ cells to DNA damage.

The structural maintenance of chromosomes complex SMC5/6 is thought to be essential for DNA repair and chromosome segregation during mitosis and meiosis. To determine the requirements of the SMC5/6 complex during mouse spermatogenesis we combined a conditional knockout allele for Smc5, with four germ cell–specific Cre-recombinase transgenes, Ddx4-Cre, Stra8-Cre, Spo11-Cre, and Hspa2-Cre, to mutate Smc5 in spermatogonia, in spermatocytes before meiotic entry, during early meiotic stages, and during midmeiotic stages, respectively. Conditional mutation of Smc5 resulted in destabilization of the SMC5/6 complex. Despite this, we observed only mild defects in spermatogenesis. Mutation of Smc5 mediated by Ddx4-Cre and Stra8-Cre resulted in partial loss of preleptotene spermatocytes; however, spermatogenesis progresses and mice are fertile. Mutation of Smc5 via Spo11-Cre or Hspa2-Cre did not result in detectable defects of spermatogenesis. Upon exposure to gamma irradiation or etoposide treatment, each conditional Smc5 mutant demonstrated an increase in the number of enlarged round spermatids with multiple acrosomes and supernumerary chromosome content. We propose that the SMC5/6 complex is not acutely required for premeiotic DNA replication and meiotic progression during mouse spermatogenesis; however, when germ cells are challenged by exogenous DNA damage, the SMC5/6 complex ensures genome integrity, and thus, fertility.

MicroRNA-130a inhibits spermatogenesis by directly targeting androgen receptor in mouse Sertoli cells.

MicroRNAs (miRNAs) have been shown to play a key role in spermatogenesis. However, whether the miRNAs influence androgen/androgen receptor (AR) signaling during spermatogenesis remains unclear. Using a bioinformatic approach, a potential miRNA, miR-130a, which could bind to Ar-3'untranslated region directly was identified. The expression pattern of miR-130a was further characterized by quantitative real-time polymerase chain reaction. It was found that miR-130a was abundant in testis and its expression level was negatively correlated with age. Overexpression of miR-130a could inhibit AR expression both in vitro and in vivo. Moreover, the mice with an intratesticular injection of miR-130a showed defects in spermatogenesis and increased germ cell apoptosis. Taken together, these results suggest that miR-130a could negatively regulate AR expression in mouse Sertoli cell, which further cause defects in spermatogenesis.

The hpRNA/RNAi Pathway Is Essential to Resolve Intragenomic Conflict in the Drosophila Male Germline

Intragenomic conflicts are fueled by rapidly evolving selfish genetic elements, which induce selective pressures to innovate opposing repressive mechanisms. This is patently manifest in sex-ratio (SR) meiotic drive systems, in which distorter and suppressor factors bias and restore equal transmission of X and Y sperm. Here, we reveal that multiple SR suppressors in Drosophila simulans (Nmy and Tmy) encode related hairpin RNAs (hpRNAs), which generate endo-siRNAs that repress the paralogous distorters Dox and MDox. All components in this drive network are recently evolved and largely testis restricted. To connect SR hpRNA function to the RNAi pathway, we generated D.simulans null mutants of Dcr-2 and AGO2. Strikingly, these coreRNAi knockouts massively derepress Dox andMDox and are in fact completely male sterile and exhibit highly defective spermatogenesis. Altogether, our data reveal how the adaptive capacity of hpRNAs is critically deployed to restrict selfish gonadal genetic systems that can exterminate a species.

Vitamin E and lycopene reduce coal burning fluorosis-induced spermatogenic cell apoptosis via oxidative stress-mediated JNK and ERK signaling pathways.

Although fluoride has been widely used in toothpaste, mouthwash, and drinking water to prevent dental caries, the excessive intake of fluoride can cause fluorosis which is associated with dental, skeletal, and soft tissue fluorosis. Recent evidences have drawn the attention to its adverse effects on male reproductive system that include spermatogenesis defect, sperm count loss, and sperm maturation impairment. Fluoride induces oxidative stress through the activation of mitogen activated protein kinase (MAPK) cascade which can lead to cell apoptosis. Vitamin E (VE) and lycopene are two common antioxidants, being protective to reactive oxygen species (ROS)-induced toxic effects. However, whether and how these two antioxidants prevent fluoride-induced spermatogenic cell apoptosis are largely unknown. In the present study, a male rat model for coal burning fluorosis was established and the histological lesions and spermatogenic cell apoptosis in rat testes were observed. The decreased expression of clusterin, a heterodimeric glycoprotein reported to regulate spermatogenic cell apoptosis, was detected in fluoride-treated rat testes. Interestingly, the co-administration with VE or lycopene reduced fluorosis-mediated testicular toxicity and rescued clusterin expression. Further, fluoride caused the enhanced Jun N-terminal kinase (JNK, c-Jun) and extracellular signal-regulated protein kinase (ERK) phosphorylation, which was reduced by VE or lycopene. Thus, VE and lycopene prevent coal burning fluorosis-induced spermatogenic cell apoptosis through the suppression of oxidative stress-mediated JNK and ERK signaling pathway, which could be an alternative therapeutic strategy for the treatment of fluorosis.

Apoptosis Is a Demanding Selective Tool During the Development of Fetal Male Germ Cells.

Apoptosis is widely known to play a major role on diseases related to male infertility. Diseases of the male genital tract as defective spermatogenesis, decreased sperm motility, sperm DNA fragmentation, testicular torsion, varicocele and immunological infertility are strongly related to apoptotic cell death. Apoptosis must not be considered only as a fail on germ cell physiology or a secondary effect of certain pathologies and exogenous hazardous agents. Apoptosis orchestrates correct function and development of the male germ cell from the early embryonic stages of gonadal differentiation to the fertilization. In this review we have tried to address a reading frame of the main knowledge about apoptosis in male germ cell development. Focussing on mechanisms concerning cellular apoptosis, which are independent of exogenous stimuli, we aimed to highlight that apoptosis is a selective instrument that guarantees the delivery of genetic message to offspring.

Deletion of DDB1- and CUL4- associated factor-17 (Dcaf17) gene causes spermatogenesis defects and male infertility in mice

DDB1– and CUL4–associated factor 17 (Dcaf17) is a member of DCAF family genes that encode substrate receptor proteins for Cullin-RING E3 ubiquitin ligases, which play critical roles in many cellular processes. To unravel the function of DCAF17, we performed expression profiling of Dcaf17 in different tissues of wild type mouse by qRT-PCR and generated Dcaf17 knockout mice by gene targeting. Expression profiling of Dcaf17 showed highest expression in testis. Analyses of Dcaf17 transcripts during post-natal development of testis at different ages displayed gradual increase in Dcaf17 mRNA levels with the age. Although Dcaf17 disruption did not have any effect on female fertility, Dcaf17 deletion led to male infertility due to abnormal sperm development. The Dcaf17−/− mice produced low number of sperm with abnormal shape and significantly low motility. Histological examination of the Dcaf17−/− testis revealed impaired spermatogenesis with presence of vacuoles and sloughed cells in the seminiferous tubules. Disruption of Dcaf17 caused asymmetric acrosome capping, impaired nuclear compaction and abnormal round spermatid to elongated spermatid transition. For the first time, these data indicate that DCAF17 is essential for spermiogenesis.

Male mice with large inversions or deletions of X-chromosome palindrome arms are fertile and express their associated genes during post-meiosis

Large (>10 kb) palindromic sequences are enriched on mammalian sex chromosomes. In mice, these palindromes harbor gene families (≥2 gene copies) expressed exclusively in post-meiotic testicular germ cells, a time when most single-copy sex-linked genes are transcriptionally repressed. This observation led to the hypothesis that palindromic structures or having ≥2 gene copies enable post-meiotic gene expression. We tested these hypotheses by using CRISPR to precisely engineer large (10’s of kb) inversions and deletions of X-chromosome palindrome arms for two regions that carry the mouse 4930567H17Rik and Mageb5 palindrome gene families. We found that 4930567H17Rik and Mageb5 gene expression is unaffected in mice carrying palindrome arm inversions and halved in mice carrying palindrome arm deletions. We assessed whether palindrome-associated genes were sensitive to reduced expression in mice carrying palindrome arm deletions. Male mice carrying palindrome arm deletions are fertile and show no defects in post-meiotic spermatogenesis. Together, these findings suggest palindromic structures on the sex chromosomes are not necessary for their associated genes to evade post-meiotic transcriptional repression and that these genes are not sensitive to reduced expression levels. Large sex chromosome palindromes may be important for other reasons, such as promoting gene conversion between palindrome arms.

A novel mouse model of testicular granulosa cell tumors.

What is the role of dysregulated transforming growth factor beta (TGFB) signaling in the development of sex cord-stromal tumors in the testis? Overactivation of TGFB signaling results in the development of testicular tumors resembling granulosa cell tumors (GrCTs). In an earlier study, we demonstrated that constitutively active TGFB receptor 1 (TGFBR1) in ovarian somatic cells promotes the development of ovarian GrCTs. However, the consequence of dysregulation of TGFB signaling in the pathobiology of the testis, remains poorly defined. To identify the impact of dysregulation of TGFB signaling on the testis, we generated mice with constitutive activation of TGFBR1 using anti-Mullerian hormone receptor type 2 (Amhr2)-Cre recombinase. The effect of constitutively active TGFBR1 on testis development and the timeline of testicular tumor formation were examined. We further investigated the molecular features of testicular tumors and determined the expression of beta-catenin (CTNNB1) known to be involved in testicular GrCT development. Male mice with constitutive activation of TGFBR1 were examined at various developmental stages (i.e. from 1 week up to 6 months) along with controls. Testis samples were collected and processed for histological and molecular analyses, including haematoxylin and eosin (H and E) staining, real-time PCR, immunohistochemistry, immunofluorescence and western blotting. Immunostaining/immunoblotting and real-time PCR experiments were performed using at least three animals per genotype. Data are presented as mean ± SEM. Statistical significance was determined using unpaired two-tail t-test and reported when P value is <0.05. Mice harboring constitutively active TGFBR1 in the testes developed tumors resembling testicular GrCTs, a rare type of tumors in the testis. The formation of testicular tumors led to altered cell proliferation, loss of germ cells and defective spermatogenesis. Immunohistochemically, these tumors were positive for inhibin alpha (INHA), forkhead box O1 (FOXO1), and more importantly, forkhead box L2 (FOXL2), a protein specifically expressed in the ovary and required for normal granulosa cell differentiation and function. Consistent with the immunohistochemical findings, FOXL2 proteins were only detectable in testes of TGFBR1-CAAcre mice but not those of controls by western blotting, suggesting potential alteration of Sertoli cell fate. To explore mechanisms underlying the tumor-promoting effect of TGFBR1 overactivation, we examined the expression of CTNNB1. The results revealed increased expression of CTNNB1 in testicular tumors in TGFBR1-CAAcre mice. Collectively, this study uncovered tumorigenic function of enhanced TGFB signaling in the testis. N/A. This study was performed using mice, and the direct relevance of the experimental paradigm and findings to human testicular GrCTs awaits further investigation. Of note, constitutive activation of TGFBR1 was employed to enhance TGFB/SMAD signaling activity and may not be interpreted as the genetic cause of the disease. This mouse model may prove to be a useful addition to the mouse genetics toolkit for GrCT research. Our finding that dysregulation of TGFB signaling results in the development of testicular GrCTs supports a common origin between Sertoli cells and granulosa cells, and highlights the paramount importance of balanced TGFB signaling in reproduction and development. This research was supported by the National Institutes of Health grant R03HD082416 from the Eunice Kennedy Shriver National Institute of Child Health & Human Development and the New Faculty Start-up Funds from Texas A&M University awarded to Q.L. The authors declare no competing interest.

Melatonin protects prepuberal testis from deleterious effects of bisphenol A or diethylhexyl phthalate by preserving H3K9 methylation.

A growing number of couples experience fertility issues with almost half being due to malefactors. The exposure to toxic environmental contaminants, such as endocrine disruptors (EDs), has been shown to negatively affect male fertility. EDs are present in the environment, and exposure to these toxins results in the failure of spermatogenesis. The deleterious effects of EDs on spermatogenesis have been well documented, whereas improvement of infertility associated with spermatogenesis defects remains a great challenge. Herein, we report that in vitro exposure of prepuberal mouse testes to two well-known endocrine disruptors (EDs), bisphenol A (BPA) or diethylhexyl phthalate (DEHP), impairs spermatogenesis with perturbing self-renewal, spermatogonia activity, and meiosis. Evidence indicates that such effects are likely due, at least in part, to decreased G9a-dependent H3K9 di-methylation. Of note, we found that melatonin (MLT) protected the testis from the negative ED impacts with preserving spermatogonia stem and meiotic cells, along with maintaining normal H3K9 di-methylation in these cells. Taken together, this work documents that BPA and EDHP adversely affect prepuberal spermatogenesis and perturb crucial epigenetic activities in male germ cells and highlight the protective ability of MLT.

Spermatogenesis-associated 48 is essential for spermatogenesis in mice.

Azoospermia, oligospermia and teratozoospermia all seriously impact male reproductive health. Spermatogenesis is a complex and precisely regulated process in which germ cells proliferate and differentiate and involves the regulation of multiple testis-specific genes. Here, we identified testis-specific gene spermatogenesis-associated 48 (SPATA48), the expression of which was age-dependent, indicating that it is involved in spermatogenesis. In humans and mice with azoospermia, expression of SPATA48 disappeared in the testis. Spata48-/- knockout male mice had smaller testis and defective spermatogenesis compared to wild-type (WT) mice. This study can help in the exploration of the genetic basis of male infertility and identify new targets for the diagnosis and treatment of male infertility.

SPAG17 Is Required for Male Germ Cell Differentiation and Fertility.

Spag17 encodes a protein present in the axoneme central pair complex of motile cilia and flagella. A mutation in this gene has been reported to be associated with infertility caused by defects in sperm motility. Here, we report that Spag17 knockout mice are infertile because of a severe defect in spermatogenesis. The histological evaluation of testis sections from mutant mice revealed seminiferous tubules with spermatogenesis arrested at the spermatid stage and cell debris in the cauda epididymis. The few sperm collected from the cauda epididymis were immotile and displayed abnormal tail and head morphology. Immunofluorescence analysis of Spag17 knockout germ cells showed spermatids with abnormally long manchette structures and morphological defects in the head. Electron microscopy showed altered manchette microtubules, reduced chromatin condensation, irregular nuclear shape, and detached acrosomes. Additionally, the transport of proteins (Pcdp1 and IFT20) along the manchette microtubules was disrupted in the knockout elongating spermatids. Our results show for the first time that Spag17 is essential for normal manchette structure, protein transport, and formation of the sperm head and flagellum, in addition to its role in sperm motility.

Impaired Spermatogenesis, Muscle, and Erythrocyte Function in U12 Intron Splicing-Defective Zrsr1 Mutant Mice

The U2AF35-like ZRSR1 has been implicated in therecognition of 3' splice site during spliceosome assembly, but ZRSR1 knockout mice do not showabnormal phenotypes. To analyze ZRSR1 function and its precise role in RNA splicing, we generatedZRSR1 mutant mice containing truncating mutations within its RNA-recognition motif.Homozygous mutant mice exhibited severe defects in erythrocytes, muscle stretch, and spermatogenesis, along with germ cell sloughing andapoptosis, ultimately leading to azoospermia and male sterility. Testis RNA sequencing (RNA-seq) analyses revealed increased intron retention of both U2- and U12-type introns, including U12-type intron events in genes with key functions inspermatogenesisand spermatid development. Affected U2 intronswere commonly found flankingU12 introns,suggesting functional cross-talkbetween the two spliceosomes. The splicing andtissue defects observed in mutant mice attributed to ZRSR1 loss of function suggest a physiologicalrole for this factor in U12 intron splicing.

Mutations in CFAP43 and CFAP44 cause male infertility and flagellum defects in Trypanosoma and human

Spermatogenesis defects concern millions of men worldwide, yet the vast majority remains undiagnosed. Here we report men with primary infertility due to multiple morphological abnormalities of the sperm flagella with severe disorganization of the sperm axoneme, a microtubule-based structure highly conserved throughout evolution. Whole-exome sequencing was performed on 78 patients allowing the identification of 22 men with bi-allelic mutations in DNAH1 (n = 6), CFAP43 (n = 10), and CFAP44 (n = 6). CRISPR/Cas9 created homozygous CFAP43/44 male mice that were infertile and presented severe flagellar defects confirming the human genetic results. Immunoelectron and stimulated-emission-depletion microscopy performed on CFAP43 and CFAP44 orthologs in Trypanosoma brucei evidenced that both proteins are located between the doublet microtubules 5 and 6 and the paraflagellar rod. Overall, we demonstrate that CFAP43 and CFAP44 have a similar structure with a unique axonemal localization and are necessary to produce functional flagella in species ranging from Trypanosoma to human.

Zebrafish androgen receptor is required for spermatogenesis and maintenance of ovarian function.

The androgen receptor (AR) is a nuclear receptor protein family member and inducible transcription factor that modulates androgen target gene expression. Studies using a mouse model confirmed the need for ar in reproductive development, particularly spermatogenesis. Here, we investigated the role of ar in zebrafish using CRISPR/Cas9 gene targeting technology. Targeted disruption of ar in zebrafish increases the number of female offspring and increases offspring weight. In addition, ar-null male zebrafish have female secondary sex characteristics. More importantly, targeted disruption of ar in zebrafish causes male infertility via defective spermatogenesis and female premature ovarian failure during growth. Mechanistic assays suggest that these effects are caused by fewer proliferated cells and more apoptotic cells in ar-null testes. Moreover, genes involved in reproductive development, estradiol induction and hormone synthesis were dys-regulated in testes and ovaries and the reproductive-endocrine axis was disordered. Our data thus suggest that the zebrafish ar is required for spermatogenesis and maintenance of ovarian function, which confirms evolutionarily conserved functions of ar in vertebrates, as well as indicates that ar-null zebrafish are a suitable model for studying pathologic mechanisms related to androgen disorders.

Hypogonadism in male thalassemia major patients: pathophysiology, diagnosis and treatment.

Failure of pubertal growth, delay or absence of sexual development, infertility and sexual dysfunction due to hypogonadism and defective spermatogenesis are frequent and well recognized disturbances among male patients with transfusion dependent (TD) thalassaemia major (β-thal). These problems are attributed mainly to the damage caused by chronic anaemia and the deposition of excess iron in the pituitary gland and testicles. This is a short review of male pubertal disorders in patients with β-thal written by pediatric endocrinologists and haematologists with an interest and active involvement, in the diagnosis and management of these complications in this group of patients. A vigilant clinical evaluation of growth and puberty, as well as an appropriate hormonal evaluation in poly-transfused (TD β-thal) patients is strongly recommended for early detection and treatment of endocrine dysfunction. Of crucial importance also, is the implementation of an efficient chelation regime from early life, to prevent severe iron load and permanent damage to the endocrine glands, particularly those responsible for gonadal function. (www.actabiomedica.it)

Development and implementation of a novel panel consisting 20 markers for the detection of genetic causes of male infertility.

Azoospermia factor (AZF) genes are involved in spermatogenesis. Deletions in the region of these genes have been recognised as a major genetic cause of infertility due to defects in spermatogenesis. Klinefelter syndrome (KS) is the other main cause of male infertility. This study was performed to establish a novel method for the detection of genetic causes of infertility in males and also to investigate the prevalence, extent and position of Y chromosome microdeletions in Iranian infertile men. We developed a newly designed panel of fluorescent multiplex-PCR method to amplify 20 markers (15 sequence-tagged sites (STSs) markers which are placed in the Y chromosome AZF region, 2 short tandem repeats (STRs) and 3 segmental duplications (SDs)). This multifunctional method is for the simultaneous detection of Y chromosome microdeletions and KS. Among 149 studied infertile men, one was detected to suffer from KS and seven (4.7%) were detected with the presence of one or more deleted STS loci. The main cause of infertility for the remaining patients would be nongenetic factors. This strategy is represented as a fast and accurate method to determine the frequencies of different AZF microdeletions which are suitable for use in clinical purposes.

A search for molecular mechanisms underlying male idiopathic infertility.

Infertility affects approximately 15% of the couples wanting to conceive. In 30 - 40% of the cases the aetiology of male infertility remains unknown and is called idiopathic male infertility. When assisted reproductive technologies are used to obtain pregnancy, an adequate (epi)genetic diagnosis of male infertility is of major importance to evaluate if a genetic abnormality will be transmitted to the offspring. In addition, there is need for better diagnostic seminal biomarkers to assess the success rates of these assisted reproductive technologies. This review investigated the possible causes and molecular mechanisms underlying male idiopathic infertility by extensive literature searches of: (i) causal gene mutations; (ii) proteome studies of spermatozoa from idiopathic infertile men;(iii) the role of epigenetics; (iv) post-translational modifications; and (v) sperm DNA fragmentation in infertile men. In conclusion, male infertility is a complex, multi-factorial disorder and the underlying causes often remain unknown. Further research on the (epi)genetic and molecular defects in spermatogenesis and sperm function is necessary to improve the diagnosis and to develop more personalized treatments of men with idiopathic infertility.