Genetic causes of spermatogenic failure

Variants in DPF3 and DSCAML1 are associated with sperm morphology

PURPOSE

Abnormalities in semen parameters are often associated with reduced fertility in males, and may, in part, be attributed to genetic variation. Aim of this study is to determine if genetic variants that were previously shown to be predictors of family size and birth rate in healthy men are also associated with sperm morphology in men recruited from an infertility laboratory.

METHODS

Genetic associations with sperm morphology phenotypes in 126 ethnically diverse men from Chicago at 41 independent loci, previously shown to be predictors of family size and birth rate in healthy men, were tested.

RESULTS

Two intronic SNPs, rs680730 (in DSCAML1) and rs10129954 (in DPF3), were associated with the percent of normal sperm morphology in Chicago men (P = 0.017 and 0.023, respectively). Furthermore, both loci were associated with increased occurrence of sperm head defects.

CONCLUSIONS

SNPs in two genes, both of which have roles in nervous system development, were associated with poor sperm morphology. These results may be helpful in identification of other novel genes and biological pathways whose proper functioning is crucial for sperm production and male reproductive processes.

Truncating mutations in TAF4B and ZMYND15 causing recessive azoospermia

BACKGROUND

Azoospermia is the absence of a measurable level of spermatozoa in the semen. It affects approximately 1% of all men, and the genetic basis of the majority of idiopathic cases is unknown. We investigated two unrelated consanguineous families with idiopathic azoospermia. In family 1, there were three azoospermic brothers and one oligozoospermic brother; and in family 2, there were three azoospermic brothers. Testis biopsy in the brothers in family 2 had led to the diagnosis of maturation arrest in the spermatid stage.

METHODS

Candidate disease loci were found via linkage mapping using data from single nucleotide polymorphism genome scans. Exome sequencing was applied to find the variants at the loci.

RESULTS

We identified two candidate loci in each family and homozygous truncating mutations p.R611X in TAF4B in family 1 and p.K507Sfs*3 in ZMYND15 in family 2. We did not detect any mutations in these genes in a cohort of 45 azoospermic and 15 oligozoospermic men. Expression studies for ZMYND15 showed that the highest expression was in the testis.

CONCLUSIONS

Both genes are known to have roles in spermatogenesis in mice but neither has been studied in humans. To our knowledge, they are the first genes identified for recessive idiopathic spermatogenic failure in men. Assuming that recessive genes for isolated azoospermia are as numerous in men as in mice, each gene is possibly responsible for only a small fraction of all cases.

Evolutionary conservation and expression of human RNA-binding proteins and their role in human genetic disease

RNA-binding proteins (RBPs) are effectors and regulators of posttranscriptional gene regulation (PTGR). RBPs regulate stability, maturation, and turnover of all RNAs, often binding thousands of targets at many sites. The importance of RBPs is underscored by their dysregulation or mutations causing a variety of developmental and neurological diseases. This chapter globally discusses human RBPs and provides a brief introduction to their identification and RNA targets. We review RBPs based on common structural RNA-binding domains, study their evolutionary conservation and expression, and summarize disease associations of different RBP classes.

SNPs in KIT and KITLG genes may be associated with oligospermia in Chinese population

KIT/KITLG signaling system is crucial for spermatogenesis, which suggests that KIT and KITLG genes may be involved in spermatogenesis impairment and male infertility. To explore the possible association of KIT and KITLG genes with male infertility having spermatogenesis impairment, polymorphism distributions of SNP rs3819392 in KIT gene as well as rs995030 and rs4474514 in KITLG gene were investigated in 372 patients with idiopathic azoospermia or oligospermia and 205 fertile controls. As a result, the significant differences in polymorphism distributions of SNP rs3819392 in KIT gene and rs4474514 in KITLG gene were observed between the patients with oligospermia and controls. The frequencies of allele G (94.2% versus 90.0% p = 0.022) and genotype GG (89.2% versus 82.0% p = 0.042) in patients with oligospermia were significantly higher than those in controls at rs3819392 locus in KIT gene. In addition, the genotype CC of rs4474514 in KITLG (8.2% versus 3.4%, p = 0.034) also significantly increased in oligospermic patients in comparison to controls. These findings indicated that SNP rs3819392 in KIT gene and rs4474514 in KITLG gene may be associated with oligospermia, suggesting that polymorphism of KIT and KITLG genes may play a role in oligospermia.

Azoospermia due to spermatogenic failure

This article summarizes the current literature regarding azoospermia caused by spermatogenic failure. The causes and genetic contributions to spermatogenic failure are reviewed. Medical therapies including use of hormonal manipulation, whether guided by a specific abnormality or empiric, to induce spermatogenesis are discussed. The role of surgical therapy, including a discussion of varicocelectomy in men with spermatogenic failure, as well as an in-depth review of surgical sperm retrieval with testicular sperm extraction and microdissection testicular sperm extraction, is provided. Finally, future directions of treatment for men with spermatogenic failure are discussed, namely, stem cell and gene therapy.

Association of progesterone receptor gene polymorphism with male infertility and clinical outcome of ICSI

PURPOSE

To investigate the association of Progesterone Receptor (PR) gene variations and male infertility

METHODS

DNA extraction, PCR and sequencing of PR gene, PROGINS insertion by PCR. Association of the variations with seminal parameters and outcomes of ICSI.

RESULTS

Four known SNPs in the PR gene were identified in the study of which three (rs3740753, rs1042838, rs104283) were co-inherited and in complete linkage disequilibrium with the PROGINS Alu insertion. There were no differences in their frequencies between fertile and infertile males. The rs2020880 was found at a very low frequency only in the controls but not in the infertile subjects. The sperm counts, fertilization rate, embryo quality or pregnancy rates were not different in individuals with or without PROGINS allele.

CONCLUSION

PR gene alterations are not associated with male infertility or ICSI outcome.

Co-culture of Mouse Embryonic Stem Cells with Sertoli Cells Promote in vitro Generation of Germ Cells

OBJECTIVE(S)

Sertoli cells support in vivo germ cell production; but, its exact mechanism has not been well understood. The present study was designed to analyze the effect of Sertoli cells in differentiation of mouse embryonic stem cells (mESCs) to germ cells.

MATERIALS AND METHODS

A fusion construct composed of a Stra8 gene promoter and the coding region of enhanced green fluorescence protein was produced to select differentiated mESCs. To analyze sertoli cells' effect in differentiation process, mESCs were separated into two groups: the first group was cultured on gelatin with retinoic acid treatment and the second group was co-cultured with sertoli cell feeder without retinoic acid induction. Expressions of pre-meiotic (Stra8), meiotic (Dazl and Sycp3) and post-meiotic (Prm1) genes were evaluated at different differentiation stages (+7, +12 and +18 days of culture).

RESULTS

In the first group, expressions of meiotic and post-meiotic genes started 12 and 18 days after induction with retinoic acid, respectively. In the second group, 7 days after co-culturing with Sertoli cells, expression of meiotic and post-meiotic genes was observed.

CONCLUSION

These results show that differentiation process to germ cells is supported by Sertoli cells. Our findings provide a novel effective approach for generation of germ cell in vitro and studying the interaction of germ cells with their niche.

Association between Y-chromosome AZFc region micro-deletions with recurrent miscarriage

BACKGROUND

In human, about 25% of implanted embryos are losing 1-2 week following attachment to the uterus. A subset of this population will have three or more consecutive miscarriages which define as repeated pregnancy loss (RPL). Introducing the assisted reproductive technologies (ARTS) made a chance for infertile couples to solve their childless problem.

OBJECTIVE

This study was conducted to evaluate the incidence of Y-chromosome AZF region's micro-deletions in male partners of couples with recurrent miscarriage (RM).

MATERIALS AND METHODS

Thirty male partner of couples with RM and thirty infertile males, who referred to the Yazd Research and Clinical Center for Infertility were recruited to this study. In addition, 30 healthy men were screened as a control group from the same center. After DNA extraction using salting out method, the multiplex-PCR was done for amplifying 8 known STSs proximal to the AZF region of the Y-chromosome. The results were compared between the groups using Fisher's exact t-test and p<0.05 was considered statistically significant.

RESULTS

Of the 30 infertile males, 5 (16.6%) cases were associated with the AZF region micro-deletions of DYF87S, DYF84S1, DYF83S1 and DYF51S1, STSs. But in the fertile and RM male groups was found no deletions similar to those, of the infertile males (p=1.0). Instead 4 (13.3%) cases of the RM group males had different micro-deletions included DYS220 (AZFb, sY129), DYS262, DYF8551, and DYF8651, STSs. The AZFc locus of Y-chromosome micro-deletions have a significant role in RM (p=0.045).

CONCLUSION

It seems that the Y-chromosome AZF region's micro-deletions are associated with RM, and we recommend adding this AZF region STSs into infertility analyzing panels.

Approach to the patient with oligozoospermia

Male infertility affects 1 in 20 men and is the sole or contributory factor in half of assisted reproductive treatments (ARTs). A reduced sperm density (oligozoospermia) is often accompanied by poor motility and morphology reflecting qualitative and quantitative defects in spermatogenesis. Many reproductive and nonreproductive disorders and treatments may be responsible, but most cases remain unexplained (idiopathic). A thorough evaluation may identify treatable causes and allow natural fertility. Comorbidities more prevalent in infertile men, especially androgen deficiency and testicular cancer, should be sought. Idiopathic spermatogenic disorders are common, but evidence-based treatment is not available; full evaluation informs management and the decision to pursue ART using the low numbers of functional sperm available. Chromosomal anomalies may impact the chance of a normal healthy pregnancy, and new genetic causes of oligozoospermia are being discovered. ART, particularly intracytoplasmic sperm injection, bypasses instead of treats the sperm defect but has dramatically improved the fertility prospects. The clinical approach to the oligozoospermic man involves understanding reproductive endocrinology, aspects of urology and clinical genetics, modern ART options, and the realistic discussion of their outcomes, alternatives such as adoption or donor gametes, and appreciation of the psychosocial concerns of the couple.

Y chromosome microdeletions in infertile men: prevalence, phenotypes and screening markers for the Indian population

PURPOSE

Yq microdeletions are the leading genetic cause of male infertility and its detection is clinically relevant for appropriate genetic counseling. We aimed to determine the prevalence and type of Yq microdeletions, the associated seminal phenotypes and the STS markers that are relevant for its testing in Indian population.

METHODS

Yq microdeletion analysis was carried out in 1,636 infertile cases in our centers. Additional data was collected from published studies in Indian population leading to a total of 3,647 cases.

RESULTS

In our cohort, 3.4 % (56/1,636) of infertile men had Yq microdeletions. Combining the data from other published studies identified 215/3,647 (5.8 %) infertile individuals to harbor Yq microdeletions; with 6.4 % in azoopsermia, 5.8 % in oligozoospermia and 3.2 % in oligoasthenozoospermia and teratozoospermia cases. No significant differences in the deletion frequencies were observed between idiopathic vs non idiopathic cases (5.8 vs 8.6 % respectively). Deletions of AZFc were at highest frequency (46.6 %) with double deletions most commonly observed in azoospermic subjects. With respect to the STS markers, screening with the six European Academy of Andrology (EAA) markers would miss 3.1 % of cases; additional non EAA markers that would contribute significantly to screening are sY746, sY82, sY121, sY128, sY130, sY143, sY145 & sY160.

INTERPRETATIONS AND CONCLUSIONS

The frequency of Yq microdeletions is lower in Indian population as compared to Western counterparts. There is no major association of Yq microdeletions with seminal parameters or cause of infertility. Clinically it will be necessary to offer Yq microdeletion testing to all the classes of infertile men. The EAA markers may not be adequate to detect microdeletions in Indian infertile men.

Null genotype of GSTM1 and GSTT1 may contribute to susceptibility to male infertility with impaired spermatogenesis in Chinese population

Glutathione-S-transferases (GSTs) play a protective role during spermatogenesis and GST genes may be involved in impaired spermatogenesis. A case-control study was performed to explore the association of genes GSTM1 and GSTT1, two members of GST gene family, with spermatogenesis impairment. The deletion polymorphism distribution of genes GSTM1 and GSTT1 was investigated in 353 patients with azoospermia or oligospermia and 201 fertile controls in Chinese population using multiplex PCR. As a result, the frequencies of null genotype of genes GSTM1 (67.4% versus 57.7%, p = 0.022, OR = 1.516, 95% CI = 1.001-2.168) and GSTT1 (61.8% versus 46.8%, p = 0.001, OR = 1.838, 95% CI = 1.295-2.610) in patients were significantly higher than those in controls. After stratifying patients, the frequencies of null genotype of gene GSTM1 in oligospermia (68.3% versus 57.7%, p = 0.027, OR = 1.580, 95% CI = 1.051-2.375) and GSTT1 in azoospermia (66.9% versus 46.8%, p < 0.001, OR = 2.299, 95% CI = 1.484-3.562) as well as oligospermia (57.9% versus 46.8%, p = 0.025, OR = 1.567, 95% CI = 1.057-2.322) were still significantly higher compared with controls. The results suggested that null genotypes of GSTM1 and GSTT1 are associated with spermatogenesis impairment and may contribute to susceptibility to spermatogenesis impairment and male infertility in Chinese population.

Clinical characteristics and reproductive outcomes in infertile men with testicular early and late maturation arrest

OBJECTIVE

To compare the clinical characteristics and reproductive outcomes of nonobstructive azoospermic men with uniform early and late maturation arrest.

METHODS

Patients with biopsy-documented uniform maturation arrest undergoing testicular sperm retrieval and complete medical records were enrolled in the present study. Their medical history, physical examination findings, testicular volume, serum hormone parameters, genetic anomalies, sperm retrieval, and reproductive outcomes were retrospectively analyzed.

RESULTS

In a cohort of 223 nonobstructive azoospermic men, 34 men with uniform maturation arrest (21 early maturation arrest and 13 late maturation arrest) were identified. No significant differences were seen in the age distribution, testicular volume, or hormone parameters between patients with early and late maturation arrest. Only 13 patients (38.2%) had a normal serum follicle-stimulating hormone level and normal testicular volume. Patients with early maturation arrest had a greater frequency of overall genetic anomalies, and patients with late maturation arrest had a greater frequency of previous testicular insults. The sperm retrieval and impregnation rate were nonsignificantly greater in patients with late maturation arrest.

CONCLUSION

Maturation arrest has a variety of causes and presents with diverse phenotypes. Not all patients with uniform maturation arrest have a normal follicle-stimulating hormone level or testicular volume. Patients with early maturation arrest have a greater incidence of genetic anomalies and are more likely to have worse reproductive outcomes than are patients with late maturation arrest.

Global human tissue profiling and protein network analysis reveals distinct levels of transcriptional germline-specificity and identifies target genes for male infertility

BACKGROUND

Mammalian spermatogenesis is a process that involves a complex expression program in both somatic and germ cells present in the male gonad. A number of studies have attempted to define the transcriptome of male meiosis and gametogenesis in rodents and primates. Few human transcripts, however, have been associated with testicular somatic cells and germ cells at different post-natal developmental stages and little is known about their level of germline-specificity compared with non-testicular tissues.

METHODS

We quantified human transcripts using GeneChips and a total of 47 biopsies from prepubertal children diagnosed with undescended testis, infertile adult patients whose spermatogenesis is arrested at consecutive stages and fertile control individuals. These results were integrated with data from enriched normal germ cells, non-testicular expression data, phenotype information, predicted regulatory DNA-binding motifs and interactome data.

RESULTS

Among 3580 genes for which we found differential transcript concentrations in somatic and germ cells present in human testis, 933 were undetectable in 45 embryonic and adult non-testicular tissues, including many that were corroborated at protein level by published gene annotation data and histological high-throughput protein immunodetection assays. Using motif enrichment analyses, we identified regulatory promoter elements likely involved in germline development. Finally, we constructed a regulatory disease network for human fertility by integrating expression signals, interactome information, phenotypes and functional annotation data.

CONCLUSIONS

Our results provide broad insight into the post-natal human testicular transcriptome at the level of cell populations and in a global somatic tissular context. Furthermore, they yield clues for genetic causes of male infertility and will facilitate the identification of novel cancer/testis genes as targets for cancer immunotherapies.