Susceptibility gene for non-obstructive azoospermia located near HLA-DR and -DQ loci in the HLA class II region

Immune and spermatogenesis-related loci are involved in the development of extreme patterns of male infertility

We conducted a genome-wide association study in a large population of infertile men due to unexplained spermatogenic failure (SPGF). More than seven million genetic variants were analysed in 1,274 SPGF cases and 1,951 unaffected controls from two independent European cohorts. Two genomic regions were associated with the most severe histological pattern of SPGF, defined by Sertoli cell-only (SCO) phenotype, namely the MHC class II gene HLA-DRB1 (rs1136759, P = 1.32E-08, OR = 1.80) and an upstream locus of VRK1 (rs115054029, P = 4.24E-08, OR = 3.14), which encodes a protein kinase involved in the regulation of spermatogenesis. The SCO-associated rs1136759 allele (G) determines a serine in the position 13 of the HLA-DRβ1 molecule located in the antigen-binding pocket. Overall, our data support the notion of unexplained SPGF as a complex trait influenced by common variation in the genome, with the SCO phenotype likely representing an immune-mediated condition.

A GWAS in a large case-control cohort of European ancestry identifies two genomic regions, the MHC class II gene HLA-DRB1 and an upstream locus of VRK1, that are associated with the most severe phenotype of spermatogenic failure.

Pervasiveness of intronless genes expressed in haploid germ cell differentiation

BACKGROUND

cDNA libraries derived from the brain and testis contain genes that encode almost all proteins. The brain is composed of various differentiated cells, and the testis also contains various differentiated cells, such as germ cells, and somatic cells that support germ cell differentiation, such as Sertoli and Leydig cells. Many genes appear to be expressed due to tissue complexity.

METHODS

The Genome Project has sequenced the entire genomes of humans and mice. Recent research using new gene analysis technologies has found that many genes are expressed specifically in male germ cells.

MAIN FINDINGS RESULTS

Functional intronless genes are significantly enriched in haploid germ cell-specific genes.

CONCLUSION

Functional intronless genes associated with fertility are more likely to be inherited in haploid germ cells than in somatic cells.

Evaluation of association between methylenetetrahydrofolate reductase and azoospermia: A meta-analysis

BACKGROUND

Infertility affects childbearing age couples all over the world. One of the important reasons for infertility is genetic factors. Our study evaluated the association between methylenetetrahydrofolate reductase (MTHFR) and azoospermia.

METHODS

Multiple databases like MEDLINE, EMBASE, Cochrane library, and China journal full-text database were used to search for relevant studies, and full-text articles involved in the evaluation of MTHFR and azoospermia. The results were evaluated using STATA 12.0. Heterogeneity analysis, sensitivity analysis, and bias analysis were also performed on the data.

RESULTS

Thirteen related studies eventually met the inclusion criteria. Significant association between C677T polymorphism and azoospermia (relative risk [RR] = 0.94 [0.90, 0.99], I2 = 60.9%, P = .002), and between A1298C polymorphism and azoospermia (RR = 0.98 [0.94, 1.02], I2 = 56.3%, P = .011) was observed. Meanwhile, in subgroup analysis, Caucasians had higher risk than Mongolians in association between MTHFR and azoospermia.

CONCLUSION

There was association between MTHFR polymorphism and azoospermia. Caucasian populations had higher risk than Mongolian populations in association between MTHFR and azoospermia.

De novo mutations in idiopathic male infertility-A pilot study

STUDY QUESTION

Are de novo mutations in the human genome associated with male infertility?

SUMMARY ANSWER

We identified de novo mutations in five candidate genes: SEMA5A, NEURL4, BRD2, CD1D, and CD63.

WHAT IS KNOWN ALREADY

Epidemiological and genetic studies have consistently indicated contribution of genetic factors to the etiology of male infertility, suggesting that more than 1500 genes are involved in spermatogenesis.

STUDY DESIGN, SIZE, DURATION

First, we searched for de novo mutations in patients with idiopathic azoospermia with whole-exome sequencing (WES). To evaluate the potential functional impact of de novo identified mutations, we analyzed their expression differences on independent testis samples with normal and impaired spermatogenesis. In the next step, we tested additional group of azoospermic patients for mutations in identified genes with de novo mutations. In addition to the analysis of de novo mutations in patients with idiopathic azoospermia, we considered other models of inheritance and searched for candidate genes harboring rare maternally inherited variants and biallelic autosomal and X-chromosome hemizygous variants.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We performed WES in 13 infertile males with idiopathic azoospermia and their parents. Potential functional impact of de novo identified mutations was evaluated by global gene expression profiling on 20 independent testis samples. To replicate the results, we performed WES in further 16 independent azoospermic males, which were screened for the variants in the same genes. Library preparation was performed with Nextera Coding Exome Capture Kit (Illumina), with subsequent sequencing on Illumina HiSeq 2500 platform.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified 11 de novo mutations in 10 genes of which 5 were considered potentially associated with azoospermia: SEMA5A, NEURL4, BRD2, CD1D, and CD63. All candidate genes showed significant differential expression in testis samples composed of patients with severely impaired and normal spermatogenesis. Additionally, we identified rare, potentially pathogenic mutations in the genes previously implicated in male infertility-a maternally inherited heterozygous frameshift variant in FKBPL gene and inframe deletion in UPF2 gene, homozygous frameshift variant in CLCA4 gene, and a heterozygous missense variant NR0B1 gene, which represent promising candidates for further clinical implication.

LIMITATIONS OF THE STUDY, REASONS FOR CAUTION

We provided limited functional support for involvement of de novo identified genes in pathogenesis of male infertility, based on expression analysis. Additionally, the sample size was limited.

WIDER IMPLICATIONS OF THE FINDINGS

We provide support that de novo mutations might contribute to male infertility and propose five genes as potentially implicated in its pathogenesis.

Fine mapping the MHC region identified rs4997052 as a new variant associated with nonobstructive azoospermia in Han Chinese males

OBJECTIVE

To investigate the association between genetic variants in the major histocompatibility complex (MHC) region and nonobstructive azoospermia (NOA) susceptibility.

DESIGN

MHC region fine-mapping analysis based on previous NOA genome-wide association study (GWAS) data.

SETTING

Medical university.

PATIENT(S)

Nine hundred and eighty-one men with NOA and 1,657 normal fertile male controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The MHC region imputation assessed with SNP2HLA software, taking the specific Han-MHC database as a reference panel; statistical significance of the MHC variants calculated using logistic regression models; functional annotation based on online public databases; and phenotypic variances explained by specific groups of genetic variants estimated using the fixed effects model from individual associations.

RESULT(S)

Two independent risk loci, rs7194 (odds ratio [OR] 1.37) at MHC class II molecules and rs4997052 (OR 1.30) at MHC class I molecules, were identified. Functional annotation showed rs7194 may tag the effect of multiple amino acid residues and the expression of HLA-DQB1 and HLA-DRB1; while rs4997052 showed the effect of amino acid changes of HLA-B at position 116 as well as the expression of HLA-B and CCHCR1, which coexpressed with genes enriched in pathways of spermatogenesis and male gamete generation. The novel variant rs4997052 identified in our study can explain another approximately 0.66% of the phenotypic variances of NOA.

CONCLUSION(S)

We fine-mapped the MHC region and identified two loci that independently drove NOA susceptibility. These results provide a deeper understanding of the association mechanisms of MHC and NOA risk.

Associations of human leucocyte antigen class II-DQB1 alleles with hepatitis C virus infection in Egyptian population: a multicentre family-based study

Hepatitis C infection is a global pandemic. HLA-DQB1 alleles are believed to have an effective role in immune response against HCV including susceptibility to or protection from this infection. The aim of this study was to investigate the contribution of HLA-DQB1 alleles in the outcome of HCV genotype-4 infection through a family-based association study. Egyptian families with HCV (324) were recruited for this study (324 index positive for RNA-HCV, 225 positive relatives representing chronic hepatitis C cases and 582 family members negative for HCV-RNA [control], 63 of whom spontaneously cleared the virus. All subjects were genotyped for HLA-DQB1 alleles by sequence-specific primers (SSP-PCR) and sequence-based typing (SBT) methods. The frequency of DQB1*02:01:01 carriage was significantly higher in infected patients when compared to controls and those who spontaneously cleared virus (OR=5.47, P<.0001 and OR= 6.5234, P<.0001, respectively), and the carriage of the DQB1*03:01:01:01 allele was significantly higher in those who cleared and controls when compared to the infected patients (OR=0.2889, P<.0001 and OR=0.3016, P<.0001, respectively). On the other hand, the frequency of DQB1*06:01:01 and QB1*05:01:01:01 alleles was not associated with infection (comparison of infected and cleared patients showed OR of 2.1598 [P<.01]), but it becomes nonsignificant after adjustments with the Bonferroni formula (P_C >0.05) and OR= 1.3523, P>.05, respectively. This study shows that clearance of HCV is associated with DQB1*03:01:01:01 allele and chronicity of HCV infection associated with the risk allele: DQB1*02:01:01.

Association and meta-analysis of HLA and non-obstructive azoospermia in the Han Chinese population

The exact aetiology and pathogenesis of most non-obstructive azoospermia (NOA) are still unknown. The previous two genomewide association studies (GWASs) have identified three different loci within the HLA region for NOA in the Han Chinese population, including rs3129878, rs498422 and rs7194. To further validate the risk of three GWAS-linked loci for NOA, we conducted a case-control study of these three risk loci in an independent Han Chinese male population, with 603 NOA patients and 610 controls. Furthermore, we also performed a meta-analysis of five studies on these three NOA-risk loci. The case-control study strongly suggested a significant association between loci rs3129878, rs498422 and rs7194 and NOA (P = 6.75 × 10^-21 (OR = 2.2586), P = 0.0060 (OR = 1.4013) and P = 0.0128 (OR = 1.2626) respectively). Our meta-analyses also supported the susceptibility of these three risk loci to NOA (P < 0.01). The risk variants within the HLA region potentially have a strong effect on males at risk of NOA, and may serve as diagnostic markers for male infertility. However, considering genetic difference between different populations, future validating studies in larger independent samples and animal experiments are suggested.

Genetics of male infertility: from research to clinic

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

Association of polymorphisms of A260G and A386G in DAZL gene with male infertility: a meta-analysis and systemic review

To investigate the association of single nucleotide polymorphism 260 and 386 (SNP260 and SNP386) gene with male infertility, an electronic search was performed to identify case-control studies evaluating the relationship of SNP260 or SNP386 of deleted in azoospermia-like (DAZL) and male infertility. Review Manager 5 was used to process the meta-analysis and other statistical analysis. A total of 139 records were retrieved, of which 13 case-control studies with total 2715 patients and 1835 normozoospermic men were included. SNP260 was found not to play a functional role in male oligo/azoospermia either for Caucasians or for Asians. But for SNP386, models of allele (A/G), dominant (AA/AG + GG), co-dominant (AA/AG) and super-dominant (AA + GG/AG) had a strong correlation to spermatogenic failure with related odds ratio being 0.15 (95% confidence interval [95% CI] 0.07 to 0.34, P < 0.00001), 0.16 (95% CI 0.07 to 0.35, P < 0.00001), 0.15 (95% CI 0.06 to 0.33, P < 0.00001) and 0.15 (95% CI 0.06 to 0.33, P < 0.00001), respectively. Moreover, this correlation was only found in the Chinese Han population (decreasing around 85% risk of oligo/azoospermia infertility) and not found in India, Japan, and Caucasian countries. Our analysis demonstrated that SNP260 of DAZL did not contribute to oligo/azoospermia while SNP386 was correlated to male infertility. However, this correlation was only found in China with a country-specific and ethnicity-specific manner.

Contribution of susceptibility locus at HLA class I region and environmental factors to occurrence of nasopharyngeal cancer in Northeast India

High incidence of nasopharyngeal carcinoma (NPC) has been reported from China, Southeast Asia and Northeast (NE) region of India. Populations at geographic regions having higher incidence of NPC display human leukocyte antigen (HLA) distribution patterns different from areas having low incidence. The current study has investigated the contribution of environmental risk factors and ethnic variation of microsatellite markers in HLA region for the high incidence of NPC in NE India. Genotyping of HLA region using 33 microsatellite markers by fragment length analysis was done in 220 study subjects (120 NPC patients and 100 healthy controls). Association analysis showed two adjacent microsatellite markers HL003 (allele 121) and D6S2704 (allele 218) in the HLA class I region having association with high risk of NPC while allele 127 of HL003 and allele 255 of D6S2678 conferred a protective effect. The environmental factors mainly use of firewood (odds ratio (OR) = 3.797385, confidence interval (CI) = 1.97-7.30, P < 0), living in mud house (OR = 3.46, CI = 1.19-10.08, P = 0.022) and consumption of alcohol (OR = 2.11, CI = 1.02-4.37, P = 0.043) were found as major risk factors for NPC. Higher-order interaction showed combination of smoked food consumption and firewood use for cooking in multifactor dimensionality reduction (MDR) analysis and interaction of non-firewood users, non-ventilated houses and residence in mud houses in classification and regression tree (CART) analysis as the significant risk factors for NPC. Expression of Epstein-Barr virus (EBV) RNA was found in 92% (23/25) of NPC cases suggesting its significant role in NPC aetiopathogenesis. This study identified association of NPC with a susceptibility locus in the HLA class I region which has complex interaction with viral DNA and environmental factors.

Array-based DNA methylation profiling in male infertility reveals allele-specific DNA methylation in PIWIL1 and PIWIL2

OBJECTIVE

To identify CpG sites differentially methylated in peripheral blood of men with idiopathic infertility due to impaired spermatogenesis as compared with fertile controls.

DESIGN

DNA methylation profiling on peripheral blood samples using the HumanMethylation450 BeadChip (Illumina) in patients and controls, single-nucleotide polymorphism (SNP) typing by Sanger sequencing.

SETTING

University institute in cooperation with genetic and infertility clinics.

PATIENT(S)

30 infertile men with normal CFTR and AZF tests and karyotype, and 10 fertile male controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

DNA methylation levels at CpG sites.

RESULT(S)

We identified 471 CpGs (287 genes) as differentially methylated between patients and controls. These were significantly enriched for the gene ontology functions MHC class II receptor activity and piwi-interacting (piRNA) binding. The latter was associated with two methylation-sensitive SNPs in the genes PIWIL1 and PIWIL2, respectively, which showed significant allele distribution skewing in the infertile cohort. We found that 445 (94.5%) of 471 differentially methylated CpGs were associated with SNPs, but 26 (15 genes) were not genomically templated, including the ENO1, MTA2, BRSK2, and LBX2 genes previously associated with fertility and spermatogenesis.

CONCLUSION(S)

Our study identifies surrogate DNA methylation markers for idiopathic infertility in peripheral blood and suggests that allele-specific DNA methylation differences at regulatory sites of genes involved in piRNA regulation are associated with disturbed spermatogenesis.

Association study of HLA-B alleles with idiopathic male infertility in Han population of China

PURPOSE

To investigate the distributions of HLA-B alleles and estimate their associations with idiopathic male infertility in Chinese Han population.

METHODS

Polymerase chain reaction-sequence-based typing (PCR-SBT) method was used for DNA typing at HLA-B locus in 109 patients with idiopathic male infertility and 152 healthy controls in male Han population of Shaanxi Province, situated in northwestern China.

RESULTS

In total, we detected 45 HLA-B alleles in idiopathic infertile patients, 48 HLA-B alleles in control subjects. However, no significant differences of these allelic frequencies were found between the infertile patients and the controls.

CONCLUSION

HLA-B gene was unlikely a major risk factor of idiopathic male infertility in this sample population. As different populations have different HLA polymorphisms, investigation of the relationship of other HLA genes and idiopathic male infertility with larger sample size, is warranted in the future.

The emerging role of FK506-binding proteins as cancer biomarkers: a focus on FKBPL

FKBPs (FK506-binding proteins) have long been recognized as key regulators of the response to immunosuppressant drugs and as co-chaperones of steroid receptor complexes. More recently, evidence has emerged suggesting that this diverse protein family may also represent cancer biomarkers owing to their roles in cancer progression and response to treatment. FKBPL (FKBP-like) is a novel FKBP with roles in GR (glucocorticoid receptor), AR (androgen receptor) and ER (oestrogen receptor) signalling. FKBPL binds Hsp90 (heat-shock protein 90) and modulates translocation, transcriptional activation and phosphorylation of these steroid receptors. It has been proposed as a novel prognostic and predictive biomarker, where high levels predict for increased recurrence-free survival in breast cancer patients and enhanced sensitivity to endocrine therapy. Since this protein family has roles in a plethora of signalling pathways, its members represent novel prognostic markers and therapeutic targets for cancer diagnosis and treatment.

Alterations in the steroid hormone receptor co-chaperone FKBPL are associated with male infertility: a case-control study

BACKGROUND

Male infertility is a common cause of reproductive failure in humans. In mice, targeted deletions of the genes coding for FKBP6 or FKBP52, members of the FK506 binding protein family, can result in male infertility. In the case of FKBP52, this reflects an important role in potentiating Androgen Receptor (AR) signalling in the prostate and accessory glands, but not the testis. In infertile men, no mutations of FKBP52 or FKBP6 have been found so far, but the gene for FKBP-like (FKBPL) maps to chromosome 6p21.3, an area linked to azoospermia in a group of Japanese patients.

METHODS

To determine whether mutations in FKBPL could contribute to the azoospermic phenotype, we examined expression in mouse and human tissues by RNA array blot, RT-PCR and immunohistochemistry and sequenced the complete gene from two azoospermic patient cohorts and matching control groups. FKBPL-AR interaction was assayed using reporter constructs in vitro.

RESULTS

FKBPL is strongly expressed in mouse testis, with expression upregulated at puberty. The protein is expressed in human testis in a pattern similar to FKBP52 and also enhanced AR transcriptional activity in reporter assays. We examined sixty patients from the Japanese patient group and found one inactivating mutation and one coding change, as well as a number of non-coding changes, all absent in fifty-six controls. A second, Irish patient cohort of thirty showed another two coding changes not present in thirty proven fertile controls.

CONCLUSIONS

Our results describe the first alterations in the gene for FKBPL in azoospermic patients and indicate a potential role in AR-mediated signalling in the testis.

Butyrophilin-like 2 gene is associated with ulcerative colitis in the Japanese under strong linkage disequilibrium with HLA-DRB1*1502

The human leukocyte antigen (HLA) region has been implicated in the pathogenesis of inflammatory bowel disease (IBD), which is classified into Crohn's disease (CD) and ulcerative colitis (UC). Recently, an association between sarcoidosis and the butyrophilin-like 2 (BTNL2) gene was reported. BTNL2 is located in the HLA region and its messenger RNA is expressed most abundantly in the intestine. In this study, we performed a case-control association study of BTNL2 in the Japanese patients with IBD and performed linkage disequilibrium (LD) analysis between BTNL2 and HLA-DRB1. We analyzed eight polymorphisms selected after direct sequencing and found that none of the polymorphisms were associated with the Japanese CD cohort. In contrast, five polymorphisms were significantly associated with UC, especially three single nucleotide polymorphisms (BTNL2_19, BTNL2_22 and BTNL2_23) were associated as a haplotype. The most frequent haplotype (GGC haplotype) was a low-risk haplotype (P= 0.000052), whereas the other TCT haplotype was a high-risk haplotype (P= 0.0000085). Among the eight polymorphisms, the strongest association with UC was found in BTNL2_19 (OR = 1.92, P= 0.0000035). As expected, the BTNL2_19-T allele showed strong LD with DRB1*1502 (D'= 0.92). When BTNL2_19 was tested as conditional on the DRB1*1502 carrier status, the significant association disappeared, suggesting that the association was because of its strong LD with DRB1*1502. We conclude that BTNL2 does not contribute to the susceptibility to Japanese CD but is associated with Japanese UC because of the strong LD with HLA-DRB1*1502. The strong LD between BTNL2 and HLA-DRB1 raises another issue about the potential role of BTNL2 in other diseases associated with HLA-DRB1.

Associations of homologous RNA-binding motif gene on the X chromosome (RBMX) and its like sequence on chromosome 9 (RBMXL9) with non-obstructive azoospermia

AIM

To investigate the associations of autosomal and X-chromosome homologs of the RNA-binding-motif (RNA-binding-motif on the Y chromosome, RBMY) gene with non-obstructive azoospermia (NOA), as genetic factors for NOA may map to chromosomes other than the Y chromosome.

METHODS

Genomic DNA was extracted using a salting-out procedure after treatment of peripheral blood leukocytes with proteinase K from Japanese patients with NOA (n=67) and normal fertile volunteers (n=105). The DNA were analyzed for RBMX by expressed sequence tag (EST) deletion and for the like sequence on chromosome 9 (RBMXL9) by microsatellite polymorphism.

RESULTS

We examined six ESTs in and around RBMX and found a deletion of SHGC31764 in one patient with NOA and a deletion of DXS7491 in one other patient with NOA. No deletions were detected in control subjects. The association study with nine microsatellite markers near RBMXL9 revealed that D9S319 was less prevalent in patients than in control subjects, whereas D9S1853 was detected more frequently in patients than that in control subjects.

CONCLUSION

We provide evidence that deletions in or around RBMX may be involved in NOA. In addition, analyses of markers in the vicinity of RBMXL9 on chromosome 9 suggest the possibility that variants of this gene may be associated with NOA. Although further studies are necessary, this is the first report of the association between RBMX and RBMXL9 with NOA.

Multilocus analyses of estrogen-related genes reveal involvement of the ESR1 gene in male infertility and the polygenic nature of the pathology

OBJECTIVE

To examine whether polymorphisms within the ESR1, FSHR, ESR2, CYP19A1, and NRIP1 genes are susceptibility factors for human male idiopathic infertility and to test the joint effects of these genes on male reproductive function.

DESIGN

Genetic association study of male infertility with polymorphisms, using both single-gene and multilocus approaches.

SETTING

Private and public fertility units and a private center for biomedical research.

PATIENT(S)

One hundred four Spanish men with azoospermia or severe oligozoospermia and 95 unselected race-matched healthy controls from the same geographic region.

INTERVENTION(S)

Peripheral blood extraction, DNA purification, and ESR1 g.938T>C, FSHR Ser680Asn, ESR2 *39A>G, CYP19A1 *19C>T, and NRIP1 Gly75Gly polymorphism analyses.

MAIN OUTCOME MEASURE(S)

Single-gene statistical analyses and multilocus statistical analyses with Sumstat, Permutation and Model-free analysis, and Estimating Haplotypes software.

RESULT(S)

We observed an excess of homozygous infertile men for the ESR1 g.938T>C marker. Multilocus analyses detected genetic interaction between the five candidate gene markers that are influential over male infertility. In addition, we detected a five-loci protector genetic pattern with a frequency of 9.4% in controls but absent in infertile men.

CONCLUSION(S)

Our results support a relevant role for the estrogenic pathway, notably the ESR1 gene, in human male reproductive function and advocate a complex trait model for male infertility.

DAZL polymorphisms and susceptibility to spermatogenic failure: an example of remarkable ethnic differences

Polymorphisms in genes involved in spermatogenesis are considered potential risk factors for male infertility. Recently a polymorphism in the deleted in azoospermia-like (DAZL) gene (T54A) was reported as susceptibility factor to oligo/azoospermia in the Chinese population. DAZL is an autosomal homologue of the Y chromosomal DAZ (deleted in azoospermia) gene cluster and both are considered master regulators of spermatogenesis. The aim of the present study was to screen (i) for mutations of the entire coding sequence of the DAZL gene in patients lacking of the DAZ gene cluster, in order to evaluate if DAZL polymorphisms may influence the AZFc deletion phenotype; (ii) for the two previously described (and eventually newly identified) single nucleotide polymorphisms (SNPs) in a large group of infertile and normospermic men of Italian origin. We failed to detect new mutations. We confirmed previous results showing no evidence for a functional role of the T12A mutation. Surprisingly, the T54A polymorphism, which was present in 7.4% of the Chinese patients was absent in our Caucasian population. This remarkable difference represent an example of how ethnic background is important also for polymorphisms involved in spermatogenesis and contributes to better select clinically relevant tests, specifically based on the ethnic origin of the infertile patients.

Susceptibility gene for non-obstructive azoospermia in the HLA class II region: correlations with Y chromosome microdeletion and spermatogenesis

We previously reported an association between the human leukocyte antigen (HLA) haplotype DRB1*1302-DQB1*0604 in the HLA class II region and non-obstructive azoospermia in Japanese men. To identify possible associations between the HLA-DRB1*1302-DQB1*0604 allele in the HLA class II region and azoospermia factor (AZF) deletion in the Y chromosome, we performed genomic polymerase chain reaction (PCR) analysis of the AZF region. We then determined spermatogenic impairment (Johnsen score) in testicular biopsy specimens from patients with or without the DRB1*1302-DQB1*0604 haplotype. The AZF microdeletion rate in patients with this haplotype was 3.85%, compared with 11.8% in others (no correlation). However, Johnsen scores in patients with the DRB1*1302-DQB1*0604 haplotype were 3.13 +/- 1.34 (mean +/- SD), compared with 3.70 +/- 1.51 in others (p < 0.05). While the DRB1*1302-DQB1*0604 haplotype acts independently from Y chromosome deletion, the haplotype might either act directly, or be functionally related to an unknown autosomal gene. In either case, this haplotype showed association with severe spermatogenic impairment.

Clinical analysis of patients with azoospermia factor deletions by microdissection testicular sperm extraction

Microdeletions of the azoospermia factor (AZF) locus on the Y chromosome have been implicated as a major genetic component of idiopathic male infertility, and the incidence of AZF deletions has been reported to be 15-20% in men with non-obstructive azoospermia (NOA). Numerous studies have described AZF deletion rates in patients with azoospermia; however, a clinical comparison of azoospermic patients with AZF deletion and those with no deletion has not been reported well. A new technique for testicular sperm extraction, microdissection testicular sperm extraction (TESE), has been used widely on NOA patients. Although testicular spermatozoa are reliably detected and retrieved from NOA patients by microdissection TESE, sperm retrieval rates for patients with AZF deletions are not well known. Therefore, characteristics of NOA patients with AZF deletion were investigated. Six of 60 patients (10%) who underwent microdissection TESE were found to have AZF deletions by genomic polymerase chain reaction. Testicular data, outcome of sperm retrieval and endocrinological profiles, were compared between patients with AZF deletions (n = 6) and those with no deletions (n = 54). Testicular size, varicocele rates and testicular histology were similar between the groups. Significant differences were not detected in the endocrinological profiles. Sperm retrieval rates were not significantly different between the groups. In conclusion, AZF deletions do not appear to confer specific characteristics to NOA patients.

Susceptibility locus for non-obstructive azoospermia is localized within the HLA-DR/DQ subregion: primary role of DQB1*0604

Non-obstructive azoospermia is a male infertility characterized by no or little sperm in semen as a result of a congenital dysfunction in spermatogenesis. Previous studies have reported a higher prevalence of particular human leukocyte antigen (HLA) antigens in non-obstructive azoospermia. As the expression of the RING3 gene located in the HLA class II region was predominant in the testis, mainly around spermatids and pachytene spermatocytes, it is tempting to speculate that RING3 is one of the strong candidate genes responsible for the pathogenesis of the disease. In this study, the genetic polymorphism in the RING3 gene was investigated by the direct sequencing technique. As a result, a total of 14 single nucleotide polymorphisms were identified. Among them, six were localized in the coding region but none of them was accompanied by an amino-acid substitution. No significant difference in the allelic distribution at these 14 polymorphic sites was observed between the patients and healthy controls, suggesting that the susceptible gene for non-obstructive azoospermia is not the RING3 gene. Then, in order to map the susceptibility locus for non-obstructive azoospermia precisely within the HLA region, 11 polymorphic microsatellite markers distributed from the SACM2L gene just outside the HLA class II region (187 kb telomeric of the DPB1 gene) to the OTF3 gene in the HLA class I region were subjected to association analysis in the patients. Statistical analysis of distribution in the allelic frequency at each microsatellite locus demonstrated that the pathogenic gene for non-obstructive azoospermia is located within the HLA-DR/DQ subregion. In fact, DRB1*1302 and DQB1*0604 were found to be strongly associated with non-obstructive azoospermia by polymerase chain reaction-based DNA typing. Further, haplotype analysis suggested that the DQB1*0604 allele may play a decisive role in the pathogenesis of non-obstructive azoospermia.