Microdeletion of the DAZ (deleted in azoospermia) gene or the YRRM (Y chromosome ribonucleic acid recognition motif) gene does not occur in patients with Klinefelter's syndrome with and without spermatogenesis

Bridging the Gap between AZF Microdeletions and Karyotype: Twelve Years' Experience of an Infertility Center

PURPOSE

Despite all past efforts, the current guidelines are not explicit enough regarding the indications for performing azoospermia factor (AZF) screening and karyotype, burdening clinicians with the decision to assess whether such tests are meaningful for the infertile male patient. These assessments can be costly and it is up to the healthcare practitioner to decide which are necessary and to weigh the benefits against economic/psychological harm. The aim of this study is to address such gaps and provide update on current management options for this group of patients.

MATERIALS AND METHODS

To address such gaps in male infertility management and to elucidate whether AZF screening is indicated in individuals who concomitantly harbor chromosomal abnormalities we conducted a retrospective cohort analysis of 10,388 consecutive patients with non-obstructive azoospermia (NOA) and severe oligozoospermia.

RESULTS

Previously, it has been suggested that all NOA cases with chromosomal defects, except males with 46,XY/45,X karyotype, have no indication for AZF screening. Our findings revealed that cases carrying the following chromosomal abnormalities inv(Y)(p11.2q12); idic(Y)(q11.2); 46,XY,r(Y); idic(Y)(p11.2) and der(Y;Autosome) (76/169; 44.9%; 95% CI, 37.7-52.5) should also be referred for AZF deletion screening. Here, we also report the correlation between sperm count and AZF deletions as a secondary outcome. In accordance with previously reported data from North America and Europe, our data revealed that only 1% of cases with >1×10⁶ sperm/mL had Y chromosome microdeletions (YCMs).

CONCLUSIONS

In the era of assisted reproduction, finding cost-minimization strategies in infertility clinics without affecting the quality of diagnosis is becoming one of the top prioritized topics for future research. From a diagnostic viewpoint, the results reflect a need to reconsider the different karyotype presentations and the sperm count thresholds in male infertility guidelines as indicators for YCM screening during an infertility evaluation.

Epigenetics and genomics in Klinefelter syndrome

Since the first description of Klinefelter syndrome (KS) was published in 1942 in The Journal of Clinical Endocrinology, large inter-individual variability in the phenotypic presentation has been demonstrated. However, our understanding of the global impact of the additional X chromosome on the genome remains an enigma. Evidence from the existing literature of KS indicates that not just one single genetic mechanism can explain the phenotype and the variable expressivity, but several mechanisms may be at play concurrently. In this review, we describe different genetic mechanisms and recent advances in the understanding of the genome, epigenome, and transcriptome of KS and the link to the phenotype and clinical heterogeneity. Future studies are needed to unite clinical data, genomic data, and basic research attempting to understand the genetics behind KS. Unraveling the genetics of KS will be of clinical relevance as it may enable the use of polygenic risk scores to predict future disease susceptibility and enable clinical risk stratification of KS patients in the future.

Incidence of Y chromosome microdeletions in patients with Klinefelter syndrome

PURPOSE

The aim of this study was to study the incidence of Y chromosome microdeletions in a Caucasian population of Klinefelter syndrome (KS) patients and to investigate the possible association between Y chromosome microdeletions and KS.

MATERIALS AND METHODS

We conducted a retrospective study on 118 KS patients, 429 patients with non-obstructive azoospermia (NOA), and 155 normozoospermic men. Eight of the 118 KS patients had undergone testicular sperm extraction (TESE). All patients underwent semen examination and Y chromosome microdeletions evaluated by PCR, using specific sequence tagged site (STS) primer sets, which spanned the azoospermia factor AZFa, AZFb, and AZFc regions of the Y chromosome.

RESULTS

Semen analysis of the KS group revealed: 1 patient with oligozoospermia, 1 with severe oligoasthenoteratozoospermia, 2 with cryptozoospermia, and 114 with azoospermia. Eight of the 114 azoospermic KS patients underwent TESE, and spermatozoa were recovered from three of these, all of whom had non-mosaic karyotype 47, XXY. 10.7% of the NOA patients presented AZF microdeletions. In 429 cases with NOA, 8 cases had AZFa + b + c deletion, 6 cases had AZF b + c deletion, 4 cases had AZFa microdeletion, 8 cases had AZFb microdeletion, and 20 cases had AZFc microdeletion. Just one KS patient (0.8%) presented microdeletion in the AZFc region.

CONCLUSION

The percentage of microdeletions in KS patients was lower than in NOA patients, suggesting that AZF microdeletions and KS do not have a causal relationship and that Y chromosome microdeletions are not a genetic factor linked to KS.

Expression analysis of RNA-binding motif gene on Y chromosome (RBMY) protein isoforms in testis tissue and a testicular germ cell cancer-derived cell line (NT2)

BACKGROUND

RNA-binding motif gene on Y chromosome (RBMY), a germ cell-specific nuclear protein, is known as a key factor in spermatogenesis and disorders associated with this protein have been recognized to be related to male infertility. Although it was suggested that this protein could have different functions during germ cell development, no studies have been conducted to uncover the mechanism of this potential function yet. Here, we analyzed the expression pattern of RBMY protein isoforms in testis compared to NT2, a testicular germ cell cancer-derived cell line, to test probability of differential expression of RBMY protein isoforms at different spermatogenesis stages.

METHODS

Full length and a segment of RBMY gene were cloned and expressed in E. coli. Anti-human RBMY antibody was produced in rabbit using the recombinant proteins as antigen. Western-blot and immunofluorescence were conducted for detection and comparison of RBMY protein isoforms.

RESULTS

Selected segment of RBMY protein resulted in producing a mono-specific antibody. As results shows, only the longest isoform of RBMY was expressed at protein level in NT2 cell line, while three isoforms of this protein were detected in the whole testis lysate.

CONCLUSION

The results imply that different alternative splicing may happen in testis cells and probably difference of RBMY function during spermatogenesis is due to the differential expression of RBMY protein isoforms. These results and further experiments on RBMY isoforms can help to obtain a better understanding of the function of this protein, which may increase our knowledge about spermatogenesis and causes of male infertility.

Chromosomal defects in infertile men with poor semen quality

PURPOSE

To assess the incidence and the type of chromosomal aberrations in males with infertility we reviewed cytogenetic results in 76 Tunisian infertile men (54 nonobstructive azoospermia and 22 oligo-asthenospermia).

METHODS

Karyotyping was performed on peripheral blood lymphocytes according to the standard methods. Molecular diagnosis of classical and partial Y-chromosomal microdeletions was performed by amplifying Y-specific STSs markers.

RESULTS

Various numerical and structural chromosome abnormalities were identified in 15 patients (19.48%). The occurrence of chromosomal abnormality in the azoospermics and severe oligo-asthnospermic was 21.7% and 13.5%, respectively. The most common was Klinefelter syndrome, accounting for 10 of the 15 cytogenetic defects. The total frequency of Y chromosomal microdeletions was 17.1%, with respective frequencies in azoospermic and severe oligospermic groups, 11.1% and 31.8%. The most frequent of Y chromosomal deletions were the partial ones (11.1% in azoospermic and 27.2% in oligospermic).

CONCLUSION

The occurrence of chromosomal abnormalities among infertile males strongly suggests the need for routine genetic testing and counseling prior to the employment of assisted reproduction techniques.

The azoospermia factor locus-c region was found to be related to Klinefelter syndrome in Turkish patients

We looked for a possible association between Klinefelter syndrome (KFS) and microdeletions in the Y chromosome in Turkish KFS patients. We examined the frequency of KFS in male patients with proven non-obstructive azoospermia and the types of Y chromosome microdeletions in these KFS patients. Fifty azoospermic patients and 50 fertile men were included in this study. KFS was found in 14 azoospermic patients. Y chromosome microdeletions were found in eight KFS patients. Azoospermia factor locus c (AZFc) was the most commonly deleted interval in KFS patients. All KFS patients had elevated plasma follicle-stimulating hormone and luteinizing hormone concentrations, but they had normal plasma testosterone concentrations. Testis biopsy of five samples with Y microdeletions revealed Sertoli cell-only syndrome. No Y microdeletions were found in the fertile group. We concluded that there could be an association between the AZFc region and KFS. Screening for this should be part of diagnostic work-up, particularly in those considering assisted reproduction.

Y CHROMOSOME MICRODELETION IN A CASE WITH KLINEFELTER'S SYNDROME

In male infertility, the frequency of genetic factors is high. Klinefelter's Syndrome is the most frequent sex chromosomal abnormality detected in male infertility. In this study we report a patient diagnosed with Klinefelter's Syndrome with a deletion of the Yq interval. The patient was 24-years old with primary infertility. Semen analyses carried out in triplicate indicated azoospermia. The plasma leutenizing hormone (LH) and follicle stimulating hormone (FSH) levels were abnormally high and the testosterone level was lower than the usual range. Each of his testes had a volume of 3 cc. Peripheral blood karyotype analysis showed Klinefelter's Syndrome (47, XXY) pattern. Polymerase chain reaction amplification of DNA was performed using the following primers; AZFa (sY81, sY82, sY84), AZFb (sY127, sY142, sY164, RBM1), AZFc (CDY, BPY, sY254, sY255, sY277), AZFd (sY152, sY145, sY153). Analysis revealed a single deletion of AZFa region (sY84). Deletion of the AZFa region may be an additional factor for absolute azoospermia in men with Klinefelter's Syndrome. For individuals with Klinefelter's Syndrome who plan to undergo assisted reproduction techniques, Y chromosome microdeletion screening can diagnostically be convenient.

Routine screening for classical azoospermia factor deletions of the Y chromosome in azoospermic patients with Klinefelter syndrome

AIM

To evaluate the occurrence of classical azoospermia factor (AZF) deletions of the Y chromosome as a routine examination in azoospermic subjects with Klinefelter syndrome (KS).

METHODS

Blood samples were collected from 95 azoospermic subjects with KS (91 subjects had a 47,XXY karyotype and four subjects had a mosaic 47,XXY/46,XY karyotype) and a control group of 93 fertile men. The values of testosterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured. To determine the presence of Y chromosome microdeletions, polymerase chain reaction (PCR) of five sequence-tagged site primers (sY84, sY129, sY134, sY254, sY255) spanning the AZF region, was performed on isolated genomic DNA.

RESULTS

Y chromosome microdeletions were not found in any of the 95 azoospermic subjects with KS. In addition, using similar conditions of PCR, no microdeletions were observed in the 93 fertile men evaluated. The level of FSH in KS subjects was higher than that in fertile men (38.2 +/- 10.3 mIU/mL vs. 5.4 +/- 2.9 mIU/mL, P < 0.001) and the testosterone level was lower than that in the control group (1.7 +/- 0.3 ng/mL vs. 4.3 +/- 1.3 ng/mL, P < 0.001).

CONCLUSION

Our data and review of the published literature suggest that classical AZF deletions might not play a role in predisposing genetic background for the phenotype of azoospermic KS subjects with a 47,XXY karyotype. In addition, routine screening for the classical AZF deletions might not be required for these subjects. Further studies including partial AZFc deletions (e.g. gr/gr or b2/b3) are necessary to establish other mechanism underlying severe spermatogenesis impairment in KS.

Y chromosome microdeletions in azoospermic patients with Klinefelter's syndrome

AIM

To study the occurrence of Y chromosome microdeletions in azoospermic patients with Klinefelter's syndrome (KFS).

METHODS

Blood and semen samples were collected from azoospermic patients with KFS (n = 14) and a control group of men of proven fertility (n = 13). Semen analysis was done according to World Health Organization (WHO) guidelines. Blood samples were processed for karyotyping, fluorescent in situ hybridization (FISH) and measurement of plasma follicle stimulating hormone (FSH) by radioimmunoassay. To determine Y chromosome microdeletions, polymerase chain reaction (PCR) of 16 sequence tagged sites (STS) and three genes (DFFRY, XKRY and RBM1Y) was performed on isolated genomic DNA. Testicular fine needle aspiration cytology (FNAC) was done in selected cases.

RESULTS

Y chromosome microdeletions spanning the azoospermia factor (AZF)a and AZFb loci were found in four of the 14 azoospermic patients with KFS. Karyotype and FISH analysis revealed that, of the four cases showing Y chromosome microdeletion, three cases had a 47,XXY/46,XY chromosomal pattern and one case had a 46,XY/47,XXY/48,XXXY/48,XXYY chromosomal pattern. The testicular FNAC of one sample with Y chromosome microdeletion revealed Sertoli cell-only type of morphology. However, no Y chromosome microdeletions were observed in any of the 13 fertile men. All patients with KFS had elevated plasma FSH levels.

CONCLUSION

Patients with KFS may harbor Y chromosome microdeletions and screening for these should be a part of their diagnostic work-up, particularly in those considering assisted reproductive techniques.

Idiopathic non-obstructive azoospermia or severe oligozoospermia: a cross-sectional study in 61 Greek men

Idiopathic non-obstructive azoospermia or severe oligozoospermia (INOA) consists a special group of men characterized by eugonadism, primary infertility, low testicular volume, azoospermia or severe oligozoospermia and high follicle stimulating hormone values. Aims of this study were to describe the clinical, hormonal, sperm and histological characteristics of men with INOA and to define if and to what extend men with the INOA phenotype carry Y chromosome long arm (Yq) microdeletions. Sixty-three men with INOA were studied through clinical examination, spermiograms, hormonal profile, polymerase chain reaction for Yq microdeletions, karyotype and testicular fine-needle aspiration biopsy. Sixty-seven men with infertility of known causes and sixty fertile men served as controls. Men with INOA had significantly lower total testosterone levels than fertile men as well as higher prevalence of loss of libido, higher luteinizing hormone levels and lower sperm volume whereas men with infertility of known causes had intermediate values. The prevalence of Yq microdeletions was 3% in men with INOA, 3% in men with infertility of known causes (all of them with abnormal karyotype) and 0% in fertile men. In conclusion, men with INOA have more severe testiculopathy than these with infertility of known causes. These men may be at increased risk of developing partial androgen deficiency of the aging male.

Absence of Yq microdeletions in infertile men

Microdeletions of the long arm of the Y chromosome (Yq) were described in men with idiopathic azoo- or oligozoospermia and seem to cause impairment of spermatogenesis. Deletion frequencies differ considerably among selected infertile men. The aim of this study was to investigate the prevalence of Yq microdeletions in patients with idiopathic infertility. Men with azoospermia or oligozoospermia resulting from endocrine or obstructive causes or with a constitutional cytogenetic anomaly were excluded. Ninety-seven patients presenting at infertility centers in Leipzig and Zurich were included in the study. Sixty-four (66%) of them were severely oligozoospermic (sperm concentrations < 5 x 10(6)/mL) and 33 (36%) were azoospermic. A sequence-tagged site (STS) PCR strategy was applied for the microdeletion screening. Thirteen STS markers spanning the whole euchromatic region of Yq were used. No Y-chromosomal microdeletion could be detected in these 97 infertile men. This result suggests a much lower Yq deletion frequency than previously thought, even among strictly selected patients with idiopathic azoo- or oligozoospermia.

Y chromosome microdeletions and alterations of spermatogenesis

Three different spermatogenesis loci have been mapped on the Y chromosome and named "azoospermia factors" (AZFa, b, and c). Deletions in these regions remove one or more of the candidate genes (DAZ, RBMY, USP9Y, and DBY) and cause severe testiculopathy leading to male infertility. We have reviewed the literature and the most recent advances in Y chromosome mapping, focusing our attention on the correlation between Y chromosome microdeletions and alterations of spermatogenesis. More than 4,800 infertile patients were screened for Y microdeletions and published. Such deletions determine azoospermia more frequently than severe oligozoospermia and involve especially the AZFc region including the DAZ gene family. Overall, the prevalence of Y chromosome microdeletions is 4% in oligozoospermic patients, 14% in idiopathic severely oligozoospermic men, 11% in azoospermic men, and 18% in idiopathic azoospermic subjects. Patient selection criteria appear to substantially influence the prevalence of microdeletions. No clear correlation exists between the size and localization of the deletions and the testicular phenotype. However, it is clear that larger deletions are associated with the most severe testicular damage. Patients with Y chromosome deletions frequently have sperm either in the ejaculate or within the testis and are therefore suitable candidates for assisted reproduction techniques. This possibility raises a number of medical and ethical concerns, since the use of spermatozoa carrying Y chromosome deletions may produce pregnancies, but in such cases the genetic anomaly will invariably be passed on to male offspring.