Editor-in-Chief
Prof. Yi-Fei WANG,
Asian J Androl 2006; 8 (1): 39-44 |
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This web only provides the extract of this article. If you want to read the figures and tables, please reference the PDF full text on Blackwell Synergy. Thank you. - Original Article - Y-chromosomal microdeletions and partial deletions of the Azoospermia Factor c (AZFc) region in normozoospermic, severe oligozoospermic and azoospermic men in Sri Lanka L. Fernando1,2, J. Gromoll1, T. R. Weerasooriya2, E. Nieschlag1, M. Simoni1 1Institute of Reproductive Medicine of the University, Münster University Hospital, D-48129 Münster, Germany Abstract Aim: To assess for the first time the occurrence of Y chromosomal microdeletions and partial deletions of the Azoospermia Factor c (AZFc) region in Sri Lankan men and to correlate them with clinical parameters. Methods: In a retrospective study, we analyzed 96 infertile men (78 with non-obstructive azoospermia) and 87 controls with normal spermatogenesis. AZFa, AZFb, AZFc and partial deletions within the AZFc region were analyzed by multiplex polymerase chain reaction (PCR) according to established protocols. Results: No AZFa, AZFb or AZFc deletions were found in the control group. Seven patients in the group of infertile men were found to have deletions as following: one AZFa, two AZFc, two AZFbc and two AZFabc. The relative distribution of these patterns was significantly different compared with that found in the German population. Extension analysis confirmed that the deletions occurred according to the current pathogenic model. gr/gr deletions were found to be equally present both in the patients (n = 4) and in the control group (n = 4). One b2/b3 deletion was found in the patient group. Conclusion: These results suggest that the frequency and pattern of microdeletions of the Y chromosome in Sri Lankan men are similar to those found in other populations and confirm that gr/gr deletions are not sufficient to cause spermatogenetic failure. (Asian J Androl 2006 Jan; 8: 39-44) Keywords: Y chromosome; male infertility; gr/gr; b2/b3; microdeletion; normozoospermia; azoospermia factor c Correspondence to: Prof. E. Nieschlag, FRCP, Institute of Reproductive Medicine of the University, Münster University Hospital,
Domagkstraße 11, D-48129 Münster, Germany
1 Introduction
Infertility affects approximately 15 % of married couples and, of these cases, approximately 50 % are due to male factors [1]. Although the causes of male infertility may vary with the geographical region and ethnic make-up of the population, a reasonable number of male infertility cases are related to genetic factors. The most common chromosomal disorder in male infertility is Klinefelter syndrome, which is responsible for approximately 1.8 % of all cases [2]. The second most common genetic cause is microdeletions in the azoospermia factor (AZF) region of the Y chromosome [3]. The Y chromosome is the smallest chromosome in the human genome and is only transmitted from fathers to sons. In addition to the testis determining factor (SRY), located in the Yp region, the Y chromosome long arm (Yq region) harbors genes which regulate spermatogenesis [4]. Although the complete sequence of the Y chromosome is now known [4], the pathophysiological correlation between Y chromosomal microdeletions and the resulting impairment of spermatogenesis has not been fully established. Although it is difficult to establish precise genotype/phenotype correlations in patients with Y chromosomal microdeletions, deletions of AZFa or AZFb and deletions involving more than one region (AZFbc or AZFabc) have more severe effects on spermatogenesis than deletions of the AZFc region [3, 5]. Furthermore, different frequencies and different patterns of Yq deletions, both microdeletions and partial deletions of the AZFc region, have been reported in different geographical regions and ethnic groups. In Europe, the overall AZF deletion frequency is approximately 8 % of men with non-obstructive azoospermia or severe oligozoospermia, affecting the AZFc region in most cases [6]. Multi-region involvement (AZFbc or AZFabc) and deletions of AZFa were recorded at very low frequencies in the German population [7]. The published data for Asia indicated a certain variability in the deletion frequency depending on the selection criteria of the patients. When patients with azoospermia or severe oligozoospermia are considered together, the frequency of microdeletions varies from 5 % in Eastern Uttar Pradesh in India [8], to 7.6 % in Japan [9], 8.5 % in Calcutta, India [10], 9 % in China [11] and 10.6 % in Taiwan, China [12]. Interestingly, much higher frequencies of AZFa deletions (17.2 % in India) and AZFbc deletions (51.7 % in India and 36.6 % in China) have been recorded, compared with those in Europe [10, 11]. Recently, partial deletions of the AZFc region (e.g. gr/gr or b1/b3 resulting from homologous recombination between amplicons within the AZFc region, and removing smaller numbers of genes compared to complete AZFc deletions, have been described [13]. The exact effects of these partial AZFc deletions on spermatogenesis are still controversial. Some studies reported a significant association between partial AZFc deletions and spermatogenic failure [13, 14] but others did not [15, 16]. However, as the penetrance of these partial deletions is far lower than that of deletions involving the entire AZFc, it is to be expected that these partial deletions would not have severe effects on spermatogenesis. Data on the partial deletions of the AZFc region are still scant and indicate frequencies of between 4 % and 6 % of men with spermatogenetic failure [13-16]. In addition, some deletion patterns are more common in some populations, for example, in Eastern Siberian Yakuts [17], and are compatible with normal spermatogenesis and fertility [15, 16]. These studies suggest that geographical and ethnic differences might influence the frequencies of AZF deletions and of partial deletions of the AZFc region, as well as the deletion patterns and, possibly, the phenotypic expression. In this study, the occurrence of Y chromosomal microdeletions and partial deletions of the AZFc region were assessed for the first time in Sri Lankan men.
2 Material and methods
2.1 Study group The study group, consisting of infertile patients and semen donors attending the Reproductive Biology Laboratory, Faculty of Medicine, Galle, Sri Lanka, was selected retrospectively. All men gave written consent to voluntary participation in the study. Approval for the study was given by the Ethics Committee, Faculty of Medicine, Galle, Sri Lanka. Permission to use the available clinic data was obtained by the Reproductive Biology Laboratory administration. Ninety-six patients were investigated, comprising two oligozoospermic men (sperm concentration < 20 × 106/mL but > 1 × 106/mL), 15 severely oligozoospermic men (sperm concentration < 1 × 106/mL) and 79 men with non-obstructive azoospermia. A questionnaire was distributed to each patient to collect demographic data, past medical and surgical history, including history of orchitis, mumps, testicular maldescent, testicular injuries, chemotherapy and radiotherapy, and habits concerning smoking and alcohol consumption. All patients were examined by a clinician for size, volume and consistency of the testis, hydrocele, varicocele and secondary sexual characteristics. Hormone profiles (serum follicle-stimulating hormone [FSH], luteinizing hormone [LH] and testosterone) of all patients were collected and, whenever available, historical testicular biopsy reports were collected. Eighty-seven men of Sri Lankan origin, who were sperm donors for heterologous insemination with normal ejaculate parameters, according to the World Health Organization (WHO) criteria [18], were recruited as the control group.
2.2 Molecular analysis Five mL of ethylene diamine tetraacetic acid (EDTA) blood was collected from each man in the study groups and genomic DNA was extracted using the Wizard DNA extraction kit (Promega, Madison, WI, USA) according to the manufacturer¡¯s protocol. Microdeletion analysis of the Y chromosome Yq AZF region involved two steps. In the first step, aimed at detecting AZFa, AZFb and AZFc microdeletions, two multiplex polymerase chain reaction (PCR) systems (A and B) were carried out according to the European Academy of Andrology/European Molecular Genetics Quality Network (EAA/EMQN) guidelines [3] using the recommended first choice primers and the Qiagen Multiplex PCR kit (Qiagen, Hilden, Germany). Each 50 µL PCR reaction mix contained 25 µL 2 × Qiagen Multiplex PCR MasterMix (containing HotStarTaq DNA polymerase [Qiagen, Hilden, Germany], Qiagen Multiplex PCR Buffer [containing 6 mmol/L MgCl2] and deoxyribonucleotide triphosphate mix), 5 µL 10 × Primer mix (2 µmol/L each primer), ~ 1 µg template DNA, and sterile distilled water to 50 µL. Amplification started with an activation step of 15 min at 95 ºC, followed by 35 cycles of 30 s denaturation (94 ºC), 90 s annealing (57 ºC) and 60 s elongation (72 ºC), ended by an elongation step of 10 min and cooling to 4 ºC. Reaction products (30 µL) were separated on 2 % agarose (Peqbold Universal Agarose, Peqlab, Erlangen, Germany) plus 0.5 % DNA agar (Serva, Heidelberg, Germany) gels in 1 ¡Á Tris borate EDTA (TBE) for 25 V overnight. Extension analysis was performed according to the EAA/EMQN guidelines [3]. In the second step, we used two multiplex systems, one including the sequence tagged site (STS) primers sY1291, sY1191 and sY1161 and the other including sY1201 and sY1206 to screen the partial deletions of the AZFc region, as described previously [15]. The samples, in which the deletions were detected by the above multiplex systems, were confirmed by repeating the single primer (simplex) reactions. 2.3 Statistical analysis Fisher¡¯s exact test and the c2 test were used to compare the frequency of deletions by applying a commercially available software package (GraphPad Prism version 3; GraphPad Software, San Diego, CA, USA). P < 0.05 was considered statistically significant.
3 Results
Seven of the 96 infertile men (7.3 %) were found to have Y chromosome microdeletions in the AZF region (Table 1). One of these seven men (case 18) had severe oligozoospermia, and the rest had azoospermia. All men with microdeletions had normal serum testosterone levels. Five patients had high serum FSH levels. One patient (case 96) showed increased serum FSH and LH levels; the LH level was normal in the others. The microdeletion patterns observed were AZFc in two patients (cases 18 and 38), AZFbc in two patients (cases 48 and 84), AZFa in one patient (case 87) and AZFabc in two patients (cases 20 and 96). The further characterization of the microdeletions by extension analysis showed a complete AZFa deletion in case 87 (sY82 and sY83 present, DBY, USP9Y and sY87 deleted, sY88 present) and deletion of the marker sY160 in cases 20 and 96, suggesting a large, terminal deletion in these two patients. Due to a shortage of DNA we could further analyze only one of the two patients with the AZFbc deletion pattern. Using the STS markers, sY1264, sY1227, sY1228, sY1283, sY117, sY1291, sY639, sY1206 and sY1201, case 84 showed a pattern corresponding to the deletion model P4/distal P1 according to Repping et al. [13]. No microdeletions were found in the control group. Two different patterns of partial deletions within the AZFc region were observed in five men in the patient group. Four (4.17 %) had gr/gr deletions and one (1.04 %) had a b2/b3 deletion pattern (Table 2). One man with gr/gr deletion was oligozoospermic (sperm concentration 4.2 × 106/mL) but the others were azoospermic. Testicular biopsy reports were available for three of the five patients with partial deletions of the AZFc region. Two cases (cases 28 and 93) had Sertoli cell-only syndrome (SCOS) and one patient (case 24) had seminiferous tubule atrophy. Four subjects of the control group were detected to have gr/gr deletions, which was the only pattern of partial deletions of the AZFc region observed in the control group. All of them had normal ejaculate parameters (Table 3). The statistical analysis of gr/gr deletions in the control group and the patient group did not show any significant difference (Fisher¡¯s exact test, P = 0.72). A comparison of the relative frequency of the type of microdeletions of the Y chromosome in Sri Lanka and Germany, according to the authors¡¯ previously published data [3], is shown in Table 4. A statistically significant difference in the distribution of the deletion pattern was observed. In particular, on the basis of the present results, AZFc microdeletions seem to be less frequent than the other patterns in Sri Lankan men compared to German men. 4 Discussion
Collecting demographic data is important in order to assess the appropriateness of the current analysis protocols [3], which might require adjustments of the STS panel according to the ethnic origin of the patients [19]. In this study we analyzed for the first time microdeletions of the Y chromosome in a small sample of Sri Lankan men. We found AZF microdeletions in 7.3 % of a selected group of infertile patients, a frequency similar to that of 8 % recorded as the overall frequency for AZF deletions among infertile patients [6]. Therefore, the frequency of Y chromosomal microdeletions in Sri Lankan men is similar to that observed in different regions of India [8, 10, 20]. The frequency distribution of the different types of AZF deletions, however, seems to be different from that observed in European men of German origin, suggesting that ethnic differences, possibly reflected by Y chromosome haplogroups, might result in a higher incidence of rare microdeletions in some populations. In a previous study conducted with Indian men, a similar overall frequency of Y chromosomal microdeletions was found, with a very high incidence (24.4 %) of AZFa microdeletions [10] and complex patterns within this region which, however, were not verified by Southern blotting. More data should be collected in order to verify whether Indian men might be more prone to AZFa deletions than European men. Extension analysis of the two patients in our study with AZFabc deletions showed that the heterocromatic marker sY160 was absent in both cases, suggesting the occurrence of a terminal deletion. Cytogenetic investigation, however, was not performed in these men. The further molecular analysis of one case with AZFa and one case with AZFbc deletions confirmed the complete removal of the entire AZFa region, including the two genes present in it, and the deletion pattern P4/distal P1 in the latter case. This suggests that the mechanism of microdeletions, that is, homologous recombination between identical sequences flanking the deletion, should be valid independently of the ethnic origin of the Y chromosome. The patients with AZFa or AZFabc deletion patterns showed SCOS in their biopsy reports. One of the two patients with an AZFbc deletion pattern showed maturation arrest. The second patient had SCOS. These findings are compatible with the recorded trend of genotype/phenotype correlation reported in other studies [5] and the concept that complete deletions of the AZFa, or AZFb, or AZFbc region result in SCOS or maturation arrest and the virtual impossibility of retrieving sperm by testicular sperm extraction attempts. Of the two patients with AZFc deletions, one was severely oligozoospermic and the other was azoospermic with, surprisingly, a normal testicular biopsy. The latter case suggests that an obstruction might be present in this patient, compatible with his normal serum FSH levels, and reinforces the concept that AZFc deletions might be compatible with spermatogenesis sufficient for fertility [21 and references therein], provided that no obstructions are concomitantly present. In this study, we analyzed for the first time the occurrence of partial deletions of the AZFc region in a small sample of Sri Lankan men. The commonest partial AZFc deletion pattern observed was the gr/gr pattern, which was detected in four (4.2 %) patients and four (4.6 %) control men, indicating no difference in the occurrence of gr/gr deletions between patients and controls. Our Sri Lankan data confirm previous findings in other populations that partial deletions of the AZFc region are not sufficient to cause spermatogenetic failure. This finding is in contrast with some recent data reporting a significant correlation between the presence of gr/gr deletion and spermatogenic failure in Spanish men [14]. Similar to the present finding, however, Hucklenbroich et al. [15] and Machev et al. [16] found no significant differences between the control group and the patient group. gr/gr deletions have been associated with particular Y chromosomal haplogroups [13]. Although the correct distribution pattern of Y haplogroups in Asian populations is still not known, haplogroup N, which is susceptible to spontaneous gr/gr deletions, is reported to be common in this region [22]. In any case, our results show clearly that gr/gr deletions cannot be considered sufficient cause for spermatogenic failure. Haplogroup and gr/gr analysis in large groups of men of different ethnic origin with normal spermatogenesis need to be performed to characterize the role played by this type of chromosomal rearrangement in male fertility. Meanwhile, we see no basis to recommend screening for gr/gr deletions as a routine investigation in male infertility.
Acknowledgment
This study was supported by the Special Programme in Human Reproduction of the World Health Organization with a fellowship to Dr L. Fernando. The excellent technical assistance of Dr S. Borchert and the language editing by Dr S. Nieschlag are gratefully acknowledged. References 1 Nieschlag E, Behre HM, Meschede, Kamischke A. Disorders at the testicular level. In: Nieschlag E, Behre HM, editors. Andrology. Male reproductive health and dysfunction, 2nd ed. Berlin: Springer Verlag; 2000. p144-76. 2 Lanfranco F, Kamischke A, Zitzmann M, Nieschlag E. Klinefelter's syndrome. Lancet 2004; 364: 273-83. 3 Simoni M, Bakker E, Krausz C. EAA/EMQN best practice guidelines for molecular diagnosis of Y-chromosomal microdeletions. State of the art 2004. Int J Androl 2004; 27: 240-9. 4 Skaletsky H, Kuroda-Kawaguchi T, Minx PJ, Cordum HS, Hillier L, Brown LG, et al. The male-specific region of the human Y chromosome is a mosaic of discrete sequence classes. Nature 2003; 423: 825-37. 5 Hopps CV, Mielnik A, Goldstein M, Palermo GD, Rosenwaks Z, Schlegel PN. Detection of sperm in men with Y chromosome microdeletions of the AZFa, AZFb and AZFc regions. Hum Reprod 2003; 18: 1660-5. 6 Simoni M, Kamischke A, Nieschlag E. Current status of the molecular diagnosis of Y-chromosomal microdeletions in the work-up of male infertility. Initiative for international quality control. Hum Reprod 1998; 13: 1764-8. 7 Maurer B, Gromoll J, Simoni M, Nieschlag E. Prevalence of Y chromosome microdeletions in infertile men who consulted a tertiary care medical centre: the Münster experience. Andrologia 2001; 33: 27-33. 8 Ambasudhan R, Singh K, Agarwal JK, Singh SK, Khanna A, Sah RK, et al. Idiopathic cases of male infertility from a region in India show low incidence of Y-chromosome microdeletion. J Biosci 2003; 28: 605-12. 9 Kato H, Komori S, Nakata Y, Sakata K, Kanazawa R, Handa M, et al. Screening for deletions in interval D16-22 of the Y chromosome in azoospermic and oligozoospermic Japanese men. J Hum Genet 2001; 46: 110-4. 10 Thangaraj K, Gupta NJ, Pavani K, Reddy AG, Subramanian S, Rani DS, et al. Y-chromosome deletions in azoospermic males in India. J Androl 2003; 24: 588-97. 11 Chiang HS, Yeh SD, Wu CC, Huang BC, Tsai HJ, Fang CL. Clinical and pathological correlation of the microdeletion of Y chromosome for 30 patients with azoospermia and severe oligoasthenospermia. Asian J Androl 2004; 6: 369-75. 12 Lin YM, Chen CW, Sun HS, Hsu CC, Chen JM, Lin SJ, et al. Y-chromosome microdeletion and its effect on reproductive decisions in Taiwanese patients presenting with nonobstructive azoospermia. Urology 2000; 56: 1041-6. 13 Repping S, Skaletsky H, Brown L, van Daalen SK, Korver CM, Pyntikova T, et al. Polymorphism for a 1.6-Mb deletion of the human Y chromosome persists through balance between recurrent mutation and haploid selection. Nature Genet 2003; 35: 247-51. 14 de Llanos M , Ballescà JL, Gázquez C, Margarit E, Oliva R. High frequency of gr/gr chromosome Y deletions in consecutive oligospermic ICSI candidates. Hum Reprod 2005; 20: 216-20. 15 Hucklenbroich K, Gromoll J, Heinrich M, Hohoff C, Nieschlag E, Simoni M. Partial deletions in the AZFc region of the Y chromosome occur in men with impaired as well as normal spermatogenesis. Hum Reprod 2005; 20: 191-7. 16 Machev N, Saut N, Longepied G, Terriou P, Navarro A, Levy N, et al. Sequence family variant loss from the AZFc interval of the human Y chromosome, but not gene copy loss, is strongly associated with male infertility. J Med Genet 2004; 41: 814-25. 17 Repping S, van Daalen S, Korver CM, Brown LG, Marszalek JD, Gianotten J, et al. A family of human Y chromosomes has dispersed throughout northern Eurasia despite a 1.8-Mb deletion in the azoospermia factor c region. Genomics 2004; 83: 1046-52. 18 World Health Organization. Laboratory Manual for the Examination of Human Semen and Sperm-Cervical Mucus Interaction, 4th ed. Cambridge: Cambridge University Press; 1999. 19 Peterlin B, Kunej T, Hristovski D. Diagnostic test for Y chromosome microdeletion screening in male infertility. Genet Test 2004; 8: 45-9. 20 Mittal RD, Singh G, Srivastava A, Pradhan M, Kesari A, Makker A, et al. Y chromosome micro-deletions in idiopathic infertility from Northern India. Ann Genet 2004; 47: 331-7. 21 Kühnert B, Gromoll J, Kostova E, Tschanter P, Luetjens CM, Simoni M, et al. Natural transmission of an AZFc Y-chromosomal microdeletion from father to his sons. Case report. Hum Reprod 2004; 19: 886-8. 22 Fernandes S, Paracchini S, Meyer LH, Floridia G, Tyler-Smith C, Vogt PH. A large AZFc deletion removes DAZ3/DAZ4 and nearby genes from men in haplogroup N. Am J Hum Genet 2004; 74: 180-7. |
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