| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Original Article |
Department of Early Childhood Education and Nursery (Y.-N.T.), Chia Nan University of Pharmacy and Science, Tainan 717; Departments of Urology (Y.-M.L., W.-C.T.), Medicine (S.-Y.T.), Pediatrics (S.-J.L.), and Obstetrics and Gynecology (P.-L.K.) and Institute of Molecular Medicine (Y.-H.L.), National Cheng Kung University College of Medicine, Tainan 704; and Taiwan United Birth Promoting Experts (C.-C.H.), Tainan 700, Taiwan
Address all correspondence and requests for reprints to: Pao-Lin Kuo, M.D., Division of Genetics, Department of Obstetrics and Gynecology, National Cheng Kung University Hospital, 138 Sheng-Li Road, Tainan, Taiwan 704. E-mail: paolink{at}mail.ncku.edu.tw.
Abstract
Single-strand conformation polymorphism analysis of exon-containing genomic DNA segments of the deleted-in-azoospermia-like (DAZL) gene was performed in 160 infertile Taiwanese men presenting with severe oligozoospermia and nonobstructive azoospermia. An A
G transition at nucleotide 386 in exon 3 was identified. The mutation is located within the RNA-recognition motif (aa 32–117) domain of the DAZL protein and will lead to Thr54Ala change (T54A) of DAZL protein. Analysis of cDNA from testicular tissue of infertile carriers showed absence of expression for the T54A allele, implying that the allele carrying T54A polymorphism is hardly, if ever, expressed. The frequencies of T54A allele in patients and the control group were 7.39% and 0.86%, respectively (P = 0.0003). The phenotypes varied significantly in cases with heterozygous T54A polymorphism, ranging from hypospermatogenesis and maturation arrest to Sertoli cell-only syndrome. A combination of DAZ gene deletion and T54A polymorphism did not worsen the phenotype. Our findings provide strong evidence for the role of the autosomal DAZL gene in human spermatogenesis.
APPROXIMATELY 5% OF otherwise healthy men suffer from involuntary childlessness for which no clinical explanation can be given (1). In roughly half of these cases, the defect can be traced to the man. In recent years, there has been an intensive search for genetic causes of male infertility, of which spermatogenic failure is the most common form. Screening with markers on the long arm of the human Y chromosome has detected Yq microdeletions in 5–15% of males with spermatogenic failure. Among cases with Yq microdeletions, deletion involving the DAZ (deleted in azoospermia) gene family represents the most frequent finding (2, 3, 4, 5, 6). The DAZ gene has an autosomal homolog, DAZL (DAZ-like), on chromosome 3p24. It is highly homologous to the DAZ gene, with 83% similarity in the coding region of the cDNA. Both genes encode RNA-binding proteins (7, 8, 9, 10). It is believed that the DAZ gene arose 40 million years ago, during primate evolution, from the transposition, repeat amplification, and pruning of an ancestral autosomal gene DAZL (7).
In addition to their presence in human beings, DAZ orthologs are present only on the Y chromosomes of great apes and Old World monkeys. Other mammals have only the autosomal DAZL gene (11, 12, 13, 14, 15). In many species, DAZL homologs are essential for the differentiation of germ cells. For example, the loss of Boule results in a meiotic arrest and azoospermia in Drosophila (16). A loss of germ cells and the absence of gamete production were observed in Dazl knockout mice. The spermatogenic defects of Boule flies could be partially rescued by the Xenopus Xdazl gene (14). Similarly, sterility of Dazl knockout mice was also partially rescued by the human DAZ gene (17). These facts indicate functional conservation of DAZ, Dazl, and Xdazl.
We have previously determined the expression patterns and transcript concentrations of DAZL in the human testes. We found that DAZL protein is expressed in different types of male germ cells and that the concentrations of DAZL transcripts were lower in men with spermatogenic failure (18). These findings suggest the important roles of the DAZL gene in human spermatogenesis. Another approach to investigate the role of DAZL is to detect mutations or polymorphisms in infertile men. To date, however, there are no reported instances of DAZL gene mutations in infertile men. In the present study, we have identified a single-nucleotide polymorphism (SNP) in exon 3 of the DAZL gene. This SNP is more prevalent in the group of patients with severe oligozoospermia and nonobstructive azoospermia. To the best of our knowledge, this is the first report on the association of SNP of an autosomal gene with susceptibility to severe spermatogenic failure.
Subjects and Methods
Subjects
From January 1997 to June 2000, we studied a total of 163 consecutive, unselected infertile men presenting with severe oligozoospermia or nonobstructive azoospermia. One hundred sixteen fertile men were enrolled as controls. All study and control subjects belonged to Han Chinese, the major ethnic group in Taiwan (making up more than 95% of the country’s population). They are distributed around five counties in Southern Taiwan: Yun-Lin, Chia-Yi, Tainan, Kaoshiung, and Ping-Tung. The control subjects were recruited from husbands of women who received regular prenatal care at the University Hospital. All of the control subjects had fathered at least 2 children without assisted reproductive technologies. The experimental design was in accord with the Helsinki Declaration of 1975 on human experimentation, and signed informed consent was obtained for all enrollees. All patients underwent comprehensive surveillance, including a detailed history taking, physical examination, at least 2 semen analyses, endocrinology profiles testing [LH, FSH, prolactin (PRL), and testosterone], karyotyping, and a molecular test for Y-chromosome microdeletions. Severe oligozoospermia was defined as sperm count less than 5 x 106/ml. In-patients with highly suspected nonobstructive azoospermia were advised to undergo bilateral testicular biopsies. Nonobstructive azoospermia was defined as: 1) spermatogenic defects in the testicular biopsy [such as hypospermatogenesis, maturation arrest, and Sertoli cell-only syndrome (SCO)]; or 2) elevated serum FSH level, total testicular volume less than 30 ml, and none of the other diagnoses applicable. Semen analysis was performed according to the standard methods outlined by the World Health Organization (1). Serum levels of FSH, LH, PRL, and testosterone were measured by using commercial RIA kits: Coat-A-Count FSH immunoradiometric assay (IRMA), Coat-A-Count LH IRMA, Coat-A-Count PRL IRMA, and IMMULITE Total Testosterone (Diagnostic Products, Los Angeles, CA). The intraassay and interassay precision coefficients of variation were 2.4% and 4% for FSH, 1.2% and 2.2% for LH, 1.9% and 2.4% for PRL, and 6.7% and 7.7% for testosterone, respectively. Chromosome analysis was performed using the G-banding by trypsin-Giemsa technique. Molecular analysis of Y-chromosome microdeletions included a combination of 24 sequence-tagged-site (STS)-based markers mapped to intervals 5 and 6 of Yq11 and 16 gene-based primers as described in our previous publications (19, 20, 21). All infertile patients and control subjects underwent a Y-chromosome deletion test.
Mutation screening by single-strand conformation polymorphism (SSCP)
Subjects with abnormal karyotypes and other recognizable causes of male infertility were excluded from screening. Genomic DNA was extracted from peripheral blood samples using a Puregene DNA isolation kit (Gentra, Minneapolis, MN). PCRs were performed in 20-µl vols containing 200 ng genomic DNA, 10 mM Tris-HCl (pH 8.3), 50 mM KCl, 0.1% Triton X-100, 200 µM deoxynucleotide triphosphates, 100 pmol of each primer, and 1 U Taq DNA polymerase (Promega Corp., Madison, WI). The primers and PCR conditions for different exons of DAZL gene are listed in Table 1
. PCR analyses were performed in an automated thermal cycler (OmniGene Thermal Cycler; Hybaid Ltd., Ashford Middlesex, UK). PCR products of exons 5–6 were restricted into 295- and 230-bp fragments by StuI for SSCP analyses (Table 1). The PCR products, with or without treatment by restriction enzymes, were mixed with an equal volume of formamide buffer (95% formamide, 10 mM EDTA, 0.1% bromophenol blue, 0.1% xylene cyanol). The mixtures were denatured for 5 min at 95 C and were then cooled rapidly on ice for 1 min. For each sample, 5-µl mixtures were subjected to SSCP analysis using GeneGel Excel gels as recommended by the manufacturer (Pharmacia Biotech, Uppsala, Sweden). Before analysis by SSCP, all PCR products had been sequenced to assure that there was no cross-amplification with DAZ. After SSCP analysis, the PCR products with aberrant band-shift were subjected to sequence analysis to identify mutations or polymorphisms. Sequence analysis was performed with an automatic sequencer (ABI 377; PE Applied Biosystems, Foster City, CA).
|
A mutation in exon 2 of the DAZL gene was digested with DdeI (BM Biochemica, Mannheim, Germany) and separated on a 2.5% agarose gel. A mutation in exon 3 was digested with AluI (BM Biochemica) and separated on a 12% polyacrylamide gel.
Confirmation of DAZL variants with testicular cDNA
The testicular tissue from patients was stored in liquid nitrogen using 2-methylbutane as a cryoprotectant until use. Before the isolation of total cellular RNA, each specimen was sliced into 10-µ-thick pieces. RT-PCR was performed according to methods described previously (18). In brief, total cellular RNA was extracted using standard methods (High Pure RNA Tissue Kit; Roche Molecular Biochemicals, Indianapolis, IN) and quantified by total absorbance at 260 nm. For the synthesis of cDNA, 12-µl aliquots of master mixture containing 2 µl RNA, 1 µl oligo(dT)12–18 primer (500 ng/µl; Life Technologies, Inc., Grand Island, NY), and 9 µl DEPC-treated water were heated to 70 C for 10 min and put on ice. RT-PCRs were performed in 20-µl aliquots containing master mixture, 4 µl 5x first-strand synthesis buffer, 0.1 M dithiothreitol, 10 mM of each deoxynucleotide triphosphate, and 200 U Superscript II RNase H- reverse transcriptase (Life Technologies, Inc.). The reverse transcriptase temperature profile was 42 C for 1 h, 75 C for 15 min, and final cooling to 4 C. The cDNA was aliquoted and stored at -20 C until use. Primers for the first round of PCR were 5'-CACGCCTCAGTCCGCCTGCGC-3' (nucleotides 1–21, sense) and 5'-TCAGACCAACAAAATTCTGAC-3' (nucleotides 1562–1582, antisense) (9) for amplification of the whole coding region of DAZL transcript. The PCR reactions were carried out at 94 C for 1 min, 55 C for 1 min, and 72 C for 1.5 min for 40 cycles, with a final extension at 72 C for 10 min. The PCR products were subjected to sequence analysis to identify mutations or polymorphisms. Sequence analysis was performed as previous described. For confirmation of T54A (Thr54Ala change) variant by the restriction enzyme, a second round of PCR was performed using products of the first round PCR as templates. Primers for nested PCR were 5'-TTCATCTTTGGCTCCTTTGAC-3' (nucleotides 91–111, sense) and 5'-CATATCTAGCAAAGAGGCTTC-3' (nucleotides 396–416, antisense) for DAZL 5' end fragment. The PCR reactions were carried out at 94 C for 1 min, 62 C for 1 min, and 72 C for 1 min for 40 cycles, with a final extension at 72 C for 10 min. The PCR products containing DAZL 5' end cDNA fragment were digested with AluI (BM Biochemica) and separated on an 8% polyacrylamide gel.
Statistical analysis
The allelic frequency was determined as the number of chromosomes harboring polymorphisms divided by the total number of chromosomes analyzed. Data were analyzed for statistical significance by a 
2 test. A P value less than 0.05 was considered statistically significant.
Results
Patient characteristics
Among the 163 patients, 21 showed abnormal karyotypes: 17 with 47,XXY; 1 with pericentric inversion of chromosome 11: 46,XY, inv (11)(p12q23.3); and 3 with gross structural rearrangements of the Y chromosome. All patients with gross karyotypic abnormalities were excluded. Among the 142 patients included in this study, 47 showed severe oligozoospermia, and 95 showed nonobstructive azoospermia.
SSCP and DNA sequencing analysis
Except for fragments containing exons 5 and 6, PCR products had been digested by restriction enzymes for SSCP analyses. The alteration in conformation was detected as a change in electrophoretic mobility in polyacrylamide gels. Of 11 exons examined, abnormal SSCP patterns were observed with exon 2 and exon 3 (Fig. 1). The exons with aberrant bands were sequenced to identify molecular lesions. Sequence analyses revealed an AG transition at nucleotide 260 in exon 2, and an AG transition at nucleotide 386 in exon 3 (Fig. 2).
|
|
The mutation in exon 2 leads to a Thr12Ala change (T12A) of the DAZL protein. The T12A variant creates a DdeI restriction site (CTNAG). On digestion, gel electrophoresis showed 67- and 197-bp fragments for the variant, instead of the 264-bp fragments for the wild-type allele (Fig. 3A). The mutation in exon 3 leads to a T54A of DAZL protein. The T54A variant creates an AluI restriction site (AGCT). After restriction enzyme digestion, gel electrophoresis showed 53-, 13-, and 115-bp fragments for the variant, instead of the 66- and 115-bp fragments for the wild-type allele (Fig. 3B).
|
Among 142 patients presenting with spermatogenic failure, 10 showed heterozygous T12A. The allelic frequency was 3.52% (10 of 284). The frequency of the T12A allele in the normal group was 2.59% (6 of 232). There was no difference in allelic frequency in T12A polymorphism between patients with spermatogenic failure and control subjects (P = 0.542).
T54A allele frequencies
Among 142 patients presenting with spermatogenic failure, 21 showed heterozygous T54A with an allele frequency of 7.39% (21 of 284). The frequency of the T54A allele was 0.86% (2 of 232) in the control group. There was a significant difference in the allelic frequency of T54A polymorphism between patients with spermatogenic failure and control subjects (P = 0.0003).
Lack of association between T12A and T54A alleles
Among 10 patients with T12A polymorphism, 3 patients (nos. 129, 161, and 171) also had T54A polymorphism. Among 6 control subjects with T12A polymorphism, no one had T54A polymorphism (P = 0.1366). Among 21 patients with T54A polymorphism, only 3 (nos. 129, 161, and 171) were found to have T12A polymorphism (Table 2). Among 2 control subjects with T54A polymorphism, no one had T12A polymorphism (P = 0.5665). Therefore, the T12A allele is not linked with T54A allele.
|
Sequence analysis of testicular cDNA from nine patients who were heterozygous for the T54A polymorphism in their genomic DNA (nos. 3, 10, 32, 35, 38, 40, 85, 97, and 161) showed the wild-type allele only, and there was absence of expected nucleotide substitution (386 AG transition at nucleotide 386) in exon 3 (Fig. 4A). There were no other mutations or polymorphisms detected in the coding region of DAZL using testicular cDNA. After restriction enzyme digestion by AluI for the DAZL 5' end cDNA fragment, the wild-type allele is expected to show 206- and 121-bp fragments instead of the 206-, 91-, and 30-bp fragments for the mutant allele. There are no 91- and 30-bp fragments in all of the patients’ samples (Fig. 4B), implying that T54A allele is hardly, if ever, expressed at the RNA level.
|
A summary of 21 infertile patients with T54A polymorphisms, Y-chromosome microdeletion status, and their corresponding testicular phenotypes are shown in Table 2
and Fig. 5. Briefly, none of control subjects carried Y-chromosomal deletions. Of the 21 patients with T54A polymorphism, testicular histopathologies were found in 9 patients. Their testicular phenotypes varied from hypospermatogenesis (2 patients) and maturation arrest (2 patients) to SCO (5 patients). No specific T54A variant and phenotype correlation could be addressed. Four patients showed microdeletions of one or more Y-specific genes: 3 (nos. 85, 97, and 165) had deletions confined to the azoospermia factor (AZF)c region, and 1 (no. 10) had deletion of the AZFa region. Of the 3 patients (nos. 85, 97, and 165) with both T54A polymorphism and DAZ gene deletions, only 2 (nos. 85 and 97) showed testicular histopathology (maturation arrest and hypospermatogenesis, respectively). It seems that a combination of DAZ gene deletion and T54A polymorphism did not worsen the phenotypic expression. Some of infertile men heterozygous for the T54A allele had higher FSH, LH, or PRL levels, and a lower level of testosterone (Table 2). However, the hormonal profiles did not differ significantly between infertile men, with or without T54A variant (data now shown).
|
Yen et al. (9) have described three other putative polymorphisms of the DAZL gene, of which the frequencies and significance in infertile men were not addressed. In the present study, we screened the entire coding sequences of DAZL gene, and two SNPs were identified. The frequencies of the two alleles were calculated for the Taiwanese population. The T12A polymorphism is most likely a true variant, given a high prevalence rate in normal fertile men. In contrast, T54A polymorphism in exon 3 is more prevalent in patients with spermatogenic failure. This polymorphism is located within the RNA recognition motif domain of the DAZL protein and will create a protein with substitution of threonine by alanine in the 54th amino acid.
Comparative analysis of 86-residue RNA recognition motif domain of human DAZL, human DAZ, and mouse Dazl reveals that human DAZL and mouse Dazl differ by only one amino acid substitution, whereas both differ from human Y-encoded DAZ at nine residues (7). Threonine in the 54th amino acid is conserved for human DAZL, DAZ, and mouse Dazl (Fig. 6) (8). It has been shown that RNA recognition motif domain of both DAZ and DAZL genes is associated with germ-cell-specific regulation of mRNA translation through binding to poly (A) RNA (22). The 54th amino acid of DAZL and DAZ is not in the RNP-1 and RNP-2 regions (8), but it is in the highly conserved region of DAZ family proteins, which may be the major determinants of RNA-binding specificity (23). Threonine in the 54th amino acid is conserved for both DAZ and DAZL genes and might be critical for the RNA-binding function (Fig. 6). We showed that the specific transcript is not detectable for the T54A allele in all infertile carriers with testicular tissues available. Presumably, T54A polymorphism creates a transcript with impaired stability, which, in turn, affects stability, editing, alternative polyA site selection, proper localization, or translational activation/repression of target RNAs (24, 25). Additional studies are required to investigate the mechanisms involving stability of the T54A transcript and the effect of this variant on proteins or RNAs interacting with DAZL.
|
Lilford et al. (30) suggested that up to 60% of undiagnosed male infertility arises from autosomal recessive mutations. DAZL seems to be an attractive candidate for autosomal recessive infertility. In the mice, the dosage effect of Dazl gene mutation on the testicular phenotype is obvious. Male mice lacking one allele of Dzal gene showed reduced sperm counts and a high level of abnormal sperm. Male mice with Dazl being completely knocked out showed almost an absence of germ cells (16). In our study, men heterozygous for the T54A polymorphism are susceptible to the development of spermatogenic failure, a finding consistent with the dosage effect observed in the transgenic mice model. The frequency of T54A was 0.86% and 7.39% in control subjects and infertile men, respectively. The expected frequency of T54A homozygote would be 1 in 13,521 and 1 in 183 in the control subjects and infertile men, respectively. It would be enlightening to observe the phenotype of subjects homozygous for the T54A polymorphism. It is possible that men homozygous for the T54A variant may not be compatible with reproduction, considering the absence of a specific variant in the infertile carriers.
Krausz et al. (31) have identified a Y-chromosome haplogroup associated with reduced sperm counts. During primate evolution, the DAZ gene cluster arose by transposing the autosomal gene on chromosome 3 to the Y, followed by amplification of the transposed unit (7, 32). Therefore, it is tempting to hypothesize that some haplotypes around the DAZL locus may predispose to spermatogenic defects or deletion formation of Y chromosome. In the present study, however, we only screened coding sequences of the DAZL gene. No attempts have been made to search haplotypes around the DAZL locus. Nor did we try to show the association between DAZL variants with deletion of DAZ gene cluster attributable to the small sample size of cases (only four) with Y deletions. Additional studies are required to confirm or deny the hypothesis.
Other genetic factors have been shown to be associated with impaired production of human sperm. These include HLA-haplotypes, mutations at the mitochondrial DNA polymerase locus, and a polymorphism of cytochrome P4501A1 (33, 34, 35). The association between short CAG repeat expansion in X-linked androgen receptor genes and the risk of impaired spermatogenesis remains uncertain (36). Indeed, the Online Mendelian Inheritance in Man database (http://www.ncbi.nlm.nih.gov/omin/) lists about 50 monogenic disorders associated with male infertility, all of which are always associated with a complex phenotypic expression other than male infertility. In the present study, we screened the polymorphisms out of the entire coding sequence of the DAZL gene and identified a SNP (T54A variant) located within the RNA recognition motif domain. We found an association between the T54A variant and a susceptibility to spermatogenic failure. To the best of our knowledge, the T54A variant of DAZL is the first SNP of autosomal genes associated with a susceptibility to severe spermatogenic failure. Our finding provides strong evidence for the role of the autosomal DAZL gene in human spermatogenesis.
Acknowledgments
We thank Bill Franke for revising the manuscript.
Footnotes
This work was supported by grants from the National Science Council of the Republic of China (NSC-90-2314-B-041-002, NSC 90-2314-B-006-164, and NSC-90-2314-B-006-168).
Abbreviations: AZF, Azoospermia factor; DAZ, deleted in azoospermia; DAZL, DAZ-like; PRL, prolactin; IRMA, immunoradiometric assay; SCO, Sertoli cell-only syndrome; SNP, single-nucleotide polymorphism; SSCP, single-strand conformation polymorphism; STS, sequence-tagged-site; T12A, Thr12Ala change; T54A, Thr54Ala change.
Received January 10, 2002.
Accepted July 23, 2002.
References
This article has been cited by other articles:
 |
|
 |
|
  A. Khattri, R. K. Pandey, N. J. Gupta, B. Chakravarty, M. Deenadayal, L. Singh, and K. Thangaraj APOB Gene Signal Peptide Deletion Polymorphism Is Not Associated With Infertility in Indian Men J Androl, November 1, 2009; 30(6): 734 - 738. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Khattri, R.K. Pandey, N.J. Gupta, B. Chakravarty, M. Deenadayal, L. Singh, and K. Thangaraj Estrogen receptor {beta} gene mutations in Indian infertile men Mol. Hum. Reprod., August 1, 2009; 15(8): 513 - 520. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Suryavathi, A. Khattri, K. Gopal, D. S. Rani, S. Panneerdoss, N. J. Gupta, B. Chakravarty, M. Deenadayal, L. Singh, and K. Thangaraj Novel Variants in UBE2B Gene and Idiopathic Male Infertility J Androl, September 1, 2008; 29(5): 564 - 571. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Reynolds, B. Collier, V. Bingham, N. K. Gray, and H. J. Cooke Translation of the synaptonemal complex component Sycp3 is enhanced in vivo by the germ cell specific regulator Dazl RNA, July 1, 2007; 13(7): 974 - 981. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. S. Cheng, P. L. Kuo, Y. N. Teng, T. Y. Kuo, C. L. Chung, Y. H. Lin, R. W. Liao, J. S. N. Lin, and Y. M. Lin Association of spermatogenic failure with decreased CDC25A expression in infertile men Hum. Reprod., September 1, 2006; 21(9): 2346 - 2352. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Guarducci, F. Nuti, L. Becherini, M. Rotondi, G. Balercia, G. Forti, and C. Krausz Estrogen receptor {alpha} promoter polymorphism: stronger estrogen action is coupled with lower sperm count Hum. Reprod., April 1, 2006; 21(4): 994 - 1001. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Ahda, J. Gromoll, A. Wunsch, K. Asatiani, M. Zitzmann, E. Nieschlag, and M. Simoni Follicle-Stimulating Hormone Receptor Gene Haplotype Distribution in Normozoospermic and Azoospermic Men J Androl, July 1, 2005; 26(4): 494 - 499. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X.-J. Yang, T. Shinka, S. Nozawa, H.-T. Yan, M. Yoshiike, M. Umeno, Y. Sato, G. Chen, T. Iwamoto, and Y. Nakahori Survey of the two polymorphisms in DAZL, an autosomal candidate for the azoospermic factor, in Japanese infertile men and implications for male infertility Mol. Hum. Reprod., July 1, 2005; 11(7): 513 - 515. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Cauffman, H. Van de Velde, I. Liebaers, and A. Van Steirteghem DAZL expression in human oocytes, preimplantation embryos and embryonic stem cells Mol. Hum. Reprod., June 1, 2005; 11(6): 405 - 411. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Tschanter, E. Kostova, C.M. Luetjens, T. G. Cooper, E. Nieschlag, and J. Gromoll No association of the A260G and A386G DAZL single nucleotide polymorphisms with male infertility in a Caucasian population Hum. Reprod., December 1, 2004; 19(12): 2771 - 2776. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Gianotten, M.P. Lombardi, A.H. Zwinderman, R. J. Lilford, and F. van der Veen Idiopathic impaired spermatogenesis: genetic epidemiology is unlikely to provide a short-cut to better understanding Hum. Reprod. Update, November 1, 2004; 10(6): 533 - 539. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Krausz, E. Guarducci, L. Becherini, S. degl'Innocenti, L. Gerace, G. Balercia, and G. Forti The Clinical Significance of the POLG Gene Polymorphism in Male Infertility J. Clin. Endocrinol. Metab., September 1, 2004; 89(9): 4292 - 4297. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Bartoloni, C. Cazzadore, A. Ferlin, A. Garolla, and C. Foresta Lack of the T54A polymorphism of the DAZL gene in infertile Italian patients Mol. Hum. Reprod., August 1, 2004; 10(8): 613 - 615. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. M. Luetjens, E. Y. Xu, R. A. Rejo Pera, A. Kamischke, E. Nieschlag, and J. Gromoll Association of Meiotic Arrest with Lack of BOULE Protein Expression in Infertile Men J. Clin. Endocrinol. Metab., April 1, 2004; 89(4): 1926 - 1933. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Kuhnert, J. Gromoll, E. Kostova, P. Tschanter, C.M. Luetjens, M. Simoni, and E. Nieschlag Case Report: Natural transmission of an AZFc Y-chromosomal microdeletion from father to his sons Hum. Reprod., April 1, 2004; 19(4): 886 - 888. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
