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SYCP3 mutations are uncommon in patients with azoospermia
CORRESPONDENCE SYCP3 mutations are uncommon in patients with azoospermia Mutation analysis of the SYCP3 gene was performed for 58 patients with a maturation arrest of spermatogenesis. In contrast to the previously reported high frequency of mutations, only polymorphisms were found in the present study. (Fertil Steril威 2005;84:1019 –20. ©2005 by American Society for Reproductive Medicine.)
What caught our interest was a report describing mutations in the SYCP3 gene (1). Knock-out mice showed that SYCP3 is involved in homologous pairing of chromosomes and causes meiotic arrest when absent (2– 4). In humans, a high frequency of mutations (10.5%) in SYCP3 has been described in men with a maturation arrest (1). In the present study, we screened patients with a maturation arrest of spermatogenesis presenting at our fertility center for mutations in SYCP3. In total, 58 patients were analyzed, including 22 patients for whom a few spermatozoa could be found in testicular tissue. Eight patients with a deletion on the long arm of the Y chromosome were also included. The histology of testicular tissues of these patients varied a great deal and additional mutations in non-Y chromosomal genes can therefore not be excluded. For the screening procedure, seven polymerase chain reactions (PCR) were set up, after which the fragments were sequenced with primers used for amplification on an automated ABI310 Genetic Analyser (Applied Biosystems, Nieuwerkerk a/d Ijssel, The Netherlands). All primers sequences for the PCR reaction were described previously (1). The following primer combinations were used: SYCP3EF1-2/SYCP3ER1-1, SYCP3EF2-2/SYCP3ER3-2, SYCP3EF3-1/SYCP3ER4-1, SYCP3EF5-2/SYCP3ER6-1, SYCP3EF6-1/SYCP3ER8-1, and SYCP3EF4-2/SYCP3ER5-2. The latter PCR was followed by a nested PCR with SYCP3EF41/SYCP3ER5-1. The sequence of SYCP3 from GenBank (AF492003) was used as the reference sequence and the A of the ATG of the translation signal was numbered ⫹1. Through sequencing of the SYCP3 gene, we detected two variants. Received January 25, 2005; revised and accepted April 18, 2005. Supported by grants from the Fund for Scientific Research (FWOVlaanderen), and from the Research Council and a Concerted Action of the Free University of Brussels (Vrije Universiteit Brussel). Reprint requests: Katrien Stouffs, Ph.D., Research Center for Reproduction and Genetics, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium (FAX: 003224776860; E-mail: katrien. [email protected]).
0015-0282/05/$30.00 doi:10.1016/j.fertnstert.2005.04.033
One patient was heterozygous for c.435A ¡ G, but as the corresponding amino acid remains unchanged, this variant probably represents a polymorphism. Another patient was heterozygous for c.754A ¡ G located after the stop codon. As a consequence, no mutations of SYCP3 were found in the patients we had analyzed. These results are in contrast with those described previously, where 2 of 19 patients were heterozygous for the same deletion (1). Our data indicate that more research is necessary to prove the involvement of SYCP3 in the etiology of male factor infertility. In our examined patient group, patients with a complete as well as an incomplete maturation arrest were included, as it cannot be excluded that some spermatocytes are able to complete meiosis. The exact impact of the described alteration on the completion of meiosis is still unknown. It has been shown that the mutated SYCP3 protein has little protein–protein interaction. Moreover, this truncated SYCP3 protein also interferes with the formation of normal protein fibers. Therefore, a dominant negative interference pattern was suggested (1). Alternatively, the level of normal proteins might be too low to trigger normal homologous pairing of chromosomes and prevent spermatocytes from going into apoptosis. Katrien Stouffs, Ph.D. Willy Lissens, Ph.D. Herman Tournaye, M.D., Ph.D. André Van Steirteghem, M.D., Ph.D. Inge Liebaers, M.D., Ph.D. Research Center for Reproduction and Genetics, Vrije Universiteit Brussel, Laarbeeklaan, Brussels, Belgium
REFERENCES 1. Miyamoto T, Hasuike S, Yogev L, Maduro MR, Ishikawa M, Westphal H, et al. Azoospermia in patients heterozygous for a mutation in SYCP3. Lancet 2003;362:1714 –9.
Fertility and Sterility姞 Vol. 84, No. 4, October 2005 Copyright ©2005 American Society for Reproductive Medicine, Published by Elsevier Inc.
1019
2. Botelho RJ, DiNicolo L, Tsao N, Karaiskakis A, Tarsounas M, Moens PB, et al. The genomic structure of SYCP3, a meiosis-specific gene encoding a protein of the chromosome core. Biochim Biophys Acta 2001;1518:294 –9. 3. Kolas NK, Yuan L, Hoog C, Heng HH, Marcon E, Moens PB. Male mouse meiotic chromosome cores deficient in structural proteins
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Stouffs et al.
Correspondence
SYCP3 and SYCP2 align by homology but fail to synapse and have possible impaired specificity of chromatin loop attachment. Cytogenet Genome Res 2004;105:182– 8. 4. Yuan L, Liu JG, Hoja MR, Wilbertz J, Nordqvist K, Hoog C. Female germ cell aneuploidy and embryo death in mice lacking the meiosisspecific protein SYCP3. Science 2002;296:1115– 8.
Vol. 84, No. 4, October 2005
What caught our interest was a report describing mutations in the SYCP3 gene (1). Knock-out mice showed that SYCP3 is involved in homologous pairing of chromosomes and causes meiotic arrest when absent (2– 4). In humans, a high frequency of mutations (10.5%) in SYCP3 has been described in men with a maturation arrest (1). In the present study, we screened patients with a maturation arrest of spermatogenesis presenting at our fertility center for mutations in SYCP3. In total, 58 patients were analyzed, including 22 patients for whom a few spermatozoa could be found in testicular tissue. Eight patients with a deletion on the long arm of the Y chromosome were also included. The histology of testicular tissues of these patients varied a great deal and additional mutations in non-Y chromosomal genes can therefore not be excluded. For the screening procedure, seven polymerase chain reactions (PCR) were set up, after which the fragments were sequenced with primers used for amplification on an automated ABI310 Genetic Analyser (Applied Biosystems, Nieuwerkerk a/d Ijssel, The Netherlands). All primers sequences for the PCR reaction were described previously (1). The following primer combinations were used: SYCP3EF1-2/SYCP3ER1-1, SYCP3EF2-2/SYCP3ER3-2, SYCP3EF3-1/SYCP3ER4-1, SYCP3EF5-2/SYCP3ER6-1, SYCP3EF6-1/SYCP3ER8-1, and SYCP3EF4-2/SYCP3ER5-2. The latter PCR was followed by a nested PCR with SYCP3EF41/SYCP3ER5-1. The sequence of SYCP3 from GenBank (AF492003) was used as the reference sequence and the A of the ATG of the translation signal was numbered ⫹1. Through sequencing of the SYCP3 gene, we detected two variants. Received January 25, 2005; revised and accepted April 18, 2005. Supported by grants from the Fund for Scientific Research (FWOVlaanderen), and from the Research Council and a Concerted Action of the Free University of Brussels (Vrije Universiteit Brussel). Reprint requests: Katrien Stouffs, Ph.D., Research Center for Reproduction and Genetics, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium (FAX: 003224776860; E-mail: katrien. [email protected]).
0015-0282/05/$30.00 doi:10.1016/j.fertnstert.2005.04.033
One patient was heterozygous for c.435A ¡ G, but as the corresponding amino acid remains unchanged, this variant probably represents a polymorphism. Another patient was heterozygous for c.754A ¡ G located after the stop codon. As a consequence, no mutations of SYCP3 were found in the patients we had analyzed. These results are in contrast with those described previously, where 2 of 19 patients were heterozygous for the same deletion (1). Our data indicate that more research is necessary to prove the involvement of SYCP3 in the etiology of male factor infertility. In our examined patient group, patients with a complete as well as an incomplete maturation arrest were included, as it cannot be excluded that some spermatocytes are able to complete meiosis. The exact impact of the described alteration on the completion of meiosis is still unknown. It has been shown that the mutated SYCP3 protein has little protein–protein interaction. Moreover, this truncated SYCP3 protein also interferes with the formation of normal protein fibers. Therefore, a dominant negative interference pattern was suggested (1). Alternatively, the level of normal proteins might be too low to trigger normal homologous pairing of chromosomes and prevent spermatocytes from going into apoptosis. Katrien Stouffs, Ph.D. Willy Lissens, Ph.D. Herman Tournaye, M.D., Ph.D. André Van Steirteghem, M.D., Ph.D. Inge Liebaers, M.D., Ph.D. Research Center for Reproduction and Genetics, Vrije Universiteit Brussel, Laarbeeklaan, Brussels, Belgium
REFERENCES 1. Miyamoto T, Hasuike S, Yogev L, Maduro MR, Ishikawa M, Westphal H, et al. Azoospermia in patients heterozygous for a mutation in SYCP3. Lancet 2003;362:1714 –9.
Fertility and Sterility姞 Vol. 84, No. 4, October 2005 Copyright ©2005 American Society for Reproductive Medicine, Published by Elsevier Inc.
1019
2. Botelho RJ, DiNicolo L, Tsao N, Karaiskakis A, Tarsounas M, Moens PB, et al. The genomic structure of SYCP3, a meiosis-specific gene encoding a protein of the chromosome core. Biochim Biophys Acta 2001;1518:294 –9. 3. Kolas NK, Yuan L, Hoog C, Heng HH, Marcon E, Moens PB. Male mouse meiotic chromosome cores deficient in structural proteins
1020
Stouffs et al.
Correspondence
SYCP3 and SYCP2 align by homology but fail to synapse and have possible impaired specificity of chromatin loop attachment. Cytogenet Genome Res 2004;105:182– 8. 4. Yuan L, Liu JG, Hoja MR, Wilbertz J, Nordqvist K, Hoog C. Female germ cell aneuploidy and embryo death in mice lacking the meiosisspecific protein SYCP3. Science 2002;296:1115– 8.
Vol. 84, No. 4, October 2005