Segregation of genomic sequence variations and contribution to loss of diploid and haploid germ cells
Final Report Abstract
Male infertility is a clinically and genetically highly heterogeneous disease, which in most cases is clinically noted as oligo(asthenoterato)zoospermia (OAT) or azoospermia (AZ). The major aim of this project was to apply the novel genetic technologies of genome-wide analyses to detect novel causes of spermatogenic failure. All subjects were selected from patients attending the collaborating Centre of Reproductive Medicine and Andrology (CeRA), Münster. High-resolution genome-wide array-CGH was carried out on 135 patient with spermatogenetic failure and 100 controls with normozoospermia. A negative correlation between total sperm count and number of deletions was found and sex-chromosomal Copy number variations (CNVs) were significantly overrepresented in patients with Sertoli-cell-only syndrome (SCOS) and meiotic arrest (MA) compared with controls. Detecting the segregation of CNVs was limited due to the low response rate of affected men, who in the majority do not want to inform their parents of their infertility. Next, a specifically designed and even higher resolution array-CGH targeting the X-chromosome was performed in collaboration with colleagues from Pittsburgh. This lead to the identification of TEX11 as a novel candidate gene and common cause for spermatogenic failure due to MA. By analysing large numbers of 289 men with AZ and 384 controls we found pathogenic deletions and nucleotide mutations in 10-20% of patients with MA, 1% of men with testicular mixed atrophy, none in SCOS patients, and none in controls. We showed that the TEX11 protein is specifically expressed in germ cells in the human comparable to the mouse model. Two other candidate genes were analysed in our patients and controls: NR5A1 encoding Steroidogenic Factor 1 (SF1) and DMRT1 encoding a transcription factor that has been demonstrated to play a pivotal role in testis development. Pathogenic mutations were found in both genes in about 1% and 4%, respectively. In contrast, the sequencing of six other candidate genes did so far not lead to identification of convincingly pathogenic mutations. Exome sequencing in highly selected men with the most severe and concise phenotypes of complete, bilateral SCOS or MA resulted in identification of one highly interesting candidate gene for each phenotype. Because for neither gene an association with spermatogenic failure had been described before, a number of functional analyses are on their way to elucidate their function. By analyses in patients with oligozoospermia and normozoospermia, we detected associations between aberrant methylation at specific loci and reduced semen quality. These epigenetic aberrations may be used as prospective markers in infertile males in the future. In conclusion, we identified or confirmed associations between variants in three genes and spermatogenic failure. While clinical routine screening of TEX11 in men with AZ and especially MA is warranted because of the high prevalence of clearly pathogenic mutations, routine analyses of NR5A1 and DMRT1 in unselected infertile men remains debatable. Epigenetic alterations may well play an important role in the future routine andrological workup of the infertile male.
Publications
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(2011) Clinical experience with azoospermia: aetiology and chances for spermatozoa detection upon biopsy. Int J Androl 34:291-298
Tüttelmann F, Werny F, Cooper TG, Kliesch S, Simoni M, Nieschlag E
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(2011) Copy number variants in patients with severe oligozoospermia and Sertoli-cell-only syndrome. PLoS One 6:e19426
Tüttelmann F, Simoni M, Kliesch S, Ledig S, Dworniczak B, Wieacker P, Röpke A
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(2011) Genetic aspects of disorders of spermatogenesis. [Genetische Aspekte bei Spermatogenesestörungen] Medizinische Genetik 23,259-266
Tüttelmann F
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(2012) Combined Effects of the Variants FSHB -211G>T and FSHR 2039A>G on Male Reproductive Parameters. J Clin Endocrinol Metab 97:3639-47
Tüttelmann F, Laan M, Grigorova M, Punab M, Sõber S, Gromoll J
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(2013) Comprehensive sequence analysis of the NR5A1 gene encoding Steroidogenic Factor 1 in a large group of infertile males. Eur J Hum Genet 21:1012-5
Röpke A, Tewes AC, Gromoll J, Kliesch S, Wieacker P, Tüttelmann F
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(2013) DNA methylation in spermatozoa as a prospective marker in andrology. Andrology 1:731-40
Kläver R, Tüttelmann F, Bleiziffer A, Haaf T, Kliesch S, Gromoll J
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(2013) Mosaicism for an unbalanced Y;21 translocation in an infertile 5 man: a case report. J Assist Reprod Genet 30:1553-8
Röpke A, Stratis Y, Dossow-Scheele D, Wieacker P, Kliesch S, Tüttelmann F
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(2014) DMRT1 mutations are rarely associated with male infertility. Fertil Steril 102:816-820.e3
Tewes AC, Ledig S, Tüttelmann F, Kliesch S, Wieacker P
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Epigenetic regulation of the RHOX homeobox gene cluster and its association with human male infertility (2014) Hum Mol Genet 23:12-23
Richardson ME, Bleiziffer A, Tüttelmann F, Gromoll J, Wilkinson MF
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(2015) X-Linked TEX11 Mutations, Meiotic Arrest, and Azoospermia in Infertile Men. N Engl J Med 372:2097-107
Yatsenko AN, Georgiadis AP, Röpke A, Berman AJ, Jaffe T, Olszewska M, Westernströer B, Sanfilippo J, Kurpisz M, Rajkovic A, Yatsenko SA, Kliesch S, Schlatt S, Tüttelmann F
