title: Epigenetic germline mosaicism in infertile men.
abstract: Imprinted genes are expressed either from the paternal or the maternal allele, because the other allele has been silenced in the mother's or father's germline. Imprints are characterized by DNA methylation at cytosine phosphate guanine sites. Recently, abnormal sperm parameters and male infertility have been linked to aberrant methylation patterns of imprinted genes in sperm DNA. However, these studies did not account for possible epigenetic heterogeneity in sperm. We have investigated whether spermatozoa are a homogeneous cell population regarding DNA methylation of imprinted genes. Swim-up sperm was obtained from 45 men with normal (n = 19) and abnormal (n = 26) sperm parameters. DNA methylation of the imprinted gene KCNQ1OT1 was measured in multiple pools of 10 spermatozoa by a highly sensitive pyrosequencing-based oligo-sperm methylation assay (OSMA). DNA methylation of four imprinted genes (KCNQ1OT1, MEST, H19 and MEG3) was further analysed by deep bisulfite sequencing, which allows analysis at the single-cell level. Using OSMA, we found a significantly increased variation in the DNA methylation values of the maternally methylated gene KCNQ1OT1 in samples with abnormal sperm parameters. DBS showed that normozoospermic samples had a homogenous pattern of DNA methylation, whereas oligoasthenozoospermic samples contained discrete populations of spermatozoa with either normal or abnormal methylation patterns. Aberrant methylation of H19 appears to occur preferentially on the maternally inherited allele. Our results demonstrate the presence of epigenetic mosaicism in the semen of oligoasthenozoospermic men, which probably results from errors in imprint erasure.
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Muenster, 48149 Muenster, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Laurentino
authors.affiliation: Institute of Human Genetics, University of Duisburg-Essen, 45122 Essen, Germany.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Beygo
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Muenster, 48149 Muenster, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Nordhoff
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Muenster, 48149 Muenster, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Kliesch
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Muenster, 48149 Muenster, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Wistuba
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Muenster, 48149 Muenster, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Borgmann
authors.affiliation: Institute of Human Genetics, University of Duisburg-Essen, 45122 Essen, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Buiting
authors.affiliation: Institute of Human Genetics, University of Duisburg-Essen, 45122 Essen, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Horsthemke
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Muenster, 48149 Muenster, Germany joerg.gromoll@ukmuenster.de.
authors.forename: Jörg
authors.initials: J
authors.lastname: Gromoll
mesh_terms: D000328:Adult; D000483:Alleles; D003596:Cytosine / Q000378:metabolism; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D057890:Epigenomics; D018392:Genomic Imprinting; D018095:Germ-Line Mutation; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007248:Infertility, Male / Q000235:genetics*; D008297:Male; D009030:Mosaicism; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D013094:Spermatozoa / Q000473:pathology*; D013447:Sulfites / Q000378:metabolism
chemical_list: C485621:KCNQ1OT1 long non-coding RNA, human; D024642:Potassium Channels, Voltage-Gated; D011506:Proteins; D013447:Sulfites; C103637:mesoderm specific transcript protein; D003596:Cytosine; C042345:hydrogen sulfite