title: Aberrant methylation of multiple imprinted genes in embryos of tamoxifen-treated male rats.
abstract: Genomic imprinting is an epigenetic phenomenon known to regulate fetal growth and development. Studies from our laboratory have demonstrated that treatment of adult male rats with tamoxifen increased postimplantation loss around mid gestation. Further studies demonstrated the aberrant expression of transcripts of several imprinted genes in the resorbing embryos at days 11 and 13 of gestation including IGF2. In addition, decreased methylation at the Igf2-H19 imprint control region was observed in spermatozoa and in resorbing embryos sired by tamoxifen-treated males. In this study, methylation analysis of the imprinted genes, which were found to be differentially expressed, was done using EpiTYPER in the spermatozoa of tamoxifen-treated rats and in postimplantation embryos sired by tamoxifen-treated rats. Differentially methylated regions (DMRs) for most imprinted genes have not been identified in the rats. Hence, initial experiments were performed to identify the putative DMRs in the genes selected for the study. Increased methylation at CpG islands present in the putative DMRs of a number of imprinted genes was observed in the resorbing embryos sired by tamoxifen-treated male rats. This increase in methylation is associated with the downregulation of most of these genes at the transcript level in resorbing embryos. No change in the methylation status of these genes was observed in spermatozoa. These observations suggest that a deregulation of mechanisms protecting unmethylated alleles from a wave of de novo methylation occurs following implantation.
authors.affiliation: Neuroendocrinology Division, National Institute for Research in Reproductive Health (ICMR), Parel, Mumbai 400 012, India.
authors.forename: Neelam A
authors.initials: NA
authors.lastname: Kedia-Mokashi
authors.forename: Leena
authors.initials: L
authors.lastname: Kadam
authors.forename: Mandar
authors.initials: M
authors.lastname: Ankolkar
authors.forename: Kushaan
authors.initials: K
authors.lastname: Dumasia
authors.forename: N H
authors.initials: NH
authors.lastname: Balasinor
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins; D018899:CpG Islands / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects; D020964:Embryo Loss / Q000139:chemically induced / Q000378:metabolism; D004622:Embryo, Mammalian / Q000187:drug effects* / Q000378:metabolism; D047108:Embryonic Development / Q000187:drug effects*; D005260:Female; D018392:Genomic Imprinting / Q000187:drug effects*; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D018812:Paternal Exposure / Q000009:adverse effects*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D020845:Selective Estrogen Receptor Modulators / Q000009:adverse effects*; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism; D013629:Tamoxifen / Q000009:adverse effects; D015854:Up-Regulation / Q000187:drug effects; D020666:ras-GRF1 / Q000235:genetics / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; C512925:Dlk1 protein, mouse; C513121:IGF2 protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; C513037:Rasgrf1 protein, mouse; D020845:Selective Estrogen Receptor Modulators; D020666:ras-GRF1; D013629:Tamoxifen; D007335:Insulin-Like Growth Factor II