title: Superovulation induces defective methylation in line-1 retrotransposon elements in blastocyst.
abstract: BACKGROUND
  Series of epigenetic events happen during preimplantation development. Therefore assistant reproduction techniques (ART) have the potential to disrupt epigenetic regulation during embryo development. The purpose of this study was to investigate whether defects in methylation patterns in blastocyst due to superovulation originate from abnormal expression of Dnmts.
  
  
  METHODS
  Low- (6 IU) and high- (10 IU) dosage of PMSG was used to stimulate the female mice. The metaphase II(MII) oocytes, zygotes and blastocyst stage embryos were collected. Global methylation and methylation at H3K9 in zygote, and methylation at repeated sequence Line 1 and IAP in blastocysts were assayed. In addition, expression of Dnmts was examined in oocytes and zygotes.
  
  
  RESULTS
  Global DNA methylation and methylation at H3K9 in zygotes derived from females after low- or high-dosage hormone treatment were unaltered compared to that in controls. Moreover, DNA methylation at IAP in blastocysts was also unaffected, regardless of hormone dosage. In contrast, methylation at Line1 decreased when high-dose hormone was administered. Unexpectedly, expression of Dnmt3a, Dnmt3b, Dnmt3L as well as maintenance Dnmt1o in oocytes and zygotes was not disrupted.
  
  
  CONCLUSIONS
  The results suggest that defects in embryonic methylation patterns do not originate from the disruption of Dnmt expression.
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Cheongju 361-763, South Korea.
authors.forename: Xing-Wei
authors.initials: XW
authors.lastname: Liang
authors.forename: Xiang-Shun
authors.initials: XS
authors.lastname: Cui
authors.forename: Shao-Chen
authors.initials: SC
authors.lastname: Sun
authors.forename: Yong-Xun
authors.initials: YX
authors.lastname: Jin
authors.forename: Young Tae
authors.initials: YT
authors.lastname: Heo
authors.forename: Suk
authors.initials: S
authors.lastname: Namgoong
authors.forename: Nam-Hyung
authors.initials: NH
authors.lastname: Kim
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006064:Gonadotropins, Equine / Q000494:pharmacology; D006657:Histones / Q000378:metabolism; D006736:Horses; D006801:Humans; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D008297:Male; D008745:Methylation; D051379:Mice; D008813:Mice, Inbred ICR; D010053:Ovary / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013480:Superovulation; D000097584:DNA Methyltransferase 3B
chemical_list: D006063:Chorionic Gonadotropin; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D006064:Gonadotropins, Equine; D006657:Histones; D000097584:DNA Methyltransferase 3B; C000717967:DNMT3A protein, human; C000715535:Dnmt3a protein, mouse; C498796:Dnmt3l protein, mouse; C000619381:Dnmt1 protein, mouse