title: Tissue-specific elevated genomic cytosine methylation levels are associated with an overgrowth phenotype of bovine fetuses derived by in vitro techniques.
abstract: Epigenetic perturbations are assumed to be responsible for abnormalities observed in fetuses and offspring derived by in vitro techniques. We have designed an experiment with bovine Day 80 fetuses generated by somatic cell nuclear transfer (SCNT), in vitro fertilization (IVF), and artificial insemination (AI) to determine the relationship between fetal phenotype and genome-wide 5-methylcytosine (5mC) content. When compared with AI controls, SCNT and IVF fetuses displayed significantly increased body weight (61% and 28%), liver weight (100% and 36%), and thorax circumference (20% and 11%). A reduced crown-rump length:thorax circumference ratio (1.175 +/- 0.017 in SCNT and 1.292 +/- 0.018 in IVF vs. 1.390 +/- 0.018 in AI, P < 0.001 and P < 0.002) was the external hallmark of this disproportionate overgrowth phenotype. The SCNT fetuses showed significant hypermethylation of liver DNA in comparison with AI controls (3.46% +/- 0.08% vs. 3.17% +/- 0.09% 5mC, P < 0.03), and the cytosine methylation levels for IVF fetuses (3.34% +/- 0.09%) were, as observed for phenotypic parameters, intermediate to the other groups. Regressions of fetal body and liver weight and thorax circumference on 5mC content of liver DNA were positive (P < 0.073-0.079). Furthermore, a significant negative regression (P < 0.021) of the crown-rump length:thorax circumference ratio on liver 5mC was observed. The 5mC content of placental cotyledon DNA was 46% lower than in liver DNA (P < 0.0001) but did not differ among groups. These data are in striking contrast with the recently reported hypomethylation of DNA from SCNT fetuses and indicate that hypermethylation of fetal tissue, but not placenta, is linked to the overgrowth phenotype in bovine SCNT and IVF fetuses.
authors.affiliation: Department of Molecular Animal Breeding and Biotechnology, Gene Center of the Ludwig-Maximilian University, D-1377 Munich, Germany. S.Hiendleder@gen.vetmed.uni-muenchen.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Hiendleder
authors.forename: Cora
authors.initials: C
authors.lastname: Mund
authors.forename: Horst-Dieter
authors.initials: HD
authors.lastname: Reichenbach
authors.forename: Hendrik
authors.initials: H
authors.lastname: Wenigerkind
authors.forename: Gottfried
authors.initials: G
authors.lastname: Brem
authors.forename: Valeri
authors.initials: V
authors.lastname: Zakhartchenko
authors.forename: Frank
authors.initials: F
authors.lastname: Lyko
authors.forename: Eckhard
authors.initials: E
authors.lastname: Wolf
mesh_terms: D044503:5-Methylcytosine / Q000378:metabolism; D000818:Animals; D002417:Cattle / Q000196:embryology*; D003596:Cytosine / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D005321:Extraembryonic Membranes / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro; D047109:Fetal Development / Q000235:genetics; D005333:Fetus / Q000378:metabolism; D016678:Genome; D007315:Insemination, Artificial; D008099:Liver / Q000196:embryology; D008745:Methylation; D053652:Nuclear Transfer Techniques; D010641:Phenotype
chemical_list: D044503:5-Methylcytosine; D003596:Cytosine; D004247:DNA