Quantification of leukocyte genomic 5-methylcytosine levels reveals epigenetic plasticity in healthy adult cloned cattle
2010
De Montera , Beatrice (INRA , Jouy-En-Josas (France). UMR 1198 Biologie du Développement et Reproduction) | El Zeihery , Dalia (University of Wuppertal, Wuppertal(Allemagne). Department of Analytical Chemistry) | Müller , Sigrid (Ludwig-Maximilians-Universität München, Munich(Allemagne). Chair for Molecular Animal Breeding and Biotechnology, and Laboratory for Functional Genome Analysis (LAFUGA), Gene Center) | Jammes , Helene (INRA , Jouy-En-Josas (France). UMR 1198 Biologie du Développement et Reproduction) | Brem , Gottfried (University of Veterinary Sciences, Vienne(Autriche). Institute of Animal Breeding and Genetics) | Reichenbach , Horst-Dieter (Bayerische Landesanstalt für Landwirtschaft, Poing/Grub(Allemagne).) | Scheipl , Fabian (Ludwig-Maximilians-Universität München, Munich(Allemagne). STABLAB) | Chavatte-Palmer , Pascale (INRA , Jouy-En-Josas (France). UMR 1198 Biologie du Développement et Reproduction) | Zakhartchenko , Valeri (Ludwig-Maximilians-Universität München, Munich(Allemagne). Chair for Molecular Animal Breeding and Biotechnology, and Laboratory for Functional Genome Analysis (LAFUGA), Gene Center) | Schmitz , Oliver J. (University of Wuppertal, Wuppertal(Allemagne). Department of Analytical Chemistry) | Wolf , Eckhard (Ludwig-Maximilians-Universität München, Munich(Allemagne). Chair for Molecular Animal Breeding and Biotechnology, and Laboratory for Functional Genome Analysis (LAFUGA), Gene Center) | Renard , Jean Paul (INRA , Jouy-En-Josas (France). UMR 1198 Biologie du Développement et Reproduction) | Hiendleder , Stefan (Ludwig-Maximilians-Universität MünchenUniversity of Adelaide, MunichAdelaide(Allemagne). Chair for Molecular Animal Breeding and Biotechnology, and Laboratory for Functional Genome Analysis (LAFUGA), Gene CenterSchool of Agriculture, Food & Wine, JS Davies Epigenetics and Genetics Group, Animal Science / Robinson Institute, Research Centre for Reproductive Health)
Successful somatic cell nuclear transfer (SCNT) requires epigenetic reprogramming of a differentiated donor cell nucleus. Incorrect reprogramming of epigenetic markings such as DNA methylation is associated with compromised prenatal development and postnatal abnormalities. Clones that survive into adulthood, in contrast, are assumed to possess a normalized epigenome corresponding to their normal phenotype. To address this point, we used capillary electrophoresis to measure 5-methylcytosine (5mC) levels in leukocyte DNA of 38 healthy female bovine clones that represented five genotypes from the Simmental breed and four genotypes from the Holstein breed. The estimated variance in 5mC level within clone genotypes of both breeds [0.104, 95% confidence interval (CI): 0.070–0.168] was higher than between clone genotypes (0, CI: 0–0.047). We quantified the contribution of SCNT to this unexpected variability by comparing the 19 Simmental clones with 12 female Simmental monozygotic twin pairs of similar age. In Simmental clones, the estimated variability within genotype (0.0636, CI: 0.0358–0.127) was clearly higher than in twin pairs (0.0091, CI: 0.0047–0.0229). In clones, variability within genotype (0.0636) was again higher than between genotypes (0, CI: 0–0.077). Twins, in contrast, showed lower variability within genotypes (0.0091) than between genotypes (0.0136, CI: 0.00250–0.0428). Importantly, the absolute deviations of 5mC values of individual SCNT clones from their genotype means were fivefold increased in comparison to twins. Further comparisons with noncloned controls revealed DNA hypermethylation in most of the clones. The clone-specific variability in DNA methylation and DNA hypermethylation clearly show that healthy adult SCNT clones must be considered as epigenome variants.
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