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- Title
Limited demethylation leaves mosaic-type methylation states in cloned bovine pre-implantation embryos.
- Authors
Vong-Kook Kang; Jung Sun Park; Deog-Bon Koo; Voung-Hee Choi; Sun-Uk Kim; Kyung-Kwang Lee; Yong-Mahn Han
- Abstract
Cloning by nuclear transfer (NT) has been riddled with difficulties: most clones die before birth and survivors frequently display growth abnormalities. The cross-species similarity in abnormalities observed in cloned fetuses/animals leads us to suspect the fidelity of epigenetic reprogramming of the donor genome. Here, we found that single-copy sequences, unlike satellite sequences, are demethylated in pre-implantation NT embryos. The differential demethylation pattern between genomic sequences was confirmed by analyzing single blastocysts. It suggests selective demethylation of other developmentally important genes in NT embryos. We also observed a reverse relationship between methylation levels and inner cell mass versus trophectoderm (ICM/TE) ratios, which was found to be a result of another type of differential demethyla- tion occurring in NT biastocysts where unequal methylation was maintained between 1CM and TE regions. TE-tocalized methylation aberrancy suggests a widespread gene dysregulation in an extra-embryonic region, thereby resulting in placental dysfunction familiar to cloned fetuses/animals. These differential demethylations among genomic sequences and between differently allocated cells produce varied overall, but specified, methylation patterns, demonstrating that epigenetic reprogramming occurs in a limited fashion in NT embryos.
- Subjects
ALKYLATION; GENETICS; FETUS; MOSAICISM; METHYLATION; EMBRYOS
- Publication
EMBO Journal, 2002, Vol 21, Issue 5, p1092
- ISSN
0261-4189
- Publication type
Article
- DOI
10.1093/emboj/21.5.1092