An epigenetic aberration increased in intergenic regions of cloned mice.

The causes of frequent abnormal phenotypes and low success rate in mammalian cloning are poorly understood. Although epigenetic aberration is suspected to be a cause, its connection to the phenotypes has yet to be investigated. To measure the level of reprogramming of an epigenetic mark, acetylation at lysine 9 of histone H3 (H3K9Ac), in cloned mice, we examined its conservation between two cloned mice derived from distinct cell nuclei and their natural donors by utilizing whole-genome tiling arrays and quantitative PCR. Pairwise comparison of the H3K9Ac enrichment profile between the four mice revealed that H3K9Ac is less conserved in intergenic regions than in promoter regions of protein-coding genes. Intriguingly, the variation of H3K9Ac enrichment in intergenic regions is the most prominent in comparison of the two clones, possibly reflecting an additive effect of aberrant reprogramming of this epigenetic information occurring specifically in each of the two clones.