Delayed and incomplete reprogramming of chromosome methylation patterns in bovine cloned embryos

摘要: Full-term development has now been achieved in several mammalian species by transfer of somatic nuclei into enucleated oocytes [1, 2]. Although a high proportion such reconstructed embryos can evolve until the blastocyst stage, only few percent develop live offspring, which often exhibit developmental abnormalities [3, 4]. Regulatory epigenetic markers as DNA methylation are imposed on embryonic cells normal proceeds, creating differentiated cell states. Cloned require erasure their so to regain totipotent state [5]. Here we report differences dynamics chromosome between cloned and bovine before implantation. We show that fail reproduce distinguishable parental-chromosome patterns after fusion maintain pattern during subsequent stages, mainly highly reduced efficiency passive demethylation process. Surprisingly, chromosomes appear constantly undermethylated euchromatin morulae blastocysts, while centromeric heterochromatin remains more methylated than embryos. propose abnormal time-dependent events spanning preimplantation clones may significantly interfere with reprogramming, contributing incidence physiological anomalies occurring later pregnancy or clone birth.