Epigenetic reprogramming in cloned livestock

The objective of this research is to examine epigenetic reprogramming in somatic cell nuclear transfer (SCNT) livestock, particularly cattle, from early embryonic through adult stages, mainly using imprinted genes as an indication of fidelity. In this study several imprinted genes were investigated, such as IGF2, IGF2R and H19. Major differences were found in the regulation of the bovine IGF2 in nearly all aspects of age-, tissue-, promoter- and allele specific expression of IGF2 as well as the promoter specific loss of imprinting from every other species studied, including cattle\u27s close relatives, the sheep and pig [1]. ^ The allelic expression of IGF2R was investigated using a G/A transition in the 3\u27UTR of IGF2R in cloned cattle. Here we report a variable pattern of IGF2R allelic expression in major organs. We also investigated expression levels of IGF2R by real time RT-PCR and found them to be highly variable among the clone groups. ^ Using bisulfite genomic sequencing we have assessed the methylation status of cytosine in 44 CpG sites in a CpG rich intergenic region of the bovine IGF2/H19 genes in major organs of controls and clones. Analysis of an identified differentially methylated fragment in cloned bovine tissues displaying abnormal, biallelic expression of H19 [2], indicates hypomethylation of both alleles in some tissues. ^ Taken together, our data indicate that the epigenetic reprogramming of livestock created by somatic cell nuclear transfer, as indicated by the fidelity of imprinted gene expression, can be incomplete in the organs and tissues of cloned cattle at all developmental stages.