Methylation and expression changes in imprinted genesH19andIgf2during serial somatic cell nuclear transfer using piglet fibroblasts

Cloned pigs produced by somatic cell nuclear transfer (SCNT) are important as a potential alternative source of organs. Although SCNT has created new possibilities for targeted gene modification, the successful cloning of pigs is rare. Here, we successfully conducted serial SCNT for three generations. We determined that the piglet genome was inherited from donor cell nuclei using microsatellite analysis of each generation. The methylation of differentially methylated regions (DMRs) in H19 was gradually reduced over the three generations of serial SCNT. By contrast, methylation of the insulin-like growth factor 2 (Igf2) DMR increased in the F1 generation, compared to the F0, and remained at the higher level in the F2 and F3 generations. The methylation patterns of housekeeping genes such as GAPDH and β-actin were unchanged in the serially cloned pigs. In addition, expression levels of H19 and Igf2 were variable for each generation of serial SCNT piglets, but there was no clear relationship between the meth...