Epigenetic characterization of the CpG islands of bovine Leptin and POU5F1 genes in cloned bovine fetuses.

Abnormal development and fetal loss during postimplantation period are concerns for production of nuclear transferred animals. Aberrant DNA methylation is one of the reasons for poor survival of cloned animals. In mammalian genome DNA, CpG islands are preferentially located at the start of transcription of housekeeping genes and are associated with tissue-specific genes. The correct and consecutive mechanisms of DNA methylation in the CpG islands are necessary for selective gene expressions that determine the properties of individual cells, tissues, and organs. In this study, we investigated the methylation status of the CpG islands of the bovine Leptin and POU5F1 genes in fetal and placental tissues from fetuses produced by artificial insemination (AI) and nuclear transfer (NT) at days 48 and 59 of pregnancy. Altered DNA methylation was observed in the normal and cloned fetal, placental, and endometrial tissues using bisulfite sequencing and pyrosequencing. Different tissue-specific methylated regions in the bovine Leptin and POU5F1 genes show a variable methylation status in NT fetuses compared to AI control.