Telomerase activity in early bovine embryos derived from parthenogenetic activation and nuclear transfer.

This study examined the telomerase activity in preimplantation bovine embryos derived from either parthenogenetic activation or nuclear transfer. Telomeres are the DNA-protein structures located at the ends of eukaryotic chromosomes. Telomerase is the ribonuclear enzyme that helps to restore telomere length by synthesizing telomeric DNA repeat (5'-TTAGGG-3') from its own RNA template. Without telomerase activity, telomeres shorten with each cell division through conventional DNA replication. In most mammalian species, telomerase activity is present in germ cells but not in somatic cells. Previously, we reported the dynamics of telomerase activity in bovine in vitro fertilized (IVF) embryos. In the present study, we examined the telomerase activity in bovine embryos derived either from parthenogenetic activation or somatic cell nuclear transfer (i.e., cloning). Embryos from both sources were harvested at different stages, from zygote to blastocyst. Telomerase activity in embryos derived from parthenogenetic activation and nuclear transfer showed a dynamic profile similar to that of those derived from IVF. Telomerase activity was detected in embryos at all stages examined, with the highest level in the blastocyst stage, regardless of the method of embryo production.