The thesis investigated a very fundamental biological question: how telomere length and telomerase activity is regulated during embryo development in mammals. It is argued that the cloned animal might inherit the shortened telomere length from the donor cell and thus is born prematured. Present work studied the dynamics of telomere length and telomerase activity during embryo development in several systems: in vivo embryo development, in vitro fertilized embryo development, parthenogenetically activated embryo development and cloned embryo development, using cattle and rabbit as model animals. A conserved telomerase dynamic pattern was found in early bovine embryos, derived from in vitro fertilization, parthenogenetic activation and nuclear transfer. It is proposed that the successful telomerase reprogramming in early NT embryos may contribute to the successful restoring of telomere length in cloned animals. Telomerase activity and telomere length of rabbit embryos were examined during in vivo development. Rabbit telomere length ranges from 15 to 36 kb, much longer than that of human (5–10 kb), in various fetal and adult tissues. Telomerase activity is present in all fetal and adult samples examined. This is similar to that of mice; however, different from human, in which telomerase is only detected in fetus, but not in any normal somatic tissues.
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