79 THE AMOUNT OF TELOMERIC DNA IN CLONED CATTLE AND THEIR CALVES IS LESS THAN THAT OF AGE MATCHED CATTLE

Abstract

A telomere is a structure consisting of tandem repeats sequences of (TTAGGG)n at the end of the eukaryotic chromosome. Telomere lengths in animals vary by species, age, and tissues, as well as environment. This experiment concentrated on the amount of telomeric DNA in cloned cattle, their calves, and age-matched normal cattle. Using somatic cell nuclear transfer (SCNT), we had obtained 16 cloned Korean Native cows derived from ear skin fibroblasts and two cloned bulls from fetal fibroblasts. In addition, four female calves were produced from each cloned cow by artificial insemination. Control cattle selected to have matched age and the same raising place served as counter-parts of cloned the cattle in this study. The lymphocytes of all cloned cattle, their calves, and the age-matched controls were examined for telomere quantity. The amount of telomeric DNA was analyzed by quantitative fluorescence after in situ hybridization (Q-FISH) with a human telomeric DNA repeat probe. A minimum of 100 interphase nuclei from each set of harvests was studied to determine the mean and medium percentages of telomeric DNA using the MetaMorph Imaging System (Universal Imaging Co., West Chester, PA, USA). The amount of telomeric DNA obtained was found to decrease in cloned and control animals during growth. The amounts of telomeric DNA in cloned cattle from both ear skin fibroblasts (n = 16) and fetal fibroblasts (n = 2) was less than that of age-matched controls (P < 0.01). Surprisingly, the amount of telomeric DNA of calves from cloned cattle was also lower than that of age matched controls (n = 4, P < 0.01). The results showed a remarkable difference in the amount of telomeric DNA between SCNT cloned cattle and normal cattle. In conclusion, the telomeres of cloned animal and their calves are significantly shorter than those of normal cattle. Moreover, the short telomeres in calves could be inherited from their cloned mothers.