본 연구는 한우 성체 유래 귀세포(Korean bovine ear skin fibroblasts, KbESF)와 태아 섬유아세포(Korean bovine fetal fibroblasts, KbFF)를 이용한 체세포 복제(SCNT) 시 세포종류, 배양기간 그리고 융합방법이 핵이식 수정란의 발달에 미치는 영향을 알아보기 위하여 실시하였다. 태아 섬유아세포는 임신 51일령의 한우태아에서 분리하였고, 귀세포는 28개월령의 성우의 귀에서 채취하였다. 세포는 15주 동안 체외에서 배양하며 체세포 핵이식(SCNT)에 공시하였다. 융합방법을 비교하기 위해 챔버방법과 전극 바늘을 이용한 방법으로 핵과 세포질을 융합하였다. 세포의 doubling time은 KbFF에서 17.3시간, KbESF에서 24.3시간으로 나타났다. 핵이식 후 융합과 분할율은 needle 방법에서 보다 유의적으로 높았으나(각 각 76.1과 81.2%, P<0.05), 배반포 발달율은 차이가 없었다. KbESF의 경우, 배반포 발달율은 passage 5~9(39.4%)와 13~15(40.4%)에서 passage 1~4에 비하여 유의적으로 높았다(P<0.05). KbFF의 경우, 융합율은 passage 5~8과 13~15에서 각각 75.0 및 76.8%로 passage 1~4(61.5%)보다 높았으나, 난분할율과 배반포 발달율은 차이가 없었다. 결론적으로, SCNT 수정란의 발달은 융합 방법에 의해 영향을 받을 수 있으나, 계대배양 15회까지 장기배양을 한 경우는 복제수정란의 발육에 영향을 주지 않는 것으로 판단된다.

Research has been in progress for more than a decade to production of useful proteins by genetic modification in cattle. However, the levels of protein production in transgenic cattle have been reported very low. To enhance protein production in transgenic animal, we tried homologous recombination to donor cells for production of transgenic clone cattle through nuclear transfer procedure. Thus, we constructed the two targeting vectors of human thrombopoietin (TPO) at bovine -casein locus using homologous recombination with 13.6 kb and 9.6 kb homology. In two targeting vectors, positive selection was through the neomycin resistance gene and negative selection was by the diphtheria toxin (DT). Gene targeting was attempted in bovine embryonic fibroblasts (bEF) and bovine ear skin fibroblasts (bESF). To determine the most appropriate concentration of neomycin for bEF and bESF, G4l8 resistance was confirmed by culturing the cells in various concentrations of the drug and both of the cells were optimally selected at of neomycin. The transfected bEF and bESF by the targeting vectors were colonized efficiently at the ratio of DNA to transfection reagent such as :2 and :. Comparing number of healthy clones from passage 4 to passage 8, bESF (17%) persist in culture for much longer than bEF (6%). The two gene-targeted bESF clones of 30 random-integrated clones with 9.6 kb homology length were confirmed, however, nothing was out of 72 random integration clones with 13.6 kb homology length, The DT also worked more efficiently in clones transfected with the vector of 9.6 kb homology length. Our data suggests that the choice of donor cell for long culture period should be considered to obtain targeted cell clone, and the gene-targeting frequency and the DT working efficiency are dependent on the length of target homology.