Clonal lines of transgenic fibroblast cells derived from the same fetus result in different development when used for nuclear transfer in pigs

Different Factors are believed to influence the outcome of nuclear transfer (NT) experiments. Besides the cell cycle stage of both recipient cytoplast and donor karyoplast, the origin of the donor cells (embryonic, fetal, and adult) is of interest. We compared in vitro development of NT embryos deri ved from small serum-starved (GO) or small cycling (G1) porcine fetal fibro blast cells. Serum starvation did not have a positive effect on cleavage ra te or the percentage of embryos that developed to the morula and blastocyst stages. Next, we investigated the development of porcine NT embryos derive d from different transgenic clonal cell lines that had originated from the same fetus. When different clonal lines of fetal fibroblasts were fused to enucleated metaphase II oocytes, differences in fusion rates as well as in development to the morula and blastocyst stages were observed (P < 0.05). W hen oocytes derived from sow ovaries were used as recipient cytoplasts, sig nificantly better cleavage (P = 0.03) and blastocyst formation (P < 0.014) was obtained when compared with oocytes derived from gilts. Our data indica te that not only different cell lines, but also different clones derived fr om one primary cell line, result in different development when used for NT, In addition, the use of sow oocytes as a cytoplast source also improves th e efficiency of NT experiments.