CLONED TRANSGENIC CALVES PRODUCED FROM NONQUIESCENT FETAL FIBROBLASTS

An efficient system for genetic modification and large-scale cloning o f cattle is of importance for agriculture, biotechnology, and human me dicine. Here, actively dividing fetal fibroblasts were genetically mod ified with a marker gene, a clonal line was selected, and the cells we re fused to enucleated mature oocytes. Out of 28 embryos transferred t o 11 recipient cows, three healthy, identical, transgenic calves were generated. Furthermore, the life-span of near senescent fibroblasts co uld be extended by nuclear transfer, as indicated by population doubli ngs in fibroblast lines derived from a 40-day-old fetal clone. With th e ability to extend the life-span of these primary cultured cells, thi s system would be useful for inducing complex genetic modifications in cattle.