SHEEP CLONED BY NUCLEAR TRANSFER FROM A CULTURED-CELL LINE

Nuclear transfer has been used in mammals as both a valuable tool in e mbryological studies(1) and as a method for the multiplication of 'eli te' embryos(2-4). Offspring have only been reported when early embryos , or embryo-derived cells during primary culture, were used as nuclear donors(5,6). Here we provide the first report, to our knowledge, of l ive mammalian offspring following nuclear transfer from an established cell line. Lambs were born after cells derived from sheep embryos, wh ich had been cultured for 6 to 13 passages, were induced to quiesce by serum starvation before transfer of their nuclei into enucleated oocy tes. Induction of quiescence in the donor cells may modify the donor c hromatin structure to help nuclear reprogramming and allow development . This approach will provide the same powerful opportunities for analy sis and modification of gene function in livestock species that are av ailable in the mouse through the use of embryonic stem cells(7).