In vitro development of green fluorescent protein (GFP) transgenic bovine embryos after nuclear transfer using different cell cycles and passages of fetal fibroblasts

Nuclear transfer using transfected donor cells provides an efficient new st rategy for the production of transgenic farm animals. The present study ass essed in vitro development of nuclear transfer embryos using green fluoresc ent protein (GFP) gene-transfected bovine fetal Fibroblasts. In experiment 1, bovine fetal fibroblasts (BFF) were transfected with linearized pEGFP-N1 by electroporation, and the enucleated oocytes were reconstructed by nucle ar transfer of transfected cells (BFF-GFP). The rates of blastocyst formati on did not differ significantly between BFF and BFF-GFP (18.2% v. 15.6%). I n experiment 2, before nuclear transfer, the donor cell stage was synchroni zed by serum deprivation or forming a confluent monolayer. The rates of cle avage (67.1% v: 71.8%) and blastocyst formation (15.8% v: 15.5%) did not di ffer between confluent and serum-starved cells after nuclear transfer. In e xperiment 3, the effects of different passages of donor fibroblast cells on the development of nuclear transfer embryos were investigated. Donor cells from 'early' (at passage 8-16) showed better blastocyst development (18.9% ) than those from 'late' (at passage 17-32; 10.5%). Tn conclusion, this stu dy suggests that transgenic somatic cell nuclei from early passages can be reprogrammed more effectively than those from late passages. In addition, G FP, a non-invasive selection marker, call be used to select transgenic nucl ear transfer embryos.