NUCLEAR TRANSFER IN THE BOVINE USING MICROINJECTED DONOR EMBRYOS - ASSESSMENT OF DEVELOPMENT AND DEOXYRIBONUCLEIC-ACID DETECTION FREQUENCY

Bovine embryos that had been microinjected with DNA were examined for their potential use as donor embryos in nuclear transfer. Donor embryo s were obtained from oocytes collected by transvaginal oocyte aspirati on, matured and fertilized in vitro, microinjected with a murine whey acidic protein-human protein C genomic DNA construct, and cultured in vitro on liver cells of buffalo rat (Rattus norvegicus). Blastomeres f rom these embryos were transferred into enucleated bovine oocytes rece ived from an abattoir by electrofusion at 40 h post-maturation. Follow ing 7 d of culture, the developmental stage was recorded, and resultin g embryos were prepared for analysis by polymerase chain reaction. Emb ryos that were derived from microinjected donor embryos did not differ from control donor embryos (11 vs. 8.6%) in development to the morula and blastocyst stage. Of the biopsies from 20 microinjected donor emb ryos, 19 were positive for the injected DNA. Of 37 embryos developing normally, only 12 (32.4%) were positive for the injected DNA. These re sults indicate that microinjected embryos can be successfully used in a nuclear transfer program to produce additional viable embryos and th at these embryos may be reliably screened for the transgene for transf er to recipients.