Production of transgenic mice following deoxyribonucleic acid microinjection and embryo freezing

Experiments with mouse embryos were designed to assess the feasibility of freezing embryos after DNA microinjection. One-cell pronuclear stage mouse embryos were microinjected with cloned deoxyribonucleic acid (DNA) and cultured in vitro to the late eight-cell stage. Microinjected and matched control embryos were frozen and stored in liquid nitrogen. Following thawing, embryos were cultured for 8 h and transferred to recipient females. In a separate set of experiments, embryos were transferred to recipients immediately following DNA microinjection. Control (uninjected) embryos developed to the late eight-cell stage significantly better than surviving microinjected embryos. Of the embryos thawed, 76% of the microinjected and 60% of the control embryos survived to be transferred to recipients. Progeny were obtained with similar survival rates from both groups following embryo transfer with transgenic mice identified among the progeny from microinjected embryos. Mouse embryos can be microinjected with DNA, cultured in vitro, frozen, thawed, transferred to recipients and transgenic progeny can be obtained.