Efficacious Production of Viable Germ‐Line Chimeras between Embryonic Stem (ES) Cells and 8‐Cell Stage Embryos

Abstract

Many embryonic stem (ES) cell lines have been isolated from various mouse strains, but production of germ‐line chimeras has been achieved with only strain 129. This report describes the isolation of a new ES cell line, F1/1, from a mouse blastocyst with the C57BL/6 X CBA male genotype and tests on its ability to produce germ‐line chimeras by two techniques, blastocyst injection and 8‐cell embryo injection. Chimera production using CD‐1 blastocysts as a host was low (20%), as reported by others. But by the 8‐cell embryo injection method, in which F1/1 cells were injected into the perivitelline space through a slit in the zona pellucida of 8‐cell embryos, chimeric mice with extremely high chimerism were obtained at a rate of 80%. Breeding tests showed that 89% of the fertile males were germ‐line chimeras and in most case, the majority of the sperms in their testes were derived from F1/1 cells. This F1/1 cell line with a different genotype from the 129 strain shows high ability to produce functional germ cells, moreover, the 8‐cell embryo injection method using F1/1 cells seems to be an efficient way to produce viable germ‐line chimeras.