Abstract
Production of chimeras between embryonic stem (ES) cells and zone-free embryos was examined in mice under coculture conditions. A3-1 ES cells were cocultured at concentrations of 0.5×106 or 1.0×106 cells/ml with zona-free embryos of 8-cell or morula stage in Dulbecco's modified Eagle's medium containing 5% fetal calf serum (FCS) and 23mM lactate (DMEM) or Whitten's medium containing 10% FCS (WM). Three hours later the cocultured embryos were transferred into WM and cultured again for 22-24 hr. The embryos developed to blastocyst stage were transferred into foster mother, and 17 days later the pups including chimeras were obtained. When morula stage embryos were cocultured with ES cells at a concentration of 0.5×106 cells/ml in DMEM, the highest rate of production of chimeric mice (5.4%) was obtained. These our results indicate that the coculture method is useful for the production of chimeras between A3-1 ES cells and zona-free morula embryos.
