Fusion of Rat and Mouse Morulae and Formation of Chimaeric Blastocysts

Pre-Implantation Development

“…Several attempts were made to produce intergeneric aggregation chimaeras between rat and mouse, but development went no further than the blastocyst stage (Mulnard, 1973;Stern, 1973;Zeilmaker, 1973); the injec- tion chimaeras of Gardner and Johnson (1973) and Gardner (1975) fared somewhat better, developing to the 33-somite stage. The most advanced stages reported so far are those obtained with sheep-goat aggregation chimaeras, some of which survived to adulthood (Fehilly et al, 1984) (Figure 2.9).…”

“…Other investigators have explored the potential for development of interspecific chimaeras by pairing the zonafree cleaving eggs of mouse and rat (Mulnard, 1973;Stem, 1973;Zeilmaker, 1973;Tachi and Tachi, 1980b) or of mouse and bank vole (Mystkowska, 1975). Well formed expanded rat-mouse blastocysts were obtained, the cells of both species contributing to both SCM and trophectoderm, but implantation after transfer was not observed.…”

Potential Use of Stem Cells for Kidney Regeneration

“…This strategy, however, was assessed to be unsuitable for human clinical application, because it is quite difficult to generate interspecific chimeras in livestock. Many groups have sought to generate interspecific chimeras between mouse and rat, achieving success with chimeric preimplantation embryos in vitro but failing with live chimeric animals [28, 29]. Extraembryonic lineage cells like trophectoderm, derived from xenogenic embryos, may suffer from inhibition of implantation on exposure to the host uterus, suggesting that only cells of preblastocyst origin can contribute to the extraembryonic lineage cells.…”

Physiology and Genetics of Reproduction

“…In the last few years, the technical armamentarium of the mammalian developmental biologist has expanded dramatically. Single blastomeres of mouse or rabbit can be separated to develop as "half' or "quarter" embryos (Tarkowski, 1959;Moore et al, 1968); two or more embryos from the same or related species can be aggregated to form composites (Tarkowski, 1961;Mintz, 1965;Zeilmaker, 1973); one or more cells can be injected into the blastocyst (Gardner, 1968); trophoblast and inner cell mass from different individuals can be reassembled (Gardner and Johnson, 1972); and inner cell mass can be differentially destroyed to leave only trophoblast (Snow, 1973a). Parthenogenetically activated eggs will develop as haploids, diploids or haplodiploid mosaics (Graham, 1970;Tarkowski et al, 1970), and cytochalasin-treated embryos can develop into tetraploid fetuses (Snow, 1973b).…”