Viable Chimaeras Produced from Normal and Parthenogenetic Mouse Embryos

Abstract

Parthenogenesis occurs spontaneously in about 10% of ovulated eggs of inbred strain LT/Sv mice (Stevens and Varnum 1974; Stevens 1975) and is experimentally inducible in other strains by various physical and chemical agents (see Tarkowski 1975 for review). The development of most parthenotes seems normal up to the expanded blastocyst stage (Van Blerkom and Runner 1976). They implant in the uterus, but, for reasons unknown, are resorbed within a few days. Although they rarely survive to 8 days of gestation when they develop somites, heart muscle, amnion, and neuroepithelium, Kaufman, Barton, and Suram (1977) obtained two embryos with 25 somites by transferring parthenogenetic blastocysts to the uteri of ovariectomised females treated with exogenous hormones. Even though parthenogenetic embryos do not survive to birth, their cells contain genetic information that permits prolonged survival. If two-cell parthenotes are cultured to the blastocyst stage and then grafted to extrauterine sites such as the testis or kidney, they may survive as teratomas composed of several types of tissues and undifferentiated embryonal cells (Stevens 1974; Ilse et al. 1975; and L.C.S. and D.S.V., unpublished).