Isolation and properties of hybrids between somatic mouse and Chinese hamster cells.

HE occurrence of hybridization between in uitro cultured cells of different Tspecies was first demonstrated in 1965 by EPHRUSSI and WEISS, who, by using the selective technique of DAVIDSON and EPHRUSSI (1965), succeeded in isolating viable, monoriucleate hybrids between heteroploid mouse and diploid rat cells. Shortly thereafter, these investigators isolated a number of other rat X mouse hybrids ( WEISS and EPHRUSSI 1966a). Following these observations, crosses between cells of permanent lines of mouse and of Chinese hamster origin have been undertaken. The aim of these experiments was to extend to another pair of species the observations referred to above. The choice of the species was motivated by the following considerations. The karyotype of the chosen pseudodiploid, drug resistant hamster line comprises a relatively small number of chromosomes, almost all of which can be identified by their characteristic morphology. Two lines of mouse cells were available which carry complementary selective markers and have karyotypes very different from that of the hamster cells. It was therefore expected that the hamster x mouse hybrids would be easily identified. Moreover, since many of the chromosomes of the hamster line can be distinguished from those of mouse lines, it was thought that hybrids between these two cell types would represent excellent material for the study of the evolution of their karyotypes. As will be seen below, two types of hamster x mouse hybrids have been isolated and a certain number of observations on their properties and evolution have been made. It is the purpose of this paper to describe these observations.