Isolation and some properties of temperature-sensitive mutants of mouse fibroblasts with respect to morphological transformation.

We have isolated from a mouse fibroblast strain C3H2K several temperature-sensitive mutants that express their transformed phenotype at low (33 degress C) but not at high (38 degrees C) temperature. The mutant clones exhibited a piled up and criss-cross pattern of growth and a high saturation density at 33 degrees C, but flat density-inhibited monolayer and a low saturation density at 38 degrees C. The temperature-dependent exprestion of transformed phenotype was fully reversible upon temperature shift, and seemed to require cell division. Plating efficiencies of the clones in liquid medium were slightly higher at 33 degrees C than at 38 degrees C, but the cells were unable to form colonies in soft agar medium.