Gene expression in murine hybrids exhibiting different morphologies and tumorigenic properties

Abstract

[³⁵S]Methionine labelled polypeptides from mouse CLID, hamster ovary cells (CHO, and 7 derived somatic cell hybrids which have segregated CHO chromosomes, were analysed by means of high resolution two-dimensional gel electrophoresis under conditions in which the position of 600 polypeptides could be reproducibly assessed. As judged from the two-dimensional gel electrophoretic patterns (isoelectric focussing (IEF) and non-equilibrium pH gradient electrophoresis (NEPHGE)) gene expression in all the hybrids resembled the mouse CLID parent and with only one exception they all expressed different numbers and intensities of CHO specific polypeptides. Even though some of the hybrids expressed as much as 50% of the total number of CHO specific polypeptides that could be clearly differentiated from those of the mouse parent we failed to find a direct correlation between the expression of any given CHO polypeptide and the morphological or tumorigenic properties of the hybrids. Most CHO specific polypeptides, however, were expressed at lower levels in the hybrids as compared to the parent CHO cells, a fact that may be due to the chromosomal constitution of the hybrids, regulation or both. Similarly, the quantitation of the major cyto-skeletal polypeptides present in the hybrids, such as a-and B-tubulin, vimentin, total actin and 3 polypeptides (IEF 12, 24 and 31) present in intermediate filament enriched cytoskeletons, indicated that changes in the relative proportion of any of these proteins is not sufficient to account for the morphology, actin microfilament pattern or tumorigenicity of the hybrids. Co-expression of cytoskeletal proteins in the hybrids could only be demonstrated in the case of the related mouse IEF 24 and hamster IEF 7 polypeptides. In all other cases the cytoskeletal polypeptides co-migrated and presented similar one-dimensional peptide maps. Some principles are emerging concerning the possibility of using somatic cell hybridization in combination with two-dimensional gel electrophoresis to locate genes coding for particular polypeptides on a given chromosome.