PHENOTYPIC-EXPRESSION IN CYBRIDS DERIVED FROM TERATOCARCINOMA CELLS FUSED WITH MYOBLAST CYTOPLASMS

Enzyme-deficient (HGPRT-) embryonical carcinoma cells (EC-cells) from a mouse teratocarcinoma were fused with enucleated L6J1 myoblasts (HGPRT+) so as to generate cells with a hybrid cytoplasm (cybrids). During the first 2-3 days after fusion, these cells differed from parental EC cells, as judged by morphology and size. In addition HGPRT activity from the myoblast cytoplasm was present during this early stage but was subsequently lost. Colonies of cells originating from the initial cybrids were isolated and analysed for myogenic properties typical of the cytoplasmic donor cell. It was found that the cybrid progeny was unable to undergo myogenic differentiation under conditions where the L6J1 cytoplasmic parent formed well developed multinucleate myotubes. Comparison of the polypeptide patterns of the cybrids with those of the parental embryonal carcinoma cells by two-dimensional gel electrophoresis revealed no reproducible differences. Thus, the gene expression pattern of the embryonal carcinoma cell nucleus is not detectably altered by exposure to myoblast cytoplasm. A new selection system for isolation of cybrids is described. © 1979.