Transfer of heritable properties by cell hybridization: specificity and the role of selective pressure

Enucleated chloramphenicol (CAP) resistant mouse L-cells (LEA-2A) were fused with the mouse hepatoma cells (BW1J). The resultant cybrids expressed CAP resistance (the property used in selection of the cybrids), and also expressed the hepatic-specific functions of the BW1J parent. Hybrids between these same cells, on the other hand, exhibited chloramphenicol resistance and extinction of the hepatoma-specific properties. Cybrids were also prepared between enucleated rat hepatoma cells (FT-2) and mouse erythroleukemia cells (C19TK). The resultant cybrids selected in tyrosine-free medium expressed phenylalanine hydroxylase, an enzyme normally appeared to be the result of activation of the previously silent gene of the C19TK cells. These cybrids, however, did not express any other liver-specific functions present in the FT-2 cytoplast donor. These experiments suggest that the transfer of heritable properties by cell cybridization is selection specific and that activation or extinction observed in hybrids may not occur in cybrids of the same cells.