Analysis of Fv-1 restriction in two murine embryonal carcinoma cell lines and a series of differentiated derivatives

1 Cellular and Genetic Toxicology Branch and 2 Laboratory of Pulmonary Pathobiology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, U.S.A. We have used antibiotic-resistant retrovirus vectors rescued by Fv-1 -sensitive murine leukaemia viruses (MuLV) to examine the Fv-1 phenotype of two undifferentiated embryonal carcinoma (EC) cell lines derived from teratocarcinomas of mouse strain 129. In addition, a set of EC cell-derived differentiated cell lines was analysed. Restriction of both B-tropic and endogenous N-tropic virus is characteristic of the N r -type restriction reported in mouse strain 129. However, results indicate that Fv-1 restriction is not expressed in the PCC4.aza1R EC cell line. In contrast, the F9 EC cell line showed a strong restriction of the B-tropic pseudotyped vector but failed to restrict endogenous N-tropic pseudotypes. The Fv-1 gene thus seems to be differentially expressed in two EC cell lines derived from the same mouse strain. Furthermore, the selective restriction of B-tropic but not endogenous N-tropic MuLV in F9 cells suggests that these activities function independently of each other. Analysis of PCC4.aza1R-derived differentiated cell lines revealed that three fibroblast cell lines derived by retinoic acid-induced differentiation were also phenotypically silent for Fv-1 . However, a pre-adipocyte line established following simultaneous exposure to retinoic acid and 5-azacytidine showed strong restriction of both B-tropic and endogenous N-tropic MuLV. Although additional data suggest that there is no correlation between the differentiated pre-adipocyte phenotype and Fv-1 expression, our results nonetheless show that N r restriction can be observed in some derivatives of PCC4.aza1R cells, presumably by activating expression of the Fv-1 gene. Present address: Division of Virology, Wellcome Research Laboratories, Burroughs Wellcome Co., 3030 Cornwallis Road, Research Triangle Park, North Carolina 27709, U.S.A. Received 3 August 1990; accepted 29 November 1990.