Resistance to friend leukemia virus in transgenic mice expressing the native FV-4 gene

Fv-4 is a truncated ecotropic retrovirus gene that codes for an envelope pr otein under control of a cellular promoter. It confers resistance to ecotro pic murine leukemia viruses. Transgenic mice were derived using the native Fv-4 gene as the construct for microinjection. Two founder mice were derive d. In both founder lines, there was no detectable expression of the transge ne or resistance to Friend murine leukemia virus (FrMLV) in hemizygotes. In one line, the resistance was observed in homozygotes with Fv-4 RNA formati on in the thymus but not in the spleen or in other tissues. Tn the other fo under line, a homozygous male was identified. Double integrants, derived fr om breeding this homozygous male to homozygous females from the other found er line, were also resistant. These results indicate that the native gene c onfers the resistance in homozygous transgenic mice or double integrants de rived from different founders but not hemizygotes.