As part of a long-term program to analyze the effects of murine retrovirus associated genes on hematopoietic system tumors, both spontaneous and those induced by chemicals or virus inoculation, a number of genes of interest are being bred onto inbred mouse backgrounds. The majority of congenic lines are being established on the NFS Swiss mouse background, providing a standard background which is negative for its own endogenous ecotropic virus. Lines include the V-loci congenics (carrying ecotropic virus loci from AKR, C58, or C3H/Fg; and mice carrying specific viral resistance genes (Fv-4, Rmcf) or linkage marker genes. Two attempts are in progress to establish congenic lines of AKR and C57BL which will lack ecotropic MuLV induction loci; these lines are at backcross 8 and backcross 6, respectively. V-cogenic mice, particularly NS.C58v1, are being used in studies of oncogenicity of various acute transforming and replication competent MuLVs.
