Genetic diversity in leukemia-prone feral house mice infected with murine leukemia virus

Abstract

The Lake Casitas (LC) mouse population located in south western Ventura county in California is unusual insofar as 85% of these mice are persistently viremic with congenitally transmitted murine leukemia virus (MuLV). The virus has been identified as the etiological agent responsible for lymphoma and neuromotor paralysis in large numbers of the mice. The majority of other wild mouse populations are generally free of infectious MuLV despite the presence of endogenous cellular DNA sequences homologous to infectious virus isolated from wild mice. Electrophoretic variation in 46 gene-enzyme systems was surveyed using mice from Lake Casitas and from a virus-negative population located in Bouquet Canyon (BC) approximately 40 miles from Lake Casitas. The LC and BC populations are genetically very similar to each other and to feral mouse populations previously studied in California and Europe. In the LC population 24% of the loci are polymorphic compared to 17% in the BC population. The average heterozygosities for the LC and Bc populations are 0.094 and 0.073, respectively. The large amount of genic variation in LC fails to support the concept of the derivation of the colony from a small number of founders. Tests for linkage disequilibrium and/or selective association of viremia and polymorphism at 15 loci located on nine mouse chromosomes did not reveal any nonrandom assortments. The viremic LC population, then, appears indistinguishable within the limits of experimental resolution from the virus-negative BC population in its population genetic structure.

Evidence for the horizontal acquisition of murine AKR virogenes by recent horizontal infection of the germ line

“…Two feral mouse populations of domesticus, Lake Casitas and Bouquet Canyon (36), were also included in the analysis. The remaining seven strains included three outbred Swiss mouse colonies (NIH, Eppley Institute, and CD1) and four inbred Swiss derivatives (NFS, NFR, HSFR, and HSFS) (19).…”

Evolution in Inbred Strains of Mice Appears Rapid

“…However, this value is the same as the 0.09 e §timated for four populations of Mus musculus musculus (18). Estimates of original heterozygosity for wild populations of M. m. domesticus (18,19) range from 0.06 to 0.09, while the estimate for M. m. brevirostris is 0.11 (18). If a new population were created by mixing equal numbers of each of these ten strains, its heterozygosity would be 0.33.…”

Murine retroviral restriction genes Fv-4 and Akvr-1 are alleles of a single locus

“…The F1 animals were crossed to AKR mice to test for independent assortment of Fv4 versus Akvr-1, using suppression of AKR viremia as our assay for restriction. The results of virus assay of crosses involving these strains are summarized (11) and viremia by the fluorescent-antibody test on SC-1 cells.…”