Relationship between a retroviral germ line reintegration and a new mutation at the ashen locus in B10.F mice. Retroviral integration and an ashen mutation.

In a litter of B10.F mice a single mouse was found with a "dilute-like" coat-color mutation. F2 matings were then carried out to establish sufficient numbers of mice carrying this mutation in a homozygous form. The coat-color mutation was found to be allelic to the ashen locus which is closely linked to the dilute locus on chromosome 9. Further analysis of the ashen mice showed they contained an additional ecotropic provirus integrated into their chromosomal DNA. This result initially suggested that retroviral integration was responsible for the mutation. However, backcross studies showed the mutation and provirus were genetically unlinked. The reintegrated provirus was molecularly cloned and transfection studies showed the virus was B tropic in host range. The restriction map of the cloned provirus was found to be similar to previously described B-tropic viruses. The results are discussed in view of the low probability of two rare and unlinked events occurring in a single mouse.