Selective expression of xenotropic virus in congenic HRS/J (hairless) mice

Abstract

GENETIC factors strongly influence susceptibility to leukaemia in mice. In some instances leukaemogenesis hinges on only a few genes, or even a single gene¹. The hairless mutation is an example of this. Homozygotes for this autosomal recessive gene (hr/hr) have a high incidence of thymic leukaemia (45% at 8–10 months), whereas the incidence in heterozygotes (hr/ +) is low (1% at 8–10 months)². The leukaemogenic effect produced by homozygocity for hr is unknown. Here we report that thymuses of hr/hr mice produce high titres of xenotropic viruses, whereas thymuses of hr/ + mice do not. Furthermore, viruses with a broadened host range were isolated from thymuses of preleukaemic hr/hr mice, but not from any tissue of hr/ + mice. We propose that the mutant gene hr specifies circumstances that augment production of xenotropic virus by the thymus. This phenomenon may be an important step in the development of thymic leukaemia.