Genetic basis of tissue specificity of vasculitis in MRL/lpr mice

Objective. To clarify the mode of inheritance of the tissue distribution of vasculitis in MRL/Mp-lpr/lpr (MRL/lpr) lupus-prone mice and to identify the susceptibility loci. Methods. Vasculitis in individual MRL/lpr, C3H/HeJ-lpr/lpr (C3H/lpr), (MRL/lpr X C3H/lpr)F-1, and (MRL/lpr X C3/llpr)F-2 intercross mice was analyzed by histopathologic grading of main branches of the aorta and of medium-sized arteries in the lower limbs. Genomic DNA samples from F2 intercross mice were examined by simple sequence-length polymorphism analysis, and the polymorphic microsatellite markers highly associated with vasculitis, in each tissue were determined as vasculitis susceptibility loci. Results. A susceptibility locus with significant linkage to vasculitis of main branches of the aorta was mapped on chromosome 4 at D4Mit213 (map position 13.3cM) selectively in males, while vasculitis of medium-sized arteries in the lower limbs was mapped to different chromosomes: at D8Mit31 on chromosome 8 (map position 33.0) selectively in females and at D5Mit36 on chromosome 5 (map position 65.0). All of these were different from the previously defined loci governing susceptibility to vasculitis involving the kidneys. Conclusion. Systemic vasculitis in MRL/lpr mice is genetically controlled with cumulative effects of multiple gene loci, each of which has tissue specificity.