A molecular genetic linkage map of mouse chromosome 19, including thelpr, Ly-44, andTdt genes

The mouse lpr gene, which is an autosomal recessive gene causing autoimmune disease with features of human systemic lupus erythematosus and eventually death from severe immune-complex glomerulonephritis, has been mapped on chromosome 19. To determine its exact chromosomal location, a three-point backcross was carried out by mating (MRL/MpJ-lpr/lpr x MOL-MIT)F1 x MRL/MpJ-lpr/lpr using the genes Ly-44 (lymphocyte differentiation antigen-44) and Tdt (terminal deoxynucleotidyl transferase) as markers. The following order of genes is proposed, with the distances between genes given in parentheses: centromere-Ly-44 (19.3 cM)-lpr (6.1 cM)-Tdt-telomere. The Ly-44a and Tdta alleles are found in all laboratory strains and in the wild Western European subspecies, domesticus and brevirostris. In contrast, the Ly-44b and Tdtb alleles are found in some Asian subspecies, Chinese mice of wild origin, yamashinai and molossinus. Furthermore the third Tdt allele, Tdtc, is detected in castaneus.