Phenotypic differences between diabetes-prone BB rat sublines cosegregate with loci on chromosomes X and 10.

BB rat sublines, all developing an insulin-dependent diabetes, differ in several phenotypic traits and in the genotype. To study the genetic basis of phenotypic differences diabetic BB/OK and BB/Mol rats characterized by significantly different frequency and age at onset of diabetes were reciprocally crossed. F1 females of both crosses were backcrossed onto diabetic BB/Mol rats resulting 94 BC1 hybrids which were analyzed for 30 polymorphic microsatellite markers on 14 chromosomes. For the first time it is shown that a diabetes protective locus on chromosome X and a gene around the D10Mit9 locus on chromosome 10 can explain the low frequency (ca. 50%) and the late age at onset of diabetes (ca. 130 days) in the BB/OK rat subline, respectively.