Modifier loci in non-mutant, female Wistar Kyoto rats influence cellular pathogenesis of nephronophthisis in Lewis polycystic kidney rats

Genetic modifier loci influence the inheritance of diseases and lead to variability in phenotype progression. We report the influence of modifier loci in female Wistar Kyoto (WKY) rats on cellular pathogenesis of nephronophthisis inherited from Lewis polycystic kidney (LPK) rats. The loci modified cellular expression and progression of nephronophthisis in the backcross 1 (BC1) progeny. Mating experiments to produce BC1 progeny were carried out between three male LPK and seven female WKY rats. Fifteen female rats from the F1 generation were mated with the male LPK rats to produce the BC1 progeny. The rats with cystic kidney disease were identified and histology of the kidneys was carried out. Mapping studies and linkage analysis were carried out to identify the modifier loci. The BC1 progeny were less affected than the LPK strain with respect to disease severity and progression of the kidneys to end stage renal disease. It was found that the mean values of all the disease phenotypes of the mutant BC1 progeny were significantly different from those of the LPK rats, and these segregated with the genotypes of the markers located on chromosomes 5q34–q36 and 7q11–q34, giving maximum LOD scores greater than 3 (p < 0.001).