Genetic dissection of proteinuria in the Sabra rat

The pathophysiology underlying proteinuria remains incompletely understood and warrants further research. We currently initiated the investigation of the genetic basis of proteinuria in the Sabra rat, a model of salt susceptibility that we showed previously to be also a model of spontaneous proteinuria that is unrelated to salt loading or development of hypertension. We applied the total genome scan strategy in 75 F₂ male animals derived from a cross between SBH/y, which are prone to develop proteinuria, and SBN/y, which are relatively resistant to the development of proteinuria. Animals were subjected to uninephrectomy (UNx) to accelerate the development of proteinuria and were provided chow with a low salt content, thus avoiding the development of hypertension. Urinary protein excretion was monitored before UNx and monthly thereafter for 8 mo. The genotype of F₂ was determined with microsatellite markers. The data were analyzed for cosegregation by ANOVA and for genetic linkage with a novel multifaceted statistical genetic paradigm. We detected three proteinuria-related quantitative trait loci (QTL) that were associated with the salt sensitivity (H) alleles from SBH/y: SUP2, SUP17, and SUP20 on rat chromosomes (Chr) 2, 17, and 20. We detected an additional QTL on Chr 3, SUP3, that was associated with the salt resistance (N) alleles from SBN/y. A temporal effect was noted: QTL SUP2 and SUP17 surfaced at months 7-8, QTL SUP20 at months 6-8, and QTL SUP3 at months 5-6. The QTL emerging from this study lead us a step closer to identifying the genes associated with and elucidating the pathophysiology of proteinuria.