CONSTRUCTION OF A DOUBLE CONGENIC STRAIN TO PROVE AN EPISTATIC INTERACTION ON BLOOD-PRESSURE BETWEEN RAT CHROMOSOME-2 AND CHROMOSOME-10

Previously we presented suggestive evidence from an F-2 segregating po pulation for an interaction on blood pressure (BP) between quantitativ e trait loci (QTL) on rat chromosomes (Chr) 2 and 10. To prove the exi stence of such an interaction, we developed congenic strains for Chr 2 and 10 by introgressing the low BP QTL alleles into the Dahl salt-sen sitive (S) strain. A double congenic strain was also constructed with both the Chr 2 and 10 low BP QTL alleles on the S background. The four strains (S, Chr 2 congenic, Chr 10 congenic, and Chr 2/10 double cong enic) were studied, for BP response to increased salt intake. An analy sis of variance showed significant main effects of Chr 2, Chr 10, and a significant interaction between Chr 2 and 10 on BP and heart weight (all P < 0.0001). The interaction accounted. for 24 mmHg of BP and 79 mg of heart weight. Thus, the discovery and proof of epistatic interac tions are clearly critical to understanding the genetics of blood pres sure.