Derivation of SHR-chromosome 4 congenic sublines for fine genetic mapping of quantitative trait loci with major effects on insulin resistance and blood pressure

Recently, we have found that transfer of a segment of chromosome 4 between I16 and Npy markers from the Brown Norway (BN) rat into the spontaneously hypertensive rat (SHR) significantly attenuated both hypertension (measured by telemetry) and insulin resistance (measured as plasma insulin/glucose ratios before and after a high fructose diet) in the SHR progenitor strain. To map the putative quantitative trait loci (QTL) more precisely, we derived an (SHR×SHR.BN-chr.4)F2 population to search for recombinants that will enable us to produce congenic sublines. The F2 animals were genotyped in markers equally distributed along the interval of the chromosome 4 differential segment. Altogether, five new congenic sublines with overlapping segments of the differential chromosome 4 are being produced. New congenic sublines will enable us to test the hypothesis that insulin resistance and hypertension can be influenced by closely linked genes or perhaps even the same gene(s) on chromosome 4.