Localization of a blood pressure quantitative trait locus (QTL) to a 1.7cM interval on rat chromosome 9

An F₂ (SxR) population of 233 rats was previously used to conduct a linkage analysis. A blood pressure quantitative trait locus (QTL) was found on rat chromosome 9 with a high LOD score of 5.0, and initially trapped within a 34.2cM congenic interval in a congenic strain, S.R(chr 9). In the current work, to further localize this blood pressure QTL, congenic substrains were constructed from the progenitor congenic strain, S.R(chr 9). Blood pressure and heart weight comparisons between these congenic substrains and their S control showed that the blood pressure QTL was in a 4.6cM interval. Two solute carrier (Na+/H+ exchanger) genes, Nhe2 and Nhe4, were excluded as candidates based on their map locations. A second iteration of congenic substrains was used to further localize the QTL to a 1.7cM interval from marker D9MlMit484 cluster to marker D9Uia6. Another solute carrier (Cl−/HCO ₃− anion exchanger) gene, Ae3, was sequenced for both S and R strains and found no coding sequence variations between the two strains. In addition, with the help of congenic substrains, Ae3 gene was also excluded as a candidate because it was located outside of the 1.7cM QTL containing interval. Although the identity of the QTL remains unknown, the map location of this QTL has been reduced from an interval of 34.2cM to 1.7cM.