Genetic and crude physical mapping have yielded chromosome regions containing quantitative trait loci for blood pressure in Dahl salt-sensitive rats. So far, the molecular identities of these loci are largely unknown. Intriguing still is how these quantitative trait loci would interact with each other to achieve an overall blood pressure effect. Alleles of some loci previously identified as blood pressure quantitative trait loci in other rat strains appear to be the same between Dahl salt-sensitive and salt-resistant rats. Why do Dahl salt-resistant rats have low blood pressure whereas Dahl salt-sensitive rats develop high blood pressure?
With the use of congenic strains and ‘double’ congenics, these issues have begun to unravel. Certain quantitative trait loci exert major blood pressure effects (> 20 mmHg) and each of them can be dissected as a monogenic trait. Some appear to be located close to each other in the same chromosome region. Different quantitative trait loci interact epistatically to produce their combined blood pressure effects. ‘Low’ blood pressure alleles of one quantitative trait locus can compensate for the ‘high’ blood pressure alleles of other quantitative trait loci in the Dahl salt-resistant rat. By integrating fine mapping and positional cloning strategies, blood pressure quantitative trait loci are being elucidated. Work in the rat may also facilitate genetic mapping of quantitative trait loci in humans.
1Department of Physiology and Molecular Medicine, Medical College of Ohio, Toledo, Ohio, USA.
2Correspondence and requests for reprints to Dr Alan Y. Deng, Department of Physiology and Molecular Medicine, Medical College of Ohio, 3035 Arlington Avenue, Toledo, OH 43614-5804, USA. Tel: +1 419 383 4026; fax: +1 419 383 6168; E-mail: email@example.com
Sponsorship: This work was supported by Grants-in-aid from the American Heart Associations (National Center and Ohio Affiliate), and by an American Society of Hypertension/Hoechst Marion Roussel Young Scholars Award.
Received 9 June 1998 Revised 26 August 1998 Accepted 26 August 1998