1. Linkage studies have revealed quantitative trait loci (QTL) for blood pr
essure in the rat genome using genetic hypertensive rat models. To identify
the genes responsible for hypertension, the construction of congenic rats
is essential.
2. To date, several congenic strains have been obtained from spontaneously
hypertensive or Dahl salt-sensitive rats. The results of these studies shou
ld be interpreted according to whether the rats carry the whole QTL region
or not.
3. After establishing congenic strains, three strategies are possible: (i)
an orthodox positional cloning in which, using sub-congenic strains, the QT
L region is cut down to smaller fragments suitable for physical mapping; (i
i) a positional candidate strategy in which candidate genes in the QTL regi
ons are studied; or (iii) physiological studies in which intermediate pheno
types directly associated with the hypertension gene are explored. Several
other experimental strategies are also available using congenic strains as
new animal models for hypertension.
4. To make the most of advances in DNA technology, the precise evaluation o
f the phenotypic difference between congenic strains carrying different QTL
or between a congenic and parental strain is critical.