Gene by environment QTL mapping through multiple trait analyses in blood pressure salt-sensitivity: identification of a novel QTL in rat chromosome 5.
BACKGROUND
The genetic mechanisms underlying interindividual blood pressure variation reflect the complex interplay of both genetic and environmental variables. The current standard statistical methods for detecting genes involved in the regulation mechanisms of complex traits are based on univariate analysis. Few studies have focused on the search for and understanding of quantitative trait loci responsible for gene x environmental interactions or multiple trait analysis. Composite interval mapping has been extended to multiple traits and may be an interesting approach to such a problem.


METHODS
We used multiple-trait analysis for quantitative trait locus mapping of loci having different effects on systolic blood pressure with NaCl exposure. Animals studied were 188 rats, the progenies of an F2 rat intercross between the hypertensive and normotensive strain, genotyped in 179 polymorphic markers across the rat genome. To accommodate the correlational structure from measurements taken in the same animals, we applied univariate and multivariate strategies for analyzing the data.


RESULTS
We detected a new quantitative train locus on a region close to marker R589 in chromosome 5 of the rat genome, not previously identified through serial analysis of individual traits. In addition, we were able to justify analytically the parametric restrictions in terms of regression coefficients responsible for the gain in precision with the adopted analytical approach.


CONCLUSIONS
Future work should focus on fine mapping and the identification of the causative variant responsible for this quantitative trait locus signal. The multivariable strategy might be valuable in the study of genetic determinants of interindividual variation of antihypertensive drug effectiveness.
Soler
Júlia M Pavan
JM
Mathematics and Statistics Institute, University of São Paulo, Brazil. pavan@ime.usp.br
Pereira
Alexandre C
AC
Tôrres
César H
CH
Krieger
José E
JE
D000818:Animals; D001794:Blood Pressure / Q000235:genetics*; D002874:Chromosome Mapping / Q000379:methods*; D033481:Chromosomes, Mammalian; D004777:Environment; D016013:Likelihood Functions; D016014:Linear Models; D008126:Lod Score; D040641:Quantitative Trait Loci; D051381:Rats; D011914:Rats, Inbred BN; D011918:Rats, Inbred SHR; D012965:Sodium Chloride / Q000494:pharmacology*
D012965:Sodium Chloride