Endocrine Abstracts

Objective. The aims of our study were to utilise a combination of high fidelity phenotyping, microarray gene expression profiling and conserved synteny mapping between rodent and human genomes to identify genetic determinants underlying human hypertension.
Methods. We used the stroke-prone spontaneously hypertensive rat (SHRSP) and a congenic strain (SP.WKYGla2c*) produced by introgressing a quantitative trait locus responsible for blood pressure regulation on rat chromosome 2 from the normotensive Wistar Kyoto (WKY) reference strain onto the SHRSP background. Genome-wide microarray expression profiling was undertaken to identify differentially expressed genes between parental SHRSP, WKY and congenic strain using total kidney RNA from three replicates of each strain and the rat RG U34 genechips from Affymetrix. Using the global error model a nominal significance level of p<0.05 was taken to be the threshold for differential expression.
Results. Phenotyping with radio-telemetry revealed that systolic and diastolic blood pressures were significantly reduced in the SP.WKY.Gla2c* compared to the SHRSP (198/134 ± 6.1/3.3 vs. 172/120 ± 3.8/3.4; F=15.8/8.1, p=0.0009/0.013). Using microarrays and the global error model we identified two genes that were differentially expressed. Of these glutathione S-transferase mu type 2 (Gstm2) was most significantly reduced. Quantitative RT-PCR relative to a beta-Actin standard confirmed the microarray results with SHRSP mRNA at 8.56 x10-4 ± 1.6 x10-4 compared to SP.WKYGla2c* 3.67 x10-3 ± 2.8 x10-4; (95%CI -3.9 x10-3, -1.8x10-3; p = 0.0034) and WKY 4.03 x10-3 ± 5.1 x10-4; (95%CI -5.4 x10-3, -8.9x10-4; p = 0.027).
Conclusions. We have isolated a region on rat chromosome 2, including Gstm2 a gene involved in the defence against oxidative stress and may be responsible for blood pressure regulation in this model. The congenic region shows conserved synteny with human chromosome 1p13-1q22 and therefore identifies a human ortholog GSTM2 as a new positional and functional candidate for human hypertension.