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A2448 - Spontaneous Mutation in Pituitary Tumor Transforming Gene-1 Contributes to Increased Susceptibility to Severe Pulmonary Arterial Hypertension Induced by SU5416 in Rats
Author Block: K. R. Chaudhary1, Y. Deng1, A. Yang1, K. Rowe1, E. Cuppen2, D. J. Stewart1; 1Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada, 2Department of Medicine, Hubrecht Institute, Utrecht, Netherlands.
Introduction: A previous report from our lab has demonstrated differences in the response of rat strains to SU5416 (SU), a VEGFR2 antagonist. We identified a unique sub-strain of Sprague-Dawley (SD) rats that is hyper-responsive (HR) to SU and developed severe progressive pulmonary arterial hypertension (PAH) in response to single injection of SU, even in absence of hypoxia (Hx). The aim of the present study was to investigate the genetic basis of increased susceptibility to SU in the HR SD rats. Hypothesis: We hypothesized that the HR phenotype is conferred by genetic determinants that potentiate the response to VEGFR2 blockade. Methods and Results: Male and female SD rats (Charles River Labs, Canada) were injected with SU (20 mg/kg) or vehicle. Right ventricular systolic pressure (RVSP) was measured at 7 weeks after SU injection. In absence of Hx, 72% (13 of 18) male and 27% (7 of 26) female rats developed severe PAH in response to SU with mean RVSP of 97±18 mmHg and 101±13 mmHg, respectively. Furthermore, crossing non-responsive male and female animals markedly decreased the proportion of HR animals in the F1-generation (HR: 15% and 0%, male and female, respectively), consistent with a possible genetic basis for the HR phenotype. Using whole genome-wide exome sequencing approach, we identified a number of mutations unique to the HR SD colony. Bioinformatics analysis of the data identified several candidate genes exhibiting mutations tightly associated with the HR phenotype, including the hypoxia inducible factor-1α, SP110, cingulin like-1 and pituitary tumor-transforming gene-1 (PTTG1). Furthermore, we confirmed that the mutation in PTTG1 was present in HR rats only and was absent in other rat strains that did not demonstrate HR phenotype. A colony of PTTG1 mutant rats was generated by selective breeding of PTTG1 mutant rats. Increase in the proportion of SU-HR animals was observed in PTTG1 mutant colony (HR: 94% and 90%, male and female, respectively), compared to parent-generation. A trend towards higher mortality (p=0.08) was also observed in male PTTG1 mutant rats compared to male wild-type littermate. Further, HR SD rats demonstrated significantly greater increase in RVSP and RV hypertrophy in response to 3-week Hx (10% O2) and monocrotaline (40 mg/kg) compared to wild-type SD rats. Conclusion: A previously unrecognized mutation in PTTG1 causes increase in susceptibility to developing severe PAH in rats. These results may provide insight into possible genetic determinants influencing the penetrance of the PAH phenotype in humans harbouring disease-causing mutations.