Abstract 16461: Genetic Basis of Severe Pulmonary Arterial Hypertension in a Colony of SU5416 “Hyper-responsive” Sprague-dawley Rats

Abstract

Introduction: Our lab has identified a unique sub-strain of Sprague Dawley (SD) rats obtained from a colony of Charles River labs (Montreal, Canada) exhibiting hyper-responsiveness (HR) to the VEGFR2 antagonist, SU5416 (SU). These rats developed severe progressive PAH in response to single injection of SU in absence of CH. In the present study, we investigated genetic basis of hyper-responsive (HR) phenotype in the sub-strain of SD rats. Hypothesis: We hypothesized that hyper-responsiveness to SU was conferred by as yet unknown genetic modifiers that modulate the response to VEFR2 blockade. Methods and Results: Male and female rats were injected with SU (20mg/kg, sc) or vehicle (control). Right ventricular systolic pressure (RVSP) was measured at 7 weeks after SU injection. In absence of CH, 72% (13 of 18) male SD rats demonstrated HR-phenotype and developed severe PAH in response to SU with mean RVSP of 97±18 mmHg; whereas only 27% (7 of 26) of the female rats showed HR-phenotype. Furthermore, crossing non-responsive male and female animals markedly decreased the proportion of HR animals in the F1-generation (HR 15% and 0%. male vs. female, respectively), supporting a possible genetic basis for the HR phenotype. Therefore, we undertook whole genome-wide exome sequencing to identify mutations related to the HR phenotype. This resulted in the identification of a number of mutations unique to the HR SD colony (not found in 40 other background strains) and predicted to have a “high effect” on gene function. Preliminary analysis has identified several candidate genes exhibiting mutations tightly associated with the HR phenotype, including the protein C receptor, hypoxia inducible factor 1α and SP110. These and other potential modifier genes identified by a bioinformatics analysis are currently being validated in a larger population of rats from this SD colony, with and without the HR phenotype. Conclusion: For the first time, we have identified modifier genes that play a critical role in determining susceptibility to development of severe PAH in response to SU alone. These data may provide insight into the nature of potential genetic determinants that may influence the penetrance of the PAH phenotype in humans harboring mutations BMPR2 or in other PAH causing genes.