Abstract P044: Pleiotropic Effect of a <42.5 kb QTL Region on Rat Chromosome 10 Regulating Blood Pressure and Tumorigenesis

Abstract

This study is focused on a translationally significant, GWAS locus for cardiovascular disease (QT-interval) on human chromosome 17. We have already validated and high resolution mapped the homologous genomic segment of this human locus to <42.5 kb on rat chromosome 10. The locus in rats regulates both QT-interval and blood pressure and contains a single protein-coding gene, rififylin (Rffl). While there are no exonic variants, the expression of Rffl is differential between Dahl S and S.LEW congenic rats, which are strains used for mapping this locus. A previous study points to altered rate of endocytic recycling as the underlying mechanism, through which Rffl operates to control both cardiac QT-intervals and blood pressure. Rffl also contributes to tumorigenesis by negatively regulating caspases and tumor suppressor genes. Moreover, the expression of Methyl-CpG Binding Domain Protein 2 (Mbd2) is also differential between Dahl S and S.LEW congenic rats and Mbd2 can mediate the repression of methylated tumor suppressor genes. Therefore, we hypothesized that the higher expression of Rffl and Mbd2 render the S.LEW congenic strain more susceptible to tumor development. To compare the tumor susceptibility between S and S.LEW congenic strain, azoxymethane (AOM)-induced colon tumorigenesis was assessed. The number of colon tumors was significantly higher in the congenic strain compared with the S rat (p<0.01). Interestingly, the incidence of another phenotype, polyarteris nodosa (PAN), was also higher in the congenic strain. However, the identity of the quantitative trait nucleotides that regulates the expression of Rffl and Mbd2 is unknown. A novel long non-coding RNA (lncRNA), which we refer to as Rffl-lnc1, was identified within the rat Rffl 5’UTR intron locus. Compared to the S rat, the Lewis alleles of Rffl-lnc1 are polymorphic, with a large 19bp deletion. To further assess the role of Rffl-lnc1, the CRISPR/Cas9 system has been successfully applied to construct a Rffl-lnc1 knock-out model of the S rat and a 19bp knock-in rescue model of the S.LEW congenic strain. Functional evaluation of these targeted disruption and rescue models is underway to test the physiological role of Rffl-lnc1 and the 19bp polymorphism in regulating blood pressure and tumorigenesis.