Abstract 220: Post-gwas Functional Genomics Analysis Of Abo Locus To Identify Novel Pathogenic Mechanisms For Chronic Thromboembolic Pulmonary Hypertension

Abstract

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare and mysterious complication of pulmonary embolism, characterized by chronic pulmonary arterial thrombosis, occlusions and vasculopathy. Emerging evidence has suggested genetic relevance of CTEPH, particularly to ABO blood type. Genome-wide association study (GWAS) has identified ABO gene as the most significant genetic locus associated with CTEPH. This locus, however, consists only intronic SNPs and there is no mechanistic explanation on how these non-coding SNPs control the risk of CTEPH. Methods: GWAS-identified CTEPH-associated ABO locus was analyzed, and haplotype SNPs were identified based on linkage disequilibrium (LD). Electrophoretic mobility shift assay (EMSA) was applied to screen functional SNPs (fSNPs) based on allele-imbalanced nuclear protein binding. SNP-binding nuclear transcription factors (TFs) were identified by proteomics. Hi-C chromatin-interaction analysis was utilized to determine potential target genes affected by fSNPs. Knockdown of fSNP-associated TFs in human pulmonary artery endothelial cells (hPAECs) was applied to validate the regulation of TFs on target genes. Results: Based on GWAS, the minor allele of tag SNP rs2519093 is associated with higher risk of CTEPH (Odds ratio 2.22). It defines 11 haplotype SNPs in a LD with R 2 > 0.8. Screened by EMSA with hPAEC nuclear proteins, intronic SNPs rs579459 and rs550057 were identified functional given their allele-specific protein binding. Proteomics analysis identified 3 candidate TFs that allele-specifically bind to fSNP rs579459: PBX1, CTCF and SAFB2. Candidate target gene ADAMTS13 is chosen based on its prominent interaction with fSNP revealed by Hi-C analysis, and the potential role in thromboembolism through vWF cleavage. TF knockdown by siRNA downregulates ADAMTS13 in hPAECs, suggesting their regulatory function as activators. Conclusion: Leveraging our post-GWAS functional genomics approach, we identified fSNPs in ABO locus that define a genetic architecture controlling the susceptibility of CTEPH. This genetic architecture, along with the newly identified fSNP-associated TFs and target gene ADAMTS13, provides a biological explanation for the pathogenesis of CTEPH.