Abstract 18159: A Functional Variant for Atrial Fibrillation Affects PITX2c Expression by Interacting With TFAP2a
Background: To date, 17 loci associated with atrial fibrillation (AF) have been identified, and there are 4 regions at 4q25 around PITX2 gene strongly associated with AF. However, the functional variants at all known AF loci remain elusive.
Methods and Results: Among the 4 AF loci at 4q25, we focused on one associated region of ~84 kb extending from Chr4: 111,520,926 to 111,604,727 that includes the PITX2 gene itself (defined as all SNPs with r2 > 0.6 from the sentinel SNP rs1448818). To identify potential functional variants, we analyzed DNase hypersensitivity, histone modification and mammalian conservation from ENCODE and Roadmap Epigenomics Project. Additionally, cap analysis of gene expression (CAGE) data was also investigated. We identified 13 candidate regions, 5 of which showed enhancer activity in zebrafish skeletal muscle and heart. Using luciferase assays in a mouse atrial cell line (HL-1), we then identified one SNP (rs2595104) in which the T risk allele was associated with 31% decreased activity compared to the G non-risk allele (p = 0.007). rs2595104 lies ~10 kb upstream of PITX2c transcriptional start site and is in high linkage disequilibrium (LD) (r2 = 0.67) with rs1448818. In silico investigation of rs2595104 using UniPROBE and HaploReg database revealed differential binding of each allele to activating enhancer binding protein 2 alpha (TFAP2a). Electrophoretic mobility shift assays showed that TFAP2a bound robustly to the non-risk G allele at rs2595104 but not to the risk T allele. Chromatin immunopricipitation followed by allele-specific qPCR in human embryonic stem cell-derived cardiomyocytes (hESC-CM) further suggested that TFAP2a was preferentially recruited to the non-risk G allele at rs2595104 in an AF-relevant cell type. hESC-CMs with homozygous deletion of rs2595104-containing enhancer using CRSPR-Cas9 expressed less PITX2c (35 ± 6%, p = 0.036), compared to the wild-type hESC-CMs. Finally, mutating the G allele at rs2595104 to T allele by CRSPR-Cas9 led to 21% reduction in PITX2c level in hESC-CMs (p = 0.027).
Conclusion: We have found that the AF-associated SNP rs2595104 alters PITX2c expression via interaction with TFAP2a. Such a pathway may ultimately contribute to AF susceptibility at the PITX2 locus.
Author Disclosures: J. Ye: None. N.R. Tucker: None. E. Dolmatova: None. P.T. Ellinor: None.
- © 2015 by American Heart Association, Inc.