Impact of genes in the PITX2 locus on the electrophysiology of human atrial induced pluripotent stem cell-derived cardiomyocytes

• Applicants: Privatdozent Dr. Torsten Christ; Professor Dr. Thomas Eschenhagen; Professorin Dr. Monika Stoll
• Subject Area: Pharmacology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 518522837

Atrial fibrillation (AF) is the most common arrhythmia and affects around 1% of the population with increasing incidence and substantial morbidity. Understanding the pathophysiology of human AF has been one of the main research goals in cardiac electrophysiology during the last two decades. Most in vitro studies were performed with isolated atrial tissues/cells obtained from patients during open-heart surgery. However, these tissues are almost exclusively obtained from elderly patients in whom AF is persistent or permanent and often secondary to structural heart disease. Thus, the standard experimental material does not represent well the pathophysiologically most interesting group of younger people with early forms of paroxysmal or lone AF that often develop early-onset AF in the absence of structural heart disease. Genome wide association studies (GWAS) have identified several gene variants associated with AF. The strongest association was found with single nucleotide polymorphisms (SNP) in a gene locus near the PITX2 gene. The effect size is comparably large, and the original finding has been several times replicated, making the association between the PITX2 gene locus and AF one of the strongest in medicine. However, as with the majority of GWAS hits, the AF-associated SNPs fall in a so-called gene desert and not in the PITX2 gene itself. Other neighboring genes have been discovered in the same locus after the initial GWAS linking AF to the PITX2 locus. Support for a role of PITX2 comes from heterozygous PITX2-KO mouse models. However, the translation to the human situation is not trivial. First, atrial electrophysiology differs substantially between mice and humans. In order to address this issue, we established a PITX2-KO in atrial human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). Engineered heart tissues (EHT) from this line shows a surprisingly “AF-like” electrophysiological phenotype and forms the basis of our proposed project. Second, while early studies suggested lower PITX2 transcript abundance in human atria of patients with SNPs close to PITX2, a larger study did not reproduce this association in 239 left atrial samples from patients with or without AF. In contrast, a gene close to PITX2, the ENPEP-AS1 showed an assoziation with AF. This finding opens the possibility that changes in genes close to PITX2 but not PITX2-expression associate with AF. Gene editing of the ENPEP-AS1 in WT and PITX2-KO atrial hiPS-CM cell line should allow to answer the question. The proposed study should help to understand if SNP in the PITX2 locus affect human atrial electrophysiology via genes close to PITX2.

• DFG Programme: Research Grants