Recent advances in the genetics of atrial fibrillation: from rare and common genetic variants to microRNA signaling

Besides traditional risk factors, atrial fibrillation (AF) also shares a strong genetic component. Here, we review the genetics of AF including monogenic forms of AF, heritability of AF, complex genetic risk of AF, and the role of microRNAs in AF pathophysiology. Thirtytwo mutations (17 genes) have been reported to cause familial AF. Mutations in cardiac ion channel genes or their subunits alter electrical properties and thereby lead to AF. Recently, also non-ion channel gene mutations have been identified to cause familial AF. Twin and community-based studies suggested AF to be heritable also on the population level. The AF risk in the offspring of an affected first-degree relative ranged between 2- to 5-fold, depending on the age of onset. Thereby, the risk of AF increases gradually the earlier the youngest relative of an AF patient developed the arrhythmia. African Americans bear a lesser risk of AF compared to individuals of European ancestry. Their risk rises with increasing European admixture. Genome wide association studies have revealed loci on chromosomes 4q25, 16q21 and 1q21 conferring risk of AF. Very recently, another consortial effort has identified a novel locus on chromosome 1, intronic to IL6R. IL6R encodes the a subunit of the interleukin 6 receptor. MicroRNAs were shown to regulate gene expression, and are increasingly reported to modify AF. A hallmark of AF pathophysiology is electrical and structural remodeling. MicroRNAs are involved in this process by regulating gene expression of cardiac ion channels, calcium handling proteins, transcription factors, and extracellular matrix related proteins.