Identification and Functional Investigation of SOX4 as a Novel Gene Underpinning Familial Atrial Fibrillation

<b>Background:</b> Atrial fibrillation (AF) signifies the most prevalent supraventricular arrhythmia in humans and may lead to cerebral stroke, cardiac failure, and even premature demise. Aggregating strong evidence points to genetic components as a cornerstone in the etiopathogenesis of familial AF. However, the genetic determinants for AF in most patients remain elusive. <b>Methods:</b> A 4-generation pedigree with idiopathic AF and another cohort of 196 unrelated patients with idiopathic AF as well as 278 unrelated healthy volunteers were recruited from the Chinese population of Han ethnicity. A family-based whole-exome sequencing examination followed by a Sanger sequencing assay in all research subjects was implemented. The functional impacts of the identified <i>SOX4</i> mutations were explored via a dual-reporter assay. <b>Results:</b> Two new heterozygous <i>SOX4</i> mutations, NM_003107.3: c.211C>T; p.(Gln71*) and NM_003107.3: c.290G>A; p.(Trp97*), were observed in the family and 1 of 196 patients with idiopathic AF, respectively. The two mutations were absent in the 278 control individuals. The biochemical measurements revealed that both Gln71*- and Trp97*-mutant SOX4 failed to transactivate <i>GJA1 (Cx43)</i>. Moreover, the two mutations nullified the synergistic activation of <i>SCN5A</i> by SOX4 and TBX5. <b>Conclusions:</b> The findings first indicate <i>SOX4</i> as a gene predisposing to AF, providing a novel target for antenatal genetic screening, individualized prophylaxis, and precision treatment of AF.