SCN3B and atrial fibrillation: In the current study, we carried out mutation screening of the SCN3B gene in 355 lone AF patients and found that two patients carried rare variants in 5′UTR (NM_018400.4: c.-324C>A, rs976125894 and NM_018400.4: c.-303C>T, rs1284768362) of SCN3B and our further functional studies revealed that the rare variant c.-324C>A (rs976125894), which is located in the promoter region and enhanced the transcriptional activity, may regulate the expression level of SCN3B through interacting with the GATA4 transcription factor.