Identification and functional analysis of a KCNA5 mutation responsible for idiopathic atrial fibrillation

Objective To investigate the molecular mechanism of idiopathic atrial fibrillation(AF)associated with KCNA5 mutation.Methods The clinical data and blood samples from 130 unrelated subjects with idiopathic AF were collected and evaluated in contrast to 200 healthy individuals.The coding exons and the flanking introns of KCNA5 gene were amplified by polymerase chain reaction and sequenced using the di-deoxynucleotide chain termination approach to identify potential mutations.Multiple alignment of the KCNA5 encoded protein sequences across species Was performed.The KCNA5 gene wag cloned and the corresponding mutant was acquired by site directed mutagenesis.The recombinant plasmid expressing or tracing KCNA5 Was constructed and transfected into COS-7 cells with Lipofectamine,respectively.The effects of mutated KCNA5 gene on the electrophysiologieal characteristics and subcellular location of encoded ion channel were explored by patch-clamp and confocal microscope,respectively.Results A heterozygous missense KCNA5 mutation.C.1580C＞T was identified in 1 of 130 idiopathic AF patients.Namely,the triplet substitution of ATG for ACG at codon 527.predicting the conversion of threonine into methionine at amino acid residue 527(T527M),was detected.Functional analysis revealed that KCNA5 T527M mutation exerted predominant negative effect on the currents but no effect on the subcellular location of encoded ion channel.Conclusion The heterozygous KCNA5 T527M mutation identified in 1 idiopathic AF patient exerts predominant negative effect on the currents of encoded ion channel,thereby conducing to idiopathic A F. Key words: Atrial fibrillation; Gene; KCNA5; Mutation