Common Genetic Variant Associated With Atrial Fibrillation Lowers Expression of Nesprin-2α1 With Downstream Effects on Nuclear and Electrophysiological Traits.

Background: Atrial fibrillation GWAS (genome-wide association studies) identified significant associations for rs1152591 and linked variants in the gene encoding Nesprin-2, which connects the nuclear membrane with the cytoskeleton.

Methods: Reporter gene vector transfection and CRISPR-Cas9 editing were used to identify the causal variant regulating the expression of . After knockdown or overexpression in human stem cell-derived cardiomyocytes, nuclear phenotypes were assessed by imaging and atomic force microscopy. Gene expression was assessed by RNAseq and gene set enrichment analysis. Fura-2 AM staining assessed calcium transients. Optical mapping assessed action potential duration and conduction velocity.

Results: The risk allele of rs1152591 had lower promoter and enhancer activity and was significantly associated with lower expression of the short isoform in human stem cell-derived cardiomyocytes, without an effect on the expression of the full-length mRNA. overexpression had dominant negative effects on the nucleus with its overexpression or knockdown leading to increased nuclear area and decreased nuclear stiffness. Gene expression results from overexpression demonstrated both concordant and nonconcordant effects with knockdown. overexpression had a gain of function on electrophysiology, leading to significantly faster calcium reuptake and decreased assessed action potential duration, while knockdown showed both shortened assessed action potential duration and decreased conduction velocity.

Conclusions: rs1152591 was identified as a causal atrial fibrillation variant, with the risk allele decreasing expression. Downstream effects of overexpression include changes in nuclear stiffness and electrophysiology, which may contribute to the mechanism for the risk allele's association with AF.