Herraiz-Martínez, AdelaLlach, AnnaTarifa, CarmenGandía, JorgeJiménez-Sabado, VerónicaLozano-Velasco, EstefaníaSerra, Selma AVallmitjana, AlexanderVázquez Ruiz de Castroviejo, EduardoBenítez, RaúlAranega, AmeliaMuñoz-Guijosa, ChristianFranco, DiegoCinca, JuanHove-Madsen, Leif2023-01-252023-01-252019http://hdl.handle.net/10668/12952Single nucleotide polymorphisms on chromosome 4q25 have been associated with risk of atrial fibrillation (AF) but the exiguous knowledge of the mechanistic links between these risk variants and underlying electrophysiological alterations hampers their clinical utility. Here, we tested the hypothesis that 4q25 risk variants cause alterations in the intracellular calcium homoeostasis that predispose to spontaneous electrical activity. Western blotting, confocal calcium imaging, and patch-clamp techniques were used to identify mechanisms linking the 4q25 risk variants rs2200733T and rs13143308T to defects in the calcium homoeostasis in human atrial myocytes. Our findings revealed that the rs13143308T variant was more frequent in patients with AF and that myocytes from carriers of this variant had a significantly higher density of calcium sparks (14.1 ± 4.5 vs. 3.1 ± 1.3 events/min, P = 0.02), frequency of transient inward currents (ITI) (1.33 ± 0.24 vs. 0.26 ± 0.09 events/min, P  Here, we identify the 4q25 variant rs13143308T as a genetic risk marker for AF, specifically associated with excessive calcium release and spontaneous electrical activity linked to increased SERCA2 expression and RyR2 phosphorylation.enAttribution-NonCommercial 4.0 Internationalhttp://creativecommons.org/licenses/by-nc/4.0/Human atrial myocytesRyanodine receptorSarcoplasmic reticulum calcium releaseSingle nucleotide polymorphismsSpontaneous electrical activityAction PotentialsAgedAtrial FibrillationCalciumCalcium SignalingCase-Control StudiesChromosomes, Human, Pair 4FemaleGenetic Association StudiesGenetic Predisposition to DiseaseHeart AtriaHeart RateHomeostasisHumansMaleMyocytes, CardiacPhenotypePhosphorylationPolymorphism, Single NucleotideRisk FactorsRyanodine Receptor Calcium Release ChannelSarcoplasmic Reticulum Calcium-Transporting ATPasesresearch article30219899open access10.1093/cvr/cvy2151755-3245PMC6383060https://academic.oup.com/cardiovascres/article-pdf/115/3/578/29816419/cvy215.pdfhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC6383060/pdf