biostudies-literatureUnknown2(3)Hou YCa²⁺ sparks constitute the fundamental units of Ca²⁺ release in cardiomyocytes. Here we investigate how ryanodine receptors (RyRs) collectively generate these events by employing a transgenic mouse with a photo-activated label on RyR2. This allowed correlative imaging of RyR localization, by super-resolution Photo-Activated Localization Microscopy, and Ca²⁺ sparks, by high-speed imaging. Two populations of Ca²⁺ sparks were observed: stationary events and "travelling" events that spread between neighbouring RyR clusters. Travelling sparks exhibited up to 8 distinct releases, sourced from local or distal junctional sarcoplasmic reticulum. Quantitative analyses showed that sparks may be triggered by any number of RyRs within a cluster, and that acute β-adrenergic stimulation augments intra-cluster RyR recruitment to generate larger events. In contrast, RyR "dispersion" during heart failure facilitates the generation of travelling sparks. Thus, RyRs cooperatively generate Ca²⁺ sparks in a complex, malleable fashion, and channel organization regulates the propensity for local propagation of Ca²⁺ release.Nature cardiovascular research251-267https://www.ebi.ac.uk/biostudies/studies/S-EPMC7616007biostudies-literatureLive-cell photo-activated localization microscopy correlates nanoscale ryanodine receptor configuration to calcium sparks in cardiomyocytes.PMC7616007Louch WELi JManfra OSjaastad ILe CLaasmaa MJones PPNorden ESZhang LHou YShen XSoeller CfalseLive-cell photo-activated localization microscopy correlates nanoscale ryanodine receptor configuration to calcium sparks in cardiomyocytes.Ca²⁺ sparks constitute the fundamental units of Ca²⁺ release in cardiomyocytes. Here we investigate how ryanodine receptors (RyRs) collectively generate these events by employing a transgenic mouse with a photo-activated label on RyR2. This allowed correlative imaging of RyR localization, by super-resolution Photo-Activated Localization Microscopy, and Ca²⁺ sparks, by high-speed imaging. Two populations of Ca²⁺ sparks were observed: stationary events and "travelling" events that spread between neighbouring RyR clusters. Travelling sparks exhibited up to 8 distinct releases, sourced from local or distal junctional sarcoplasmic reticulum. Quantitative analyses showed that sparks may be triggered by any number of RyRs within a cluster, and that acute β-adrenergic stimulation augments intra-cluster RyR recruitment to generate larger events. In contrast, RyR "dispersion" during heart failure facilitates the generation of travelling sparks. Thus, RyRs cooperatively generate Ca²⁺ sparks in a complex, malleable fashion, and channel organization regulates the propensity for local propagation of Ca²⁺ release.2023-01-01T00:00:00Z2023 Mar2026-06-02T08:33:06.959Z2025-04-07T02:07:27.864ZS-EPMC76160073880336310.1038/s44161-022-00199-2