{"doi":"10.1101/2020.04.14.039461","title":"Synchronized cardiac impulses emerge from multi-scale, heterogeneous local calcium signals within and among cells of heart pacemaker tissue","abstract":"ABSTRACT Background The current paradigm of Sinoatrial Node (SAN) impulse generation: (i) is that full-scale action potentials (APs) of a common frequency are initiated at one site and are conducted within the SAN along smooth isochrones; and (ii) does not feature fine details of Ca 2+ signalling present in isolated SAN cells, in which small subcellular, subthreshold local Ca 2+ releases (LCRs) self-organize to generate cell-wide APs. Objectives To study subcellular Ca 2+ signals within and among cells comprising the SAN tissue. Methods We combined immunolabeling with a novel technique to detect the occurrence of LCRs and AP-induced Ca 2+ transients (APCTs) in individual pixels (chonopix) across the entire mouse SAN images. Results At high magnification, Ca 2+ signals appeared markedly heterogeneous in space, amplitude, frequency, and phase among cells comprising an HCN4 + /CX43 - cell meshwork. The signalling exhibited several distinguishable patterns of LCR/APCT interactions within and among cells. Apparently conducting rhythmic APCTs of the meshwork were transferred to a truly conducting HCN4 - /CX43 + network of straited cells via narrow functional interfaces where different cell types intertwine, i.e. the SAN anatomical/functional unit. At low magnification, the earliest APCT of each cycle occurred within a small area of the HCN4 meshwork and subsequent APCT appearance throughout SAN pixels was discontinuous. Conclusions We have discovered a novel, microscopic Ca 2+ signalling paradigm of SAN operation that has escaped detection using low-resolution, macroscopic tissue isochrones employed in prior studies: APs emerge from heterogeneous subcellular subthreshold Ca 2+ signals, resembling multiscale complex processes of impulse generation within clusters of neurons in neuronal networks. Condensed abstract By combining immunolabeling with a novel optical technique we detected markedly heterogenous Ca 2+ signals within and among cell clusters of an HCN4 + /CX43 - meshwork in mouse sinoatrial node. These Ca 2+ signals self-organized and transferred, throughout the node, to projections from an HCN4 - /CX43 + network connected to a highly organized, rapidly conducting part of the CX43 + network. Thus, APs emerge from heterogeneous, subthreshold Ca 2+ signaling not detected in low-resolution macroscopic isochrones. Our discovery requires a fundamental paradigm shift from concentric impulse propagation initiated within a leading site, to a multiscale/complex process, resembling the emergence of organized signals from heterogeneous local signals within neuronal networks.","journal":"bioRxiv (Cold Spring Harbor Laboratory)","year":2020,"id":122702,"datarank":0.24141568686511508,"base_score":1.6094379124341003,"endowment":1.6094379124341003,"self_citation_contribution":0.24141568686511508,"citation_network_contribution":0.0,"self_endowment_contribution":0.24141568686511508,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":4,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9467,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2020-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":286635,"name":"Magdalena Juhaszova","orcid":"0000-0001-9571-9541","position":1,"is_corresponding":false},{"id":286636,"name":"Kenta Tsutsui","orcid":"0000-0002-5121-6974","position":2,"is_corresponding":false},{"id":287464,"name":"Christopher Coletta","orcid":null,"position":3,"is_corresponding":false},{"id":286637,"name":"Michael D. Stern","orcid":"0000-0003-4476-7425","position":4,"is_corresponding":false},{"id":286638,"name":"Victor A. Maltsev","orcid":"0000-0002-3832-791X","position":5,"is_corresponding":false},{"id":55700,"name":"Edward G. Lakatta","orcid":"0000-0002-4772-0035","position":6,"is_corresponding":false},{"id":287463,"name":"Rostislav Bychkov","orcid":null,"position":0,"is_corresponding":true}],"reference_count":62,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-18T23:14:55.385653Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}