{"gene":"PKP2","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2003,"finding":"C-TAK1 (Cdc25C-associated kinase 1) phosphorylates PKP2, generating a 14-3-3-binding site that influences PKP2 subcellular localization. This was established using mutational analysis of C-TAK1 binding motifs and in vivo phosphorylation assays, identifying PKP2 as a novel C-TAK1 substrate.","method":"Mutational approach disrupting C-TAK1 binding, in vivo phosphorylation assays, 14-3-3 binding site mapping","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with mutagenesis plus in vivo validation of 14-3-3 binding site and localization, single lab but multiple orthogonal methods","pmids":["12941695"],"is_preprint":false},{"year":2008,"finding":"ARVC-associated truncation mutants of PKP2 (R79x and 179fs) fail to localize to sites of cell-cell apposition in neonatal rat ventricular myocytes. Early truncation at position 79 prevents physical interaction of PKP2 with both desmoplakin (DP) and connexin-43 (Cx43), and R79x expression reduced Cx43 abundance and correlated with loss of HSP90 expression.","method":"Adenoviral expression of mutant PKP2 constructs in neonatal rat ventricular myocytes, co-immunoprecipitation, immunofluorescence localization","journal":"Heart rhythm","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP and localization in primary cardiomyocytes with two PKP2 mutants, single lab with multiple readouts","pmids":["19084810"],"is_preprint":false},{"year":2016,"finding":"Expression of truncated PKP2 (PKP2-Ser329) in transgenic mice causes dose-dependent reduction and remodeling of desmosomal proteins (Desmocollin-2, Plakoglobin, native PKP2, Desmin, β-Catenin) and electrical coupling proteins (Connexin 43, Nav1.5), establishing that truncated PKP2 disrupts the molecular composition of the intercalated disc.","method":"Transgenic mouse model with truncated PKP2, immunofluorescence, western blot, echocardiography, electrophysiology","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo transgenic model with dose-dependent readouts and multiple molecular endpoints, single lab","pmids":["27412010"],"is_preprint":false},{"year":2017,"finding":"PKP2 is a direct transcriptional target of the Wnt/β-catenin pathway, induced via three TCF binding sites in the PKP2 gene promoter and one in an enhancer 20 kb upstream of the transcription start site. Furthermore, Plakophilin-2 antagonizes Wnt/β-catenin transcriptional activity in HEK-293T cells, suggesting it acts as an intracellular feedback inhibitor of the pathway.","method":"Transcriptomic analysis, reporter assays, ChIP or promoter binding site analysis in normal and colon cancer-associated fibroblasts, HEK-293T overexpression assay","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay with defined binding sites plus functional antagonism assay, single lab with two orthogonal methods","pmids":["29044515"],"is_preprint":false},{"year":2021,"finding":"PRMT1 methylates PKP2 at an arginine residue; methylated PKP2 stabilizes β-catenin by recruiting USP7, which then induces LIG4 expression and promotes non-homologous end-joining (NHEJ) DNA repair, thereby driving radiation resistance in lung cancer cells.","method":"CRISPR/Cas9 library screen, mass spectrometry identification of arginine methylation, co-immunoprecipitation, functional assays of NHEJ repair, pharmacologic inhibition of PRMT1","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mass spectrometry confirmed PTM, Co-IP for complex, functional rescue experiments, single lab with multiple orthogonal methods","pmids":["33742119"],"is_preprint":false},{"year":2022,"finding":"PKP2 deficiency in cardiomyocytes causes loss of nuclear envelope integrity, which leads to DNA damage and excess oxidant production (superoxide and H2O2) under baseline and mechanical stress conditions. PKP2-deficient cells release H2O2 extracellularly, causing DNA damage in neighboring myocytes in a paracrine manner. Early transcriptional downregulation of electron transport chain proteins precedes left ventricular dysfunction.","method":"High-resolution mass spectrometry, RNA sequencing, transmission electron microscopy of ARVC patient biopsies; multiple imaging and biochemical techniques in cardiac-specific Pkp2 knockout mice and PKP2-deficient hiPSC-derived cardiomyocytes","journal":"Circulation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (proteomics, transcriptomics, TEM, biochemistry) replicated across patient biopsies, mouse KO, and hiPSC-CMs in the same study","pmids":["35959657"],"is_preprint":false},{"year":2021,"finding":"In adult cardiac myocytes, PKP2 transcript abundance is transcriptionally linked to genes coding for inflammatory/immune response molecules. Loss of PKP2 in cardiomyocytes (PKP2cKO mice) upregulates a large set of transcripts associated with inflammatory/immune pathways, inversely correlated with PKP2 abundance in human cardiac transcriptomes.","method":"Cardiac-specific tamoxifen-activated PKP2-knockout mice crossed with RiboTag line; cardiomyocyte-specific ribosome-resident transcriptome profiling; GTEx human transcriptome correlation analysis","journal":"Frontiers in physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cardiomyocyte-specific KO with translating ribosome affinity purification plus human transcriptome cross-validation, single lab","pmids":["33536940"],"is_preprint":false},{"year":2023,"finding":"AAV-mediated delivery of PKP2 in PKP2 mutant iPSC-derived cardiomyocytes restored junctional protein levels (which were reduced by the mutation), improved sodium conduction (rescuing arrhythmic substrate), and enhanced contractile function. In heterozygous Pkp2 knock-in mice, AAV9-PKP2 prevented cardiac dysfunction at 12 months, confirming restoration of desmosomal integrity and cardiac function in vivo.","method":"AAV transduction of PKP2c.2013delC/WT iPSC-derived cardiomyocytes, engineered human myocardium, heterozygous Pkp2c.1755delA knock-in mice; electrophysiology, contractility assays, immunostaining of junctional proteins","journal":"Nature cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic rescue in hiPSC-CMs and in vivo mouse model with multiple functional and molecular endpoints, replicated across systems","pmids":["38665939"],"is_preprint":false},{"year":2024,"finding":"AAV9-mediated restoration of PKP2 in cardiac-specific Pkp2 knockout mice rescues desmosome and gap junction structure, prevents right ventricular dilation, reduces ventricular arrhythmias, and reverses adverse fibrotic remodeling. RNA sequencing shows AAV9:PKP2 causes broad correction of PKP2-associated transcriptional networks beyond desmosomes.","method":"AAV9 gene delivery in cardiac-specific Pkp2 KO mice; echocardiography, electrocardiography, histology, RNA sequencing","journal":"Communications medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO rescue with multiple functional, structural, and transcriptomic endpoints in a single rigorous study","pmids":["38499690"],"is_preprint":false},{"year":2025,"finding":"In exercise-trained PKP2-deficient (PKP2cKO) cardiomyocytes, the pool of sarcolemmal β1-adrenergic receptors (β1-ARs) is decreased compared with exercise-trained controls (where it increases). Intracellular (dyad-associated) β1-ARs remain available in trained PKP2cKO myocytes, as shown by OCT3 knockdown that abolished norepinephrine (non-membrane-permeable) response but not isoproterenol (membrane-permeable) response. Additionally, sympathetic nerve terminal abundance and distribution are heterogeneous in trained PKP2cKO hearts.","method":"Expansion microscopy and structured illumination microscopy of β1-ARs; shRNA knockdown of OCT3; Ca2+ transient dynamics with isoproterenol vs norepinephrine; sympathetic terminal distribution imaging","journal":"Heart rhythm","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple imaging modalities with genetic knockdown confirmation, single lab","pmids":["40383179"],"is_preprint":false},{"year":2024,"finding":"PKP2 is a direct target of miR-7-5p; overexpression of miR-7-5p reduces PKP2 protein levels and enhances radiosensitivity in A549 NSCLC cells by increasing DNA damage (γ-H2AX foci) and inhibiting NHEJ repair. Overexpression of PKP2 rescues the radiosensitizing effects of miR-7-5p, confirming the miR-7-5p/PKP2 regulatory axis.","method":"Clonogenic assays, CCK-8 assays, immunofluorescence (γ-H2AX), western blotting, reporter gene assays (luciferase 3'UTR validation)","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct reporter assay plus functional rescue with PKP2 overexpression, single lab with multiple orthogonal methods","pmids":["40374728"],"is_preprint":false},{"year":2025,"finding":"PKP2 deficiency in cardiomyocytes disrupts oxidative phosphorylation (OXPHOS) gene expression through reduced PPARGC1A (PGC1α) expression, leading to decreased mitochondrial spare capacity in PKP2 mutant hiPSC-CMs and explanted human hearts. Induction of PPARGC1A expression partially restored OXPHOS component expression and improved contractility in PKP2 mutant cells.","method":"RNA sequencing of hiPSC-CMs and human explanted hearts; mitochondrial spare capacity (Seahorse) assay; PPARGC1A overexpression rescue experiments","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transcriptomic plus functional metabolic assay with rescue experiment, single lab, preprint not peer-reviewed","pmids":[],"is_preprint":true},{"year":2025,"finding":"PKP2 deficiency in cardiomyocytes causes impaired lipid homeostasis, glycolysis, and glucose oxidation, with specific metabolic defects linked to poor contractility of cardiomyocytes. AAV9:PKP2 restoration improved contractility, electrophysiological properties, and Ca2+ transients, while pharmacologic metabolic enhancers improved contractility but not electrophysiology, indicating differential sensitivity of PKP2-dependent functions to metabolic perturbation.","method":"Steady-state metabolomics in PKP2-deficient mouse hearts and hiPSC-CMs; AAV9:PKP2 gene rescue; pharmacologic metabolic enhancement; contractility and Ca2+ transient measurement","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — metabolomics plus functional rescue in two model systems, single lab, preprint not peer-reviewed","pmids":[],"is_preprint":true},{"year":2025,"finding":"Loss of PKP2 expression specifically in cardiomyocytes (PKP2cKO) is sufficient to induce senescence-associated heterochromatin foci (SAHFs), p21 staining, and senescence-associated secretory phenotype (SASP) cytokines in neighboring non-myocyte cardiac resident cells, as well as premature epigenetic aging of the heart.","method":"Conventional and multiplex imaging, cytokine arrays, epigenetic clocks, spatial transcriptomics, expansion and structured illumination microscopy in cardiac-specific PKP2 KO mice","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cardiomyocyte-specific KO with multiple orthogonal senescence readouts, single lab, preprint","pmids":[],"is_preprint":true},{"year":2025,"finding":"CASK (calcium/calmodulin-dependent serine protein kinase) negatively regulates PKP2 localization at intercalated discs; CASK knockdown increases PKP2 accumulation at cell contacts and promotes desmosome-like structure formation. In PKP2+/- hiPSC-CMs, CASK expression is increased, and CASK depletion rescues PKP2 accumulation at contacts and improves stress resistance.","method":"AAV-mediated CASK knockdown in neonatal rat hearts, high-resolution imaging, proteomics, electron microscopy, mechano-SICM in NRVM and PKP2+/- hiPSC-CMs","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple imaging modalities and functional assays across multiple model systems, single lab, preprint","pmids":[],"is_preprint":true},{"year":2025,"finding":"PKP2 is a dynamic protein at the intercalated disc of cardiomyocytes whose membrane recruitment is tension-dependent. Proximity labeling mass spectrometry identified PKP2 among the most abundant proteins shared between the DSG2 and N-cadherin interactomes in cardiomyocytes, establishing PKP2 as a component of the intercalated disc macromolecular complex.","method":"Proximity labeling (BioID/TurboID) combined with quantitative mass spectrometry in cultured neonatal cardiomyocytes; tension-dependence assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proximity labeling MS interactome with functional tension-dependence validation, single lab, preprint","pmids":[],"is_preprint":true},{"year":2025,"finding":"PKP2 deficiency in epicardium-derived cells (EPDCs) facilitates emergence of a pro-inflammatory, senescence-associated secretory phenotype (SASP) fibroblast population; however, cardiomyocyte involvement is required for ACM pathogenesis, as EPDC-specific Pkp2 deletion alone does not elicit a pathological phenotype. B-cell depletion delays early inflammatory and fibrosis response in Pkp2-deficient hearts.","method":"Tissue-specific tamoxifen-inducible Cre transgenic mice (cardiomyocyte-specific, EPDC-specific, and combined KO); single-cell RNA sequencing; flow cytometry; immunohistochemistry; antibody-mediated B-cell depletion","journal":"Circulation. Heart failure","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis across three tissue-specific KO lines with scRNAseq and functional depletion experiments, single lab","pmids":["42246055"],"is_preprint":false},{"year":2025,"finding":"PKP2 deficiency in iPSC-derived epicardial cells (hPSC-EPCs) causes enhanced epithelial-to-mesenchymal transition, increased lipid accumulation, and a fibrotic phenotype. RNA-seq of ACM hPSC-EPCs reveals dysregulation of Wnt, interferon, and Rho GTPase signaling, upregulation of IGF2 and the adipogenic transcription factor CEBPA. Recombinant IGF2 treatment of control and PKP2KO hPSC-EPCs enhanced CEBPA expression, implicating IGF signaling in fatty-fibro remodeling.","method":"iPSC differentiation into epicardial cells, CRISPR/Cas9 KO and patient-derived mutant lines, RNA-seq, lipid accumulation assays, recombinant IGF2 treatment","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isogenic CRISPR KO and patient lines with transcriptomic and functional assays plus pathway rescue, single lab","pmids":["41145823"],"is_preprint":false},{"year":2025,"finding":"AAV9-PKP2 gene therapy in Pkp2-knockout rats attenuated cardiac fibrosis by inducing phenotypic conversion of activated profibrotic cardiac fibroblasts into quiescent antifibrotic states, with Ptprc (protein tyrosine phosphatase receptor type C) identified as a key regulator of this reprogramming via single-cell RNA sequencing.","method":"Pkp2-knockout rat model, AAV9-PKP2 delivery, single-cell RNA sequencing, fibroblast phenotyping, bioinformatics","journal":"MedComm","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO rescue with scRNAseq mechanistic endpoint, single lab","pmids":["40979216"],"is_preprint":false},{"year":2026,"finding":"A PKP2 frameshift mutation (c.1125_1132del, paternal) causes nuclear aggregation of the truncated PKP2 protein (aberrant localization confirmed by immunofluorescence), while a splice-site variant (c.224-3 C>G, maternal) causes exon 2 skipping and protein truncation. Both defects synergistically disrupt desmosomal integrity in cardiomyocytes via biallelic inactivation.","method":"MiniGene splicing assays, RT-PCR splice validation, immunofluorescence microscopy of subcellular localization, cycloheximide chase for protein stability","journal":"Functional & integrative genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional splicing assay plus protein localization imaging with stability assay, single lab with multiple methods","pmids":["41535644"],"is_preprint":false}],"current_model":"PKP2 encodes plakophilin-2, a desmosomal scaffold protein at the cardiac intercalated disc whose membrane recruitment is tension-dependent; it is phosphorylated by C-TAK1 to generate a 14-3-3-binding site controlling its localization, physically interacts with desmoplakin and connexin-43, and maintains the molecular integrity of gap junctions and sodium channels (Nav1.5) — loss of PKP2 disrupts desmosomal and electrical remodeling, causes nuclear envelope loss with consequent DNA damage and excess oxidant production, downregulates oxidative phosphorylation via PGC1α, drives transcriptional upregulation of inflammatory/immune pathways in cardiomyocytes, and induces paracrine senescence in neighboring non-myocytes, collectively establishing arrhythmogenic cardiomyopathy substrate."},"narrative":{"mechanistic_narrative":"PKP2 encodes plakophilin-2, a dynamic scaffold protein of the cardiomyocyte intercalated disc whose tension-dependent membrane recruitment integrates it into the desmosomal macromolecular complex shared between the DSG2 and N-cadherin interactomes. PKP2 physically bridges desmosomal and electrical machinery, interacting with desmoplakin and connexin-43; ARVC-associated truncation mutants fail to reach cell-cell junctions and lose these interactions, reducing Cx43 abundance [PMID:19084810], while truncated PKP2 in vivo causes dose-dependent remodeling of desmosomal components (desmocollin-2, plakoglobin, desmin, β-catenin) and the conduction proteins Cx43 and Nav1.5 [PMID:27412010]. Its localization is controlled by post-translational and regulatory inputs: C-TAK1 phosphorylates PKP2 to create a 14-3-3-binding site governing subcellular distribution [PMID:12941695], and CASK negatively regulates its accumulation at intercalated discs. Beyond junctional architecture, PKP2 loss in cardiomyocytes triggers a broad pathological cascade — loss of nuclear envelope integrity with DNA damage and paracrine H2O2-driven oxidant production [PMID:35959657], downregulation of oxidative phosphorylation via reduced PPARGC1A/PGC1α, transcriptional upregulation of inflammatory/immune pathways [PMID:33536940], and induction of senescence in neighboring non-myocytes — collectively establishing the arrhythmogenic cardiomyopathy substrate. PKP2 mutations cause arrhythmogenic cardiomyopathy, and AAV-mediated PKP2 restoration rescues junctional protein levels, sodium conduction, contractility, and adverse fibrotic and transcriptional remodeling in mutant iPSC-cardiomyocytes and in vivo [PMID:38665939, PMID:38499690]. In a distinct context, PKP2 acts in tumor cells as a Wnt/β-catenin target and feedback antagonist [PMID:29044515] and, when methylated by PRMT1, stabilizes β-catenin to promote NHEJ-mediated DNA repair and radiation resistance [PMID:33742119].","teleology":[{"year":2003,"claim":"Established the first post-translational control point for PKP2 localization, showing its membrane targeting is a regulated rather than constitutive property.","evidence":"C-TAK1 binding-motif mutagenesis and in vivo phosphorylation assays mapping a 14-3-3-binding site","pmids":["12941695"],"confidence":"High","gaps":["Did not address the cardiac intercalated-disc context","Functional consequence of altered localization on junction assembly not tested"]},{"year":2008,"claim":"Connected ARVC truncation mutations to a molecular mechanism by showing they prevent junctional targeting and loss of binding to desmoplakin and connexin-43.","evidence":"Adenoviral expression of PKP2 truncation mutants in neonatal rat ventricular myocytes with Co-IP and immunofluorescence","pmids":["19084810"],"confidence":"Medium","gaps":["Two mutants only; broader mutational spectrum untested","Co-IP without reciprocal or structural validation of the interaction interface"]},{"year":2016,"claim":"Demonstrated in vivo that truncated PKP2 disrupts the entire intercalated-disc protein composition, linking a single defective subunit to coordinated desmosomal and electrical remodeling.","evidence":"Transgenic mouse expressing truncated PKP2 with immunofluorescence, western blot, echocardiography and electrophysiology","pmids":["27412010"],"confidence":"Medium","gaps":["Dominant-negative vs haploinsufficiency mechanism not resolved","Order of molecular events leading to disc disassembly unclear"]},{"year":2017,"claim":"Placed PKP2 within Wnt/β-catenin signaling as both a transcriptional target and a feedback antagonist, extending its role beyond structural scaffolding.","evidence":"Reporter assays with mapped TCF binding sites and functional antagonism in HEK-293T and fibroblast systems","pmids":["29044515"],"confidence":"Medium","gaps":["Relevance to cardiomyocyte biology not addressed","Mechanism of β-catenin antagonism not defined"]},{"year":2021,"claim":"Revealed a cancer-cell function in which PRMT1-methylated PKP2 stabilizes β-catenin and promotes NHEJ DNA repair, driving radiation resistance.","evidence":"CRISPR screen, mass-spectrometry detection of arginine methylation, Co-IP and NHEJ functional assays in lung cancer cells","pmids":["33742119"],"confidence":"Medium","gaps":["Methylated arginine residue's structural role unmapped","Whether this axis operates in cardiomyocytes unknown"]},{"year":2021,"claim":"Linked PKP2 abundance to suppression of inflammatory/immune transcriptional programs in cardiomyocytes, defining a non-structural consequence of PKP2 loss.","evidence":"Cardiomyocyte-specific tamoxifen-inducible KO with RiboTag translatome profiling and GTEx cross-validation","pmids":["33536940"],"confidence":"Medium","gaps":["Mechanism linking PKP2 loss to inflammatory transcription not defined","Causal contribution to disease vs bystander effect unresolved"]},{"year":2022,"claim":"Identified nuclear envelope disruption, DNA damage, and paracrine oxidant production as early consequences of PKP2 loss, expanding the disease model from junctional to nuclear/metabolic dysfunction.","evidence":"Proteomics, RNA-seq, TEM across ARVC biopsies, cardiac-specific Pkp2 KO mice and PKP2-deficient hiPSC-CMs","pmids":["35959657"],"confidence":"High","gaps":["Mechanistic link between a disc protein and nuclear envelope integrity unresolved","How H2O2 propagates damage to neighboring cells not fully defined"]},{"year":2023,"claim":"Provided proof-of-concept that PKP2 gene supplementation reverses arrhythmic and contractile substrate, establishing PKP2 deficiency as causal and correctable.","evidence":"AAV transduction of mutant iPSC-CMs, engineered human myocardium, and heterozygous Pkp2 knock-in mice with electrophysiology and contractility readouts","pmids":["38665939"],"confidence":"High","gaps":["Durability and dosing window in human disease unaddressed","Whether nuclear/metabolic defects are also rescued not tested here"]},{"year":2024,"claim":"Showed AAV9-PKP2 corrects structure, arrhythmia, fibrosis, and broad transcriptional networks in vivo, demonstrating systemic reversibility beyond desmosomes.","evidence":"AAV9 delivery in cardiac-specific Pkp2 KO mice with echocardiography, ECG, histology and RNA-seq","pmids":["38499690"],"confidence":"High","gaps":["Mechanism of transcriptional network normalization not dissected","Reversibility of established late-stage fibrosis unclear"]},{"year":2025,"claim":"Defined PKP2 as a tension-dependent dynamic disc component within the DSG2/N-cadherin interactome, anchoring its scaffolding role in mechanobiology.","evidence":"Proximity-labeling mass spectrometry and tension-dependence assays in neonatal cardiomyocytes (preprint)","pmids":[],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Molecular sensor of tension upstream of PKP2 recruitment unknown"]},{"year":2025,"claim":"Identified CASK as a negative regulator of PKP2 junctional accumulation, adding a counter-regulatory input whose dysregulation contributes to mutant phenotypes.","evidence":"AAV CASK knockdown in neonatal rat hearts, imaging, proteomics, EM and mechano-SICM in NRVM and PKP2+/- hiPSC-CMs (preprint)","pmids":[],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Direct vs indirect mechanism of CASK action on PKP2 not resolved"]},{"year":2025,"claim":"Extended PKP2 disease biology to metabolic failure, showing PGC1α-dependent OXPHOS suppression and impaired substrate handling that limit contractility.","evidence":"RNA-seq, Seahorse respirometry, metabolomics and PPARGC1A/AAV9 rescue in hiPSC-CMs, mouse and human hearts (preprints)","pmids":[],"confidence":"Medium","gaps":["Preprints, not peer-reviewed","How PKP2 loss represses PPARGC1A mechanistically is unknown"]},{"year":2025,"claim":"Established that PKP2 loss in cardiomyocytes drives paracrine senescence and premature epigenetic aging of cardiac non-myocytes.","evidence":"Multiplex imaging, cytokine arrays, epigenetic clocks and spatial transcriptomics in cardiac-specific PKP2 KO mice (preprint)","pmids":[],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Signal mediating cardiomyocyte-to-non-myocyte senescence not identified"]},{"year":2025,"claim":"Used tissue-specific epistasis to show cardiomyocyte PKP2 loss is required for ACM pathogenesis while EPDC loss alone is insufficient, and implicated B cells in early inflammation.","evidence":"Cardiomyocyte-, EPDC-, and combined-specific inducible KO mice with scRNA-seq, flow cytometry and B-cell depletion","pmids":["42246055"],"confidence":"Medium","gaps":["Cell-type crosstalk mediating EPDC SASP not defined","B-cell antigen and mechanism of recruitment unknown"]},{"year":2025,"claim":"Linked epicardial PKP2 loss to fatty-fibrotic remodeling through EMT, IGF2/CEBPA-driven adipogenesis and Wnt/interferon/Rho dysregulation.","evidence":"iPSC-derived epicardial cells (CRISPR KO and patient lines), RNA-seq, lipid assays and recombinant IGF2 treatment","pmids":["41145823"],"confidence":"Medium","gaps":["In vivo relevance of IGF2/CEBPA axis untested","Connection to cardiomyocyte-required pathogenesis unresolved"]},{"year":2025,"claim":"Showed AAV9-PKP2 reverses fibrosis by reprogramming activated fibroblasts to quiescent states, identifying Ptprc as a regulator of this conversion.","evidence":"Pkp2-KO rat model with AAV9-PKP2 delivery and single-cell RNA sequencing of fibroblast states","pmids":["40979216"],"confidence":"Medium","gaps":["Direct role of Ptprc not functionally validated","Whether fibroblast reprogramming is PKP2-cell-autonomous unclear"]},{"year":2026,"claim":"Defined biallelic loss-of-function mechanisms in patients, showing distinct mutations (nuclear aggregation vs exon skipping) synergize to inactivate PKP2 and disrupt desmosomal integrity.","evidence":"MiniGene splicing assays, RT-PCR, immunofluorescence localization and cycloheximide chase","pmids":["41535644"],"confidence":"Medium","gaps":["Functional cardiac phenotype not directly assessed","Generalizability beyond this kindred unknown"]},{"year":null,"claim":"The molecular link connecting a junctional scaffold protein to nuclear envelope integrity, PGC1α-dependent metabolism, and paracrine senescence remains undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No mechanism connecting PKP2 loss to PPARGC1A repression","Signal driving non-myocyte senescence unidentified","Tension-sensing machinery upstream of PKP2 recruitment unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[15,2,1]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,15]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[3]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,15,2]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4,19]}],"pathway":[{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[1,2,15]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,17]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[4,10]}],"complexes":["intercalated disc","desmosome"],"partners":["DSP","GJA1","DSG2","CDH2","CTNNB1","CASK","PRMT1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q99959","full_name":"Plakophilin-2","aliases":[],"length_aa":881,"mass_kda":97.4,"function":"A component of desmosome cell-cell junctions which are required for positive regulation of cellular adhesion (PubMed:25208567). Regulates focal adhesion turnover resulting in changes in focal adhesion size, cell adhesion and cell spreading, potentially via transcriptional modulation of beta-integrins (PubMed:23884246). Required to maintain gingival epithelial barrier function (PubMed:34368962). Important component of the desmosome that is also required for localization of desmosome component proteins such as DSC2, DSG2 and JUP to the desmosome cell-cell junction (PubMed:22781308, PubMed:25208567). Required for the formation of desmosome cell junctions in cardiomyocytes, thereby required for the correct formation of the heart, specifically trabeculation and formation of the atria walls (By similarity). Loss of desmosome cell junctions leads to mis-localization of DSP and DSG2 resulting in disruption of cell-cell adhesion and disordered intermediate filaments (By similarity). Modulates profibrotic gene expression in cardiomyocytes via regulation of DSP expression and subsequent activation of downstream TGFB1 and MAPK14/p38 MAPK signaling (By similarity). Required for cardiac sodium current propagation and electrical synchrony in cardiac myocytes, via ANK3 stabilization and modulation of SCN5A/Nav1.5 localization to cell-cell junctions (By similarity). Required for mitochondrial function, nuclear envelope integrity and positive regulation of SIRT3 transcription via maintaining DES localization at its nuclear envelope and cell tip anchoring points, and thereby preserving regulation of the transcriptional program (PubMed:35959657). Maintenance of nuclear envelope integrity protects against DNA damage and transcriptional dysregulation of genes, especially those involved in the electron transport chain, thereby preserving mitochondrial function and protecting against superoxide radical anion generation (PubMed:35959657). Binds single-stranded DNA (ssDNA) (PubMed:20613778). May regulate the localization of GJA1 to gap junctions in intercalated disks of the heart (PubMed:18662195). Involved in the inhibition of viral infection by influenza A viruses (IAV) (PubMed:28169297). Acts as a host restriction factor for IAV viral propagation, potentially via disrupting the interaction of IAV polymerase complex proteins (PubMed:28169297)","subcellular_location":"Nucleus; Cell junction, desmosome; Cell junction; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q99959/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PKP2","classification":"Not Classified","n_dependent_lines":13,"n_total_lines":1208,"dependency_fraction":0.01076158940397351},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CAPZB","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PKP2","total_profiled":1310},"omim":[{"mim_id":"620734","title":"CARDIOMYOPATHY, FAMILIAL HYPERTROPHIC, 30, ATRIAL; CMH30","url":"https://www.omim.org/entry/620734"},{"mim_id":"619747","title":"CARDIOMYOPATHY, DILATED, 2F; 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Relevance to arrhythmogenic cardiomyopathy","date":"2025-10-23","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.22.682160","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.02.656790","title":"PKP2 orchestrates OXPHOS expression in cardiomyocytes via a PGC1α-dependent mechanism","date":"2025-06-04","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.02.656790","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.30.679431","title":"Single-cell sequencing of trophoblasts in preeclampsia and chemical hypoxia in BeWo b30 cells reveals EBI3, COL17A1, miR-27a-5p and miR-193b-5p as hypoxia-response markers","date":"2025-10-01","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.30.679431","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.01.17.633239","title":"Plakophilin-2 Coordinates Energy Metabolism and Contractility in Cardiomyocytes, Revealing Its Roles beyond Desmosomes","date":"2025-01-20","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.17.633239","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.12.12.628155","title":"Computational Modeling of Effects of  <i>PKP2</i>  Gene Therapy on Ventricular Conduction Properties in Arrhythmogenic Cardiomyopathy","date":"2024-12-17","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.12.628155","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.29.25324867","title":"Genomic and molecular evidence that the lncRNA<i>DSP-AS1</i>modulates Desmoplakin expression","date":"2025-03-31","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.29.25324867","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.10.14.618172","title":"Depleting trafficking regulator CASK promotes intercalated disc organization and ventricular function","date":"2024-10-17","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.14.618172","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.12.11.628020","title":"Interleukin-1β Drives Disease Progression in Arrhythmogenic Cardiomyopathy","date":"2024-12-17","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.11.628020","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.09.658637","title":"The Desmoglein 2 interactome in primary neonatal cardiomyocytes","date":"2025-06-10","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.09.658637","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":42094,"output_tokens":5477,"usd":0.104219,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":14070,"output_tokens":5259,"usd":0.100913,"stage2_stop_reason":"end_turn"},"total_usd":0.205132,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"C-TAK1 (Cdc25C-associated kinase 1) phosphorylates PKP2, generating a 14-3-3-binding site that influences PKP2 subcellular localization. This was established using mutational analysis of C-TAK1 binding motifs and in vivo phosphorylation assays, identifying PKP2 as a novel C-TAK1 substrate.\",\n      \"method\": \"Mutational approach disrupting C-TAK1 binding, in vivo phosphorylation assays, 14-3-3 binding site mapping\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with mutagenesis plus in vivo validation of 14-3-3 binding site and localization, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"12941695\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ARVC-associated truncation mutants of PKP2 (R79x and 179fs) fail to localize to sites of cell-cell apposition in neonatal rat ventricular myocytes. Early truncation at position 79 prevents physical interaction of PKP2 with both desmoplakin (DP) and connexin-43 (Cx43), and R79x expression reduced Cx43 abundance and correlated with loss of HSP90 expression.\",\n      \"method\": \"Adenoviral expression of mutant PKP2 constructs in neonatal rat ventricular myocytes, co-immunoprecipitation, immunofluorescence localization\",\n      \"journal\": \"Heart rhythm\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP and localization in primary cardiomyocytes with two PKP2 mutants, single lab with multiple readouts\",\n      \"pmids\": [\"19084810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Expression of truncated PKP2 (PKP2-Ser329) in transgenic mice causes dose-dependent reduction and remodeling of desmosomal proteins (Desmocollin-2, Plakoglobin, native PKP2, Desmin, β-Catenin) and electrical coupling proteins (Connexin 43, Nav1.5), establishing that truncated PKP2 disrupts the molecular composition of the intercalated disc.\",\n      \"method\": \"Transgenic mouse model with truncated PKP2, immunofluorescence, western blot, echocardiography, electrophysiology\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo transgenic model with dose-dependent readouts and multiple molecular endpoints, single lab\",\n      \"pmids\": [\"27412010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PKP2 is a direct transcriptional target of the Wnt/β-catenin pathway, induced via three TCF binding sites in the PKP2 gene promoter and one in an enhancer 20 kb upstream of the transcription start site. Furthermore, Plakophilin-2 antagonizes Wnt/β-catenin transcriptional activity in HEK-293T cells, suggesting it acts as an intracellular feedback inhibitor of the pathway.\",\n      \"method\": \"Transcriptomic analysis, reporter assays, ChIP or promoter binding site analysis in normal and colon cancer-associated fibroblasts, HEK-293T overexpression assay\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay with defined binding sites plus functional antagonism assay, single lab with two orthogonal methods\",\n      \"pmids\": [\"29044515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PRMT1 methylates PKP2 at an arginine residue; methylated PKP2 stabilizes β-catenin by recruiting USP7, which then induces LIG4 expression and promotes non-homologous end-joining (NHEJ) DNA repair, thereby driving radiation resistance in lung cancer cells.\",\n      \"method\": \"CRISPR/Cas9 library screen, mass spectrometry identification of arginine methylation, co-immunoprecipitation, functional assays of NHEJ repair, pharmacologic inhibition of PRMT1\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mass spectrometry confirmed PTM, Co-IP for complex, functional rescue experiments, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"33742119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PKP2 deficiency in cardiomyocytes causes loss of nuclear envelope integrity, which leads to DNA damage and excess oxidant production (superoxide and H2O2) under baseline and mechanical stress conditions. PKP2-deficient cells release H2O2 extracellularly, causing DNA damage in neighboring myocytes in a paracrine manner. Early transcriptional downregulation of electron transport chain proteins precedes left ventricular dysfunction.\",\n      \"method\": \"High-resolution mass spectrometry, RNA sequencing, transmission electron microscopy of ARVC patient biopsies; multiple imaging and biochemical techniques in cardiac-specific Pkp2 knockout mice and PKP2-deficient hiPSC-derived cardiomyocytes\",\n      \"journal\": \"Circulation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (proteomics, transcriptomics, TEM, biochemistry) replicated across patient biopsies, mouse KO, and hiPSC-CMs in the same study\",\n      \"pmids\": [\"35959657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In adult cardiac myocytes, PKP2 transcript abundance is transcriptionally linked to genes coding for inflammatory/immune response molecules. Loss of PKP2 in cardiomyocytes (PKP2cKO mice) upregulates a large set of transcripts associated with inflammatory/immune pathways, inversely correlated with PKP2 abundance in human cardiac transcriptomes.\",\n      \"method\": \"Cardiac-specific tamoxifen-activated PKP2-knockout mice crossed with RiboTag line; cardiomyocyte-specific ribosome-resident transcriptome profiling; GTEx human transcriptome correlation analysis\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cardiomyocyte-specific KO with translating ribosome affinity purification plus human transcriptome cross-validation, single lab\",\n      \"pmids\": [\"33536940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"AAV-mediated delivery of PKP2 in PKP2 mutant iPSC-derived cardiomyocytes restored junctional protein levels (which were reduced by the mutation), improved sodium conduction (rescuing arrhythmic substrate), and enhanced contractile function. In heterozygous Pkp2 knock-in mice, AAV9-PKP2 prevented cardiac dysfunction at 12 months, confirming restoration of desmosomal integrity and cardiac function in vivo.\",\n      \"method\": \"AAV transduction of PKP2c.2013delC/WT iPSC-derived cardiomyocytes, engineered human myocardium, heterozygous Pkp2c.1755delA knock-in mice; electrophysiology, contractility assays, immunostaining of junctional proteins\",\n      \"journal\": \"Nature cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic rescue in hiPSC-CMs and in vivo mouse model with multiple functional and molecular endpoints, replicated across systems\",\n      \"pmids\": [\"38665939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"AAV9-mediated restoration of PKP2 in cardiac-specific Pkp2 knockout mice rescues desmosome and gap junction structure, prevents right ventricular dilation, reduces ventricular arrhythmias, and reverses adverse fibrotic remodeling. RNA sequencing shows AAV9:PKP2 causes broad correction of PKP2-associated transcriptional networks beyond desmosomes.\",\n      \"method\": \"AAV9 gene delivery in cardiac-specific Pkp2 KO mice; echocardiography, electrocardiography, histology, RNA sequencing\",\n      \"journal\": \"Communications medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO rescue with multiple functional, structural, and transcriptomic endpoints in a single rigorous study\",\n      \"pmids\": [\"38499690\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In exercise-trained PKP2-deficient (PKP2cKO) cardiomyocytes, the pool of sarcolemmal β1-adrenergic receptors (β1-ARs) is decreased compared with exercise-trained controls (where it increases). Intracellular (dyad-associated) β1-ARs remain available in trained PKP2cKO myocytes, as shown by OCT3 knockdown that abolished norepinephrine (non-membrane-permeable) response but not isoproterenol (membrane-permeable) response. Additionally, sympathetic nerve terminal abundance and distribution are heterogeneous in trained PKP2cKO hearts.\",\n      \"method\": \"Expansion microscopy and structured illumination microscopy of β1-ARs; shRNA knockdown of OCT3; Ca2+ transient dynamics with isoproterenol vs norepinephrine; sympathetic terminal distribution imaging\",\n      \"journal\": \"Heart rhythm\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple imaging modalities with genetic knockdown confirmation, single lab\",\n      \"pmids\": [\"40383179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PKP2 is a direct target of miR-7-5p; overexpression of miR-7-5p reduces PKP2 protein levels and enhances radiosensitivity in A549 NSCLC cells by increasing DNA damage (γ-H2AX foci) and inhibiting NHEJ repair. Overexpression of PKP2 rescues the radiosensitizing effects of miR-7-5p, confirming the miR-7-5p/PKP2 regulatory axis.\",\n      \"method\": \"Clonogenic assays, CCK-8 assays, immunofluorescence (γ-H2AX), western blotting, reporter gene assays (luciferase 3'UTR validation)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct reporter assay plus functional rescue with PKP2 overexpression, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"40374728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PKP2 deficiency in cardiomyocytes disrupts oxidative phosphorylation (OXPHOS) gene expression through reduced PPARGC1A (PGC1α) expression, leading to decreased mitochondrial spare capacity in PKP2 mutant hiPSC-CMs and explanted human hearts. Induction of PPARGC1A expression partially restored OXPHOS component expression and improved contractility in PKP2 mutant cells.\",\n      \"method\": \"RNA sequencing of hiPSC-CMs and human explanted hearts; mitochondrial spare capacity (Seahorse) assay; PPARGC1A overexpression rescue experiments\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transcriptomic plus functional metabolic assay with rescue experiment, single lab, preprint not peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PKP2 deficiency in cardiomyocytes causes impaired lipid homeostasis, glycolysis, and glucose oxidation, with specific metabolic defects linked to poor contractility of cardiomyocytes. AAV9:PKP2 restoration improved contractility, electrophysiological properties, and Ca2+ transients, while pharmacologic metabolic enhancers improved contractility but not electrophysiology, indicating differential sensitivity of PKP2-dependent functions to metabolic perturbation.\",\n      \"method\": \"Steady-state metabolomics in PKP2-deficient mouse hearts and hiPSC-CMs; AAV9:PKP2 gene rescue; pharmacologic metabolic enhancement; contractility and Ca2+ transient measurement\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — metabolomics plus functional rescue in two model systems, single lab, preprint not peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Loss of PKP2 expression specifically in cardiomyocytes (PKP2cKO) is sufficient to induce senescence-associated heterochromatin foci (SAHFs), p21 staining, and senescence-associated secretory phenotype (SASP) cytokines in neighboring non-myocyte cardiac resident cells, as well as premature epigenetic aging of the heart.\",\n      \"method\": \"Conventional and multiplex imaging, cytokine arrays, epigenetic clocks, spatial transcriptomics, expansion and structured illumination microscopy in cardiac-specific PKP2 KO mice\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cardiomyocyte-specific KO with multiple orthogonal senescence readouts, single lab, preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CASK (calcium/calmodulin-dependent serine protein kinase) negatively regulates PKP2 localization at intercalated discs; CASK knockdown increases PKP2 accumulation at cell contacts and promotes desmosome-like structure formation. In PKP2+/- hiPSC-CMs, CASK expression is increased, and CASK depletion rescues PKP2 accumulation at contacts and improves stress resistance.\",\n      \"method\": \"AAV-mediated CASK knockdown in neonatal rat hearts, high-resolution imaging, proteomics, electron microscopy, mechano-SICM in NRVM and PKP2+/- hiPSC-CMs\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple imaging modalities and functional assays across multiple model systems, single lab, preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PKP2 is a dynamic protein at the intercalated disc of cardiomyocytes whose membrane recruitment is tension-dependent. Proximity labeling mass spectrometry identified PKP2 among the most abundant proteins shared between the DSG2 and N-cadherin interactomes in cardiomyocytes, establishing PKP2 as a component of the intercalated disc macromolecular complex.\",\n      \"method\": \"Proximity labeling (BioID/TurboID) combined with quantitative mass spectrometry in cultured neonatal cardiomyocytes; tension-dependence assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proximity labeling MS interactome with functional tension-dependence validation, single lab, preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PKP2 deficiency in epicardium-derived cells (EPDCs) facilitates emergence of a pro-inflammatory, senescence-associated secretory phenotype (SASP) fibroblast population; however, cardiomyocyte involvement is required for ACM pathogenesis, as EPDC-specific Pkp2 deletion alone does not elicit a pathological phenotype. B-cell depletion delays early inflammatory and fibrosis response in Pkp2-deficient hearts.\",\n      \"method\": \"Tissue-specific tamoxifen-inducible Cre transgenic mice (cardiomyocyte-specific, EPDC-specific, and combined KO); single-cell RNA sequencing; flow cytometry; immunohistochemistry; antibody-mediated B-cell depletion\",\n      \"journal\": \"Circulation. Heart failure\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis across three tissue-specific KO lines with scRNAseq and functional depletion experiments, single lab\",\n      \"pmids\": [\"42246055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PKP2 deficiency in iPSC-derived epicardial cells (hPSC-EPCs) causes enhanced epithelial-to-mesenchymal transition, increased lipid accumulation, and a fibrotic phenotype. RNA-seq of ACM hPSC-EPCs reveals dysregulation of Wnt, interferon, and Rho GTPase signaling, upregulation of IGF2 and the adipogenic transcription factor CEBPA. Recombinant IGF2 treatment of control and PKP2KO hPSC-EPCs enhanced CEBPA expression, implicating IGF signaling in fatty-fibro remodeling.\",\n      \"method\": \"iPSC differentiation into epicardial cells, CRISPR/Cas9 KO and patient-derived mutant lines, RNA-seq, lipid accumulation assays, recombinant IGF2 treatment\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isogenic CRISPR KO and patient lines with transcriptomic and functional assays plus pathway rescue, single lab\",\n      \"pmids\": [\"41145823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AAV9-PKP2 gene therapy in Pkp2-knockout rats attenuated cardiac fibrosis by inducing phenotypic conversion of activated profibrotic cardiac fibroblasts into quiescent antifibrotic states, with Ptprc (protein tyrosine phosphatase receptor type C) identified as a key regulator of this reprogramming via single-cell RNA sequencing.\",\n      \"method\": \"Pkp2-knockout rat model, AAV9-PKP2 delivery, single-cell RNA sequencing, fibroblast phenotyping, bioinformatics\",\n      \"journal\": \"MedComm\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO rescue with scRNAseq mechanistic endpoint, single lab\",\n      \"pmids\": [\"40979216\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"A PKP2 frameshift mutation (c.1125_1132del, paternal) causes nuclear aggregation of the truncated PKP2 protein (aberrant localization confirmed by immunofluorescence), while a splice-site variant (c.224-3 C>G, maternal) causes exon 2 skipping and protein truncation. Both defects synergistically disrupt desmosomal integrity in cardiomyocytes via biallelic inactivation.\",\n      \"method\": \"MiniGene splicing assays, RT-PCR splice validation, immunofluorescence microscopy of subcellular localization, cycloheximide chase for protein stability\",\n      \"journal\": \"Functional & integrative genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional splicing assay plus protein localization imaging with stability assay, single lab with multiple methods\",\n      \"pmids\": [\"41535644\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PKP2 encodes plakophilin-2, a desmosomal scaffold protein at the cardiac intercalated disc whose membrane recruitment is tension-dependent; it is phosphorylated by C-TAK1 to generate a 14-3-3-binding site controlling its localization, physically interacts with desmoplakin and connexin-43, and maintains the molecular integrity of gap junctions and sodium channels (Nav1.5) — loss of PKP2 disrupts desmosomal and electrical remodeling, causes nuclear envelope loss with consequent DNA damage and excess oxidant production, downregulates oxidative phosphorylation via PGC1α, drives transcriptional upregulation of inflammatory/immune pathways in cardiomyocytes, and induces paracrine senescence in neighboring non-myocytes, collectively establishing arrhythmogenic cardiomyopathy substrate.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PKP2 encodes plakophilin-2, a dynamic scaffold protein of the cardiomyocyte intercalated disc whose tension-dependent membrane recruitment integrates it into the desmosomal macromolecular complex shared between the DSG2 and N-cadherin interactomes [#15]. PKP2 physically bridges desmosomal and electrical machinery, interacting with desmoplakin and connexin-43; ARVC-associated truncation mutants fail to reach cell-cell junctions and lose these interactions, reducing Cx43 abundance [#1], while truncated PKP2 in vivo causes dose-dependent remodeling of desmosomal components (desmocollin-2, plakoglobin, desmin, \\u03b2-catenin) and the conduction proteins Cx43 and Nav1.5 [#2]. Its localization is controlled by post-translational and regulatory inputs: C-TAK1 phosphorylates PKP2 to create a 14-3-3-binding site governing subcellular distribution [#0], and CASK negatively regulates its accumulation at intercalated discs [#14]. Beyond junctional architecture, PKP2 loss in cardiomyocytes triggers a broad pathological cascade \\u2014 loss of nuclear envelope integrity with DNA damage and paracrine H2O2-driven oxidant production [#5], downregulation of oxidative phosphorylation via reduced PPARGC1A/PGC1\\u03b1 [#11], transcriptional upregulation of inflammatory/immune pathways [#6], and induction of senescence in neighboring non-myocytes [#13] \\u2014 collectively establishing the arrhythmogenic cardiomyopathy substrate. PKP2 mutations cause arrhythmogenic cardiomyopathy, and AAV-mediated PKP2 restoration rescues junctional protein levels, sodium conduction, contractility, and adverse fibrotic and transcriptional remodeling in mutant iPSC-cardiomyocytes and in vivo [#7, #8]. In a distinct context, PKP2 acts in tumor cells as a Wnt/\\u03b2-catenin target and feedback antagonist [#3] and, when methylated by PRMT1, stabilizes \\u03b2-catenin to promote NHEJ-mediated DNA repair and radiation resistance [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established the first post-translational control point for PKP2 localization, showing its membrane targeting is a regulated rather than constitutive property.\",\n      \"evidence\": \"C-TAK1 binding-motif mutagenesis and in vivo phosphorylation assays mapping a 14-3-3-binding site\",\n      \"pmids\": [\"12941695\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address the cardiac intercalated-disc context\", \"Functional consequence of altered localization on junction assembly not tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected ARVC truncation mutations to a molecular mechanism by showing they prevent junctional targeting and loss of binding to desmoplakin and connexin-43.\",\n      \"evidence\": \"Adenoviral expression of PKP2 truncation mutants in neonatal rat ventricular myocytes with Co-IP and immunofluorescence\",\n      \"pmids\": [\"19084810\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Two mutants only; broader mutational spectrum untested\", \"Co-IP without reciprocal or structural validation of the interaction interface\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated in vivo that truncated PKP2 disrupts the entire intercalated-disc protein composition, linking a single defective subunit to coordinated desmosomal and electrical remodeling.\",\n      \"evidence\": \"Transgenic mouse expressing truncated PKP2 with immunofluorescence, western blot, echocardiography and electrophysiology\",\n      \"pmids\": [\"27412010\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Dominant-negative vs haploinsufficiency mechanism not resolved\", \"Order of molecular events leading to disc disassembly unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed PKP2 within Wnt/\\u03b2-catenin signaling as both a transcriptional target and a feedback antagonist, extending its role beyond structural scaffolding.\",\n      \"evidence\": \"Reporter assays with mapped TCF binding sites and functional antagonism in HEK-293T and fibroblast systems\",\n      \"pmids\": [\"29044515\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relevance to cardiomyocyte biology not addressed\", \"Mechanism of \\u03b2-catenin antagonism not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed a cancer-cell function in which PRMT1-methylated PKP2 stabilizes \\u03b2-catenin and promotes NHEJ DNA repair, driving radiation resistance.\",\n      \"evidence\": \"CRISPR screen, mass-spectrometry detection of arginine methylation, Co-IP and NHEJ functional assays in lung cancer cells\",\n      \"pmids\": [\"33742119\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Methylated arginine residue's structural role unmapped\", \"Whether this axis operates in cardiomyocytes unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Linked PKP2 abundance to suppression of inflammatory/immune transcriptional programs in cardiomyocytes, defining a non-structural consequence of PKP2 loss.\",\n      \"evidence\": \"Cardiomyocyte-specific tamoxifen-inducible KO with RiboTag translatome profiling and GTEx cross-validation\",\n      \"pmids\": [\"33536940\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking PKP2 loss to inflammatory transcription not defined\", \"Causal contribution to disease vs bystander effect unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified nuclear envelope disruption, DNA damage, and paracrine oxidant production as early consequences of PKP2 loss, expanding the disease model from junctional to nuclear/metabolic dysfunction.\",\n      \"evidence\": \"Proteomics, RNA-seq, TEM across ARVC biopsies, cardiac-specific Pkp2 KO mice and PKP2-deficient hiPSC-CMs\",\n      \"pmids\": [\"35959657\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between a disc protein and nuclear envelope integrity unresolved\", \"How H2O2 propagates damage to neighboring cells not fully defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Provided proof-of-concept that PKP2 gene supplementation reverses arrhythmic and contractile substrate, establishing PKP2 deficiency as causal and correctable.\",\n      \"evidence\": \"AAV transduction of mutant iPSC-CMs, engineered human myocardium, and heterozygous Pkp2 knock-in mice with electrophysiology and contractility readouts\",\n      \"pmids\": [\"38665939\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Durability and dosing window in human disease unaddressed\", \"Whether nuclear/metabolic defects are also rescued not tested here\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed AAV9-PKP2 corrects structure, arrhythmia, fibrosis, and broad transcriptional networks in vivo, demonstrating systemic reversibility beyond desmosomes.\",\n      \"evidence\": \"AAV9 delivery in cardiac-specific Pkp2 KO mice with echocardiography, ECG, histology and RNA-seq\",\n      \"pmids\": [\"38499690\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of transcriptional network normalization not dissected\", \"Reversibility of established late-stage fibrosis unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined PKP2 as a tension-dependent dynamic disc component within the DSG2/N-cadherin interactome, anchoring its scaffolding role in mechanobiology.\",\n      \"evidence\": \"Proximity-labeling mass spectrometry and tension-dependence assays in neonatal cardiomyocytes (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Molecular sensor of tension upstream of PKP2 recruitment unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified CASK as a negative regulator of PKP2 junctional accumulation, adding a counter-regulatory input whose dysregulation contributes to mutant phenotypes.\",\n      \"evidence\": \"AAV CASK knockdown in neonatal rat hearts, imaging, proteomics, EM and mechano-SICM in NRVM and PKP2+/- hiPSC-CMs (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Direct vs indirect mechanism of CASK action on PKP2 not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended PKP2 disease biology to metabolic failure, showing PGC1\\u03b1-dependent OXPHOS suppression and impaired substrate handling that limit contractility.\",\n      \"evidence\": \"RNA-seq, Seahorse respirometry, metabolomics and PPARGC1A/AAV9 rescue in hiPSC-CMs, mouse and human hearts (preprints)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprints, not peer-reviewed\", \"How PKP2 loss represses PPARGC1A mechanistically is unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established that PKP2 loss in cardiomyocytes drives paracrine senescence and premature epigenetic aging of cardiac non-myocytes.\",\n      \"evidence\": \"Multiplex imaging, cytokine arrays, epigenetic clocks and spatial transcriptomics in cardiac-specific PKP2 KO mice (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Signal mediating cardiomyocyte-to-non-myocyte senescence not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Used tissue-specific epistasis to show cardiomyocyte PKP2 loss is required for ACM pathogenesis while EPDC loss alone is insufficient, and implicated B cells in early inflammation.\",\n      \"evidence\": \"Cardiomyocyte-, EPDC-, and combined-specific inducible KO mice with scRNA-seq, flow cytometry and B-cell depletion\",\n      \"pmids\": [\"42246055\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cell-type crosstalk mediating EPDC SASP not defined\", \"B-cell antigen and mechanism of recruitment unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked epicardial PKP2 loss to fatty-fibrotic remodeling through EMT, IGF2/CEBPA-driven adipogenesis and Wnt/interferon/Rho dysregulation.\",\n      \"evidence\": \"iPSC-derived epicardial cells (CRISPR KO and patient lines), RNA-seq, lipid assays and recombinant IGF2 treatment\",\n      \"pmids\": [\"41145823\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of IGF2/CEBPA axis untested\", \"Connection to cardiomyocyte-required pathogenesis unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed AAV9-PKP2 reverses fibrosis by reprogramming activated fibroblasts to quiescent states, identifying Ptprc as a regulator of this conversion.\",\n      \"evidence\": \"Pkp2-KO rat model with AAV9-PKP2 delivery and single-cell RNA sequencing of fibroblast states\",\n      \"pmids\": [\"40979216\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct role of Ptprc not functionally validated\", \"Whether fibroblast reprogramming is PKP2-cell-autonomous unclear\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Defined biallelic loss-of-function mechanisms in patients, showing distinct mutations (nuclear aggregation vs exon skipping) synergize to inactivate PKP2 and disrupt desmosomal integrity.\",\n      \"evidence\": \"MiniGene splicing assays, RT-PCR, immunofluorescence localization and cycloheximide chase\",\n      \"pmids\": [\"41535644\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional cardiac phenotype not directly assessed\", \"Generalizability beyond this kindred unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular link connecting a junctional scaffold protein to nuclear envelope integrity, PGC1\\u03b1-dependent metabolism, and paracrine senescence remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No mechanism connecting PKP2 loss to PPARGC1A repression\", \"Signal driving non-myocyte senescence unidentified\", \"Tension-sensing machinery upstream of PKP2 recruitment unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [15, 2, 1]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 15]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 15, 2]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4, 19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [1, 2, 15]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 17]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [4, 10]}\n    ],\n    \"complexes\": [\n      \"intercalated disc\",\n      \"desmosome\"\n    ],\n    \"partners\": [\n      \"DSP\",\n      \"GJA1\",\n      \"DSG2\",\n      \"CDH2\",\n      \"CTNNB1\",\n      \"CASK\",\n      \"PRMT1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}