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Background: Empirical decisions to select therapies for psoriasis (PSO) and atopic dermatitis (AD) can lead to delays in disease control and increased health care costs. However, routine molecular testing for AD and PSO are lacking., Objective: To examine (1) how clinicians choose systemic therapies for patients with PSO and AD without molecular testing and (2) to determine how often the current approach leads to patients switching medications., Methods: A 20-question survey designed to assess clinician strategies for systemic treatment of AD and PSO was made available to attendees of a national dermatology conference in 2022., Results: Clinicians participating in the survey (265/414, 64% response rate) ranked "reported efficacy" as the most important factor governing treatment choice ( P  < .001). However, 62% (165/265) of clinicians estimated that 2 or more systemic medications were typically required to achieve efficacy. Over 90% (239/265) of respondents would or would likely find a molecular test to guide therapeutic selection useful., Limitations: To facilitate ease of recall, questions focused on systemic therapies as a whole and not individual therapies., Conclusion: Clinicians want a molecular test to help determine the most efficacious drug for individual patients., Competing Interests: Dr Brownstone received a stipend paid for by Castle Biosciences, Inc. Dr Farberg is a consultant for Castle Biosciences, Inc and on the advisory board for Amgen, Boehringer Ingelheim, Eli Lilly, Galderma, Incyte, Janssen, Novartis, Ortho Dermatologics, Pfizer, and Sun Pharma. Drs Quick, Siegel, Hurton, and Goldberg are employees and option and stockholders for Castle Biosciences, Inc. Dr Lio reports research grants/funding from AbbVie, AOBiome, Eczema Foundation, National Eczema Association; is on the speaker's bureau for AbbVie, Eli Lilly, Galderma, Hyphens Pharma, Incyte, La Roche-Posay/L’Oreal, MyOR Diagnostics, ParentMD, Pfizer, Pierre-Fabre Dermatologie, and Regeneron/Sanofi Genzyme; reports consulting/advisory boards for AbbVie, Almirall, Amyris, Arbonne, ASLAN, Bodewell, Boston Skin Science, Bristol-Myers Squibb, Burt’s Bees, Castle Biosciences, Codex Labs, Concerto Biosci, Dermavant, Dermira, DermVeda, Eli Lilly, Galderma, IntraDerm, Janssen, Johnson & Johnson, Kaleido Biosci, Kimberly Clark, LEO Pharma, Lipidor, L’Oreal, Menlo Therapeutics, Merck, Micreos, MyOR Diagnostics, Regeneron/Sanofi Genzyme, Sibel Health, Skinfix, Sonica, Theraplex, UCB, Unilever, Verrica, and Yobee Care; reports stock options with LearnSkin/Learn Health, Medable, Micreos, Modernizing Medicine, and Yobee Care. In addition, Dr Lio has a patent pending for a Theraplex product with royalties paid and is a Board member and Scientific Advisory Committee Member of the National Eczema Association. Author Litchman has no conflicts of interest to declare., (© 2024 by the American Academy of Dermatology, Inc. Published by Elsevier Inc.)

Myocardial lipid metabolism is critical to normal heart function, whereas altered lipid regulation has been linked to cardiac diseases including cardiomyopathies. Genetic variants in the JPH2 gene can cause hypertrophic cardiomyopathy (HCM) and, in some cases, dilated cardiomyopathy (DCM). In this study, we tested the hypothesis that JPH2 variants identified in patients with HCM and DCM, respectively, cause distinct alterations in myocardial lipid profiles. Echocardiography revealed clinically significant cardiac dysfunction in both knock-in mouse models of cardiomyopathy. Unbiased myocardial lipidomic analysis demonstrated significantly reduced levels of total unsaturated fatty acids, ceramides, and various phospholipids in both mice with HCM and DCM, suggesting a common metabolic alteration in both models. On the contrary, significantly increased di- and triglycerides, and decreased co-enzyme were only found in mice with HCM. Moreover, mice with DCM uniquely exhibited elevated levels of cholesterol ester. Further in-depth analysis revealed significantly altered metabolites from all the lipid classes with either similar or opposing trends in JPH2 mutant mice with HCM or DCM. Together, these studies revealed, for the first time, unique alterations in the cardiac lipid composition-including distinct increases in neutral lipids and decreases in polar membrane lipids-in mice with HCM and DCM were caused by distinct JPH2 variants. These studies may aid the development of novel biomarkers or therapeutics for these inherited disorders., (© 2024 Lahiri et al.)

Deep skin wounds represent a serious condition and frequently require split-thickness skin grafts (STSG) to heal. The application of autologous human-skin-cell-suspension (hSCS) requires less donor skin than STSG without compromising the healing capacity. Impaired function and replicative ability of senescent cutaneous cells in the aging skin affects healing with autologous hSCS. Major determinants of senescence are telomere erosion and DNA damage. Human telomerase reverse transcriptase (hTERT) adds telomeric repeats to the DNA and can protect against DNA damage. Herein, hTERT mRNA lipid nanoparticles (LNP) are proposed and evaluated for enhancing cellular engraftment and proliferation of hSCS. Transfection with optimized hTERT mRNA LNP system enables delivery and expression of mRNA in vitro in keratinocytes, fibroblasts, and in hSCS prepared from donors' skin. Telomerase activity in hSCS is significantly increased. hTERT mRNA LNP enhance the generation of a partial-thickness human skin equivalent in the mouse model, increasing hSCS engraftment (Lamin) and proliferation (Ki67), while reducing cellular senescence (p21) and DNA damage (53BP1)., (© 2023 Wiley-VCH GmbH.)

Objective: The 31-gene expression profile (31-GEP) can predict the risk of recurrence and metastasis in cutaneous melanoma (CM). We assessed the viewpoints and use of 31-GEP testing by physician assistants (PAs) and nurse practitioners (NPs) for patients with CM., Methods: NPs and PAs ( n = 369) completed an 18-question online survey about their viewpoints and use of the 31-GEP risk-stratification test., Results: Most practitioners ( n = 334, 90.5%) felt prognostic testing improved patient care and would recommend the 31-GEP to a colleague ( n = 333, 90.2%) or a friend or family member ( n = 289, 78.3%) who was diagnosed with CM. The 31-GEP test was used by 176 respondents in the preceding 12 months (53%). Among users of the 31-GEP test, 78% stated that the results would impact follow-up schedule and referral, 66% overall treatment decisions, 62% sentinel lymph node biopsy recommendations, and 50% surveillance imaging. In thin tumors (≤ 1 mm), 82% of 31-GEP users and 44% of nonusers stated that the 31-GEP results would impact their treatment plan decisions., Conclusion: The 31-GEP test significantly impacts treatment plans in CM, particularly for thin and stage I melanomas. Importantly, even nonusers stated that 31-GEP test results would impact treatment plans as well as recommendations to a friend or family member., Competing Interests: This study was funded by Castle Biosciences, Inc. Ms. Block has no conflicts of interest and nothing to declare. Ms. Patterson, Dr. Siegel, Dr. Martin, and Dr. Quick are employees, and stock and options holders at Castle Biosciences, Inc. Ms. Hunt is on the speakers bureau at Castle Biosciences, Inc., (© 2023 BroadcastMed LLC.)

Background: Many patients with low-stage cutaneous melanoma will experience tumor recurrence, metastasis, or death, and many higher staged patients will not., Objective: To develop an algorithm by integrating the 31-gene expression profile test with clinicopathologic data for an optimized, personalized risk of recurrence (integrated 31 risk of recurrence [i31-ROR]) or death and use i31-ROR in conjunction with a previously validated algorithm for precise sentinel lymph node positivity risk estimates (i31-SLNB) for optimized treatment plan decisions., Methods: Cox regression models for ROR were developed (n = 1581) and independently validated (n = 523) on a cohort with stage I-III melanoma. Using National Comprehensive Cancer Network cut points, i31-ROR performance was evaluated using the midpoint survival rates between patients with stage IIA and stage IIB disease as a risk threshold., Results: Patients with a low-risk i31-ROR result had significantly higher 5-year recurrence-free survival (91% vs 45%, P < .001), distant metastasis-free survival (95% vs 53%, P < .001), and melanoma-specific survival (98% vs 73%, P < .001) than patients with a high-risk i31-ROR result. A combined i31-SLNB/ROR analysis identified 44% of patients who could forego sentinel lymph node biopsy while maintaining high survival rates (>98%) or were restratified as being at a higher or lower risk of recurrence or death., Limitations: Multicenter, retrospective study., Conclusion: Integrating clinicopathologic features with the 31-GEP optimizes patient risk stratification compared to clinicopathologic features alone., Competing Interests: Conflicts of interest Dillon, Covington, Goldberg, Bailey, Quick, Martin, Kurley, and Cook are employees and stock and options holders at Castle Biosciences, Inc. Jarell and Hsueh are on the speaker’s bureau for Castle Biosciences, Inc. Podlipnik and Puig have no conflicts of interest to disclose., (Copyright © 2022 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Ryanodine receptors (RyRs) exhibit dynamic arrangements in cardiomyocytes, and we previously showed that 'dispersion' of RyR clusters disrupts Ca 2+ homeostasis during heart failure (HF) (Kolstad et al., eLife, 2018). Here, we investigated whether prolonged β-adrenergic stimulation, a hallmark of HF, promotes RyR cluster dispersion and examined the underlying mechanisms. We observed that treatment of healthy rat cardiomyocytes with isoproterenol for 1 hr triggered progressive fragmentation of RyR clusters. Pharmacological inhibition of Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) reversed these effects, while cluster dispersion was reproduced by specific activation of CaMKII, and in mice with constitutively active Ser2814-RyR. A similar role of protein kinase A (PKA) in promoting RyR cluster fragmentation was established by employing PKA activation or inhibition. Progressive cluster dispersion was linked to declining Ca 2+ spark fidelity and magnitude, and slowed release kinetics from Ca 2+ propagation between more numerous RyR clusters. In healthy cells, this served to dampen the stimulatory actions of β-adrenergic stimulation over the longer term and protect against pro-arrhythmic Ca 2+ waves. However, during HF, RyR dispersion was linked to impaired Ca 2+ release. Thus, RyR localization and function are intimately linked via channel phosphorylation by both CaMKII and PKA, which, while finely tuned in healthy cardiomyocytes, underlies impaired cardiac function during pathology., Competing Interests: XS, Jv, AB, TK, EN, YH, ML, YA, AQ, EE, IS, XW, AE, CS, WL No competing interests declared, (© 2022, Shen et al.)

Objective: National Comprehensive Cancer Network (NCCN) guidelines for cutaneous melanoma (CM) recommend physicians consider increased surveillance for patients who typically have lower melanoma survival rates (stages IIB-IV as determined by the American Joint Committee on Cancer (AJCC), 8th edition). However, up to 15% of patients identified as having a low recurrence risk (stages I-IIA) experience disease recurrence, and some patients identified as having a high recurrence risk will not experience any recurrence. The 31-gene expression profile test (31-GEP) stratifies patient recurrence risk into low (Class 1) and high (Class 2) and has demonstrated risk-appropriate impact on disease management and clinical decisions., Methods: Five-year plans for lab work, frequency of clinical visits, and imaging pre- and post-31-GEP test results were assessed for a cohort of 509 stage I-III patients following an interim subset analysis of 247 patients., Results: After receiving 31-GEP results, 50.6% of patients had a change in management plans in at least one of the following categories-clinical visits, lab work, or surveillance imaging. The changes aligned with the risk predicted by the 31-GEP for 76.1% of patients with a Class 1 result and 78.7% of patients with a Class 2 result. A Class 1 31-GEP result was associated with changes toward low-intensity management recommendations, while a Class 2 result was associated with changes toward high-intensity management recommendations., Conclusion: The 31-GEP can stratify patient recurrence risk in patients with CM, and clinicians understand and apply the prognostic ability of the 31-GEP test to alter patient management in risk-appropriate directions.

Background: There is a need to improve prognostic accuracy for patients with cutaneous melanoma. A 31-gene expression profile (31-GEP) test uses the molecular biology of primary tumors to identify individual patient metastatic risk., Objective: Develop a nomogram incorporating 31-GEP with relevant clinical factors to improve prognostic accuracy., Methods: In an IRB-approved study, 1124 patients from 9 Mohs micrographic surgery centers were prospectively enrolled, treated with Mohs micrographic surgery, and underwent 31-GEP testing. Data from 684 of those patients with at least 1-year follow-up or a metastatic event were included in nomogram development to predict metastatic risk., Results: Logistic regression modeling of 31-GEP results and T stage provided the simplest nomogram with the lowest Bayesian information criteria score. Validation in an archival cohort (n = 901) demonstrated a significant linear correlation between observed and nomogram-predicted risk of metastasis. The resulting nomogram more accurately predicts the risk for cutaneous melanoma metastasis than T stage or 31-GEP alone., Limitations: The patient population is representative of Mohs micrographic surgery centers. Sentinel lymph node biopsy was not performed for most patients and could not be used in the nomogram., Conclusions: Integration of 31-GEP and T stage can gain clinically useful prognostic information from data obtained noninvasively., Competing Interests: Conflicts of interest Drs Covington, Caruso, Quick, and Zolochevska are employees and stockholders at Castle Biosciences. Drs Thorpe, Bricca, Campoli, DeBloom, Fazio, Greenhaw, Kirkland, Machan, Brodland, and Zitelli have no conflicts of interest to disclose., (Copyright © 2021 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Cutaneous melanoma (CM) survival is assessed using averaged data from the American Joint Committee on Cancer 8th edition (AJCC8). However, subsets of AJCC8 stages I-III have better or worse survival than the predicted average value. The objective of this study was to determine if the 31-gene expression profile (31-GEP) test for CM can further risk-stratify melanoma-specific mortality within each AJCC8 stage. This retrospective multicenter study of 901 archival CM samples obtained from patients with stages I-III CM assessed 31-GEP test predictions of 5-year melanoma-specific survival (MSS) using Kaplan-Meier and Cox proportional hazards. In stage I-III CM population, patients with a Class 2B result had a lower 5-year MSS (77.8%) than patients with a Class 1A result (98.7%) and log-rank testing demonstrated significant stratification of MSS [χ2 (2df, n = 901) = 99.7, P < 0.001). Within each stage, 31-GEP data provided additional risk stratification, including in stage I [χ2 (2df, n = 415) = 11.3, P = 0.004]. Cox regression multivariable analysis showed that the 31-GEP test was a significant predictor of melanoma-specific mortality (MSM) in patients with stage I-III CM [hazard ratio: 6.44 (95% confidence interval: 2.61-15.85), P < 0.001]. This retrospective study focuses on Class 1A versus Class 2B results. Intermediate results (Class 1B/2A) comprised 21.6% of cases with survival rates between Class 1A and 2B, and similar to 5-year MSS AJCC stage values. Data from the 31-GEP test significantly differentiates MSM into lower (Class 1A) and higher risk (Class 2B) groups within each AJCC8 stage. Incorporating 31-GEP results into AJCC8 survival calculations has the potential to more precisely assess survival and enhance management guidance., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Fifteen to forty percent of patients with localized cutaneous melanoma (CM) (stages I-II) will experience disease relapse. The 31-gene expression profile (31-GEP) uses gene expression data from the primary tumor in conjunction with clinicopathologic features to refine patient prognosis. The study's objective was to evaluate 31-GEP risk stratification for disease-free survival (DFS) in a previously published cohort with longer follow-up., Methods: Patients with stage IB-II CM ( n = 86) were prospectively tested with the 31-GEP. Follow-up time increased from 2.2 to 3.9 years. Patient outcomes were compared using Kaplan-Meier and Cox regression analysis., Results: A Class 2B result was a significant predictor of 3-year DFS (hazard ratio (HR) 8.4, p = 0.008) in univariate analysis. The 31-GEP significantly stratified patients by risk of relapse ( p = 0.005). A Class 2B result was associated with a lower 3-year DFS (75.0%) than a Class 1A result (100%). The 31-GEP had a high sensitivity (77.8%) and negative predictive value (95.0%)., Conclusions: The 31-GEP is a significant predictor of disease relapse in patients with stage IB-II melanoma and accurately stratified patients by risk of relapse.

Aim: Sentinel node biopsy is a prognostic indicator of melanoma recurrence. We hypothesized that adding the primary melanoma molecular signature from the 31-gene expression profile (31-GEP) test could refine the risk of recurrence prognosis for patients with stage I-III melanoma. Materials & methods: Four hundred thirty-eight patients with stage I-III melanoma consecutively tested with the 31-GEP were retrospectively analyzed. The 31-GEP stratified patients as low-risk (Class 1A), intermediate-risk (Class 1B/2A) or high risk (Class 2B) of recurrence or metastasis. Results: The 31-GEP significantly stratified patient risk for recurrence-free survival (p < 0.001), distant metastasis-free survival (p < 0.001) and melanoma-specific survival (p < 0.001) and was a significant, independent predictor of metastatic recurrence (hazard ratio: 5.38; p = 0.014). Conclusion: The 31-GEP improves prognostic accuracy in stage I-III melanoma.

National guidelines recommend sentinel lymph node biopsy (SLNB) be offered to patients with > 10% likelihood of sentinel lymph node (SLN) positivity. On the other hand, guidelines do not recommend SLNB for patients with T1a tumors without high-risk features who have < 5% likelihood of a positive SLN. However, the decision to perform SLNB is less certain for patients with higher-risk T1 melanomas in which a positive node is expected 5%-10% of the time. We hypothesized that integrating clinicopathologic features with the 31-gene expression profile (31-GEP) score using advanced artificial intelligence techniques would provide more precise SLN risk prediction., Methods: An integrated 31-GEP (i31-GEP) neural network algorithm incorporating clinicopathologic features with the continuous 31-GEP score was developed using a previously reported patient cohort (n = 1,398) and validated using an independent cohort (n = 1,674)., Results: Compared with other covariates in the i31-GEP, the continuous 31-GEP score had the largest likelihood ratio (G 2 = 91.3, P < .001) for predicting SLN positivity. The i31-GEP demonstrated high concordance between predicted and observed SLN positivity rates (linear regression slope = 0.999). The i31-GEP increased the percentage of patients with T1-T4 tumors predicted to have < 5% SLN-positive likelihood from 8.5% to 27.7% with a negative predictive value of 98%. Importantly, for patients with T1 tumors originally classified with a likelihood of SLN positivity of 5%-10%, the i31-GEP reclassified 63% of cases as having < 5% or > 10% likelihood of positive SLN, for a more precise, personalized, and clinically actionable SLN-positive likelihood estimate., Conclusion: These data suggest the i31-GEP could reduce the number of SLNBs performed by identifying patients with likelihood under the 5% threshold for performance of SLNB and improve the yield of positive SLNBs by identifying patients more likely to have a positive SLNB., Competing Interests: John T. Vetto Employment: Gilead Sciences (I) Stock and Other Ownership Interests: Gilead Sciences (I), Roche/Genentech (I) Speakers' Bureau: Castle Biosciences Travel, Accommodations, Expenses: Castle Biosciences No other potential conflicts of interest were reported. John T. Vetto Employment: Gilead Sciences (I) Stock and Other Ownership Interests: Gilead Sciences (I), Roche/Genentech (I) Speakers' Bureau: Castle Biosciences Travel, Accommodations, Expenses: Castle Biosciences No other potential conflicts of interest were reported., (© 2021 by American Society of Clinical Oncology.)

Background: While patients with localized cutaneous melanoma (CM) generally have good five-year melanoma-specific survival rates, identifying patients with localized disease at a high risk of recurrence could allow them access to additional follow-up or surveillance., Objective: We sought to examine the prognostic value of the 31-gene expression profile (31-GEP) test for the risk of recurrence in stage I CM patients according to 31-GEP main class (low risk: Class 1 vs. high-risk: Class 2) and the lowest and highest risk 31-GEP subclasses (Class 1A vs. Class 2B)., Methods: Data from a previously described meta-analysis detailing the 31-GEP results for patients with stage I CM (N = 623) were re-analyzed to determine 31-GEP accuracy., Results: Patients with stage I CM and a Class 1 31-GEP result were less likely to have a recurrence (15/556; 2.7% vs. 6/67; 9.0%; p =0.018) than patients with a Class 2 result and had a higher five-year recurrence-free survival (RFS) (96% vs. 85%). Patients with a Class 2 result were 2.8 times as likely to experience a recurrence (positive likelihood ratio: 2.82; 95% confidence interval: 1.38-5.77). In a subset of patients with stage I CM stratified further into 31-GEP subclasses (n = 206), patients with a Class 1A result had a higher five-year RFS than those with a Class 2B result (98% vs. 73%). Patients with a Class 2B result were also 6.5 times as likely to experience a recurrence (positive likelihood ratio: 6.45; 95% confidence interval: 2.44-17.00) than those with a Class 1A result, and the 31-GEP had a negative predictive value of 96.3% (95% confidence interval: 92.3%-98.4%)., Conclusion: The 31-GEP test significantly differentiates between low and high recurrence risk in patients with stage I CM., Competing Interests: DISCLOSURES: All authors are employees with Castle Biosciences, Inc. in Friendswood, Texas., (Copyright © 2021. Matrix Medical Communications. All rights reserved.)

Proper cardiac Ca2+ homeostasis is essential for normal excitation-contraction coupling. Perturbations in cardiac Ca2+ handling through altered kinase activity has been implicated in altered cardiac contractility and arrhythmogenesis. Thus, a better understanding of cardiac Ca2+ handling regulation is vital for a better understanding of various human disease processes. 'Striated muscle preferentially expressed protein kinase' (SPEG) is a member of the myosin light chain kinase family that is key for normal cardiac function. Work within the last 5 years has revealed that SPEG has a crucial role in maintaining normal cardiac Ca2+ handling through maintenance of transverse tubule formation and phosphorylation of junctional membrane complex proteins. Additionally, SPEG has been causally impacted in human genetic diseases such as centronuclear myopathy and dilated cardiomyopathy as well as in common acquired cardiovascular disease such as heart failure and atrial fibrillation. Given the rapidly emerging role of SPEG as a key cardiac Ca2+ regulator, we here present this review in order to summarize recent findings regarding the mechanisms of SPEG regulation of cardiac excitation-contraction coupling in both physiology and human disease. A better understanding of the roles of SPEG will be important for a more complete comprehension of cardiac Ca2+ regulation in physiology and disease., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited cardiac arrhythmia syndrome that often leads to sudden cardiac death. The most common form of CPVT is caused by autosomal-dominant variants in the cardiac ryanodine receptor type-2 (RYR2) gene. Mutations in RYR2 promote calcium (Ca 2+ ) leak from the sarcoplasmic reticulum (SR), triggering lethal arrhythmias. Recently, it was demonstrated that tetracaine derivative EL20 specifically inhibits mutant RyR2, normalizes Ca 2+ handling and suppresses arrhythmias in a CPVT mouse model. The objective of this study was to determine whether EL20 normalizes SR Ca 2+ handling and arrhythmic events in induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from a CPVT patient. Blood samples from a child carrying RyR2 variant RyR2 variant Arg-176-Glu (R176Q) and a mutation-negative relative were reprogrammed into iPSCs using a Sendai virus system. iPSC-CMs were derived using the Stemdiff TM kit. Confocal Ca 2+ imaging was used to quantify RyR2 activity in the absence and presence of EL20. iPSC-CMs harbouring the R176Q variant demonstrated spontaneous SR Ca 2+ release events, whereas administration of EL20 diminished these abnormal events at low nanomolar concentrations (IC 50  = 82 nM). Importantly, treatment with EL20 did not have any adverse effects on systolic Ca 2+ handling in control iPSC-CMs. Our results show for the first time that tetracaine derivative EL20 normalized SR Ca 2+ handling and suppresses arrhythmogenic activity in iPSC-CMs derived from a CPVT patient. Hence, this study confirms that this RyR2-inhibitor represents a promising therapeutic candidate for treatment of CPVT., (© 2021 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

Purpose: Current guidelines for postoperative management of patients with stage I-IIA cutaneous melanoma (CM) do not recommend routine cross-sectional imaging, yet many of these patients develop metastases. Methods that complement American Joint Committee on Cancer (AJCC) staging are needed to improve identification and treatment of these patients. A 31-gene expression profile (31-GEP) test predicts metastatic risk as low (class 1) or high (class 2). Prospective analysis of CM outcomes was performed to test the hypotheses that the 31-GEP provides prognostic value for patients with stage I-III CM, and that patients with stage I-IIA melanoma and class 2 31-GEP results have metastatic risk similar to patients for whom surveillance is recommended., Materials and Methods: Two multicenter registry studies, INTEGRATE (ClinicalTrials.gov identifier:NCT02355574) and EXPAND (ClinicalTrials.gov identifier:NCT02355587), were initiated under institutional review board approval, and 323 patients with stage I-III CM and median follow-up time of 3.2 years met inclusion criteria. Primary end points were 3-year recurrence-free survival (RFS), distant metastasis-free survival (DMFS), and overall survival (OS)., Results: The 31-GEP was significant for RFS, DMFS, and OS in a univariate analysis and was a significant, independent predictor of RFS, DMFS, and OS in a multivariable analysis. GEP class 2 results were significantly associated with lower 3-year RFS, DMFS, and OS in all patients and those with stage I-IIA disease. Patients with stage I-IIA CM and a class 2 result had recurrence, distant metastasis, and death rates similar to patients with stage IIB-III CM. Combining 31-GEP results and AJCC staging enhanced sensitivity over each approach alone., Conclusion: These data provide a rationale for using the 31-GEP along with AJCC staging, and suggest that patients with stage I-IIA CM and a class 2 31-GEP signature may be candidates for more intense follow-up., Competing Interests: The following represents disclosure information provided by authors of this manuscript. All relationships are considered compensated unless otherwise noted. Relationships are self-held unless noted. I = Immediate Family Member, Inst = My Institution. Relationships may not relate to the subject matter of this manuscript. For more information about ASCO’s conflict of interest policy, please refer to www.asco.org/rwc or ascopubs.org/po/author-center. Open Payments is a public database containing information reported by companies about payments made to US-licensed physicians (Open Payments). Eddy C. Hsueh Speakers' Bureau: Amgen, Castle BiosciencesJeffrey J. Sussman Consulting or Advisory Role: Castle BiosciencesKyle R. Covington Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Gene expression profile tests Travel, Accommodations, Expenses: Castle BiosciencesHillary G. Caruso Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Chimeric antigen receptors (CARs) and CAR-expressing T cells are provided that can specifically target cells that express an elevated level of a target antigen. Likewise, methods for specifically targeting cells that express elevated levels of antigen (eg, cancer cells) with CAR T-cell therapies are provided Travel, Accommodations, Expenses: Castle BiosciencesAnn P. Quick Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Travel, Accommodations, Expenses: Castle BiosciencesRobert W. Cook Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Castle Biosciences related patents Travel, Accommodations, Expenses: Castle BiosciencesCraig L. Slingluff Consulting or Advisory Role: Immatics, Polynoma, CureVac Research Funding: GlaxoSmithKline, Merck Sharp & Dohme, 3M, Theraclion, Celldex Patents, Royalties, Other Intellectual Property: Licensing and Ventures Group of the University of Virginia Travel, Accommodations, Expenses: Polynoma Uncompensated Relationships: Agenus No other potential conflicts of interest were reported.Eddy C. Hsueh Speakers' Bureau: Amgen, Castle Biosciences Jeffrey J. Sussman Consulting or Advisory Role: Castle Biosciences Kyle R. Covington Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Gene expression profile tests Travel, Accommodations, Expenses: Castle Biosciences Hillary G. Caruso Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Chimeric antigen receptors (CARs) and CAR-expressing T cells are provided that can specifically target cells that express an elevated level of a target antigen. Likewise, methods for specifically targeting cells that express elevated levels of antigen (eg, cancer cells) with CAR T-cell therapies are provided Travel, Accommodations, Expenses: Castle Biosciences Ann P. Quick Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Travel, Accommodations, Expenses: Castle Biosciences Robert W. Cook Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Castle Biosciences related patents Travel, Accommodations, Expenses: Castle Biosciences Craig L. Slingluff Consulting or Advisory Role: Immatics, Polynoma, CureVac Research Funding: GlaxoSmithKline, Merck Sharp & Dohme, 3M, Theraclion, Celldex Patents, Royalties, Other Intellectual Property: Licensing and Ventures Group of the University of Virginia Travel, Accommodations, Expenses: Polynoma Uncompensated Relationships: Agenus No other potential conflicts of interest were reported.Eddy C. Hsueh Speakers' Bureau: Amgen, Castle Biosciences Jeffrey J. Sussman Consulting or Advisory Role: Castle Biosciences Kyle R. Covington Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Gene expression profile tests Travel, Accommodations, Expenses: Castle Biosciences Hillary G. Caruso Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Chimeric antigen receptors (CARs) and CAR-expressing T cells are provided that can specifically target cells that express an elevated level of a target antigen. Likewise, methods for specifically targeting cells that express elevated levels of antigen (eg, cancer cells) with CAR T-cell therapies are provided Travel, Accommodations, Expenses: Castle Biosciences Ann P. Quick Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Travel, Accommodations, Expenses: Castle Biosciences Robert W. Cook Employment: Castle Biosciences Stock and Other Ownership Interests: Castle Biosciences Patents, Royalties, Other Intellectual Property: Castle Biosciences related patents Travel, Accommodations, Expenses: Castle Biosciences Craig L. Slingluff Consulting or Advisory Role: Immatics, Polynoma, CureVac Research Funding: GlaxoSmithKline, Merck Sharp & Dohme, 3M, Theraclion, Celldex Patents, Royalties, Other Intellectual Property: Licensing and Ventures Group of the University of Virginia Travel, Accommodations, Expenses: Polynoma Uncompensated Relationships: Agenus No other potential conflicts of interest were reported., (© 2021 by American Society of Clinical Oncology.)

Background: Enhanced diastolic calcium (Ca 2+ ) release through ryanodine receptor type-2 (RyR2) has been implicated in atrial fibrillation (AF) promotion. Diastolic sarcoplasmic reticulum Ca 2+ leak is caused by increased RyR2 phosphorylation by PKA (protein kinase A) or CaMKII (Ca 2+ /calmodulin-dependent kinase-II) phosphorylation, or less dephosphorylation by protein phosphatases. However, considerable controversy remains regarding the molecular mechanisms underlying altered RyR2 function in AF. We thus aimed to determine the role of SPEG (striated muscle preferentially expressed protein kinase), a novel regulator of RyR2 phosphorylation, in AF pathogenesis., Methods: Western blotting was performed with right atrial biopsies from patients with paroxysmal AF. SPEG atrial knockout mice were generated using adeno-associated virus 9. In mice, AF inducibility was determined using intracardiac programmed electric stimulation, and diastolic Ca 2+ leak in atrial cardiomyocytes was assessed using confocal Ca 2+ imaging. Phosphoproteomics studies and Western blotting were used to measure RyR2 phosphorylation. To test the effects of RyR2-S2367 phosphorylation, knockin mice with an inactivated S2367 phosphorylation site (S2367A) and a constitutively activated S2367 residue (S2367D) were generated by using CRISPR-Cas9., Results: Western blotting revealed decreased SPEG protein levels in atrial biopsies from patients with paroxysmal AF in comparison with patients in sinus rhythm. SPEG atrial-specific knockout mice exhibited increased susceptibility to pacing-induced AF by programmed electric stimulation and enhanced Ca 2+ spark frequency in atrial cardiomyocytes with Ca 2+ imaging, establishing a causal role for decreased SPEG in AF pathogenesis. Phosphoproteomics in hearts from SPEG cardiomyocyte knockout mice identified RyR2-S2367 as a novel kinase substrate of SPEG. Western blotting demonstrated that RyR2-S2367 phosphorylation was also decreased in patients with paroxysmal AF. RyR2-S2367A mice exhibited an increased susceptibility to pacing-induced AF, and aberrant atrial sarcoplasmic reticulum Ca 2+ leak, as well. In contrast, RyR2-S2367D mice were resistant to pacing-induced AF., Conclusions: Unlike other kinases (PKA, CaMKII) that increase RyR2 activity, SPEG phosphorylation reduces RyR2-mediated sarcoplasmic reticulum Ca 2+ release. Reduced SPEG levels and RyR2-S2367 phosphorylation typified patients with paroxysmal AF. Studies in S2367 knockin mouse models showed a causal relationship between reduced S2367 phosphorylation and AF susceptibility. Thus, modulating SPEG activity and phosphorylation levels of the novel S2367 site on RyR2 may represent a novel target for AF treatment.

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. Patients with HF exhibit a loss of junctophilin-2 (JPH2), a structural protein critical in forming junctional membrane complexes in which excitation-contraction takes place. Several mechanisms have been proposed to mediate the loss of JPH2, one being cleavage by the calcium-dependent protease calpain. The downstream mechanisms underlying HF progression after JPH2 cleavage are presently poorly understood. In this study, we used Labcas to bioinformatically predict putative calpain cleavage sites on JPH2. We identified a cleavage site that produces a novel C-terminal JPH2 peptide (JPH2-CTP) using several domain-specific antibodies. Western blotting revealed elevated JPH2-CTP levels in hearts of patients and mice with HF, corresponding to increased levels of calpain-2. Moreover, immunocytochemistry demonstrated nuclear localization of JPH2-CTP within ventricular myocytes isolated from a murine model of pressure overload-induced HF as well as rat ventricular myocytes treated with isoproterenol. Nuclear localization of JPH2-CTP and cellular remodeling were abrogated by a genetic mutation of the nuclear localization sequence within JPH2-CTP. Taken together, our studies identified a novel C-terminal fragment of JPH2 (JPH2-CTP) generated by calpain-2 mediated cleavage which localizes within the cardiomyocyte nucleus during HF. Blocking nuclear localization of JPH2-CTP protects cardiomyocytes from isoproterenol-induced hypertrophy in vitro. Future in vivo studies of the nuclear role of JPH2-CTP may reveal a causal association with adverse remodeling during HF and establish CTP as a therapeutic target.

Background: Abnormal calcium (Ca 2+ ) release from the sarcoplasmic reticulum (SR) contributes to the pathogenesis of atrial fibrillation (AF). Increased phosphorylation of 2 proteins essential for normal SR-Ca 2+ cycling, the type-2 ryanodine receptor (RyR2) and phospholamban (PLN), enhances the susceptibility to AF, but the underlying mechanisms remain unclear. Protein phosphatase 1 (PP1) limits steady-state phosphorylation of both RyR2 and PLN. Proteomic analysis uncovered a novel PP1-regulatory subunit (PPP1R3A [PP1 regulatory subunit type 3A]) in the RyR2 macromolecular channel complex that has been previously shown to mediate PP1 targeting to PLN. We tested the hypothesis that reduced PPP1R3A levels contribute to AF pathogenesis by reducing PP1 binding to both RyR2 and PLN., Methods: Immunoprecipitation, mass spectrometry, and complexome profiling were performed from the atrial tissue of patients with AF and from cardiac lysates of wild-type and Pln-knockout mice. Ppp1r3a-knockout mice were generated by CRISPR-mediated deletion of exons 2 to 3. Ppp1r3a-knockout mice and wild-type littermates were subjected to in vivo programmed electrical stimulation to determine AF susceptibility. Isolated atrial cardiomyocytes were used for Stimulated Emission Depletion superresolution microscopy and confocal Ca 2+ imaging., Results: Proteomics identified the PP1-regulatory subunit PPP1R3A as a novel RyR2-binding partner, and coimmunoprecipitation confirmed PPP1R3A binding to RyR2 and PLN. Complexome profiling and Stimulated Emission Depletion imaging revealed that PLN is present in the PPP1R3A-RyR2 interaction, suggesting the existence of a previously unknown SR nanodomain composed of both RyR2 and PLN/sarco/endoplasmic reticulum calcium ATPase-2a macromolecular complexes. This novel RyR2/PLN/sarco/endoplasmic reticulum calcium ATPase-2a complex was also identified in human atria. Genetic ablation of Ppp1r3a in mice impaired binding of PP1 to both RyR2 and PLN. Reduced PP1 targeting was associated with increased phosphorylation of RyR2 and PLN, aberrant SR-Ca 2+ release in atrial cardiomyocytes, and enhanced susceptibility to pacing-induced AF. Finally, PPP1R3A was progressively downregulated in the atria of patients with paroxysmal and persistent (chronic) AF., Conclusions: PPP1R3A is a novel PP1-regulatory subunit within the RyR2 channel complex. Reduced PPP1R3A levels impair PP1 targeting and increase phosphorylation of both RyR2 and PLN. PPP1R3A deficiency promotes abnormal SR-Ca 2+ release and increases AF susceptibility in mice. Given that PPP1R3A is downregulated in patients with AF, this regulatory subunit may represent a new target for AF therapeutic strategies.

βIV-Spectrin, along with ankyrin and Ca2+/calmodulin-dependent kinase II (CaMKII), has been shown to form local signaling domains at the intercalated disc, while playing a key role in the regulation of Na+ and K+ channels in cardiomyocytes. In this issue of the JCI, Unudurthi et al. show that under chronic pressure overload conditions, CaMKII activation leads to βIV-spectrin degradation, resulting in the release of sequestered STAT3 from the intercalated discs. This in turn leads to dysregulation of STAT3-mediated gene transcription, maladaptive remodeling, fibrosis, and decreased cardiac function. Overall, this study presents interesting findings regarding the role of CaMKII and βIV-spectrin under physiological as well as pathological conditions.

Background: Duchenne muscular dystrophy patients are prone to ventricular arrhythmias, which may be caused by abnormal calcium (Ca 2+ ) homeostasis and elevated reactive oxygen species. CaMKII (Ca 2+ /calmodulin-dependent protein kinase II) is vital for normal Ca 2+ homeostasis, but excessive CaMKII activity contributes to abnormal Ca 2+ homeostasis and arrhythmias in cardiomyocytes. Reactive oxygen species induce CaMKII to become autonomously active. We hypothesized that genetic inhibition of CaMKII oxidation (ox-CaMKII) in a mouse model of Duchenne muscular dystrophy can alleviate abnormal Ca 2+ homeostasis, thus, preventing ventricular arrhythmia. The objective of this study was to test if selective loss of ox-CaMKII affects ventricular arrhythmias in the mdx mouse model of Duchenne muscular dystrophy., Methods and Results: 5-(6)-Chloromethyl-2,7-dichlorodihydrofluorescein diacetate staining revealed increased reactive oxygen species production in ventricular myocytes isolated from mdx mice, which coincides with elevated ventricular ox-CaMKII demonstrated by Western blotting. Genetic inhibition of ox-CaMKII by knockin replacement of the regulatory domain methionines with valines (MM-VV [CaMKII M281/282V]) prevented ventricular tachycardia in mdx mice. Confocal calcium imaging of ventricular myocytes isolated from mdx :MM-VV mice revealed normalization of intracellular Ca 2+ release events compared with cardiomyocytes from mdx mice. Abnormal action potentials assessed by optical mapping in mdx mice were also alleviated by genetic inhibition of ox-CaMKII. Knockout of the NADPH oxidase regulatory subunit p47 phox normalized elevated ox-CaMKII, repaired intracellular Ca 2+ homeostasis, and rescued inducible ventricular arrhythmias in mdx mice., Conclusions: Inhibition of reactive oxygen species or ox-CaMKII protects against proarrhythmic intracellular Ca 2+ handling and prevents ventricular arrhythmia in a mouse model of Duchenne muscular dystrophy., (© 2018 American Heart Association, Inc.)

Background: Hypertrophic cardiomyopathy (HCM), defined as asymmetric left ventricular hypertrophy, is a leading cause of cardiac death in the young. Perturbations in calcium (Ca 2+ ) handling proteins have been implicated in the pathogenesis of HCM. JPH2 -encoded junctophilin 2 is a major component of the junctional membrane complex, the subcellular microdomain involved in excitation-contraction coupling. We hypothesized that a novel JPH2 mutation identified in patients with HCM is causally linked to HCM, and alters intracellular Ca 2+ signaling in a pro-hypertrophic manner., Objectives: To determine using a transgenic mouse model whether a JPH2 mutation found in a HCM patient is responsible for disease development., Methods: Genetic interrogation of a large cohort of HCM cases was conducted for all coding exons of JPH2 . Pseudo-knock-in (PKI) mice containing a novel JPH2 variant were subjected to echocardiography, cardiac MRI, hemodynamic analysis, and histology., Results: A novel JPH2 mutation, A405S, was identified in a genotype-negative proband with significant basal septal hypertrophy. Although initially underappreciated by traditional echocardiographic imaging, PKI mice with this JPH2 mutation (residue A399S in mice) were found to exhibit similar basal hypertrophy using a newly developed echo imaging plane, and this was confirmed using cardiac MRI. Histological analysis demonstrated cardiomyocyte hypertrophy and disarray consistent with HCM., Conclusions: Variant A405S is a novel HCM-associated mutation in JPH2 found in a proband negative for mutations in the canonical HCM-associated genes. Studies in the analogous mouse model demonstrated for the first time a causal link between a JPH2 defect and HCM. Moreover, novel imaging approaches identified subvalvular septal hypertrophy, specific findings also reported in the human JPH2 mutation carrier.

Rationale: Junctional membrane complexes (JMCs) in myocytes are critical microdomains, in which excitation-contraction coupling occurs. Structural and functional disruption of JMCs underlies contractile dysfunction in failing hearts. However, the role of newly identified JMC protein SPEG (striated muscle preferentially expressed protein kinase) remains unclear., Objective: To determine the role of SPEG in healthy and failing adult hearts., Methods and Results: Proteomic analysis of immunoprecipitated JMC proteins ryanodine receptor type 2 and junctophilin-2 (JPH2) followed by mass spectrometry identified the serine-threonine kinase SPEG as the only novel binding partner for both proteins. Real-time polymerase chain reaction revealed the downregulation of SPEG mRNA levels in failing human hearts. A novel cardiac myocyte-specific Speg conditional knockout (MCM-Speg fl/fl ) model revealed that adult-onset SPEG deficiency results in heart failure (HF). Calcium (Ca 2+ ) and transverse-tubule imaging of ventricular myocytes from MCM-Speg fl/fl mice post HF revealed both increased sarcoplasmic reticulum Ca 2+ spark frequency and disrupted JMC integrity. Additional studies revealed that transverse-tubule disruption precedes the development of HF development in MCM-Speg fl/fl mice. Although total JPH2 levels were unaltered, JPH2 phosphorylation levels were found to be reduced in MCM-Speg fl/fl mice, suggesting that loss of SPEG phosphorylation of JPH2 led to transverse-tubule disruption, a precursor of HF development in SPEG-deficient mice., Conclusions: The novel JMC protein SPEG is downregulated in human failing hearts. Acute loss of SPEG in mouse hearts causes JPH2 dephosphorylation and transverse-tubule loss associated with downstream Ca 2+ mishandling leading to HF. Our study suggests that SPEG could be a novel target for the treatment of HF., (© 2016 American Heart Association, Inc.)

Framingham Heart Study suggests that dysfunction of steroid receptor coactivator-1 may be involved in the development of hypertension. However, there is no functional evidence linking steroid receptor coactivator-1 to the regulation of blood pressure. We used immunohistochemistry to map the expression of steroid receptor coactivator-1 protein in mouse brain, especially in regions implicated in the regulation of blood pressure. Steroid receptor coactivator-1 protein was found in central amygdala, medial amygdala, supraoptic nucleus, arcuate nucleus, ventromedial, dorsomedial, paraventricular hypothalamus, and nucleus of the solitary tract. To determine the effects of steroid receptor coactivator-1 protein on cardiovascular system we measured blood pressures, blood flow velocities, echocardiographic parameters, and aortic input impedance in female steroid receptor coactivator-1 knockout mice and their wild type littermates. Steroid receptor coactivator-1 knockout mice had higher blood pressures and increased aortic stiffness when compared to female wild type littermates. Additionally, the hearts of steroid receptor coactivator-1 knockout mice seem to consume higher energy as evidenced by increased impedance and higher heart rate pressure product when compared to female wild type littermates. Our results demonstrate that steroid receptor coactivator-1 may be functionally involved in the regulation of blood pressure and aortic stiffness through the regulation of sympathetic activation in various neuronal populations., Competing Interests: Dr. Xander Wehrens serves as guest editor for PLOS ONE. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials. Regarding employment with commercial entity, Indus Instruments, Dr. Reddy regularly reports any significant financial conflicts to the Department of Medicine at Baylor College of Medicine.

Background: Junctophilin-2 (JPH2) is the primary structural protein for the coupling of transverse (T)-tubule associated cardiac L-type Ca channels and type-2 ryanodine receptors on the sarcoplasmic reticulum within junctional membrane complexes (JMCs) in cardiomyocytes. Effective signaling between these channels ensures adequate Ca-induced Ca release required for normal cardiac contractility. Disruption of JMC subcellular domains, a common feature of failing hearts, has been attributed to JPH2 downregulation. Here, we tested the hypothesis that adeno-associated virus type 9 (AAV9) mediated overexpression of JPH2 could halt the development of heart failure in a mouse model of transverse aortic constriction (TAC)., Methods and Results: Following TAC, a progressive decrease in ejection fraction was paralleled by a progressive decrease of cardiac JPH2 levels. AAV9-mediated expression of JPH2 rescued cardiac contractility in mice subjected to TAC. AAV9-JPH2 also preserved T-tubule structure. Moreover, the Ca 2+ spark frequency was reduced and the Ca 2+ transient amplitude was increased in AAV9-JPH2 mice following TAC, consistent with JPH2-mediated normalization of SR Ca 2+ handling., Conclusions: This study demonstrates that AAV9-mediated JPH2 gene therapy maintained cardiac function in mice with early stage heart failure. Moreover, restoration of JPH2 levels prevented loss of T-tubules and suppressed abnormal SR Ca 2+ leak associated with contractile failure following TAC. These findings suggest that targeting JPH2 might be an attractive therapeutic approach for treating pathological cardiac remodeling during heart failure., Competing Interests: 6. CONFLICT OF INTEREST None declared., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Aims: Altered Ca(2+) handling in atrial fibrillation (AF) has been associated with dysregulated protein phosphatase 1 (PP1) and subcellular heterogeneities in protein phosphorylation, but the underlying mechanisms remain unclear. This is due to a lack of investigation into the local, rather than global, regulation of PP1 on different subcellular targets such as ryanodine receptor type 2 (RyR2), especially in AF., Methods and Results: We tested the hypothesis that impaired local regulation of PP1 causes RyR2 hyperphosphorylation thereby promoting AF susceptibility. To specifically disrupt PP1's local regulation of RyR2, we used the spinophilin knockout (Sp(-/-)) mice (Mus musculus) since PP1 is targeted to RyR2 via spinophilin. Without spinophilin, the interaction between PP1 and RyR2 was reduced by 64%, while RyR2 phosphorylation was increased by 43% at serine (S)2814 but unchanged at S2808. Lipid bilayer experiments revealed that single RyR2 channels isolated from Sp(-/-) hearts had an increased open probability. Likewise, Ca(2+) spark frequency normalized to sarcoplasmic reticulum Ca(2+) content was also enhanced in Sp(-/-) atrial myocytes, but normalized by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibitors KN-93 and AIP and also by genetic inhibition of RyR2 S2814 phosphorylation. Finally, Sp(-/-) mice exhibited increased atrial ectopy and susceptibility to pacing-induced AF, both of which were also prevented by the RyR2 S2814A mutation., Conclusion: PP1 regulates RyR2 locally by counteracting CaMKII phosphorylation of RyR2. Decreased local PP1 regulation of RyR2 contributes to RyR2 hyperactivity and promotes AF susceptibility. This represents a novel mechanism for subcellular modulation of calcium channels and may represent a potential drug target of AF., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.)