The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

David E Clapham - One of the best experts on this subject based on the ideXlab platform.

  • abstract 48 cardiac targeted trpm7 deletion induces cardiomyopathy heart block and impaired ventricular repolarization via downregulation of KCND2 and hcn4
    Circulation Research, 2012
    Co-Authors: Rajan Sah, P Mesirca, Xenos Mason, Christopher Bateswithers, William J Gibson, Janice L Robertson, Matteo E Mangoni, David E Clapham
    Abstract:

    Transient Receptor Potential Melastatin-7 (TRPM7) is a divalent permeant channel-kinase of unknown function. It is concentrated in myocardium during embryonic development, and TRPM7-like current has been reported in adult ventricular myocytes. In atrial cardiac fibroblasts, TRPM7 has been implicated in fibrogenesis in patients with atrial fibrillation, however its function in ventricular myocardium is unexplored. We tested the hypothesis that TRPM7 is required for ventricular function by crossing TRPM7fl/- mice with the cardiac-targeted αMHC-Cre line (αMHC-TRPM7 KO). We show that TRPM7 forms a functional current in adult murine ventricular cardiomyocytes and demonstrate that ∼50% of αMHC-TRPM7 KO mice develop a cardiomyopathy with left ventricular dysfunction and cardiac hypertrophy, associated with heart block and impaired ventricular repolarization. This phenotype is associated with robust elevations in mRNA of Postn, Nppa, Timp1, Acta and reductions in Hdac9, Kcnv2, Kcnj3, KCND2, Lgi1 and Hcn4. Consistent with mRNA expression analysis and the observed electrical remodeling, patch-clamp of αMHC-Cre-TRPM7 KO ventricular myocytes (RV and LV) reveals significant action potential prolongation (2.5 to 4-fold increase in APD50) due to a 2 to 4-fold reduction in transient outward current (Ito, encoded by KCND2). Similarly, the funny current (If), encoded by Hcn4, is diminished 4-fold in atrioventricular nodal cells isolated from αMHC-Cre-Trpm7 KO hearts, accounting for the observed heart block. The ∼50% of αMHC-Cre-Trpm7 KO mice that do not develop cardiomyopathy are devoid of heart block, show normal expression levels of hypertrophy genes Postn, Nppa, and Acta, but continue to show significant reductions in KCND2, Lgi1, Kcnj3, Kcnv2, and Hdac9 expression. In conclusion, these results demonstrate that cardiac-targeted TRPM7 deletion dysregulates the expression of ion channels important for cardiomyocyte repolarization (KCND2) and atrioventricular conduction (Hcn4), leading to impaired ventricular repolarization and heart block in mice. The observed cardiomyopathy may arise from hemodynamic stresses secondary to chronic bradycardia from heart block in the setting of down-regulated histone deacetylase 9 (HDAC9).

  • Cardiac-Targeted TRPM7 Deletion Induces Heart Block and Cardiomyopathy via Disrupted Embryonic Ventricular Development
    Biophysical Journal, 2012
    Co-Authors: Christopher Bates-withers, Xenos Mason, William J Gibson, Marjolein Van Den Boogert, William T. Pu, David E Clapham
    Abstract:

    Transient Receptor Potential Melastatin-7 (Trpm7) is a divalent permeant channel-kinase of unknown function that is ubiquitously expressed, concentrated in myocardium during embryonic development, and forms a functional current in adult murine cardiac myocytes. Using multiple cardiac-targeted knock-out lines we show that the timing of Trpm7 deletion during embryonic development variably disrupts adult atrio-ventricular conduction, ventricular morphology and function without altering total myocardial magnesium, calcium or zinc content. Late embryonic cardiac Trpm7 deletion in αMHC-Cre-TRPM7fl/fl mice resulted in normal ventricular size and function, while slightly earlier deletion in αMHC-Cre-TRPM7fl/- mice yielded a bimodal phenotype in which ∼50% develop a dilated, fibrotic cardiomyopathy with impaired function and high grade atrioventricular block. Microarray analysis performed on αMHC-Cre-TRPM7fl/- ventricular tissue revealed 184 differentially expressed genes including significant elevations in Nppa (33-fold), Nppb (15-fold), TIMP1 (13-fold), Itgb1b3 (13-fold), Postn (12-fold) and reductions in Lgi-1 (20-fold), Pfkb1 (7-fold), Kcnv2 (Kv8.2) (5-fold), Mme (5-fold), Kcnj3 (GIRK1) (4-fold) and KCND2 (Kv4.2) (4-fold). To probe the importance of Trpm7 in early embryonic cardiac development, we crossed Trpm7flfl mice with Isl1-Cre and TnT-Cre lines. These early cardiac knock-outs developed congestive heart failure and died by E11 due to impaired formation of the compact myocardium secondary to arrested myocardial proliferation. Taken together, these results define an essential role for Trpm7 in normal embryonic myocardial development and suggest that adult cardiac phenotypes associated with disruptions in Trpm7 arise from defects in myocardial differentiation.

Michael J Ackerman - One of the best experts on this subject based on the ideXlab platform.

  • spectrum and prevalence of mutations from the first 2 500 consecutive unrelated patients referred for the familion long qt syndrome genetic test
    Heart Rhythm, 2009
    Co-Authors: Jamie D Kapplinger, David J Tester, Arthur A.m. Wilde, Benjamin A Salisbury, Janet L Carr, Carole Harriskerr, Guido D Pollevick, Michael J Ackerman
    Abstract:

    Background Long QT syndrome (LQTS) is a potentially lethal, highly treatable cardiac channelopathy for which genetic testing has matured from discovery to translation and now clinical implementation. Objectives Here we examine the spectrum and prevalence of mutations found in the first 2,500 unrelated cases referred for the FAMILION ® LQTS clinical genetic test. Methods Retrospective analysis of the first 2,500 cases (1,515 female patients, average age at testing 23 ± 17 years, range 0 to 90 years) scanned for mutations in 5 of the LQTS-susceptibility genes: KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6). Results Overall, 903 referral cases (36%) hosted a possible LQTS-causing mutation that was absent in >2,600 reference alleles; 821 (91%) of the mutation-positive cases had single genotypes, whereas the remaining 82 patients (9%) had >1 mutation in ≥1 gene, including 52 cases that were compound heterozygous with mutations in >1 gene. Of the 562 distinct mutations, 394 (70%) were missense, 428 (76%) were seen once, and 336 (60%) are novel, including 92 of 199 in KCNQ1 , 159 of 226 in KCNH2 , and 70 of 110 in SCN5A . Conclusion This cohort increases the publicly available compendium of putative LQTS-associated mutations by >50%, and approximately one-third of the most recently detected mutations continue to be novel. Although control population data suggest that the great majority of these mutations are pathogenic, expert interpretation of genetic test results will remain critical for effective clinical use of LQTS genetic test results.

  • genotypic heterogeneity and phenotypic mimicry among unrelated patients referred for catecholaminergic polymorphic ventricular tachycardia genetic testing
    Heart Rhythm, 2006
    Co-Authors: David J Tester, Carla M Haglund, Amanda L Farley, Jonathan C Makielski, Melissa L. Will, Puneeta Arya, Michael J Ackerman
    Abstract:

    Background Mutations in the RyR2 -encoded cardiac ryanodine receptor/calcium release channel and in CASQ2 -encoded calsequestrin cause catecholaminergic polymorphic ventricular tachycardia (CPVT1 and CPVT2, respectively). Objectives The purpose of this study was to evaluate the extent of genotypic and phenotypic heterogeneity among referrals for CPVT genetic testing. Methods Using denaturing high-performance liquid chromatography and DNA sequencing, mutational analysis of 23 RyR2 exons previously implicated in CPVT1, comprehensive analysis of all translated exons in CASQ2 (CPVT2), KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), KCNE2 (LQT6), and KCNJ2 (Andersen-Tawil syndrome [ATS1], also annotated LQT7), and analysis of 10 ANK2 exons implicated in LQT4 were performed on genomic DNA from 11 unrelated patients (8 females) referred to Mayo Clinic's Sudden Death Genomics Laboratory explicitly for CPVT genetic testing. Results Overall, putative disease causing mutations were identified in 8 patients (72%). Only 4 patients (3 males) hosted CPVT1-associated RyR2 mutations: P164S, V186M, S3938R, and T4196A. Interestingly, 4 females instead possessed either ATS1- or LQT5-associated mutations. Mutations were absent in >400 reference alleles. Conclusion Putative CPVT1-causing mutations in RyR2 were seen in

  • genotypic heterogeneity and phenotypic mimicry among unrelated patients referred for catecholaminergic polymorphic ventricular tachycardia genetic testing
    Heart Rhythm, 2006
    Co-Authors: David J Tester, Carla M Haglund, Amanda L Farley, Jonathan C Makielski, Melissa L. Will, Puneeta Arya, Michael J Ackerman
    Abstract:

    Background Mutations in the RyR2 -encoded cardiac ryanodine receptor/calcium release channel and in CASQ2 -encoded calsequestrin cause catecholaminergic polymorphic ventricular tachycardia (CPVT1 and CPVT2, respectively). Objectives The purpose of this study was to evaluate the extent of genotypic and phenotypic heterogeneity among referrals for CPVT genetic testing. Methods Using denaturing high-performance liquid chromatography and DNA sequencing, mutational analysis of 23 RyR2 exons previously implicated in CPVT1, comprehensive analysis of all translated exons in CASQ2 (CPVT2), KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), KCNE2 (LQT6), and KCNJ2 (Andersen-Tawil syndrome [ATS1], also annotated LQT7), and analysis of 10 ANK2 exons implicated in LQT4 were performed on genomic DNA from 11 unrelated patients (8 females) referred to Mayo Clinic's Sudden Death Genomics Laboratory explicitly for CPVT genetic testing. Results Overall, putative disease causing mutations were identified in 8 patients (72%). Only 4 patients (3 males) hosted CPVT1-associated RyR2 mutations: P164S, V186M, S3938R, and T4196A. Interestingly, 4 females instead possessed either ATS1- or LQT5-associated mutations. Mutations were absent in >400 reference alleles. Conclusion Putative CPVT1-causing mutations in RyR2 were seen in

  • compendium of cardiac channel mutations in 541 consecutive unrelated patients referred for long qt syndrome genetic testing
    Heart Rhythm, 2005
    Co-Authors: David J Tester, Carla M Haglund, Melissa L. Will, Michael J Ackerman
    Abstract:

    Objectives The purpose of this study was to determine the spectrum and prevalence of cardiac channel mutations among a large cohort of consecutive, unrelated patients referred for long QT syndrome (LQTS) genetic testing. Background Congenital LQTS is a primary cardiac channelopathy. More than 300 mutations have been identified in five genes encoding key ion channel subunits. Until the recent release of the commercial clinical genetic test, LQTS genetic testing had been performed in research laboratories during the past decade. Methods A cardiac channel gene screen for LQTS-causing mutations in KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6) was performed for 541 consecutive, unrelated patients (358 females, average age at diagnosis 24 ± 16 years, average QTc 482 ± 57 ms) referred to Mayo Clinic's Sudden Death Genomics Laboratory for LQTS genetic testing between August 1997 and July 2004. A comprehensive open reading frame and splice site analysis of the 60 protein-encoding exons was conducted using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing. Results Overall, 211 putative pathogenic mutations in KCNQ1 (88), KCNH2 (89), SCN5A (32), KCNE1 (1), and KCNE2 (1) were found in 272 unrelated patients (50%). Among the genotype positive patients (N = 272), 243 had single pathogenic mutations (LQT1: n=120 patients; LQT2: n=93; LQT3: n=26; LQT5: n=3; LQT6: n=1), and 29 patients (10% of genotype-positive patients and 5% overall) had two LQTS-causing mutations. The majority of mutations were missense mutations (154/210 [73%]), singletons (identified in only a single unrelated patient: 165/210 [79%]), and novel (125/211 [59%]). None of the mutations identified were seen in more than 1,500 reference alleles. Those patients harboring multiple mutations were younger at diagnosis (15 ± 11 years vs 24 ± 16 years, P =.003). Conclusions In this comprehensive cardiac channel gene screen of the largest cohort of consecutive, unrelated patients referred for LQTS genetic testing, half of the patients had an identifiable mutation. The majority of mutations continue to represent novel singletons that expand the published compendium of LQTS-causing mutations by 35%. These observations should facilitate diagnostic interpretation of the clinical genetic test for LQTS.

  • spectrum and frequency of cardiac channel defects in swimming triggered arrhythmia syndromes
    Circulation, 2004
    Co-Authors: Grace R Choi, Carla M Haglund, David J Tester, Melissa L. Will, Laura J Kopplin, Michael J Ackerman
    Abstract:

    Background— Swimming is a relatively genotype-specific arrhythmogenic trigger for type 1 long-QT syndrome (LQT1). We hypothesize that mimickers of concealed LQT1, namely catecholaminergic polymorphic ventricular tachycardia (CPVT), may also underlie swimming-triggered cardiac events. Methods and Results— Between August 1997 and May 2003, 388 consecutive, unrelated patients were referred specifically for LQTS genetic testing. The presence of a personal and/or family history of a near-drowning or drowning was determined by review of the medical records and/or phone interviews and was blinded to genetic test results. Comprehensive mutational analysis of the 5 LQTS-causing channel genes, KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6), along with KCNJ2 (Andersen-Tawil syndrome) and targeted analysis of 18 CPVT1-associated exons in RyR2, was performed with the use of denaturing high-performance liquid chromatography and direct DNA sequencing. Approximately 11% (43 of 388) of the index ...

William J Gibson - One of the best experts on this subject based on the ideXlab platform.

  • abstract 48 cardiac targeted trpm7 deletion induces cardiomyopathy heart block and impaired ventricular repolarization via downregulation of KCND2 and hcn4
    Circulation Research, 2012
    Co-Authors: Rajan Sah, P Mesirca, Xenos Mason, Christopher Bateswithers, William J Gibson, Janice L Robertson, Matteo E Mangoni, David E Clapham
    Abstract:

    Transient Receptor Potential Melastatin-7 (TRPM7) is a divalent permeant channel-kinase of unknown function. It is concentrated in myocardium during embryonic development, and TRPM7-like current has been reported in adult ventricular myocytes. In atrial cardiac fibroblasts, TRPM7 has been implicated in fibrogenesis in patients with atrial fibrillation, however its function in ventricular myocardium is unexplored. We tested the hypothesis that TRPM7 is required for ventricular function by crossing TRPM7fl/- mice with the cardiac-targeted αMHC-Cre line (αMHC-TRPM7 KO). We show that TRPM7 forms a functional current in adult murine ventricular cardiomyocytes and demonstrate that ∼50% of αMHC-TRPM7 KO mice develop a cardiomyopathy with left ventricular dysfunction and cardiac hypertrophy, associated with heart block and impaired ventricular repolarization. This phenotype is associated with robust elevations in mRNA of Postn, Nppa, Timp1, Acta and reductions in Hdac9, Kcnv2, Kcnj3, KCND2, Lgi1 and Hcn4. Consistent with mRNA expression analysis and the observed electrical remodeling, patch-clamp of αMHC-Cre-TRPM7 KO ventricular myocytes (RV and LV) reveals significant action potential prolongation (2.5 to 4-fold increase in APD50) due to a 2 to 4-fold reduction in transient outward current (Ito, encoded by KCND2). Similarly, the funny current (If), encoded by Hcn4, is diminished 4-fold in atrioventricular nodal cells isolated from αMHC-Cre-Trpm7 KO hearts, accounting for the observed heart block. The ∼50% of αMHC-Cre-Trpm7 KO mice that do not develop cardiomyopathy are devoid of heart block, show normal expression levels of hypertrophy genes Postn, Nppa, and Acta, but continue to show significant reductions in KCND2, Lgi1, Kcnj3, Kcnv2, and Hdac9 expression. In conclusion, these results demonstrate that cardiac-targeted TRPM7 deletion dysregulates the expression of ion channels important for cardiomyocyte repolarization (KCND2) and atrioventricular conduction (Hcn4), leading to impaired ventricular repolarization and heart block in mice. The observed cardiomyopathy may arise from hemodynamic stresses secondary to chronic bradycardia from heart block in the setting of down-regulated histone deacetylase 9 (HDAC9).

  • Cardiac-Targeted TRPM7 Deletion Induces Heart Block and Cardiomyopathy via Disrupted Embryonic Ventricular Development
    Biophysical Journal, 2012
    Co-Authors: Christopher Bates-withers, Xenos Mason, William J Gibson, Marjolein Van Den Boogert, William T. Pu, David E Clapham
    Abstract:

    Transient Receptor Potential Melastatin-7 (Trpm7) is a divalent permeant channel-kinase of unknown function that is ubiquitously expressed, concentrated in myocardium during embryonic development, and forms a functional current in adult murine cardiac myocytes. Using multiple cardiac-targeted knock-out lines we show that the timing of Trpm7 deletion during embryonic development variably disrupts adult atrio-ventricular conduction, ventricular morphology and function without altering total myocardial magnesium, calcium or zinc content. Late embryonic cardiac Trpm7 deletion in αMHC-Cre-TRPM7fl/fl mice resulted in normal ventricular size and function, while slightly earlier deletion in αMHC-Cre-TRPM7fl/- mice yielded a bimodal phenotype in which ∼50% develop a dilated, fibrotic cardiomyopathy with impaired function and high grade atrioventricular block. Microarray analysis performed on αMHC-Cre-TRPM7fl/- ventricular tissue revealed 184 differentially expressed genes including significant elevations in Nppa (33-fold), Nppb (15-fold), TIMP1 (13-fold), Itgb1b3 (13-fold), Postn (12-fold) and reductions in Lgi-1 (20-fold), Pfkb1 (7-fold), Kcnv2 (Kv8.2) (5-fold), Mme (5-fold), Kcnj3 (GIRK1) (4-fold) and KCND2 (Kv4.2) (4-fold). To probe the importance of Trpm7 in early embryonic cardiac development, we crossed Trpm7flfl mice with Isl1-Cre and TnT-Cre lines. These early cardiac knock-outs developed congestive heart failure and died by E11 due to impaired formation of the compact myocardium secondary to arrested myocardial proliferation. Taken together, these results define an essential role for Trpm7 in normal embryonic myocardial development and suggest that adult cardiac phenotypes associated with disruptions in Trpm7 arise from defects in myocardial differentiation.

Xenos Mason - One of the best experts on this subject based on the ideXlab platform.

  • abstract 48 cardiac targeted trpm7 deletion induces cardiomyopathy heart block and impaired ventricular repolarization via downregulation of KCND2 and hcn4
    Circulation Research, 2012
    Co-Authors: Rajan Sah, P Mesirca, Xenos Mason, Christopher Bateswithers, William J Gibson, Janice L Robertson, Matteo E Mangoni, David E Clapham
    Abstract:

    Transient Receptor Potential Melastatin-7 (TRPM7) is a divalent permeant channel-kinase of unknown function. It is concentrated in myocardium during embryonic development, and TRPM7-like current has been reported in adult ventricular myocytes. In atrial cardiac fibroblasts, TRPM7 has been implicated in fibrogenesis in patients with atrial fibrillation, however its function in ventricular myocardium is unexplored. We tested the hypothesis that TRPM7 is required for ventricular function by crossing TRPM7fl/- mice with the cardiac-targeted αMHC-Cre line (αMHC-TRPM7 KO). We show that TRPM7 forms a functional current in adult murine ventricular cardiomyocytes and demonstrate that ∼50% of αMHC-TRPM7 KO mice develop a cardiomyopathy with left ventricular dysfunction and cardiac hypertrophy, associated with heart block and impaired ventricular repolarization. This phenotype is associated with robust elevations in mRNA of Postn, Nppa, Timp1, Acta and reductions in Hdac9, Kcnv2, Kcnj3, KCND2, Lgi1 and Hcn4. Consistent with mRNA expression analysis and the observed electrical remodeling, patch-clamp of αMHC-Cre-TRPM7 KO ventricular myocytes (RV and LV) reveals significant action potential prolongation (2.5 to 4-fold increase in APD50) due to a 2 to 4-fold reduction in transient outward current (Ito, encoded by KCND2). Similarly, the funny current (If), encoded by Hcn4, is diminished 4-fold in atrioventricular nodal cells isolated from αMHC-Cre-Trpm7 KO hearts, accounting for the observed heart block. The ∼50% of αMHC-Cre-Trpm7 KO mice that do not develop cardiomyopathy are devoid of heart block, show normal expression levels of hypertrophy genes Postn, Nppa, and Acta, but continue to show significant reductions in KCND2, Lgi1, Kcnj3, Kcnv2, and Hdac9 expression. In conclusion, these results demonstrate that cardiac-targeted TRPM7 deletion dysregulates the expression of ion channels important for cardiomyocyte repolarization (KCND2) and atrioventricular conduction (Hcn4), leading to impaired ventricular repolarization and heart block in mice. The observed cardiomyopathy may arise from hemodynamic stresses secondary to chronic bradycardia from heart block in the setting of down-regulated histone deacetylase 9 (HDAC9).

  • Cardiac-Targeted TRPM7 Deletion Induces Heart Block and Cardiomyopathy via Disrupted Embryonic Ventricular Development
    Biophysical Journal, 2012
    Co-Authors: Christopher Bates-withers, Xenos Mason, William J Gibson, Marjolein Van Den Boogert, William T. Pu, David E Clapham
    Abstract:

    Transient Receptor Potential Melastatin-7 (Trpm7) is a divalent permeant channel-kinase of unknown function that is ubiquitously expressed, concentrated in myocardium during embryonic development, and forms a functional current in adult murine cardiac myocytes. Using multiple cardiac-targeted knock-out lines we show that the timing of Trpm7 deletion during embryonic development variably disrupts adult atrio-ventricular conduction, ventricular morphology and function without altering total myocardial magnesium, calcium or zinc content. Late embryonic cardiac Trpm7 deletion in αMHC-Cre-TRPM7fl/fl mice resulted in normal ventricular size and function, while slightly earlier deletion in αMHC-Cre-TRPM7fl/- mice yielded a bimodal phenotype in which ∼50% develop a dilated, fibrotic cardiomyopathy with impaired function and high grade atrioventricular block. Microarray analysis performed on αMHC-Cre-TRPM7fl/- ventricular tissue revealed 184 differentially expressed genes including significant elevations in Nppa (33-fold), Nppb (15-fold), TIMP1 (13-fold), Itgb1b3 (13-fold), Postn (12-fold) and reductions in Lgi-1 (20-fold), Pfkb1 (7-fold), Kcnv2 (Kv8.2) (5-fold), Mme (5-fold), Kcnj3 (GIRK1) (4-fold) and KCND2 (Kv4.2) (4-fold). To probe the importance of Trpm7 in early embryonic cardiac development, we crossed Trpm7flfl mice with Isl1-Cre and TnT-Cre lines. These early cardiac knock-outs developed congestive heart failure and died by E11 due to impaired formation of the compact myocardium secondary to arrested myocardial proliferation. Taken together, these results define an essential role for Trpm7 in normal embryonic myocardial development and suggest that adult cardiac phenotypes associated with disruptions in Trpm7 arise from defects in myocardial differentiation.

David J Tester - One of the best experts on this subject based on the ideXlab platform.

  • spectrum and prevalence of mutations from the first 2 500 consecutive unrelated patients referred for the familion long qt syndrome genetic test
    Heart Rhythm, 2009
    Co-Authors: Jamie D Kapplinger, David J Tester, Arthur A.m. Wilde, Benjamin A Salisbury, Janet L Carr, Carole Harriskerr, Guido D Pollevick, Michael J Ackerman
    Abstract:

    Background Long QT syndrome (LQTS) is a potentially lethal, highly treatable cardiac channelopathy for which genetic testing has matured from discovery to translation and now clinical implementation. Objectives Here we examine the spectrum and prevalence of mutations found in the first 2,500 unrelated cases referred for the FAMILION ® LQTS clinical genetic test. Methods Retrospective analysis of the first 2,500 cases (1,515 female patients, average age at testing 23 ± 17 years, range 0 to 90 years) scanned for mutations in 5 of the LQTS-susceptibility genes: KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6). Results Overall, 903 referral cases (36%) hosted a possible LQTS-causing mutation that was absent in >2,600 reference alleles; 821 (91%) of the mutation-positive cases had single genotypes, whereas the remaining 82 patients (9%) had >1 mutation in ≥1 gene, including 52 cases that were compound heterozygous with mutations in >1 gene. Of the 562 distinct mutations, 394 (70%) were missense, 428 (76%) were seen once, and 336 (60%) are novel, including 92 of 199 in KCNQ1 , 159 of 226 in KCNH2 , and 70 of 110 in SCN5A . Conclusion This cohort increases the publicly available compendium of putative LQTS-associated mutations by >50%, and approximately one-third of the most recently detected mutations continue to be novel. Although control population data suggest that the great majority of these mutations are pathogenic, expert interpretation of genetic test results will remain critical for effective clinical use of LQTS genetic test results.

  • genotypic heterogeneity and phenotypic mimicry among unrelated patients referred for catecholaminergic polymorphic ventricular tachycardia genetic testing
    Heart Rhythm, 2006
    Co-Authors: David J Tester, Carla M Haglund, Amanda L Farley, Jonathan C Makielski, Melissa L. Will, Puneeta Arya, Michael J Ackerman
    Abstract:

    Background Mutations in the RyR2 -encoded cardiac ryanodine receptor/calcium release channel and in CASQ2 -encoded calsequestrin cause catecholaminergic polymorphic ventricular tachycardia (CPVT1 and CPVT2, respectively). Objectives The purpose of this study was to evaluate the extent of genotypic and phenotypic heterogeneity among referrals for CPVT genetic testing. Methods Using denaturing high-performance liquid chromatography and DNA sequencing, mutational analysis of 23 RyR2 exons previously implicated in CPVT1, comprehensive analysis of all translated exons in CASQ2 (CPVT2), KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), KCNE2 (LQT6), and KCNJ2 (Andersen-Tawil syndrome [ATS1], also annotated LQT7), and analysis of 10 ANK2 exons implicated in LQT4 were performed on genomic DNA from 11 unrelated patients (8 females) referred to Mayo Clinic's Sudden Death Genomics Laboratory explicitly for CPVT genetic testing. Results Overall, putative disease causing mutations were identified in 8 patients (72%). Only 4 patients (3 males) hosted CPVT1-associated RyR2 mutations: P164S, V186M, S3938R, and T4196A. Interestingly, 4 females instead possessed either ATS1- or LQT5-associated mutations. Mutations were absent in >400 reference alleles. Conclusion Putative CPVT1-causing mutations in RyR2 were seen in

  • genotypic heterogeneity and phenotypic mimicry among unrelated patients referred for catecholaminergic polymorphic ventricular tachycardia genetic testing
    Heart Rhythm, 2006
    Co-Authors: David J Tester, Carla M Haglund, Amanda L Farley, Jonathan C Makielski, Melissa L. Will, Puneeta Arya, Michael J Ackerman
    Abstract:

    Background Mutations in the RyR2 -encoded cardiac ryanodine receptor/calcium release channel and in CASQ2 -encoded calsequestrin cause catecholaminergic polymorphic ventricular tachycardia (CPVT1 and CPVT2, respectively). Objectives The purpose of this study was to evaluate the extent of genotypic and phenotypic heterogeneity among referrals for CPVT genetic testing. Methods Using denaturing high-performance liquid chromatography and DNA sequencing, mutational analysis of 23 RyR2 exons previously implicated in CPVT1, comprehensive analysis of all translated exons in CASQ2 (CPVT2), KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), KCNE2 (LQT6), and KCNJ2 (Andersen-Tawil syndrome [ATS1], also annotated LQT7), and analysis of 10 ANK2 exons implicated in LQT4 were performed on genomic DNA from 11 unrelated patients (8 females) referred to Mayo Clinic's Sudden Death Genomics Laboratory explicitly for CPVT genetic testing. Results Overall, putative disease causing mutations were identified in 8 patients (72%). Only 4 patients (3 males) hosted CPVT1-associated RyR2 mutations: P164S, V186M, S3938R, and T4196A. Interestingly, 4 females instead possessed either ATS1- or LQT5-associated mutations. Mutations were absent in >400 reference alleles. Conclusion Putative CPVT1-causing mutations in RyR2 were seen in

  • compendium of cardiac channel mutations in 541 consecutive unrelated patients referred for long qt syndrome genetic testing
    Heart Rhythm, 2005
    Co-Authors: David J Tester, Carla M Haglund, Melissa L. Will, Michael J Ackerman
    Abstract:

    Objectives The purpose of this study was to determine the spectrum and prevalence of cardiac channel mutations among a large cohort of consecutive, unrelated patients referred for long QT syndrome (LQTS) genetic testing. Background Congenital LQTS is a primary cardiac channelopathy. More than 300 mutations have been identified in five genes encoding key ion channel subunits. Until the recent release of the commercial clinical genetic test, LQTS genetic testing had been performed in research laboratories during the past decade. Methods A cardiac channel gene screen for LQTS-causing mutations in KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6) was performed for 541 consecutive, unrelated patients (358 females, average age at diagnosis 24 ± 16 years, average QTc 482 ± 57 ms) referred to Mayo Clinic's Sudden Death Genomics Laboratory for LQTS genetic testing between August 1997 and July 2004. A comprehensive open reading frame and splice site analysis of the 60 protein-encoding exons was conducted using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing. Results Overall, 211 putative pathogenic mutations in KCNQ1 (88), KCNH2 (89), SCN5A (32), KCNE1 (1), and KCNE2 (1) were found in 272 unrelated patients (50%). Among the genotype positive patients (N = 272), 243 had single pathogenic mutations (LQT1: n=120 patients; LQT2: n=93; LQT3: n=26; LQT5: n=3; LQT6: n=1), and 29 patients (10% of genotype-positive patients and 5% overall) had two LQTS-causing mutations. The majority of mutations were missense mutations (154/210 [73%]), singletons (identified in only a single unrelated patient: 165/210 [79%]), and novel (125/211 [59%]). None of the mutations identified were seen in more than 1,500 reference alleles. Those patients harboring multiple mutations were younger at diagnosis (15 ± 11 years vs 24 ± 16 years, P =.003). Conclusions In this comprehensive cardiac channel gene screen of the largest cohort of consecutive, unrelated patients referred for LQTS genetic testing, half of the patients had an identifiable mutation. The majority of mutations continue to represent novel singletons that expand the published compendium of LQTS-causing mutations by 35%. These observations should facilitate diagnostic interpretation of the clinical genetic test for LQTS.

  • spectrum and frequency of cardiac channel defects in swimming triggered arrhythmia syndromes
    Circulation, 2004
    Co-Authors: Grace R Choi, Carla M Haglund, David J Tester, Melissa L. Will, Laura J Kopplin, Michael J Ackerman
    Abstract:

    Background— Swimming is a relatively genotype-specific arrhythmogenic trigger for type 1 long-QT syndrome (LQT1). We hypothesize that mimickers of concealed LQT1, namely catecholaminergic polymorphic ventricular tachycardia (CPVT), may also underlie swimming-triggered cardiac events. Methods and Results— Between August 1997 and May 2003, 388 consecutive, unrelated patients were referred specifically for LQTS genetic testing. The presence of a personal and/or family history of a near-drowning or drowning was determined by review of the medical records and/or phone interviews and was blinded to genetic test results. Comprehensive mutational analysis of the 5 LQTS-causing channel genes, KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6), along with KCNJ2 (Andersen-Tawil syndrome) and targeted analysis of 18 CPVT1-associated exons in RyR2, was performed with the use of denaturing high-performance liquid chromatography and direct DNA sequencing. Approximately 11% (43 of 388) of the index ...