Background: Mutations in desmoplakin ( DSP ), the primary force transducer between cardiac desmosomes and intermediate filaments, cause an arrhythmogenic form of cardiomyopathy that has been variably associated with arrhythmogenic right ventricular cardiomyopathy. Clinical correlates of DSP cardiomyopathy have been limited to small case series. Methods: Clinical and genetic data were collected on 107 patients with pathogenic DSP mutations and 81 patients with pathogenic plakophilin 2 ( PKP2 ) mutations as a comparison cohort. A composite outcome of severe ventricular arrhythmia was assessed. Results: DSP and PKP2 cohorts included similar proportions of probands (41% versus 42%) and patients with truncating mutations (98% versus 100%). Left ventricular (LV) predominant cardiomyopathy was exclusively present among patients with DSP (55% versus 0% for PKP2 , P <0.001), whereas right ventricular cardiomyopathy was present in only 14% of patients with DSP versus 40% for PKP2 ( P <0.001). Arrhythmogenic right ventricular cardiomyopathy diagnostic criteria had poor sensitivity for DSP cardiomyopathy. LV late gadolinium enhancement was present in a primarily subepicardial distribution in 40% of patients with DSP (23/57 with magnetic resonance images). LV late gadolinium enhancement occurred with normal LV systolic function in 35% (8/23) of patients with DSP . Episodes of acute myocardial injury (chest pain with troponin elevation and normal coronary angiography) occurred in 15% of patients with DSP and were strongly associated with LV late gadolinium enhancement (90%), even in cases of acute myocardial injury with normal ventricular function (4/5, 80% with late gadolinium enhancement). In 4 DSP cases with 18F-fluorodeoxyglucose positron emission tomography scans, acute LV myocardial injury was associated with myocardial inflammation misdiagnosed initially as cardiac sarcoidosis or myocarditis. Left ventricle ejection fraction <55% was strongly associated with severe ventricular arrhythmias for DSP cases ( P <0.001, sensitivity 85%, specificity 53%). Right ventricular ejection fraction <45% was associated with severe arrhythmias for PKP2 cases ( P <0.001) but was poorly associated for DSP cases ( P =0.8). Frequent premature ventricular contractions were common among patients with severe arrhythmias for both DSP (80%) and PKP2 (91%) groups ( P =non-significant). Conclusions: DSP cardiomyopathy is a distinct form of arrhythmogenic cardiomyopathy characterized by episodic myocardial injury, left ventricular fibrosis that precedes systolic dysfunction, and a high incidence of ventricular arrhythmias. A genotype-specific approach for diagnosis and risk stratification should be used.

Background Hypertrophic cardiomyopathy and dilated cardiomyopathy arise from mutations in genes encoding sarcomere proteins including MYH7, MYBPC3, and TTN. Genetic diagnosis of cardiomyopathy relies on complete sequencing of the gene coding regions, and most pathogenic variation is rare. The 1000 Genomes project is an ongoing consortium designed to deliver whole genome sequence information from an ethnically diverse population and therefore is a rich source to determine both common and rare genetic variants. Methods and Results We queried the 1000 Genomes database of 1,092 individuals for exonic variants within three sarcomere genes MHY7, MYBPC3, and TTN. We focused our analysis on protein-altering variation, including nonsynonymous single nucleotide polymorphisms, insertion/deletion polymorphisms, or splice site altering variants. We identified known and predicted pathogenic variation in MYBPC3 and MYH7 at a higher frequency than what would be expected based on the known prevalence of cardiomyopathy. We also found substantial variation, including protein-disrupting sequences, in TTN. Conclusions Cardiomyopathy is a genetically heterogeneous disorder caused by mutations in multiple genes. The frequency of predicted pathogenic protein altering variation in cardiomyopathy genes suggests that many of these variants may be insufficient to cause disease on their own but may modify phenotype in a genetically susceptible host. This is suggested by the high prevalence of TTN insertion/deletions in the 1000 Genomes cohort. Given the possibility of additional genetic variants that modify the phenotype of a primary driver mutation, broad-based genetic testing should be employed.

Huntington disease (HD) is a neurodegenerative condition characterized by cognitive impairments, motor abnormalities, and psychiatric disturbance. An increased risk for suicide has been documented. The majority of HD research has focused on cognitive and motor features of HD; the implications of psychiatric manifestations have received less consideration. Recent studies have sought to identify the stages of HD in which patients are at increased risk to experience suicidal ideation, though no study has examined possible risk factors for suicidality. The current study examines the presence of psychiatric comorbidity and its involvement in suicidal ideation. Suicidal ideation was examined in 1,941 HD patients enrolled in the Huntington Study Group. Of those, 19% (N = 369) reported suicidal ideation. Logistic regression analyses indicated that depression/anxiety and aggression/irritability are significant predictors of suicidal ideation (p < 0.01). In a subsample with the greatest suicidal ideation, alcohol and drug abuse were also predictive. Findings suggest that suicide in HD may be more distinct as compared to suicide in the general population. It is recommended that all individuals with HD (specifically those with features of depression, aggression, substance abuse) have routine suicide assessment; further research is needed to understand the high rate of suicide in HD.

The MegaSeq workflow is designed to harness the size and memory of the Cray XE6, housed at Argonne National Laboratory, for whole genome analysis in a platform designed to better match current and emerging sequencing volume.

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Rationale/Objective Cardiomyopathy and arrhythmias are under significant genetic influence. Here, we studied a family with dilated cardiomyopathy and associated conduction system disease in whom prior clinical cardiac gene panel testing was unrevealing. Methods/Results Whole genome sequencing and induced pluripotent stem cells were used to examine a family with dilated cardiomyopathy and atrial and ventricular arrhythmias. We also characterized a mouse model with heterozygous and homozygous deletion of Mybphl. Results Whole genome sequencing identified a premature stop codon, R255X, in the MYBPHL gene encoding myosin-binding protein-H like (MyBP-HL), a novel member of the myosin binding protein family. MYBPHL was found to have high atrial expression with low ventricular expression. We determined that MyBP-HL protein was myofilament-associated in the atria, and truncated MyBP-HL protein failed to incorporate into the myofilament. Human cell modeling demonstrated reduced expression from the mutant MYBPHL allele. Echocardiography of Mybphl heterozygous and null mouse hearts exhibited a 36% reduction in fractional shortening and an increased diastolic ventricular chamber size. Atria weight normalized to total heart weight was significantly increased in Mybphl heterozygous and null mice. Using a reporter system, we detected robust expression of Mybphl in the atria as well as in discrete puncta throughout the right ventricular wall and septum. Telemetric ECG recordings in Mybphl mice revealed cardiac conduction system abnormalities with aberrant atrioventricular conduction and an increased rate of arrhythmia in heterozygous and null mice. Conclusions The findings of reduced ventricular function and conduction system defects in Mybphl mice support that MYBPHL truncations may increase risk for human arrhythmias and cardiomyopathy.

Background Cardiomyopathy is highly heritable but genetically diverse. At present, genetic testing for cardiomyopathy uses targeted sequencing to simultaneously assess the coding regions of more than 50 genes. New genes are routinely added to panels to improve the diagnostic yield. With the anticipated $1000 genome, it is expected that genetic testing will shift towards comprehensive genome sequencing accompanied by targeted gene analysis. Therefore, we assessed the reliability of whole genome sequencing and targeted analysis to identify cardiomyopathy variants in 11 subjects with cardiomyopathy. Methods and Results Whole genome sequencing with an average of 37× coverage was combined with targeted analysis focused on 204 genes linked to cardiomyopathy. Genetic variants were scored using multiple prediction algorithms combined with frequency data from public databases. This pipeline yielded 1-14 potentially pathogenic variants per individual. Variants were further analyzed using clinical criteria and/or segregation analysis. Three of three previously identified primary mutations were detected by this analysis. In six subjects for whom the primary mutation was previously unknown, we identified mutations that segregated with disease, had clinical correlates, and/or had additional pathological correlation to provide evidence for causality. For two subjects with previously known primary mutations, we identified additional variants that may act as modifiers of disease severity. In total, we identified the likely pathological mutation in 9 of 11 (82%) subjects. Conclusions These pilot data demonstrate that ~30-40× coverage whole genome sequencing combined with targeted analysis is feasible and sensitive to identify rare variants in cardiomyopathy-associated genes.

BackgroundCellular models of muscle disease are taking on increasing importance with the large number of genes and mutations implicated in causing myopathies and the concomitant need to test personalized therapies. Developing cell models relies on having an easily obtained source of cells, and if the cells are not derived from muscle itself, a robust reprogramming process is needed. Fibroblasts are a human cell source that works well for the generation of induced pluripotent stem cells, which can then be differentiated into cardiomyocyte lineages, and with less efficiency, skeletal muscle-like lineages. Alternatively, direct reprogramming with the transcription factor MyoD has been used to generate myotubes from cultured human fibroblasts. Although useful, fibroblasts require a skin biopsy to obtain and this can limit their access, especially from pediatric populations.ResultsWe now demonstrate that direct reprogramming of urine-derived cells is a highly efficient and reproducible process that can be used to establish human myogenic cells. We show that this method can be applied to urine cells derived from normal individuals as well as those with muscle diseases. Furthermore, we show that urine-derived cells can be edited using CRISPR/Cas9 technology.ConclusionsWith progress in understanding the molecular etiology of human muscle diseases, having a readily available, noninvasive source of cells from which to generate muscle-like cells is highly useful.Electronic supplementary materialThe online version of this article (doi:10.1186/s13395-016-0103-9) contains supplementary material, which is available to authorized users.