Identification of Novel Genetic Variants and Biomarkers of Disease Progression in Arrhythmogenic Cardiomyopathy

Sudden cardiac arrest (SCA) accounts for over 360,000 deaths in the US and 400,000 in Europe per annum, including thousands under the age of 40 who die unexpectedly and without warning. Whilst the majority of SCAs are triggered by heart attacks, in those under the age of 40 years this tends to be due to genetic heart disease, which if identified early may save lives of other family members. Epidemiological and post-mortem studies have shown arrhythmogenic ventricular cardiomyopathy (AVC) as a leading cause of SCA, responsible for up to 25% of deaths in this age group.

AVC is a highly clinically and genetically heterogeneous condition, which results in fibro-fatty replacement of myocardium which may lead to ventricular dysfunction, heart failure, electrical rhythm disturbances and SCD. Although AVC predominantly affects the right ventricle (ARVC), it can affect both the right and left ventricle, or the LV in isolation (ALVC) and result in a type of dilated cardiomyopathy (DCM) with a propensity for arrhythmia (aDCM). Recent reports of aDCM with a familial distribution suggests this is undiagnosed AVC, reflecting heterogeneity and limited understanding. AVC is considered a disease of the desmosome (cell-adhesion proteins) and this has led to identification of desmosomal mutations (plakoglobin, plakophilin-2, desmoplakin, desmoglein-2 and desmocollin), mostly inherited in an autosomal dominant manner with incomplete penetrance and variable expressivity. Non-desmosomal genes have also been discovered (desmin, titin, RYR2, transforming growth factor -3, transmembrane protein 43 and phospholamban). Together, these only account for 50-60% of known AVc-related mutations, with the remainder being genetically undetermined. Additionally, multiple mutations also exist within families and within individuals further compounding the complexity of AVC. Inter and intra-familial variability is inexplicable with current knowledge, and suggests epigenetic and environmental factors contributing to phenotype. Disease expression is highly variable even amongst members of the same family with the same mutation making clinical detection and cascade screening a challenge. Finally, predicting which patients are at risk of SCD who have AVC or may have AVC is difficult and potentially lethal. Since SCD can be the first lethal and tragic manifestation of the disease, optimizing screening strategies is of paramount importance. The long-term goals of this program are to leverage our well-phenotyped cohort of patients with AVC at Mayo Clinic and Papworth Hospital, University of Cambridge, , enroll others and to discover novel pathogenic variants, correlate genotype with phenotype, and develop robust screening tools for the diagnosis of AVC and preventing SCD.

Overall hypothesis: that the onset of AVC can be reliably and accurately predicted in first-degree relatives of index cases using genetic, electrocardiographic (ECG) and imaging data.

Aim #1: Identify novel candidate genes and variants associated with AVC (including cases involving the right, left and the dilated cardiomyopathy types). This aim will be accomplished using next generation sequencing of probands-family member trios "genomic familial triangulation" approach and an innovative bioinformatics, statistical, and systems based biology approach.

Aim #2: Correlate genotype with phenotype in confirmed cases of AVC followed longitudinally using clinical, ECG and imaging data to 2a. predict disease onset; 2b. predict disease progression; and 2c. predict the likelihood of arrhythmia (ventricular, supra-ventricular and atrial fibrillation).