Compound and Digenic Heterozygosity Contributes to Arrhythmogenic Right Ventricular Cardiomyopathy

Abstract

Objective: To define the genetic basis of arrhythmogenic right ventricular cardiomyopathy. Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC), characterized by right ventricular fibrofatty replacement and arrhythmias, causes sudden death. Autosomal dominant Inheritance, reduced penetrance, and 7 desmosome-encoding causative genes are known. The basis of low penetrance is poorly understood. Methods: ARVC probands and family members were enrolled, blood obtained, lymphoblastoid cell lines immortalized, DNA extracted, PCR amplification of desmosome-encoding genes performed, PCR products sequenced and diseased tissue samples studied for intercellular junction protein distribution using confocal immunofluorescence microscopy and antibodies against key proteins. Results: We identified 21 variants in plakophilin-2 (PKP2) in 38 of 198 probands (19%), including missense, nonsense, splice site, and deletion/insertion mutations. Pedigrees showed wide intra-familial variability (severe early-onset disease to asymptomatic individuals). In 9/38 probands, PKP2 variants were identified that were encoded in trans (compound heterozygosity). The 38 probands hosting PKP2 variants were screened for other desmosomal genes mutations; second variants (digenic heterozygosity) were identified in 16/38 subjects with PKP2 variants (42%) including desmoplakin (DSP, n=6), desmoglein-2 (DSG2, n=5), plakophilin-4 (PKP4, n=1), and desmocollin-2 (DSC2, n=1). Heterozygous mutations in non-PKP 2desmosomal genes occurred in 14/198 subjects (7%), including DSP (n=4), DSG2 (n=5), DSC2 (n=3), and junctional plakoglobin (JUP, n=2). All variants occurred in conserved regions; none were identified in 700 ethnic-matched controls. Immunohistochemical analysis demonstrated abnormalities of protein architecture. Conclusions: These data suggest that the genetic basis of ARVC includes reduced penetrance with compound and digenic heterozygosity. Disturbed junctional cytoarchitecture in subjects with desmosomal mutations confirms that ARVC is a disease of the desmosome and cell junction.

Clinical utility gene card for: arrhythmogenic right ventricular cardiomyopathy (ARVC)

“…Nevertheless, because carriership of multiple pathogenic mutations in more than one gene has been reported, 5,13,17,18 this mutation-negative family member may carry an yet unidentified ARVC-related mutation.…”

“…Among these, PKP2 is the most prevalent mutated gene responsible for 11-51% of ARVC patients. [11][12][13] In certain populations, specific mutations can be found often due to a founder effect, such as the PLN p.Arg14del and PKP2 p.Arg79* mutations in the Netherlands and the TMEM43 p.Ser358Leu mutation in Newfoundland, Canada. [14][15][16] ARVC patients carrying more than one disease-associated mutation often show a more severe phenotype, characterized by a younger age of onset and worse prognosis, suggesting a gene-dosage effect.…”

“…[14][15][16] ARVC patients carrying more than one disease-associated mutation often show a more severe phenotype, characterized by a younger age of onset and worse prognosis, suggesting a gene-dosage effect. 5,13,17,18 It is to be expected that the use of NGS techniques will result in the identification of an increasing number of patients with such complex genotypes.…”

“…On average, the mutation detection rate for the most common ARVC-related genes are: PKP2 11-51%, DSG2 3-20%, DSC2 1-7%, JUP 0.5-16% and DSP 1-7%. 5,12,13,[17][18][19][20][21] …”

“…However, as carriership of multiple disease-causing or -modifying mutations in one or more genes has been reported, it cannot be excluded that this mutation-negative family member carries a still unidentified ARVCrelated mutation. 5,13,17,18 Index case in that family had not been tested: ARVC is believed to be familial in B30-50% of cases. 1,8,9,20 Therefore, when an index patient has been clinically diagnosed with ARVC, and no genetic test has been performed, the chance for a firstdegree relative to develop ARVC may reach up to 15-25%.…”