Identification of novel mutations including a double mutation in patients with inherited cardiomyopathy by a targeted sequencing approach using the Ion Torrent PGM system.

Inherited cardiomyopathy is the major cause of sudden cardiac death (SCD) and heart failure (HF). The disease is associated with extensive genetic heterogeneity; pathogenic mutations in cardiac sarcomere protein genes, cytoskeletal protein genes and nuclear envelope protein genes have been linked to its etiology. Early diagnosis is conducive to clinical monitoring and allows for presymptomatic interventions as needed. In the present study, the entire coding sequences and flanking regions of 12 major disease (cardiomyopathy)-related genes [namely myosin, heavy chain 7, cardiac muscle, β (MYH7); myosin binding protein C, cardiac (MYBPC3); lamin A/C (LMNA); troponin I type 3 (cardiac) (TNNI3); troponin T type 2 (cardiac) (TNNT2); actin, α, cardiac muscle 1 (ACTC1); tropomyosin 1 (α) (TPM1); sodium channel, voltage gated, type V alpha subunit (SCN5A); myosin, light chain 2, regulatory, cardiac, slow (MYL2); myosin, heavy chain 6, cardiac muscle, α (MYH6); myosin, light chain 3, alkali, ventricular, skeletal, slow (MYL3); and protein kinase, AMP-activated, gamma 2 non-catalytic subunit  (PRKAG2)] in 8 patients with dilated cardiomyopathy (DCM) and in 8 patients with hypertrophic cardiomyopathy (HCM) were amplified and then sequenced using the Ion Torrent Personal Genome Machine (PGM) system. As a result, a novel heterozygous mutation (MYH7, p.Asn885Thr) and a variant of uncertain significance (TNNT2, p.Arg296His) were identified in 2 patients with HCM. These 2 missense mutations, which were absent in the samples obtained from the 200 healthy control subjects, altered the amino acid that was evolutionarily conserved among a number of vertebrate species; this illustrates that these 2 non-synonymous mutations play a role in the pathogenesis of HCM. Moreover, a double heterozygous mutation (PRKAG2, p.Gly100Ser plus MYH7, p.Arg719Trp) was identified in a patient with severe familial HCM, for the first time to the best of our knowledge. This patient provided us with more information regarding the genotype-phenotype correlation between mutations of MYH7 and PRKAG2. Taken together, these findings provide insight into the molecular mechanisms underlying inherited cardiomyopathy. The mutations identified in this study may be further investigated in the future in order to improve the diagnosis and treatment of patients with inherited cardiomyopathy. Furthermore, our findings indicated that sequencing using the Ion Torrent PGM system is a useful approach for the identification of pathogenic mutations associated with inherited cardiomyopathy, and it may be used for the risk evaluation of individuals with a possible susceptibility to inherited cardiomyopathy.