High-Throughput Diagnostic Assay for a Highly Prevalent Cardiomyopathy-Associated MYBPC3 Variant

Abstract

A 25-basepair deletion variant of MYBPC3 occurs at high frequency in individuals of South Asian descent and is estimated to affect 55 million people worldwide, carrying an increased likelihood of cardiomyopathy. Since this variant is prevalent and severe in this subpopulation, quick and affordable screening to provide risk-assessment to guide treatment for these patients is critical. An RNaseH qPCR assay was developed to quickly and specifically diagnose the presence of the 25-basepair deletion variant in MYBPC3. RNAseH-blocked nucleotide primers were designed to identify the presence or absence of the wild type MYBPC3 allele or the genomic sequence containing the 25-basepair deletion. Using this assay, three blinded operators were able to accurately determine the genotype from human genomic DNA samples from blood and saliva using a qPCR thermocycler. Furthermore, positive variant subjects were examined by both electrocardiography and echocardiography for the presence of cardiomyopathy. A simple, robust assay was established, verified and validated that can be automated to detect the presence of the highly prevalent 25-basepair deletion MYBPC3 variant using both blood and saliva samples. The assay will provide quick and accurate prescreening of individuals at high risk for cardiomyopathies and allow for better clinical identification of 25-basepair deletion MYBPC3 carriers in large cohort epidemiological studies.

Reevaluation of the South Asian MYBPC3 Δ25bp Intronic Deletion in Hypertrophic Cardiomyopathy

“…When the MYBPC3 Δ25 variant was first reported to be associated with cardiomyopathy in the South Asian population, it was thought likely to have a direct role in disease pathogenesis; since the initial report, it has come to be considered as one of the most compelling examples of a common, low-penetrance variant contributing to the genetic architecture of HCM. 3,[8][9][10][11][12] Genetic analyses undertaken in this study challenge these previous assertions and show that the MYBPC3 Δ25 variant does not directly confer an increased risk of cardiomyopathy but instead acts as a proxy marker for a rare, large effect size, intronic pathogenic variant, MYBPC3 c.1224-52G>A (Figure 3). Consequently, we conclude that heterozygosity for the MYBPC3 Δ25 common variant is not pathogenic for HCM.…”

Association of intronic DNA methylation and hydroxymethylation alterations in the epigenetic etiology of dilated cardiomyopathy

“…To determine changes in genomic DNA methylation in the DCM phenotype, we used a 3-mo-old male mouse model of DCM (t/t), in which the MYBPC3 (myosin binding protein-C) gene was mutated at the COOH-terminus, resulting in a cardiac myosin binding protein C null heart (34). We have extensively studied this mouse model to characterize and confirm the presence of DCM (6,7). In the present experimental setting, hearts were excised from wild-type (WT) and t/t mice, and gross images were captured under a stereomicroscope (SteREO Discovery.…”