A New Leu714Arg Variant in the Converter Domain of MYH7 is Associated with a Severe Form of Familial Hypertrophic Cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy is the most frequent autosomal dominant disease, yet due to genetic heterogeneity, incomplete penetrance, and phenotype variability, the prognosis of the disease course in pathogenic variant carriers remains an issue. Identifying common patterns among the effects of different genetic variants is important. METHODS: We investigated the cause of familial hypertrophic cardiomyopathy (HCM) in a family with two patients suffering from a particularly severe disease. Searching for the genetic variants in HCM genes was performed using different sequencing methods. RESULTS: A new missense variant, p.Leu714Arg, was identified in exon 19 of the beta-myosin heavy chain gene (MYH7). The mutation was found in a region that encodes the 'converter domain' in the globular myosin head. This domain is essential for the conformational change of myosin during ATP cleavage and contraction cycle. Most reports on different mutations in this region describe severe phenotypic consequences. The two patients with the p.Leu714Arg mutation had heart failure early in life and died from HCM complications. CONCLUSIONS: This case presents a new likely pathogenic variant in MYH7 and supports the hypothesis that myosin converter mutations constitute a subclass of HCM mutations with a poor prognosis for the patient.

Application of Long-Read Nanopore Sequencing to the Search for Mutations in Hypertrophic Cardiomyopathy.

Increasing evidence suggests that both coding and non-coding regions of sarcomeric protein genes can contribute to hypertrophic cardiomyopathy (HCM). Here, we introduce an experimental workflow (tested on four patients) for complete sequencing of the most common HCM genes (MYBPC3, MYH7, TPM1, TNNT2, and TNNI3) via long-range PCR, Oxford Nanopore Technology (ONT) sequencing, and bioinformatic analysis. We applied Illumina and Sanger sequencing to validate the results, FastQC, Qualimap, and MultiQC for quality evaluations, MiniMap2 to align data, Clair3 to call and phase variants, and Annovar's tools and CADD to assess pathogenicity of variants. We could not amplify the region encompassing exons 6-12 of MYBPC3. A higher sequencing error rate was observed with ONT (6.86-6.92%) than with Illumina technology (1.14-1.35%), mostly for small indels. Pathogenic variant p.Gln1233Ter and benign polymorphism p.Arg326Gln in MYBPC3 in a heterozygous state were found in one patient. We demonstrated the ability of ONT to phase single-nucleotide variants, enabling direct haplotype determination for genes TNNT2 and TPM1. These findings highlight the importance of long-range PCR efficiency, as well as lower accuracy of variant calling by ONT than by Illumina technology; these differences should be clarified prior to clinical application of the ONT method.

Isolated left ventricular apical hypoplasia with myocardial non-compaction: a case report.

BACKGROUND: Isolated left ventricular apical hypoplasia (ILVAH) is a rare congenital cardiac abnormality, which might result in severe symptomatic heart failure (HF) with pulmonary hypertension, atrial fibrillation (AF), or malignant ventricular tachycardia in adults. CASE SUMMARY: A 32-years-old man presented with exertional dyspnoea New York Heart Association Class II and persistent AF. Echocardiography and cardiac magnetic resonance showed the presence of (i) spherical remodelling of the left ventricle (LV) with impaired contractile function (three-dimensional ejection fraction, EF 32%); (ii) substitution of apical myocardium by fatty tissue; (iii) abnormal origin of a papillary muscle network; and (iv) an elongated right ventricle, compatible with ILVAH. In addition, non-compacted endomyocardial layer of the LV was observed. Because of a high risk of sudden cardiac death in symptomatic HF patients with reduced EF, an implantable cardioverter-defibrillator was placed which followed by pulmonary vein isolation. After the procedures and restoration of sinus rhythm, the patient demonstrated improvement in HF symptoms and exercise tolerance. This was accompanied by an enhancement of left and right ventricular systolic function by echocardiography. At 6-month, 1, and 2-year follow-up the clinical conditions of the patient and echocardiographic findings remained stable. DISCUSSION: A rare combination of ILVAH and left ventricular myocardium non-compaction was observed in this young adult who presented with symptomatic HF and persistent AF. The use of consecutive invasive cardiac procedures leads to restoration of sinus rhythm, the improvement of myocardial contractility and clinical manifestation of HF.