👤 Erika Pagannone

MYBPC3 pathogenic variants are the most common cause of hypertrophic cardiomyopathy (HCM) and are associated with significant phenotypic heterogeneity. Despite their pathogenic potential, MYBPC3 founder variants persist within specific populations. This study investigates the MYBPC3 c.2309-2 A > G splice variant hypothesizing its founder origin in central Italy. The aim was to confirm the presence of a common haplotype, assess its molecular and clinical impact, and compare the phenotype with that of other MYBPC3 founder variants. Among the 5251 HCM patients recruited at eight Italian referral centers, 1108 probands (21.1%) were identified as carriers of pathogenic or likely pathogenic MYBPC3 variants, and among these, 11.6% carried the c.2309-2 A > G variant. Haplotype reconstruction using short tandem repeats and tag-SNPs revealed a unique 5.2 Mb haplotype segregating with the c.2309-2 A > G variant in all carriers. Age estimation suggested that the variant originated approximately 481 years ago, likely in the Lazio region with clustering in Rome. Clinically, carriers exhibited variable expressivity with age-and sex-dependent penetrance. Males showed earlier onset, higher penetrance and greater disease severity compared to females. RNA analysis showed the retention of both introns 23 and 24, and significantly reduced MYBPC3 expression consistent with haploinsufficiency. Comparative analysis with other MYBPC3 founder variants highlighted differences in phenotypic expression, particularly in left ventricular wall thickness and clinical outcomes. This study establishes c.2309-2 A > G as an Italian MYBPC3 founder mutation, enhancing the understanding of HCM genetics and regional founder effects. These findings emphasize the importance of targeted genetic screening and personalized management for MYBPC3 c.2309-2 A > G carriers. Show less

Hypertrophic cardiomyopathy (HCM) is a genetic cardiac muscle disease characterized by clinical and genetic heterogeneity. Genetic testing can reveal the presence of disease-causing variants in genes encoding sarcomere proteins. However, it yields inconclusive or negative results in 40-60% of HCM cases, owing to, among other causes, technical limitations such as the inability to detect pathogenic intronic variants. Therefore, we aimed to increase the diagnostic yield of molecular analysis for HCM by improving the Show less

Sequencing of sarcomere protein genes in patients fulfilling the clinical diagnostic criteria for hypertrophic cardiomyopathy (HCM) identifies a disease-causing mutation in 35% to 60% of cases. Age at diagnosis and family history may increase the yield of mutations screening. In order to assess whether Next-Generation Sequencing (NGS) may fulfil the molecular diagnostic needs in HCM, we included 17 HCM-related genes in a sequencing panel run on PGM IonTorrent. We selected 70 HCM patients, 35 with early (≤25 years) and 35 with late (≥65 years) diagnosis of disease onset. All samples had a 98.6% average of target regions, with coverage higher than 20× (mean coverage 620×). We identified 41 different mutations (seven of them novel) in nine genes: MYBPC3 (17/41 = 41%); MYH7 (10/41 = 24%); TNNT2, CAV3 and MYH6 (3/41 = 7.5% each); TNNI3 (2/41 = 5%); GLA, MYL2, and MYL3 (1/41=2.5% each). Mutation detection rate was 30/35 (85.7%) in early-onset and 8/35 (22.9%) in late-onset HCM patients, respectively (p < 0.0001). The overall detection rate for patients with positive family history was 84%, and 90.5% in patients with early disease onset. In our study NGS revealed higher mutations yield in patients with early onset and with a family history of HCM. Appropriate patient selection can increase the yield of genetic testing and make diagnostic testing cost-effective. Show less

Hypertrophic cardiomyopathy (HCM) is a genetic disorder characterized by cardiac hypertrophy caused by mutations in sarcomere protein genes. MYBPC3 mutations are reported as a frequent cause of HCM. We aimed to identify the gene mutation underlying HCM in an Italian patient and his family composed of 13 relatives. Mutation screening of 658 known mutations was performed using a rapid and efficient mutation detection system based on semiautomated MALDI-TOF mass spectrometry using the Sequenom MassArray System and iPLEX Gold genotyping chemistry. Subsequently, direct sequencing of the coding exons and flanking intronic regions was performed for the most suitable HCM genes (MYBPC3, MYH7, TNNT2, TNNI3, and TPM1) in the index patient. We found a novel MYBPC3 gene mutation: G13999T (Gln689His). No other sarcomere gene mutation was found in this family. This genetic variant, which changes the last amino acid of MYBPC3 exon 21, affects a highly conserved residue. Furthermore, the Gln689His does not appear in public databases and has never been described as a polymorphism. The potential pathogenic role of this novel mutation was underlined by its absence in a sample of healthy subjects (n = 122) from the general Italian population. In summary, a novel MYBPC3 gene mutation has been identified in a patient affected by HCM, whereas it was absent in 244 reference alleles. Show less