👤 Francesca Girolami

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

The 2 sarcomere genes most commonly associated with hypertrophic cardiomyopathy (HCM), MYBPC3 (myosin-binding protein C3) and MYH7 (β-myosin heavy chain), are indistinguishable at presentation, and genotype-phenotype correlations have been elusive. Based on molecular and pathophysiological differences, however, it is plausible to hypothesize a different behavior in myocardial performance, impacting lifetime changes in left ventricular (LV) function. We reviewed the initial and final echocardiograms of 402 consecutive HCM patients with pathogenic or likely pathogenic MYBPC3 (n=251) or MYH7 (n=151) mutations, followed over 9±8 years. At presentation, MYBPC3 patients were less frequently obstructive (15% versus 26%; MYBPC3-related HCM showed increased long-term prevalence of systolic dysfunction compared with MYH7, in spite of similar outcome. Such observations suggest different pathophysiology of clinical progression in the 2 subsets and may prove relevant for understanding of genotype-phenotype correlations in HCM. Show less

Background Although atrial fibrillation (AF) is common in hypertrophic cardiomyopathy (HCM) patients, the relationship between genetic variation and AF has been poorly defined. Characterizing genetic subtypes of HCM and their associations with AF may help to improve personalized medical care. We aimed to investigate the link between sarcomeric gene variation and incident AF in HCM patients. Methods and Results Patients from the multinational Sarcomeric Human Cardiomyopathy Registry were followed for incident AF. Those with likely pathogenic or pathogenic variants in sarcomeric genes were included. The AF incidence was ascertained by review of medical records and electrocardiograms at each investigative site. One thousand forty adult HCM patients, without baseline AF and with likely pathogenic or pathogenic variation in either MYH7 (n=296), MYBPC3 (n=659), or thin filament genes (n=85), were included. Compared with patients with variation in other sarcomeric genes, those with MYH7 variants were younger on first clinical encounter at the Sarcomeric Human Cardiomyopathy Registry site and more likely to be probands than the MYBPC3 variants. During an average follow-up of 7.2 years, 198 incident AF events occurred. Patients with likely pathogenic or pathogenic mutations in MYH7 had the highest incidence of AF after adjusting for age, sex, proband status, left atrial size, maximal wall thickness, and peak pressure gradient (hazard ratio, 1.7; 95% CI, 1.1-2.6; P=0.009). Conclusions During a mean follow-up of 7.2 years, new-onset AF developed in 19% of HCM patients with sarcomeric mutations. Compared with other sarcomeric genes, patients with likely pathogenic or pathogenic variation in MYH7 had a higher rate of incident AF independent of clinical and echocardiographic factors. Show less

Genes associated with hypertrophic cardiomyopathy (HC) are not uniformly expressed in the atrial myocardium. Whether this may impact susceptibility to atrial fibrillation (AF) is unresolved. To analyze the prevalence and clinical correlates of AF in relation to genotype in a large HC cohort, prevalence and clinical profile of AF were assessed in 237 patients with HC, followed for 14 ± 10 years. Patients were divided into 3 genetic subgroups: (1) MYBPC3 (58%), (2) MYH7 (28%), and (3) "other genotypes" (14%; comprising TNNT2, TNNI3, TPM1, MYL2, complex genotypes, Z-line, and E-C coupling genes). Left atrial size was similar in the 3 subsets. AF occurred in 74 patients with HC (31%), with no difference among groups (31% in MYBPC3, 37% in MYH7 and 18% in other genotypes, p = 0.15), paroxysmal/persistent AF (12%, 18%, and 12%, respectively; p = 0.53), paroxysmal/persistent evolved to permanent (12%, 12%, and 3%, p = 0.36) or permanent AF (7%, 7%, and 3%, p = 0.82). Age at AF onset was younger in the group with other genotypes (37 ± 10 years) compared to the first 2 groups (53 ± 14 and 51 ± 17, respectively; p = 0.05) because of early onset associated with complex genotypes and a specific JPH2 mutation associated with abnormal intracellular calcium handling. At multivariate analysis, independent predictors of AF were atrial diameter (p ≤0.05) and age at diagnosis (p = 0.09), but not genetic subtype (p = 0.35). In conclusion, in patients with HC, genetic testing cannot be used in clinical decision making with regard to management strategies for AF. Genotype is not predictive of onset or severity of AF, which appears rather driven by hemodynamic determinants of atrial dilatation. Exceptions are represented by rare genes suggesting specific molecular pathways for AF in genetic cardiomyopathies. Show less

We recently performed next generation sequencing (NGS) genetic screening in 11 consecutive and unrelated Tunisian HCM probands seen at Habib Thameur Hospital in Tunis in the first 6 months of 2014, as part of a cooperative study between our Institutions. The clinical diagnosis of HCM was made according to standard criteria. Using the Illumina platform, a panel of 12 genes was analyzed including myosin binding protein C (MYBPC3), beta-myosin heavy chain (MYH7), regulatory and essential light chains (MYL2 and MYL3), troponin-T (TNNT2), troponin-I (TNNI3), troponin-C (TNNC1), alpha-tropomyosin (TPM1), alpha-actin (ACTC1), alpha-actinin-2 (ACTN2) as well as alfa-galactosidase (GLA), 5'-AMP-activated protein (PKRAG2), transthyretin (TTR) and lysosomal-associated membrane protein-2 (LAMP2) for exclusion of phenocopies. Our preliminary data, despite limitations inherent to the small sample size, suggest that HCM in Tunisia may have a peculiar genetic background which privileges rare genes overs the classic HCM-associated MHY7 and MYBPC3 genes. Show less

End-stage hypertrophic cardiomyopathy (ES-HC) has an ominous prognosis. Whether genotype can influence ES-HC occurrence is unresolved. We assessed the spectrum and clinical correlates of HC-associated mutations in a large multicenter cohort with end-stage ES-HC. Sequencing analysis of 8 sarcomere genes (MYH7, MYBPC3, TNNI3, TNNT2, TPM1, MYL2, MYL3, and ACTC1) and 2 metabolic genes (PRKAG2 and LAMP2) was performed in 156 ES-HC patients with left ventricular (LV) ejection fraction (EF) <50%. A comparison among mutated and negative ES-HC patients and a reference cohort of 181 HC patients with preserved LVEF was performed. Overall, 131 mutations (36 novel) were identified in 104 ES-HC patients (67%) predominantly affecting MYH7 and MYBPC3 (80%). Complex genotypes with double or triple mutations were present in 13% compared with 5% of the reference cohort (p = 0.013). The distribution of mutations was otherwise indistinguishable in the 2 groups. Among ES-HC patients, those presenting at first evaluation before the age of 20 had a 30% prevalence of complex genotypes compared with 19% and 21% in the subgroups aged 20 to 59 and ≥60 years (p = 0.003). MYBPC3 mutation carriers with ES-HC were older than patients with MYH7, other single mutations, or multiple mutations (median 41 vs 16, 26, and 28 years, p ≤0.001). Outcome of ES-HC patients was severe irrespective of genotype. In conclusion, the ES phase of HC is associated with a variable genetic substrate, not distinguishable from that of patients with HC and preserved EF, except for a higher frequency of complex genotypes with double or triple mutations of sarcomere genes. Show less

The aim of this study was to describe the clinical profile associated with triple sarcomere gene mutations in a large hypertrophic cardiomyopathy (HCM) cohort. In patients with HCM, double or compound sarcomere gene mutation heterozygosity might be associated with earlier disease onset and more severe outcome. The occurrence of triple mutations has not been reported. A total of 488 unrelated index HCM patients underwent screening for myofilament gene mutations by direct deoxyribonucleic acid sequencing of 8 genes, including myosin binding protein C (MYBPC3), beta-myosin heavy chain (MYH7), regulatory and essential light chains (MYL2, MYL3), troponin-T (TNNT2), troponin-I (TNNI3), alpha-tropomyosin (TPM1), and actin (ACTC). Of the 488 index patients, 4 (0.8%) harbored triple mutations, as follows: MYH7-R869H, MYBPC3-E258K, and TNNI3-A86fs in a 32-year-old woman; MYH7-R723C, MYH7-E1455X, and MYBPC3-E165D in a 46-year old man; MYH7-R869H, MYBPC3-K1065fs, and MYBPC3-P371R in a 45-year old woman; and MYH7-R1079Q, MYBPC3-Q969X, and MYBPC3-R668H in a 50-year old woman. One had a history of resuscitated cardiac arrest, and 3 had significant risk factors for sudden cardiac death, prompting the insertion of an implantable cardioverter-defibrillator in all, with appropriate shocks in 2 patients. Moreover, 3 of 4 patients had a severe phenotype with progression to end-stage HCM by the fourth decade, requiring cardiac transplantation (n=1) or biventricular pacing (n=2). The fourth patient, however, had clinically mild disease. Hypertrophic cardiomyopathy caused by triple sarcomere gene mutations was rare but conferred a remarkably increased risk of end-stage progression and ventricular arrhythmias, supporting an association between multiple sarcomere defects and adverse outcome. Comprehensive genetic testing might provide important insights to risk stratification and potentially indicate the need for differential surveillance strategies based on genotype. Show less

In patients with hypertrophic cardiomyopathy (HCM) and atrial fibrillation (AF), radiofrequency catheter ablation (RFCA) represents a promising option. However, the predictors of RFCA efficacy remain largely unknown. We assessed the outcome of a multicentre HCM cohort following RFCA for symptomatic AF refractory to medical therapy. Sixty-one patients (age 54 +/- 13 years; time from AF onset 5.7 +/- 5.5 years) with paroxysmal (n = 35; 57%), recent persistent (n = 15; 25%), or long-standing persistent AF (n = 11; 18%) were enrolled. A scheme with pulmonary vein isolation plus linear lesions was employed. Of the 61 patients, 32 (52%) required redo procedures. Antiarrhythmic therapy was maintained in 22 (54%). At the end of a 29 +/- 16 months follow-up, 41 patients (67%) were in sinus rhythm, including 17 of the 19 patients aged < or = 50 years, with marked improvement in New York Heart Association (NYHA) functional class (1.2 +/- 0.5 vs. 1.9 +/- 0.7 at baseline; P < 0.001). In the remaining 20 patients (33%), with AF recurrence, there was less marked, but still significant, improvement following RFCA (NYHA class 1.8 +/- 0.7 vs. 2.3 +/- 0.7 at baseline; P = 0.002). Independent predictors of AF recurrence were increased left atrium volume [hazard ratio (HR) per unit increase 1.009, 95% confidence interval (CI) 1.001-1.018; P = 0.037] and NYHA functional class (HR 2.24, 95% CI 1.16-4.35; P = 0.016). Among 11 genotyped HCM patients (6 with MYBPC3, 2 with MYH7, 1 with MYL2 and 2 with multiple mutations), RFCA success rate was comparable with that of the overall cohort (n = 8; 73%). RFCA was successful in restoring long-term sinus rhythm and improving symptomatic status in most HCM patients with refractory AF, including the subset with proven sarcomere gene mutations, although redo procedures were often necessary. Younger HCM patients with small atrial size and mild symptoms proved to be the best RFCA candidates, likely due to lesser degrees of atrial remodelling. Show less

Mutations causing hypertrophic cardiomyopathy (HCM) have been described in nine different genes of the sarcomere. Three genes account for most known mutations: beta-myosin heavy chain (MYH7), cardiac myosin binding protein C (MYBPC3) and cardiac troponin T (TNNT2). Their prevalence in Italian HCM patients is unknown. Thus, we prospectively assessed a molecular screening strategy of these three genes in a consecutive population with HCM from two Italian centres. Comprehensive screening of MYBPC3, MYH7 and TNNT2 was performed in 88 unrelated HCM patients by denaturing high-performance liquid chromatography and automatic sequencing. We identified 32 mutations in 50 patients (57%); 16 were novel. The prevalence rates for MYBPC3, MYH7 and TNNT2 were 32%, 17% and 2%, respectively. MYBPC3 mutations were 18, including two frameshift, five splice-site and two nonsense. All were 'private' except insC1065 and R502Q, present in three and two patients, respectively. Moreover, E258K was found in 14% of patients, suggesting a founder effect. MYH7 mutations were 12, all missense; seven were novel. In TNNT2, only two mutations were found. In addition, five patients had a complex genotype [i.e. carried a double MYBPC3 mutation (n = 2), or were double heterozygous for mutations in MYBPC3 and MYH7 (n = 3)]. The first comprehensive evaluation of MYBPC3, MYH7 and TNNT2 in an Italian HCM population allowed a genetic diagnosis in 57% of the patients. These data support a combined analysis of the three major sarcomeric genes as a rational and cost-effective initial approach to the molecular screening of HCM. Show less