Genetic variants as determinants of outcome in lamin A/C-related cardiac disease

Background

Current guidelines for the diagnosis and management of familial dilated cardiomyopathy highlight the variables “male sex” and “non-missense type variants” as risk factors for malignant ventricular arrhythmias.

Objective

Quantitative evaluation of prognostic differences between different LMNA variants associated with cardio-laminopathy.

Method

Analysis of cardiac event-free survival (sudden death, major arrhythmic events, death from heart failure and transplantation) with Kaplan-Meier approach in relation to gender & variant LMNA type. The data come from a specific database containing information on more than 1200 carriers of disease-causing LMNA variants. In the first analysis, the groups of comparison were truncating-type variants (LMNAtv) VS the global of pathogenic missense variants in the gene associated with cardiolaminopathy (LMNAm), segregated by gender. In the second analysis, it was considered missense LMNA affecting different residues (p.Arg190, p.Arg377 and p.Arg541), located in different functional domains, with enough data for comparison and with statistically different clinical behavior from that of global pathogenic variants in the gene. They were compared with the group of LMNAtv variants, as reference. The variants included were p.Arg377Cys/His, p.Arg541Cys/Ser/Gly/Pro/His and p.Arg190Trp/Gln/Pro, all of them pathogenic and associated with cardio-laminopathy.

Results

No significant differences were observed in survival between LMNAtv versus LMNAm variants (log rank=0.56) with slightly worse outcomes in males (log rank 0.03). Median survival time was 56 years for men compared to 60 years for women with LMNAtv, and 55 years compared to 66 years, respectively, among carriers of LMNAm (analysis A). In analysis B, statistically significant differences were observed between the groups considered (Log Rank p<0.001). These differences were also clinically relevant (median survival time in groups p.Arg377, LMNAtv, p.Arg190 and p.Arg541 was 60, 58, 50 and 35 years, respectively). Importantly, more than 70% of the cardiac events observed were related to major ventricular arrhythmic episodes.

Conclusions

This quantitative analysis demonstrates that certain missense variants in LMNA may have a similar and even more adverse clinical course than the set of truncation-type variants. These findings highlight the relevance of the specific variant rather than the variant type in guiding actionable therapies to prevent adverse outcomes. Regarding the differences observed between genders, even though they are statistically significant, their magnitude could be clinically not relevant.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Health in Code

Specific actin (ACTC1) missense variants are associated with different overlapping clinical phenotypes and outcomes

Introduction

Pathogenic variants in ACTC1 have been associated with hypertrophic (HCM), dilated (DCM), and left ventricular non-compaction (LVNC) cardiomyopathies. Phenotypes often overlap and atrial septal defects have also been reported. Prognostic data on carriers of these variants are scarce.

Methods and results

The proprietary database of a cardiovascular genetic laboratory was examined to assess penetrance and survival in the 438 carriers (191 families) of 75 missense variants in ACTC1 associated with disease. Their mean age at diagnosis was 32.4 (±18.7) years; 52% were male. The diagnosis was isolated HCM in 47%, LVNC in 17%, and DCM in 9%. LVNC with either HCM or DCM was present in an additional 8%; 13% had an atrial septal defect. Among carriers with echocardiographic information, left ventricular dilatation and dysfunction were described in 13% and 16%, respectively. Ventricular arrhythmias and conduction defects were reported in 94 and 93 carriers. Percentages have not been calculated for the latter, as we cannot ensure a denominator in whom cardiac conduction defects and arrhythmias were certainly discarded.

Overall, 50% of carriers were diagnosed by age 45, and 10% had experienced a major cardiac event. The p.Leu10Met and p.His90Tyr variants (23% of all carriers) demonstrated lower penetrance and a better prognosis than the p.Glu101Lys variant and the other missense variants.

Conclusions

Missense variants in ACTC1 are associated with a range of phenotypes that often overlap. Overall, penetrance and outcomes are age-dependent with a moderate rate of major cardiac events, which are highly dependent on the specific disease-causing variant

Funding Acknowledgement

Type of funding sources: None. Figure 1. The graph shows the percentage of carriers of pathogenic or likely pathogenic missense variants in the ACTC1 gene diagnosed at different ages. Considering all the missense variants in ACTC (in red), 50% of carriers had been diagnosed by age 45. It is worth highlighting the percentage of diagnosis (>15%) in the first 15 years of life, which is higher than the figure usually observed in sarcomeric hypertrophic cardiomyopathy.Figure 2. The graph shows the survival free of major cardiovascular events (sudden, heart failure, stroke-related death, appropriate ICD therapy and heart transplant) in individuals with missense variants in ACTC1. Carriers and affected relatives without genetic study were included. Events were infrequent in two of the most informative variants (p.Leu10Met and p.His90Tyr), and significantly different compared with carriers of the other missense variants (p=0.036 for p.Leu10Met and p=0.015 for p.His90Tyr).

Narrowing of the neonatal region in the FBN1 gene

Background

Neonatal Marfan syndrome (MFS) is considered the most severe form of MFS and is characterized by early childhood death due to congestive heart failure. It has been suggested that genetic variants associated with this clinical presentation, cluster in a specific region between exons 24 and 32. It has been reported that patients carrying genetic variants in these exons have worse prognosis.

Purpose

Our purpose was to analyze cardiovascular outcome by location of the genetic variants in the “neonatal region” of the FBN1 gene.

Materials and methods

We analyzed clinical data on 1353 carriers and affected relatives with 683 missense pathogenic or likely pathogenic genetic variants of FBN1 gene (including cases identified in our laboratory and cases described in the literature) in whom age at last follow-up was available. Kaplan-Meier survival curves were generated to examine location of the genetic variant in the FBN1 gene in relation to survival free of surgical intervention or cardiovascular (CV) death (composite of deaths related to aortic dissection, heart failure/transplant, sudden, stroke or CV surgery).

Missense genetic variants were classified as located in the “neonatal region” (residues 952–1363, corresponding to exons 24–32) and in the “non-neonatal region” (residues 45–951 and 1364–2731). In the “neonatal region”, we have also analyzed a sub-region of “over-representation” of heart failure deaths in the first year of life, which we called “critical neonatal region” (amino acids 1028–1088, corresponding to exon 25 and few residues from exon 26) in comparison to the “non-critical neonatal region”.

Results

Data were examined on 1060 patients with missense variants located in the “non neonatal region” and on 293 patients with missense variants located in the “neonatal region”. Of these, 96 patients were carriers of missense variants in the “critical neonatal region”, the rest of patients carried variants in the neonatal region, outside this particular domain (“non-critical neonatal region”).

Patients carrying missense variants in the neonatal region had worse prognosis than those carrying variants outside this region. This poorer outcome was due to events occurring in patients carrying variants in the “critical neonatal region” (see Figure). These patients had the worse prognosis (p=0.000108, vs. the other groups). Furthermore, events in the non-critical neonatal region were similar to other missense variants located outside the neonatal region.

There were no differences in the “neonatal region” when analyzing by gender.

Conclusion

In our cohort, the worse prognosis seen in patients carrying missense pathogenic or likely pathogenic variants in the “neonatal region” compared to the “non-neonatal region”, was due to events in patients carrying missense variants in a small subregion which we called the “critical-neonatal region” (exons 25 and 26). These patients had the worse prognosis, irrespective of gender.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Health in Code Figure 1. Neonatal region FBN1

Molecular characterization of a cohort of individuals referred to genetic testing with suspected CPVT

Background

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is one of the most lethal inherited arrhythmogenic diseases and it mainly affects the young, in the absence of structural heart disease. This condition is difficult to diagnose and the first expression of disease can be an arrhythmic death. In the last years, genetic testing has become a useful tool in the challenging task of CPVT diagnosis.

The diagnostic yield of the genetic study is highly variable and dependent on the phenotypic characteristics of the individuals evaluated.

Purpose

This study aimed to address the clinical characteristics and genetic testing (GT) results in a cohort of individuals referred to genetic analysis with a non-definitive diagnosis of CPVT, in a real world-setting.

Methods

This is a retrospective cohort study of patients referred for GT with clinical suspicion of CPVT, but who did not strictly meet the diagnostic criteria for this disease (according to current guidelines). NGS genotyping was performed with a library of 251 genes. NGS-based genomic testing was performed with classification of identified variants according to American College of Medical Genetics and Genomics guidelines.

Results

One hundred and sixteen unrelated patients with available clinical information (patients' characteristics are summarized in TABLE1) were included in the analysis. Mean age at GT was 36 y/o (±19), 47% were women and 18% had a familial history of sudden cardiac death.

The first clinical manifestation was: exercise or stress induced syncope in 36%, exercise induced ventricular tachycardia in 30% and sudden cardiac arrest in 15.5% (78% during emotional or physical stress - 89% aborted sudden death). Mean age at sudden death was 20 y/o (±14).

GT was positive in 49.1% (n=57), negative in 37.9% (n=44) and inconclusive in 12.9% (n=15). We had identified pathogenic/likely pathogenic variants in CPVT-related genes in 40% of the referred patients: RYR2 (70.2%-n: 40), KCNJ2 (8.8%-n: 5), CASQ2 in homozygous/compound heterozygous carriers (3.5%-n: 2). In the RYR2 gene we detected 36 different genetic variants (13 were novel) in 40 different individuals. In addition, relevant variants were also identified in other genes associated with channelopathies (SCN5A, 3.5%, n: 2 and KCNQ1, 1.7%, n: 1) and in genes associated with structural heart disease: desmosomal genes (6.8%-DSP n: 1 and PKP2 n: 3) and sarcomeric genes (5.1%- MYBPC3 and MYH7) (figure 1A-B).

Conclusions

In our cohort of patients with non-definitive diagnosis of CPVT, the diagnostic yield of genetic testing was almost 50%. GT allowed confirmation of the suspicion of CPVT in 40% of the patients and, in addition, we were able to detect relevant genetic variants in other genes not associated with CPVT in 10% (differential diagnosis). The use of wide genetic panels would be useful in this context.

Funding Acknowledgement

Type of funding sources: None. Suspected CPVT. Genetic Testing.

Marfan syndrome: genetic variant determinants of cardiovascular outcomes

Background

Marfan syndrome is a systemic connective tissue disorder caused by genetic variants in the fibrillin-1 (FBN1) gene. Cardiovascular complications are the leading cause of mortality.

Purpose

To compare cardiovascular outcome by gender and by type of the genetic variant in the FBN1 gene.

Materials and methods

We analyzed clinical data on 1956 carriers and affected relatives with 1430 pathogenic or likely pathogenic genetic variants in the FBN1 gene (including cases identified in our laboratory and cases described in the literature) in whom age at last follow-up was available. We excluded patients with pathogenic or likely pathogenic genetic variants located in the so-called “neonatal region” (exon 24–32); they are recognized to have an early onset/severe phenotype.

Kaplan-Meier survival curves were generated to examine gender and type of genetic variant in relation to survival free of surgical intervention or cardiovascular (CV) death (composite of deaths related to aortic dissection, heart failure/transplant, sudden, stroke or CV surgery). Genetic variants were classified as truncating (nonsense, frameshift and splicing), “missense non-neonatal” and only those missense eliminating a Cysteine residue in the non-neonatal region (“Cys non-neonatal”).

Results

Data were examined on 896 patients with truncating variants (53% male; 47% female) and 1060 with missense variants, located outside the “neonatal region” (54% male; 46% female). Of these, 475 were missense variants substituting a cysteine residue (52% male; 48% female).

Those with truncating variants had worse prognosis versus those with missense and Cys variants (p=0.000108 and p=0.000115), with earlier onset of cardiovascular events. Overall, patients with missense variants had similar prognosis to those with missense variants eliminating a Cysteine residue. By age 65, however, almost 50% of patients with any type of variant had suffered a CV event, and with each variant type males had worse prognosis (see Figure 1). This was most evident in males aged 30 to 50 with missense variants that substituted a Cysteine residue, while female carriers of these variants had a prognosis similar to other missense variants (see Figure 2).

During the first decade carriers of missense and truncating variants mainly died of heart failure. From age 10 to 50, aortic dissection was the most common event, while later other events became more frequent, e.g. vascular intervention and sudden death.

Conclusion

In our cohort, male carriers of pathogenic or likely pathogenic variants had worse prognosis versus females. Carriers of truncating variants had the worst CV outcomes. However, it is noteworthy that by age 65, regardless of gender or mutation type, close to 50% of patients had experienced a major CV event/death.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Health in Code Figure 2. Type by gender

Novel Filamin C missense mutation associated with severe restrictive cardiomyopathy overlapping with left ventricular non-compaction

Introduction

Filamin C gene (FLNC) missense mutations have been previously reported in association with restrictive cardiomyopathy (RCM). The association of FLNC missense variants with non-compaction cardiomyopathy has been reported only in a single proband, but familiar or functional evidence on its causative effect is limited. Overlapping traits among cardiomyopathies related to the same genetic substrate is an emerging and a challenging scenario nowadays.

Purpose

To report a new pathogenic FLNC missense variant in association with a particular form of restrictive/non-compaction overlapping cardiomyopathy.

Methods

The probands fulfill the diagnostic criteria for RCM based on current guidelines. Genetic testing in the probands was performed by NGS, using a broad gene panel (containing over 240 genes). Clinical and genetic cascade screening were expanded to first-degree relatives when it was possible. All mutation carriers underwent clinical assessment including physical examination, 12-lead ECG, echocardiography, cardiac magnetic resonance (MRI), 24h Holter monitoring, and ergometry. None of them had major systemic illnesses nor clinical symptoms of muscular involvement.

Results

The p.Gly2011Arg variant in the FLNC gene was the only relevant variant in the three probands. This variant is virtually absent in the general population (gnomAD). The variant showed a de novo presentation in the first family and segregated with the phenotype in the four studied relatives from the second family (three affected carriers and one unaffected non-carrier). In the third case no familial information was available. This variant affects an ultraconserved residue and is located in a relevant sub-region of Filamin-C, which is necessary for its interaction with other Z-disc proteins. Detailed clinical information is available on all carriers (n=5, 1 male). The average age at diagnosis is 17 years [1–36]. An abnormal ECG was the earliest clinical manifestation (left ventricular hypertrophy by voltage criteria and extensive repolarization abnormalities). Significant hypertrabeculations, mainly at the anterolateral wall and basal anteroseptal segments, was present in all affected carriers. Interestingly, none of them showed an abnormal late-gadolinium enhancement pattern on MRI. The four carriers who were older than 35 years were found to have severe restrictive pattern on echocardiography (functional parameters and secondary features such as bi-atrial dilation), all four suffered from limiting dyspnea, and two are under pre-transplant workup (A-II-1 and B-III-1). One of them had a cardioembolic event (femoral acute ischemia, A-II-1). One relative has recently died from advanced heart failure (B-II-2).

Conclusion

This is the first description on this overlapping (restrictive/non-compaction cardiomyopathy) and aggressive phenotype associated with a missense FLNC variant. This description widens the clinical spectrum related to FLNC missense mutations.

Pedigrees and clinical characterization

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Health in Code

Prognostic implications of pathogenic truncating variants in the TTN gene

INTRODUCTION AND OBJECTIVES

TTN gene truncating variants (TTNtv) are a frequent cause of dilated cardiomyopathy (DCM). However, there are discrepant data on the associated prognosis. Our objectives were to describe the prevalence of TTNtv in our cohort and to compare the clinical course with that described in the literature.

METHODS

We included patients with DCM and genetic testing performed using next-generation sequencing. Through a systematic literature research, we collected information about carriers and affected relatives with TTNtv. We compared the cumulative percentage of affected carriers and the survival free of cardiovascular death.

RESULTS

One hundred and ten DCM patients were evaluated. A total of 13 TTNtv distributed in 14 probands were identified (12.7%). We found a 21.4% prevalence in familial cases. No significant differences in the relation between age and clinical disease expression were identified. Survival free of cardiovascular death curves constructed from data in the literature seems not to overestimate the risk in our population.

CONCLUSIONS

The identification of TTNtv in patients with DCM is frequent and provides relevant information about the disease prognosis. The risk of cardiovascular death should not be underestimated. Age related penetrance need to be considered in the familial evaluation.

Clinical utility of genetic testing in patients with dilated cardiomyopathy

INTRODUCTION AND OBJECTIVES

Dilated cardiomyopathy (DCM) is the most frequent cause of heart transplantation. The prevalence of familial disease can reach 50%. Our objective was to describe the genetic basis of DCM in a cohort with a high proportion of transplanted patients.

METHODS

We included patients with DCM and genetic testing performed using next-generation sequencing (NGS) that included at least 80 genes. Clinical data, family history and genetic results were retrospectively analysed. When possible, assessment of first-degree relatives was carried out.

RESULTS

Eighty-seven DCM patients and 308 relatives from 70 families were evaluated. Clinical prevalence of familial disease was 37% (32 patients). Forty-four percent of patients (38 patients) had required heart transplantation. A relevant variant was found in 43 patients (49%), 25 patients (29%) carried variants of unknown significance and in 19 patients (22%) the study was negative. Most genetic variants were found in sarcomeric genes and the yield of genetic testing was higher in patients with familial DCM.

CONCLUSIONS

The yield of genetic testing in our DCM cohort was high, reaching 69% in familial cases. Mutational spectrum was heterogeneous and the identification of the specific aetiology of the disease often provided prognostic information.

Mutations in TRIM63 cause an autosomal-recessive form of hypertrophic cardiomyopathy

OBJECTIVE

Up to 50% of patients with hypertrophic cardiomyopathy (HCM) show no disease-causing variants in genetic studies. TRIM63 has been suggested as a candidate gene for the development of cardiomyopathies, although evidence for a causative role in HCM is limited. We sought to investigate the relationship between rare variants in TRIM63 and the development of HCM.

METHODS

TRIM63 was sequenced by next generation sequencing in 4867 index cases with a clinical diagnosis of HCM and in 3628 probands with other cardiomyopathies. Additionally, 3136 index cases with familial cardiovascular diseases other than cardiomyopathy (mainly channelopathies and aortic diseases) were used as controls.

RESULTS

Sixteen index cases with rare homozygous or compound heterozygous variants in TRIM63 (15 HCM and one restrictive cardiomyopathy) were included. No homozygous or compound heterozygous were identified in the control population. Familial evaluation showed that only homozygous and compound heterozygous had signs of disease, whereas all heterozygous family members were healthy. The mean age at diagnosis was 35 years (range 15-69). Fifty per cent of patients had concentric left ventricular hypertrophy (LVH) and 45% were asymptomatic at the moment of the first examination. Significant degrees of late gadolinium enhancement were detected in 80% of affected individuals, and 20% of patients had left ventricular (LV) systolic dysfunction. Fifty per cent had non-sustained ventricular tachycardia. Twenty per cent of patients suffered an adverse cerebrovascular event (20%).

CONCLUSION

TRIM63 appears to be an uncommon cause of HCM inherited in an autosomal-recessive manner and associated with concentric LVH and a high rate of LV dysfunction.