Cardiac myosin binding protein-C variants in paediatric-onset hypertrophic cardiomyopathy: natural history and clinical outcomes

BACKGROUND

Variants in the cardiac myosin-binding protein C gene (MYBPC3) are a common cause of hypertrophic cardiomyopathy (HCM) in adults and have been associated with late-onset disease, but there are limited data on their role in paediatric-onset HCM. The objective of this study was to describe natural history and clinical outcomes in a large cohort of children with HCM and pathogenic/likely pathogenic (P/LP) MYBPC3 variants.

METHODS AND RESULTS

Longitudinal data from 62 consecutive patients diagnosed with HCM under 18 years of age and carrying at least one P/LP MYBPC3 variant were collected from a single specialist referral centre. The primary patient outcome was a major adverse cardiac event (MACE). Median age at diagnosis was 10 (IQR: 2-14) years, with 12 patients (19.4%) diagnosed in infancy. Forty-seven (75%) were boy and 31 (50%) were probands. Median length of follow-up was 3.1 (IQR: 1.6-6.9) years. Nine patients (14.5%) experienced an MACE during follow-up and five (8%) died. Twenty patients (32.3%) had evidence of ventricular arrhythmia, including 6 patients (9.7%) presenting with out-of-hospital cardiac arrest. Five-year freedom from MACE for those with a single or two MYBPC3 variants was 95.2% (95% CI: 78.6% to 98.5%) and 68.4% (95% CI: 40.6% to 88.9%), respectively (HR 4.65, 95% CI: 1.16 to 18.66, p=0.03).

CONCLUSIONS

MYBPC3 variants can cause childhood-onset disease, which is frequently associated with life-threatening ventricular arrhythmia. Clinical outcomes in this cohort vary substantially from aetiologically and genetically mixed paediatric HCM cohorts described previously, highlighting the importance of identifying specific genetic subtypes for clinical management of childhood HCM.

Clinical characterisation of hypertrophic cardiomyopathy caused by MYH7 gene variants in children

Background

Variants in the cardiac Beta Myosin Heavy chain 7 gene (MYH7) are a common cause of hypertrophic cardiomyopathy (HCM) in adults, but their role in paediatric-onset HCM has not been systematically characterised. This study aims to describe the presentation, clinical characteristics and outcomes of childhood HCM secondary to disease-causing MYH7 variants.

Methods

Retrospective, longitudinal, data from 70 individuals meeting diagnostic criteria for HCM under the age of 18 years with disease-causing MYH7 variants from a single specialist centre (1991–2019) were collected. A Major Adverse Cardiac Event was defined as sudden cardiac death (SCD), heart failure-related death, cardiac transplantation, haemodynamically-compromising sustained ventricular arrhythmia or appropriate implantable cardioverter defibrillator (ICD) therapy.

Results

Median age at diagnosis was 9.2 years (IQR 4.2–13.3 years); 47 patients (67.1%) were less than 12 years and 7 (10.0%) were under the age of 1 at diagnosis. Twenty-two patients (31.4%) were probands. MYH7 variants were missense (n=67) or truncating (n=1). Reason for presentation were: family screening (n=45, 64.3%); cardiac symptoms (n=12, 17.1%); incidental finding (n=11, 15.7%); and out of hospital cardiac arrest (n=2, 2.9%). At baseline, mean maximum left ventricular wall thickness (MLVWT) z-score was 9.6 (±5.8), 11 patients (15.7%) had resting left ventricular outflow tract obstruction (left ventricular outflow tract gradient ≥30mmHg). Baseline phenotype did not significantly differ between probands and non-probands (MLVWT Z score 11.9 (±4.5) vs 8.5 (±6.1), p-value 0.0675). Over a median follow up of 3.6 years (IQR 1.8–7.9 years), 10 patients (14.3%) underwent a left ventricular septal myectomy at a median age 6.4 years (IQR 3.4–12.1 years) and 27 (38.6%) had an implantable cardioverter defibrillator (ICD) for primary (n=24, 34.3%) or secondary (n=3, 4.3%) prevention. Three patients (4.3%) died (SCD, n=1; heart-failure related, n=1; non-cardiac, n=1) and 3 (4.3%) underwent cardiac transplantation. Ten patients (14.3%) experienced a MACE. Patients who experienced a MACE were more likely to be probands [n= 6 (60.0%) vs n=16 (26.7%); p=0.036] but did not differ in terms of baseline phenotype (p=0.134).

Conclusion

MYH7 variants can cause infantile and childhood-onset disease, which is associated with significant early cardiac morbidity and mortality. Adverse outcomes were more common in those presenting as probands.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Medical Research Council, Great Ormond Street Hospital charity.

Analysis of Anti-RNA Polymerase III Antibody-positive Systemic Sclerosis and Altered GPATCH2L and CTNND2 Expression in Scleroderma Renal Crisis

OBJECTIVE

Scleroderma renal crisis (SRC) is a life-threatening complication of systemic sclerosis (SSc) strongly associated with anti-RNA polymerase III antibody (ARA) autoantibodies. We investigated genetic susceptibility and altered protein expression in renal biopsy specimens in ARA-positive patients with SRC.

METHODS

ARA-positive patients (n = 99) with at least 5 years' follow-up (49% with a history of SRC) were selected from a well characterized SSc cohort (n = 2254). Cases were genotyped using the Illumina Human Omni-express chip. Based on initial regression analysis, 9 single-nucleotide polymorphisms (SNP) were chosen for validation in a separate cohort of 256 ARA-positive patients (40 with SRC). Immunostaining of tissue sections from SRC or control kidney was used to quantify expression of candidate proteins based upon genetic analysis of the discovery cohort.

RESULTS

Analysis of 641,489 SNP suggested association of POU2F1 (rs2093658; P = 1.98 × 10^-5), CTNND2 (rs1859082; P = 5.58 × 10^-5), HECW2 (rs16849716; P = 1.2 × 10^-4), and GPATCH2L (rs935332; P = 4.92 × 10^-5) with SRC. Further, the validation cohort showed an association between rs935332 within the GPATCH2L region, with SRC (P = 0.025). Immunostaining of renal biopsy sections showed increased tubular expression of GPATCH2L (P = 0.026) and glomerular expression of CTNND2 (P = 0.026) in SRC samples (n = 8) compared with normal human kidney controls (n = 8), despite absence of any genetic replication for the associated SNP.

CONCLUSION

Increased expression of 2 candidate proteins, GPATCH2L and CTNND2, in SRC compared with control kidney suggests a potential role in pathogenesis of SRC. For GPATCH2L, this may reflect genetic susceptibility in ARA-positive patients with SSc based upon 2 independent cohorts.

Expanding the horizons of microRNA bioinformatics

MicroRNA regulation of key biological and developmental pathways is a rapidly expanding area of research, accompanied by vast amounts of experimental data. This data, however, is not widely available in bioinformatic resources, making it difficult for researchers to find and analyze microRNA-related experimental data and define further research projects. We are addressing this problem by providing two new bioinformatics data sets that contain experimentally verified functional information for mammalian microRNAs involved in cardiovascular-relevant, and other, processes. To date, our resource provides over 4400 Gene Ontology annotations associated with over 500 microRNAs from human, mouse, and rat and over 2400 experimentally validated microRNA:target interactions. We illustrate how this resource can be used to create microRNA-focused interaction networks with a biological context using the known biological role of microRNAs and the mRNAs they regulate, enabling discovery of associations between gene products, biological pathways and, ultimately, diseases. This data will be crucial in advancing the field of microRNA bioinformatics and will establish consistent data sets for reproducible functional analysis of microRNAs across all biological research areas.