Molecular autopsy in young sudden cardiac death victims with suspected cardiomyopathy

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Abstract

The aim of this investigation was to identify and characterise pathogenic mutations in a sudden cardiac death (SCD) cohort suspected of cardiomyopathy in persons aged 0–40 years.

The study material for the genetic screening of cardiomyopathies consisted of 41 cases and was selected from the case database at the Institute of Forensic Medicine. Mutational screening by DNA sequencing was performed to detect mutations in DNA samples from deceased persons suspected of suffering from hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and arrhythmogenic right ventricle cardiomyopathy (ARVC).

A total of 9 of the examined 41 cases had a rare sequence variant in the MYBPC3, MYH7, LMNA, PKP2 or TMEM43 genes, of which 4 cases (9.8%) were presumed to be pathogenic mutations. The presumed pathogenic mutations were distributed with one case of suspected HCM and DCM (MYH7; p.R442H), one case of suspected DCM (LMNA; p.R471H), and two cases of suspected ARVC (PKP2; p.R79X and LMNA; p.R644C).

The presented data adds important information on the genetic elements of SCD in the young, and calls for expert pathological evaluation and molecular autopsy in the post-mortem examination of SCD victims with structural anomalies of the heart.

Introduction

Sudden cardiac death (SCD) constitutes one of the most important unsolved challenges in the practice of forensic pathology. Several researchers have found that most sudden unexplained deaths (SUD) are caused by hereditary conditions of which cardiovascular diseases are the most frequent [1], [2], [3]. These conditions are genetically heterogeneous, making diagnosis and counselling difficult, with the risk of repeated sudden deaths in the same family. Incidence rates of SCD among persons aged 1–35 years, upon autopsy, were recently found to be 1.1 per 100,000 in a Danish study [4]. In this study, we present a genetic examination of structural heart diseases, which include cardiomyopathies, such as hypertrophic, dilated and arrhythmogenic right ventricle cardiomyopathy (HCM, DCM and ARVC), in a group of SCD in children and young adults. Most often, these inherited cardiac disorders give rise to lethal ventricular arrhythmias without any previous pathological clinical history and they show an autosomal dominant pattern of inheritance. Genetic screening of the major genes involved in cardiomyopathies can help determine the cause of death and may help to evaluate the potential risk of relatives. Table 1 summarises the most commonly studied genes associated with cardiomyopathies included in this study. Several other genes have been studied and found associated with cardiomyopathies, especially hypertrophic- and dilated cardiomyopathies, but with a minor frequency in patients. We performed molecular genetic studies on a selected group of the major genes associated with hereditary cardiomyopathies using blood samples from deceased persons suspected of cardiomyopathies based on autopsy findings.

Section snippets

Study subjects

The study material for the genetic screening of the major genes associated with cardiomyopathies (HCM, DCM, and ARVC) consisted of 41 cases with structural changes related to cardiomyopathies, aged 0–40 years that died in the period 1998–2007. DNA was obtained from post-mortem blood and stored at −80 °C. The material was selected from our own database by age (0–40 years) and cause of death (cardiovascular or an unknown cause of death at autopsy), and a manual selection of cases was then

Bioinformatics analyses

We aligned sequence traces to JUP (NM_002230.2), DSP (NM_004415.2), PKP2 (NM_004572.2), DSG2 (NM_001943.2), DCS2 (NM_004949.2), TMEM43 (NM_024334.2), MYH7 (NM_000257.2), MYBPC3 (NM_000256.3), and LMNA (NM_170707.2) reference sequences using SeqScape version 2.5 or 2.7 (Applied Biosystems). All variants were queried in gene specific mutation databases (http://www.arvcdatabases.info and http://lovd.nl/2.0/). Sequence variants leading to amino acid substitutions were evaluated using the PolyPhen 2

HCM, DCM, and HCM–DCM groups

Samples considered included 27 autopsy cases (21 male/6 female; aged 9–40 years), with structurally changes related to HCM and DCM (Fig. 1). We found that four of the 27 deceased had a rare sequence variant in the LMNA-, MYH7- or MYBPC3 genes. All presumed pathogenic mutations (p) are summarised in Table 2 (case; p1–p4), and presumed benign mutations (b) are summarised in Table 3 (case; b1–b5).

Case p1; had a rare sequence variant in the LMNA gene (p.R471H). Case p2; had a rare sequence variant

Discussion

We found that 9 of 41 cases (22%) with structural changes related to cardiomyopathies had a rare sequence variant in the LMNA, MYBPC3, MYH7, PKP2 or TMEM43 genes, of which 4 cases (9.8%) were suspected to be pathogenic changes (Fig. 1). The suspected pathogenic mutations were found in 1 case (p1) of suspected DCM (LMNA; p.R471H), 1 case (p2) of suspected HCM and DCM (MYH7; p.R442H) and 2 cases (p3–p4) of suspected ARVC (PKP2; p.R79X and LMNA; p.R644C). All 4 variants (p1–p4) have previously

Conclusion

In this SCD cohort, 22% had a rare sequence variant in the LMNA, MYBPC3, MYH7, PKP2 or TMEM43 genes, and 9.8% were suspected to be pathogenic variants. When SCD appears in younger people with structural anomalies of the heart, autopsy investigation including molecular autopsy will contribute to establish the cause of death. These results will subsequently be important in the risk stratification management and the genetic counselling of family members.

Conflict of interest

None declared.

Acknowledgements

This work was supported by Research Grants from the Jørgen Møllers Foundation, the Augustinus Foundation, the Grosserer A. V. Lykfeldt and Wife Foundation, the Helga and Peter Kornings Foundation, the Grosserer Valdemar Foersom and Thyra Foersom Foundation, and Aarhus University. The authors are grateful to Anette Stenderup, Gitte Glistrup Nielsen, Anette Funder and Jakob Hansen for excellent technical assistance.

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