Sudden cardiac death in young athletes: Literature review of molecular basis

Intense athletic training and competition can rarely result in sudden cardiac death (SCD). Despite the introduction of pre-participation cardiovascular screening, especially among young competitive athletes, sport-related SCD remains a debated issue among medical personnel, sports communities and laypersons alike, and generates significant media attention. The most frequent cause of SCD is a hidden inherited cardiomyopathy, the athletes may not even be aware of. Predictive medicine, by searching the presence of pathogenic alterations in cardiac genes, may be an integrative tool, besides the conventional ones used in cardiology (mainly electro and echocardiogram), to reach a definitive diagnosis in athletes showing signs/symptoms, even borderline, of inherited cardiomyopathy/ channelopathy, and in athletes presenting family history of SCD and/or of hereditary cardiac disease. In this review, we revised the molecular basis of the major cardiac diseases associated to sudden cardiac death and the clinical molecular biology approach that can be used to perform risk assessment at DNA level of sudden cardiac death, contributing to the early implementation of adequate therapy. Alterations can occur in ion channel genes, in genes encoding desmosomal and junctional proteins, sarcomeric and Z-disc proteins, proteins for the cytoskeleton and the nuclear envelope. The advent of next generation sequencing (NGS) technology has provided the means to search for mutations in all these genes, at the same time. Therefore, this molecular approach should be the preferred methodology for the aforementioned purpose

Mitochondrial mutation in adult patient with Hypertrophic Cardiomyopathy and renal failure

Background: Mitochondrial diseases (MDs) (1:5000-10000) represents a wide group of human disorders associated with mitochondrial DNA (mtDNA) variations causing defect of oxidative phosphorylation system, whereas nuclear genome mutations are somewhat rare. The extremely heterogeneous clinical phenotype, extending from oligosymptomatic condition to complex syndromes involving neurological, ophtalmological, gastroenterological and endocrine features, depends to the involved tissue well as to the specific mtDNA mutations and their heteroplasmic level. Diabetes and deafness are common features of mitochondrial diseases, while renal alterations are rarely reported, especially in adults, probably because of lack of association to mitochondrial conventional phenotypes. Case Presentation: We investigated a 62 years old male affected by hypertrophic cardiomyopathy (HCM) and renal failure that caused already a bilateral transplantation. Pathological anamnesis revealed also diabetes, deafness and Crohn disease. Family history of cardiomyopathy showed a strong mitochondrial involvement. The proband's mother, three brothers (one of which died of renal failure at 26 years), the sister and her child were affected. Materials and Methods: Genomic DNA from peripheral blood and buccal cells was extracted with the Kit-Nucleon-BACC2 (Illustra DNA-Extraction Kit-BACC2-GE Healthcare, UK) and the whole mitochondrial genome was amplified by two pair of primers designed in our laboratory to generate two overlapping fragments. The PCR products were then sequenced and compared to mitochondrial reference sequence (rCRS NC_012920). Results and Discussion: In both biological samples the mtDNA analysis showed the heteroplasmic A3243G mutation in the tRNALeu (UUR), frequently associated with MDs. A cardiological involvement leading to hypertrophic remodelling, caused to mitochondria intermyofibrillar proliferation, occurs up to 40% of patients with mtDNA disease. Molecular backgrounds of mitochondrial cardiomyopathy of adult age are still quite poorly known and the A3243G mutation in tRNA Leu(UUR) of mtDNA has been reported in 40-60% of patients with HCM. The interesting finding presented here support the knowledge that mitochondrial gene altertation represents a possible etiology in cardiological patients with unexplained renal failure. This is particularly true, as in this case, when other associated symtoms linked with dysfunctional oxidative phosphorylation are present. The case presented in this report further suggests that a differential diagnosis in presence of HCM should be solved by a multidisciplinary approach together with mutation analysis of mitochondrial DNA

Diagnosi molecolare di sindrome di Brugada in un giovane atleta mediante il sequenziamento di un pannello multigenico con tecniche di nuova generazione

Mutations in genes driving the molecular pathways that regulate myocardial functions can predispose to many independent cardiopathies and also to sudden cardiac death (SCD) even in asymptomatic subjects. The overlapping clinical signs or symptoms or even silent phenotypes make it difficult to diagnose these diseases, therefore the risk of undiagnosed disease could be high especially in young adults and athletes, which may then incur in SCD. We describe the case of a clinical asymptomatic eight-year-old child, practicing soccer game, who underwent a screening medical examination to undertake the path of an increasing physical activity to become a competitive athlete, where abnormal signs at ECG indicated a suspicion of an arrhythmogenic heart disease. Molecular screening analysis, to discriminate among the various predisposing gene alterations, was performed using a 75 gene-panel for arrhythmias customized in our laboratory. The child resulted carrier of a loss-of-function mutation in the SCN5A gene (c.1126C>T). About 25% of Brugada patients carry mutations in this gene coding for the cardiac sodium channel. The loss-of-function mutations in SCN5A gene induce alterations of sodium ion conduction in cardiomyocytes, compatible with the Brugada Syndrome. This case report highlights the importance of the implementation of a rapid, sensitive and wide molecular screening to shed light on possible genetic alterations present also in asymptomatic athletes with negative family history, which may often remain undiagnosed, thus exposed to high risk of sudden death

Diagnostic and Therapeutic Potential for HNP-1, HBD-1 and HBD-4 in Pregnant Women with COVID-19

Pregnancy is characterized by significant immunological changes and a cytokine profile, as well as vitamin deficiencies that can cause problems for the correct development of a fetus. Defensins are small antimicrobial peptides that are part of the innate immune system and are involved in several biological activities. Following that, this study aims to compare the levels of various cytokines and to investigate the role of defensins between pregnant women with confirmed COVID-19 infection and pregnant women without any defined risk factor. TNF-α, TGF-β, IL-2 and IL-10, β-defensins, have been evaluated by gene expression in our population. At the same time, by ELISA assay IL-6, IL-8, defensin alpha 1, defensin beta 1 and defensin beta 4 have been measured. The data obtained show that mothers affected by COVID-19 have an increase in pro-inflammatory factors (TNF-α, TGF-β, IL-2, IL-6, IL-8) compared to controls; this increase could generate a sort of "protection of the fetus" from virus attacks. Contemporarily, we have an increase in the anti-inflammatory cytokine IL-10 and an increase in AMPs, which highlights how the mother's body is responding to the viral attack. These results allow us to hypothesize a mechanism of "trafficking" of antimicrobial peptides from the mother to the fetus that would help the fetus to protect itself from the infection in progress

Protein Thermodynamic Destabilization in the Assessment of Pathogenicity of a Variant of Uncertain Significance in Cardiac Myosin Binding Protein C.

In the era of next generation sequencing (NGS), genetic testing for inherited disorders identifies an ever-increasing number of variants whose pathogenicity remains unclear. These variants of uncertain significance (VUS) limit the reach of genetic testing in clinical practice. The VUS for hypertrophic cardiomyopathy (HCM), the most common familial heart disease, constitute over 60% of entries for missense variants shown in ClinVar database. We have studied a novel VUS (c.1809T>G-p.I603M) in the most frequently mutated gene in HCM, MYBPC3, which codes for cardiac myosin-binding protein C (cMyBPC). Our determinations of pathogenicity integrate bioinformatics evaluation and functional studies of RNA splicing and protein thermodynamic stability. In silico prediction and mRNA analysis indicated no alteration of RNA splicing induced by the variant. At the protein level, the p.I603M mutation maps to the C4 domain of cMyBPC. Although the mutation does not perturb much the overall structure of the C4 domain, the stability of C4 I603M is severely compromised as detected by circular dichroism and differential scanning calorimetry experiments. Taking into account the highly destabilizing effect of the mutation in the structure of C4, we propose reclassification of variant p.I603M as likely pathogenic. Looking into the future, the workflow described here can be used to refine the assignment of pathogenicity of variants of uncertain significance in MYBPC3.J.A.C. was funded by the Ministerio de Ciencia, Innovación y Universidades (MCNU) through grants BIO2017-83640-P (AEI/FEDER, UE) and RYC-2014-16604, the European Research Area Network on Cardiovascular Diseases (ERA-CVD/ISCIII, MINOTAUR, AC16/00045), the Comunidad de Madrid (P2018/NMT-4443) and the CNIC-Severo Ochoa intramural grant program (03-2016 IGP). The CNIC is supported by the Instituto de Salud Carlos III (ISCIII), MCNU and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505). G.F. was funded by the Ministero dell’Istruzione, dell’Università e della Ricerca-Rome PS35-126/IND.S

Molecular Epidemiology of Mitochondrial Cardiomyopathy: A Search Among Mitochondrial and Nuclear Genes

Mitochondrial Cardiomyopathy (MCM) is a common manifestation of multi-organ Mitochondrial Diseases (MDs), occasionally present in non-syndromic cases. Diagnosis of MCM is complex because of wide clinical and genetic heterogeneity and requires medical, laboratory, and neuroimaging investigations. Currently, the molecular screening for MCM is fundamental part of MDs management and allows achieving the definitive diagnosis. In this article, we review the current genetic knowledge associated with MDs, focusing on diagnosis of MCM and MDs showing cardiac involvement. We searched for publications on mitochondrial and nuclear genes involved in MCM, mainly focusing on genetic screening based on targeted gene panels for the molecular diagnosis of the MCM, by using Next Generation Sequencing. Here we report twelve case reports, four case-control studies, eleven retrospective studies, and two prospective studies, for a total of twenty-nine papers concerning the evaluation of cardiac manifestations in mitochondrial diseases. From the analysis of published causal mutations, we identified 130 genes to be associated with mitochondrial heart diseases. A large proportion of these genes (34.3%) encode for key proteins involved in the oxidative phosphorylation system (OXPHOS), either as directly OXPHOS subunits (22.8%), and as OXPHOS assembly factors (11.5%). Mutations in several mitochondrial tRNA genes have been also reported in multi-organ or isolated MCM (15.3%). This review highlights the main disease-genes, identified by extensive genetic analysis, which could be included as target genes in next generation panels for the molecular diagnosis of patients with clinical suspect of mitochondrial cardiomyopathies