745-4 Sudden “Arrhythmic” Death in Young People with Apparently Normal Heart

The aim of the present study was to assess whether and how often the ultimate diagnosis of structural heart disease underlying sudden cardiac arrest depends on histologic examination of the myocardium and specialized conduction system. Among 186 cases of consecutive sudden cardiovascular death in young people (≤35 yrs) studied from 1979 to 1994, in 59 (32%) gross examination failed to show any cardiac cause of sudden death such as obstructive coronary atherosclerosis, congenital coronary anomaly, cardiomyopathy, valve disease and aortic dissection. The grossly normal heart group consisted of 40 males and 19 females, aged 4–35 yrs (mean 23.7); 27 patients experienced warning symptoms and signs consisting of syncope in 12, ECG abnormalities in 16, and arrhythmias in 11. None had been diagnosed while alive. Detailed histologic study, including examination of ordinary ventricular myocardium as well as serial sections of specialized conduction system, disclosed: 1)focal myocarditis in 17 patients; 2) conduction system abnormalities leading to heart block in 6 patients (sick sinus syndrome in 1, lipomatous discontinuity between the atrial myocardium and the atrioventricular node in 2, sclerotic interruption of His and bundle branches in 2, and longitudinal dissociation of the His bundle in 1). and to ventricular pre-excitation in 15 (atrioventricular by-pass fibers in 9, nodoventricular Mahaim fibers in 4, atriofascicular tract in 1, AV nodal hypoplasia in 1); 3) focal fibrousfatty replacement of the right anterior wall and infundibulum in 5 patients. Sudden death remained unexplained in 16 cases. In conclusion, gross heart features were normal in nearly one third of the young sudden cardiovascular death victims; in 73% of them, however, there was histopathologic evidence of concealed “arrhythmogenic” substrates mostly consisting of conduction system pathology and focal myocarditis

Transcriptional and Translational Effects of Intronic CAPN3 Gene Mutations

Variants of unknown significance in the CAPN3 gene constitute a significant challenge for genetic counselling. Despite the frequency of intronic nucleotide changes in this gene (15–25% of all mutations), so far their pathogenicity has only been inferred by in-silico analysis, and occasionally, proven by RNA analysis. In this study, 5 different intronic variants (one novel) that bioinformatic tools predicted would affect RNA splicing, underwent comprehensive studies which were designed to prove they are disease-causing. Muscle mRNA from 15 calpainopathy patients was analyzed by RT-PCR and splicing-specific-PCR tests. We established the previously unrecognized pathogenicity of these mutations, which caused aberrant splicing, most frequently by the activation of cryptic splicing sites or, occasionally, by exon skipping. The absence or severe reduction of protein demonstrated their deleterious effect at translational level. We concluded that bioinformatic tools are valuable to suggest the potential effects of intronic variants; however, the experimental demonstration of the pathogenicity is not always easy to do even when using RNA analysis (low abundance, degradation mechanisms), and it might not be successful unless splicing-specific-PCR tests are used. A comprehensive approach is therefore recommended to identify and describe unclassified variants in order to offer essential data for basic and clinical geneticists. ©2010 Wiley-Liss, Inc

Identification of an intragenic deletion in the SGCB gene through a re-evaluation of negative next generation sequencing results

A large mutation screening of 504 patients with muscular dystrophy or myopathy has been performed by next generation sequencing (NGS). Among this cohort of patients, we report a case with a severe form of muscular dystrophy with a proximal weakness in the limb-girdle muscles. Her biopsy revealed typical dystrophic features and immunohistochemistry for α- and γ-sarcoglycans showed an absent reaction, addressing the clinical diagnosis toward a sarcoglycanopathy. Considering that no causative point mutation was detected in any of the four sarcoglycan genes, we re-evaluated the NGS data by careful quantitative analysis of the specific reads mapping on the four sarcoglycan genes. A complete absence of reads from the sixth exon of the β-sarcoglycan gene was found. Subsequent array comparative genomic hybridization (CGH) analysis confirmed the result with the identification of a novel 3.3 kb intragenic deletion in the SGCB gene. This case illustrates the importance of a multidisciplinary approach involving clinicians and molecular geneticists and the need for a careful re-evaluation of NGS data

Hearing impairment in MELAS: new prospective in clinical use of microRNA, a systematic review

Aim To evaluate the feasibility of microRNAs (miR) in clinical use to fill in the gap of current methodology commonly used to test hearing impairment in MELAS patients. Material and method A literature review was performed using the following keywords, i.e., MELAS, Hearing Loss, Hearing Impairment, Temporal Bone, Otoacustic Emission (OTOAE), Auditory Brain Response (ABR), and microRNA. We reviewed the literature and focused on the aspect of the temporal bone, the results of electrophysiological tests in human clinical studies, and the use of miR for detecting lesions in the cochlea in patients with MELAS. Results In patients with MELAS, Spiral Ganglions (SG), stria vascularis (SV), and hair cells are damaged, and these damages affect in different ways various structures of the temporal bone. The function of these cells is typically investigated using OTOAE and ABR, but in patients with MELAS these tests provide inconsistent results, since OTOAE response is absent and ABR is normal. The normal ABR responses are unexpected given the SG loss in the temporal bone. Recent studies in humans and animals have shown that miRs, and in particular miRs 34a, 29b, 76, 96, and 431, can detect damage in the cells of the cochlea with high sensitivity. Studies that focus on the temporal bone aspects have reported that miRs increase is correlated with the death of specific cells of the inner ear. MiR − 9/9* was identified as a biomarker of human brain damage, miRs levels increase might be related to damage in the central auditory pathways and these increased levels could identify the damage with higher sensitivity and several months before than electrophysiological testing. Conclusion We suggest that due to their accuracy and sensitivity, miRs might help monitor the progression of SNHL in patients with MELAS