Ion channelopathies associated genetic variants as the culprit for sudden unexplained death

Use of potassium ion channel and spliceosome proteins as diagnostic biomarkers for sudden unexplained death in schizophrenia

Sudden unexplained death in schizophrenia (SUD-SCZ) is not uncommon and its incidence is approximately three times higher than that in the general population. However, diagnosis of SUD-SCZ remains a great challenge in forensic pathology. This study designed a two-phase study to investigate whether three proteins, namely two potassium ion channel proteins (KCNJ3 and KCNAB1) and one spliceosome protein (SF3B3) that were identified in our previous work, could be applied in the postmortem diagnosis of SUD-SCZ. Immunohistochemical staining of the three biomarkers, followed by a rigorous quantitative analysis, was performed on heart specimens from both SUD-SCZ and control groups. A diagnostic software based on the logistic regression formula derived from the test phase data was then constructed. In the test phase, we found that the staining intensities of KCNJ3, KCNAB1, and SF3B3 were all significantly lower in the SUD-SCZ group (n = 20) as compared with the control group that died from non-natural causes (n = 25), with fold-changes being 14.85 (p < 0.001), 4.13 (p = 0.028) and 2.12 (p = 0.048), respectively. Receiver operating characteristic analysis further illustrated that combination of the three biomarkers achieved the optimal diagnostic specificity (92%) and area under the curve (0.886). In the validation phase, the diagnostic software was confirmed to be a promising tool for predicting the risk of SUD-SCZ in authentic cases. Our study provided a valid strategy towards the practical diagnosis of SUD-SCZ by using KCNJ3, KCNAB1, and SF3B3 proteins as diagnostic biomarkers.

Update on the Genetic Basis of Sudden Unexpected Death in Epilepsy

Epilepsy is a common neurological disorder associated with increased morbidity and mortality. Sudden unexpected death in epilepsy, also known as SUDEP, is the main cause of death in patients with epilepsy. SUDEP has an incidence of 1.2 per 1000 person-years in adults and 0.2 per 1000 person-years in children. SUDEP accounts for 8-17% of deaths in patients with epilepsy. It is commonly associated with a history of generalized tonic-clonic seizures, and its risk may be increased by other factors such as postictal electroencephalographic suppression, prone sleeping position, altered heart rate variability, conduction abnormalities, gender, or antiepileptic medications. Recently, electrocardiograms, electroencephalograms, and imaging markers have helped clinicians stratify SUDEP risk and identify patients in need of close monitoring. However, the pathophysiology of SUDEP is likely multifactorial and still unknown. Improving the knowledge of SUDEP incidence, risk factors, and biomarkers can help design and implement effective prevention strategies.

Feasibility of analysis of the SCN5A gene in paraffin embedded samples in sudden infant death cases at the Pretoria Medico-Legal Laboratory, South Africa

To determine variations in the SCN5A gene linked to inherited cardiac arrhythmogenic disorders in sudden, unexplained infant death (SUID) cases examined at the Pretoria Medico-Legal Laboratory, South Africa. A retrospective study was conducted on SUID cases and controls, analyzing DNA extracted from archived formalin-fixed, paraffin-embedded (FFPE) myocardial tissue samples as well as blood samples. A total of 48 FFPE tissue samples (cases), 10 control FFPE tissue samples and nine control blood samples were included. DNA extracted from all samples was used to test for variations in the SCN5A gene by using high resolution melt (HRM) real-time PCR and sequencing. Genetic analysis showed 31 different single nucleotide variants in the entire study population (n = 67). Five previously reported variants of known pathogenic significance, and 14 variants of benign clinical significance, were identified. The study found 12 different variants in the cases that were not published in any database or literature and were considered novel. Of these novel variants, two were predicted as "probably damaging" with a high level of certainty (found in four case samples), one (identified in another case sample) was predicted to be "possibly damaging" with a 50% chance of being disease-causing, and nine were predicted to be benign. This study shows the significant added value of using genetic testing in determining the cause of death in South African SUID cases. Considering the high heritability of these arrhythmic disorders, post mortem genetic testing could play an important role in the understanding of the pathogenesis thereof and could also aid in the diagnosis and treatment of family members at risk, ultimately preventing similar future cases.