Retrospective analysis-based prioritization and degradation pattern characterization of sudden unexplained death...

Genetic factors are known to have important roles in sudden unexplained death (SUD) of apparently healthy individuals. Currently, molecular autopsy is considered an effective diagnostic tool in the multidisciplinary management of SUD. Recent studies highlighted the contribution of regulatory variants to complex genetic disorders. Pathogenic variants within the untranslated regions of SUD susceptibility genes were also identified in certain cases. However, the functional validation of pathogenic variants outside of the coding regions remains challenging. As the most direct method, transcriptome analysis could be performed at the same time with molecular autopsy to identify the abnormal expression of SUD susceptibility genes, while the post-mortem degradation of mRNA in myocardial tissues has made it difficult to interpret the transcriptome profiling results. In this study, we performed a retrospective analysis-based prioritization of SUD susceptibility genes based on the distribution of pathogenic genetic variants in previous studies with molecular autopsy findings reported. After gene prioritization, we analyzed the transcriptome data of 432 left ventricle tissues with different sampling time intervals from the Genotype-Tissue Expression database, in order to characterize the degradation pattern of prioritized SUD susceptibility genes. Furthermore, RNA degradation difference between unfrozen and thawed samples was investigated. We demonstrated that with proper segmentation of genes according to their degradation patterns, a partial least squares-discriminant analysis could effectively recognize the expression difference of targeted genes between normal samples and simulated SUD cases. Taken together, our findings presented a strategy for the interpretation of RNA profiling results during the forensic investigation of SUD.