Detection of genetic variation in KCNQ1 gene by high-resolution melting analysis in a prospective-based series of postmortem negative sudden death: comparison of results obtained in fresh frozen and formalin-fixed paraffin-embedded tissues

High-resolution melting (HRM) analysis is a recently developed molecular technique proved to be applicable for detection of genetic variation, notably in sudden cardiac death. In certain circumstances, especially in postmortem genetic investigations, the formalin-fixed and paraffin-embedded (FFPE) tissues are the only DNA source available. The present study aimed to develop HRM assays, optimized for the analysis of FFPE tissues, to detect sequence variations in KCNQ1 exons in a prospective population-based series of postmortem negative sudden death and to compare the results between the paired freshly frozen and FFPE tissue samples simultaneously obtained from the same case. The analyses were conducted in each case of sudden death involving cases younger than 35 years with no significant morphological anomalies particularly with no cardiac structural disease and with negatives toxicological investigations. HRM analysis was successfully optimized for 13 of the 16 exons of the KCNQ1 gene. All mutated samples were correctly identified by HRM whatever the type of tissue tested. However, for FFPE samples, HRM indicated more positive samples than classical sequencing, used in parallel, due to the degradation of DNA by formalin fixation. This is the first postmortem study of KCNQ1 mutation detection with HRM on DNA extracted from FFPE samples with adapted protocol. Despite the false-positive detection, we concluded that the use of HRM as a screening method with FFPE samples to analyze KCNQ1 mutations can reduce the number of sequencing reactions and, thus, results in substantial time and cost savings.