PJ3-045 Identification and Characterization of a Novel Mutation M579Fs+75X in HERG

A molecular biological analysis of cardiac ion channel should be useful for exploring the cause of sudden death, especially when there was no obvious morphological abnormality in the heart. We performed an autopsy of 42-year-old female who suffered from sudden death 10 hours after awakening from general anesthesia. She had a history of prolonged QTc interval. Pathological examination showed mild dilatation of the left ventricle (LV) and histological interstitial fibrosis in the LV and atrioventricular conduction system. Sequence analysis revealed AT deletion at nucleotide position 1735-1736 bp (ΔAT) of the HREG gene. In ΔAT cDNA-transfected HEK293T cells, HERG channel current was not detected under voltage clamp. When co-expressed with the wild-type (WT) HERG, the ΔAT did not exert dominant negative suppression on WT HERG channel current. Confocal microscopy revealed more reduced protein expression on the cell surface for the ΔAT than for the WT. These results suggest that the ΔAT dose not act as a dominant negative and cannot co-assemble to form functional channels. The long QT-interval in the case of heterozygous for this mutation may be explained by the reduced amount of functional HERG channels incorporated in the heart cell membrane.