1261
Poster Cat: Sudden death
A POTENT DOMINANT NEGATIVE MUTATION IN HERG IN A CHINESE
FAMILY EXPERIENCING LONG QT SYNDROME, EPILEPSY, AND
UNEXPECTED SUDDEN DEATH
G.L. Li1, J.E. Wu1, W.Q. Han1, S.T. Ma1, A.F. Zhang2, G. Cheng3, X.X. Xue1, C.F. Sun1
1.Department of Cardiovascular Medicine, the First Affiliated Hospital, Xi'an Jiaotong University
College of Medicine, Xi'an, Shaanxi, China
2. Department of Cardiovascular Medicine, the Second Affiliated Hospital of Xi’an Jiaotong
University College of Medicine, Xi’an, Shaanxi, China
3. Department of Cardiovascular Medicine, Shaanxi Provincial People's Hospital, Xi'an, Shaanxi,
China
Objectives: We aimed to screen the mutation in a Chinese family experiencing long QT
syndrome, syncope and unexpected sudden death. Additionally, we also investigated the
functional role of the mutation and its potential contribution to the disease phenotype.
Background: Inherited long-QT syndromes (LQTS) are electrical heart disorders
characterized by torsade de pointes, syncope and cardiac sudden death. Mutations in the
human ether-a-go-go-related gene (hERG) are responsible for the type 2 LQTS (LQT2).
Methods: Regular physical examinations were conducted to exclude the structural heart
diseases. Direct sequencing of candidate gene hERG was performed. The mutant A561VhERG plasmid was constructed and transfected into HEK293 cells. Western blotting and
immunostaining experiments were conducted to evaluate the A561V-hERG protein
expression. Whole cell patch clamp was performed to investigate the function of A561VhERG channels. Additionally, different concentrations of the mutant A561V-hERG
plasmids were transfected into the HEK293 cells stably expressing wide type hERG
(WT-hERG) to simulate the heterozygous mutation.
Results: Based on the characteristics of the ECG, we identified a heterozygous missense
mutation in the S5/pore region of the hERG protein that leads to the substitution of the
amino acid alanine by valine (A561V). A561V-hERG protein could not travel to the
plasma membrane and failed to generate functioning hERG currents in homozygous cells.
When A561V-hERG was expressed simultaneously with WT-hERG, it resulted in
obvious retention of WT-hERG channel protein in the endoplasmic reticulum and
reduced its expression on the membrane. Additionally, A561V-hERG suppressed WThERG currents in a concentration-dependent manner and changed the gating properties of
the channel.
Conclusion: A561V produced a non-function protein. Additionally, it suppressed WThERG channels expression and functional via a dominant-negative effect. This may
explain, in part, the clinical manifestations in the Chinese family with the mutation.