Identification of an ethnic-specific variant (V207M) of the KCNQ1 cardiac potassium channel gene in sudden unexplained death and implications from a knock-in mouse model.

We performed mutation analysis for genes implicated in long QT syndrome (KCNQ1, KCNH2, and SCN5A) in 17 sudden unexplained death autopsy cases. Single-strand conformation polymorphism and subsequent DNA sequencing analyses revealed that in one case, there was a variant, V207M of KCNQ1, a gene encoding a cardiac potassium channel. This case, a 40-year-old African male, was shown to have a heterozygous missense mutation (V207M), which has been previously reported to be ethnic-specific. The heterozygous V207M mutation was found in one case (0.23%) of 444 alleles from African individuals. We developed a knock-in mouse model carrier of the Kcnq1-V206M mutation, the mouse equivalent to the KCNQ1-V207M mutation identified in the victim. Significant prolongation of QT intervals was observed in the Kcnq1(V206M/V206M) mice. These findings suggest that the KCNQ1-V207M mutation might be pathogenic and might have been associated with the cause of death in the present case.