Not all hERG pore domain mutations have a severe phenotype: G584S has an inactivation gating defect with mild phenotype compared to G572S, which has a dominant negative trafficking defect and a severe phenotype.
BACKGROUND
Mutations in the pore domain of the human ether-a-go-go-related gene (hERG) potassium channel are associated with higher risk of sudden death. However, in many kindreds clinical presentation is variable, making it hard to predict risk. We hypothesized that in vitro phenotyping of the intrinsic severity of individual mutations can assist with risk stratification.


RESULTS
We analyzed 2 hERG pore domain mutations, G572S and G584S. Similar to 90% of hERG missense mutations, G572S-hERG subunits did not traffic to the plasma membrane but could coassemble with WT subunits and resulted in a dominant negative suppression of hERG current density. The G584S-hERG subunits traffic normally but have abnormal inactivation gating. Computer models of human ventricular myocyte action potentials (AP), incorporating Markov models of the hERG mutants, indicate that G572S-hERG channels would cause more severe AP prolongation than that seen with G584S-hERG channels.


CONCLUSIONS
hERG-G572S and -G584S are 2 pore domain mutations that involve the same change in sidechain but have very different in vitro phenotypes; G572S causes a dominant negative trafficking defect, whereas G584S is the first hERG missense mutation where the cause of disease can be exclusively attributed to enhanced inactivation. The G572S mutation is intrinsically more severe than the G584S mutation, consistent with the overall clinical presentation in the 2 small kindreds studied here. Further investigation, involving a larger number of cohorts, to test the hypothesis that in vitro phenotyping of the intrinsic severity of a given mutation will assist with risk stratification is therefore warranted.
Zhao
Jing Ting
JT
Victor Chang Cardiac Research Institute, Sydney, Australia.
Hill
Adam P
AP
Varghese
Anthony
A
Cooper
Antony A
AA
Swan
Heikki
H
Laitinen-Forsblom
Päivi J
PJ
Rees
Mark I
MI
Skinner
Jonathan R
JR
Campbell
Terence J
TJ
Vandenberg
Jamie I
JI
D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D002648:Child; D006224:Cricetinae; D003412:Cricetulus; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000235:genetics*; D005260:Female; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010375:Pedigree; D010641:Phenotype; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D012720:Severity of Illness Index; D055815:Young Adult
D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human