KCNH2 Variant G657S

Summary of observed carriers, functional annotations, and structural context for KCNH2 G657S. Data combine curated literature, international cohorts, and gnomAD observations.

Estimated LQT2 penetrance

15%

1/11 effective observations

Total carriers

1

0 LQT2 · 1 unaffected

Functional studies

1

Publications with functional data

G657S has not been reported in gnomAD. This residue resides in a Hotspot region for LQT2.

We have tested the trafficking efficiency of this variant: 25% of WT with a standard error of 10%. In our analysis we used SE < 20% as 'high quality'. Approximately below 50% of WT is considered PS3 moderate and below 30% is PS3 strong.

Variant features alone are equivalent to phenotyping 1 individuals with LQT2 and 9 unaffected individuals.

In silico predictors

Variant-level computational predictors.
PROVEAN PolyPhen-2 BLAST-PSSM REVEL Penetrance Density LQT2 (%)
-5.812 1.0 0 0.982 46

PROVEAN scores below -2 suggest deleterious impact. REVEL scores above 0.5–0.75 are often interpreted as likely pathogenic. PolyPhen-2 scores above 0.85 are typically pathogenic. BLAST-PSSM reflects evolutionary conservation; more negative values indicate rarer substitutions. Penetrance density summarises neighbouring residue risk (Kroncke et al. 2019).

Reported carrier data

Observed carriers by publication or cohort.
Source Year Carriers Unaffected LQT2 Other Disease
Japan Cohort 2020 1 1 0
Literature, cohort, and gnomAD 1 1 0
Variant features alone 10 9 1

Totals may differ from individual publications due to duplicate patients removed during curation.

Functional data

Functional assay results from published electrophysiology studies. Steady state (S.S.) and peak tail current are relative % to wildtype (100% being no different from wildtype). V1/2 activation and inactivation are the voltages at which half of the maximal current is reached, in mV. Recovery from inactivation and deactivation time are ratios of characteristic time constants with wildtype. HM indicates homomeric channels, HT indicates heteromeric channels.

Homomeric channel data

Published electrophysiology measurements (homomeric).
PubMed ID Cell Type S.S Peak (%WT) Peak Tail IKr (%WT) V1/2 Act. V1/2 Inact. Recov. Inact. Deactivation (%WT)
17823114 Xeno -23.4 None None 0.993288591

Heteromeric channel data

Published electrophysiology measurements (heteromeric).
PubMed ID Cell Type S.S Peak (%WT) Peak Tail IKr (%WT) V1/2 Act. V1/2 Inact. Deactivation (%WT)
17823114 Xeno None None None

Nearby variants

Neighbouring residues within 15 Ångström provide structural context. Variants listed in the right-most column have been observed clinically or in gnomAD. Note that some residues appear multiple times at different distances since the functional KV11.1 channel (protein product of KCNH2/hERG) is a homotetramer and occasionally the same residue from multiple subunits is present within the 15Å window.

Previously observed variants near G657S.
Neighbour residue Distance (Å) Observed variants
657 0 G657S, G657V,
658 4
660 5 S660L,
659 5
654 6
656 6 F656L, F656L, F656L,
661 6 A661V,
655 6
653 6
660 7 S660L,
653 8
662 8
664 8 Q664X,
652 9 Y652X,
553 9 L553V,
663 10
663 10
664 10 Q664X,
654 10
651 10 M651K,
661 10 A661V,
657 10 G657S, G657V,
657 10 G657S, G657V,
659 11
650 11 L650X,
550 11
650 11 L650X,
649 11
665 11 R665Q,
656 12 F656L, F656L, F656L,
554 12
549 12 V549M,
652 12 Y652X,
557 13
658 13
649 13
671 13 A671G, A671Del
662 13
648 13 G648A,
658 13
667 13 Y667X,
652 13 Y652X,
660 13 S660L,
653 14
656 14 F656L, F656L, F656L,
655 14
651 14 M651K,
556 14
666 14
648 14 G648A,
552 14 L552S,
546 14
657 14 G657S, G657V,
661 14 A661V,
653 14
660 15 S660L,
623 15 T623I,
670 15
668 15 S668L,
666 15
622 15 L622F,