KCNH2 Variant S818L

Summary of observed carriers, functional annotations, and structural context for KCNH2 S818L. Data combine curated literature, international cohorts, and gnomAD observations.

Estimated LQT2 penetrance

44%

16/28 effective observations

Total carriers

18

14 LQT2 · 3 unaffected

Functional studies

3

Publications with functional data

S818L is present in 2 alleles in gnomAD. This residue resides in a Hotspot region for LQT2.

We have tested the trafficking efficiency of this variant: 9% of WT with a standard error of 4%. 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 2 individuals with LQT2 and 8 unaffected individuals.

In silico predictors

Variant-level computational predictors.
PROVEAN PolyPhen-2 BLAST-PSSM REVEL Penetrance Density LQT2 (%)
-5.213 1.0 -3 0.97 57

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
24667783 2015 1 0 1
Japan Cohort 2020 6 0 6
Italy Cohort 2020 2 1 1
France Cohort 2020 2 1 1
23098067 2012 1 0 1
10086971 1999 2 1 1
26496715 2015 3 0 3
Literature, cohort, and gnomAD 18 3 14
Variant features alone 10 8 2

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)
10996323 Xeno 0 None None None None
15961404 HEK293 0 None None None None
16432067 HEK293 5 None None None None

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)
10996323 Xeno 51 -3.0 None None
15961404 HEK293 None None None
16432067 HEK293 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 S818L.
Neighbour residue Distance (Å) Observed variants
818 0 S818A, S818W, S818L,
773 4
819 5 N819K, N819K,
817 5
772 5
820 5 G820R, G820R,
774 5 D774Y, D774X,
862 6 L862P,
776 6 L776I, L776P,
816 7 G816V,
863 7 R863X, R863P
775 8
770 8
821 8 D821E, D821E,
771 8 H771fsX, H771R,
807 9 E807X,
806 9 G806R, G806R,
749 10
861 10 N861H, N861I,
791 10 R791W, R791Q,
822 10 V822M, V822L, V822L,
815 10
845 11
747 11
860 11
789 11
777 11
778 11 A778T,
805 11 F805S, F805C,
790 12
748 12
750 12 C750X,
812 12 Y812S,
844 12 M844V,
769 12
780 13
808 13
752 13 R752W, R752Q, R752P,
768 13
792 13
779 14
835 14 R835W, R835fsX, R835Q,
796 14 V796L, V796L, V796Del,
823 14 R823W, R823fsX, R823T, R823Q,
847 14
753 14 A753S,
814 14
846 14 P846T, P846S,
858 14 I858V, I858T,
723 14 C723R, C723G, C723X,
797 14 A797T,
746 15 A746S, A746X,
61 15 Q61R,
751 15 L751V,
809 15
859 15 T859M, T859R,
794 15 V794I, V794D,