KCNH2 Variant D609G

Summary of observed carriers, functional annotations, and structural context for KCNH2 D609G. Data combine curated literature, international cohorts, and gnomAD observations.

Estimated LQT2 penetrance

50%

90% CI: 28.2% – 72.3%

6/13 effective observations

Total carriers

3

3 LQT2 · 0 unaffected

Functional studies

1

Publications with functional data

D609G has not been reported in gnomAD. This residue resides in a Hotspot region for LQT2.

We have tested the trafficking efficiency of this variant: 0% of WT with a standard error of 0%. 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 3 individuals with LQT2 and 7 unaffected individuals.

In silico predictors

Variant-level computational predictors.
PROVEAN PolyPhen-2 BLAST-PSSM REVEL Penetrance Density LQT2 (%)
-6.172 0.973 -2 0.889 90

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
30844837 1 0 Fibromuscular dysplasia
15500450 2005 1 0 1
26496715 2015 2 0 2
Literature, cohort, and gnomAD 3 0 3
Variant features alone 10 7 3

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)
15500450 Xeno 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)
15500450 Xeno 9 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 D609G.
Neighbour residue Distance (Å) Observed variants
609 0 D609N, D609G,
610 5
606 5 S606Del, S606P, S606F,
608 5
612 5 V612L, V612L, V612A,
635 6 N635I,
613 6 T613A, T613L, T613K, T613M,
607 6
611 7 Y611D,
605 7 P605L,
638 8 K638E, K638D, K638Del, K638R,
614 8 A614T, A614V,
589 8 L589P,
593 9 I593V, I593K, I593T, I593R, I593X,
634 9 T634P, T634A, T634S, T634S, T634I,
595 10 K595E, K595N, K595N,
615 10 L615V, L615F,
586 10 L586M,
569 10 Y569H, Y569C, Y569X,
431 10 F431L, F431L, F431L,
639 10 I639F, I639N,
616 10 Y616S,
604 10 G604S, G604C, G604D,
636 10
633 10 N633D, N633S, N633I,
585 11 W585C, W585C,
590 11 G590D, G590V,
592 11 Q592X,
565 12
594 12
427 12 Y427H, Y427S, Y427C,
637 12 E637K, E637G, E637X,
632 12 P632A, P632S,
630 12 V630I, V630T, V630A,
568 13 W568C, W568C,
566 13 C566S, C566R, C566G, C566S, C566F,
617 13 F617L, F617V, F617L, F617L,
629 13 N629D, N629T, N629S, N629I, N629K, N629K,
642 13 I642V, I642Del
588 13 N588D, N588K, N588K,
603 13 G603D,
562 14 H562P, H562R, H562Q, H562Q,
573 14
597 14 Y597H, Y597C,
430 14
641 14 S641P, S641F,
596 14 P596T, P596S, P596R, P596L,
591 14 D591N, D591H,
583 14 I583V,
572 14 G572S, G572R, G572C, G572D,
618 14 T618S, T618S,
587 14
584 15 G584S, G584R, G584C,
570 15
432 15
575 15 E575K,
619 15