KCNH2 Variant L523A

Summary of observed carriers, functional annotations, and structural context for KCNH2 L523A. Data combine curated literature, international cohorts, and gnomAD observations.

Estimated LQT2 penetrance

12%

1/10 effective observations

Total carriers

0

0 LQT2 · 0 unaffected

Functional studies

1

Publications with functional data

L523A has not been reported in gnomAD. This residue resides in a Mild_Hotspot region for LQT2.

We have tested the trafficking efficiency of this variant: 53% of WT with a standard error of 15%. 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 (%)
None None None None 16

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
Literature, cohort, and gnomAD 0 0 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)
15528201 Xeno 9.2 15.1 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)
15528201 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 L523A.
Neighbour residue Distance (Å) Observed variants
523 0
522 4 G522E,
524 5
526 6
521 6
525 7 K525N, K525N,
429 7 A429P, A429V,
520 8
527 9
430 9
425 10
428 10 S428fsX, S428X, S428L,
426 10 P426H,
528 11 R528W, R528X, R528P,
508 11
432 11
529 12
574 12 M574L, M574V, M574L
570 13
510 13
431 13 F431L, F431L, F431L,
566 13 C566S, C566R, C566G, C566S, C566F,
567 13 I567T, I567M,
530 14
503 14
506 14 I506V,
507 14 P507S, P507L,
427 14 Y427H, Y427S, Y427C,
509 15 D509N,
573 15
504 15 A504V,
563 15 W563G, W563C, W563C, W563X,
569 15 Y569H, Y569C, Y569X,
421 15 T421fsX, T421M,