KCNH2 Variant T436M

Summary of observed carriers, functional annotations, and structural context for KCNH2 T436M. Data combine curated literature, international cohorts, and gnomAD observations.

Estimated LQT2 penetrance

3%

90% CI: 0.3% – 14.5%

1/32 effective observations

Total carriers

22

0 LQT2 · 11 unaffected

Functional studies

2

Publications with functional data

T436M is present in 20 alleles in gnomAD. This residue resides in a Non_Hotspot region for LQT2.

We have tested the trafficking efficiency of this variant: 40% of WT with a standard error of 19%. 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 (%)
-0.424 0.021 -1 0.559 6

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
Italy Cohort 2020 1 1 0
11854117 2002 1 0 1
26129877 2015 1 1 atrial fibrillation
Literature, cohort, and gnomAD 22 11 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)
16432067 HEK293 135 None None None None
26129877 CHO 143 1.4 6.5 None 1.735099338

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)
16432067 HEK293 None None None
26129877 CHO 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 T436M.
Neighbour residue Distance (Å) Observed variants
436 0 T436M,
435 4 E435G, E435X,
437 4
434 5
438 5 E438K, E438X,
433 7
439 7
432 8
440 8 P440L,
431 8 F431L, F431L, F431L,
441 8 P441R, P441L,
430 9
442 9
429 10 A429P, A429V,
443 10 T443fsX, T443N,
428 11 S428fsX, S428X, S428L,
444 11 E444K, E444D, E444D,
427 11 Y427H, Y427S, Y427C,
445 11
426 12 P426H,
446 12
425 13
447 13 Y447X,
424 13
448 13 A448T, A448S,
423 14
449 14
422 14 A422T,
450 14
421 15 T421fsX, T421M,
451 15 P451L