KCNH2 Variant T399P Detail

We estimate the penetrance of LQTS for KCNH2 T399P is 32%. We are unaware of any observations of this variant in individuals. T399P is not present in gnomAD. T399P has not been functionally characterized. This residue is located in a Mild_Hotspot region for LQT2. In silico predictions, functional data (if available), and location in structure are equivalent to observing 3 individuals with LQT2 and 7 unaffected individuals.These data combined with observations of carriers lead us to estimate the LQTS penetrance for KCNQ1 T399P around 32% (3/10).

In Silico Data

PROVEAN PolyPhen-2 BLAST-PSSM REVEL Penetrance Density (%)
-5.527 0.121 -1 0.95 39
PROVEAN scores less than -2 are considered deleterious. REVEL scores higher than 0.5 or 0.75 are considered likely pathogenic (higher sensitivity with the former cutoff, higher specificity with the latter cutoff). A PolyPhen-2 score of 0.85 or greater is considered likely pathogenic. BLAST-PSSM reflects the evolutionary conservation of residue substitutions, more negative numbers indicate fewer observations of the specific substitution than is expected. Penetrance density is our previously published method to calculate the average LQTS probability density in a shell of residues surrounding a residue of interest (Kroncke et al. 2019).

Reported Carrier Data

PubMed ID Year Carriers Unaffected LQT2 Other Disease
Summary totals might not agree with the literature table because of duplicate patients, which were excluded from the total counts. We do not distinguish here between multiple missense codons. Missense variants are combined across degenerate codon substitutions since codon-level data were not consistently available for curation.

T399P has 26 previously observed neighbors within 15 angstroms

A residue within a folded protein on average has nearest neighbors that fall roughly into two shells: a "nearest" neighbor around 5-6 angstroms and a second shell around 11 angstroms. NOTE: 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 15A window. All variants shown in the rightmost column have been observed in at least one individual in the literature or gnomAD.

Neighbor Distance (Angstroms) Variants Observed in Individuals
399 0
398 4 W398L, W398X,
400 4 I400N,
472 7 R472X, R472C,
401 7
485 8 H485X,
473 8 T473P,
484 8
474 9 T474I,
486 10
469 11
404 11
406 12
483 12 V483I,
489 12 I489F, I489I,
402 12 H402R,
403 12
471 12 F471X,
407 12
470 13 N470D,
468 13 L468F, L468R, L468X,
482 13 V482A,
475 13 Y475C, Y475Del,
487 13 G487R, G487S,
488 14 R488C, R488H,
405 14