KCNQ1 Variant H403Q Detail

We estimate the penetrance of LQTS for KCNQ1 H403Q is 60%. We are unaware of any observations of this variant in individuals. H403Q is not present in gnomAD. H403Q has not been functionally characterized. This residue is located in a Hotspot region for LQT1. In silico predictions, functional data (if available), and location in structure are equivalent to observing 5 individuals with LQT1 and 5 unaffected individuals. These data combined with observations of carriers lead us to estimate the LQTS penetrance for KCNQ1 H403Q around 60% (5/10).

In Silico Data

PROVEAN PolyPhen-2 BLAST-PSSM REVEL Penetrance Density (%)
-1.36 0.06 1 0.6 67
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 LQT1 Other Disease
LITERATURE, COHORT, AND GNOMAD: - 0 0 0
VARIANT FEATURES ALONE: - 10 5 5 -
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.

H403Q has 31 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. This results from the fact that the functional KV7.1 channel 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
403 0 H403P,
402 4
404 4
401 5 R401W, R401Q,
405 5
400 7
406 7
399 8 A399S, A399V, A399G,
407 8
398 8 K398R,
408 8 P408A,
397 9 R397W, R397Q, R397G,
409 9
396 10
410 10
395 11 Y395C,
411 11
394 11 I394L,
412 11 P412S,
393 12 K393N,
413 12 K413R,
392 13 W392R, W392R, W392ins,
414 13
391 13 T391A, T391I,
415 13
390 14
416 14 V416M,
389 14 S389P,
417 14 V417M,
388 15 D388H, D388N,
418 15 V418I,