KCNQ1 Variant G646C Detail

We estimate the penetrance of LQTS for KCNQ1 G646C is 10%. We are unaware of any observations of this variant in individuals. G646C is not present in gnomAD. G646C has not been functionally characterized. This residue is located in a Non_Hotspot region for LQT1. In silico predictions, functional data (if available), and location in structure are equivalent to observing 0 individuals with LQT1 and 10 unaffected individuals. These data combined with observations of carriers lead us to estimate the LQTS penetrance for KCNQ1 G646C around 10% (0/10).

In Silico Data

PROVEAN PolyPhen-2 BLAST-PSSM REVEL Penetrance Density (%)
-1.21 0.855 -3 0.574 1
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 10 0 -
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.

G646C 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
646 0
645 4
647 4
644 5
648 5 V648I,
643 7 G643S,
649 7 D649N, D649G,
642 8
650 8
641 8 P641L,
651 8
640 9 Q640L,
652 9
639 10
653 10 F653Y,
638 11
654 11
637 11
655 11
636 12
656 12
635 13 G635R, G635R,
657 13 N657S,
634 13
658 13 T658N,
633 14
659 14
632 14
660 14 P660S,
631 15 P631R,
661 15