KCNQ1 Variant G621C Detail

We estimate the penetrance of LQTS for KCNQ1 G621C is 23%. This variant was found in a total of 3 carriers in 0 papers or gnomAD, 0 had LQTS. G621C is present in 3 alleles in gnomAD. G621C has not been functionally characterized. This residue is located in a Mild_Hotspot region for LQT1. In silico predictions, functional data (if available), and location in structure are equivalent to observing 2 individuals with LQT1 and 8 unaffected individuals. These data combined with observations of carriers lead us to estimate the LQTS penetrance for KCNQ1 G621C around 23% (2/13).

In Silico Data

PROVEAN PolyPhen-2 BLAST-PSSM REVEL Penetrance Density (%)
-0.95 0.718 -2 0.593 33
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: - 3 3 0
VARIANT FEATURES ALONE: - 10 8 2 -
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.

G621C 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
621 0 G621S, G621C, G621D,
620 4
622 4 G622S,
619 5 L619M,
623 5
618 7
624 7
617 8
625 8 P625R,
616 8
626 8 G626S,
615 9
627 9
614 10 H614del,
628 10 G628S, G628D,
613 11
629 11 G629S,
612 11
630 11 P630S, P630T,
611 12 D611N, D611Y,
631 12 P631R,
610 13
632 13
609 13
633 13
608 14
634 14
607 14 A607T,
635 14 G635R, G635R,
606 15
636 15