rs199472696

Positions:

• chr11-2570670-C-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_000218.3(KCNQ1):​c.520C>T​(p.Arg174Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000031 in 1,612,454 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R174H) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 33)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: KCNQ1 NM_000218.3 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:10 O:1
• Conservation: PhyloP100: 3.56

Genes affected

KCNQ1 (HGNC:6294): (potassium voltage-gated channel subfamily Q member 1) This gene encodes a voltage-gated potassium channel required for repolarization phase of the cardiac action potential. This protein can form heteromultimers with two other potassium channel proteins, KCNE1 and KCNE3. Mutations in this gene are associated with hereditary long QT syndrome 1 (also known as Romano-Ward syndrome), Jervell and Lange-Nielsen syndrome, and familial atrial fibrillation. This gene exhibits tissue-specific imprinting, with preferential expression from the maternal allele in some tissues, and biallelic expression in others. This gene is located in a region of chromosome 11 amongst other imprinted genes that are associated with Beckwith-Wiedemann syndrome (BWS), and itself has been shown to be disrupted by chromosomal rearrangements in patients with BWS. Alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Aug 2011]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 9 uncertain in NM_000218.3
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr11-2570671-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 53059.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.993
• PP5: Variant 11-2570670-C-T is Pathogenic according to our data. Variant chr11-2570670-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 53058.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr11-2570670-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
KCNQ1	NM_000218.3	c.520C>T	p.Arg174Cys	missense_variant	3/16	ENST00000155840.12

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
KCNQ1	ENST00000155840.12	c.520C>T	p.Arg174Cys	missense_variant	3/16	1	NM_000218.3	P1
KCNQ1	ENST00000335475.6	c.139C>T	p.Arg47Cys	missense_variant	3/16	1
KCNQ1	ENST00000496887.7	c.259C>T	p.Arg87Cys	missense_variant	4/16	5
KCNQ1	ENST00000646564.2	c.478-12765C>T		intron_variant

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152172 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0000654

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.00000401 AC: 1 AN: 249462 Hom.: 0 AF XY: 0.00000739 AC XY: 1 AN XY: 135368

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000290

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1460282 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 726530

Gnomad4 AFR exome AF: 0.0000597

Gnomad4 AMR exome AF: 0.0000224

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152172 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74330

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.0000654

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000147

Gnomad4 OTH AF: 0.00

Bravo AF: 0.0000113

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:10 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Long QT syndrome 1 Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Johns Hopkins Genomics, Johns Hopkins University	Nov 27, 2022	This KCNQ1 variant (rs199472696) is rare (<0.1%) in a large population dataset (gnomAD: 1/249462 total alleles; 0.0004%; no homozygotes) and has been reported in ClinVar5. This variant has been reported in the literature in multiple unrelated individuals affected with long QT syndrome. Alterations of the same codon have also been reported in individuals with LQT1. Experimental studies have shown that this amino acid substitution (p.Arg174Cys) adversely affects KCNQ1 channel function. Bioinformatic analysis predicts that this missense variant would not affect normal exon 3 splicing, although this has not been confirmed experimentally to our knowledge. We consider c.520C>T to be pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Feb 01, 2016	Variant summary: The c.520C>T (p.R174C) in KCNQ1 gene is a missense variant that involves a conserved nucleotide and 5/5 in silico tools predict deleterious outcome. The variant is present in the control population dataset of ExAC at a low frequency (0.0008%) which does not exceed the maximum allele frequency for a pathogenic KCNQ1 variant (0.01%). This variant has been reported in the literature in multiple affected individuals presented with elongated QTc interval, including one homozygous pt with severe arrhythmic presentation. Other alterations of the same codon, p.R174H, p.R174L and p.R174P have been reported in pts with LQTS. Functional studies showed p.R174C alters the normal channel activity. In addition, several reputable databases/clinical laboratories classified the variant as Pathogenic. Therefore, this variant was classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Molecular Genetics Laboratory - Cardiogenetics, CHU de Nantes	Aug 01, 2023	- -

not provided Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Dec 14, 2021	Not observed at significant frequency in large population cohorts (Lek et al., 2016); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Published in vitro functional studies demonstrate a damaging effect as the p.(R174C) variant impairs potassium channel regulation and function (Chouabe et al., 1997; Matavel et al., 2010; Wu et al., 2018); Reported in ClinVar as a pathogenic variant (ClinVar Variant ID# 53058; Landrum et al., 2016); This variant is associated with the following publications: (PMID: 9312006, 23130128, 10973849, 15840476, 9386136, 26986070, 26907222, 29532034, 22581653, 19841300, 19716085, 19934648, 23392653, 27251404, 23728945, 26669661, 19815527, 27761162, 29037160, 29033053, 29449639, 11668638, 31737537, 32383558) -
Pathogenic, criteria provided, single submitter	clinical testing	Mayo Clinic Laboratories, Mayo Clinic	Nov 02, 2021	PP3, PM2_supporting, PM3, PS3, PS4_moderate -

Long QT syndrome Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Oct 14, 2023	This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 174 of the KCNQ1 protein (p.Arg174Cys). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This missense change has been observed in individuals with long QT syndrome (PMID: 9386136, 11668638, 15840476, 19716085, 23130128, 23392653). ClinVar contains an entry for this variant (Variation ID: 53058). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt KCNQ1 protein function. Experimental studies have shown that this missense change affects KCNQ1 function (PMID: 9312006, 19934648). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, no assertion criteria provided	clinical testing	Clinical Molecular Genetics Laboratory, Johns Hopkins All Children's Hospital	Sep 10, 2015	- -

Beckwith-Wiedemann syndrome;C1837014:Atrial fibrillation, familial, 3;C1865019:Short QT syndrome type 2;C4551509:Jervell and Lange-Nielsen syndrome 1;C4551647:Long QT syndrome 1 Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 11, 2021

- -

Cardiovascular phenotype Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 28, 2021

The p.R174C pathogenic mutation (also known as c.520C>T), located in coding exon 3 of the KCNQ1 gene, results from a C to T substitution at nucleotide position 520. The arginine at codon 174 is replaced by cysteine, an amino acid with highly dissimilar properties, and is located in the S2/S3 transmembrane-spanning region. This variant has been reported in long QT syndrome (LQTS) cohorts and LQTS genetic testing cohorts, where some cases had limited details provided (Donger C et al. Circulation. 1997;96(9):2778-81; Splawski I et al. Circulation. 2000;102(10):1178-85; Tester DJ. Heart Rhythm. 2005;2(5):507-17; Couderc JP et al. J Am Heart Assoc. 2012;1:e000570; Miyazaki et al. JACC: Clin Electrophys. 2016;(2)3:266-76; Westphal DS et al. Mol Genet Genomic Med, 2020 09;8:e1300). This variant has also been reported in the homozygous and compound heterozygous states in patients with severe LQTS presentation and Jervell and Lange-Nielsen syndrome (Giudicessi JR et al. Circ Cardiovasc Genet. 2013;6(2):193-200; Uysal F et al. BMC Med Genet. 2017 10;18:114). This variant was also detected in two siblings with LQTS who had additional co-occurring variants in other arrhythmia-related genes; family members heterozygous for p.R174C with QTc values in the normal range were also described (Wu J et al. Sci Rep, 2018 02;8:3129). Functional studies have reported this alteration to disrupt regulation of ion channel activation and lead to impaired ion channel function (Chouabe C et al. EMBO J. 1997;16(17):5472-9; Matavel A et al. Channels (Austin). 2010;4(1):3-11; Huang H et al. Sci Adv, 2018 03;4:eaar2631). Furthermore, other variants affecting this amino acid (p.R174H, p.R174P, and p.R174L) have also been reported in LQTS cohorts (Lupoglazoff JM et al. J. Am Coll Cardiol. 2004;43(5):826-30; Napolitano C et al. JAMA. 2005; 294:2975-80; Aziz PF et al. Circ Arrhythm Electrophysiol. 2011;4:867-73). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation. -

Cardiac arrhythmia Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Color Diagnostics, LLC DBA Color Health

Nov 04, 2018

This missense variant is located in the cytoplasmic linker between transmembrane domains S2 and S3 of the KCNQ1 protein. Computational prediction tools and conservation analyses suggest that this variant may have deleterious impact on the protein function. Computational splicing tools suggest that this variant may not impact RNA splicing. Experimental functional studies have shown that this variant adversely affects KCNQ1 channel function (PMID: 9312006, 19934648, 29449639). This variant has been reported in multiple unrelated individuals affected with long QT syndrome (PMID: 11668638, 23130128, 27251404, 29449639) and in individuals referred for long QT syndrome testing (PMID: 15840476, 19716085). This variant has also been reported in the homozygous and compound heterozygous state in individuals affected with Jervell and Lange-Nielsen syndrome (PMID: 23392653, 29037160). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). Based on available evidence, this variant is classified as Likely Pathogenic. -

Congenital long QT syndrome Other:1

not provided, no classification provided

literature only

Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust

-

This variant has been reported as associated with Long QT syndrome in the following publications (PMID:9386136;PMID:11668638;PMID:15840476;PMID:19716085;PMID:19934648). This is a literature report, and does not necessarily reflect the clinical interpretation of the Imperial College / Royal Brompton Cardiovascular Genetics laboratory. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
CADD	Pathogenic	33
DANN	Pathogenic	1.0
Eigen	Pathogenic	0.80
Eigen_PC	Pathogenic	0.68
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	1.0	D;D;D
M_CAP	Pathogenic	0.92	D
MetaRNN	Pathogenic	0.99	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D
PrimateAI	Pathogenic	0.84	D
PROVEAN	Pathogenic	-7.5	D;D;D
REVEL	Pathogenic	0.98
Sift	Pathogenic	0.0	D;D;D
Sift4G	Pathogenic	0.0	D;D;D
Polyphen		1.0	.;D;.
Vest4		0.90, 0.87
MutPred		0.97		.;Loss of MoRF binding (P = 0.0045);.;
MVP		0.97
MPC		1.4
ClinPred		1.0	D
GERP RS		4.4
Varity_R		0.96
gMVP		0.99

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs199472696; hg19: chr11-2591900;