11-2583544-C-T
Variant summary
Our verdict is Pathogenic. The variant received 14 ACMG points: 14P and 0B. PM1PM5PP2PP3PP5_Very_Strong
The NM_000218.3(KCNQ1):c.1031C>T(p.Ala344Val) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000056 in 1,607,638 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A344T) has been classified as Likely pathogenic.
Frequency
Consequence
NM_000218.3 missense, splice_region
Scores
Clinical Significance
Conservation
Publications
- long QT syndromeInheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
- long QT syndrome 1Inheritance: AD, AR Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P
- Jervell and Lange-Nielsen syndromeInheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
- Jervell and Lange-Nielsen syndrome 1Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: PanelApp Australia, Labcorp Genetics (formerly Invitae), G2P
- atrial fibrillation, familial, 3Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
- short QT syndromeInheritance: AD Classification: STRONG, SUPPORTIVE Submitted by: ClinGen, Orphanet
- short QT syndrome type 2Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P
- familial atrial fibrillationInheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
- Jervell and Lange-Nielsen syndromeInheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
- hypertrophic cardiomyopathyInheritance: AD Classification: NO_KNOWN Submitted by: ClinGen
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ACMG classification
Our verdict: Pathogenic. The variant received 14 ACMG points.
Variant Effect in Transcripts
ACMG analysis was done for transcript: NM_000218.3. You can select a different transcript below to see updated ACMG assignments.
RefSeq Transcripts
| Selected | Gene | Transcript | Tags | HGVSc | HGVSp | Effect | Exon Rank | Protein | UniProt |
|---|---|---|---|---|---|---|---|---|---|
| KCNQ1 | NM_000218.3 | MANE Select | c.1031C>T | p.Ala344Val | missense splice_region | Exon 7 of 16 | NP_000209.2 | ||
| KCNQ1 | NM_001406836.1 | c.1031C>T | p.Ala344Val | missense splice_region | Exon 7 of 15 | NP_001393765.1 | |||
| KCNQ1 | NM_001406837.1 | c.761C>T | p.Ala254Val | missense splice_region | Exon 8 of 17 | NP_001393766.1 |
Ensembl Transcripts
| Selected | Gene | Transcript | Tags | HGVSc | HGVSp | Effect | Exon Rank | Protein | UniProt |
|---|---|---|---|---|---|---|---|---|---|
| KCNQ1 | ENST00000155840.12 | TSL:1 MANE Select | c.1031C>T | p.Ala344Val | missense splice_region | Exon 7 of 16 | ENSP00000155840.2 | ||
| KCNQ1 | ENST00000335475.6 | TSL:1 | c.650C>T | p.Ala217Val | missense splice_region | Exon 7 of 16 | ENSP00000334497.5 | ||
| KCNQ1 | ENST00000713725.1 | c.890C>T | p.Ala297Val | missense splice_region | Exon 6 of 15 | ENSP00000519029.1 |
Frequencies
GnomAD3 genomes AF: 0.00000657 AC: 1AN: 152222Hom.: 0 Cov.: 33 show subpopulations
GnomAD4 exome AF: 0.00000550 AC: 8AN: 1455416Hom.: 0 Cov.: 30 AF XY: 0.00000414 AC XY: 3AN XY: 724372 show subpopulations
Age Distribution
GnomAD4 genome AF: 0.00000657 AC: 1AN: 152222Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0AN XY: 74362 show subpopulations
ClinVar
Submissions by phenotype
Long QT syndrome 1 Pathogenic:4
The c.1031C>T variant in KCNQ1 has previously been reported in individuals with long QT syndrome (PMID: 9386136, 28944242, 31737537, 34505893) and it has been deposited in ClinVar [ClinVar ID: 52936] as Pathogenic by multiple submitters with affected status provided. The c.1031C>T variant is observed in 1 allele (~0.00017% minor allele frequency with 0 homozygote) in population databases (gnomAD v2.1.1 and v3.1.2, TOPMed Freeze 8, All of Us), suggesting it is not a common benign variant in the populations represented in those databases. The c.1031C>T variant in KCNQ1 is located in exon 7 of this 16-exon gene and is predicted to replace an evolutionarily conserved alanine amino acid with valine at position 344 (p.(Ala344Val) in the ion transport domain of the encoded protein [UniProt ID: P51787]. Functional studies demonstrated loss of potassium channel function (PMID: 34505893). Different missense variants affecting the same aminoacid residue (p.Ala344) and neighbouring residues within the S segment have been reported in individuals with long QT syndrome in the literature [PMID: 28349240]. Based on available evidence this c.1031C>T p.(Ala344Val) variant identified in KCNQ1 is classified as Pathogenic.
Based on the classification scheme VCGS_Germline_v1.1.1, this variant is classified as Pathogenic. Following criteria are met: 0103 - Both loss- and gain-of-function are known mechanisms of disease for this gene (PMID: 19632626). (N) 0104 - Dominant Negative is a mechanism of disease for this gene. Long QT syndrome has been associated with variants resulting in both loss-of-function and dominant negative effects (PMID: 19632626). (N) 0108 - This gene is known to be associated with both recessive and dominant disease. Long QT syndrome is caused predominantly by heterozygous pathogenic variants (OMIM). (N) 0200 - Variant is predicted to result in a missense amino acid change from an alanine to a valine (exon 7). (N) 0251 - Variant is heterozygous. (N) 0302 - Variant is present in gnomAD <0.001 for a dominant condition (1 heterozygote, 0 homozygotes). (P) 0502 - Missense variant with conflicting in silico predictions and uninformative conservation. (N) 0600 - Variant is located in an annotated domain or motif (S6 transmembrane helix of the ion transport domain; NCBI, PDB, Decipher, PMID: 10508236). (N) 0703 - Comparable variants have moderate previous evidence for pathogenicity. At least two different variants in the same codon resulting in a change to a threonine and a glycine have been reported as likely pathogenic (ClinVar). (P) 0801 - Strong previous evidence of pathogenicity in unrelated individuals. This variant has been has described as a mild variant and has been previously reported as pathogenic in multiple patients with long QT syndrome (ClinVar, LOVD, PMID: 10508236, PMID: 28944242). (P) 1002 - Moderate functional evidence supporting abnormal protein function. Studies show that this variant induces voltage-dependent inactivation in KCNQ1 channels and shifts the voltage dependence of KCNQ1/KCNE1 complex activation (PMID: 16931984). (P) 1208 - Inheritance information for this variant is not currently available. (N) Legend: (P) - Pathogenic, (N) - Neutral, (B) - Benign
Long QT syndrome Pathogenic:4
Variant summary: KCNQ1 c.1031C>T (p.Ala344Val) results in a non-conservative amino acid change in the Ion transport domain (IPR005821) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. Several computational tools predict a significant impact on normal splicing: Three predict the variant weakens the canonical 5' donor site. One predict the variant creates the canonical 5' donor site. However, these predictions have yet to be confirmed by functional studies. The variant was absent in 251186 control chromosomes. c.1031C>T has been observed at a heterozygous state in multiple families affected with long QT syndrome 1 (examples, Donger_1997 and Schwartz_2021) and at a homozygous state in at least three individuals affected with severe long QT syndrome without hearing loss (example, Al-Hassnan_2017). In the families with homozygous affected, the variant was also observed at a heterozygous state in 7 family members including consanguineous parents, who reported no severe arrhythmic events such as syncope, but the QTC intervals appeared to be prolonged (Al-Hassnan_2017). These data indicate that the variant is very likely to be associated with disease. c.1031C>T has also been observed in multiple unaffected heterozygous individuals (Schwartz_2021), suggesting a reduced penetrance for long QT syndrome. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect results in a voltage-dependent inactivation of the macroscopic current in X. Oocytes and CHO cells (Siebrands_2006). The following publications have been ascertained in the context of this evaluation (PMID: 28438721, 9386136, 34505893, 16931984). ClinVar contains an entry for this variant (Variation ID: 52936). Based on the evidence outlined above, the variant was classified as pathogenic.
Criteria: PS4_Strong, PS3_Moderate, PM1, PM2, PP3
This variant has been reported in multiple individuals with long QT syndrome (PMID: 9386136, 15466642, 15840476, 19716085, 9570196, 17470695, 32893267, 36102233). This variant is absent from large population databases, including the Genome Aggregation Database (http://gnomad.broadinstitute.org/). This variant is located in a well-established functional domain of the protein where other pathogenic or likely pathogenic variants have been described (PMID: 19716085). It is predicted to be deleterious by in silico analysis. Functional studies suggest that this variant results in a deleterious effect on the protein (PMID: 16931984).
This sequence change replaces alanine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 344 of the KCNQ1 protein (p.Ala344Val). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with long QT syndrome (PMID: 9386136, 16922724, 17088455, 17470695, 19490272, 24217263). ClinVar contains an entry for this variant (Variation ID: 52936). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed for this missense variant. However, the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on KCNQ1 protein function. Experimental studies have shown that this missense change affects KCNQ1 function (PMID: 16931984). For these reasons, this variant has been classified as Pathogenic.
not provided Pathogenic:3
Note this variant was found in clinical genetic testing performed by one or more labs who may also submit to ClinVar. Thus any internal case data may overlap with the internal case data of other labs. The interpretation reviewed below is that of the Stanford Center for Inherited Cardiovascular Disease. KCNQ1 p.Ala344Val This variant has been published in multiple cases of long QT syndrome. Donger et al (1997) reported the variant in 6 members of one family with long QT syndrome. It’s not clear how many of those family members actually had clinically diagnosed long QT. The average QTc among those family members was 471 ms (+/-32) and 2 of the 6 carriers were symptomatic (syncope). Tester et al (2005) reported the variant in three cases of long QT syndrome referred to Mayo Clinic’s Sudden Death Genomics Laboratory for genetic testing. In a study on genotype-phenotype correlations, Moss et al (2007) reported 17 individuals with this variant, though it is not clear if they all had a clinical diagnosis of long QT syndrome. Another missense variant at the same codon has been reported in someone with long QT syndrome: p.Ala344Glu (Tester et al 2005). Tester et al (2005) did not see the variant in more than 750 control individuals of varied ancestry. Donger et al (1997) did not observe the variant in 100 control subjects, for a total of 1050 control individuals. As of Oct 2013: It is not present in the NHLBI Exome Sequencing Project dataset of approximately 6500 individuals of Caucasian and African American ancestry. Based on these data it is very likely that this variant causes long QT syndrome and that the risk of cardiac events is increased because of the location of this variant. It affects a highly conserved amino acid residue in an important functional domain of the protein: the S6 transmembrane domain. Of note, variants like this one that are located in the transmembrane region of the channel are correlated with a higher risk of cardiac events (hazard ratio 2.06), independent of traditional clinical risk factors such as age, gender, and QTc length (Moss et al 2007).
Not observed in large population cohorts (gnomAD); Published functional studies demonstrate a damaging effect on KCNQ1 channel function (Siebrands et al., 2006); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 15840476, 19716085, 29444113, 16931984, 12388934, 22095730, 15466642, 9386136, 17470695, 28944242, 9570196, 29033053, 31589614, 28438721, 31737537, 34505893)
PP3, PM2, PS3, PS4
Cardiovascular phenotype Pathogenic:1
The p.A344V pathogenic mutation (also known as c.1031C>T), located in coding exon 7 of the KCNQ1 gene, results from a C to T substitution at nucleotide position 1031. The alanine at codon 344 is replaced by valine, an amino acid with similar properties. This variant was reported in individual(s) with features consistent with long QT syndrome (LQTS) (Donger C et al. Circulation. 1997;96(9):2778-81; Choi G et al. Circulation. 2004;110(15):2119-24; Shimizu W et al. J. Am. Coll. Cardiol. 2004;44:117-25; Tester DJ et al. Heart Rhythm. 2005;2(5):507-17; Millat G et al. Clin. Genet. 2006;70(3):214-27; Moss AJ et al. Circulation. 2007;115(19):2481-9; Kapplinger JD et al. Heart Rhythm. 2009;6(9):1297-303; Schwartz PJ et al. Eur Heart J. 2021 12;42(46):4743-4755). This variant has also been detected in the homozygous state in several individuals with severe LQTS phenotypes reminiscent recessive Jervell and Lange-Nielsen syndrome (JLNS), but without hearing loss (Al-Hassnan ZN et al. Heart Rhythm. 2017;epub; Bdier AT et al. Mol Gen & Gen Med. 2017:epub). Asymptomatic heterozygous carriers of this variant have also been detected, suggesting it may result in a mild phenotype and/or exhibit reduced penetrance in the heterozygous state in some cases (Al-Hassnan ZN et al. Heart Rhythm. 2017;epub; Schwartz PJ et al. Eur Heart J. 2021 12;42(46):4743-4755). In multiple assays testing KCNQ1 function, this variant showed functionally abnormal results (Siebrands CC et al. Anesthesiology. 2006 Sep;105(3):511-20; Heijman J et al. Circ. Res. 2012 Jan;110(2):211-9; Schwartz PJ et al. Eur Heart J. 2021 12;42(46):4743-4755). Based on internal structural analysis, this variant is anticipated to disrupt a region of known function (Sun J et al. Cell. 2020 01;180(2):340-347.e9; Sun J et al. Cell. 2017 Jun;169(6):1042-1050.e9). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. 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
This missense variant replaces alanine with valine at codon 344 of the KCNQ1 protein. This variant is found within a highly conserved region in transmembrane domain S6 (a.a. 328-348). Rare non-truncating variants in this region have been shown to be significantly overrepresented in individuals with long QT syndrome (PMID: 32893267). Functional studies have shown that this variant affects gating properties and increases channel sensitivity to anesthetics (PMID: 16931984, 32015334 ). This variant has been reported in heterozygous state in over ten unrelated individuals affected with long QT syndrome (PMID: 9386136, 15840476, 19716085, 20851114, 24217263, 26669661, 27920829, 32298319, 32893267, 34505893, 34884666) and in homozygous state in at least three individuals affected with severe long QT syndrome without hearing loss (PMID: 28438721, 28944242). This variant has been report to be a de novo occurrence in a child with severe long QT syndrome in compound heterozygous state with p.Ala300Thr variant in the same gene (PMID: 34884666). This variant has also been observed in over twenty unaffected heterozygous individuals (PMID: 9386136, 28438721, 28944242, 34505893). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). Based on the available evidence, this variant is classified as Pathogenic.
Congenital long QT syndrome Other:1
This variant has been reported as associated with Long QT syndrome in the following publications (PMID:9386136;PMID:15466642;PMID:15840476;PMID:19716085;PMID:9570196;PMID:17470695). 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:
Splicing
Find out detailed SpliceAI scores and Pangolin per-transcript scores at