rs199473263

Positions:

• chr3-38555705-A-G

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1 PM2 PP2 PP3_Strong PP5

The NM_001099404.2(SCN5A):​c.4493T>C​(p.Met1498Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M1498V) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 31)
• Consequence: SCN5A NM_001099404.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:2 O:1
• Conservation: PhyloP100: 9.27

Genes affected

SCN5A (HGNC:10593): (sodium voltage-gated channel alpha subunit 5) The protein encoded by this gene is an integral membrane protein and tetrodotoxin-resistant voltage-gated sodium channel subunit. This protein is found primarily in cardiac muscle and is responsible for the initial upstroke of the action potential in an electrocardiogram. Defects in this gene have been associated with long QT syndrome type 3 (LQT3), atrial fibrillation, cardiomyopathy, and Brugada syndrome 1, all autosomal dominant cardiac diseases. Alternative splicing results in several transcript variants encoding different isoforms. [provided by RefSeq, May 2022]

ACMG classification

Verdict is Pathogenic. Variant got 10 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 9 uncertain in NM_001099404.2
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, SCN5A
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.962
• PP5: Variant 3-38555705-A-G is Pathogenic according to our data. Variant chr3-38555705-A-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 67902.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=2, not_provided=1, Likely_pathogenic=1}. Variant chr3-38555705-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SCN5A	NM_001099404.2	c.4493T>C	p.Met1498Thr	missense_variant	26/28	ENST00000413689.6
SCN5A	NM_000335.5	c.4490T>C	p.Met1497Thr	missense_variant	26/28	ENST00000423572.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SCN5A	ENST00000413689.6	c.4493T>C	p.Met1498Thr	missense_variant	26/28	5	NM_001099404.2	P4
SCN5A	ENST00000423572.7	c.4490T>C	p.Met1497Thr	missense_variant	26/28	1	NM_000335.5	A1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:2 Other:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	May 03, 2019	This variant identified in the SCN5A gene is located in the interdomain linker DIII/DIV region of the resulting protein (PMID: 25348405). For more information about the location of this variant, please visit www.invitae.com/SCN5A-topology. It is unclear how this variant impacts the function of this protein. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C65"). This variant has been reported in the literature in an individual referred for long QT syndrome genetic testing (PMID: 16414944).   ClinVar contains an entry for this variant (Variation ID: 67902). This variant is not present in population databases (ExAC no frequency). This sequence change replaces methionine with threonine at codon 1498 of the SCN5A protein (p.Met1498Thr). The methionine residue is highly conserved and there is a moderate physicochemical difference between methionine and threonine. -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	May 17, 2022	Reported in patients with LQTS in published literature; however detailed clinical information was not provided (Riuro et al., 2015; Napolitano et al., 2005); Not observed at significant frequency in large population cohorts (gnomAD); 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: 32268277, 23840796, 23663249, 26467377, 24667783, 16414944) -

Cardiovascular phenotype Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 10, 2019

The p.M1498T variant (also known as c.4493T>C), located in coding exon 25 of the SCN5A gene, results from a T to C substitution at nucleotide position 4493. The methionine at codon 1498 is replaced by threonine, an amino acid with similar properties located in the cytoplasmic region linking transmembrane protein domains III and IV. This variant was previously described in a patient with long QT syndrome (Napolitano C et al. JAMA. 2005;294(23):2975-80). Additionally, other alterations involving the same amino acid position (p.M1498V c.4492A>G; p.M198R c.4493T>G) have been observed either in a patient from a study of long QT syndrome clinical genetic testing or in a family with sick sinus syndrome (Kapplinger JD et al. Heart Rhythm. 2009;6(9):1297-303; Asadi M et al. Anatol J Cardiol, 2016 Mar;16:170-4). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is likely to be 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:16414944). 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	0.99
CardioboostCm	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.57
CADD	Uncertain	26
DANN	Uncertain	0.97
Eigen	Pathogenic	0.83
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Pathogenic	0.98	D
M_CAP	Pathogenic	0.73	D
MetaRNN	Pathogenic	0.96	D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D;D;D;D;D;D;D;D;D
PrimateAI	Pathogenic	0.95	D
PROVEAN	Pathogenic	-5.5	D;D;D;D;D;D;D;D;D
REVEL	Pathogenic	0.95
Sift	Uncertain	0.0020	D;D;D;D;D;D;D;D;D
Sift4G	Pathogenic	0.0	D;D;D;D;D;D;D;D;D
Polyphen		0.99	D;B;.;D;.;D;D;.;.
Vest4		0.94
MutPred		0.84		.;.;Loss of stability (P = 0.014);.;.;Loss of stability (P = 0.014);.;.;.;
MVP		0.97
MPC		1.5
ClinPred		1.0	D
GERP RS		4.5
Varity_R		0.91
gMVP		0.96

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: rs199473263; hg19: chr3-38597196;