3-38560404-C-T

Variant names:

• chr3-38560404-C-T
• rs199473224
• NM_001099404.2:c.3988G>A

Variant summary

Our verdict is Pathogenic. Variant got 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_000335.5(SCN5A):​c.3985G>A​(p.Ala1329Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000684 in 1,460,924 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 13/22 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. A1329P) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000068 (0 hom.)
• Consequence: SCN5A NM_000335.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3 U:1 O:2
• Conservation: PhyloP100: 7.83

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 19 ACMG points.

• PM1: In a helix (size 11) in uniprot entity SCN5A_HUMAN there are 7 pathogenic changes around while only 0 benign (100%) in NM_000335.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-38560404-C-G is described in Lovd as [Pathogenic].
• PP2: Missense variant in the SCN5A gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 99 curated pathogenic missense variants (we use a threshold of 10). The gene has 60 curated benign missense variants. Gene score misZ: 2.7504 (below the threshold of 3.09). Trascript score misZ: 4.8279 (above the threshold of 3.09). GenCC associations: The gene is linked to progressive familial heart block, type 1A, Brugada syndrome, familial sick sinus syndrome, short QT syndrome, paroxysmal familial ventricular fibrillation, progressive familial heart block, long QT syndrome 3, familial atrial fibrillation, catecholaminergic polymorphic ventricular tachycardia, dilated cardiomyopathy, dilated cardiomyopathy 1E, arrhythmogenic right ventricular cardiomyopathy, Brugada syndrome 1, atrial standstill, familial isolated dilated cardiomyopathy, familial long QT syndrome, sick sinus syndrome 1.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.986
• PP5: Variant 3-38560404-C-T is Pathogenic according to our data. Variant chr3-38560404-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 67842.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr3-38560404-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN5A	NM_001099404.2	c.3988G>A	p.Ala1330Thr	missense_variant	Exon 23 of 28	ENST00000413689.6	NP_001092874.1
SCN5A	NM_000335.5	c.3985G>A	p.Ala1329Thr	missense_variant	Exon 23 of 28	ENST00000423572.7	NP_000326.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN5A	ENST00000413689.6	c.3988G>A	p.Ala1330Thr	missense_variant	Exon 23 of 28	5	NM_001099404.2	ENSP00000410257.1
SCN5A	ENST00000423572.7	c.3985G>A	p.Ala1329Thr	missense_variant	Exon 23 of 28	1	NM_000335.5	ENSP00000398266.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000684 AC: 10 AN: 1460924 Hom.: 0 Cov.: 32 AF XY: 0.00000826 AC XY: 6 AN XY: 726738

Gnomad4 AFR exome AF: 0.0000299

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000101

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000360

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3 Uncertain:1 Other:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:2

Feb 03, 2022

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); Published functional studies demonstrated that A1330T induces a positive shift in the voltage-dependence of steady-state inactivation and accelerates recovery from inactivation likely resulting in delayed repolarization (Smits et al., 2005).; In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Reported in ClinVar as likely pathogenic but additional evidence is not available (ClinVar Variant ID# 67842; ClinVar); This variant is associated with the following publications: (PMID: 19841300, 12566525, 17854786, 16039271, 28118183, 29654130, 31317183, 11535573, 30193851, 33087929, 33164571) -

Sep 29, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 1330 of the SCN5A protein (p.Ala1330Thr). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with long QT syndrome (PMID: 16039271). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 67842). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. Experimental studies have shown that this missense change affects SCN5A function (PMID: 16039271). This variant disrupts the p.Ala1330 amino acid residue in SCN5A. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 11535573). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

Cardiovascular phenotype Pathogenic:1 Uncertain:1

Nov 05, 2021

Ambry Genetics

Significance: Uncertain significance

Review Status: flagged submission

Collection Method: clinical testing

The c.3988G>A (p.A1330T) alteration is located in exon 23 (coding exon 22) of the SCN5A gene. This alteration results from a G to A substitution at nucleotide position 3988, causing the alanine (A) at amino acid position 1330 to be replaced by a threonine (T). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Sep 06, 2016

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: The SCN5A c.3988G>A (p.Ala1330Thr) variant involves the alteration of a conserved nucleotide. 4/4 in silico tools predict a damaging outcome for this variant (SNPs&GO not captured due to low reliability index). This variant is absent in 120776 control chromosomes. This variant has been reported in one LQTS family with co-segregation in 5 affected members (Smits_2005). No additional patient who carries this variant has been reported so far. In vitro study showed this variant shifts the voltage range of I(Na, window) activity to more positive potentials. Here the counter-acting effect of outward K+ current is reduced and may delay AP repolarization, explaining the LQT3 phenotype (Smits_2005). However, the magnitude of the electrophysiological findings reported by the authors does not seem dramatically different from those of the wild-type controls as compared to the other pathogenic variant (p.A1330P) which is known to be associated with LQT3. Nevertheless, the authors interpret their findings as an increased persistent inward current caused by this variant. In addition, multiple clinical diagnostic laboratories/reputable databases classified this variant as pathogenic. Taken together, this variant is classified as likely pathogenic until additional functional studies and co-segregation of this variant in other patients/families with LQT3 are obtained. -

SCN5A-related disorder Other:1

-

GenomeConnect, ClinGen

Significance: not provided

Review Status: no classification provided

Collection Method: phenotyping only

GenomeConnect assertions are reported exactly as they appear on the patient-provided report from the testing laboratory. GenomeConnect staff make no attempt to reinterpret the clinical significance of the variant. -

Congenital long QT syndrome Other:1

-

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

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

This variant has been reported as associated with Long QT syndrome in the following publications (PMID:12566525;PMID:19841300). 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	0.95
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	30
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.96	.;.;.;.;.;D;.;.;.
Eigen	Pathogenic	0.82
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.96	.;D;D;D;D;D;D;.;D
M_CAP	Pathogenic	0.76	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.1	.;.;.;.;.;M;.;.;.
PrimateAI	Pathogenic	0.86	D
PROVEAN	Uncertain	-3.9	D;D;D;D;D;D;D;D;D
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	D;D;D;D;D;D;D;D;D
Sift4G	Benign	0.081	T;T;T;T;T;T;T;T;T
Polyphen		1.0	D;D;.;D;.;D;D;.;.
Vest4		0.98
MutPred		0.92		Gain of glycosylation at A1330 (P = 0.295);.;Gain of glycosylation at A1330 (P = 0.295);Gain of glycosylation at A1330 (P = 0.295);.;Gain of glycosylation at A1330 (P = 0.295);.;.;.;
MVP		0.99
MPC		1.4
ClinPred		1.0	D
GERP RS		4.1
Varity_R		0.84
gMVP		0.98

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: rs199473224; hg19: chr3-38601895; COSMIC: COSV61116764;