chr2-166002533-C-T

Variant names:

• chr2-166002533-C-T
• rs794726784
• NM_001165963.4:c.4223G>A

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_001165963.4(SCN1A):​c.4223G>A​(p.Trp1408*) variant causes a stop gained 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 Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 31)
• Consequence: SCN1A NM_001165963.4 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 7.72

Genes affected

SCN1A (HGNC:10585): (sodium voltage-gated channel alpha subunit 1) Voltage-dependent sodium channels are heteromeric complexes that regulate sodium exchange between intracellular and extracellular spaces and are essential for the generation and propagation of action potentials in muscle cells and neurons. Each sodium channel is composed of a large pore-forming, glycosylated alpha subunit and two smaller beta subunits. This gene encodes a sodium channel alpha subunit, which has four homologous domains, each of which contains six transmembrane regions. Allelic variants of this gene are associated with generalized epilepsy with febrile seizures and epileptic encephalopathy. Alternative splicing results in multiple transcript variants. The RefSeq Project has decided to create four representative RefSeq records. Three of the transcript variants are supported by experimental evidence and the fourth contains alternate 5' untranslated exons, the exact combination of which have not been experimentally confirmed for the full-length transcript. [provided by RefSeq, Oct 2015]

SCN1A-AS1 (HGNC:54069): (SCN1A and SCN9A antisense RNA 1)

LOC102724058 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 2-166002533-C-T is Pathogenic according to our data. Variant chr2-166002533-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 189947.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.4223G>A	p.Trp1408*	stop_gained	Exon 24 of 29	ENST00000674923.1	NP_001159435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.4223G>A	p.Trp1408*	stop_gained	Exon 24 of 29		NM_001165963.4	ENSP00000501589.1
SCN1A	ENST00000303395.9	c.4223G>A	p.Trp1408*	stop_gained	Exon 23 of 28	5		ENSP00000303540.4
SCN1A	ENST00000375405.7	c.4190G>A	p.Trp1397*	stop_gained	Exon 21 of 26	5		ENSP00000364554.3
SCN1A	ENST00000409050.1	c.4139G>A	p.Trp1380*	stop_gained	Exon 21 of 26	5		ENSP00000386312.1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Jan 02, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Trp1408*) in the SCN1A gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in SCN1A are known to be pathogenic (PMID: 17347258, 18930999). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with severe myoclonic epilepsy in infancy (PMID: 12566275). ClinVar contains an entry for this variant (Variation ID: 189947). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -

Generalized epilepsy with febrile seizures plus, type 2 Pathogenic:1

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Lifecell International Pvt. Ltd

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

A heterozygous nonsense variation in exon 24 of the SCN1A gene (c.4223G>A) that results in a stop codon and premature truncation of the protein at codon 1408 (p.Trp1408Ter) was detected. The observed variant is not present in both the 1000 Genomes and gnomAD databases. The reference base is conserved across the species and in-silico prediction by Mutation taster is damaging. This variant has previously been reported for Dravet Syndrome by Xu X. et al., 2015. The stop gained p.Trp1408Ter in SCN1A (NM_001165963.4) has been reported to ClinVar as Pathogenic with a status of (1 stars) criteria provided, single submitter (Variation ID 189947 as of 2020-03-05). The gene SCN1A has a low rate of benign loss of function variants as indicated by a high LoF variants Z-Score of 7.90. The p.Trp1408Ter variant is a loss of function variant in the gene SCN1A, which is intolerant of Loss of Function variants, as indicated by the presence of existing pathogenic loss of function variant NP_001159435.1:p.Met1Ile and 346 others. There are 88 downstream pathogenic loss of function variants, with the furthest variant being 518 residues downstream of the variant p.Trp1408Ter. Based on the above evidence this variant has been classified as pathogenic according to the ACMG guidelines. -

Severe myoclonic epilepsy in infancy Pathogenic:1

Dec 20, 2014

Center for Bioinformatics, Peking University

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.66
CADD	Pathogenic	42
DANN	Uncertain	0.99
Eigen	Pathogenic	0.96
Eigen_PC	Pathogenic	0.85
FATHMM_MKL	Pathogenic	0.99	D
Vest4		0.99, 0.98
GERP RS		5.4

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: rs794726784; hg19: chr2-166859043;