rs794726799

Positions:

• chr2-166047668-G-A

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PM2 PP3_Strong PP5_Very_Strong

The NM_001353961.2(SCN1A):​c.-1297C>T variant causes a 5 prime UTR premature start codon gain change. 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 (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN1A NM_001353961.2 5_prime_UTR_premature_start_codon_gain
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:9
• Conservation: PhyloP100: 4.99

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 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 14 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: BayesDel_addAF computational evidence supports a deleterious effect, 0.625
• PP5: Variant 2-166047668-G-A is Pathogenic according to our data. Variant chr2-166047668-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 189963.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-166047668-G-A is described in Lovd as [Pathogenic]. Variant chr2-166047668-G-A is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.1129C>T	p.Arg377*	stop_gained	11/29	ENST00000674923.1	NP_001159435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.1129C>T	p.Arg377*	stop_gained	11/29		NM_001165963.4	ENSP00000501589.1
SCN1A	ENST00000303395.9	c.1129C>T	p.Arg377*	stop_gained	10/28	5		ENSP00000303540.4
SCN1A	ENST00000375405.7	c.1129C>T	p.Arg377*	stop_gained	8/26	5		ENSP00000364554.3
SCN1A	ENST00000409050.1	c.1129C>T	p.Arg377*	stop_gained	8/26	5		ENSP00000386312.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:9

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:4

Pathogenic, no assertion criteria provided	clinical testing	Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Aug 08, 2024	Nonsense variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 25525159, 17054684, 27465585, 30182498, 30321769, 26096185, 31009440, 30868114, 23808377, 30641252, 32090326, 33278787, 32427350, 31440721, 31031587, 28664031, 35074891, 36480001, 36801247) -
Pathogenic, no assertion criteria provided	clinical testing	Diagnostic Laboratory, Department of Genetics, University Medical Center Groningen	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Jul 01, 2020	- -

Severe myoclonic epilepsy in infancy Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Neuberg Centre For Genomic Medicine, NCGM	-	The stop gained variant c.1129C>T(p.Arg377Ter) in SCN1A gene has been reported previously in individuals affected with Dravet syndrome (Djémié et al., 2016). This variant has been reported to the ClinVar database as Pathogenic. The p.Arg377Ter variant is novel (not in any individuals) in gnomAD Exomes and 1000 Genomes. The nucleotide change in SCN1A is predicted as conserved by GERP++ and PhyloP across 100 vertebrates. This variant is predicted to cause loss of normal protein function through protein truncation. Loss-of-function variants in SCN1A are known to be pathogenic (Harkin et al., 2007; Depienne et al., 2009). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	research	Center for Bioinformatics, Peking University	Dec 20, 2014	- -
Pathogenic, no assertion criteria provided	clinical testing	Génétique des Maladies du Développement, Hospices Civils de Lyon	-	- -

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 13, 2023

This sequence change creates a premature translational stop signal (p.Arg377*) 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 Dravet syndrome (PMID: 17054684, 23808377, 27465585). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 189963). 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. -

Seizure Pathogenic:1

Likely pathogenic, no assertion criteria provided

clinical testing

Diagnostic Laboratory, Strasbourg University Hospital

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.62
CADD	Pathogenic	44
DANN	Uncertain	1.0
Eigen	Uncertain	0.53
Eigen_PC	Uncertain	0.38
FATHMM_MKL	Uncertain	0.95	D
Vest4		0.85, 0.84, 0.84, 0.85
GERP RS		3.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.74		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.74		Position offset: -41

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

Publications

LitVar

Other links and lift over

dbSNP: rs794726799; hg19: chr2-166904178; COSMIC: COSV57667265;