2-166041385-C-T

Variant names:

• chr2-166041385-C-T
• rs794726743
• NM_001165963.4:c.2261G>A

Variant summary

Our verdict is Pathogenic. Variant got 13 ACMG points: 13P and 0B. PVS1 PM2 PP3 PP5_Moderate

The NM_001165963.4(SCN1A):​c.2261G>A​(p.Trp754*) 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: 30)
• Consequence: SCN1A NM_001165963.4 stop_gained
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.90

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)

ACMG classification

Verdict is Pathogenic. Variant got 13 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
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 2-166041385-C-T is Pathogenic according to our data. Variant chr2-166041385-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 461248.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.2261G>A	p.Trp754*	stop_gained	Exon 16 of 29	ENST00000674923.1	NP_001159435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.2261G>A	p.Trp754*	stop_gained	Exon 16 of 29		NM_001165963.4	ENSP00000501589.1
SCN1A	ENST00000303395.9	c.2261G>A	p.Trp754*	stop_gained	Exon 15 of 28	5		ENSP00000303540.4
SCN1A	ENST00000375405.7	c.2228G>A	p.Trp743*	stop_gained	Exon 13 of 26	5		ENSP00000364554.3
SCN1A	ENST00000409050.1	c.2177G>A	p.Trp726*	stop_gained	Exon 13 of 26	5		ENSP00000386312.1

Frequencies

GnomAD3 genomes Cov.: 30

GnomAD4 exome Cov.: 36

GnomAD4 genome Cov.: 30

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Aug 15, 2020

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. While this particular variant has not been reported in the literature, loss-of-function variants in SCN1A are known to be pathogenic (PMID: 17347258, 18930999). This sequence change creates a premature translational stop signal at codon 754 (p.Trp754*) of the SCN1A gene. It is expected to result in an absent or disrupted protein product. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.66
CADD	Pathogenic	52
DANN	Uncertain	1.0
Eigen	Pathogenic	0.98
Eigen_PC	Pathogenic	0.88
FATHMM_MKL	Pathogenic	0.98	D
Vest4		0.96, 0.97, 0.97, 0.97
GERP RS		5.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.65		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.65		Position offset: -2

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

Publications

LitVar

Other links and lift over

dbSNP: rs794726743; hg19: chr2-166897895; COSMIC: COSV57664348; COSMIC: COSV57664348;