rs794726811

Variant names:

• chr2-166037942-C-A
• rs794726811
• NM_001165963.4:c.2780G>T

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5

The NM_001165963.4(SCN1A):​c.2780G>T​(p.Cys927Phe) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,886 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. C927R) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 7.90
• Publications: 2 publications found

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

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 14 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 9 uncertain in NM_001165963.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr2-166037943-A-G is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 1686149.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in the SCN1A gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 848 curated pathogenic missense variants (we use a threshold of 10). The gene has 89 curated benign missense variants. Gene score misZ: 5.2206 (above the threshold of 3.09). Trascript score misZ: 7.6022 (above the threshold of 3.09). GenCC associations: The gene is linked to familial or sporadic hemiplegic migraine, myoclonic-astatic epilepsy, arthrogryposis, Dravet syndrome, malignant migrating partial seizures of infancy, generalized epilepsy with febrile seizures plus, type 2, migraine, familial hemiplegic, 3, developmental and epileptic encephalopathy, 6A, familial hemiplegic migraine, generalized epilepsy with febrile seizures plus, genetic developmental and epileptic encephalopathy, Lennox-Gastaut syndrome.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.947
• PP5: Variant 2-166037942-C-A is Pathogenic according to our data. Variant chr2-166037942-C-A is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 189978.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001165963.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SCN1A	NM_001165963.4	MANE Select	c.2780G>T	p.Cys927Phe	missense	Exon 18 of 29	NP_001159435.1
	SCN1A	NM_001202435.3		c.2780G>T	p.Cys927Phe	missense	Exon 17 of 28	NP_001189364.1
	SCN1A	NM_001353948.2		c.2780G>T	p.Cys927Phe	missense	Exon 16 of 27	NP_001340877.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SCN1A	ENST00000674923.1	MANE Select	c.2780G>T	p.Cys927Phe	missense	Exon 18 of 29	ENSP00000501589.1
	SCN1A	ENST00000303395.9	TSL:5	c.2780G>T	p.Cys927Phe	missense	Exon 17 of 28	ENSP00000303540.4
	SCN1A	ENST00000375405.7	TSL:5	c.2747G>T	p.Cys916Phe	missense	Exon 15 of 26	ENSP00000364554.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461886 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727244

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1112006

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Developmental and epileptic encephalopathy Pathogenic:1

Jan 28, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces cysteine, which is neutral and slightly polar, with phenylalanine, which is neutral and non-polar, at codon 927 of the SCN1A protein (p.Cys927Phe). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with Dravet syndrome (PMID: 18930999, 29573403, 32090326). ClinVar contains an entry for this variant (Variation ID: 189978). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is expected to disrupt SCN1A protein function with a positive predictive value of 95%. For these reasons, this variant has been classified as Pathogenic.

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

SCN1A-related disorder Uncertain:1

Oct 18, 2022

PreventionGenetics, part of Exact Sciences

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The SCN1A c.2780G>T variant is predicted to result in the amino acid substitution p.Cys927Phe. This variant was reported in two individuals with Dravet syndrome (E-Table B, Depienne et al 2009. PubMed ID: 18930999; reported as p.Cys927Phe in Table 1, Tian et al 2018. PubMed ID: 29573403; Table S1, Brunklaus et al 2020. PubMed ID: 32090326). This variant has not been reported in a large population database (http://gnomad.broadinstitute.org), indicating this variant is rare. We suspect this variant may be pathogenic. However, at this time, the clinical significance is uncertain due to the absence of conclusive functional and genetic evidence.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.54	D
BayesDel_noAF	Pathogenic	0.54
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.98	D
Eigen	Uncertain	0.47
Eigen_PC	Uncertain	0.44
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Uncertain	0.96	D
M_CAP	Pathogenic	0.70	D
MetaRNN	Pathogenic	0.95	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.4	M
PhyloP100		7.9
PrimateAI	Uncertain	0.74	T
PROVEAN	Pathogenic	-9.6	D
REVEL	Pathogenic	0.87
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.015	D
Polyphen		0.97	D
Vest4		0.82
MutPred		0.64		Loss of ubiquitination at K922 (P = 0.1139)
MVP		0.99
MPC		3.3
ClinPred		1.0	D
GERP RS		5.2
Varity_R		0.90
gMVP		1.0
Mutation Taster		=0/100	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs794726811; hg19: chr2-166894452; COSMIC: COSV57668958; COSMIC: COSV57668958;