2-165992341-C-T

Position:

• chr2-165992341-C-T

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_001165963.4(SCN1A):​c.4934G>A​(p.Arg1645Gln) variant causes a missense 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. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R1645G) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:7 O:1
• Conservation: PhyloP100: 7.77

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 19 ACMG points.

• PM1: In a transmembrane_region Helical; Name=S4 of repeat IV (size 16) in uniprot entity SCN1A_HUMAN there are 10 pathogenic changes around while only 0 benign (100%) 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 chr2-165992342-G-C is described in Lovd as [Pathogenic].
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), SCN1A. . Gene score misZ 5.2206 (greater than the threshold 3.09). Trascript score misZ 7.6022 (greater than threshold 3.09). GenCC has associacion of gene with migraine, familial hemiplegic, 3, familial hemiplegic migraine, Dravet syndrome, malignant migrating partial seizures of infancy, generalized epilepsy with febrile seizures plus, myoclonic-astatic epilepsy, developmental and epileptic encephalopathy, developmental and epileptic encephalopathy, 6, familial or sporadic hemiplegic migraine, arthrogryposis, Lennox-Gastaut syndrome, generalized epilepsy with febrile seizures plus, type 2.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.974
• PP5: Variant 2-165992341-C-T is Pathogenic according to our data. Variant chr2-165992341-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 68558.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.4934G>A	p.Arg1645Gln	missense_variant	29/29	ENST00000674923.1	NP_001159435.1
LOC102724058	NR_110598.1	n.176-23272C>T		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.4934G>A	p.Arg1645Gln	missense_variant	29/29		NM_001165963.4	ENSP00000501589	P4
SCN1A-AS1	ENST00000651574.1	n.193-23272C>T		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:7 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Severe myoclonic epilepsy in infancy Pathogenic:2 Other:1

not provided, no classification provided	literature only	UniProtKB/Swiss-Prot	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	Neurogenetics Laboratory - MEYER, AOU Meyer	Nov 16, 2016	- -
Pathogenic, criteria provided, single submitter	clinical testing	Neuberg Centre For Genomic Medicine, NCGM	-	The missense variant p.R1645Q in SCN1A (NM_001165963.4) has ben previously reported in multiple patients with Dravet syndrome including one where it was confirmed to be de novo (Harkin LA et al; Parrini E et al). The variant has been submitted to ClinVar as Pathogenic.The missense variant c.4934G>A (p.R1645Q) in SCN1A (NM_001165963.4) is not observed in the large population cohorts of the gnomAD and 1000 Genomes datasets (Exome Aggregation Consortium et al., 2016; 1000 Genomes Consortium et al., 2015). The p.R1645Q missense variant is predicted to be damaging by both SIFT and PolyPhen2. The arginine residue at codon 1645 of SCN1A is conserved in all mammalian species. The nucleotide c.4934 in SCN1A is predicted conserved by GERP++ and PhyloP across 100 vertebrates. For these reasons, this variant has been classified as Pathogenic. -

Migraine, familial hemiplegic, 3 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Centre for Mendelian Genomics, University Medical Centre Ljubljana

Nov 28, 2018

This variant was classified as: Pathogenic. The following ACMG criteria were applied in classifying this variant: PM1,PP2,PP3,PS1. -

Inborn genetic diseases Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

May 06, 2016

The p.R1645Q pathogenic mutation (also known as c.4934G>A), located in coding exon 26 of the SCN1A gene, results from a G to A substitution at nucleotide position 4934. The arginine at codon 1645 is replaced by glutamine, an amino acid with highly similar properties. This alteration has been reported in the literature as de novo in two individuals with the SCN1A-related seizure disorder, Dravet syndrome (Harkin LA, Brain 2007; 130:843-52; Heron SE, J. Med. Genet. 2010; 47(2):137-41; Bolszak M, Epilepsy Res. 2009; 85(2-3):300-4). The position R1645 corresponds to a well-defined arginine (R3) in the voltage sensing motif known to play a significant role in gating function (DeCoursey TE. Physiol Rev. 2013;93(2):599-652). Based on the supporting evidence this alteration is interpreted as a disease-causing mutation. -

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 30, 2023

For these reasons, this variant has been classified as Pathogenic. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt SCN1A protein function. ClinVar contains an entry for this variant (Variation ID: 68558). This missense change has been observed in individual(s) with Dravet syndrome (PMID: 17347258, 27864847). In at least one individual the variant was observed to be de novo. This variant is present in population databases (rs121917976, gnomAD 0.0009%). This sequence change replaces arginine, which is basic and polar, with glutamine, which is neutral and polar, at codon 1645 of the SCN1A protein (p.Arg1645Gln). -

Severe myoclonic epilepsy in infancy;C1858673:Generalized epilepsy with febrile seizures plus, type 2;C1864987:Migraine, familial hemiplegic, 3 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 31, 2018

- -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Jul 06, 2020

Not observed at a significant frequency in large population cohorts (Lek et al., 2016); Missense variants in this gene are often considered pathogenic (Stenson et al., 2014); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 19585586, 17347258, 16713920, 19359143, 19589774, 27864847, 31134136, 31031587) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.56
CADD	Pathogenic	29
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.99	.;.;.;D;.;D;.;.;.
Eigen	Pathogenic	0.98
Eigen_PC	Pathogenic	0.90
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.94	D;D;D;D;.;.;.;D;D
M_CAP	Pathogenic	0.99	D
MetaRNN	Pathogenic	0.97	D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.99	D
MutationAssessor	Pathogenic	4.6	.;.;.;H;.;H;.;.;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.85	D
PROVEAN	Uncertain	-3.5	.;.;.;D;.;D;.;D;D
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	.;.;.;D;.;D;.;D;D
Sift4G	Uncertain	0.010	.;.;.;D;.;D;.;D;D
Polyphen		1.0	.;.;.;.;D;.;D;D;.
Vest4		0.94, 0.98, 0.97
MutPred		0.85		.;.;.;Loss of methylation at R1648 (P = 0.1221);.;Loss of methylation at R1648 (P = 0.1221);.;.;.;
MVP		1.0
MPC		1.7
ClinPred		1.0	D
GERP RS		5.3
Varity_R		0.71
gMVP		1.0

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: rs121917976; hg19: chr2-166848851; COSMIC: COSV57662283; COSMIC: COSV57662283;