chr2-166037885-C-T

Position:

• chr2-166037885-C-T

Variant summary

Our verdict is Pathogenic. Variant got 21 ACMG points: 21P and 0B. PS1_Moderate PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_001165963.4(SCN1A):​c.2837G>A​(p.Arg946His) 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. 13/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another nucleotide change resulting in same amino acid change has been previously reported as Likely pathogenicin UniProt. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R946S) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:12 O:2
• 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 21 ACMG points.

• PS1: Transcript NM_001165963.4 (SCN1A) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in UniProt
• PM1: In a hotspot region, there are 13 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 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 chr2-166037886-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 68604.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• 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, 0.962
• PP5: Variant 2-166037885-C-T is Pathogenic according to our data. Variant chr2-166037885-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 68523.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-166037885-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SCN1A	NM_001165963.4	c.2837G>A	p.Arg946His	missense_variant	18/29	ENST00000674923.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SCN1A	ENST00000674923.1	c.2837G>A	p.Arg946His	missense_variant	18/29		NM_001165963.4	P4
SCN1A-AS1	ENST00000651574.1	n.487+1755C>T		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:12 Other:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:4

Pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Feb 01, 2017	- -
Pathogenic, no assertion criteria provided	clinical testing	Genome Diagnostics Laboratory, University Medical Center Utrecht	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Apr 13, 2022	Published functional studies suggest that R946H results in complete loss of function of the Nav1.1 protein (Liao et al., 2010; Volkers et al., 2011); Not observed in large population cohorts (gnomAD); Missense variants in this gene are often considered pathogenic (HGMD); This substitution is predicted to be within the pore forming loop between the S5 and S6 transmembrane segments of the second homologous domain; This variant is associated with the following publications: (PMID: 15508916, 18930999, 15277629, 16713920, 17347258, 16713913, 21371021, 17166794, 20550552, 14738421, 23195492, 21864321, 27781031, 19589774, 28492532, 15944908, 31780880, 32090326, 33851778) -
Pathogenic, no assertion criteria provided	clinical testing	Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+	-	- -

Severe myoclonic epilepsy in infancy Pathogenic:2 Other:2

Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Sep 16, 2016	Variant summary: The SCN1A c.2837G>A (p.Arg946His) variant involves the alteration of a conserved nucleotide and results in a replacement of a large size and basic Arginine (R) with a medium size and polar Histidine (H) located in the in the pore loop region of the SCN1A gene. 4/4 in silico tools predict a damaging outcome for this substitution (SNPs&GO not captured due to low reliability index). This variant is absent in 121408 control chromosomes while it was reported in several Dravet Syndrome patients, some of whom the variant arose de novo, strongly indicating causality. Moreover, independent functional studies reported the variant to result in absent measurable sodium currents, further supporting pathogenicity. In addition, mutations affecting the same codon have been described as pathogenic (c.2837G>A, p.R946P; c.2836C>A, p.R946S; c.2836C>T, p.R946C; HGMD, ClinVar) underscoring the functional/clinical importance of the R946 residue and indicating the variant to be located in a mutation hotspot. Furthermore, a clinical diagnostic laboratory classified this variant as pathogenic. Taken together, this variant is classified as pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Jun 26, 2015	- -
not provided, no classification provided	literature only	UniProtKB/Swiss-Prot	-	- -
not provided, no classification provided	literature only	Channelopathy-Associated Epilepsy Research Center	-	- -

Developmental and epileptic encephalopathy 6B Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Institute of Human Genetics, University of Leipzig Medical Center	Aug 23, 2024	Criteria applied: PS3,PS4,PM1,PM2,PM5,PP3_MOD -
Pathogenic, criteria provided, single submitter	clinical testing	Breakthrough Genomics, Breakthrough Genomics	Nov 22, 2021	This variant (also known as R936H in the literature) was previously reported in several individuals with SCN1A-related epilepsy [PMID: 21864321, 27781031, 23195492, 21371021]. Functional studies have suggested that this variant results in complete loss of SCN1A function in cell culture [PMID: 21864321, 20550552]. In addition, missense variants affecting the same codon of the identified variant (p.R946S; p.R946C) have been reported to be pathogenic [PMID: 21864321, 14738421, 15944908]. -

Inborn genetic diseases Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 14, 2017

The p.R946H variant (also known as c.2837G>A), located in coding exon 15 of the SCN1A gene, results from a G to A substitution at nucleotide position 2837. The arginine at codon 946 is replaced by histidine, an amino acid with highly similar properties. This variant was identified in multiple individuals with seizure disorders, including Dravet syndrome, severe myoclonic epilepsy in infancy, and generalized epilepsy with febrile seizures plus (GEFS+), occurring both de novo as well as inherited (Harkin LA et al. Brain, 2007 Mar;130:843-52; Depienne C et al. J. Med. Genet., 2009 Mar;46:183-91; Liao WP et al. Epilepsia, 2010 Sep;51:1669-78; Zuberi SM et al. Neurology, 2011 Feb;76:594-600; Verbeek NE et al. Epilepsia, 2011 Apr;52:e23-5; Volkers L et al. Eur. J. Neurosci., 2011 Oct;34:1268-75; Wang JW et al. Epilepsy Res., 2012 Dec;102:195-200; Møller RS et al. Mol Syndromol, 2016 Sep;7:210-219). In addition, when transfected into tsA201 cells, this variant demonstrated no measurable sodium currents when expressed heterologously with the recombinant human accessory sodium channel subunits β1 and β2 (Liao WP et al. Epilepsia, 2010 Sep;51:1669-78; Volkers L et al. Eur. J. Neurosci., 2011 Oct;34:1268-75). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 16, 2023

This sequence change replaces arginine, which is basic and polar, with histidine, which is basic and polar, at codon 946 of the SCN1A protein (p.Arg946His). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with SCN1A-related epilepsy (PMID: 14738421, 19589774, 20550552, 21371021, 21864321, 23195492, 27781031). In at least one individual the variant was observed to be de novo. This variant is also known as R936H. ClinVar contains an entry for this variant (Variation ID: 68523). 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. Experimental studies have shown that this missense change affects SCN1A function (PMID: 20550552, 21864321). This variant disrupts the p.Arg946 amino acid residue in SCN1A. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 14738421, 21864321). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

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

Pathogenic, criteria provided, single submitter

clinical testing

Génétique des Maladies du Développement, Hospices Civils de Lyon

Aug 22, 2018

- -

Seizure Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Génétique des Maladies du Développement, Hospices Civils de Lyon

Nov 10, 2020

Missense variant predicted pathogenic by bioinformatic scores. Absent from gnomAD but recurrent in the literature. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	32
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.99	.;.;.;D;.;.;D;.;.;.
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.91
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Pathogenic	0.99	D;D;D;D;.;D;.;.;D;D
M_CAP	Pathogenic	0.94	D
MetaRNN	Pathogenic	0.96	D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	4.4	.;.;.;H;.;.;H;.;.;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.90	D
PROVEAN	Pathogenic	-4.8	.;.;.;D;.;.;D;.;D;D
REVEL	Pathogenic	0.99
Sift	Pathogenic	0.0	.;.;.;D;.;.;D;.;D;D
Sift4G	Pathogenic	0.0	.;.;.;D;.;.;D;.;D;D
Polyphen		1.0, 1.0	.;.;.;D;D;.;D;D;D;.
Vest4		0.96, 0.98, 0.97, 0.97
MutPred		0.80		.;Gain of sheet (P = 0.1208);.;Gain of sheet (P = 0.1208);.;.;Gain of sheet (P = 0.1208);.;.;.;
MVP		1.0
MPC		3.0
ClinPred		1.0	D
GERP RS		5.2
Varity_R		0.96
gMVP		0.99

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: rs121917971; hg19: chr2-166894395;