2-166038098-G-C

Position:

• chr2-166038098-G-C

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP2 PP3_Strong

The NM_001165963.4(SCN1A):​c.2624C>G​(p.Thr875Arg) 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 Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T875K) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 10.0

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 11 ACMG points.

• PM1: In a helix (size 11) in uniprot entity SCN1A_HUMAN there are 4 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 chr2-166038098-G-T is described in Lovd as [Likely_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, 0.976

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.2624C>G	p.Thr875Arg	missense_variant	18/29	ENST00000674923.1	NP_001159435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.2624C>G	p.Thr875Arg	missense_variant	18/29		NM_001165963.4	ENSP00000501589.1
SCN1A	ENST00000303395.9	c.2624C>G	p.Thr875Arg	missense_variant	17/28	5		ENSP00000303540.4
SCN1A	ENST00000375405.7	c.2591C>G	p.Thr864Arg	missense_variant	15/26	5		ENSP00000364554.3
SCN1A	ENST00000409050.1	c.2540C>G	p.Thr847Arg	missense_variant	15/26	5		ENSP00000386312.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 19, 2019

This sequence change replaces threonine with arginine at codon 875 of the SCN1A protein (p.Thr875Arg). The threonine residue is highly conserved and there is a moderate physicochemical difference between threonine and arginine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with SCN1A-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant disrupts the p.Thr875 amino acid residue in SCN1A. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 10742094, 12086636, 11567038, 14702334). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.57
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	.;.;.;D;.;.;D;.;.;.
Eigen	Pathogenic	0.91
Eigen_PC	Pathogenic	0.85
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Pathogenic	0.99	D;D;D;D;.;D;.;.;D;D
M_CAP	Pathogenic	0.94	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.8	.;.;.;H;.;.;H;.;.;.
PrimateAI	Pathogenic	0.91	D
PROVEAN	Pathogenic	-5.7	.;.;.;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, 0.95, 0.92
MutPred		0.87		.;Gain of MoRF binding (P = 0.0191);.;Gain of MoRF binding (P = 0.0191);.;.;Gain of MoRF binding (P = 0.0191);.;.;.;
MVP		1.0
MPC		2.8
ClinPred		1.0	D
GERP RS		4.9
Varity_R		0.96
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: rs121918623; hg19: chr2-166894608;