rs121917960

Positions:

• chr2-166002753-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PP2 PP3_Moderate PP5

The NM_001165963.4(SCN1A):​c.4003G>A​(p.Val1335Met) variant causes a missense, splice region 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. 13/23 in silico tools predict a damaging outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 31)
• Consequence: SCN1A NM_001165963.4 missense, splice_region
• Scores: Splicing: ADA: 0.9996
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1 O: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 (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a topological_domain Cytoplasmic (size 16) in uniprot entity SCN1A_HUMAN there are 5 pathogenic changes around while only 0 benign (100%) in NM_001165963.4
• PM2: Very rare variant in population databases, with high coverage
• 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, 0.93
• PP5: Variant 2-166002753-C-T is Pathogenic according to our data. Variant chr2-166002753-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 68535.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, not_provided=1, Pathogenic=2}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.4003G>A	p.Val1335Met	missense_variant, splice_region_variant	24/29	ENST00000674923.1	NP_001159435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.4003G>A	p.Val1335Met	missense_variant, splice_region_variant	24/29		NM_001165963.4	ENSP00000501589.1
SCN1A	ENST00000303395.9	c.4003G>A	p.Val1335Met	missense_variant, splice_region_variant	23/28	5		ENSP00000303540.4
SCN1A	ENST00000375405.7	c.3970G>A	p.Val1324Met	missense_variant, splice_region_variant	21/26	5		ENSP00000364554.3
SCN1A	ENST00000409050.1	c.3919G>A	p.Val1307Met	missense_variant, splice_region_variant	21/26	5		ENSP00000386312.1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1 Other:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Severe myoclonic epilepsy in infancy Pathogenic:1 Other:1

Pathogenic, criteria provided, single submitter	research	Center for Bioinformatics, Peking University	Dec 20, 2014	- -
not provided, no classification provided	literature only	UniProtKB/Swiss-Prot	-	- -

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 03, 2024

This sequence change replaces valine, which is neutral and non-polar, with methionine, which is neutral and non-polar, at codon 1335 of the SCN1A protein (p.Val1335Met). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with Dravet syndrome (PMID: 18413471, 18554359; Invitae). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 68535). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. For these reasons, this variant has been classified as Pathogenic. -

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 21, 2023

The c.4003G>A (p.V1335M) alteration is located in exon 21 (coding exon 21) of the SCN1A gene. This alteration results from a G to A substitution at nucleotide position 4003, causing the valine (V) at amino acid position 1335 to be replaced by a methionine (M). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD). This variant has been reported in individuals with features consistent with Dravet syndrome, including one de novo occurrence (Sun, 2008; Zucca, 2008; Silvennoinen, 2021). This amino acid position is highly conserved in available vertebrate species. This alteration is predicted to be deleterious by in silico analysis. Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.57
CADD	Pathogenic	31
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	.;.;D;.;.;D;.;.;.
Eigen	Pathogenic	0.93
Eigen_PC	Pathogenic	0.87
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.97	D;D;D;.;D;.;.;D;D
M_CAP	Pathogenic	0.97	D
MetaRNN	Pathogenic	0.93	D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.7	.;.;H;.;.;H;.;.;.
PrimateAI	Pathogenic	0.92	D
PROVEAN	Uncertain	-2.7	.;.;D;.;.;D;.;D;D
REVEL	Pathogenic	0.94
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		0.76, 0.82, 0.84
MutPred		0.70		.;.;Gain of MoRF binding (P = 0.0916);.;.;Gain of MoRF binding (P = 0.0916);.;.;.;
MVP		0.99
MPC		1.8
ClinPred		1.0	D
GERP RS		5.3
Varity_R		0.71
gMVP		0.95

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.13		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: rs121917960; hg19: chr2-166859263;