rs1553548096

chr2-166048906-A-Cchr2-166048906-A-T

Variant summary

Our verdict is Pathogenic. Variant got 13 ACMG points: 13P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Moderate

The NM_001165963.4(SCN1A):c.1008T>G(p.Cys336Trp) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C336Y) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 6.27

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 13 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 6 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 chr2-166048907-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 189962.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant where missense usually causes diseases, SCN1A
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.963
• PP5: Variant 2-166048906-A-C is Pathogenic according to our data. Variant chr2-166048906-A-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 461241.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SCN1A	NM_001165963.4	c.1008T>G	p.Cys336Trp	missense_variant	10/29	ENST00000674923.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SCN1A	ENST00000674923.1	c.1008T>G	p.Cys336Trp	missense_variant	10/29		NM_001165963.4	P4
SCN1A-AS1	ENST00000651574.1	n.487+12776A>C		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Invitae

Aug 21, 2017

Family studies have indicated that this variant was not present in the parents of an individual with SCN1A-related disease, which suggests that it was de novo in that affected individual (Invitae). In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. 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 identified in the SCN1A gene is located in the extracellular D1-P1 region of the resulting protein (PMID: 25348405, 18804930), but it is unclear how this variant impacts the function of this protein. This variant is not present in population databases (ExAC no frequency). This sequence change replaces cysteine with tryptophan at codon 336 of the SCN1A protein (p.Cys336Trp). The cysteine residue is highly conserved and there is a large physicochemical difference between cysteine and tryptophan. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
Cadd	Uncertain	25
Dann	Uncertain	0.99
Eigen	Pathogenic	0.93
Eigen_PC	Pathogenic	0.83
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D;D;D;D;.;D;.;.;D;D
M_CAP	Pathogenic	0.96	D
MetaRNN	Pathogenic	0.96	D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.84	D
Polyphen		1.0, 1.0	.;.;.;D;D;.;D;D;D;.
Vest4		0.94, 0.93, 0.93, 0.93
MutPred		0.77		Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);Gain of catalytic residue at L334 (P = 0.0196);
MVP		0.95
MPC		2.0
ClinPred		1.0	D
GERP RS		5.3
Varity_R		0.93
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: rs1553548096; hg19: chr2-166905416;