2-165991636-C-G

Variant names:

• chr2-165991636-C-G
• rs201905405
• NM_001165963.4:c.5639G>C

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM1 PM2 PP2 PP3

The NM_001165963.4(SCN1A):​c.5639G>C​(p.Gly1880Ala) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,752 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic 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. G1880E) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 4.97
• Publications: 11 publications found

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

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 14 uncertain in NM_001165963.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the SCN1A gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 848 curated pathogenic missense variants (we use a threshold of 10). The gene has 89 curated benign missense variants. Gene score misZ: 5.2206 (above the threshold of 3.09). Trascript score misZ: 7.6022 (above the threshold of 3.09). GenCC associations: The gene is linked to familial or sporadic hemiplegic migraine, myoclonic-astatic epilepsy, arthrogryposis, Dravet syndrome, malignant migrating partial seizures of infancy, generalized epilepsy with febrile seizures plus, type 2, migraine, familial hemiplegic, 3, developmental and epileptic encephalopathy, 6A, familial hemiplegic migraine, generalized epilepsy with febrile seizures plus, genetic developmental and epileptic encephalopathy, Lennox-Gastaut syndrome.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.752

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.5639G>C	p.Gly1880Ala	missense_variant	Exon 29 of 29	ENST00000674923.1	NP_001159435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.5639G>C	p.Gly1880Ala	missense_variant	Exon 29 of 29		NM_001165963.4	ENSP00000501589.1
SCN1A	ENST00000303395.9	c.5639G>C	p.Gly1880Ala	missense_variant	Exon 28 of 28	5		ENSP00000303540.4
SCN1A	ENST00000375405.7	c.5606G>C	p.Gly1869Ala	missense_variant	Exon 26 of 26	5		ENSP00000364554.3
SCN1A	ENST00000409050.2	c.5555G>C	p.Gly1852Ala	missense_variant	Exon 28 of 28	5		ENSP00000386312.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461752 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727182

African (AFR) AF: 0.00 AC: 0 AN: 33468

American (AMR) AF: 0.00 AC: 0 AN: 44698

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26128

East Asian (EAS) AF: 0.00 AC: 0 AN: 39696

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1111924

Other (OTH) AF: 0.00 AC: 0 AN: 60392

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Developmental and epileptic encephalopathy Uncertain:1

Oct 31, 2018

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glycine with alanine at codon 1880 of the SCN1A protein (p.Gly1880Ala). The glycine residue is highly conserved and there is a small physicochemical difference between glycine and alanine. 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 disease. 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. 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	Benign	0.17
BayesDel_addAF	Uncertain	0.11	D
BayesDel_noAF	Uncertain	-0.080
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.82	.;.;.;D;.;D;.;.;.
Eigen	Uncertain	0.60
Eigen_PC	Uncertain	0.64
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.93	D;D;D;D;.;.;.;D;D
M_CAP	Pathogenic	0.35	D
MetaRNN	Pathogenic	0.75	D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.93	D
MutationAssessor	Uncertain	2.6	.;.;.;M;.;M;.;.;.
PhyloP100		5.0
PrimateAI	Uncertain	0.76	T
PROVEAN	Pathogenic	-4.7	.;.;.;D;.;D;.;D;D
REVEL	Uncertain	0.59
Sift	Uncertain	0.0010	.;.;.;D;.;D;.;D;D
Sift4G	Benign	0.24	.;.;.;T;.;T;.;T;T
Polyphen		0.78	.;.;.;.;P;.;P;P;.
Vest4		0.44, 0.49, 0.46, 0.67
MutPred		0.33		.;.;.;Loss of glycosylation at S1879 (P = 0.0797);.;Loss of glycosylation at S1879 (P = 0.0797);.;.;.;
MVP		0.97
MPC		1.5
ClinPred		0.99	D
GERP RS		5.6
Varity_R		0.74
gMVP		0.84
Mutation Taster		=4/96	disease causing

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

Other links and lift over

dbSNP: rs201905405; hg19: chr2-166848146;