chr2-166054710-C-G

Variant names:

• chr2-166054710-C-G
• rs121918770
• NM_001165963.4:c.530G>C

Variant summary

Our verdict is Pathogenic. The variant received 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP2 PP3_Strong

The NM_001165963.4(SCN1A):​c.530G>C​(p.Gly177Ala) 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. 13/22 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G177V) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.90
• Publications: 2 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)

ACMG classification

Our verdict: Pathogenic. The variant received 11 ACMG points.

• PM1: In a hotspot region, there are 7 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 13 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 chr2-166054710-C-A is described in ClinVar as Pathogenic. ClinVar VariationId is 189904.Status of the report is criteria_provided_single_submitter, 1 stars.
• 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, 0.983

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001165963.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SCN1A	NM_001165963.4	MANE Select	c.530G>C	p.Gly177Ala	missense	Exon 7 of 29	NP_001159435.1
	SCN1A	NM_001202435.3		c.530G>C	p.Gly177Ala	missense	Exon 6 of 28	NP_001189364.1
	SCN1A	NM_001353948.2		c.530G>C	p.Gly177Ala	missense	Exon 5 of 27	NP_001340877.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SCN1A	ENST00000674923.1	MANE Select	c.530G>C	p.Gly177Ala	missense	Exon 7 of 29	ENSP00000501589.1
	SCN1A	ENST00000303395.9	TSL:5	c.530G>C	p.Gly177Ala	missense	Exon 6 of 28	ENSP00000303540.4
	SCN1A	ENST00000375405.7	TSL:5	c.530G>C	p.Gly177Ala	missense	Exon 4 of 26	ENSP00000364554.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

SCN1A-related disorder Pathogenic:1

Apr 24, 2025

3billion

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The variant is not observed in the gnomAD v4.1.0 dataset. Predicted Consequence/Location: Missense variant In silico tool predictions suggest damaging effect of the variant on gene or gene product [REVEL: 0.97 (>=0.6, sensitivity 0.68 and specificity 0.92); 3Cnet: 1.00 (> 0.75, sensitivity 0.96 and precision 0.92)]. The same nucleotide change resulting in the same amino acid change has been previously reported to be associated with SCN1A-related disorder (PMID: 30735520). The variant has been previously reported as de novo in a similarly affected individual (PMID: 30735520). Different missense changes at the same codon (p.Gly177Arg, p.Gly177Glu, p.Gly177Val) have been reported as pathogenic/likely pathogenic with strong evidence (ClinVar ID: VCV000068658, VCV000189904 / PMID: 12821740, 18076640, 26252084). Therefore, this variant is classified as Pathogenic according to the recommendation of ACMG/AMP guideline.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.99	D
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.92
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.97	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.1	H
PhyloP100		7.9
PrimateAI	Pathogenic	0.85	D
PROVEAN	Pathogenic	-5.8	D
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.012	D
Polyphen		1.0	D
Vest4		0.96
MutPred		0.88		Loss of loop (P = 0.0986)
MVP		0.99
MPC		1.8
ClinPred		1.0	D
GERP RS		5.2
Varity_R		0.98
gMVP		0.99
Mutation Taster		=0/100	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: rs121918770; hg19: chr2-166911220;