2-166048928-C-A

Variant names:

• chr2-166048928-C-A
• rs779184118
• NM_001165963.4:c.986G>T

Variant summary

Our verdict is Pathogenic. The variant received 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_001165963.4(SCN1A):​c.986G>T​(p.Gly329Val) 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. G329A) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 4.12
• Publications: 3 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 19 ACMG points.

• PM1: In a hotspot region, there are 10 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 8 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 chr2-166048928-C-G is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 1032678.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 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, 0.941
• PP5: Variant 2-166048928-C-A is Pathogenic according to our data. Variant chr2-166048928-C-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 206755.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.986G>T	p.Gly329Val	missense_variant	Exon 10 of 29	ENST00000674923.1	NP_001159435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.986G>T	p.Gly329Val	missense_variant	Exon 10 of 29		NM_001165963.4	ENSP00000501589.1
SCN1A	ENST00000303395.9	c.986G>T	p.Gly329Val	missense_variant	Exon 9 of 28	5		ENSP00000303540.4
SCN1A	ENST00000375405.7	c.986G>T	p.Gly329Val	missense_variant	Exon 7 of 26	5		ENSP00000364554.3
SCN1A	ENST00000409050.2	c.986G>T	p.Gly329Val	missense_variant	Exon 9 of 28	5		ENSP00000386312.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:2

Nov 15, 2023

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Identified in a patient with early-onset epilepsy in the published literature (PMID: 36403551); Missense variants in this gene are a common cause of disease and they are underrepresented in the general population; Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This substitution is within the extracellular loop between the S5 and S6 transmembrane segments of the first homologous domain; This variant is associated with the following publications: (PMID: 37334821, 36403551) -

Jul 01, 2017

CeGaT Center for Human Genetics Tuebingen

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Generalized epilepsy with febrile seizures plus, type 2 Pathogenic:1

Oct 02, 2017

Equipe Genetique des Anomalies du Developpement, Université de Bourgogne

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Severe myoclonic epilepsy in infancy Pathogenic:1

May 28, 2019

Mendelics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.65
BayesDel_addAF	Pathogenic	0.52	D
BayesDel_noAF	Pathogenic	0.51
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.96	.;.;.;D;.;.;D;.;.;.
Eigen	Pathogenic	0.83
Eigen_PC	Pathogenic	0.76
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.95	D;D;D;D;.;D;.;.;D;D
M_CAP	Pathogenic	0.89	D
MetaRNN	Pathogenic	0.94	D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.3	.;.;.;M;M;.;M;M;M;M
PhyloP100		4.1
PrimateAI	Uncertain	0.57	T
PROVEAN	Pathogenic	-7.6	.;.;.;D;.;.;D;.;D;D
REVEL	Pathogenic	0.88
Sift	Pathogenic	0.0	.;.;.;D;.;.;D;.;D;D
Sift4G	Uncertain	0.0040	.;.;.;D;.;.;D;.;D;D
Polyphen		1.0, 1.0	.;.;.;D;D;.;D;D;D;.
Vest4		0.88, 0.89, 0.88, 0.84
MutPred		0.66		Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);
MVP		0.98
MPC		1.9
ClinPred		1.0	D
GERP RS		5.3
Varity_R		0.90
gMVP		0.98
Mutation Taster		=0/100	disease causing (ClinVar)

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: rs779184118; hg19: chr2-166905438;