rs121917991

Positions:

• chr2-166037805-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 8P and 4B. PM1 PM2 PM5 PP2 PP3 BS2

The NM_001165963.4(SCN1A):​c.2917A>G​(p.Met973Val) variant causes a missense change. The variant allele was found at a frequency of 0.00000342 in 1,461,882 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. M973K) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1 O:1
• Conservation: PhyloP100: 6.17

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 Uncertain_significance. Variant got 4 ACMG points.

• PM1: In a transmembrane_region Helical; Name=S6 of repeat II (size 20) in uniprot entity SCN1A_HUMAN there are 9 pathogenic changes around while only 0 benign (100%) 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 chrnull-null-null-null is described in UniProt as null.
• 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, 0.837
• BS2: High AC in GnomAdExome4 at 5 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SCN1A	NM_001165963.4	c.2917A>G	p.Met973Val	missense_variant	18/29	ENST00000674923.1	NP_001159435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN1A	ENST00000674923.1	c.2917A>G	p.Met973Val	missense_variant	18/29		NM_001165963.4	ENSP00000501589	P4
SCN1A-AS1	ENST00000651574.1	n.487+1675T>C		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1461882 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727240

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000450

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1 Other:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Feb 09, 2022

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. This variant disrupts the p.Met973 amino acid residue in SCN1A. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 18930999). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C15"). ClinVar contains an entry for this variant (Variation ID: 68526). This missense change has been observed in individual(s) with SCN1A-related conditions (PMID: 17347258). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces methionine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 973 of the SCN1A protein (p.Met973Val). -

Generalized epilepsy Other:1

not provided, no classification provided

literature only

UniProtKB/Swiss-Prot

-

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.43
BayesDel_addAF	Pathogenic	0.49	D
BayesDel_noAF	Pathogenic	0.47
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.95	.;.;.;D;.;.;D;.;.;.
Eigen	Benign	0.13
Eigen_PC	Uncertain	0.29
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Benign	0.82	T;T;T;T;.;T;.;.;T;T
M_CAP	Pathogenic	0.57	D
MetaRNN	Pathogenic	0.84	D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Benign	0.44	.;.;.;N;.;.;N;.;.;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.79	T
PROVEAN	Uncertain	-3.6	.;.;.;D;.;.;D;.;D;D
REVEL	Pathogenic	0.77
Sift	Uncertain	0.0010	.;.;.;D;.;.;D;.;D;D
Sift4G	Benign	0.13	.;.;.;T;.;.;T;.;T;T
Polyphen		0.21, 0.33	.;.;.;B;B;.;B;B;B;.
Vest4		0.81, 0.85, 0.85, 0.83
MutPred		0.48		.;Gain of catalytic residue at M973 (P = 0.0191);.;Gain of catalytic residue at M973 (P = 0.0191);.;.;Gain of catalytic residue at M973 (P = 0.0191);.;.;.;
MVP		0.97
MPC		2.6
ClinPred		0.97	D
GERP RS		5.2
Varity_R		0.73
gMVP		0.88

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: rs121917991; hg19: chr2-166894315;