rs121918780

Positions:

• chr2-166051928-A-G
• chr2-166051928-A-T

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate PP5_Moderate

The NM_001165963.4(SCN1A):​c.755T>C​(p.Ile252Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,322 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 Pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. I252L) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: SCN1A NM_001165963.4 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 9.32

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 11 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 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 chr2-166051929-T-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 2036212.Status of the report is criteria_provided_single_submitter, 1 stars.
• 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, 0.935
• PP5: Variant 2-166051928-A-G is Pathogenic according to our data. Variant chr2-166051928-A-G is described in ClinVar as [Pathogenic]. Clinvar id is 408928.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.755T>C	p.Ile252Thr	missense_variant	9/29	ENST00000674923.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SCN1A	ENST00000674923.1	c.755T>C	p.Ile252Thr	missense_variant	9/29		NM_001165963.4	P4
SCN1A-AS1	ENST00000651574.1	n.487+15798A>G		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460322 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 726494

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: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 04, 2023

Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt SCN1A protein function. ClinVar contains an entry for this variant (Variation ID: 408928). This missense change has been observed in individuals with clinical features of SCN1A-related conditions (Invitae). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces isoleucine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 252 of the SCN1A protein (p.Ile252Thr). For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Ile252 amino acid residue in SCN1A. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 15087100). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. -

Computational scores

Source: dbNSFP v4.3

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	0.98	.;.;.;D;.;.;D;.;.;.
Eigen	Pathogenic	0.89
Eigen_PC	Pathogenic	0.83
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.93	D;D;D;D;.;D;.;.;D;D
M_CAP	Pathogenic	0.95	D
MetaRNN	Pathogenic	0.93	D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Uncertain	2.8	.;.;.;M;M;.;M;M;M;M
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.95	D
PROVEAN	Pathogenic	-4.8	.;.;.;D;.;.;D;.;D;D
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	.;.;.;D;.;.;D;.;D;D
Sift4G	Benign	0.11	.;.;.;T;.;.;T;.;T;T
Polyphen		1.0, 1.0	.;.;.;D;D;.;D;D;D;.
Vest4		0.94, 0.93, 0.94, 0.90
MutPred		0.71		Loss of stability (P = 0.002);Loss of stability (P = 0.002);Loss of stability (P = 0.002);Loss of stability (P = 0.002);Loss of stability (P = 0.002);Loss of stability (P = 0.002);Loss of stability (P = 0.002);Loss of stability (P = 0.002);Loss of stability (P = 0.002);Loss of stability (P = 0.002);
MVP		0.97
MPC		1.9
ClinPred		1.0	D
GERP RS		5.4
Varity_R		0.84
gMVP		0.93

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: rs121918780; hg19: chr2-166908438;