12-51662827-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP2

The NM_014191.4(SCN8A):c.10C>T(p.Arg4Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,442 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. R4Q) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: SCN8A NM_014191.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.80

Genes affected

SCN8A (HGNC:10596): (sodium voltage-gated channel alpha subunit 8) This gene encodes a member of the sodium channel alpha subunit gene family. The encoded protein forms the ion pore region of the voltage-gated sodium channel. This protein is essential for the rapid membrane depolarization that occurs during the formation of the action potential in excitable neurons. Mutations in this gene are associated with cognitive disability, pancerebellar atrophy and ataxia. Alternate splicing results in multiple transcript variants.[provided by RefSeq, May 2010]

ACMG classification

Verdict is Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, SCN8A

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SCN8A	NM_001330260.2	c.10C>T	p.Arg4Trp	missense_variant	2/27	ENST00000627620.5
SCN8A	NM_014191.4	c.10C>T	p.Arg4Trp	missense_variant	2/27	ENST00000354534.11
SCN8A	NM_001177984.3	c.10C>T	p.Arg4Trp	missense_variant	2/26
SCN8A	NM_001369788.1	c.10C>T	p.Arg4Trp	missense_variant	2/26

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SCN8A	ENST00000354534.11	c.10C>T	p.Arg4Trp	missense_variant	2/27	1	NM_014191.4	P4
SCN8A	ENST00000627620.5	c.10C>T	p.Arg4Trp	missense_variant	2/27	5	NM_001330260.2	A1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461442 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 726990

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.0000383

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000471 Hom.: 0

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain: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

Invitae

Sep 18, 2023

This sequence change replaces arginine, which is basic and polar, with tryptophan, which is neutral and slightly polar, at codon 4 of the SCN8A protein (p.Arg4Trp). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with SCN8A-related conditions. ClinVar contains an entry for this variant (Variation ID: 1020681). 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 not expected to disrupt SCN8A protein function. 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	0.29
BayesDel_addAF	Uncertain	0.15	D
BayesDel_noAF	Uncertain	-0.020
Cadd	Pathogenic	32
Dann	Pathogenic	1.0
Eigen	Uncertain	0.44
Eigen_PC	Uncertain	0.49
FATHMM_MKL	Uncertain	0.92	D
LIST_S2	Pathogenic	0.99	D;D;D;.;D;D
M_CAP	Uncertain	0.14	D
MetaRNN	Uncertain	0.48	T;T;T;T;T;T
MetaSVM	Uncertain	0.78	D
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Uncertain	0.58	T
Polyphen		0.99	.;D;.;.;.;.
Vest4		0.27, 0.35, 0.39, 0.38, 0.47
MutPred		0.41		Gain of catalytic residue at A3 (P = 0.0103);Gain of catalytic residue at A3 (P = 0.0103);Gain of catalytic residue at A3 (P = 0.0103);Gain of catalytic residue at A3 (P = 0.0103);Gain of catalytic residue at A3 (P = 0.0103);Gain of catalytic residue at A3 (P = 0.0103);
MVP		0.68
MPC		1.3
ClinPred		0.79	D
GERP RS		5.0
Varity_R		0.18
gMVP		0.60

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: rs1940949996; hg19: chr12-52056611; COSMIC: COSV105910302; COSMIC: COSV105910302;