NM_001330260.2:c.1474C>T

Variant names:

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 1P and 4B. PP2BS2

The NM_001330260.2(SCN8A):c.1474C>T(p.Arg492Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000249 in 1,607,420 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. R492H) has been classified as Likely benign.

Frequency

Genomes: 𝑓 0.000013 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000026 ( 0 hom. )

Consequence

SCN8A
NM_001330260.2 missense

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:2

Conservation

PhyloP100: 1.12

Publications

0 publications found

Variant links:

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]

SCN8A Gene-Disease associations (from GenCC):

complex neurodevelopmental disorder
Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
developmental and epileptic encephalopathy, 13
Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P, Ambry Genetics
cognitive impairment with or without cerebellar ataxia
Inheritance: AD Classification: STRONG Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
seizures, benign familial infantile, 5
Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
benign familial infantile epilepsy
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
infantile convulsions and choreoathetosis
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
undetermined early-onset epileptic encephalopathy
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
myoclonus, familial, 2
Inheritance: AD Classification: LIMITED Submitted by: Ambry Genetics

SCN8A links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -3 ACMG points.

PP2

Missense variant in the SCN8A gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 213 curated pathogenic missense variants (we use a threshold of 10). The gene has 45 curated benign missense variants. Gene score misZ: 0.78755 (below the threshold of 3.09). Trascript score misZ: 10.436 (above the threshold of 3.09). GenCC associations: The gene is linked to myoclonus, familial, 2, developmental and epileptic encephalopathy, 13, undetermined early-onset epileptic encephalopathy, benign familial infantile epilepsy, complex neurodevelopmental disorder, seizures, benign familial infantile, 5, cognitive impairment with or without cerebellar ataxia, infantile convulsions and choreoathetosis.

BS2

High AC in GnomAdExome4 at 38 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN8A	NM_001330260.2 link	c.1474C>T	p.Arg492Cys	missense_variant	Exon 11 of 27	ENST00000627620.5	NP_001317189.1	Q9UQD0-2Q6B4S4
SCN8A	NM_014191.4 link	c.1474C>T	p.Arg492Cys	missense_variant	Exon 11 of 27	ENST00000354534.11	NP_055006.1	Q9UQD0-1
SCN8A	NM_001177984.3 link	c.1474C>T	p.Arg492Cys	missense_variant	Exon 11 of 26		NP_001171455.1	Q9UQD0-5
SCN8A	NM_001369788.1 link	c.1474C>T	p.Arg492Cys	missense_variant	Exon 11 of 26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	UniProt
SCN8A	ENST00000354534.11 link	c.1474C>T	p.Arg492Cys	missense_variant	Exon 11 of 27	1	NM_014191.4	ENSP00000346534.4	Q9UQD0-1
SCN8A	ENST00000627620.5 link	c.1474C>T	p.Arg492Cys	missense_variant	Exon 11 of 27	5	NM_001330260.2	ENSP00000487583.2	Q9UQD0-2
SCN8A	ENST00000599343.5 link	c.1474C>T	p.Arg492Cys	missense_variant	Exon 10 of 26	5		ENSP00000476447.3	Q9UQD0-3
SCN8A	ENST00000355133.7 link	c.1474C>T	p.Arg492Cys	missense_variant	Exon 10 of 25	1		ENSP00000347255.4	Q9UQD0-5

Frequencies

GnomAD3 genomes

AF:

0.0000132

AC:

AN:

151942

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000242

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.0000421

AC:

AN:

237448

AF XY:

0.0000389

show subpopulations

Gnomad AFR exome

AF:

0.0000688

Gnomad AMR exome

AF:

0.0000600

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000468

Gnomad OTH exome

AF:

0.000172

GnomAD4 exome

AF:

0.0000261

AC:

AN:

1455360

Hom.:

Cov.:

AF XY:

0.0000207

AC XY:

AN XY:

723260

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33326

American (AMR)

AF:

0.0000685

AC:

AN:

43780

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26000

East Asian (EAS)

AF:

0.00

AC:

AN:

39488

South Asian (SAS)

AF:

0.0000118

AC:

AN:

84916

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53090

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5764

European-Non Finnish (NFE)

AF:

0.0000307

AC:

AN:

1108826

Other (OTH)

AF:

0.00

AC:

AN:

60170

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.461

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.0000132

AC:

AN:

152060

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74324

show subpopulations

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.0000241

AC:

AN:

41454

American (AMR)

AF:

0.00

AC:

AN:

15274

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3466

East Asian (EAS)

AF:

0.00

AC:

AN:

5178

South Asian (SAS)

AF:

0.00

AC:

AN:

4810

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10574

Middle Eastern (MID)

AF:

0.00

AC:

AN:

294

European-Non Finnish (NFE)

AF:

0.0000147

AC:

AN:

67988

Other (OTH)

AF:

0.00

AC:

AN:

2112

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.400

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Alfa

AF:

0.0000868

Hom.:

ExAC

AF:

0.0000331

AC:

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Inborn genetic diseases

Uncertain:1

Jun 12, 2017

Ambry Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The p.R492C variant (also known as c.1474C>T), located in coding exon 10 of the SCN8A gene, results from a C to T substitution at nucleotide position 1474. The arginine at codon 492 is replaced by cysteine, an amino acid with highly dissimilar properties. This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Developmental and epileptic encephalopathy

Uncertain:1

Jun 03, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 492 of the SCN8A protein (p.Arg492Cys). This variant is present in population databases (rs576362165, gnomAD 0.006%). 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: 589221). 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) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on 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

Pathogenic

0.69

BayesDel_addAF

Uncertain

0.14

BayesDel_noAF

Pathogenic

0.15

CADD

Pathogenic

(source)

DANN

Pathogenic

1.0

DEOGEN2

Pathogenic

0.87

.;D;.;.;.;.;.

Eigen

Uncertain

0.60

Eigen_PC

Uncertain

0.50

FATHMM_MKL

Uncertain

0.91

LIST_S2

Pathogenic

0.98

D;D;D;.;D;D;D

M_CAP

Pathogenic

0.63

MetaRNN

Uncertain

0.62

D;D;D;D;D;D;D

MetaSVM

Pathogenic

0.86

MutationAssessor

Pathogenic

2.9

.;M;M;M;M;M;.

PhyloP100

1.1

PrimateAI

Pathogenic

0.87

PROVEAN

Pathogenic

-6.5

.;D;D;D;.;.;.

REVEL

Pathogenic

0.67

Sift

Pathogenic

0.0

.;D;D;D;.;.;.

Sift4G

Uncertain

0.0060

.;D;D;D;D;D;D

Polyphen

1.0

.;D;.;.;D;.;.

Vest4

0.61, 0.60, 0.66, 0.61, 0.58

MutPred

0.26

Loss of helix (P = 0.0068);Loss of helix (P = 0.0068);Loss of helix (P = 0.0068);Loss of helix (P = 0.0068);Loss of helix (P = 0.0068);Loss of helix (P = 0.0068);.;

MVP

0.92

MPC

2.4

ClinPred

0.70

GERP RS

4.2

Varity_R

0.71

gMVP

0.64

Mutation Taster

=24/76

disease causing

(source)

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over