NM_001330260.2:c.202A>G

Variant names:

• chr12-51663019-A-G
• rs797045945
• NM_001330260.2:c.202A>G

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 3P and 1B. PM2 PP2 BP6

The NM_001330260.2(SCN8A):​c.202A>G​(p.Ile68Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:1
• Conservation: PhyloP100: 9.32
• Publications: 1 publications found

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

ACMG classification

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• 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.
• BP6: Variant 12-51663019-A-G is Benign according to our data. Variant chr12-51663019-A-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 212135.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN8A	NM_001330260.2	c.202A>G	p.Ile68Val	missense_variant	Exon 2 of 27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.202A>G	p.Ile68Val	missense_variant	Exon 2 of 27	ENST00000354534.11	NP_055006.1
SCN8A	NM_001177984.3	c.202A>G	p.Ile68Val	missense_variant	Exon 2 of 26		NP_001171455.1
SCN8A	NM_001369788.1	c.202A>G	p.Ile68Val	missense_variant	Exon 2 of 26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000354534.11	c.202A>G	p.Ile68Val	missense_variant	Exon 2 of 27	1	NM_014191.4	ENSP00000346534.4
SCN8A	ENST00000627620.5	c.202A>G	p.Ile68Val	missense_variant	Exon 2 of 27	5	NM_001330260.2	ENSP00000487583.2
SCN8A	ENST00000599343.5	c.202A>G	p.Ile68Val	missense_variant	Exon 1 of 26	5		ENSP00000476447.3
SCN8A	ENST00000355133.7	c.202A>G	p.Ile68Val	missense_variant	Exon 1 of 25	1		ENSP00000347255.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Developmental and epileptic encephalopathy Uncertain:1

Jul 04, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. 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: "Probably Damaging"; Align-GVGD: "Class C0"). ClinVar contains an entry for this variant (Variation ID: 212135). This variant has been observed in individual(s) with clinical features of SCN8A-related conditions (PMID: 27875746). This variant is not present in population databases (ExAC no frequency). This sequence change replaces isoleucine with valine at codon 68 of the SCN8A protein (p.Ile68Val). The isoleucine residue is moderately conserved and there is a small physicochemical difference between isoleucine and valine. -

not specified Benign:1

Dec 24, 2014

Genetic Services Laboratory, University of Chicago

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.45
BayesDel_addAF	Pathogenic	0.25	D
BayesDel_noAF	Uncertain	0.12
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Benign	0.41	.;T;.;.;.;.
Eigen	Uncertain	0.49
Eigen_PC	Uncertain	0.50
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.88	D;D;D;.;D;D
M_CAP	Pathogenic	0.30	D
MetaRNN	Uncertain	0.71	D;D;D;D;D;D
MetaSVM	Uncertain	0.72	D
MutationAssessor	Uncertain	2.8	.;M;M;M;M;M
PhyloP100		9.3
PrimateAI	Uncertain	0.75	T
PROVEAN	Benign	-0.92	.;N;N;N;.;.
REVEL	Pathogenic	0.71
Sift	Uncertain	0.0010	.;D;D;D;.;.
Sift4G	Benign	0.081	.;T;T;T;T;T
Polyphen		0.86	.;P;.;.;.;.
Vest4		0.54, 0.52, 0.53, 0.51
MutPred		0.62		Loss of helix (P = 0.0237);Loss of helix (P = 0.0237);Loss of helix (P = 0.0237);Loss of helix (P = 0.0237);Loss of helix (P = 0.0237);Loss of helix (P = 0.0237);
MVP		0.94
MPC		1.9
ClinPred		0.69	D
GERP RS		4.0
PromoterAI		0.045	Neutral
Varity_R		0.18
gMVP		0.82
Mutation Taster		=33/67	disease causing

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: rs797045945; hg19: chr12-52056803; COSMIC: COSV61976693; COSMIC: COSV61976693;