12-51702881-G-A

Variant names:

• chr12-51702881-G-A
• rs1555219147
• NM_001330260.2:c.1101G>A

Variant summary

Our verdict is Pathogenic. The variant received 15 ACMG points: 15P and 0B. PS1 PM1 PM2 PM5 PP2 PP3_Moderate PP5_Moderate

The NM_001330260.2(SCN8A):​c.1101G>A​(p.Met367Ile) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Likely pathogenic in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M367V) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 10.0
• Publications: 0 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: Pathogenic. The variant received 15 ACMG points.

• PS1: Transcript NM_001330260.2 (SCN8A) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in ClinVar.
• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 uncertain in NM_001330260.2
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr12-51702879-A-G is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 207105.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• 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.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.932
• PP5: Variant 12-51702881-G-A is Pathogenic according to our data. Variant chr12-51702881-G-A is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 461331.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN8A	NM_001330260.2	c.1101G>A	p.Met367Ile	missense_variant	Exon 9 of 27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.1101G>A	p.Met367Ile	missense_variant	Exon 9 of 27	ENST00000354534.11	NP_055006.1
SCN8A	NM_001177984.3	c.1101G>A	p.Met367Ile	missense_variant	Exon 9 of 26		NP_001171455.1
SCN8A	NM_001369788.1	c.1101G>A	p.Met367Ile	missense_variant	Exon 9 of 26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000354534.11	c.1101G>A	p.Met367Ile	missense_variant	Exon 9 of 27	1	NM_014191.4	ENSP00000346534.4
SCN8A	ENST00000627620.5	c.1101G>A	p.Met367Ile	missense_variant	Exon 9 of 27	5	NM_001330260.2	ENSP00000487583.2
SCN8A	ENST00000599343.5	c.1101G>A	p.Met367Ile	missense_variant	Exon 8 of 26	5		ENSP00000476447.3
SCN8A	ENST00000355133.7	c.1101G>A	p.Met367Ile	missense_variant	Exon 8 of 25	1		ENSP00000347255.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Developmental and epileptic encephalopathy Pathogenic:1

May 29, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces methionine, which is neutral and non-polar, with isoleucine, which is neutral and non-polar, at codon 367 of the SCN8A protein (p.Met367Ile). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with seizure (Invitae). ClinVar contains an entry for this variant (Variation ID: 461331). 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 SCN8A protein function with a positive predictive value of 95%. This variant disrupts the p.Met367 amino acid residue in SCN8A. Other variant(s) that disrupt this residue have been determined to be pathogenic (Invitae). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.53
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.95	.;D;.;.;.;.;.
Eigen	Pathogenic	0.71
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.95	D;D;D;.;D;D;D
M_CAP	Pathogenic	0.85	D
MetaRNN	Pathogenic	0.93	D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Benign	1.0	.;L;L;L;L;L;.
PhyloP100		10
PrimateAI	Pathogenic	0.91	D
PROVEAN	Uncertain	-3.9	.;D;D;D;.;.;.
REVEL	Pathogenic	0.94
Sift	Pathogenic	0.0	.;D;D;D;.;.;.
Sift4G	Benign	0.16	.;T;T;T;T;T;T
Polyphen		0.81, 0.96	.;P;.;.;D;.;.
Vest4		0.74, 0.72, 0.74, 0.75, 0.73
MutPred		0.70		Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);.;
MVP		1.0
MPC		2.1
ClinPred		0.97	D
GERP RS		5.0
Varity_R		0.87
gMVP		0.97
Mutation Taster		=11/89	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: rs1555219147; hg19: chr12-52096665;