NM_001330260.2:c.4877G>A

Variant names:

• chr12-51806363-G-A
• rs886044328
• NM_001330260.2:c.4877G>A

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1 PM2 PP2 PP3_Strong PP5

The NM_001330260.2(SCN8A):​c.4877G>A​(p.Arg1626His) 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. 13/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:4 U:2
• Conservation: PhyloP100: 10.0

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 Pathogenic. Variant got 10 ACMG points.

• PM1: In a transmembrane_region Helical; Name=S4 of repeat IV (size 16) in uniprot entity SCN8A_HUMAN there are 4 pathogenic changes around while only 0 benign (100%) in NM_001330260.2
• 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, infantile convulsions and choreoathetosis, cognitive impairment with or without cerebellar ataxia, undetermined early-onset epileptic encephalopathy, complex neurodevelopmental disorder, developmental and epileptic encephalopathy, 13, benign familial infantile epilepsy, seizures, benign familial infantile, 5.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.979
• PP5: Variant 12-51806363-G-A is Pathogenic according to our data. Variant chr12-51806363-G-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 290005.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Uncertain_significance=1, Pathogenic=3}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN8A	NM_001330260.2	c.4877G>A	p.Arg1626His	missense_variant	Exon 27 of 27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.4877G>A	p.Arg1626His	missense_variant	Exon 27 of 27	ENST00000354534.11	NP_055006.1
SCN8A	NM_001177984.3	c.4754G>A	p.Arg1585His	missense_variant	Exon 26 of 26		NP_001171455.1
SCN8A	NM_001369788.1	c.4754G>A	p.Arg1585His	missense_variant	Exon 26 of 26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000354534.11	c.4877G>A	p.Arg1626His	missense_variant	Exon 27 of 27	1	NM_014191.4	ENSP00000346534.4
SCN8A	ENST00000627620.5	c.4877G>A	p.Arg1626His	missense_variant	Exon 27 of 27	5	NM_001330260.2	ENSP00000487583.2
SCN8A	ENST00000599343.5	c.4910G>A	p.Arg1637His	missense_variant	Exon 26 of 26	5		ENSP00000476447.3
SCN8A	ENST00000355133.7	c.4754G>A	p.Arg1585His	missense_variant	Exon 25 of 25	1		ENSP00000347255.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1440384 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 713410

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:4 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Developmental and epileptic encephalopathy, 13 Pathogenic:2

Jul 17, 2023

Victorian Clinical Genetics Services, Murdoch Childrens Research Institute

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as Pathogenic. Following criteria are met: 0103 - Loss of function and gain of function are known mechanisms of disease in this gene, and are associated with cognitive impairment with or without cerebellar ataxia (MIM#614306), and developmental and epileptic encephalopathy 13 (MIM#614558), respectively. In addition, gain of function is speculated for benign familial infantile seizures, 5 (MIM#617080) (PMID: 31904124, OMIM). (I) 0107 - This gene is associated with autosomal dominant disease. (I) 0200 - Variant is predicted to result in a missense amino acid change from arginine to histidine. (I) 0251 - This variant is heterozygous. (I) 0301 - Variant is absent from gnomAD (both v2 and v3). (SP) 0501 - Missense variant consistently predicted to be damaging by multiple in silico tools or highly conserved with a major amino acid change. (SP) 0603 - Missense variant in a region that is highly intolerant to missense variation (high constraint region in DECIPHER). (SP) 0708 - Other missense variants comparable to the one identified in this case have conflicting previous evidence for pathogenicity. p.(Arg1626Cys) and p.(Arg1626Leu) have been classified as pathogenic/likely pathogenic and VUS, respectively (ClinVar). (I) 0801 - This variant has strong previous evidence of pathogenicity in unrelated individuals. It has been reported de novo in at least three individuals with intellectual disability and seizures, or developmental and epileptic encephalopathy (PMID: 35701389; ClinVar). (SP) 1007 - No published functional evidence has been identified for this variant. (I) 1206 - This variant has been shown to be paternally inherited (by trio analysis). (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -

Oct 04, 2022

Genetics Laboratory, UDIAT-Centre Diagnòstic, Hospital Universitari Parc Tauli

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

PS4_supporting;PM1;PM2_supporting;PM5;PM6;PP2;PP3; -

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Nov 13, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine, which is basic and polar, with histidine, which is basic and polar, at codon 1626 of the SCN8A protein (p.Arg1626His). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with developmental and epileptic encephalopathy (PMID: 35701389). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 290005). 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%. For these reasons, this variant has been classified as Pathogenic. -

Cognitive impairment with or without cerebellar ataxia;C3281191:Developmental and epileptic encephalopathy, 13;C4310728:Seizures, benign familial infantile, 5 Pathogenic:1

Apr 25, 2017

Génétique des Maladies du Développement, Hospices Civils de Lyon

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Abnormal cerebral morphology Uncertain:1

-

Diagnostic Laboratory, Strasbourg University Hospital

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

not provided Uncertain:1

Aug 09, 2016

Eurofins Ntd Llc (ga)

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	31
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.99	D;.;.;.;.
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.92	D;D;.;D;D
M_CAP	Pathogenic	0.93	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D
MetaSVM	Pathogenic	0.97	D
MutationAssessor	Pathogenic	3.5	H;.;.;.;H
PrimateAI	Pathogenic	0.91	D
PROVEAN	Pathogenic	-4.5	D;D;.;.;.
REVEL	Pathogenic	0.95
Sift	Pathogenic	0.0	D;D;.;.;.
Sift4G	Benign	0.076	T;T;T;T;T
Polyphen		1.0	D;.;.;.;.
Vest4		0.94
MutPred		0.84		Gain of methylation at R1629 (P = 0.0634);.;.;.;Gain of methylation at R1629 (P = 0.0634);
MVP		1.0
MPC		2.5
ClinPred		1.0	D
GERP RS		5.3
Varity_R		0.82
gMVP		0.99

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: rs886044328; hg19: chr12-52200147; COSMIC: COSV61990808; COSMIC: COSV61990808;