rs878854974

Positions:

• chr12-51762651-T-G

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM1 PM2 PP2 PP3_Strong PP5_Moderate

The NM_014191.4(SCN8A):​c.2519T>G​(p.Leu840Arg) 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. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN8A NM_014191.4 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 8.02

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 11 ACMG points.

• PM1: In a repeat II (size 272) in uniprot entity SCN8A_HUMAN there are 6 pathogenic changes around while only 0 benign (100%) in NM_014191.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), SCN8A. . Gene score misZ 0.78755 (greater than the threshold 3.09). Trascript score misZ 10.278 (greater than threshold 3.09). GenCC has associacion of gene with 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, 0.988
• PP5: Variant 12-51762651-T-G is Pathogenic according to our data. Variant chr12-51762651-T-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 240885.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SCN8A	NM_001330260.2	c.2519T>G	p.Leu840Arg	missense_variant	15/27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.2519T>G	p.Leu840Arg	missense_variant	15/27	ENST00000354534.11	NP_055006.1
SCN8A	NM_001177984.3	c.2519T>G	p.Leu840Arg	missense_variant	15/26		NP_001171455.1
SCN8A	NM_001369788.1	c.2519T>G	p.Leu840Arg	missense_variant	15/26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000354534.11	c.2519T>G	p.Leu840Arg	missense_variant	15/27	1	NM_014191.4	ENSP00000346534	P4
SCN8A	ENST00000627620.5	c.2519T>G	p.Leu840Arg	missense_variant	15/27	5	NM_001330260.2	ENSP00000487583	A1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 13, 2019

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. 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"). This variant has been observed in individual(s) with clinical features of SCN8A-related disease (Invitae). In at least one individual the variant was observed to be de novo. This variant is not present in population databases (ExAC no frequency). This sequence change replaces leucine with arginine at codon 840 of the SCN8A protein (p.Leu840Arg). The leucine residue is highly conserved and there is a moderate physicochemical difference between leucine and arginine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	D;.;.;.;.
Eigen	Pathogenic	0.83
Eigen_PC	Pathogenic	0.72
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Benign	0.83	T;T;.;T;T
M_CAP	Pathogenic	0.93	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.3	M;M;M;.;M
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Pathogenic	0.83	D
PROVEAN	Pathogenic	-5.6	D;D;D;.;.
REVEL	Pathogenic	0.99
Sift	Pathogenic	0.0	D;D;D;.;.
Sift4G	Uncertain	0.013	D;D;D;D;D
Polyphen		1.0	D;.;.;.;.
Vest4		0.98
MutPred		0.89		Gain of MoRF binding (P = 0.0109);Gain of MoRF binding (P = 0.0109);Gain of MoRF binding (P = 0.0109);.;Gain of MoRF binding (P = 0.0109);
MVP		0.99
MPC		4.3
ClinPred		1.0	D
GERP RS		4.0
Varity_R		0.96
gMVP		1.0

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs878854974; hg19: chr12-52156435;