chr12-51751523-C-T

Position:

• chr12-51751523-C-T

Variant summary

Our verdict is Pathogenic. Variant got 15 ACMG points: 15P and 0B. PM1 PM2 PP2 PP3_Moderate PP5_Very_Strong

The NM_014191.4(SCN8A):​c.2300C>T​(p.Thr767Ile) 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 Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN8A NM_014191.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4 O:1
• Conservation: PhyloP100: 7.91

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 15 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, 0.921
• PP5: Variant 12-51751523-C-T is Pathogenic according to our data. Variant chr12-51751523-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 208500.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SCN8A	NM_001330260.2	c.2300C>T	p.Thr767Ile	missense_variant	14/27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.2300C>T	p.Thr767Ile	missense_variant	14/27	ENST00000354534.11	NP_055006.1
SCN8A	NM_001177984.3	c.2300C>T	p.Thr767Ile	missense_variant	14/26		NP_001171455.1
SCN8A	NM_001369788.1	c.2300C>T	p.Thr767Ile	missense_variant	14/26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000354534.11	c.2300C>T	p.Thr767Ile	missense_variant	14/27	1	NM_014191.4	ENSP00000346534	P4
SCN8A	ENST00000627620.5	c.2300C>T	p.Thr767Ile	missense_variant	14/27	5	NM_001330260.2	ENSP00000487583	A1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Inborn genetic diseases Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 06, 2017

The p.T767I variant (also known as c.2300C>T), located in coding exon 13 of the SCN8A gene, results from a C to T substitution at nucleotide position 2300. The threonine at codon 767 is replaced by isoleucine, an amino acid with similar properties. De novo occurrence of this variant has been reported in a patient with profound developmental delay, intellectual disability and intractable epilepsy (Estacion M et al. Neurobiol. Dis., 2014 Sep;69:117-23). In neuronal cells, this variant caused enhanced channel activation and increased ramp current. Pyramidal hippocampal neurons expressing the mutant channel also exhibited increased spontaneous firing and frequency of evoked action potentials. This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Early infantile epileptic encephalopathy with suppression bursts Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 31, 2022

This sequence change replaces threonine, which is neutral and polar, with isoleucine, which is neutral and non-polar, at codon 767 of the SCN8A protein (p.Thr767Ile). For these reasons, this variant has been classified as Pathogenic. Experimental studies have shown that this missense change affects SCN8A function (PMID: 24874546). 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: "Benign"; Align-GVGD: "Class C0"). ClinVar contains an entry for this variant (Variation ID: 208500). This missense change has been observed in individual(s) with clinical features of SCN8A-related conditions (PMID: 24874546, 30171078). In at least one individual the variant was observed to be de novo. This variant is not present in population databases (gnomAD no frequency). -

Developmental and epileptic encephalopathy, 13 Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

Mendelics

Jul 01, 2014

- -

Developmental and epileptic encephalopathy, 13;C4310728:Seizures, benign familial infantile, 5 Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Dec 31, 2017

- -

Complex neurodevelopmental disorder Other:1

not provided, no classification provided

literature only

Channelopathy-Associated Epilepsy Research Center

-

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	26
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.97	D;.;.;.;.
Eigen	Pathogenic	0.84
Eigen_PC	Pathogenic	0.78
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.92	D;D;.;D;D
M_CAP	Pathogenic	0.78	D
MetaRNN	Pathogenic	0.92	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	0.90	D
PROVEAN	Pathogenic	-5.8	D;D;D;.;.
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	D;D;D;.;.
Sift4G	Benign	0.070	T;T;T;T;T
Polyphen		1.0	D;.;.;.;.
Vest4		0.87
MutPred		0.58		Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);Loss of sheet (P = 0.1158);.;Loss of sheet (P = 0.1158);
MVP		1.0
MPC		1.9
ClinPred		1.0	D
GERP RS		4.7
Varity_R		0.89
gMVP		0.96

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: rs797045013; hg19: chr12-52145307;