rs879255709

Positions:

• chr12-51806434-G-A
• chr12-51806434-G-T

Variant summary

Our verdict is Pathogenic. Variant got 17 ACMG points: 17P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate PP5_Very_Strong

The NM_001330260.2(SCN8A):​c.4948G>A​(p.Ala1650Thr) 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 Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A1650V) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2 O:1
• 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 17 ACMG points.

• PM1: In a repeat IV (size 297) in uniprot entity SCN8A_HUMAN there are 10 pathogenic changes around while only 1 benign (91%) 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 chr12-51806435-C-T is described in Lovd as [Pathogenic].
• 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 10.436 (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, 0.936
• PP5: Variant 12-51806434-G-A is Pathogenic according to our data. Variant chr12-51806434-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 253294.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.4948G>A	p.Ala1650Thr	missense_variant	27/27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.4948G>A	p.Ala1650Thr	missense_variant	27/27	ENST00000354534.11	NP_055006.1
SCN8A	NM_001177984.3	c.4825G>A	p.Ala1609Thr	missense_variant	26/26		NP_001171455.1
SCN8A	NM_001369788.1	c.4825G>A	p.Ala1609Thr	missense_variant	26/26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000354534.11	c.4948G>A	p.Ala1650Thr	missense_variant	27/27	1	NM_014191.4	ENSP00000346534.4
SCN8A	ENST00000627620.5	c.4948G>A	p.Ala1650Thr	missense_variant	27/27	5	NM_001330260.2	ENSP00000487583.2
SCN8A	ENST00000599343.5	c.4981G>A	p.Ala1661Thr	missense_variant	26/26	5		ENSP00000476447.3
SCN8A	ENST00000355133.7	c.4825G>A	p.Ala1609Thr	missense_variant	25/25	1		ENSP00000347255.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Epileptic encephalopathy Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Neurogenetics Laboratory - MEYER, AOU Meyer

Nov 16, 2016

- -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Feb 10, 2016

The A1650T pathogenic variant in the SCN8A gene has been reported previously as a de novo variant in two unrelated individuals whose combined features include intractable early-onset epileptic encephalopathy, severely regressed development, intellectual disability, quadriparesis with dystonic posturing, hypotonia, and MRI abnormalities including asymmetric ventricles and mild diffuse atrophy (Larsen et al., 2015; Ohba et al., 2014). The A1650T variant was not observed in approximately 6500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. The A1650T variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs at a position that is conserved across species and in silico analysis predicts this variant is probably damaging to the protein structure/function. We interpret A1650T as a pathogenic variant. -

Developmental and epileptic encephalopathy, 13 Other:1

not provided, no classification provided

literature only

GeneReviews

-

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.50	D
BayesDel_noAF	Pathogenic	0.48
CADD	Pathogenic	30
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.97	D;.;.;.;.
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.96
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.97	D;D;.;D;D
M_CAP	Pathogenic	0.94	D
MetaRNN	Pathogenic	0.94	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.5	M;.;.;.;M
PrimateAI	Pathogenic	0.89	D
PROVEAN	Uncertain	-3.6	D;D;.;.;.
REVEL	Pathogenic	0.95
Sift	Pathogenic	0.0	D;D;.;.;.
Sift4G	Uncertain	0.015	D;D;D;D;D
Polyphen		1.0	D;.;.;.;.
Vest4		0.75
MutPred		0.69		Gain of MoRF binding (P = 0.3867);.;.;.;Gain of MoRF binding (P = 0.3867);
MVP		0.99
MPC		2.2
ClinPred		0.99	D
GERP RS		5.3
Varity_R		0.91
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: rs879255709; hg19: chr12-52200218;