rs1555217390

Positions:

• chr12-51689037-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM2 PP2 PP3_Moderate

The NM_001330260.2(SCN8A):​c.647T>C​(p.Val216Ala) 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. 8/13 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U: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 Uncertain_significance. Variant got 5 ACMG points.

• 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 10.436 (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, 0.916

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SCN8A	NM_001330260.2	c.647T>C	p.Val216Ala	missense_variant	6/27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.706+188T>C		intron_variant		ENST00000354534.11	NP_055006.1
SCN8A	NM_001369788.1	c.647T>C	p.Val216Ala	missense_variant	6/26		NP_001356717.1
SCN8A	NM_001177984.3	c.706+188T>C		intron_variant			NP_001171455.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000627620.5	c.647T>C	p.Val216Ala	missense_variant	6/27	5	NM_001330260.2	ENSP00000487583	A1
SCN8A	ENST00000354534.11	c.706+188T>C		intron_variant		1	NM_014191.4	ENSP00000346534	P4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Early infantile epileptic encephalopathy with suppression bursts Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 23, 2023

In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant is not likely to affect RNA splicing. Experimental studies and prediction algorithms are not available or were not evaluated, and the functional significance of this variant is currently unknown. ClinVar contains an entry for this variant (Variation ID: 461348). This variant has not been reported in the literature in individuals affected with SCN8A-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces valine, which is neutral and non-polar, with alanine, which is neutral and non-polar, at codon 216 of the SCN8A protein (p.Val216Ala). The SCN8A gene has multiple clinically relevant transcripts. This variant occurs in alternate transcript NM_001330260.1, and corresponds to NM_014191.3:c.706+188T>C in the primary transcript. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.33
CADD	Pathogenic	26
DANN	Uncertain	1.0
Eigen	Uncertain	0.61
Eigen_PC	Uncertain	0.63
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.88	D;D;D
M_CAP	Pathogenic	0.72	D
MetaRNN	Pathogenic	0.92	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D;D
REVEL	Pathogenic	0.95
Sift4G	Uncertain	0.035	.;D;T
Vest4		0.80
MutPred		0.72		Loss of MoRF binding (P = 0.1254);Loss of MoRF binding (P = 0.1254);.;
MVP		0.36
ClinPred		0.71	D
GERP RS		5.0

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: rs1555217390; hg19: chr12-52082821;