NM_001330260.2:c.779T>C

Variant names:

• chr12-51699642-T-C
• rs879255697
• NM_001330260.2:c.779T>C

Variant summary

Our verdict is Pathogenic. The variant received 13 ACMG points: 13P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Moderate

The NM_001330260.2(SCN8A):​c.779T>C​(p.Phe260Ser) 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. 13/22 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. F260V) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 31)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1 O:1
• Conservation: PhyloP100: 8.02
• Publications: 10 publications found

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]

SCN8A Gene-Disease associations (from GenCC):

• complex neurodevelopmental disorder

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• developmental and epileptic encephalopathy, 13

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P, Ambry Genetics
• cognitive impairment with or without cerebellar ataxia

  Inheritance: AD Classification: STRONG Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
• seizures, benign familial infantile, 5

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• benign familial infantile epilepsy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• infantile convulsions and choreoathetosis

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• undetermined early-onset epileptic encephalopathy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• myoclonus, familial, 2

  Inheritance: AD Classification: LIMITED Submitted by: Ambry Genetics

ACMG classification

Our verdict: Pathogenic. The variant received 13 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 2 uncertain 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 chr12-51699641-T-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 1803066.Status of the report is criteria_provided_single_submitter, 1 stars.
• 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, developmental and epileptic encephalopathy, 13, undetermined early-onset epileptic encephalopathy, benign familial infantile epilepsy, complex neurodevelopmental disorder, seizures, benign familial infantile, 5, cognitive impairment with or without cerebellar ataxia, infantile convulsions and choreoathetosis.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.96
• PP5: Variant 12-51699642-T-C is Pathogenic according to our data. Variant chr12-51699642-T-C is described in ClinVar as [Pathogenic]. Clinvar id is 253279.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN8A	NM_001330260.2	c.779T>C	p.Phe260Ser	missense_variant	Exon 7 of 27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.779T>C	p.Phe260Ser	missense_variant	Exon 7 of 27	ENST00000354534.11	NP_055006.1
SCN8A	NM_001177984.3	c.779T>C	p.Phe260Ser	missense_variant	Exon 7 of 26		NP_001171455.1
SCN8A	NM_001369788.1	c.779T>C	p.Phe260Ser	missense_variant	Exon 7 of 26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000354534.11	c.779T>C	p.Phe260Ser	missense_variant	Exon 7 of 27	1	NM_014191.4	ENSP00000346534.4
SCN8A	ENST00000627620.5	c.779T>C	p.Phe260Ser	missense_variant	Exon 7 of 27	5	NM_001330260.2	ENSP00000487583.2
SCN8A	ENST00000599343.5	c.779T>C	p.Phe260Ser	missense_variant	Exon 6 of 26	5		ENSP00000476447.3
SCN8A	ENST00000355133.7	c.779T>C	p.Phe260Ser	missense_variant	Exon 6 of 25	1		ENSP00000347255.4

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1 Other:1

Revision: criteria provided, single submitter

Submissions by phenotype

Developmental and epileptic encephalopathy Pathogenic:1

Jan 24, 2020

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces phenylalanine with serine at codon 260 of the SCN8A protein (p.Phe260Ser). The phenylalanine residue is highly conserved and there is a large physicochemical difference between phenylalanine and serine. This variant is not present in population databases (ExAC no frequency). This variant has been observed in individual(s) with clinical features of early infantile epileptic encephalopathy (PMID: 25568300, Invitae). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 253279). 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"). For these reasons, this variant has been classified as Pathogenic. -

Developmental and epileptic encephalopathy, 13 Other:1

-

GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	.;D;.;.;.;.;.
Eigen	Pathogenic	0.91
Eigen_PC	Pathogenic	0.79
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	0.98	D;D;D;.;D;D;D
M_CAP	Pathogenic	0.94	D
MetaRNN	Pathogenic	0.96	D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	4.3	.;H;H;H;H;H;.
PhyloP100		8.0
PrimateAI	Pathogenic	0.93	D
PROVEAN	Pathogenic	-7.8	.;D;D;D;.;.;D
REVEL	Pathogenic	0.99
Sift	Pathogenic	0.0	.;D;D;D;.;.;D
Sift4G	Pathogenic	0.0	.;D;D;D;D;D;D
Polyphen		0.92, 1.0	.;P;.;.;D;.;.
Vest4		0.92, 0.97, 0.97, 0.98, 0.97
MutPred		0.80		Loss of stability (P = 0.0539);Loss of stability (P = 0.0539);Loss of stability (P = 0.0539);Loss of stability (P = 0.0539);Loss of stability (P = 0.0539);Loss of stability (P = 0.0539);.;
MVP		0.99
MPC		2.7
ClinPred		1.0	D
GERP RS		4.5
Varity_R		0.98
gMVP		0.98
Mutation Taster		=2/98	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs879255697; hg19: chr12-52093426;