12-51807247-A-G

Variant names:

• chr12-51807247-A-G
• rs368796221
• NM_001330260.2:c.5761A>G

Variant summary

Our verdict is Likely benign. The variant received -5 ACMG points: 1P and 6B. PP2 BP4_Moderate BS2

The NM_001330260.2(SCN8A):​c.5761A>G​(p.Thr1921Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000753 in 1,461,712 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 17/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T1921P) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000075 (0 hom.)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 1.01
• Publications: 1 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: Likely_benign. The variant received -5 ACMG points.

• 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.
• BP4: Computational evidence support a benign effect (MetaRNN=0.08590457).
• BS2: High AC in GnomAdExome4 at 11 AD gene.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001330260.2. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SCN8A	NM_001330260.2	MANE Select	c.5761A>G	p.Thr1921Ala	missense	Exon 27 of 27	NP_001317189.1
	SCN8A	NM_014191.4	MANE Plus Clinical	c.5761A>G	p.Thr1921Ala	missense	Exon 27 of 27	NP_055006.1
	SCN8A	NM_001177984.3		c.5638A>G	p.Thr1880Ala	missense	Exon 26 of 26	NP_001171455.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SCN8A	ENST00000354534.11	TSL:1 MANE Plus Clinical	c.5761A>G	p.Thr1921Ala	missense	Exon 27 of 27	ENSP00000346534.4
	SCN8A	ENST00000627620.5	TSL:5 MANE Select	c.5761A>G	p.Thr1921Ala	missense	Exon 27 of 27	ENSP00000487583.2
	SCN8A	ENST00000599343.5	TSL:5	c.5794A>G	p.Thr1932Ala	missense	Exon 26 of 26	ENSP00000476447.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000802 AC: 2 AN: 249240 AF XY: 0.0000148

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000753 AC: 11 AN: 1461712 Hom.: 0 Cov.: 33 AF XY: 0.0000124 AC XY: 9 AN XY: 727138

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.0000812 AC: 7 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53402

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111870

Other (OTH) AF: 0.0000663 AC: 4 AN: 60374

GnomAD4 genome Cov.: 32

ExAC AF: 0.0000165 AC: 2

Asia WGS AF: 0.000577 AC: 2 AN: 3478

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cognitive impairment with or without cerebellar ataxia Uncertain:1

Apr 23, 2020

Baylor Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was determined to be of uncertain significance according to ACMG Guidelines, 2015 [PMID:25741868].

Developmental and epileptic encephalopathy Uncertain:1

Mar 24, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces threonine, which is neutral and polar, with alanine, which is neutral and non-polar, at codon 1921 of the SCN8A protein (p.Thr1921Ala). This variant is present in population databases (rs368796221, gnomAD 0.006%). This variant has not been reported in the literature in individuals affected with SCN8A-related conditions. ClinVar contains an entry for this variant (Variation ID: 1029255). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt SCN8A protein function with a negative predictive value of 95%. 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.

not provided Uncertain:1

Breakthrough Genomics, Breakthrough Genomics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: not provided

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.055
BayesDel_addAF	Benign	-0.22	T
BayesDel_noAF	Benign	-0.37
CADD	Benign	11
DANN	Benign	0.84
DEOGEN2	Benign	0.28	T
Eigen	Benign	-0.87
Eigen_PC	Benign	-0.73
FATHMM_MKL	Benign	0.048	N
LIST_S2	Benign	0.76	T
M_CAP	Benign	0.032	D
MetaRNN	Benign	0.086	T
MetaSVM	Benign	-0.43	T
MutationAssessor	Benign	0.0	N
PhyloP100		1.0
PrimateAI	Benign	0.36	T
PROVEAN	Benign	0.040	N
REVEL	Benign	0.21
Sift	Benign	0.25	T
Sift4G	Benign	0.67	T
Polyphen		0.0	B
Vest4		0.026
MutPred		0.22		Loss of phosphorylation at T1921 (P = 0.0351)
MVP		0.61
MPC		1.0
ClinPred		0.95	D
GERP RS		1.4
Varity_R		0.028
gMVP		0.61
Mutation Taster		=94/6	polymorphism

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: rs368796221; hg19: chr12-52201031;