12-51806532-C-G

Variant names:

• chr12-51806532-C-G
• rs376759643
• NM_001330260.2:c.5046C>G

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM2 PP2 PP3_Moderate PP5

The NM_001330260.2(SCN8A):​c.5046C>G​(p.Ile1682Met) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,894 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. I1682I) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: -6.58
• Publications: 0 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_pathogenic. The variant received 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• 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, 0.872
• PP5: Variant 12-51806532-C-G is Pathogenic according to our data. Variant chr12-51806532-C-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 3775337.

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.5046C>G	p.Ile1682Met	missense	Exon 27 of 27	NP_001317189.1
	SCN8A	NM_014191.4	MANE Plus Clinical	c.5046C>G	p.Ile1682Met	missense	Exon 27 of 27	NP_055006.1
	SCN8A	NM_001177984.3		c.4923C>G	p.Ile1641Met	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.5046C>G	p.Ile1682Met	missense	Exon 27 of 27	ENSP00000346534.4
	SCN8A	ENST00000627620.5	TSL:5 MANE Select	c.5046C>G	p.Ile1682Met	missense	Exon 27 of 27	ENSP00000487583.2
	SCN8A	ENST00000599343.5	TSL:5	c.5079C>G	p.Ile1693Met	missense	Exon 26 of 26	ENSP00000476447.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461894 Hom.: 0 Cov.: 33 AF XY: 0.00000138 AC XY: 1 AN XY: 727248

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: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

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

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1112012

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

SCN8A-related disorder Pathogenic:1

Jul 22, 2024

3billion

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The variant is observed at an extremely low frequency in the gnomAD v4.0.0 dataset (total allele frequency: <0.001%). Predicted Consequence/Location: The variant is located in a mutational hot spot and/or well-established functional domain in which established pathogenic variants have been reported (PMID: 27270488, 35188110). Missense changes are a common disease-causing mechanism. In silico tool predictions suggest damaging effect of the variant on gene or gene product [REVEL: 0.73 (>=0.6, sensitivity 0.68 and specificity 0.92)]. The same nucleotide change resulting in the same amino acid change has been previously reported to be associated with SCN8A related disorder (3billion dataset). Therefore, this variant is classified as Likely pathogenic according to the recommendation of ACMG/AMP guideline.

not provided Uncertain:1

Nov 07, 2024

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Has not been previously published as pathogenic or benign to our knowledge; Extracellular loop between the S5 and S6 transmembrane segments of the fourth homologous domain

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.60
BayesDel_addAF	Pathogenic	0.33	D
BayesDel_noAF	Pathogenic	0.24
CADD	Benign	1.7
DANN	Benign	0.97
DEOGEN2	Pathogenic	0.96	D
Eigen	Benign	-0.75
Eigen_PC	Benign	-1.1
FATHMM_MKL	Benign	0.042	N
LIST_S2	Uncertain	0.95	D
M_CAP	Pathogenic	0.78	D
MetaRNN	Pathogenic	0.87	D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Uncertain	2.9	M
PhyloP100		-6.6
PrimateAI	Pathogenic	0.86	D
PROVEAN	Uncertain	-2.7	D
REVEL	Pathogenic	0.73
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.013	D
Polyphen		0.99	D
Vest4		0.75
MutPred		0.64		Gain of disorder (P = 0.0789)
MVP		0.94
MPC		2.2
ClinPred		0.99	D
GERP RS		-11
Varity_R		0.71
gMVP		0.96
Mutation Taster		=63/37	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs376759643; hg19: chr12-52200316;