12-51745960-G-C

Variant names:

• chr12-51745960-G-C
• rs373073046
• NM_001330260.2:c.2056G>C

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 3P and 0B. PM2 PP2

The NM_001330260.2(SCN8A):​c.2056G>C​(p.Asp686His) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,459,756 control chromosomes in the GnomAD database, with no homozygous occurrence. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D686Y) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 7.42
• 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: Uncertain_significance. The variant received 3 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.

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.2056G>C	p.Asp686His	missense	Exon 13 of 27	NP_001317189.1
	SCN8A	NM_014191.4	MANE Plus Clinical	c.2056G>C	p.Asp686His	missense	Exon 13 of 27	NP_055006.1
	SCN8A	NM_001177984.3		c.2056G>C	p.Asp686His	missense	Exon 13 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.2056G>C	p.Asp686His	missense	Exon 13 of 27	ENSP00000346534.4
	SCN8A	ENST00000627620.5	TSL:5 MANE Select	c.2056G>C	p.Asp686His	missense	Exon 13 of 27	ENSP00000487583.2
	SCN8A	ENST00000599343.5	TSL:5	c.2089G>C	p.Asp697His	missense	Exon 12 of 26	ENSP00000476447.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000808 AC: 2 AN: 247560 AF XY: 0.00000745

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: 0.0000178

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1459756 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 726068

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33384

American (AMR) AF: 0.00 AC: 0 AN: 44558

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26070

East Asian (EAS) AF: 0.00 AC: 0 AN: 39658

South Asian (SAS) AF: 0.00 AC: 0 AN: 85768

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53366

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5758

European-Non Finnish (NFE) AF: 9.00e-7 AC: 1 AN: 1110914

Other (OTH) AF: 0.00 AC: 0 AN: 60280

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

ExAC AF: 0.00000828 AC: 1

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.81
BayesDel_addAF	Uncertain	0.13	D
BayesDel_noAF	Uncertain	-0.030
CADD	Uncertain	26
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.83	D
Eigen	Uncertain	0.52
Eigen_PC	Uncertain	0.57
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.96	D
M_CAP	Uncertain	0.21	D
MetaRNN	Uncertain	0.47	T
MetaSVM	Pathogenic	0.87	D
MutationAssessor	Uncertain	2.8	M
PhyloP100		7.4
PrimateAI	Uncertain	0.63	T
PROVEAN	Pathogenic	-4.8	D
REVEL	Uncertain	0.63
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.017	D
Polyphen		0.14	B
Vest4		0.50
MutPred		0.48		Loss of solvent accessibility (P = 0.0169)
MVP		0.96
MPC		1.3
ClinPred		0.98	D
GERP RS		4.3
Varity_R		0.67
gMVP		0.80
Mutation Taster		=9/91	disease causing

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: rs373073046; hg19: chr12-52139744;