NM_001330260.2:c.19G>T

Variant names:

• chr12-51662836-G-T
• rs896109778
• NM_001330260.2:c.19G>T

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 3P and 1B. PM2 PP2 BP4

The NM_001330260.2(SCN8A):​c.19G>T​(p.Ala7Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,538 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 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. A7P) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: SCN8A NM_001330260.2 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 7.99
• 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 2 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.
• BP4: Computational evidence support a benign effect (MetaRNN=0.42341936).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN8A	NM_001330260.2	c.19G>T	p.Ala7Ser	missense_variant	Exon 2 of 27	ENST00000627620.5	NP_001317189.1
SCN8A	NM_014191.4	c.19G>T	p.Ala7Ser	missense_variant	Exon 2 of 27	ENST00000354534.11	NP_055006.1
SCN8A	NM_001177984.3	c.19G>T	p.Ala7Ser	missense_variant	Exon 2 of 26		NP_001171455.1
SCN8A	NM_001369788.1	c.19G>T	p.Ala7Ser	missense_variant	Exon 2 of 26		NP_001356717.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN8A	ENST00000354534.11	c.19G>T	p.Ala7Ser	missense_variant	Exon 2 of 27	1	NM_014191.4	ENSP00000346534.4
SCN8A	ENST00000627620.5	c.19G>T	p.Ala7Ser	missense_variant	Exon 2 of 27	5	NM_001330260.2	ENSP00000487583.2
SCN8A	ENST00000599343.5	c.19G>T	p.Ala7Ser	missense_variant	Exon 1 of 26	5		ENSP00000476447.3
SCN8A	ENST00000355133.7	c.19G>T	p.Ala7Ser	missense_variant	Exon 1 of 25	1		ENSP00000347255.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461538 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727036

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

African (AFR) AF: 0.0000299 AC: 1 AN: 33470

American (AMR) AF: 0.00 AC: 0 AN: 44720

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

East Asian (EAS) AF: 0.00 AC: 0 AN: 39696

South Asian (SAS) AF: 0.00 AC: 0 AN: 86250

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53344

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5764

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111788

Other (OTH) AF: 0.00 AC: 0 AN: 60370

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.18
BayesDel_addAF	Pathogenic	0.21	D
BayesDel_noAF	Uncertain	0.060
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Benign	0.32	.;T;.;.;.;.
Eigen	Uncertain	0.66
Eigen_PC	Pathogenic	0.68
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.86	D;D;D;.;D;D
M_CAP	Uncertain	0.14	D
MetaRNN	Benign	0.42	T;T;T;T;T;T
MetaSVM	Pathogenic	0.82	D
MutationAssessor	Benign	0.69	.;N;N;N;N;N
PhyloP100		8.0
PrimateAI	Uncertain	0.65	T
PROVEAN	Benign	-1.1	.;N;N;N;.;.
REVEL	Uncertain	0.47
Sift	Benign	0.046	.;D;D;D;.;.
Sift4G	Benign	0.22	.;T;T;T;T;T
Polyphen		0.99	.;D;.;.;.;.
Vest4		0.45, 0.47, 0.48, 0.44
MutPred		0.20		Gain of phosphorylation at A7 (P = 0.0048);Gain of phosphorylation at A7 (P = 0.0048);Gain of phosphorylation at A7 (P = 0.0048);Gain of phosphorylation at A7 (P = 0.0048);Gain of phosphorylation at A7 (P = 0.0048);Gain of phosphorylation at A7 (P = 0.0048);
MVP		0.91
MPC		1.6
ClinPred		0.94	D
GERP RS		5.0
PromoterAI		0.054	Neutral
Varity_R		0.17
gMVP		0.68
Mutation Taster		=45/55	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: rs896109778; hg19: chr12-52056620;