Genetic Variant SCN1A:p.His127Asp (chr2-166058574-G-C) – ACMG Classification: Uncertain_significance (2 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 7P and 5B. PM1PM5PP2PP3_ModerateBP6BS2

The NM_001165963.4(SCN1A):c.379C>G(p.His127Asp) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00015 in 1,548,624 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). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. H127Y) has been classified as Likely pathogenic.

Frequency

Genomes: 𝑓 0.00011 ( 0 hom., cov: 32)

Exomes 𝑓: 0.00015 ( 0 hom. )

Consequence

SCN1A
NM_001165963.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:5B:3

Conservation

PhyloP100: 10.0

Publications

11 publications found

Variant links:

Genes affected

SCN1A (HGNC:10585): (sodium voltage-gated channel alpha subunit 1) Voltage-dependent sodium channels are heteromeric complexes that regulate sodium exchange between intracellular and extracellular spaces and are essential for the generation and propagation of action potentials in muscle cells and neurons. Each sodium channel is composed of a large pore-forming, glycosylated alpha subunit and two smaller beta subunits. This gene encodes a sodium channel alpha subunit, which has four homologous domains, each of which contains six transmembrane regions. Allelic variants of this gene are associated with generalized epilepsy with febrile seizures and epileptic encephalopathy. Alternative splicing results in multiple transcript variants. The RefSeq Project has decided to create four representative RefSeq records. Three of the transcript variants are supported by experimental evidence and the fourth contains alternate 5' untranslated exons, the exact combination of which have not been experimentally confirmed for the full-length transcript. [provided by RefSeq, Oct 2015]

SCN1A links:

SCN1A-AS1 (HGNC:54069): (SCN1A and SCN9A antisense RNA 1)

SCN1A-AS1 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

PM1

In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 18 uncertain in NM_001165963.4

PM5

Other missense variant is known to change same aminoacid residue: Variant chr2-166058574-G-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 582634.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

PP2

Missense variant in the SCN1A gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 848 curated pathogenic missense variants (we use a threshold of 10). The gene has 89 curated benign missense variants. Gene score misZ: 5.2206 (above the threshold of 3.09). Trascript score misZ: 7.6022 (above the threshold of 3.09). GenCC associations: The gene is linked to familial or sporadic hemiplegic migraine, myoclonic-astatic epilepsy, arthrogryposis, Dravet syndrome, malignant migrating partial seizures of infancy, generalized epilepsy with febrile seizures plus, type 2, migraine, familial hemiplegic, 3, developmental and epileptic encephalopathy, 6A, familial hemiplegic migraine, generalized epilepsy with febrile seizures plus, genetic developmental and epileptic encephalopathy, Lennox-Gastaut syndrome.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.878

BP6

Variant 2-166058574-G-C is Benign according to our data. Variant chr2-166058574-G-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 195131.

BS2

High AC in GnomAd4 at 16 AD,Unknown gene.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001165963.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
SCN1A	NM_001165963.4	MANE Select	c.379C>G	p.His127Asp	missense	Exon 5 of 29	NP_001159435.1
SCN1A	NM_001202435.3		c.379C>G	p.His127Asp	missense	Exon 4 of 28	NP_001189364.1
SCN1A	NM_001353948.2		c.379C>G	p.His127Asp	missense	Exon 3 of 27	NP_001340877.1

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
SCN1A	ENST00000674923.1	MANE Select	c.379C>G	p.His127Asp	missense	Exon 5 of 29	ENSP00000501589.1
SCN1A	ENST00000303395.9	TSL:5	c.379C>G	p.His127Asp	missense	Exon 4 of 28	ENSP00000303540.4
SCN1A	ENST00000375405.7	TSL:5	c.379C>G	p.His127Asp	missense	Exon 2 of 26	ENSP00000364554.3

Frequencies

GnomAD3 genomes

AF:

0.000105

AC:

AN:

151998

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000724

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.000191

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.0000678

AC:

AN:

250644

AF XY:

0.0000443

show subpopulations

Gnomad AFR exome

AF:

0.0000618

Gnomad AMR exome

AF:

0.0000290

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.000132

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.000155

AC:

216

AN:

1396626

Hom.:

Cov.:

AF XY:

0.000156

AC XY:

109

AN XY:

698776

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

31906

American (AMR)

AF:

0.0000224

AC:

AN:

44594

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25706

East Asian (EAS)

AF:

0.00

AC:

AN:

39248

South Asian (SAS)

AF:

0.00

AC:

AN:

84854

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53288

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5656

European-Non Finnish (NFE)

AF:

0.000197

AC:

208

AN:

1053358

Other (OTH)

AF:

0.000121

AC:

AN:

58016

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.472

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.000105

AC:

AN:

151998

Hom.:

Cov.:

AF XY:

0.0000808

AC XY:

AN XY:

74234

show subpopulations

African (AFR)

AF:

0.0000724

AC:

AN:

41408

American (AMR)

AF:

0.00

AC:

AN:

15238

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5180

South Asian (SAS)

AF:

0.00

AC:

AN:

4826

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10602

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.000191

AC:

AN:

67954

Other (OTH)

AF:

0.00

AC:

AN:

2090

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.466

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.000279

Hom.:

Bravo

AF:

0.0000945

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000116

AC:

ExAC

AF:

0.0000577

AC:

EpiCase

AF:

0.000273

EpiControl

AF:

0.000297

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:5Benign:3

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not provided

Uncertain:4Benign:1

Diagnostic Laboratory, Department of Genetics, University Medical Center Groningen

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

Oct 01, 2023

CeGaT Center for Human Genetics Tuebingen

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

SCN1A: PM5, PP3, BS2

Mar 12, 2015

Eurofins Ntd Llc (ga)

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Apr 24, 2025

GeneDx

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Reported as an apparently de novo change in an individual with clinical features of borderline Dravet syndrome; however, paternity was not established. In the same paper, p.H127D was identified in another individual with classic Dravet syndrome who had another missense variant (p.P1451S) in SCN1A (PMID: 21248271); This substitution is predicted to be in the N-terminal cytoplasmic domain; In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 20831750, 28150151, 28202706, 29655203, 32090326, 32725632, 34598035, 35074891, 21248271, 39168079, 38410936, 37194601, 35711923)

Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

Severe myoclonic epilepsy in infancy;C1858673:Generalized epilepsy with febrile seizures plus, type 2;C1864987:Migraine, familial hemiplegic, 3

Uncertain:1

Oct 31, 2018

Fulgent Genetics, Fulgent Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Developmental and epileptic encephalopathy

Benign:1

Sep 10, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

SCN1A-related disorder

Benign:1

Aug 09, 2024

PreventionGenetics, part of Exact Sciences

Significance:Likely benign

Review Status:no assertion criteria provided

Collection Method:clinical testing

This variant is classified as likely benign based on ACMG/AMP sequence variant interpretation guidelines (Richards et al. 2015 PMID: 25741868, with internal and published modifications).

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.95

BayesDel_addAF

Pathogenic

0.37

BayesDel_noAF

Pathogenic

0.54

CADD

Pathogenic

(source)

DANN

Uncertain

0.99

DEOGEN2

Pathogenic

0.87

Eigen

Uncertain

0.37

Eigen_PC

Uncertain

0.47

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Uncertain

0.90

M_CAP

Pathogenic

0.69

MetaRNN

Pathogenic

0.88

MetaSVM

Pathogenic

0.87

MutationAssessor

Pathogenic

3.5

PhyloP100

PrimateAI

Pathogenic

0.87

PROVEAN

Pathogenic

-7.5

REVEL

Pathogenic

0.75

Sift

Uncertain

0.0010

Sift4G

Uncertain

0.011

Polyphen

0.0010

Vest4

0.94

MVP

0.99

MPC

0.93

ClinPred

0.92

GERP RS

4.8

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.89

gMVP

0.99

Mutation Taster

=3/97

disease causing

(source)

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over