rs778661227

Positions:

• chr17-63971780-C-T

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 0P and 2B. BP4_Moderate

The NM_000334.4(SCN4A):​c.553G>A​(p.Asp185Asn) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000415 in 1,612,694 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign 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. D185A) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.000020 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000044 (0 hom.)
• Consequence: SCN4A NM_000334.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:7 B:1
• Conservation: PhyloP100: 0.0590

Genes affected

SCN4A (HGNC:10591): (sodium voltage-gated channel alpha subunit 4) Voltage-gated sodium channels are transmembrane glycoprotein complexes composed of a large alpha subunit with 24 transmembrane domains and one or more regulatory beta subunits. They are responsible for the generation and propagation of action potentials in neurons and muscle. This gene encodes one member of the sodium channel alpha subunit gene family. It is expressed in skeletal muscle, and mutations in this gene have been linked to several myotonia and periodic paralysis disorders. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.18770996).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SCN4A	NM_000334.4	c.553G>A	p.Asp185Asn	missense_variant	4/24	ENST00000435607.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SCN4A	ENST00000435607.3	c.553G>A	p.Asp185Asn	missense_variant	4/24	1	NM_000334.4	P1

Frequencies

GnomAD3 genomes AF: 0.0000263 AC: 4 AN: 152040 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000483

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0000655

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: 0.00

Gnomad OTH AF: 0.000478

GnomAD3 exomes AF: 0.0000487 AC: 12 AN: 246640 Hom.: 0 AF XY: 0.0000448 AC XY: 6 AN XY: 133896

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000585

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.000132

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000179

Gnomad OTH exome AF: 0.000667

GnomAD4 exome AF: 0.0000438 AC: 64 AN: 1460536 Hom.: 0 Cov.: 33 AF XY: 0.0000537 AC XY: 39 AN XY: 726486

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000674

Gnomad4 ASJ exome AF: 0.0000766

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.000151

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000306

Gnomad4 OTH exome AF: 0.000133

GnomAD4 genome AF: 0.0000197 AC: 3 AN: 152158 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74386

Gnomad4 AFR AF: 0.0000482

Gnomad4 AMR AF: 0.0000655

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000132 Hom.: 0

Bravo AF: 0.0000756

ExAC AF: 0.0000744 AC: 9

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:7 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hyperkalemic periodic paralysis Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Dec 25, 2023	This sequence change replaces aspartic acid, which is acidic and polar, with asparagine, which is neutral and polar, at codon 185 of the SCN4A protein (p.Asp185Asn). This variant is present in population databases (rs778661227, gnomAD 0.01%). This variant has not been reported in the literature in individuals affected with SCN4A-related conditions. ClinVar contains an entry for this variant (Variation ID: 197134). 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 SCN4A 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. -
Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jan 13, 2018	This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Athena Diagnostics	Mar 26, 2019	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Feb 05, 2015	- -

Hypokalemic periodic paralysis, type 2 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Paramyotonia congenita of Von Eulenburg Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Congenital myasthenic syndrome 16 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Potassium-aggravated myotonia Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as likely benign is not then subjected to further curation. The score for this variant resulted in a classification of likely benign for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.090
BayesDel_addAF	Benign	-0.25	T
BayesDel_noAF	Benign	-0.36
CADD	Benign	15
DANN	Uncertain	0.98
DEOGEN2	Uncertain	0.78	D
Eigen	Benign	-0.92
Eigen_PC	Benign	-0.93
FATHMM_MKL	Benign	0.057	N
LIST_S2	Benign	0.63	T
M_CAP	Benign	0.067	D
MetaRNN	Benign	0.19	T
MetaSVM	Uncertain	0.48	D
MutationAssessor	Benign	1.4	L
MutationTaster	Benign	1.0	N;N
PrimateAI	Benign	0.38	T
PROVEAN	Benign	-2.2	N
REVEL	Benign	0.24
Sift	Benign	0.095	T
Sift4G	Benign	0.23	T
Polyphen		0.018	B
Vest4		0.27
MutPred		0.50		Loss of loop (P = 0.0804);
MVP		0.51
MPC		0.25
ClinPred		0.016	T
GERP RS		1.5
Varity_R		0.073
gMVP		0.67

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

LitVar

Other links and lift over

dbSNP: rs778661227; hg19: chr17-62049140; COSMIC: COSV71128369; COSMIC: COSV71128369;