rs121908545

chr17-63941939-C-Achr17-63941939-C-Gchr17-63941939-C-T

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP3_Strong PP5

The NM_000334.4(SCN4A):c.4343G>T(p.Arg1448Leu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging 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. R1448S) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 31)
• Consequence: SCN4A NM_000334.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 7.91

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 Pathogenic. Variant got 11 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 9 uncertain in NM_000334.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr17-63941940-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 5898.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.994
• PP5: Variant 17-63941939-C-A is Pathogenic according to our data. Variant chr17-63941939-C-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 586518.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=2, Uncertain_significance=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SCN4A	NM_000334.4	c.4343G>T	p.Arg1448Leu	missense_variant	24/24	ENST00000435607.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SCN4A	ENST00000435607.3	c.4343G>T	p.Arg1448Leu	missense_variant	24/24	1	NM_000334.4	P1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 35

GnomAD4 genome Cov.: 31

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:1 Uncertain:1

Likely pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Sep 06, 2019	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Athena Diagnostics	Oct 31, 2017	- -

Hyperkalemic periodic paralysis Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Invitae

Apr 11, 2022

Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. This sequence change replaces arginine, which is basic and polar, with leucine, which is neutral and non-polar, at codon 1448 of the SCN4A protein (p.Arg1448Leu). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with clinical features of paramyotonia congenita (PMID: 18166706; Invitae). ClinVar contains an entry for this variant (Variation ID: 586518). This variant disrupts the p.Arg1448 amino acid residue in SCN4A. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 1316765, 7809121, 8005599, 16801039). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
Cadd	Pathogenic	27
Dann	Uncertain	1.0
DEOGEN2	Pathogenic	0.97	D
Eigen	Pathogenic	0.83
Eigen_PC	Pathogenic	0.67
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.92	D
M_CAP	Pathogenic	0.78	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.4	M
MutationTaster	Benign	1.0	D;D
PrimateAI	Pathogenic	0.88	D
PROVEAN	Pathogenic	-6.5	D
REVEL	Pathogenic	0.98
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.032	D
Polyphen		1.0	D
Vest4		0.94
MutPred		0.97		Loss of MoRF binding (P = 0.0329);
MVP		0.98
MPC		0.91
ClinPred		1.0	D
GERP RS		3.7
Varity_R		0.94
gMVP		0.93

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: rs121908545; hg19: chr17-62019299;