17-63963719-G-T

Variant names:

• chr17-63963719-G-T
• rs753391449
• NM_000334.4:c.1559C>A

Variant summary

Our verdict is Uncertain significance. The variant received 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_000334.4(SCN4A):​c.1559C>A​(p.Pro520Gln) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000069 in 1,448,814 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 16/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. P520L) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 34)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: SCN4A NM_000334.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.86
• Publications: 0 publications found

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]

SCN4A Gene-Disease associations (from GenCC):

• hyperkalemic periodic paralysis

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), G2P, Orphanet
• paramyotonia congenita of Von Eulenburg

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Laboratory for Molecular Medicine, Genomics England PanelApp, Labcorp Genetics (formerly Invitae), G2P, Orphanet
• SCN4A-related myopathy, autosomal recessive

  Inheritance: AR Classification: DEFINITIVE Submitted by: Illumina, ClinGen
• hypokalemic periodic paralysis, type 2

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae)
• potassium-aggravated myotonia

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• congenital myasthenic syndrome 16

  Inheritance: AR Classification: STRONG, LIMITED Submitted by: PanelApp Australia, Ambry Genetics, Genomics England PanelApp, Labcorp Genetics (formerly Invitae)
• congenital myopathy

  Inheritance: AR Classification: STRONG Submitted by: Genomics England PanelApp
• congenital myopathy 22A, classic

  Inheritance: AR Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• acetazolamide-responsive myotonia

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• hypokalemic periodic paralysis

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• myotonia fluctuans

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• myotonia permanens

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• postsynaptic congenital myasthenic syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

LOC105371858 (HGNC:):

ACMG classification

Our verdict: Uncertain_significance. The variant received 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 97 curated pathogenic missense variants (we use a threshold of 10). The gene has 19 curated benign missense variants. Gene score misZ: 1.5606 (below the threshold of 3.09). Trascript score misZ: 2.2224 (below the threshold of 3.09). GenCC associations: The gene is linked to congenital myasthenic syndrome 16, paramyotonia congenita of Von Eulenburg, hyperkalemic periodic paralysis, hypokalemic periodic paralysis, type 2, congenital myopathy, hypokalemic periodic paralysis, SCN4A-related myopathy, autosomal recessive, congenital myopathy 22A, classic, potassium-aggravated myotonia, postsynaptic congenital myasthenic syndrome, myotonia fluctuans, myotonia permanens, acetazolamide-responsive myotonia.
• BP4: Computational evidence support a benign effect (MetaRNN=0.114162594).

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000334.4. 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
	SCN4A	NM_000334.4	MANE Select	c.1559C>A	p.Pro520Gln	missense	Exon 10 of 24	NP_000325.4

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SCN4A	ENST00000435607.3	TSL:1 MANE Select	c.1559C>A	p.Pro520Gln	missense	Exon 10 of 24	ENSP00000396320.1

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome AF: 6.90e-7 AC: 1 AN: 1448814 Hom.: 0 Cov.: 34 AF XY: 0.00000139 AC XY: 1 AN XY: 719484

⚠️ 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: 33104

American (AMR) AF: 0.00 AC: 0 AN: 44120

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25918

East Asian (EAS) AF: 0.00 AC: 0 AN: 39036

South Asian (SAS) AF: 0.00 AC: 0 AN: 84934

European-Finnish (FIN) AF: 0.0000196 AC: 1 AN: 51098

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5330

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1105452

Other (OTH) AF: 0.00 AC: 0 AN: 59822

⚠️ 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.: 34

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Uncertain:1

Feb 10, 2020

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed in large population cohorts (Lek et al., 2016); In silico analysis supports that this missense variant does not alter protein structure/function; Has not been previously published as pathogenic or benign to our knowledge

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.080
BayesDel_addAF	Uncertain	0.064	T
BayesDel_noAF	Benign	-0.15
CADD	Benign	19
DANN	Benign	0.70
DEOGEN2	Benign	0.28	T
Eigen	Benign	-0.70
Eigen_PC	Benign	-0.56
FATHMM_MKL	Benign	0.43	N
LIST_S2	Benign	0.45	T
M_CAP	Benign	0.038	D
MetaRNN	Benign	0.11	T
MetaSVM	Benign	-0.34	T
MutationAssessor	Benign	0.37	N
PhyloP100		1.9
PrimateAI	Benign	0.39	T
PROVEAN	Benign	0.41	N
REVEL	Benign	0.26
Sift	Benign	0.78	T
Sift4G	Benign	0.12	T
Polyphen		0.0070	B
Vest4		0.20
MutPred		0.16		Loss of glycosylation at P520 (P = 0.0357)
MVP		0.72
MPC		0.24
ClinPred		0.12	T
GERP RS		2.9
Varity_R		0.057
gMVP		0.36

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: rs753391449; hg19: chr17-62041079;