chr17-63948763-A-C

Variant names:

• chr17-63948763-A-C
• rs1555601897
• NM_000334.4:c.2992T>G

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM2 PP2 PP3_Strong

The NM_000334.4(SCN4A):​c.2992T>G​(p.Cys998Gly) variant causes a missense, splice region change. The variant allele was found at a frequency of 0.000000689 in 1,451,008 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 1/1 splice prediction tools predict no significant impact on normal splicing. 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. C998R) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: SCN4A NM_000334.4 missense, splice_region
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 6.02
• 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

ACMG classification

Our verdict: Likely_pathogenic. The variant received 7 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.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.978

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SCN4A	NM_000334.4	c.2992T>G	p.Cys998Gly	missense_variant, splice_region_variant	Exon 16 of 24	ENST00000435607.3	NP_000325.4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SCN4A	ENST00000435607.3	c.2992T>G	p.Cys998Gly	missense_variant, splice_region_variant	Exon 16 of 24	1	NM_000334.4	ENSP00000396320.1
SCN4A	ENST00000584310.1	n.315T>G		splice_region_variant, non_coding_transcript_exon_variant	Exon 2 of 3	4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.89e-7 AC: 1 AN: 1451008 Hom.: 0 Cov.: 31 AF XY: 0.00000139 AC XY: 1 AN XY: 720362

African (AFR) AF: 0.00 AC: 0 AN: 33328

American (AMR) AF: 0.00 AC: 0 AN: 44462

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25818

East Asian (EAS) AF: 0.00 AC: 0 AN: 39430

South Asian (SAS) AF: 0.00 AC: 0 AN: 85724

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 51690

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5740

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1104908

Other (OTH) AF: 0.0000167 AC: 1 AN: 59908

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.85
BayesDel_addAF	Pathogenic	0.29	D
BayesDel_noAF	Pathogenic	0.18
CADD	Uncertain	24
DANN	Uncertain	0.97
DEOGEN2	Pathogenic	0.84	D
Eigen	Uncertain	0.30
Eigen_PC	Uncertain	0.28
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Pathogenic	0.98	D
M_CAP	Pathogenic	0.48	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Uncertain	0.63	D
MutationAssessor	Pathogenic	3.8	H
PhyloP100		6.0
PrimateAI	Uncertain	0.69	T
PROVEAN	Pathogenic	-11	D
REVEL	Pathogenic	0.79
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.0030	D
Polyphen		0.51	P
Vest4		0.96
MutPred		0.82		Gain of loop (P = 0.0079);
MVP		0.87
MPC		1.0
ClinPred		1.0	D
GERP RS		4.2
Varity_R		0.99
gMVP		0.76

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1555601897; hg19: chr17-62026123;