NM_000083.3:c.1357C>T

Variant names:

Variant summary

Our verdict is Uncertain significance. The variant received 1 ACMG points: 1P and 0B. PP2

The NM_000083.3(CLCN1):c.1357C>T(p.Arg453Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000836 in 1,614,118 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. R453Q) has been classified as Likely benign.

Frequency

Genomes: 𝑓 0.00013 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000079 ( 0 hom. )

Consequence

CLCN1
NM_000083.3 missense

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:4

Conservation

PhyloP100: 0.318

Publications

10 publications found

Variant links:

Genes affected

CLCN1 (HGNC:2019): (chloride voltage-gated channel 1) The CLCN family of voltage-dependent chloride channel genes comprises nine members (CLCN1-7, Ka and Kb) which demonstrate quite diverse functional characteristics while sharing significant sequence homology. The protein encoded by this gene regulates the electric excitability of the skeletal muscle membrane. Mutations in this gene cause two forms of inherited human muscle disorders: recessive generalized myotonia congenita (Becker) and dominant myotonia (Thomsen). Alternative splicing results in multiple transcript variants. [provided by RefSeq, Mar 2012]

CLCN1 Gene-Disease associations (from GenCC):

myotonia congenita, autosomal dominant
Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae)
myotonia congenita, autosomal recessive
Inheritance: AR Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp
Thomsen and Becker disease
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

CLCN1 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

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

PP2

Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 106 curated pathogenic missense variants (we use a threshold of 10). The gene has 18 curated benign missense variants. Gene score misZ: 0.21191 (below the threshold of 3.09). Trascript score misZ: 0.95247 (below the threshold of 3.09). GenCC associations: The gene is linked to myotonia congenita, autosomal dominant, myotonia congenita, autosomal recessive, Thomsen and Becker disease.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CLCN1	NM_000083.3 link	c.1357C>T	p.Arg453Trp	missense_variant	Exon 12 of 23	ENST00000343257.7	NP_000074.3	P35523
CLCN1	NR_046453.2 link	n.1356+326C>T		intron_variant	Intron 11 of 21

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	UniProt
CLCN1	ENST00000343257.7 link	c.1357C>T	p.Arg453Trp	missense_variant	Exon 12 of 23	1	NM_000083.3	ENSP00000339867.2	P35523
CLCN1	ENST00000432192.6 link	n.*642C>T		non_coding_transcript_exon_variant	Exon 12 of 23	1		ENSP00000395949.2	H7C0N6
CLCN1	ENST00000432192.6 link	n.*642C>T		3_prime_UTR_variant	Exon 12 of 23	1		ENSP00000395949.2	H7C0N6
CLCN1	ENST00000650516.2 link	c.1357C>T	p.Arg453Trp	missense_variant	Exon 12 of 23			ENSP00000498052.2	A0A3B3IU72

Frequencies

GnomAD3 genomes

AF:

0.000131

AC:

AN:

152132

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000966

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00173

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.000414

Gnomad FIN

AF:

0.0000943

Gnomad MID

AF:

0.00633

Gnomad NFE

AF:

0.0000735

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.0000795

AC:

AN:

251452

AF XY:

0.0000883

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.000794

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.0000462

Gnomad NFE exome

AF:

0.0000703

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000787

AC:

115

AN:

1461868

Hom.:

Cov.:

AF XY:

0.0000839

AC XY:

AN XY:

727244

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33478

American (AMR)

AF:

0.00

AC:

AN:

44724

Ashkenazi Jewish (ASJ)

AF:

0.000612

AC:

AN:

26136

East Asian (EAS)

AF:

0.00

AC:

AN:

39700

South Asian (SAS)

AF:

0.000209

AC:

AN:

86258

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53420

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.0000683

AC:

AN:

1111990

Other (OTH)

AF:

0.0000828

AC:

AN:

60394

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.478

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:

0.000131

AC:

AN:

152250

Hom.:

Cov.:

AF XY:

0.000161

AC XY:

AN XY:

74434

show subpopulations

African (AFR)

AF:

0.0000963

AC:

AN:

41544

American (AMR)

AF:

0.00

AC:

AN:

15292

Ashkenazi Jewish (ASJ)

AF:

0.00173

AC:

AN:

3470

East Asian (EAS)

AF:

0.00

AC:

AN:

5188

South Asian (SAS)

AF:

0.000414

AC:

AN:

4826

European-Finnish (FIN)

AF:

0.0000943

AC:

AN:

10602

Middle Eastern (MID)

AF:

0.00680

AC:

AN:

294

European-Non Finnish (NFE)

AF:

0.0000735

AC:

AN:

68018

Other (OTH)

AF:

0.00

AC:

AN:

2108

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.458

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:

0.0000815

Hom.:

Bravo

AF:

0.0000831

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000116

AC:

ExAC

AF:

0.0000906

AC:

EpiCase

AF:

0.000109

EpiControl

AF:

0.000178

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not provided

Uncertain:2

May 15, 2025

GeneDx

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

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: 23739125, 26007199, 34426522, 28427807, 32154989) -

Sep 19, 2022

Revvity Omics, Revvity

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

not specified

Uncertain:1

Dec 07, 2023

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Variant summary: CLCN1 c.1357C>T (p.Arg453Trp) results in a non-conservative amino acid change in the encoded protein sequence. Three of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 8e-05 in 251452 control chromosomes (gnomAD). This frequency is not significantly higher than estimated for a pathogenic variant in CLCN1 causing Myotonia congenita (8e-05 vs 0.0035), allowing no conclusion about variant significance. c.1357C>T has been reported in the literature in individuals affected with Myotonia congenita (e.g. Brugnoni_2013, Portaro_2015). These data do not allow any conclusion about variant significance. Transient expression in tsA201 cells show the variant had similar activity as WT (Portaro_2015), indicating no chance in function. The following publications have been ascertained in the context of this evaluation (PMID: 23739125, 26007199). Three submitters have cited clinical-significance assessments for this variant to ClinVar after 2014. All submitters classified the variant as uncertain significance. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Congenital myotonia, autosomal recessive form;C2936781:Congenital myotonia, autosomal dominant form

Uncertain:1

Mar 22, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces arginine, which is basic and polar, with tryptophan, which is neutral and slightly polar, at codon 453 of the CLCN1 protein (p.Arg453Trp). This variant is present in population databases (rs376026619, gnomAD 0.08%). This missense change has been observed in individual(s) with clinical features of myotonia congenita (PMID: 26007199; Invitae). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 420148). 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) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on CLCN1 protein function. Experimental studies have shown that this missense change does not substantially affect CLCN1 function (PMID: 26007199). 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. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.10

BayesDel_addAF

Benign

-0.16

BayesDel_noAF

Benign

-0.26

CADD

Benign

(source)

DANN

Uncertain

1.0

DEOGEN2

Uncertain

0.70

Eigen

Benign

-0.13

Eigen_PC

Benign

-0.30

FATHMM_MKL

Benign

0.39

LIST_S2

Uncertain

0.97

M_CAP

Pathogenic

0.44

MetaRNN

Uncertain

0.69

MetaSVM

Uncertain

-0.23

MutationAssessor

Uncertain

2.3

PhyloP100

0.32

PrimateAI

Benign

0.21

PROVEAN

Uncertain

-2.9

REVEL

Uncertain

0.32

Sift

Benign

0.074

Sift4G

Benign

0.14

Polyphen

0.99

Vest4

0.78

MVP

0.93

MPC

0.59

ClinPred

0.43

GERP RS

2.5

Varity_R

0.43

gMVP

0.71

Mutation Taster

=35/65

disease causing

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.020

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

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over