7-143330813-G-C

Position:

chr7-143330813-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PP3_ModeratePP5

The NM_000083.3(CLCN1):c.895G>C(p.Val299Leu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000558 in 1,614,086 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000055 ( 0 hom. )

Consequence

CLCN1
NM_000083.3 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:4U:3

Conservation

PhyloP100: 9.99

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 links:

CLCN1 (HGNC:):

CLCN1 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 3 ACMG points.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.932

PP5

Variant 7-143330813-G-C is Pathogenic according to our data. Variant chr7-143330813-G-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 447073.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=3, Pathogenic=1, Likely_pathogenic=3}. Variant chr7-143330813-G-C is described in Lovd as [Pathogenic]. Variant chr7-143330813-G-C is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CLCN1	NM_000083.3 linkuse as main transcript	c.895G>C	p.Val299Leu	missense_variant	8/23	ENST00000343257.7	NP_000074.3	P35523
CLCN1	NR_046453.2 linkuse as main transcript	n.1000G>C		non_coding_transcript_exon_variant	8/22

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CLCN1	ENST00000343257.7 linkuse as main transcript	c.895G>C	p.Val299Leu	missense_variant	8/23	1	NM_000083.3	ENSP00000339867.2		P35523

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152200

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

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:

0.00000398

AC:

AN:

251404

Hom.:

AF XY:

0.00000736

AC XY:

AN XY:

135870

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.0000327

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000547

AC:

AN:

1461886

Hom.:

Cov.:

AF XY:

0.00000688

AC XY:

AN XY:

727242

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.0000116

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000540

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152200

Hom.:

Cov.:

AF XY:

0.0000134

AC XY:

AN XY:

74362

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

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:

0.000478

Alfa

AF:

0.0000712

Hom.:

Bravo

AF:

0.0000113

EpiCase

AF:

0.000109

EpiControl

AF:

0.00

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:4Uncertain:3

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Congenital myotonia, autosomal recessive form

Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Victorian Clinical Genetics Services, Murdoch Childrens Research Institute	Jul 17, 2023	Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as Likely pathogenic. Following criteria are met: 0103 - Dominant negative and loss of function are known mechanisms of disease in this gene and are associated with autosomal dominant myotonia congenita (AD MC; MIM#160800) and autosomal recessive myotonia congenita (AR MC; MIM#255700), respectively (GeneReviews; PMID: 32117034). (I) 0108 - This gene is associated with both recessive and dominant disease. The genotype-phenotype correlation is currently unestablished however, AR MC is a more severe disease than AR MC (GeneReviews). (I) 0112 - The condition associated with this gene has incomplete penetrance. Specifically, this has been described in AD MC families (GeneReviews). (I) 0115 - Variants in this gene are known to have variable expressivity. Intra-familial variability has been described (GeneReviews). (I) 0200 - Variant is predicted to result in a missense amino acid change from valine to leucine. (I) 0251 - This variant is heterozygous. (I) 0304 - Variant is present in gnomAD <0.01 condition (v2+v3: 2 heterozygotes, 0 homozygotes). (SP) 0309 - An alternative amino acid change at the same position has been observed in gnomAD (v2: 1 heterozygote, 0 homozygotes). (I) 0502 - Missense variant with conflicting in silico predictions and uninformative conservation. (I) 0600 - Variant is located in the annotated TM1 domain (PMID: 34529042). (I) 0704 - Another missense variant comparable to the one identified in this case has limited previous evidence for pathogenicity. p.(Val299Ala) has been identified in a compound heterozygote individual with AR MC (PMID: 34790634). (SP) 0801 - This variant has strong previous evidence of pathogenicity in unrelated individuals. It has been reported in one AD MC family with two affecteds (PMID: 29606556), two AR MC families, one of whom reportedly have unaffected carrier parents (PMIDs: 34529042, 17932099) and in an individual with an undiagnosed neuromuscular disorder, although zygosity was not reported (PMID: 32528171). Diagnostic laboratories in ClinVar has conflicting classifications for this variant, both likely pathogenic and VUS. (SP) 1002 - This variant has moderate functional evidence supporting abnormal protein function. Patch clamp assays in xenopus oocytes demonstrated a reduction in channel activities when expressed both as a homomer or in heterozygous state (co-expressed as mutant + WT) (PMID: 34529042). (SP) 1206 - This variant has been shown to be paternally inherited (by trio analysis). (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Oct 30, 2024	Variant summary: CLCN1 c.895G>C (p.Val299Leu) results in a conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 4e-06 in 251404 control chromosomes. c.895G>C has been reported in the literature as a heterozygous and homozygous genotype in multiple individuals affected with features of myotonia congenita/skeletal muscle channelopathies/neuromuscular disorders (Abolhassani_2024, Fialho_2007, Stunnenberg_2018, Suetterlin_2022, Tpf_2020). At least one affected homozygous individual had unaffected heterozygous carrier parents reported as distant cousins with evidence of transient weakness (e.g, Fialho_2007). As both dominant and recessive variants have been reported in this gene, these data indicate that the variant is very likely to be associated with disease. The following publications have been ascertained in the context of this evaluation (PMID: 38374194, 17932099, 29606556, 34529042, 32528171). ClinVar contains an entry for this variant (Variation ID: 447073). Based on the evidence outlined above, the variant was classified as pathogenic. -

not provided

Pathogenic:1Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Nov 30, 2021	Not observed at significant frequency in large population cohorts (Lek et al., 2016); 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: 17932099, 32528171) -
Likely pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Apr 27, 2017	- -

Abnormality of the musculature

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Kariminejad - Najmabadi Pathology & Genetics Center

Jul 10, 2021

- -

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

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Mar 21, 2022

This sequence change replaces valine, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 299 of the CLCN1 protein (p.Val299Leu). This variant is present in population databases (rs202179484, gnomAD 0.003%). This missense change has been observed in individual(s) with clinical features of autosomal dominant CLCN1-related conditions (PMID: 29606556). ClinVar contains an entry for this variant (Variation ID: 447073). 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 expected to disrupt CLCN1 protein function. 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. -

Congenital myotonia, autosomal dominant form

Uncertain:1

Uncertain significance, criteria provided, single submitter

curation

Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard

May 04, 2022

The heterozygous p.Val299Leu variant in CLCN1 was identified by our study in 1 individual with autosomal dominant myotonia congenita. The variant has been reported in 2 Dutch individuals with autosomal dominant myotonia congenita (PMID: 29606556), and has been identified in 0.003% (1/30614) of South Asian chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP ID: rs202179484). Although this variant has been seen in the general population, its frequency is not high enough to rule out a pathogenic role. This variant has also been reported in ClinVar (Variation ID: 447073) as likely pathogenic by Athena Diagnostics Inc, and as having uncertain significance by GeneDx. Computational prediction tools and conservation analyses suggest that this variant may impact the protein, though this information is not predictive enough to determine pathogenicity. In summary, while there is some suspicion for a pathogenic role, the clinical significance of this variant is uncertain. ACMG/AMP Criteria applied: PS4_supporting, PP3 (Richards 2015). -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.78

BayesDel_addAF

Pathogenic

0.39

BayesDel_noAF

Pathogenic

0.43

CADD

Pathogenic

DANN

Uncertain

1.0

DEOGEN2

Uncertain

0.76

.;D

Eigen

Uncertain

0.58

Eigen_PC

Uncertain

0.54

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Uncertain

0.97

D;D

M_CAP

Pathogenic

0.43

MetaRNN

Pathogenic

0.93

D;D

MetaSVM

Uncertain

0.74

MutationAssessor

Benign

1.6

.;L

PrimateAI

Pathogenic

0.90

PROVEAN

Uncertain

-2.5

.;D

REVEL

Pathogenic

0.80

Sift

Uncertain

0.0030

.;D

Sift4G

Uncertain

0.0050

.;D

Polyphen

1.0

.;D

Vest4

0.88

MutPred

0.84

Gain of helix (P = 0.132);Gain of helix (P = 0.132);

MVP

0.97

MPC

0.65

ClinPred

0.96

GERP RS

4.6

Varity_R

0.82

gMVP

0.80

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

Publications

LitVar

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over