rs121912807

chr7-143339534-G-A

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PM1 PM2 PP3_Strong PP5_Very_Strong

The NM_000083.3(CLCN1):c.1495G>A(p.Gly499Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,464 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 13/23 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G499E) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: CLCN1 NM_000083.3 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 9.99

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]

ACMG classification

Verdict is Pathogenic. Variant got 16 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 5 uncertain in NM_000083.3
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.994
• PP5: Variant 7-143339534-G-A is Pathogenic according to our data. Variant chr7-143339534-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 17543.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr7-143339534-G-A is described in Lovd as [Pathogenic]. Variant chr7-143339534-G-A is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CLCN1	NM_000083.3	c.1495G>A	p.Gly499Arg	missense_variant	14/23	ENST00000343257.7
CLCN1	NR_046453.2	n.1450G>A		non_coding_transcript_exon_variant	13/22

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CLCN1	ENST00000343257.7	c.1495G>A	p.Gly499Arg	missense_variant	14/23	1	NM_000083.3	P4
CLCN1	ENST00000432192.6	c.*780G>A		3_prime_UTR_variant, NMD_transcript_variant	14/23	1
CLCN1	ENST00000650516.2	c.1495G>A	p.Gly499Arg	missense_variant	14/23			A2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251464 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135914

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: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000879

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461464 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727078

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

EpiCase AF: 0.0000545

EpiControl AF: 0.00

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Congenital myotonia, autosomal recessive form Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Laboratory of Medical Genetics, National & Kapodistrian University of Athens	Feb 20, 2024	- -
Pathogenic, no assertion criteria provided	literature only	OMIM	Jan 28, 2000	- -

Congenital myotonia, autosomal recessive form;C2936781:Congenital myotonia, autosomal dominant form Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Nov 29, 2022

For these reasons, this variant has been classified as Pathogenic. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. Experimental studies have shown that this missense change affects CLCN1 function (PMID: 10644771). 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. ClinVar contains an entry for this variant (Variation ID: 17543). This missense change has been observed in individual(s) with autosomal recessive myotonia congenita (PMID: 10644771, 23113340; Invitae). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. This variant is present in population databases (rs121912807, gnomAD 0.0009%). This sequence change replaces glycine, which is neutral and non-polar, with arginine, which is basic and polar, at codon 499 of the CLCN1 protein (p.Gly499Arg). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
Cadd	Pathogenic	34
Dann	Pathogenic	1.0
DEOGEN2	Pathogenic	0.97	D
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.96
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.85	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.4	H
MutationTaster	Benign	1.0	A
PrimateAI	Pathogenic	0.83	D
PROVEAN	Pathogenic	-7.4	D
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		0.99	D
Vest4		0.99
MutPred		0.95		Loss of methylation at R496 (P = 0.0845);
MVP		0.97
MPC		0.81
ClinPred		1.0	D
GERP RS		5.1
Varity_R		0.99
gMVP		0.99

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.26		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.26		Position offset: -4

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs121912807; hg19: chr7-143036627; COSMIC: COSV58374316;