rs80356699

Positions:

• chr7-143320744-A-G

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Moderate PP5_Moderate

The NM_000083.3(CLCN1):​c.382A>G​(p.Met128Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,586 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 Likely pathogenic (★).

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: CLCN1 NM_000083.3 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:2 O:1
• Conservation: PhyloP100: 9.20

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 (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a helix (size 34) in uniprot entity CLCN1_HUMAN there are 9 pathogenic changes around while only 0 benign (100%) in NM_000083.3
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.876
• PP5: Variant 7-143320744-A-G is Pathogenic according to our data. Variant chr7-143320744-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 17546.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr7-143320744-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CLCN1	NM_000083.3	c.382A>G	p.Met128Val	missense_variant	3/23	ENST00000343257.7	NP_000074.3
CLCN1	NR_046453.2	n.484A>G		non_coding_transcript_exon_variant	3/22

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CLCN1	ENST00000343257.7	c.382A>G	p.Met128Val	missense_variant	3/23	1	NM_000083.3	ENSP00000339867.2
CLCN1	ENST00000432192.6	n.148A>G		non_coding_transcript_exon_variant	2/23	1		ENSP00000395949.2
CLCN1	ENST00000650516.2	c.382A>G	p.Met128Val	missense_variant	3/23			ENSP00000498052.2

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461586 Hom.: 0 Cov.: 33 AF XY: 0.00000138 AC XY: 1 AN XY: 727126

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: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2 Other:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Sep 29, 2021

In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This variant disrupts the p.Met128 amino acid residue in CLCN1. Other variant(s) that disrupt this residue have been observed in individuals with CLCN1-related conditions (PMID: 19949657, 23113340, 24625573), which suggests that this may be a clinically significant amino acid residue. Experimental studies have shown that this missense change affects CLCN1 function (PMID: 14639587). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0"). ClinVar contains an entry for this variant (Variation ID: 17546). This missense change has been observed in individual(s) with autosomal dominant myotonia congenita (PMID: 12661046, 14639587). It has also been observed to segregate with disease in related individuals. This variant is not present in population databases (ExAC no frequency). This sequence change replaces methionine with valine at codon 128 of the CLCN1 protein (p.Met128Val). The methionine residue is highly conserved and there is a small physicochemical difference between methionine and valine. -

Congenital myotonia, autosomal dominant form Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Apr 01, 2003

- -

Batten-Turner congenital myopathy Other:1

not provided, no classification provided

literature only

GeneReviews

-

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.37
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.37
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.49	.;T
Eigen	Uncertain	0.37
Eigen_PC	Uncertain	0.45
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.95	D;D
M_CAP	Uncertain	0.086	D
MetaRNN	Pathogenic	0.88	D;D
MetaSVM	Uncertain	0.58	D
MutationAssessor	Uncertain	2.6	.;M
PrimateAI	Uncertain	0.67	T
PROVEAN	Uncertain	-3.3	.;D
REVEL	Pathogenic	0.80
Sift	Benign	0.069	.;T
Sift4G	Uncertain	0.033	.;D
Polyphen		0.55	.;P
Vest4		0.96
MutPred		0.77		Gain of catalytic residue at M128 (P = 0.0476);Gain of catalytic residue at M128 (P = 0.0476);
MVP		0.93
MPC		0.27
ClinPred		0.98	D
GERP RS		5.0
Varity_R		0.62
gMVP		0.75

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

Publications

LitVar

Other links and lift over

dbSNP: rs80356699; hg19: chr7-143017837;