rs80356688

Positions:

• chr7-143324486-C-T

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.847C>T​(p.Leu283Phe) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: CLCN1 NM_000083.3 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 4.70

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 Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a intramembrane_region Helical (size 21) in uniprot entity CLCN1_HUMAN there are 15 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, 0.937
• PP5: Variant 7-143324486-C-T is Pathogenic according to our data. Variant chr7-143324486-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 1347742.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr7-143324486-C-T is described in Lovd as [Pathogenic]. Variant chr7-143324486-C-T is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CLCN1	NM_000083.3	c.847C>T	p.Leu283Phe	missense_variant	7/23	ENST00000343257.7	NP_000074.3
CLCN1	NR_046453.2	n.952C>T		non_coding_transcript_exon_variant	7/22

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CLCN1	ENST00000343257.7	c.847C>T	p.Leu283Phe	missense_variant	7/23	1	NM_000083.3	ENSP00000339867	P4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic: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

Jan 31, 2023

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. Experimental studies have shown that this missense change affects CLCN1 function (PMID: 12390967). 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. ClinVar contains an entry for this variant (Variation ID: 1347742). This missense change has been observed in individuals with autosomal dominant myotonia congenita (PMID: 12390967; Invitae). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces leucine, which is neutral and non-polar, with phenylalanine, which is neutral and non-polar, at codon 283 of the CLCN1 protein (p.Leu283Phe). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.66
BayesDel_addAF	Pathogenic	0.49	D
BayesDel_noAF	Pathogenic	0.47
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.82	D
Eigen	Benign	0.084
Eigen_PC	Benign	0.22
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.87	D
M_CAP	Uncertain	0.22	D
MetaRNN	Pathogenic	0.94	D
MetaSVM	Uncertain	0.65	D
MutationAssessor	Benign	1.3	L
MutationTaster	Benign	1.0	A
PrimateAI	Pathogenic	0.82	D
PROVEAN	Uncertain	-2.6	D
REVEL	Pathogenic	0.75
Sift	Uncertain	0.0020	D
Sift4G	Benign	0.094	T
Polyphen		0.11	B
Vest4		0.93
MutPred		0.82		Gain of helix (P = 0.2684);
MVP		0.96
MPC		0.75
ClinPred		0.99	D
GERP RS		4.6
Varity_R		0.86
gMVP		0.85

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: rs80356688; hg19: chr7-143021579;