rs774843953

Positions:

• chr7-143332755-T-C

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PM2 PP3_Strong PP5_Very_Strong

The NM_000083.3(CLCN1):​c.1283T>C​(p.Phe428Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,886 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: CLCN1 NM_000083.3 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4 U:2 O:1
• Conservation: PhyloP100: 8.01

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 14 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.977
• PP5: Variant 7-143332755-T-C is Pathogenic according to our data. Variant chr7-143332755-T-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 208083.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr7-143332755-T-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CLCN1	NM_000083.3	c.1283T>C	p.Phe428Ser	missense_variant	12/23	ENST00000343257.7	NP_000074.3
CLCN1	NR_046453.2	n.1356+252T>C		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CLCN1	ENST00000343257.7	c.1283T>C	p.Phe428Ser	missense_variant	12/23	1	NM_000083.3	ENSP00000339867	P4
CLCN1	ENST00000432192.6	c.*568T>C		3_prime_UTR_variant, NMD_transcript_variant	12/23	1		ENSP00000395949
CLCN1	ENST00000650516.2	c.1283T>C	p.Phe428Ser	missense_variant	12/23			ENSP00000498052	A2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000795 AC: 2 AN: 251466 Hom.: 0 AF XY: 0.0000147 AC XY: 2 AN XY: 135904

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

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: 6.84e-7 AC: 1 AN: 1461886 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727244

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.: 32

Alfa AF: 0.0000965 Hom.: 0

Bravo AF: 0.0000416

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4 Uncertain:2 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:2 Uncertain:2

Pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Feb 19, 2019	The frequency of this variant in the general population is consistent with pathogenicity. Found in at least one patient with expected phenotype for this gene. Predicted to have a damaging effect on the protein. In multiple individuals, this variant has been seen with a single recessive pathogenic variant in the same gene, suggesting this variant may also be pathogenic. Assessment of experimental evidence suggests this variant results in abnormal protein function. -
Likely pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Jan 13, 2023	Reported previously in a patient with a clinical diagnosis of paramyotonia congenita including muscle stiffness, hand weakness and paraesthesias, and abnormal EMG (Wu et al., 2002); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 12390967, 15786415, 9040658, 20301529, 22187529, 22507243, Prado2020[CaseReport]) -
Uncertain significance, flagged submission	clinical testing	Revvity Omics, Revvity	May 31, 2019	- -
Uncertain significance, flagged submission	clinical testing	Eurofins Ntd Llc (ga)	Nov 28, 2017	- -

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

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 20, 2024

This sequence change replaces phenylalanine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 428 of the CLCN1 protein (p.Phe428Ser). This variant is present in population databases (rs774843953, gnomAD 0.003%). This missense change has been observed in individual(s) with clinical features of autosomal recessive myotonia congenita (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: 208083). 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 with a positive predictive value of 95%. Experimental studies have shown that this missense change affects CLCN1 function (PMID: 12390967). For these reasons, this variant has been classified as Pathogenic. -

Congenital myotonia, autosomal recessive form Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Greenwood Genetic Center Diagnostic Laboratories, Greenwood Genetic Center

Jun 01, 2023

PS3_Supporting, PM2, PM3, PP3 -

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	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.48	D
BayesDel_noAF	Pathogenic	0.53
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.90	D
Eigen	Pathogenic	0.95
Eigen_PC	Pathogenic	0.85
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.92	D
M_CAP	Pathogenic	0.74	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.9	H
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.79	T
PROVEAN	Pathogenic	-7.2	D
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.98
MVP		1.0
MPC		1.0
ClinPred		1.0	D
GERP RS		5.4
Varity_R		0.97
gMVP		0.93

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: rs774843953; hg19: chr7-143029848;