rs80356694

Positions:

• chr7-143339290-C-A
• chr7-143339290-C-T

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Moderate

The NM_000083.3(CLCN1):​c.1439C>A​(p.Pro480His) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,876 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 Pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. P480L) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: CLCN1 NM_000083.3 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.89

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 Pathogenic. Variant got 12 ACMG points.

• PM1: In a transmembrane_region Helical (size 19) 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
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr7-143339290-C-T is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.994
• PP5: Variant 7-143339290-C-A is Pathogenic according to our data. Variant chr7-143339290-C-A is described in ClinVar as [Pathogenic]. Clinvar id is 942360.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CLCN1	NM_000083.3	c.1439C>A	p.Pro480His	missense_variant	13/23	ENST00000343257.7	NP_000074.3
CLCN1	NR_046453.2	n.1394C>A		non_coding_transcript_exon_variant	12/22

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CLCN1	ENST00000343257.7	c.1439C>A	p.Pro480His	missense_variant	13/23	1	NM_000083.3	ENSP00000339867.2
CLCN1	ENST00000432192.6	n.*724C>A		non_coding_transcript_exon_variant	13/23	1		ENSP00000395949.2
CLCN1	ENST00000432192.6	n.*724C>A		3_prime_UTR_variant	13/23	1		ENSP00000395949.2
CLCN1	ENST00000650516.2	c.1439C>A	p.Pro480His	missense_variant	13/23			ENSP00000498052.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460876 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 726790

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: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: 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

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Apr 12, 2023

For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Pro480 amino acid residue in CLCN1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 8112288, 18337730). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Studies have shown that this missense change alters CLCN1 gene expression (PMID: 27666773). 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: 942360). This missense change has been observed in individuals with clinical features of autosomal dominant myotonia congenita (PMID: 27666773; Invitae). This variant has been reported in individual(s) with clinical features of autosomal recessive myotonia congenita (PMID: 17932099); however, the role of the variant in this condition is currently unclear. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces proline, which is neutral and non-polar, with histidine, which is basic and polar, at codon 480 of the CLCN1 protein (p.Pro480His). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.53
CADD	Pathogenic	30
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.96	D
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.98
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.96	D
M_CAP	Pathogenic	0.73	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.4	H
PrimateAI	Uncertain	0.78	T
PROVEAN	Pathogenic	-8.6	D
REVEL	Pathogenic	0.98
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.97
MutPred		0.94		Loss of helix (P = 0.1299);
MVP		0.99
MPC		0.80
ClinPred		1.0	D
GERP RS		5.6
Varity_R		0.97
gMVP		0.95

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs80356694; hg19: chr7-143036383;