chr7-143319840-A-G

Variant names:

• chr7-143319840-A-G
• rs948634525
• NM_000083.3:c.266A>G

Variant summary

Our verdict is Uncertain significance. The variant received 1 ACMG points: 1P and 0B. PP2

The NM_000083.3(CLCN1):​c.266A>G​(p.Asp89Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000558 in 1,613,834 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000048 (0 hom.)
• Consequence: CLCN1 NM_000083.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.22
• Publications: 0 publications found

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 Gene-Disease associations (from GenCC):

• myotonia congenita, autosomal dominant

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae)
• myotonia congenita, autosomal recessive

  Inheritance: AR Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp
• Thomsen and Becker disease

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 1 ACMG points.

• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 106 curated pathogenic missense variants (we use a threshold of 10). The gene has 18 curated benign missense variants. Gene score misZ: 0.21191 (below the threshold of 3.09). Trascript score misZ: 0.95247 (below the threshold of 3.09). GenCC associations: The gene is linked to myotonia congenita, autosomal dominant, myotonia congenita, autosomal recessive, Thomsen and Becker disease.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000083.3. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CLCN1	NM_000083.3	MANE Select	c.266A>G	p.Asp89Gly	missense	Exon 2 of 23	NP_000074.3
	CLCN1	NR_046453.2		n.368A>G		non_coding_transcript_exon	Exon 2 of 22

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CLCN1	ENST00000343257.7	TSL:1 MANE Select	c.266A>G	p.Asp89Gly	missense	Exon 2 of 23	ENSP00000339867.2
	CLCN1	ENST00000432192.6	TSL:1	n.32A>G		non_coding_transcript_exon	Exon 1 of 23	ENSP00000395949.2
	CLCN1	ENST00000650516.2		c.266A>G	p.Asp89Gly	missense	Exon 2 of 23	ENSP00000498052.2

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152212 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000479 AC: 7 AN: 1461622 Hom.: 0 Cov.: 32 AF XY: 0.00000550 AC XY: 4 AN XY: 727136

African (AFR) AF: 0.0000299 AC: 1 AN: 33468

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26134

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86248

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5762

European-Non Finnish (NFE) AF: 0.00000540 AC: 6 AN: 1111794

Other (OTH) AF: 0.00 AC: 0 AN: 60374

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152212 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74368

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.0000241 AC: 1 AN: 41446

American (AMR) AF: 0.00 AC: 0 AN: 15284

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3470

East Asian (EAS) AF: 0.00 AC: 0 AN: 5202

South Asian (SAS) AF: 0.00 AC: 0 AN: 4834

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10624

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000147 AC: 1 AN: 68030

Other (OTH) AF: 0.00 AC: 0 AN: 2094

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0.00000037155), which strongly suggests a high chance of mosaicism in these individuals.

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.0000189

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Jun 27, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. This sequence change replaces aspartic acid, which is acidic and polar, with glycine, which is neutral and non-polar, at codon 89 of the CLCN1 protein (p.Asp89Gly). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with CLCN1-related conditions. ClinVar contains an entry for this variant (Variation ID: 531745). 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 not expected to disrupt CLCN1 protein function. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.078
BayesDel_addAF	Uncertain	0.088	D
BayesDel_noAF	Benign	-0.11
CADD	Benign	22
DANN	Uncertain	0.99
DEOGEN2	Benign	0.15	T
Eigen	Benign	-0.12
Eigen_PC	Benign	0.034
FATHMM_MKL	Uncertain	0.87	D
LIST_S2	Benign	0.79	T
M_CAP	Benign	0.029	D
MetaRNN	Benign	0.23	T
MetaSVM	Uncertain	-0.12	T
MutationAssessor	Benign	1.7	L
PhyloP100		2.2
PrimateAI	Benign	0.36	T
PROVEAN	Benign	-1.2	N
REVEL	Uncertain	0.39
Sift	Benign	0.11	T
Sift4G	Benign	0.36	T
Polyphen		0.0010	B
Vest4		0.11
MutPred		0.30		Loss of helix (P = 0.0444)
MVP		0.91
MPC		0.24
ClinPred		0.51	D
GERP RS		5.5
Varity_R		0.24
gMVP		0.45
Mutation Taster		=87/13	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.21		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.21		Position offset: 35

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

Other links and lift over

dbSNP: rs948634525; hg19: chr7-143016933;