7-143321816-G-T

Variant names:

• chr7-143321816-G-T
• rs747078264
• NM_000083.3:c.664G>T

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM1 PM2 PP2 PP3_Moderate

The NM_000083.3(CLCN1):​c.664G>T​(p.Gly222Cys) 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. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G222S) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 33)
• Consequence: CLCN1 NM_000083.3 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 6.79
• 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: Likely_pathogenic. The variant received 7 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 uncertain in NM_000083.3
• PM2: Very rare variant in population databases, with high coverage
• 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.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.887

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CLCN1	NM_000083.3	c.664G>T	p.Gly222Cys	missense_variant	Exon 5 of 23	ENST00000343257.7	NP_000074.3
CLCN1	NR_046453.2	n.766G>T		non_coding_transcript_exon_variant	Exon 5 of 22

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CLCN1	ENST00000343257.7	c.664G>T	p.Gly222Cys	missense_variant	Exon 5 of 23	1	NM_000083.3	ENSP00000339867.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.45
BayesDel_addAF	Pathogenic	0.29	D
BayesDel_noAF	Pathogenic	0.18
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.58	.;D
Eigen	Uncertain	0.65
Eigen_PC	Uncertain	0.63
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.95	D;D
M_CAP	Uncertain	0.28	D
MetaRNN	Pathogenic	0.89	D;D
MetaSVM	Pathogenic	0.91	D
MutationAssessor	Benign	1.2	.;L
PhyloP100		6.8
PrimateAI	Uncertain	0.77	T
PROVEAN	Uncertain	-2.4	.;N
REVEL	Pathogenic	0.77
Sift	Uncertain	0.0060	.;D
Sift4G	Benign	0.063	.;T
Polyphen		1.0	.;D
Vest4		0.78
MutPred		0.67		Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);
MVP		0.98
MPC		0.76
ClinPred		0.98	D
GERP RS		5.0
Varity_R		0.75
gMVP		0.81
Mutation Taster		=52/48	polymorphism

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

Other links and lift over

dbSNP: rs747078264; hg19: chr7-143018909; COSMIC: COSV58373335;