X-71224209-T-G

Variant names:

• chrX-71224209-T-G
• rs1057518780
• NM_000166.6:c.502T>G

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP3_Strong PP5

The NM_000166.6(GJB1):​c.502T>G​(p.Cys168Gly) variant causes a missense change involving the alteration of a conserved nucleotide. 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 Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 22)
• Consequence: GJB1 NM_000166.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:1
• Conservation: PhyloP100: 8.02

Genes affected

GJB1 (HGNC:4283): (gap junction protein beta 1) This gene encodes a member of the gap junction protein family. The gap junction proteins are membrane-spanning proteins that assemble to form gap junction channels that facilitate the transfer of ions and small molecules between cells. According to sequence similarities at the nucleotide and amino acid levels, the gap junction proteins are divided into two categories, alpha and beta. Mutations in this gene cause X-linked Charcot-Marie-Tooth disease, an inherited peripheral neuropathy. Alternatively spliced transcript variants encoding the same protein have been found for this gene. [provided by RefSeq, Oct 2008]

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a chain Gap junction beta-1 protein (size 282) in uniprot entity CXB1_HUMAN there are 4 pathogenic changes around while only 0 benign (100%) in NM_000166.6
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.975
• PP5: Variant X-71224209-T-G is Pathogenic according to our data. Variant chrX-71224209-T-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 373934.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=2, Uncertain_significance=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GJB1	NM_000166.6	c.502T>G	p.Cys168Gly	missense_variant	Exon 2 of 2	ENST00000361726.7	NP_000157.1
GJB1	NM_001097642.3	c.502T>G	p.Cys168Gly	missense_variant	Exon 2 of 2		NP_001091111.1
GJB1	XM_011530907.3	c.502T>G	p.Cys168Gly	missense_variant	Exon 2 of 2		XP_011529209.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GJB1	ENST00000361726.7	c.502T>G	p.Cys168Gly	missense_variant	Exon 2 of 2	1	NM_000166.6	ENSP00000354900.6

Frequencies

GnomAD3 genomes Cov.: 22

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 22

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hand muscle atrophy;C0728829:Pes cavus;C1389118:Peroneal muscle atrophy;C1836450:Distal lower limb muscle weakness Pathogenic:1

Aug 10, 2016

Centre for Mendelian Genomics, University Medical Centre Ljubljana

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Sensory neuropathy;C0427065:Distal muscle weakness;C0728829:Pes cavus;C1136179:Hammertoe;C1857640:Decreased nerve conduction velocity Pathogenic:1

Nov 27, 2014

Centre for Mendelian Genomics, University Medical Centre Ljubljana

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Charcot-Marie-Tooth disease X-linked dominant 1 Pathogenic:1

Jan 01, 2016

Centre for Mendelian Genomics, University Medical Centre Ljubljana

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was classified as: Likely pathogenic. The following ACMG criteria were applied in classifying this variant: PM2,PM5,PP3,PP5. -

Charcot-Marie-Tooth Neuropathy X Uncertain:1

Apr 30, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces cysteine, which is neutral and slightly polar, with glycine, which is neutral and non-polar, at codon 168 of the GJB1 protein (p.Cys168Gly). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with GJB1-related conditions. ClinVar contains an entry for this variant (Variation ID: 373934). 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 GJB1 protein function with a positive predictive value of 80%. This variant disrupts the p.Cys168 amino acid residue in GJB1. Other variant(s) that disrupt this residue have been observed in individuals with GJB1-related conditions (PMID: 12325071, 15241803), which suggests that this may be a clinically significant amino acid residue. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.74	D
BayesDel_noAF	Pathogenic	0.82
CADD	Uncertain	25
DANN	Uncertain	0.97
DEOGEN2	Pathogenic	0.99	D;D;D;D;D
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.93	.;.;.;.;D
M_CAP	Pathogenic	0.94	D
MetaRNN	Pathogenic	0.97	D;D;D;D;D
MetaSVM	Pathogenic	0.99	D
MutationAssessor	Pathogenic	4.2	H;H;H;H;H
PrimateAI	Uncertain	0.75	T
PROVEAN	Pathogenic	-12	D;.;D;.;D
REVEL	Pathogenic	0.95
Sift	Pathogenic	0.0	D;.;D;.;D
Sift4G	Pathogenic	0.0	D;.;D;.;D
Polyphen		1.0	D;D;D;D;D
Vest4		0.98
MutPred		0.71		Loss of stability (P = 0.0058);Loss of stability (P = 0.0058);Loss of stability (P = 0.0058);Loss of stability (P = 0.0058);Loss of stability (P = 0.0058);
MVP		1.0
MPC		2.1
ClinPred		1.0	D
GERP RS		4.8
Varity_R		0.99
gMVP		1.0

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: rs1057518780; hg19: chrX-70444059;