rs879254097

Positions:

• chrX-71223946-A-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.239A>G​(p.Gln80Arg) 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: 23)
• Consequence: GJB1 NM_000166.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:2
• Conservation: PhyloP100: 9.32

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, 0.993
• PP5: Variant X-71223946-A-G is Pathogenic according to our data. Variant chrX-71223946-A-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 246096.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Pathogenic=2, Likely_pathogenic=1}. Variant chrX-71223946-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GJB1	NM_000166.6	c.239A>G	p.Gln80Arg	missense_variant	2/2	ENST00000361726.7	NP_000157.1
GJB1	NM_001097642.3	c.239A>G	p.Gln80Arg	missense_variant	2/2		NP_001091111.1
GJB1	XM_011530907.3	c.239A>G	p.Gln80Arg	missense_variant	2/2		XP_011529209.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GJB1	ENST00000361726.7	c.239A>G	p.Gln80Arg	missense_variant	2/2	1	NM_000166.6	ENSP00000354900.6

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 23

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Aug 20, 2021	Functional studies show that the Q80R variant is capable of forming a functional gap junction protein, and the authors conclude that further functional studies are necessary to elucidate the effect, if any, of the Q80R variant (Wang et al., 2004); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Missense variants in this gene are often considered pathogenic (Stenson et al., 2014); Not observed at significant frequency in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 30042657, 25449862, 15006706, 9361298, 28211240, 17353473, 8737658, 10873293, 10737979, 7580242) -
Pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	Aug 26, 2024	This variant has not been reported in large, multi-ethnic general populations. (http://gnomad.broadinstitute.org) In some published literature, this variant is referred to as c.301A>G, (p.Gln80Arg). Assessment of experimental evidence regarding the effect of this variant on protein function is inconclusive (PMID: 15006706). This variant has been identified in multiple unrelated individuals with clinical features associated with this gene. This variant occurs as the most likely explanation for disease in a significant number of internal cases, suggesting this variant is associated with disease. -

Charcot-Marie-Tooth Neuropathy X Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 19, 2024

This sequence change replaces glutamine, which is neutral and polar, with arginine, which is basic and polar, at codon 80 of the GJB1 protein (p.Gln80Arg). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with Charcot-Marie-Tooth disease (PMID: 7580242, 10737979, 17353473; Invitae). ClinVar contains an entry for this variant (Variation ID: 246096). 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%. Experimental studies have shown that this missense change does not substantially affect GJB1 function (PMID: 15006706). This variant disrupts the p.Gln80 amino acid residue in GJB1. Other variant(s) that disrupt this residue have been observed in individuals with GJB1-related conditions (PMID: 22464564, 28286897), which suggests that this may be a clinically significant amino acid residue. For these reasons, this variant has been classified as Pathogenic. -

Charcot-Marie-Tooth disease Uncertain:1

Uncertain significance, no assertion criteria provided

literature only

Inherited Neuropathy Consortium

-

- -

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Aug 22, 2022

The p.Q80R variant (also known as c.239A>G), located in coding exon 1 of the GJB1 gene, results from an A to G substitution at nucleotide position 239. The glutamine at codon 80 is replaced by arginine, an amino acid with highly similar properties. This alteration has been detected in individuals with features consistent with Charcot-Marie-Tooth neuropathy X type 1 (CMTX1); however, clinical details were limited (Mersiyanova IV et al. Hum Mutat, 2000;15:340-7; Ionasescu V et al. Am J Med Genet, 1996 Jun;63:486-91). Functional studies in vitro have shown that Q80R retains its ability to form homotypic junctional channels, similar to wild-type cells (Wang HL et al. Neurobiol Dis, 2004 Mar;15:361-70). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.73	D
BayesDel_noAF	Pathogenic	0.81
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.99	D;D;D;D;D;.;D
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	0.98	.;.;.;.;D;D;D
M_CAP	Pathogenic	0.97	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	4.0	H;H;H;H;.;.;H
PrimateAI	Pathogenic	0.82	D
PROVEAN	Uncertain	-4.0	D;.;D;.;D;.;D
REVEL	Pathogenic	0.99
Sift	Uncertain	0.0010	D;.;D;.;D;.;D
Sift4G	Pathogenic	0.0	D;.;D;.;D;.;D
Polyphen		1.0	D;D;D;D;.;.;D
Vest4		0.96
MutPred		0.99		Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);Gain of helix (P = 0.132);
MVP		1.0
MPC		1.9
ClinPred		1.0	D
GERP RS		4.7
Varity_R		0.98
gMVP		1.0

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: rs879254097; hg19: chrX-70443796;