X-71223808-T-C

Position:

• chrX-71223808-T-C

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_000166.6(GJB1):​c.101T>C​(p.Met34Thr) 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. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M34K) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 23)
• Consequence: GJB1 NM_000166.6 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2 U:1
• Conservation: PhyloP100: 3.91

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 Pathogenic. Variant got 18 ACMG points.

• PM1: In a hotspot region, there are 10 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 13 uncertain in NM_000166.6
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chrX-71223807-A-G is described in ClinVar as [Pathogenic]. Clinvar id is 565409.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.986
• PP5: Variant X-71223808-T-C is Pathogenic according to our data. Variant chrX-71223808-T-C is described in ClinVar as [Pathogenic]. Clinvar id is 406224.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chrX-71223808-T-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GJB1	NM_000166.6	c.101T>C	p.Met34Thr	missense_variant	2/2	ENST00000361726.7
GJB1	NM_001097642.3	c.101T>C	p.Met34Thr	missense_variant	2/2
GJB1	XM_011530907.3	c.101T>C	p.Met34Thr	missense_variant	2/2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GJB1	ENST00000361726.7	c.101T>C	p.Met34Thr	missense_variant	2/2	1	NM_000166.6	P1

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 23

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Charcot-Marie-Tooth Neuropathy X Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Aug 16, 2016

Experimental studies in Xenopus oocytes have shown that this missense change affects the electrophysiological properties of the channel encoded by GJB1, known as Connexin 32 in the literature (PMID: 9354338). Additional experiments in HeLa cells found that this missense change alters the sub-cellular localization of Connexin 32 (PMID: 12460545). For these reasons, this variant has been classified as Pathogenic. This variant has been reported in multiple individuals affected with CMTX (PMID: 9401007. 11571214) and has been observed to co-segregate with disease in an affected family (PMID: 8829637). This variant is not present in population databases (ExAC no frequency). This sequence change replaces methionine with threonine at codon 34 of the GJB1 protein (p.Met34Thr). The methionine residue is moderately conserved and there is a moderate physicochemical difference between methionine and threonine. -

GJB1-related disorder Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

PreventionGenetics, part of Exact Sciences

May 17, 2023

The GJB1 c.101T>C variant is predicted to result in the amino acid substitution p.Met34Thr. This variant has been reported in individuals with X-linked Charcot-Marie-Tooth disease (Reported as Met34->Thr in Tan et al 1996. PubMed ID: 8829637; Dubourg. 2001. PubMed ID: 11571214; Supp. Table 2 Volodarsky M et al 2020. PubMed ID: 32376792). Functional studies indicate this variant alters protein function (Oh S et al 1997. PubMed ID: 9354338). This variant has not been reported in a large population database (http://gnomad.broadinstitute.org), indicating this variant is rare. This variant is interpreted as pathogenic. -

Charcot-Marie-Tooth disease Uncertain:1

Uncertain significance, no assertion criteria provided

literature only

Inherited Neuropathy Consortium

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.46
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.34
CADD	Benign	22
DANN	Benign	0.97
DEOGEN2	Pathogenic	0.95	D;D;D;D;D;.;D
FATHMM_MKL	Uncertain	0.79	D
LIST_S2	Benign	0.81	.;.;.;.;T;T;T
M_CAP	Pathogenic	0.80	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Benign	1.6	L;L;L;L;.;.;L
MutationTaster	Benign	0.99	D;D;D
PrimateAI	Uncertain	0.78	T
PROVEAN	Uncertain	-3.7	D;.;D;.;D;.;D
REVEL	Pathogenic	0.78
Sift	Benign	0.041	D;.;D;.;D;.;D
Sift4G	Uncertain	0.048	D;.;D;.;D;.;D
Polyphen		0.24	B;B;B;B;.;.;B
Vest4		0.81
MutPred		0.96		Gain of sheet (P = 0.0827);Gain of sheet (P = 0.0827);Gain of sheet (P = 0.0827);Gain of sheet (P = 0.0827);Gain of sheet (P = 0.0827);Gain of sheet (P = 0.0827);Gain of sheet (P = 0.0827);
MVP		1.0
MPC		1.8
ClinPred		0.92	D
GERP RS		4.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.74
gMVP		0.98

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: rs1060500998; hg19: chrX-70443658;