chrX-71224168-A-G

Position:

• chrX-71224168-A-G

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Strong

The NM_000166.6(GJB1):​c.461A>G​(p.Tyr154Cys) 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 Uncertain significance (★★).

• Frequency: Genomes: not found (cov: 22)
• Consequence: GJB1 NM_000166.6 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts 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 8 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, 0.968

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GJB1	NM_000166.6	c.461A>G	p.Tyr154Cys	missense_variant	2/2	ENST00000361726.7	NP_000157.1
GJB1	NM_001097642.3	c.461A>G	p.Tyr154Cys	missense_variant	2/2		NP_001091111.1
GJB1	XM_011530907.3	c.461A>G	p.Tyr154Cys	missense_variant	2/2		XP_011529209.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GJB1	ENST00000361726.7	c.461A>G	p.Tyr154Cys	missense_variant	2/2	1	NM_000166.6	ENSP00000354900	P1

Frequencies

GnomAD3 genomes Cov.: 22

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 22

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Charcot-Marie-Tooth Neuropathy X Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Sep 15, 2021

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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. This missense change has been observed in individual(s) with clinical features of GJB1-related conditions (Invitae). This variant is not present in population databases (ExAC no frequency). This sequence change replaces tyrosine with cysteine at codon 154 of the GJB1 protein (p.Tyr154Cys). The tyrosine residue is highly conserved and there is a large physicochemical difference between tyrosine and cysteine. -

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

Uncertain significance, criteria provided, single submitter

clinical testing

3billion

-

The variant is not observed in the gnomAD v2.1.1 dataset. In silico tool predictions suggest damaging effect of the variant on gene or gene product (REVEL: 0.96; 3Cnet: 0.86). Therefore, this variant is classified as Uncertain significance according to the recommendation of ACMG/AMP guideline. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.41
BayesDel_addAF	Pathogenic	0.71	D
BayesDel_noAF	Pathogenic	0.79
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	D;D;D;D;D
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.87	.;.;.;.;D
M_CAP	Pathogenic	0.95	D
MetaRNN	Pathogenic	0.97	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.2	M;M;M;M;M
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Uncertain	0.75	T
PROVEAN	Pathogenic	-7.4	D;.;D;.;D
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	D;.;D;.;D
Sift4G	Pathogenic	0.0010	D;.;D;.;D
Polyphen		1.0	D;D;D;D;D
Vest4		0.94
MutPred		0.68		Loss of catalytic residue at P158 (P = 0.0896);Loss of catalytic residue at P158 (P = 0.0896);Loss of catalytic residue at P158 (P = 0.0896);Loss of catalytic residue at P158 (P = 0.0896);Loss of catalytic residue at P158 (P = 0.0896);
MVP		1.0
MPC		2.1
ClinPred		1.0	D
GERP RS		4.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.96
gMVP		1.0

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1555937189; hg19: chrX-70444018;