X-71224083-C-T

Position:

• chrX-71224083-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 5P and 4B. PM1 PP3_Moderate PP5 BS2

The NM_000166.6(GJB1):​c.376C>T​(p.His126Tyr) variant causes a missense change. The variant allele was found at a frequency of 0.00000548 in 1,094,628 control chromosomes in the GnomAD database, with no homozygous occurrence. There are 2 hemizygotes in GnomAD. 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)
  • Exomes 𝑓: 0.0000055 (0 hom. 2 hem.)
• Consequence: GJB1 NM_000166.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:2
• Conservation: PhyloP100: 3.82

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 Uncertain_significance. Variant got 1 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
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.858
• PP5: Variant X-71224083-C-T is Pathogenic according to our data. Variant chrX-71224083-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 245904.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Likely_pathogenic=1}. Variant chrX-71224083-C-T is described in Lovd as [Pathogenic].
• BS2: High Hemizygotes in GnomAdExome4 at 2 XL gene

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GJB1	NM_000166.6	c.376C>T	p.His126Tyr	missense_variant	2/2	ENST00000361726.7	NP_000157.1
GJB1	NM_001097642.3	c.376C>T	p.His126Tyr	missense_variant	2/2		NP_001091111.1
GJB1	XM_011530907.3	c.376C>T	p.His126Tyr	missense_variant	2/2		XP_011529209.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GJB1	ENST00000361726.7	c.376C>T	p.His126Tyr	missense_variant	2/2	1	NM_000166.6	ENSP00000354900.6

Frequencies

GnomAD3 genomes Cov.: 22

GnomAD4 exome AF: 0.00000548 AC: 6 AN: 1094628 Hom.: 0 Cov.: 32 AF XY: 0.00000555 AC XY: 2 AN XY: 360340

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000714

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 22

Bravo AF: 0.00000378

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Charcot-Marie-Tooth Neuropathy X Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 22, 2023

This sequence change replaces histidine, which is basic and polar, with tyrosine, which is neutral and polar, at codon 126 of the GJB1 protein (p.His126Tyr). 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: 11030070, 28768847, 32376792). ClinVar contains an entry for this variant (Variation ID: 245904). 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 not expected to disrupt GJB1 protein function. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Charcot-Marie-Tooth disease Uncertain:1

Uncertain significance, no assertion criteria provided

literature only

Inherited Neuropathy Consortium

-

- -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Feb 16, 2023

Observed in multiple unrelated individuals with Charcot-Marie-Tooth disease (Panosyan et al., 2017; Verhelst et al., 2000; Volodarsky et al., 2021); Not observed at significant frequency in large population cohorts (gnomAD); Missense variants in this gene are often considered pathogenic (HGMD); In silico analysis supports that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 28768847, 11030070, 32376792) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.17
BayesDel_addAF	Pathogenic	0.30	D
BayesDel_noAF	Pathogenic	0.19
CADD	Benign	23
DANN	Uncertain	0.98
DEOGEN2	Pathogenic	0.85	D;D;D;D;D
FATHMM_MKL	Uncertain	0.89	D
LIST_S2	Benign	0.73	.;.;.;.;T
M_CAP	Uncertain	0.25	D
MetaRNN	Pathogenic	0.86	D;D;D;D;D
MetaSVM	Uncertain	0.54	D
MutationAssessor	Benign	0.90	L;L;L;L;L
PrimateAI	Uncertain	0.72	T
PROVEAN	Benign	-1.4	N;.;N;.;N
REVEL	Pathogenic	0.67
Sift	Benign	0.085	T;.;T;.;T
Sift4G	Benign	0.11	T;.;T;.;T
Polyphen		0.83	P;P;P;P;P
Vest4		0.21
MutPred		0.79		Loss of disorder (P = 0.0277);Loss of disorder (P = 0.0277);Loss of disorder (P = 0.0277);Loss of disorder (P = 0.0277);Loss of disorder (P = 0.0277);
MVP		0.96
MPC		0.98
ClinPred		0.55	D
GERP RS		3.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.26
gMVP		0.92

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: rs879253995; hg19: chrX-70443933;