X-71224198-G-T

Variant names:

• chrX-71224198-G-T
• rs1241595912
• NM_000166.6:c.491G>T

Variant summary

Our verdict is Pathogenic. The variant received 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate PP5_Moderate

The NM_000166.6(GJB1):​c.491G>T​(p.Arg164Leu) 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 Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R164G) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 22)
• Consequence: GJB1 NM_000166.6 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 10.0
• Publications: 28 publications found

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]

GJB1 Gene-Disease associations (from GenCC):

• Charcot-Marie-Tooth disease X-linked dominant 1

  Inheritance: XL Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Orphanet, PanelApp Australia, ClinGen, Labcorp Genetics (formerly Invitae)
• X-linked progressive cerebellar ataxia

  Inheritance: XL Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 11 ACMG points.

• PM1: In a hotspot region, there are 12 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 23 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-71224198-G-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 543920.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 135 curated pathogenic missense variants (we use a threshold of 10). The gene has 4 curated benign missense variants. Trascript score misZ: NaN (below the threshold of 3.09). GenCC associations: The gene is linked to Charcot-Marie-Tooth disease X-linked dominant 1, X-linked progressive cerebellar ataxia.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.925
• PP5: Variant X-71224198-G-T is Pathogenic according to our data. Variant chrX-71224198-G-T is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 846947.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GJB1	NM_000166.6	c.491G>T	p.Arg164Leu	missense_variant	Exon 2 of 2	ENST00000361726.7	NP_000157.1
GJB1	NM_001097642.3	c.491G>T	p.Arg164Leu	missense_variant	Exon 2 of 2		NP_001091111.1
GJB1	NM_001440770.1	c.491G>T	p.Arg164Leu	missense_variant	Exon 3 of 3		NP_001427699.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GJB1	ENST00000361726.7	c.491G>T	p.Arg164Leu	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: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Charcot-Marie-Tooth Neuropathy X Pathogenic:1

Aug 22, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense change has been observed in individuals with clinical features of Charcot-Marie-Tooth disease (PMID: 28768847, 31902012; Invitae). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces arginine, which is basic and polar, with leucine, which is neutral and non-polar, at codon 164 of the GJB1 protein (p.Arg164Leu). ClinVar contains an entry for this variant (Variation ID: 846947). 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. This variant disrupts the p.Arg164 amino acid residue in GJB1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 7580242, 8733054, 9187667, 15006706, 27844031). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.71
BayesDel_addAF	Pathogenic	0.65	D
BayesDel_noAF	Pathogenic	0.69
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.95	D;D;D;D;D
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.89	.;.;.;.;D
M_CAP	Pathogenic	0.93	D
MetaRNN	Pathogenic	0.92	D;D;D;D;D
MetaSVM	Pathogenic	0.97	D
MutationAssessor	Pathogenic	3.1	M;M;M;M;M
PhyloP100		10
PrimateAI	Uncertain	0.77	T
PROVEAN	Pathogenic	-5.1	D;.;D;.;D
REVEL	Pathogenic	0.89
Sift	Benign	0.18	T;.;T;.;T
Sift4G	Benign	0.56	T;.;T;.;T
Polyphen		1.0	D;D;D;D;D
Vest4		0.88
MutPred		0.65		Gain of sheet (P = 0.039);Gain of sheet (P = 0.039);Gain of sheet (P = 0.039);Gain of sheet (P = 0.039);Gain of sheet (P = 0.039);
MVP		1.0
MPC		2.0
ClinPred		1.0	D
GERP RS		4.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.83
gMVP		0.99
Mutation Taster		=0/100	disease causing

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

Other links and lift over

dbSNP: rs1241595912; hg19: chrX-70444048;