NM_000166.6:c.34G>A

Variant names:

• chrX-71223741-G-A
• rs1555936999
• NM_000166.6:c.34G>A

Variant summary

Our verdict is Pathogenic. The variant received 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_000166.6(GJB1):​c.34G>A​(p.Gly12Ser) 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. G12D) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 22)
• Consequence: GJB1 NM_000166.6 missense
• Clinical Significance: Likely pathogenic criteria provided, multiple submitters, no conflicts P:2 U:1
• Conservation: PhyloP100: 9.97
• Publications: 8 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 19 ACMG points.

• PM1: In a hotspot region, there are 13 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 28 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-71223742-G-A is described in ClinVar as Pathogenic. ClinVar VariationId is 565953.Status of the report is criteria_provided_single_submitter, 1 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, 0.981
• PP5: Variant X-71223741-G-A is Pathogenic according to our data. Variant chrX-71223741-G-A is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 477595.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000166.6. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GJB1	NM_000166.6	MANE Select	c.34G>A	p.Gly12Ser	missense	Exon 2 of 2	NP_000157.1
	GJB1	NM_001097642.3		c.34G>A	p.Gly12Ser	missense	Exon 2 of 2	NP_001091111.1
	GJB1	NM_001440770.1		c.34G>A	p.Gly12Ser	missense	Exon 3 of 3	NP_001427699.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GJB1	ENST00000361726.7	TSL:1 MANE Select	c.34G>A	p.Gly12Ser	missense	Exon 2 of 2	ENSP00000354900.6
	GJB1	ENST00000374029.2	TSL:5	c.34G>A	p.Gly12Ser	missense	Exon 2 of 2	ENSP00000363141.1
	GJB1	ENST00000447581.2	TSL:5	c.34G>A	p.Gly12Ser	missense	Exon 3 of 3	ENSP00000407223.2

Frequencies

GnomAD3 genomes Cov.: 22

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 22

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Charcot-Marie-Tooth Neuropathy X Pathogenic:1

Jul 11, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glycine with serine at codon 12 of the GJB1 protein (p.Gly12Ser). The glycine residue is highly conserved and there is a small physicochemical difference between glycine and serine. This variant is not present in population databases (ExAC no frequency). This variant has been reported in a family affected with Charcot-Marie-Tooth disease, type X (PMID: 8266101). Experimental studies have shown that this missense change alters the structure of the GJB1 (also known as Cx32) protein such that a functional channel is not formed and the mutant protein is mislocalized to the Golgi apparatus instead of the plasma membrane (PMID: 9354338, 11325342, 15006706, 19638273, 9364054, 10646523, 22705201). 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.

not provided Pathogenic:1

Feb 16, 2025

Laboratory of Genetics, Children's Clinical University Hospital Latvia

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Charcot-Marie-Tooth disease Uncertain:1

Inherited Neuropathy Consortium

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: literature only

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.53
BayesDel_addAF	Pathogenic	0.49	D
BayesDel_noAF	Pathogenic	0.46
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.95	D
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.94	D
M_CAP	Pathogenic	0.77	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Uncertain	2.4	M
PhyloP100		10
PrimateAI	Pathogenic	0.80	D
PROVEAN	Pathogenic	-5.5	D
REVEL	Pathogenic	0.91
Sift	Uncertain	0.0030	D
Sift4G	Uncertain	0.039	D
Polyphen		1.0	D
Vest4		0.91
MutPred		0.92		Loss of glycosylation at S11 (P = 0.0326)
MVP		0.99
MPC		1.8
ClinPred		0.99	D
GERP RS		4.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.94
gMVP		0.98
Mutation Taster		=4/96	disease causing (ClinVar)

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: rs1555936999; hg19: chrX-70443591;