X-71223337-T-G

Position:

• chrX-71223337-T-G

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PVS1 PM2 PP3_Strong

The NM_000166.6(GJB1):​c.-17+2T>G variant causes a splice donor change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 22)
• Consequence: GJB1 NM_000166.6 splice_donor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.57

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 14 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 5.1, offset of 29, new splice context is: cagGTctgg. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. No scorers claiming Uncertain. Scorers claiming Benign: max_spliceai.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GJB1	NM_000166.6	c.-17+2T>G		splice_donor_variant		ENST00000361726.7
GJB1	NM_001097642.3	c.-16-355T>G		intron_variant
GJB1	XM_011530907.3	c.-16-355T>G		intron_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GJB1	ENST00000361726.7	c.-17+2T>G		splice_donor_variant		1	NM_000166.6	P1

Frequencies

GnomAD3 genomes Cov.: 22

GnomAD4 exome Cov.: 0

GnomAD4 genome Cov.: 22

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Charcot-Marie-Tooth Neuropathy X Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 05, 2023

This variant occurs in a non-coding region of the GJB1 gene. It does not change the encoded amino acid sequence of the GJB1 protein. It affects a nucleotide within the consensus splice site. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate insufficient coverage at this position in the gnomAD database. This variant has been observed in individual(s) with clinical features of Charcot-Marie-Tooth disease (Invitae). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.44
CADD	Pathogenic	27
DANN	Uncertain	0.99

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.84
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

No publications associated with this variant yet.

Other links and lift over

hg19: chrX-70443187;