NM_021954.4:c.443C>T

Variant names:

• chr13-20142846-G-A
• rs1555339477
• NM_021954.4:c.443C>T

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_021954.4(GJA3):​c.443C>T​(p.Thr148Ile) 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. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: GJA3 NM_021954.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 9.87

Genes affected

GJA3 (HGNC:4277): (gap junction protein alpha 3) The protein encoded by this gene is a connexin and is a component of lens fiber gap junctions. Defects in this gene are a cause of zonular pulverulent cataract type 3 (CZP3). [provided by RefSeq, Jan 2010]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a disulfide_bond (size 138) in uniprot entity CXA3_HUMAN there are 9 pathogenic changes around while only 1 benign (90%) in NM_021954.4
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.923

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GJA3	NM_021954.4	c.443C>T	p.Thr148Ile	missense_variant	Exon 2 of 2	ENST00000241125.4	NP_068773.2
GJA3	XM_011535048.3	c.443C>T	p.Thr148Ile	missense_variant	Exon 2 of 2		XP_011533350.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GJA3	ENST00000241125.4	c.443C>T	p.Thr148Ile	missense_variant	Exon 2 of 2	3	NM_021954.4	ENSP00000241125.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 35

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cataract 14 multiple types Uncertain:2

Jan 21, 2023

Dept. Genetics and Cancer, Menzies Institute for Medical Research, University of Tasmania

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: curation

Variant identified and curated during a GJA3 specific review of the literature in relation to pediatric or congenital cataract. ACMG-AMP criteria applied: PM2(Supporting), PP1, PP3. Original variant report: PMID:28877251. The cataract phenotype reported for this variant is: Pulverulent nuclear. Gene review and curation guidelines are outlined in: https://doi.org/10.1080/17469899.2023.2160320 -

Sep 13, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces threonine with isoleucine at codon 148 of the GJA3 protein (p.Thr148Ile). The threonine residue is highly conserved and there is a moderate physicochemical difference between threonine and isoleucine. This variant is not present in population databases (ExAC no frequency). This variant has been reported to segregate with bilateral pulverulent nuclear cataracts in multiple affected individuals from a single family (PMID: 28877251). Experimental studies have shown that this missense change alters the normal expression level and the distribution of protein in cells (PMID: 28877251). However, the clinical significant of this finding is unknown. 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
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.43	D
BayesDel_noAF	Pathogenic	0.37
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.72	D
Eigen	Pathogenic	0.71
Eigen_PC	Pathogenic	0.67
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.93	D
M_CAP	Pathogenic	0.69	D
MetaRNN	Pathogenic	0.92	D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	3.3	M
PrimateAI	Pathogenic	0.82	D
PROVEAN	Pathogenic	-5.5	D
REVEL	Pathogenic	0.86
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		0.99	D
Vest4		0.77
MutPred		0.58		Gain of catalytic residue at N152 (P = 0.011);
MVP		0.94
MPC		2.1
ClinPred		1.0	D
GERP RS		5.1
Varity_R		0.91
gMVP		0.97

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: rs1555339477; hg19: chr13-20716985;