NM_198904.4:c.769G>A

Variant names:

• chr5-162104026-G-A
• rs1554098235
• NM_198904.4:c.769G>A

Variant summary

Our verdict is Pathogenic. The variant received 14 ACMG points: 14P and 0B. PM2 PP3_Strong PP5_Very_Strong

The NM_198904.4(GABRG2):​c.769G>A​(p.Gly257Arg) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,646 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 17/26 in silico tools predict a damaging outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: GABRG2 NM_198904.4 missense, splice_region
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 9.88
• Publications: 4 publications found

Genes affected

GABRG2 (HGNC:4087): (gamma-aminobutyric acid type A receptor subunit gamma2) This gene encodes a gamma-aminobutyric acid (GABA) receptor. GABA is the major inhibitory neurotransmitter in the mammlian brain, where it acts at GABA-A receptors, which are ligand-gated chloride channels. GABA-A receptors are pentameric, consisting of proteins from several subunit classes: alpha, beta, gamma, delta and rho. Mutations in this gene have been associated with epilepsy and febrile seizures. Multiple transcript variants encoding different isoforms have been identified for this gene. [provided by RefSeq, Jul 2008]

GABRG2 Gene-Disease associations (from GenCC):

• epilepsy

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• developmental and epileptic encephalopathy, 74

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• febrile seizures, familial, 8

  Inheritance: AD Classification: STRONG Submitted by: Ambry Genetics, G2P, Labcorp Genetics (formerly Invitae)
• Dravet syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• generalized epilepsy with febrile seizures plus

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• self-limited epilepsy with centrotemporal spikes

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• undetermined early-onset epileptic encephalopathy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 14 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing predictors support a deleterious effect. Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 5-162104026-G-A is Pathogenic according to our data. Variant chr5-162104026-G-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 433102.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GABRG2	NM_198904.4	c.769G>A	p.Gly257Arg	missense_variant, splice_region_variant	Exon 6 of 10	ENST00000639213.2	NP_944494.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GABRG2	ENST00000639213.2	c.769G>A	p.Gly257Arg	missense_variant, splice_region_variant	Exon 6 of 10	1	NM_198904.4	ENSP00000491909.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461646 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727126

African (AFR) AF: 0.00 AC: 0 AN: 33472

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26128

East Asian (EAS) AF: 0.0000252 AC: 1 AN: 39630

South Asian (SAS) AF: 0.00 AC: 0 AN: 86256

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53406

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111876

Other (OTH) AF: 0.0000166 AC: 1 AN: 60388

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

EPILEPSY, CHILDHOOD ABSENCE, SUSCEPTIBILITY TO, 2;C1969810:Febrile seizures, familial, 8 Pathogenic:1

Oct 30, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glycine, which is neutral and non-polar, with arginine, which is basic and polar, at codon 257 of the GABRG2 protein (p.Gly257Arg). This variant also falls at the last nucleotide of exon 6, which is part of the consensus splice site for this exon. This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with clinical features of GABRG2-related conditions (PMID: 25726841; internal data). ClinVar contains an entry for this variant (Variation ID: 433102). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. Experimental studies have shown that this missense change affects GABRG2 function (PMID: 25726841). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -

Self-limited epilepsy with centrotemporal spikes Pathogenic:1

Jan 01, 2017

Bioinformatics Core, Luxembourg Center for Systems Biomedicine

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: case-control

CAADphred>15 -

not provided Pathogenic:1

Dec 14, 2023

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Reported in individuals with rolandic epilepsy in published literature (PMID: 25726841, 29358611); Published functional studies demonstrate a damaging effect on cell surface localization and levels of palmitoylation required for protein trafficking to the cell membrane (PMID: 25726841); Not observed at significant frequency in large population cohorts (gnomAD); The last nucleotide of exon variant in a gene for which loss of function is a known mechanism of disease, and both splice predictors and evolutionary conservation support a deleterious effect, although in the absence of functional evidence the actual effect of this sequence change is unknown.; This variant is associated with the following publications: (PMID: 28351718, 30851244, 29358611, 25726841, 36979350, 33004838) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.36
CADD	Pathogenic	35
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.88	.;.;.;.;.;.;D;.;.;.;.;.;.;.
Eigen	Pathogenic	0.91
Eigen_PC	Pathogenic	0.82
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.94	D;D;D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.43	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Uncertain	0.64	D
MutationAssessor	Pathogenic	3.1	.;.;.;.;M;.;M;.;.;.;.;.;.;.
PhyloP100		9.9
PrimateAI	Pathogenic	0.85	D
PROVEAN	Pathogenic	-7.6	.;.;.;.;.;.;.;.;.;.;.;D;.;.
REVEL	Pathogenic	0.88
Sift	Pathogenic	0.0	.;.;.;.;.;.;.;.;.;.;.;D;.;.
Sift4G	Uncertain	0.0090	.;.;.;.;.;.;.;.;.;.;.;D;.;.
Polyphen		1.0	.;.;.;.;D;.;D;.;.;.;.;.;.;.
Vest4		0.87
MutPred		0.88		.;.;.;.;Loss of ubiquitination at K253 (P = 0.0421);.;Loss of ubiquitination at K253 (P = 0.0421);.;Loss of ubiquitination at K253 (P = 0.0421);.;Loss of ubiquitination at K253 (P = 0.0421);.;.;Loss of ubiquitination at K253 (P = 0.0421);
MVP		0.89
MPC		2.8
ClinPred		1.0	D
GERP RS		5.4
Varity_R		0.92
gMVP		0.97
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.99
SpliceAI score (max)		0.52		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.52		Position offset: 0

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs1554098235; hg19: chr5-161531032; COSMIC: COSV62721042; COSMIC: COSV62721042;