chr15-26621403-T-G

Variant names:

• chr15-26621403-T-G
• rs1057519550
• NM_000814.6:c.372A>C

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PP5_Very_Strong

The NM_000814.6(GABRB3):​c.372A>C​(p.Leu124Phe) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: GABRB3 NM_000814.6 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 1.03
• Publications: 3 publications found

Genes affected

GABRB3 (HGNC:4083): (gamma-aminobutyric acid type A receptor subunit beta3) This gene encodes a member of the ligand-gated ionic channel family. The encoded protein is one the subunits of a multi-subunit chloride channel that serves as the receptor for gamma-aminobutyric acid, a major inhibitory neurotransmitter of the mammalian nervous system. This gene is located on the long arm of chromosome 15 in a cluster with two other genes encoding related subunits of the family. This gene may be associated with the pathogenesis of several disorders including Angelman syndrome, Prader-Willi syndrome, nonsyndromic orofacial clefts, epilepsy and autism. Alternatively spliced transcript variants encoding distinct isoforms have been described. [provided by RefSeq, Jul 2013]

GABRB3 Gene-Disease associations (from GenCC):

• developmental and epileptic encephalopathy, 43

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
• epilepsy, childhood absence, susceptibility to, 5

  Inheritance: AD, Unknown Classification: DEFINITIVE, LIMITED Submitted by: G2P, Labcorp Genetics (formerly Invitae)
• genetic developmental and epileptic encephalopathy

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• childhood absence epilepsy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Lennox-Gastaut syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_000814.6
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 15-26621403-T-G is Pathogenic according to our data. Variant chr15-26621403-T-G is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 375532.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
GABRB3	NM_000814.6	c.372A>C	p.Leu124Phe	missense_variant	Exon 4 of 9	ENST00000311550.10	NP_000805.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GABRB3	ENST00000311550.10	c.372A>C	p.Leu124Phe	missense_variant	Exon 4 of 9	1	NM_000814.6	ENSP00000308725.5

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Epileptic encephalopathy Pathogenic:1

Nov 16, 2016

Neurogenetics Laboratory - MEYER, AOU Meyer

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Epilepsy, childhood absence, susceptibility to, 1;C2677087:Epilepsy, childhood absence, susceptibility to, 5 Pathogenic:1

Jan 07, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces leucine, which is neutral and non-polar, with phenylalanine, which is neutral and non-polar, at codon 124 of the GABRB3 protein (p.Leu124Phe). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of developmental and epileptic encephalopathy (PMID: 27864847, 34698933, 35383156). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 375532). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on GABRB3 protein function. Experimental studies have shown that this missense change affects GABRB3 function (PMID: 35383156). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.91
BayesDel_addAF	Pathogenic	0.27	D
BayesDel_noAF	Pathogenic	0.15
CADD	Uncertain	23
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.46	.;T;.;.;.;.;.;.;.
Eigen	Benign	0.012
Eigen_PC	Benign	-0.019
FATHMM_MKL	Uncertain	0.79	D
LIST_S2	Uncertain	0.96	.;D;D;D;D;.;D;D;.
M_CAP	Uncertain	0.17	D
MetaRNN	Uncertain	0.58	D;D;D;D;D;D;D;D;D
MetaSVM	Benign	-0.40	T
MutationAssessor	Uncertain	2.2	.;M;.;.;M;.;.;.;.
PhyloP100		1.0
PrimateAI	Pathogenic	0.89	D
PROVEAN	Benign	-2.2	.;N;.;N;N;.;.;N;N
REVEL	Uncertain	0.57
Sift	Uncertain	0.022	.;D;.;D;D;.;.;D;D
Sift4G	Uncertain	0.013	D;D;D;D;D;.;.;D;D
Polyphen		0.96, 0.95	.;D;.;P;P;.;.;.;.
Vest4		0.80
MutPred		0.51		.;.;.;Gain of catalytic residue at L180 (P = 0.0058);.;.;.;.;.;
MVP		0.95
MPC		2.5
ClinPred		0.89	D
GERP RS		0.95
Varity_R		0.67
gMVP		0.90
Mutation Taster		=5/95	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: rs1057519550; hg19: chr15-26866550;