rs922847767

Positions:

• chr9-98371535-C-T

Variant summary

Our verdict is Pathogenic. Variant got 15 ACMG points: 15P and 0B. PM2 PM5 PP2 PP3_Moderate PP5_Very_Strong

The NM_005458.8(GABBR2):​c.1699G>A​(p.Ala567Thr) 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 Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A567V) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: GABBR2 NM_005458.8 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:12
• Conservation: PhyloP100: 7.51

Genes affected

GABBR2 (HGNC:4507): (gamma-aminobutyric acid type B receptor subunit 2) The multi-pass membrane protein encoded by this gene belongs to the G-protein coupled receptor 3 family and GABA-B receptor subfamily. The GABA-B receptors inhibit neuronal activity through G protein-coupled second-messenger systems, which regulate the release of neurotransmitters, and the activity of ion channels and adenylyl cyclase. This receptor subunit forms an active heterodimeric complex with GABA-B receptor subunit 1, neither of which is effective on its own. Allelic variants of this gene have been associated with nicotine dependence.[provided by RefSeq, Jan 2010]

ACMG classification

Verdict is Pathogenic. Variant got 15 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr9-98371534-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 1073462.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), GABBR2. . Gene score misZ 4.6253 (greater than the threshold 3.09). Trascript score misZ 4.0975 (greater than threshold 3.09). GenCC has associacion of gene with developmental and epileptic encephalopathy, 59, neurodevelopmental disorder with poor language and loss of hand skills, atypical Rett syndrome.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.87
• PP5: Variant 9-98371535-C-T is Pathogenic according to our data. Variant chr9-98371535-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 446211.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr9-98371535-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GABBR2	NM_005458.8	c.1699G>A	p.Ala567Thr	missense_variant	12/19	ENST00000259455.4
GABBR2	XM_017015331.3	c.1405G>A	p.Ala469Thr	missense_variant	11/18
GABBR2	XM_005252316.6	c.925G>A	p.Ala309Thr	missense_variant	10/17
GABBR2	XM_017015332.3	c.925G>A	p.Ala309Thr	missense_variant	9/16

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GABBR2	ENST00000259455.4	c.1699G>A	p.Ala567Thr	missense_variant	12/19	1	NM_005458.8	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1459618 Hom.: 0 Cov.: 28 AF XY: 0.00 AC XY: 0 AN XY: 726324

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:12

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Neurodevelopmental disorder with poor language and loss of hand skills Pathogenic:4

Pathogenic, no assertion criteria provided	literature only	OMIM	Mar 15, 2018	- -
Pathogenic, criteria provided, single submitter	clinical testing	3billion	Oct 02, 2021	Same nucleotide change resulting in same amino acid change has been previously reported multiple times as de novo in similarly affected indivisual (PMID: 25533962, 28688840 PS2, PS4_M). It is not observed in the gnomAD v2.1.1 dataset (PM2). In silico tool predictions suggest damaging effect of the variant on gene or gene product (REVEL: 0.843, 3Cnet: 0.995, PP3). Therefore, this variant is classified as pathogenic according to the recommendation of ACMG/AMP guideline. -
Pathogenic, no assertion criteria provided	clinical testing	Zotz-Klimas Genetics Lab, MVZ Zotz Klimas	Oct 30, 2023	- -
Pathogenic, criteria provided, single submitter	clinical testing	Institute of Human Genetics Munich, Klinikum Rechts Der Isar, TU München	Nov 03, 2020	- -

not provided Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Apr 01, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Institute of Medical Genetics and Applied Genomics, University Hospital Tübingen	Oct 23, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Greenwood Genetic Center Diagnostic Laboratories, Greenwood Genetic Center	Jul 28, 2020	PS2, PS4, PP3, PM2 -

GABBR2-related disorder Pathogenic:2

Pathogenic, no assertion criteria provided	clinical testing	PreventionGenetics, part of Exact Sciences	Jul 22, 2024	The GABBR2 c.1699G>A variant is predicted to result in the amino acid substitution p.Ala567Thr. This variant has been reported as a recurrent de novo variant in individuals with Rett-syndrome-like phenotypes and non-specified neurodevelopmental disorders (see, for example, Lopes et al. 2016. PubMed ID: 26740508; Lucariello et al. 2016. PubMed ID: 27541642; Table S1, Takata et al. 2018. PubMed ID: 29346770; Yoo et al. 2017. PubMed ID: 28856709). This variant has not been reported in a large population database, indicating this variant is rare. Another missense variant affecting the same amino acid (p.Ala567Val) has been reported in an individual with autism spectrum disorder (Supplementary Data 1, Zhou et al. 2022. PubMed ID: 35982159). This variant is interpreted as pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Rady Children's Institute for Genomic Medicine, Rady Children's Hospital San Diego	-	This variant has been previously reported as a de novo heterozygous change in multiple unrelated patients with autism spectrum disorder, motor and language developmental delay, developmental regression, stereotypies, sleep disturbance, and muscular hypotonia with or without epileptic encephalopathy (PMID: 26740508, 27541642, 28191890, 28856709, 28867141, 29346770). A different amino acid change at the same residue (p.Ala567Val) has been observed in individuals with similar clinical phenotype and in at least one of these individuals, this variant was detected to be de novo (Variation ID: 1073462, Invitae internal data). The GABBR2 gene is constrained against variation (Z-score= 4.63 and pLI = 1) and missense variants are a common mechanism of disease (HGMD, ClinVar database). Experimental studies showed that presence of the p.Ala567Thr variant resulted in abnormal protein activity in HEK293 cells without altering protein expression and subcellular localization; furthermore, this variant caused abnormal behaviors in tadpoles (PMID: 28856709). The c.1699G>A (p.Ala567Thr) variant is absent from the gnomAD population database and thus is presumed to be rare. Analysis of the parental samples was negative for the variant, indicating this variant likely occurred as a de novo event. Based on the available evidence, the c.1699G>A (p.Ala567Thr) variant is classified as Pathogenic. -

Rett syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

case-control;in vitro;in vivo;research

Choi Lab, Seoul National University

Sep 22, 2017

We identified a recurring de novo variant in GABAB receptor R2 (GABBR2) that reduces the receptor function, whereas different GABBR2 variants in EE patients possess a more profound effect in reducing receptor activity and are more responsive to agonist rescue in an animal model. GABBR2 is a genetic factor that determines RTT- or EE-like phenotype expression depending on the variant positions. GABBR2-mediated γ-aminobutyric acid signaling is a crucial factor in determining the severity and nature of neurodevelopmental phenotypes. -

Inborn genetic diseases Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Aug 03, 2016

- -

Epileptic encephalopathy Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 28, 2023

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 567 of the GABBR2 protein (p.Ala567Thr). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with GABBR2-related conditions (PMID: 26740508, 27541642, 28856709). In at least one individual the variant was observed to be de novo. ClinVar contains an entry for this variant (Variation ID: 446211). 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) performed at Invitae indicates that this missense variant is not expected to disrupt GABBR2 protein function with a negative predictive value of 80%. Experimental studies have shown that this missense change affects GABBR2 function (PMID: 28856709). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.82
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.11
CADD	Pathogenic	28
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.64	D;.
Eigen	Pathogenic	0.88
Eigen_PC	Pathogenic	0.84
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.86	D;D
M_CAP	Pathogenic	0.34	D
MetaRNN	Pathogenic	0.87	D;D
MetaSVM	Pathogenic	0.86	D
MutationAssessor	Benign	1.8	L;.
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.87	D
PROVEAN	Uncertain	-3.5	D;.
REVEL	Pathogenic	0.75
Sift	Uncertain	0.0020	D;.
Sift4G	Uncertain	0.0060	D;.
Polyphen		1.0	D;.
Vest4		0.75
MutPred		0.67		Gain of MoRF binding (P = 0.1367);.;
MVP		0.85
MPC		1.3
ClinPred		0.98	D
GERP RS		5.4
Varity_R		0.88
gMVP		0.90

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs922847767; hg19: chr9-101133817;