15-26621395-T-C

Position:

• chr15-26621395-T-C

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate PP5

The NM_000814.6(GABRB3):​c.380A>G​(p.Lys127Arg) 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 Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. K127E) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: GABRB3 NM_000814.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 7.90

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]

ACMG classification

Verdict is Pathogenic. Variant got 10 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 4 uncertain in NM_000814.6
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr15-26621396-T-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 1067451.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), GABRB3. . Gene score misZ 3.3856 (greater than the threshold 3.09). Trascript score misZ 4.4544 (greater than threshold 3.09). GenCC has associacion of gene with childhood absence epilepsy, developmental and epileptic encephalopathy, 43, developmental and epileptic encephalopathy, Lennox-Gastaut syndrome, epilepsy, childhood absence, susceptibility to, 5.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.901
• PP5: Variant 15-26621395-T-C is Pathogenic according to our data. Variant chr15-26621395-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 374687.We mark this variant Likely_pathogenic, oryginal submissions are: {Pathogenic=2, Uncertain_significance=1}. Variant chr15-26621395-T-C is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GABRB3	NM_000814.6	c.380A>G	p.Lys127Arg	missense_variant	4/9	ENST00000311550.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GABRB3	ENST00000311550.10	c.380A>G	p.Lys127Arg	missense_variant	4/9	1	NM_000814.6	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:1 Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Jul 01, 2016	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Sep 28, 2022	Published functional studies demonstrate a damaging effect by significantly reducing GABA sensitivity and channel current amplitude (Absalom et al., 2022); Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 28053010, 32964447, 34906499, 31785789, 35383156) -

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

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Mar 06, 2020

For these reasons, this variant has been classified as Pathogenic. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site, but this prediction has not been confirmed by published transcriptional studies. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant has been observed to be de novo in individuals affected with early-onset absence epilepsy (PMID: 28053010, Invitae). ClinVar contains an entry for this variant (Variation ID: 374687). This variant is not present in population databases (ExAC no frequency). This sequence change replaces lysine with arginine at codon 127 of the GABRB3 protein (p.Lys127Arg). The lysine residue is highly conserved and there is a small physicochemical difference between lysine and arginine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.58
BayesDel_addAF	Pathogenic	0.22	D
BayesDel_noAF	Uncertain	0.090
CADD	Pathogenic	29
DANN	Pathogenic	1.0
DEOGEN2	Uncertain	0.72	.;D;.;.;.;.;.;.;.
Eigen	Pathogenic	0.82
Eigen_PC	Pathogenic	0.80
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.95	.;D;D;D;D;.;D;D;.
M_CAP	Pathogenic	0.39	D
MetaRNN	Pathogenic	0.90	D;D;D;D;D;D;D;D;D
MetaSVM	Uncertain	0.49	D
MutationAssessor	Uncertain	2.5	.;M;.;.;M;.;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D
PrimateAI	Pathogenic	0.87	D
PROVEAN	Uncertain	-2.7	.;D;.;D;D;.;.;D;D
REVEL	Pathogenic	0.76
Sift	Pathogenic	0.0	.;D;.;D;D;.;.;D;D
Sift4G	Pathogenic	0.0	D;D;D;D;D;.;.;D;D
Polyphen		1.0	.;D;.;D;D;.;.;.;.
Vest4		0.70
MutPred		0.73		.;.;.;Loss of methylation at K183 (P = 0.0165);.;.;.;.;.;
MVP		0.86
MPC		2.2
ClinPred		0.98	D
GERP RS		5.8
Varity_R		0.91
gMVP		0.84

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: rs1057519201; hg19: chr15-26866542;