1-2019488-C-T

Position:

• chr1-2019488-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_000815.5(GABRD):​c.65C>T​(p.Thr22Ile) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000181 in 1,105,478 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T22A) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.0000069 (0 hom., cov: 27)
  • Exomes 𝑓: 0.0000010 (0 hom.)
• Consequence: GABRD NM_000815.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.91

Genes affected

GABRD (HGNC:4084): (gamma-aminobutyric acid type A receptor subunit delta) Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian brain where it acts at GABA-A receptors, which are ligand-gated chloride channels. Chloride conductance of these channels can be modulated by agents such as benzodiazepines that bind to the GABA-A receptor. The GABA-A receptor is generally pentameric and there are five types of subunits: alpha, beta, gamma, delta, and rho. This gene encodes the delta subunit. Mutations in this gene have been associated with susceptibility to generalized epilepsy with febrile seizures, type 5. Alternatively spliced transcript variants have been described for this gene, but their biological validity has not been determined. [provided by RefSeq, Jul 2008]

GABRD (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.2973422).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GABRD	NM_000815.5	c.65C>T	p.Thr22Ile	missense_variant	1/9	ENST00000378585.7	NP_000806.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GABRD	ENST00000378585.7	c.65C>T	p.Thr22Ile	missense_variant	1/9	1	NM_000815.5	ENSP00000367848.4

Frequencies

GnomAD3 genomes AF: 0.00000689 AC: 1 AN: 145218 Hom.: 0 Cov.: 27

Gnomad AFR AF: 0.0000251

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000104 AC: 1 AN: 960260 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 450918

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: 0.00000118

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000689 AC: 1 AN: 145218 Hom.: 0 Cov.: 27 AF XY: 0.00 AC XY: 0 AN XY: 70802

Gnomad4 AFR AF: 0.0000251

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Idiopathic generalized epilepsy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Apr 04, 2019

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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has not been reported in the literature in individuals with GABRD-related conditions. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate insufficient coverage at this position in the ExAC database. This sequence change replaces threonine with isoleucine at codon 22 of the GABRD protein (p.Thr22Ile). The threonine residue is weakly conserved and there is a moderate physicochemical difference between threonine and isoleucine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.11
BayesDel_addAF	Benign	-0.077	T
BayesDel_noAF	Benign	-0.35
CADD	Benign	20
DANN	Uncertain	0.98
DEOGEN2	Benign	0.13	T;.;.;.;.;.
Eigen	Benign	-0.44
Eigen_PC	Benign	-0.35
FATHMM_MKL	Benign	0.062	N
LIST_S2	Benign	0.30	T;T;T;T;T;T
M_CAP	Pathogenic	0.89	D
MetaRNN	Benign	0.30	T;T;T;T;T;T
MetaSVM	Benign	-0.79	T
MutationAssessor	Benign	0.55	N;.;.;.;.;.
MutationTaster	Benign	1.0	N
PrimateAI	Pathogenic	0.86	D
PROVEAN	Benign	-0.60	N;.;.;.;.;.
REVEL	Benign	0.16
Sift	Benign	0.22	T;.;.;.;.;.
Sift4G	Benign	0.50	T;.;.;.;.;.
Polyphen		0.037	B;.;.;.;.;.
Vest4		0.13
MutPred		0.39		Gain of helix (P = 0.0854);Gain of helix (P = 0.0854);Gain of helix (P = 0.0854);Gain of helix (P = 0.0854);Gain of helix (P = 0.0854);.;
MVP		0.42
MPC		0.86
ClinPred		0.15	T
GERP RS		2.9
Varity_R		0.080
gMVP		0.38

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: rs1658715532; hg19: chr1-1950927;