16-8781311-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_020686.6(ABAT):c.1384G>A(p.Val462Met) variant causes a missense, splice region change. The variant allele was found at a frequency of 0.00000496 in 1,613,980 control chromosomes in the GnomAD database, with no homozygous occurrence. 1/1 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 31)
  • Exomes 𝑓: 0.0000048 (0 hom.)
• Consequence: ABAT NM_020686.6 missense, splice_region
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.84

Genes affected

ABAT (HGNC:23): (4-aminobutyrate aminotransferase) 4-aminobutyrate aminotransferase (ABAT) is responsible for catabolism of gamma-aminobutyric acid (GABA), an important, mostly inhibitory neurotransmitter in the central nervous system, into succinic semialdehyde. The active enzyme is a homodimer of 50-kD subunits complexed to pyridoxal-5-phosphate. The protein sequence is over 95% similar to the pig protein. GABA is estimated to be present in nearly one-third of human synapses. ABAT in liver and brain is controlled by 2 codominant alleles with a frequency in a Caucasian population of 0.56 and 0.44. The ABAT deficiency phenotype includes psychomotor retardation, hypotonia, hyperreflexia, lethargy, refractory seizures, and EEG abnormalities. Multiple alternatively spliced transcript variants encoding the same protein isoform have been found for this gene. [provided by RefSeq, Jul 2008]

TMEM186 (HGNC:24530): (transmembrane protein 186) This gene encodes a potential transmembrane protein. [provided by RefSeq, Dec 2012]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ABAT	NM_020686.6	c.1384G>A	p.Val462Met	missense_variant, splice_region_variant	16/16	ENST00000268251.13

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ABAT	ENST00000268251.13	c.1384G>A	p.Val462Met	missense_variant, splice_region_variant	16/16	1	NM_020686.6	P1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152166 Hom.: 0 Cov.: 31

Gnomad AFR AF: 0.00

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: 0.000478

GnomAD3 exomes AF: 0.0000159 AC: 4 AN: 251410 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135892

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.000163

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.000163

GnomAD4 exome AF: 0.00000479 AC: 7 AN: 1461814 Hom.: 0 Cov.: 34 AF XY: 0.00000275 AC XY: 2 AN XY: 727212

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000101

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152166 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 74320

Gnomad4 AFR AF: 0.00

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: 0.000478

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Gamma-aminobutyric acid transaminase deficiency Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

May 25, 2022

This sequence change replaces valine, which is neutral and non-polar, with methionine, which is neutral and non-polar, at codon 462 of the ABAT protein (p.Val462Met). This variant is present in population databases (rs779818625, gnomAD 0.02%). This variant has not been reported in the literature in individuals affected with ABAT-related conditions. 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: "Benign"; Align-GVGD: "Class C0"). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.28
BayesDel_addAF	Uncertain	0.014	T
BayesDel_noAF	Uncertain	0.050
Cadd	Uncertain	24
Dann	Uncertain	1.0
DEOGEN2	Uncertain	0.58	D;D;.;D
Eigen	Uncertain	0.42
Eigen_PC	Uncertain	0.41
FATHMM_MKL	Pathogenic	0.98	D
M_CAP	Uncertain	0.15	D
MetaRNN	Uncertain	0.64	D;D;D;D
MetaSVM	Uncertain	-0.025	T
MutationAssessor	Uncertain	2.9	M;M;.;M
MutationTaster	Benign	1.0	D;D;D;D;D
PrimateAI	Benign	0.45	T
PROVEAN	Uncertain	-2.4	N;N;N;N
REVEL	Pathogenic	0.71
Sift	Uncertain	0.0010	D;D;D;D
Sift4G	Uncertain	0.0020	D;D;D;D
Polyphen		0.73	P;P;.;P
Vest4		0.51
MutPred		0.53		Loss of catalytic residue at V462 (P = 0.0201);Loss of catalytic residue at V462 (P = 0.0201);.;Loss of catalytic residue at V462 (P = 0.0201);
MVP		0.78
MPC		0.55
ClinPred		0.88	D
GERP RS		4.2
Varity_R		0.44
gMVP		0.77

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.14		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: rs779818625; hg19: chr16-8875168;