16-8735758-G-A

Position:

• chr16-8735758-G-A

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_020686.6(ABAT):​c.19G>A​(p.Ala7Thr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000023 in 1,606,512 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.000039 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000021 (0 hom.)
• Consequence: ABAT NM_020686.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.733

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]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.033116043).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ABAT	NM_020686.6	c.19G>A	p.Ala7Thr	missense_variant	2/16	ENST00000268251.13

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ABAT	ENST00000268251.13	c.19G>A	p.Ala7Thr	missense_variant	2/16	1	NM_020686.6	P1

Frequencies

GnomAD3 genomes AF: 0.0000394 AC: 6 AN: 152132 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000483

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: 0.0000588

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000422 AC: 10 AN: 237066 Hom.: 0 AF XY: 0.0000468 AC XY: 6 AN XY: 128250

Gnomad AFR exome AF: 0.000202

Gnomad AMR exome AF: 0.0000599

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000698

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000280

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000213 AC: 31 AN: 1454262 Hom.: 0 Cov.: 31 AF XY: 0.0000208 AC XY: 15 AN XY: 722628

Gnomad4 AFR exome AF: 0.000120

Gnomad4 AMR exome AF: 0.0000457

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000473

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000171

Gnomad4 OTH exome AF: 0.0000333

GnomAD4 genome AF: 0.0000394 AC: 6 AN: 152250 Hom.: 0 Cov.: 32 AF XY: 0.0000403 AC XY: 3 AN XY: 74442

Gnomad4 AFR AF: 0.0000481

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: 0.0000588

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000865 Hom.: 0

ESP6500AA AF: 0.000228 AC: 1

ESP6500EA AF: 0.00 AC: 0

ExAC AF: 0.0000330 AC: 4

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

Jul 19, 2022

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 7 of the ABAT protein (p.Ala7Thr). This variant is present in population databases (rs141213694, gnomAD 0.02%). This variant has not been reported in the literature in individuals affected with ABAT-related conditions. ClinVar contains an entry for this variant (Variation ID: 945833). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The threonine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. 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	0.066
BayesDel_addAF	Benign	-0.26	T
BayesDel_noAF	Benign	-0.33
CADD	Benign	1.6
DANN	Benign	0.79
DEOGEN2	Benign	0.014	T;T;.;T;T;.;.;T;T
Eigen	Benign	-1.5
Eigen_PC	Benign	-1.5
FATHMM_MKL	Benign	0.0034	N
M_CAP	Benign	0.019	T
MetaRNN	Benign	0.033	T;T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.87	T
MutationAssessor	Benign	0.0	N;.;.;.;N;.;.;N;.
MutationTaster	Benign	1.0	N;N;N;N;N
PrimateAI	Benign	0.27	T
PROVEAN	Benign	0.13	N;N;N;N;N;N;N;N;N
REVEL	Uncertain	0.35
Sift	Benign	0.80	T;T;T;T;T;T;T;T;T
Sift4G	Benign	0.70	T;T;T;T;T;T;T;T;T
Polyphen		0.0	B;.;.;.;B;.;.;B;.
Vest4		0.16
MVP		0.45
MPC		0.30
ClinPred		0.0065	T
GERP RS		-3.9
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.0
Varity_R		0.032
gMVP		0.44

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: rs141213694; hg19: chr16-8829615;