16-8779483-G-T

Position:

• chr16-8779483-G-T

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_020686.6(ABAT):​c.1274G>T​(p.Arg425Leu) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,461,658 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic 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. R425Q) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: ABAT NM_020686.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.72

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 Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.791

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ABAT	NM_020686.6	c.1274G>T	p.Arg425Leu	missense_variant	15/16	ENST00000268251.13

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ABAT	ENST00000268251.13	c.1274G>T	p.Arg425Leu	missense_variant	15/16	1	NM_020686.6	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461658 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727130

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: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

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

Labcorp Genetics (formerly Invitae), Labcorp

Jul 12, 2022

This sequence change replaces arginine, which is basic and polar, with leucine, which is neutral and non-polar, at codon 425 of the ABAT protein (p.Arg425Leu). This variant is not present in population databases (gnomAD no frequency). 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: 1001431). 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. 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	0.15
BayesDel_addAF	Uncertain	0.050	T
BayesDel_noAF	Benign	-0.17
CADD	Benign	20
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.61	D;D;.;D;D
Eigen	Benign	-0.065
Eigen_PC	Benign	0.032
FATHMM_MKL	Uncertain	0.91	D
LIST_S2	Benign	0.80	.;T;T;.;T
M_CAP	Benign	0.037	D
MetaRNN	Pathogenic	0.79	D;D;D;D;D
MetaSVM	Benign	-0.39	T
MutationAssessor	Uncertain	2.3	M;M;.;M;.
MutationTaster	Benign	0.95	D;D;D;D;D
PrimateAI	Benign	0.33	T
PROVEAN	Uncertain	-4.0	D;D;D;D;D
REVEL	Uncertain	0.48
Sift	Uncertain	0.015	D;D;D;D;D
Sift4G	Uncertain	0.040	D;D;D;D;D
Polyphen		0.0050	B;B;.;B;.
Vest4		0.66
MutPred		0.63		Gain of helix (P = 0.0199);Gain of helix (P = 0.0199);.;Gain of helix (P = 0.0199);Gain of helix (P = 0.0199);
MVP		0.79
MPC		0.39
ClinPred		0.94	D
GERP RS		3.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.33
gMVP		0.80

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: rs368127499; hg19: chr16-8873340;