16-8735753-T-G

Position:

• chr16-8735753-T-G

Variant summary

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

The NM_020686.6(ABAT):​c.14T>G​(p.Leu5Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000206 in 1,453,938 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: ABAT NM_020686.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.32

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 2 ACMG points.

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

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
ABAT	NM_020686.6	c.14T>G	p.Leu5Trp	missense_variant	2/16	ENST00000268251.13	NP_065737.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
ABAT	ENST00000268251.13	c.14T>G	p.Leu5Trp	missense_variant	2/16	1	NM_020686.6	ENSP00000268251	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000206 AC: 3 AN: 1453938 Hom.: 0 Cov.: 31 AF XY: 0.00000277 AC XY: 2 AN XY: 722386

Gnomad4 AFR exome AF: 0.0000897

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000756

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

Jan 26, 2022

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 are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals affected with ABAT-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces leucine, which is neutral and non-polar, with tryptophan, which is neutral and slightly polar, at codon 5 of the ABAT protein (p.Leu5Trp). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.11
BayesDel_addAF	Uncertain	0.11	D
BayesDel_noAF	Benign	-0.090
CADD	Uncertain	24
DANN	Benign	0.95
DEOGEN2	Benign	0.039	T;T;.;T;T;.;.;T;T
Eigen	Uncertain	0.27
Eigen_PC	Benign	0.21
FATHMM_MKL	Uncertain	0.82	D
LIST_S2	Benign	0.79	.;T;T;T;T;T;T;.;T
M_CAP	Uncertain	0.15	D
MetaRNN	Uncertain	0.48	T;T;T;T;T;T;T;T;T
MetaSVM	Uncertain	0.17	D
MutationAssessor	Uncertain	2.1	M;.;.;.;M;.;.;M;.
MutationTaster	Benign	1.0	D;D;D;D;D
PrimateAI	Uncertain	0.51	T
PROVEAN	Benign	-1.1	N;N;D;D;N;N;N;N;N
REVEL	Uncertain	0.48
Sift	Uncertain	0.0010	D;D;D;D;D;D;D;D;D
Sift4G	Uncertain	0.011	D;D;D;D;D;D;T;D;D
Polyphen		0.98	D;.;.;.;D;.;.;D;.
Vest4		0.53
MutPred		0.28		Gain of MoRF binding (P = 0.0031);.;Gain of MoRF binding (P = 0.0031);Gain of MoRF binding (P = 0.0031);Gain of MoRF binding (P = 0.0031);Gain of MoRF binding (P = 0.0031);.;Gain of MoRF binding (P = 0.0031);Gain of MoRF binding (P = 0.0031);
MVP		0.95
MPC		1.2
ClinPred		0.79	D
GERP RS		4.1
Varity_R		0.22
gMVP		0.80

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: rs1346245434; hg19: chr16-8829610;