chr16-8735781-C-G

Position:

• chr16-8735781-C-G

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_020686.6(ABAT):​c.42C>G​(p.Phe14Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000103 in 1,455,648 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 (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000010 (0 hom.)
• Consequence: ABAT NM_020686.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.294

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 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.07340622).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
ABAT	NM_020686.6	c.42C>G	p.Phe14Leu	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.42C>G	p.Phe14Leu	missense_variant	2/16	1	NM_020686.6	ENSP00000268251	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.0000103 AC: 15 AN: 1455648 Hom.: 0 Cov.: 31 AF XY: 0.00000691 AC XY: 5 AN XY: 723490

Gnomad4 AFR exome AF: 0.0000299

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: 0.0000126

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

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

Oct 13, 2023

This sequence change replaces phenylalanine, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 14 of the ABAT protein (p.Phe14Leu). 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: 576904). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Not Available"; PolyPhen-2: "Benign"; Align-GVGD: "Not Available". The leucine 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	0.19
BayesDel_addAF	Uncertain	0.020	T
BayesDel_noAF	Benign	-0.21
CADD	Benign	4.7
DANN	Benign	0.58
DEOGEN2	Benign	0.0061	T;T;.;T;T;.;.;T;T
Eigen	Benign	-1.0
Eigen_PC	Benign	-0.89
FATHMM_MKL	Benign	0.089	N
LIST_S2	Benign	0.60	.;T;T;T;T;T;T;.;T
M_CAP	Benign	0.011	T
MetaRNN	Benign	0.073	T;T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.98	T
MutationAssessor	Benign	-1.7	N;.;.;.;N;.;.;N;.
MutationTaster	Benign	1.0	N;N;N;N;N
PrimateAI	Benign	0.34	T
PROVEAN	Benign	0.27	N;N;D;N;N;N;N;N;N
REVEL	Uncertain	0.29
Sift	Benign	0.85	T;T;D;T;T;T;T;T;T
Sift4G	Benign	0.77	T;T;D;T;T;T;T;T;T
Polyphen		0.0	B;.;.;.;B;.;.;B;.
Vest4		0.18
MutPred		0.28		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);.;Gain of helix (P = 0.0854);Gain of helix (P = 0.0854);
MVP		0.62
MPC		0.36
ClinPred		0.040	T
GERP RS		3.1
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.070
gMVP		0.29

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: rs1567293995; hg19: chr16-8829638;