16-8674701-G-T

Variant summary

Our verdict is Likely benign. Variant got -3 ACMG points: 2P and 5B. PM2 BP4_Strong BS1_Supporting

The NM_020686.6(ABAT):c.-52G>T variant causes a 5 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00122 in 152,334 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.0012 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: ABAT NM_020686.6 5_prime_UTR
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -1.02

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 -3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.77).
• BS1: Variant frequency is greater than expected in population nfe. gnomad4 allele frequency = 0.00122 (186/152334) while in subpopulation NFE AF= 0.00156 (106/68020). AF 95% confidence interval is 0.00132. There are 0 homozygotes in gnomad4. There are 102 alleles in male gnomad4 subpopulation. Median coverage is 32. This position pass quality control queck. Existence of Clinvar submissions makes me limit the strength of this signal to Supporting

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ABAT	NM_020686.6	c.-52G>T		5_prime_UTR_variant	1/16	ENST00000268251.13

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ABAT	ENST00000268251.13	c.-52G>T		5_prime_UTR_variant	1/16	1	NM_020686.6	P1
ABAT	ENST00000564714.5	c.-74G>T		5_prime_UTR_variant	1/6	3
ABAT	ENST00000563992.1	n.85G>T		non_coding_transcript_exon_variant	1/2	2

Frequencies

GnomAD3 genomes AF: 0.00122 AC: 186 AN: 152216 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.000288

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.000414

Gnomad FIN AF: 0.00631

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00156

Gnomad OTH AF: 0.00

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 54 Hom.: 0 Cov.: 0 AF XY: 0.00 AC XY: 0 AN XY: 36

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

GnomAD4 genome AF: 0.00122 AC: 186 AN: 152334 Hom.: 0 Cov.: 32 AF XY: 0.00137 AC XY: 102 AN XY: 74494

Gnomad4 AFR AF: 0.000240

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.000288

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.000414

Gnomad4 FIN AF: 0.00631

Gnomad4 NFE AF: 0.00156

Gnomad4 OTH AF: 0.00

Alfa AF: 0.00138 Hom.: 0

Bravo AF: 0.000608

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

Illumina Laboratory Services, Illumina

Jan 12, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.77
Cadd	Benign	2.6
Dann	Benign	0.55
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.0

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: rs532269694; hg19: chr16-8768558;