chr2-170818625-T-A

Position:

• chr2-170818625-T-A

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_000817.3(GAD1):​c.34T>A​(p.Ser12Thr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000363 in 1,461,890 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign 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. S12C) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 0.000036 (0 hom.)
• Consequence: GAD1 NM_000817.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.30

Genes affected

GAD1 (HGNC:4092): (glutamate decarboxylase 1) This gene encodes one of several forms of glutamic acid decarboxylase, identified as a major autoantigen in insulin-dependent diabetes. The enzyme encoded is responsible for catalyzing the production of gamma-aminobutyric acid from L-glutamic acid. A pathogenic role for this enzyme has been identified in the human pancreas since it has been identified as an autoantigen and an autoreactive T cell target in insulin-dependent diabetes. This gene may also play a role in the stiff man syndrome. Deficiency in this enzyme has been shown to lead to pyridoxine dependency with seizures. Alternative splicing of this gene results in two products, the predominant 67-kD form and a less-frequent 25-kD form. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), GAD1. . Gene score misZ 2.3151 (greater than the threshold 3.09). Trascript score misZ 3.7409 (greater than threshold 3.09). GenCC has associacion of gene with cerebral palsy, spastic quadriplegic, 1, developmental and epileptic encephalopathy 89, early infantile epileptic encephalopathy, spastic quadriplegic cerebral palsy, neurodevelopmental disorder with progressive spasticity and brain white matter abnormalities.
• BP4: Computational evidence support a benign effect (MetaRNN=0.09773141).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAD1	NM_000817.3	c.34T>A	p.Ser12Thr	missense_variant	2/17	ENST00000358196.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAD1	ENST00000358196.8	c.34T>A	p.Ser12Thr	missense_variant	2/17	1	NM_000817.3	P1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD3 exomes AF: 0.0000438 AC: 11 AN: 251288 Hom.: 0 AF XY: 0.0000294 AC XY: 4 AN XY: 135848

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.0000462

Gnomad NFE exome AF: 0.0000792

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000363 AC: 53 AN: 1461890 Hom.: 0 Cov.: 31 AF XY: 0.0000344 AC XY: 25 AN XY: 727246

Gnomad4 AFR exome AF: 0.0000299

Gnomad4 AMR exome AF: 0.0000224

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.0000374

Gnomad4 NFE exome AF: 0.0000432

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 31

Alfa AF: 0.0000282 Hom.: 0

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000116 AC: 1

ExAC AF: 0.0000247 AC: 3

EpiCase AF: 0.0000545

EpiControl AF: 0.000119

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Neurodevelopmental disorder with progressive spasticity and brain white matter abnormalities Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 16, 2018

This sequence change replaces serine with threonine at codon 12 of the GAD1 protein (p.Ser12Thr). The serine residue is highly conserved and there is a small physicochemical difference between serine and threonine. 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: "Benign"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with GAD1-related disease. This variant is present in population databases (rs149074954, ExAC 0.005%). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.071
BayesDel_addAF	Benign	-0.19	T
BayesDel_noAF	Benign	-0.32
CADD	Benign	19
DANN	Benign	0.97
DEOGEN2	Benign	0.23	.;.;.;T;.;.;.;.
Eigen	Benign	-0.40
Eigen_PC	Benign	-0.25
FATHMM_MKL	Benign	0.74	D
LIST_S2	Benign	0.67	T;T;T;T;T;.;T;T
M_CAP	Benign	0.066	D
MetaRNN	Benign	0.098	T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.73	T
MutationAssessor	Benign	0.69	.;.;N;N;N;N;.;.
MutationTaster	Benign	0.87	N;N;N
PrimateAI	Benign	0.46	T
PROVEAN	Benign	-1.2	N;N;.;N;N;N;N;N
REVEL	Benign	0.094
Sift	Benign	0.40	T;T;.;T;T;T;T;T
Sift4G	Pathogenic	0.0	D;D;D;D;D;D;D;D
Polyphen		0.0	.;.;.;B;B;B;.;.
Vest4		0.32, 0.29, 0.23, 0.23
MVP		0.65
MPC		0.53
ClinPred		0.080	T
GERP RS		2.0
Varity_R		0.063
gMVP		0.36

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: rs149074954; hg19: chr2-171675135;