rs781163821

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PVS1_ModeratePM2

The NM_000156.6(GAMT):c.668_669insA(p.Tyr223Ter) variant causes a stop gained, frameshift change. The variant allele was found at a frequency of 0.00000186 in 1,612,302 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★★). Synonymous variant affecting the same amino acid position (i.e. Y223Y) has been classified as Likely benign.

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 33)

Exomes 𝑓: 0.0000014 ( 0 hom. )

Consequence

GAMT
NM_000156.6 stop_gained, frameshift

Scores

Not classified

Clinical Significance

Uncertain significance reviewed by expert panel U:4

Conservation

PhyloP100: 6.00

Variant links:

Genes affected

GAMT (HGNC:4136): (guanidinoacetate N-methyltransferase) The protein encoded by this gene is a methyltransferase that converts guanidoacetate to creatine, using S-adenosylmethionine as the methyl donor. Defects in this gene have been implicated in neurologic syndromes and muscular hypotonia, probably due to creatine deficiency and accumulation of guanidinoacetate in the brain of affected individuals. Two transcript variants encoding different isoforms have been described for this gene. Pseudogenes of this gene are found on chromosomes 2 and 13. [provided by RefSeq, Feb 2012]

GAMT links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 4 ACMG points.

PVS1

Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.0605 CDS is truncated, and there are 0 pathogenic variants in the truncated region.

PM2

Very rare variant in population databases, with high coverage;

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAMT	NM_000156.6 linkuse as main transcript	c.668_669insA	p.Tyr223Ter	stop_gained, frameshift_variant	6/6	ENST00000252288.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAMT	ENST00000252288.8 linkuse as main transcript	c.668_669insA	p.Tyr223Ter	stop_gained, frameshift_variant	6/6	1	NM_000156.6	P1	Q14353-1
GAMT	ENST00000640762.1 linkuse as main transcript	c.599_600insA	p.Tyr200Ter	stop_gained, frameshift_variant	6/6	5
GAMT	ENST00000640164.1 linkuse as main transcript	n.501_502insA		non_coding_transcript_exon_variant	4/4	2

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152200

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.00000403

AC:

AN:

248204

Hom.:

AF XY:

0.00000742

AC XY:

AN XY:

134760

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00000890

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000137

AC:

AN:

1460102

Hom.:

Cov.:

AF XY:

0.00000275

AC XY:

AN XY:

726362

show subpopulations

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

AF:

0.00000657

AC:

AN:

152200

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74352

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000147

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000712

Hom.:

Bravo

AF:

0.0000113

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: reviewed by expert panel

LINK: link

Submissions by phenotype

Deficiency of guanidinoacetate methyltransferase

Uncertain:2

Uncertain significance, reviewed by expert panel	curation	ClinGen Cerebral Creatine Deficiency Syndromes Variant Curation Expert Panel, ClinGen	Jun 06, 2022	The NM_000156.6:c.668dupA (p.Tyr223fs) variant in GAMT is a frameshift variant in the last exon (exon 6/6; amino acid 223/237) of GAMT, and is therefore predicted to escape nonsense mediated decay. Less than 10% of the protein is predicted to be removed (PVS1_Moderate). The variant is absent in gnomAD v2.1.1 (PM2_Supporting). To our knowledge, this variant has not been reported in published literature in individuals with GAMT deficiency. It is noted in ClinVar (Variation ID 445930). In summary, this variant meets the criteria to be classified as a variant of uncertain significance for GAMT deficiency. GAMT-specific ACMG/AMP codes met, as specified by the ClinGen Cerebral Creatine Deficiency Syndromes VCEP (Specifications Version 1.1.0): PM2_Supporting, BP4. (Classification approved by the ClinGen CCDS VCEP on June 6, 2022). -
Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Center for Pediatric Genomic Medicine, Children's Mercy Hospital and Clinics

Aug 16, 2017

- -

Cerebral creatine deficiency syndrome

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jul 26, 2022

Experimental studies and prediction algorithms are not available or were not evaluated, and the functional significance of this variant is currently unknown. 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. ClinVar contains an entry for this variant (Variation ID: 445930). This variant has not been reported in the literature in individuals affected with GAMT-related conditions. This variant is present in population databases (rs781163821, gnomAD 0.002%). This sequence change creates a premature translational stop signal (p.Tyr223*) in the GAMT gene. While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 14 amino acid(s) of the GAMT protein. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over