rs568392459

Positions:

• chr19-1399931-C-G

Variant summary

Our verdict is Uncertain significance. Variant got -1 ACMG points: 1P and 2B. BP4 PM2_Supporting BP7

This summary comes from the ClinGen Evidence Repository: The NM_000156.6:c.189G>C (p.Arg63=) variant in GAMT is a synonymous (silent) variant that is not predicted by SpliceAI to impact splicing. In addition, it occurs at a nucleotide that is not conserved as shown by phyloP (score -1.308) (BP4, BP7). To our knowledge, this variant has not been reported among individuals with GAMT deficiency and results of functional studies are unavailable. The GrpMax filtering allele frequency in gnomAD v4.1.0 is 0.0002424 in the African / African American population. This is lower than the ClinGen CCDS VCEP's threshold for PM2_Supporting (<0.0004), meeting this criterion (PM2_Supporting). There is a ClinVar entry for this variant (Variation ID: 288963). In summary, this variant meets the criteria to be classified as a variant of uncertain significance for GAMT deficiency based on the ACMG/AMP criteria applied, as specified by the ClinGen Cerebral Creatine Deficiency Syndromes Variant Curation Expert Panel (Specifications Version 2.0.0): PM2_Supporting, BP4, BP7.(Classification approved by the ClinGen Cerebral Creatine Deficiency Syndromes Variant Curation Expert Panel on October 8th, 2024). LINK:https://erepo.genome.network/evrepo/ui/classification/CA9043767/MONDO:0012999/026

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000022 (0 hom.)
• Consequence: GAMT ENST00000252288.8 synonymous
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:2 B:4
• Conservation: PhyloP100: -1.24

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]

ACMG classification

Verdict is Uncertain_significance. Variant got -1 ACMG points.

• PM2: For more information check the summary or visit ClinGen Evidence Repository.
• BP4: For more information check the summary or visit ClinGen Evidence Repository.
• BP7: For more information check the summary or visit ClinGen Evidence Repository.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GAMT	NM_000156.6	c.189G>C	p.Arg63=	synonymous_variant	2/6	ENST00000252288.8	NP_000147.1
GAMT	NM_138924.3	c.189G>C	p.Arg63=	synonymous_variant	2/5		NP_620279.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GAMT	ENST00000252288.8	c.189G>C	p.Arg63=	synonymous_variant	2/6	1	NM_000156.6	ENSP00000252288	P1
GAMT	ENST00000447102.8	c.189G>C	p.Arg63=	synonymous_variant	2/5	2		ENSP00000403536
GAMT	ENST00000640762.1	c.120G>C	p.Arg40=	synonymous_variant	2/6	5		ENSP00000492031

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152232 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000482

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: 0.00

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000213 AC: 5 AN: 235050 Hom.: 0 AF XY: 0.0000235 AC XY: 3 AN XY: 127884

Gnomad AFR exome AF: 0.0000687

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000691

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000945

Gnomad OTH exome AF: 0.000174

GnomAD4 exome AF: 0.0000220 AC: 32 AN: 1454706 Hom.: 0 Cov.: 33 AF XY: 0.0000304 AC XY: 22 AN XY: 723122

Gnomad4 AFR exome AF: 0.000718

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000235

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000499

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152350 Hom.: 0 Cov.: 32 AF XY: 0.0000134 AC XY: 1 AN XY: 74510

Gnomad4 AFR AF: 0.0000481

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: 0.00

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000508 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:2 Benign:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:1 Benign:1

Likely benign, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Jul 01, 2024	GAMT: BP4, BP7 -
Uncertain significance, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jul 15, 2016	- -

Deficiency of guanidinoacetate methyltransferase Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 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. -

not specified Benign:1

Likely benign, criteria provided, single submitter

clinical testing

GeneDx

Dec 27, 2017

This variant is considered likely benign or benign based on one or more of the following criteria: it is a conservative change, it occurs at a poorly conserved position in the protein, it is predicted to be benign by multiple in silico algorithms, and/or has population frequency not consistent with disease. -

Inborn genetic diseases Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 23, 2016

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -

Cerebral creatine deficiency syndrome Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 11, 2024

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.56
CADD	Benign	4.6
DANN	Benign	0.77
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		3.1

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: rs568392459; hg19: chr19-1399930;