rs1441030187

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM3_SupportingPP3PP4_StrongPM2_SupportingPS3

This summary comes from the ClinGen Evidence Repository: The NM_000156.6:c.224C>T variant in GAMT is a missense variant that is predicted to result in the substitution of alanine by valine at amino acid 75 (p.Ala75Val). One patient, with mild intellectual disability, anti-epileptic drug-responsive seizures, and stereotypic movements has been reported with creatine and guanidinoacetate peak absent on MRS, bilateral thalami increased on MRI, and urine guanidinoacetate levels between 1.1 and 12 times above the upper limit of reference range (PP4_Strong). This individual is homozygous for the variant (PM3_Supporting). The highest population minor allele frequency in gnomAD v2.1.1 is 0.00007 (1/15028 alleles) in the African population, which is lower than the ClinGen CCDS VCEP’s threshold for PM2_Supporting (<0.0004), meeting this criterion (PM2_Supporting). GAMT-deficient fibroblasts transfected with the variant showed <15% wild-type enzyme activity (PMID:24415674). The computational predictor REVEL gives a score of 0.86 which is above the threshold of 0.75, evidence that correlates with impact to GAMT function (PP3). There is a ClinVar entry for this variant (Variation ID: 544251). In summary, this variant meets the criteria to be classified as pathogenic 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 1.1.0): PP4_Strong, PP3, PS3_Supporting, PM2_Supporting, PM3_Supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA402996954/MONDO:0012999/026

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)
Exomes 𝑓: 0.000029 ( 0 hom. )

Consequence

GAMT
ENST00000252288.8 missense

Scores

7
11
1

Clinical Significance

Pathogenic reviewed by expert panel P:4U:2

Conservation

PhyloP100: 9.88
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]

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 11 ACMG points.

PS3
For more information check the summary or visit ClinGen Evidence Repository.
PM2
For more information check the summary or visit ClinGen Evidence Repository.
PM3
For more information check the summary or visit ClinGen Evidence Repository.
PP3
For more information check the summary or visit ClinGen Evidence Repository.
PP4
For more information check the summary or visit ClinGen Evidence Repository.

Transcripts

RefSeq

Gene Transcript HGVSc HGVSp Effect #exon/exons MANE Protein UniProt
GAMTNM_000156.6 linkuse as main transcriptc.224C>T p.Ala75Val missense_variant 2/6 ENST00000252288.8 NP_000147.1
GAMTNM_138924.3 linkuse as main transcriptc.224C>T p.Ala75Val missense_variant 2/5 NP_620279.1

Ensembl

Gene Transcript HGVSc HGVSp Effect #exon/exons TSL MANE Protein Appris UniProt
GAMTENST00000252288.8 linkuse as main transcriptc.224C>T p.Ala75Val missense_variant 2/61 NM_000156.6 ENSP00000252288 P1Q14353-1
GAMTENST00000447102.8 linkuse as main transcriptc.224C>T p.Ala75Val missense_variant 2/52 ENSP00000403536 Q14353-2
GAMTENST00000640762.1 linkuse as main transcriptc.155C>T p.Ala52Val missense_variant 2/65 ENSP00000492031

Frequencies

GnomAD3 genomes
AF:
0.00000657
AC:
1
AN:
152190
Hom.:
0
Cov.:
32
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:
0.0000209
AC:
5
AN:
239744
Hom.:
0
AF XY:
0.0000230
AC XY:
3
AN XY:
130240
show subpopulations
Gnomad AFR exome
AF:
0.0000665
Gnomad AMR exome
AF:
0.00
Gnomad ASJ exome
AF:
0.00
Gnomad EAS exome
AF:
0.00
Gnomad SAS exome
AF:
0.0000341
Gnomad FIN exome
AF:
0.00
Gnomad NFE exome
AF:
0.0000278
Gnomad OTH exome
AF:
0.00
GnomAD4 exome
AF:
0.0000288
AC:
42
AN:
1456236
Hom.:
0
Cov.:
33
AF XY:
0.0000318
AC XY:
23
AN XY:
723922
show subpopulations
Gnomad4 AFR exome
AF:
0.0000898
Gnomad4 AMR exome
AF:
0.00
Gnomad4 ASJ exome
AF:
0.00
Gnomad4 EAS exome
AF:
0.00
Gnomad4 SAS exome
AF:
0.0000704
Gnomad4 FIN exome
AF:
0.00
Gnomad4 NFE exome
AF:
0.0000288
Gnomad4 OTH exome
AF:
0.0000166
GnomAD4 genome
AF:
0.00000657
AC:
1
AN:
152190
Hom.:
0
Cov.:
32
AF XY:
0.00
AC XY:
0
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
Bravo
AF:
0.0000264

ClinVar

Significance: Pathogenic
Submissions summary: Pathogenic:4Uncertain:2
Revision: reviewed by expert panel
LINK: link

Submissions by phenotype

Deficiency of guanidinoacetate methyltransferase Pathogenic:3Uncertain:1
Pathogenic, reviewed by expert panelcurationClinGen Cerebral Creatine Deficiency Syndromes Variant Curation Expert Panel, ClinGenMar 09, 2023The NM_000156.6:c.224C>T variant in GAMT is a missense variant that is predicted to result in the substitution of alanine by valine at amino acid 75 (p.Ala75Val). One patient, with mild intellectual disability, anti-epileptic drug-responsive seizures, and stereotypic movements has been reported with creatine and guanidinoacetate peak absent on MRS, bilateral thalami increased on MRI, and urine guanidinoacetate levels between 1.1 and 12 times above the upper limit of reference range (PP4_Strong). This individual is homozygous for the variant (PM3_Supporting). The highest population minor allele frequency in gnomAD v2.1.1 is 0.00007 (1/15028 alleles) in the African population, which is lower than the ClinGen CCDS VCEP’s threshold for PM2_Supporting (<0.0004), meeting this criterion (PM2_Supporting). GAMT-deficient fibroblasts transfected with the variant showed <15% wild-type enzyme activity (PMID: 24415674). The computational predictor REVEL gives a score of 0.86 which is above the threshold of 0.75, evidence that correlates with impact to GAMT function (PP3). There is a ClinVar entry for this variant (Variation ID: 544251). In summary, this variant meets the criteria to be classified as pathogenic 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 1.1.0): PP4_Strong, PP3, PS3_Supporting, PM2_Supporting, PM3_Supporting. -
Likely pathogenic, criteria provided, single submitterclinical testingBaylor GeneticsMar 20, 2024- -
Likely pathogenic, criteria provided, single submitterclinical testingWomen's Health and Genetics/Laboratory Corporation of America, LabCorpSep 09, 2024Variant summary: GAMT c.224C>T (p.Ala75Val) results in a non-conservative amino acid change located in the Arginine N-methyltransferase 2-like domain (IPR026480) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 2.1e-05 in 239744 control chromosomes. c.224C>T has been reported in the literature in a homozygous individual affected with Guanidinoactetate Methyltransferase Deficiency (Mercimek-Mahmutoglu_2014) and was identified in as an unspecified genotype in an individual undergoing multigene panel testing for epilepsy and neurodevelopmental disorders, although no further clinical information was provided (Lindy_2018) . These data indicate that the variant may be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function. The variant exhibited <4% activity versus the WT protein when transfected into a GAMT-deficient human fibroblast cell line (Mercimek-Mahmutoglu_2014). The following publications have been ascertained in the context of this evaluation (PMID: 29655203, 24415674). ClinVar contains an entry for this variant (Variation ID: 544251). Based on the evidence outlined above, the variant was classified as likely pathogenic. -
Uncertain significance, no assertion criteria providedclinical testingNatera, Inc.Sep 18, 2020- -
Cerebral creatine deficiency syndrome Pathogenic:1Uncertain:1
Uncertain significance, criteria provided, single submitterclinical testingLabcorp Genetics (formerly Invitae), LabcorpJun 02, 2022This sequence change replaces alanine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 75 of the GAMT protein (p.Ala75Val). This variant is present in population databases (no rsID available, gnomAD 0.007%). This missense change has been observed in individual(s) with a positive newborn screening result for GAMT-related disease (PMID: 24415674). ClinVar contains an entry for this variant (Variation ID: 544251). 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: "Probably Damaging"; Align-GVGD: "Class C15"). Experimental studies have shown that this missense change affects GAMT function (PMID: 24415674). 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. -
Likely pathogenic, criteria provided, single submittercurationBroad Center for Mendelian Genomics, Broad Institute of MIT and HarvardNov 02, 2021The p.Ala75Val variant in GAMT has been reported in 1 homozygous individual with cerebral creatine deficiency syndrome (PMID: 24415674) and has been identified in 0.007% (1/15028) of African/African-American chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP ID: rs1441030187). Although this variant has been seen in the general population in a heterozygous state, its frequency is low enough to be consistent with a recessive carrier frequency. This variant has also been reported in ClinVar (Variation ID#: 544251) and has been interpreted as VUS by Invitae. In vitro functional studies provide some evidence that the p.Ala75Val variant may slightly impact protein function (PMID: 24415674). However, these types of assays may not accurately represent biological function. Computational prediction tools and conservation analyses suggest that this variant may impact the protein. The phenotype of individuals homozygous or compound heterozygous for this variant is highly specific for cerebral creatine deficiency syndrome based on strict biochemical investigations consistent with disease (PMID: 24415674). In summary, although additional studies are required to fully establish its clinical significance, this variant is likely pathogenic for autosomal recessive cerebral creatine deficiency syndrome. ACMG/AMP Criteria applied: PM3_supporting, PM2_supporting, PS3_supporting, PP3, PP4_strong (Richards 2015). -

Computational scores

Source: dbNSFP v4.3

Name
Calibrated prediction
Score
Prediction
AlphaMissense
Pathogenic
0.91
BayesDel_addAF
Uncertain
0.073
D
BayesDel_noAF
Uncertain
0.050
CADD
Pathogenic
28
DANN
Pathogenic
1.0
DEOGEN2
Uncertain
0.73
D;.;.
Eigen
Uncertain
0.57
Eigen_PC
Uncertain
0.45
FATHMM_MKL
Pathogenic
0.97
D
LIST_S2
Uncertain
0.93
D;D;D
M_CAP
Pathogenic
0.51
D
MetaRNN
Pathogenic
0.88
D;D;D
MetaSVM
Uncertain
0.65
D
MutationAssessor
Pathogenic
3.2
M;.;M
MutationTaster
Benign
1.0
D;D
PrimateAI
Uncertain
0.56
T
PROVEAN
Uncertain
-3.3
D;.;D
REVEL
Pathogenic
0.86
Sift
Uncertain
0.0030
D;.;T
Sift4G
Uncertain
0.029
D;.;D
Polyphen
1.0
D;.;.
Vest4
0.97
MutPred
0.50
Gain of catalytic residue at A75 (P = 0.0098);.;Gain of catalytic residue at A75 (P = 0.0098);
MVP
0.93
MPC
0.63
ClinPred
0.87
D
GERP RS
3.2
RBP_binding_hub_radar
0.0
RBP_regulation_power_radar
1.8
Varity_R
0.71
gMVP
0.87

Splicing

Name
Calibrated prediction
Score
Prediction
SpliceAI score (max)
0.050
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.

Other links and lift over

dbSNP: rs1441030187; hg19: chr19-1399895; COSMIC: COSV52040506; COSMIC: COSV52040506; API