NM_000156.6:c.623G>A

Variant names:

Variant summary

Our verdict is Uncertain significance. The variant received 1 ACMG points: 2P and 1B. PM5_SupportingPM2_SupportingBP4

This summary comes from the ClinGen Evidence Repository: The NM_000156.6:c.623G>A variant in GAMT is a missense variant predicted to cause substitution of arginine by histidine at amino acid 208 (p.Arg208His). The highest population minor allele frequency in gnomAD v4.1.0. is 0.0001114 (5/44894 alleles) in the East Asian population. This is lower that the ClinGen CCDS VCEP's threshold for PM2_Supporting (<0.0004), therefore meeting this criterion (PM2_Supporting). The computational predictor REVEL gives a score of 0.279 which is below the threshold of 0.29, evidence that correlates with no impact to GAMT function (BP4). In addition, SpliceAI predicts that the variant will have no impact on splicing. Two additional missense variants at this amino acid position have been reported - c.622C>T (p.Arg208Cys) (ClinVarID: 5442618) and c.623G>C (p.Arg208Pro) (PMID 24415674). The ClinGen CCDS VCEP has classified p.Arg208Pro as likely pathogenic, while p.Arg208Cys has been classified as a VUS (PM5_Supporting). To our knowledge, c.623G>A (p.Arg208His) has not been previously reported in the published literature, but has been noted in ClinVar (ClinVar ID 577478). In summary, this variant meets the criteria to be classified as a variant of uncertain significance for GAMT deficiency. GAMT-specific ACMG/AMP criteria applied, as specified by the ClinGen CCDS VCEP (Specifications Version 2.0.0.: PM2_Supporting, PM5_Supporting, BP4.(Classification approved by the ClinGen CCDS VCEP on April 28, 2025). LINK:https://erepo.genome.network/evrepo/ui/classification/CA9043553/MONDO:0012999/026

Frequency

Genomes: 𝑓 0.000026 ( 0 hom., cov: 33)

Exomes 𝑓: 0.000026 ( 0 hom. )

Consequence

GAMT
NM_000156.6 missense

Scores

Clinical Significance

Uncertain significance reviewed by expert panel U:4

Conservation

PhyloP100: 0.126

Publications

0 publications found

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 Gene-Disease associations (from GenCC):

guanidinoacetate methyltransferase deficiency
Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, Orphanet, G2P, ClinGen, Labcorp Genetics (formerly Invitae)

GAMT links:

Genome browser will be placed here

ACMG classification

Specifications for GAMT are available in the ClinGen Criteria Specification Registry and recommended for reference when assigning criteria.

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 1 ACMG points.

PM2

For more information check the summary or visit ClinGen Evidence Repository.

PM5

For more information check the summary or visit ClinGen Evidence Repository.

BP4

For more information check the summary or visit ClinGen Evidence Repository.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000156.6. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GAMT	NM_000156.6	MANE Select	c.623G>A	p.Arg208His	missense	Exon 6 of 6	NP_000147.1	Q14353-1

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
GAMT	ENST00000252288.8	TSL:1 MANE Select	c.623G>A	p.Arg208His	missense	Exon 6 of 6	ENSP00000252288.1	Q14353-1
GAMT	ENST00000902474.1		c.893G>A	p.Arg298His	missense	Exon 6 of 6	ENSP00000572533.1
GAMT	ENST00000902472.1		c.626G>A	p.Arg209His	missense	Exon 6 of 6	ENSP00000572531.1

Frequencies

GnomAD3 genomes

AF:

0.0000263

AC:

AN:

152214

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000724

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

GnomAD2 exomes

AF:

0.0000364

AC:

AN:

247300

AF XY:

0.0000372

show subpopulations

Gnomad AFR exome

AF:

0.000125

Gnomad AMR exome

AF:

0.0000290

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.000109

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000355

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000261

AC:

AN:

1457948

Hom.:

Cov.:

AF XY:

0.0000289

AC XY:

AN XY:

725392

show subpopulations

African (AFR)

AF:

0.0000597

AC:

AN:

33476

American (AMR)

AF:

0.0000224

AC:

AN:

44710

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26122

East Asian (EAS)

AF:

0.000126

AC:

AN:

39694

South Asian (SAS)

AF:

0.0000348

AC:

AN:

86258

European-Finnish (FIN)

AF:

0.00

AC:

AN:

49676

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.0000234

AC:

AN:

1111888

Other (OTH)

AF:

0.0000166

AC:

AN:

60356

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.499

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.0000263

AC:

AN:

152214

Hom.:

Cov.:

AF XY:

0.0000269

AC XY:

AN XY:

74364

show subpopulations

African (AFR)

AF:

0.0000724

AC:

AN:

41454

American (AMR)

AF:

0.00

AC:

AN:

15284

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5200

South Asian (SAS)

AF:

0.00

AC:

AN:

4834

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10626

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.0000147

AC:

AN:

68026

Other (OTH)

AF:

0.00

AC:

AN:

2090

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.525

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.0000378

ExAC

AF:

0.0000412

AC:

EpiCase

AF:

0.00

EpiControl

AF:

0.0000593

ClinVar

ClinVar submissions

Significance:Uncertain significance

Revision:reviewed by expert panel

View on ClinVar

Pathogenic

VUS

Benign

Condition

Deficiency of guanidinoacetate methyltransferase (2)

Cerebral creatine deficiency syndrome (1)

Inborn genetic diseases (1)

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.065

BayesDel_addAF

Benign

-0.35

BayesDel_noAF

Benign

-0.50

CADD

Benign

0.24

(source)

DANN

Benign

0.97

DEOGEN2

Benign

0.38

Eigen

Benign

-1.5

Eigen_PC

Benign

-1.5

FATHMM_MKL

Benign

0.40

LIST_S2

Benign

0.50

M_CAP

Uncertain

0.24

MetaRNN

Benign

0.17

MetaSVM

Benign

-0.92

MutationAssessor

Benign

0.77

PhyloP100

0.13

PROVEAN

Benign

-1.5

REVEL

Benign

0.28

Sift

Benign

0.11

Sift4G

Uncertain

0.038

Polyphen

0.0030

Vest4

0.041

MutPred

0.34

Gain of sheet (P = 0.0477)

MVP

0.49

ClinPred

0.020

GERP RS

-5.0

Varity_R

0.11

Mutation Taster

=69/31

polymorphism

(source)

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

You must be logged in to view publications. This limit was set because tens of millions (!) of queries from AI bots are generated daily.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over