rs1555777015

Variant names:

• chr19-1398956-A-C
• rs1555777015
• NM_000156.6:c.530T>G

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PM1 PM2 PP3

The NM_000156.6(GAMT):​c.530T>G​(p.Leu177Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic 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. L177V) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: GAMT NM_000156.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.85
• Publications: 0 publications found

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: Orphanet, G2P, Labcorp Genetics (formerly Invitae), ClinGen, Ambry Genetics

ACMG classification

Our verdict: Uncertain_significance. The variant received 5 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 17 uncertain in NM_000156.6
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.804

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

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GAMT	NM_000156.6	MANE Select	c.530T>G	p.Leu177Arg	missense	Exon 5 of 6	NP_000147.1
	GAMT	NM_138924.3		c.530T>G	p.Leu177Arg	missense	Exon 5 of 5	NP_620279.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	GAMT	ENST00000252288.8	TSL:1 MANE Select	c.530T>G	p.Leu177Arg	missense	Exon 5 of 6	ENSP00000252288.1
	GAMT	ENST00000447102.8	TSL:2	c.530T>G	p.Leu177Arg	missense	Exon 5 of 5	ENSP00000403536.2
	GAMT	ENST00000640762.1	TSL:5	c.461T>G	p.Leu154Arg	missense	Exon 5 of 6	ENSP00000492031.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

ClinVar submissions as Germline

Significance: Uncertain significance

Revision: criteria provided, single submitter

Pathogenic	VUS	Benign	Condition
-	1	-	Cerebral creatine deficiency syndrome (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.16
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.10
CADD	Pathogenic	28
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.66	D
Eigen	Uncertain	0.49
Eigen_PC	Uncertain	0.42
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.88	D
M_CAP	Pathogenic	0.66	D
MetaRNN	Pathogenic	0.80	D
MetaSVM	Uncertain	0.37	D
MutationAssessor	Pathogenic	3.0	M
PhyloP100		8.8
PrimateAI	Uncertain	0.67	T
PROVEAN	Uncertain	-2.9	D
REVEL	Pathogenic	0.70
Sift	Uncertain	0.0050	D
Sift4G	Benign	0.30	T
Polyphen		0.93	P
Vest4		0.85
MutPred		0.52		Gain of disorder (P = 0.0216)
MVP		0.99
MPC		0.76
ClinPred		0.99	D
GERP RS		2.9
Varity_R		0.63
gMVP		0.91
Mutation Taster		=26/74	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs1555777015; hg19: chr19-1398955;