1-99900717-C-A

Position:

• chr1-99900717-C-A

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000642.3(AGL):​c.3444C>A​(p.Tyr1148Ter) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000041 in 1,461,866 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. Y1148Y) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000041 (0 hom.)
• Consequence: AGL NM_000642.3 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 2.01

Genes affected

AGL (HGNC:321): (amylo-alpha-1, 6-glucosidase, 4-alpha-glucanotransferase) This gene encodes the glycogen debrancher enzyme which is involved in glycogen degradation. This enzyme has two independent catalytic activities which occur at different sites on the protein: a 4-alpha-glucotransferase activity and a amylo-1,6-glucosidase activity. Mutations in this gene are associated with glycogen storage disease although a wide range of enzymatic and clinical variability occurs which may be due to tissue-specific alternative splicing. Alternatively spliced transcripts encoding different isoforms have been described. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 1-99900717-C-A is Pathogenic according to our data. Variant chr1-99900717-C-A is described in ClinVar as [Pathogenic]. Clinvar id is 655389.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
AGL	NM_000642.3	c.3444C>A	p.Tyr1148Ter	stop_gained	26/34	ENST00000361915.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
AGL	ENST00000361915.8	c.3444C>A	p.Tyr1148Ter	stop_gained	26/34	1	NM_000642.3	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251490 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135920

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: 0.00000879

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000410 AC: 6 AN: 1461866 Hom.: 0 Cov.: 32 AF XY: 0.00000413 AC XY: 3 AN XY: 727226

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: 0.00000540

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ExAC AF: 0.00000824 AC: 1

EpiCase AF: 0.0000545

EpiControl AF: 0.00

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Glycogen storage disease type III Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Dec 30, 2021	Variant summary: AGL c.3444C>A (p.Tyr1148X) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. The variant allele was found at a frequency of 4e-06 in 251490 control chromosomes (gnomAD). c.3444C>A has been reported in the literature in homozygous and compound heterozygous individuals affected with Glycogen Storage Disease Type III (Mili_2012, Vega_2016). These data indicate that the variant is likely to be associated with disease. One of these publications reported leukocyte enzyme activities in two homozygous patients, and demonstrated lack of activity (Mili 2012). One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014, classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Nov 24, 2023	This sequence change creates a premature translational stop signal (p.Tyr1148*) in the AGL gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in AGL are known to be pathogenic (PMID: 19299494). This variant is present in population databases (rs776977863, gnomAD 0.0009%). This premature translational stop signal has been observed in individual(s) with glycogen storage disease (PMID: 22089644). ClinVar contains an entry for this variant (Variation ID: 655389). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Apr 11, 2023	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	37
DANN	Uncertain	1.0
Eigen	Uncertain	0.68
Eigen_PC	Uncertain	0.54
FATHMM_MKL	Uncertain	0.93	D
MutationTaster	Benign	1.0	A;A;A;A;A;A;A
Vest4		0.93
GERP RS		3.5

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: rs776977863; hg19: chr1-100366273;