1-99916703-CT-C

Position:

• chr1-99916703-CT-C

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The NM_000642.3(AGL):​c.4456del​(p.Ser1486ProfsTer18) variant causes a frameshift change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,100 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: AGL NM_000642.3 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:11 O:1
• Conservation: PhyloP100: 7.67

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]

LOC124904230 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most 50 bp of the penultimate exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.0315 CDS is truncated, and there are 0 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 1-99916703-CT-C is Pathogenic according to our data. Variant chr1-99916703-CT-C is described in ClinVar as [Pathogenic]. Clinvar id is 1098.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
AGL	NM_000642.3	c.4456del	p.Ser1486ProfsTer18	frameshift_variant	33/34	ENST00000361915.8	NP_000633.2
LOC124904230	XR_007066249.1	n.1146-3487del		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
AGL	ENST00000361915.8	c.4456del	p.Ser1486ProfsTer18	frameshift_variant	33/34	1	NM_000642.3	ENSP00000355106	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000797 AC: 2 AN: 250878 Hom.: 0 AF XY: 0.00000737 AC XY: 1 AN XY: 135600

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: 0.0000176

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461100 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 726868

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: 0.00

Gnomad4 OTH exome AF: 0.0000331

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:11 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Glycogen storage disease type III Pathogenic:6 Other:1

Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Sep 26, 2023	This sequence change creates a premature translational stop signal (p.Ser1486Profs*18) in the AGL gene. While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 47 amino acid(s) of the AGL protein. This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individuals with glycogen storage disease III (PMID: 9412782, 25388549, 25602008, 27065010, 27460348). This variant is also known as c.4455delT. ClinVar contains an entry for this variant (Variation ID: 1098). For these reasons, this variant has been classified as Pathogenic. -
not provided, no classification provided	literature only	GeneReviews	-	Founder variant in North African Jewish persons and those of Inuit descent -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Jun 20, 2023	- -
Pathogenic, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Dec 20, 2019	NM_000642.2(AGL):c.4456delT(S1486Pfs*18) is classified as pathogenic in the context of glycogen storage disease type III. Sources cited for classification include the following: PMID 9412782 and 25602008. Classification of NM_000642.2(AGL):c.4456delT(S1486Pfs*18) is based on the following criteria: The variant causes a premature termination codon that is not expected to be targeted by nonsense-mediated mRNA decay; however, literature evidence strongly supports pathogenicity. Please note: this variant was assessed in the context of healthy population screening. -
Pathogenic, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Jul 15, 2021	- -
Pathogenic, criteria provided, single submitter	clinical testing	3billion	Sep 01, 2022	The variant is observed at an extremely low frequency in the gnomAD v2.1.1 dataset (total allele frequency: <0.001%). Frameshift variant is predicted to result in a loss or disruption of normal protein function through protein truncation. The predicted truncated protein may be shortened by less than 10%. The variant has been observed in at least two similarly affected unrelated individuals (PMID: 9412782 / 3billion dataset). The variant has been reported to be in trans with a pathogenic variant as either compound heterozygous or homozygous in at least one similarly affected unrelated individual (PMID: 25388549 , 9412782 / 3billion dataset). The variant has been reported at least twice as pathogenic with clinical assertions and evidence for the classification (ClinVar ID: VCV000001098 / PMID: 9412782). Therefore, this variant is classified as Pathogenic according to the recommendation of ACMG/AMP guideline. -

not provided Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Nov 25, 2020	Frameshift variant in the C-terminus predicted to result in protein truncation, as the last 47 amino acids are lost and replaced with 17 incorrect amino acids (Stenson et al., 2014);; Not observed at a significant frequency in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 31661040, 28888851, 25388549, 25602008, 27460348, 9412782) -
Pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jun 13, 2014	- -
Pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Nov 01, 2018	- -

Glycogen storage disease IIIa Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Sep 01, 1997

- -

AGL-related disorder Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Apr 22, 2024

The AGL c.4456delT variant is predicted to result in a frameshift and premature protein termination (p.Ser1486Profs*18). This variant was reported in the homozygous or compound heterozygous state in individuals with glycogen storage disease IIIa (Parvari et al. 1997. PubMed ID: 9412782; Rousseau-Nepton et al. 2015. PubMed ID: 25602008; Decostre et al. 2017. PubMed ID: 28888851; Laforêt et al. 2019. PubMed ID: 31661040; Wen et al. 2022. PubMed ID: 35199448) and as a suspected founder variant in the Inuit population (Rousseau-Nepton et al. 2015. PubMed ID: 25602008). This variant is reported in 0.0018% of alleles in individuals of European (Non-Finnish) descent in gnomAD. Frameshift variants in AGL are expected to be pathogenic. This variant is interpreted as pathogenic. -

Computational scores

Source: dbNSFP v4.3

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: rs113994134; hg19: chr1-100382259;