chr1-99900826-AC-A

Variant names:

• chr1-99900826-AC-A
• rs764318570
• NM_000642.3:c.3554delC

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000642.3(AGL):​c.3554delC​(p.Thr1185LysfsTer42) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000558 in 1,613,674 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000055 (0 hom.)
• Consequence: AGL NM_000642.3 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 1.24
• Publications: 0 publications found

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]

AGL Gene-Disease associations (from GenCC):

• glycogen storage disease III

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, Ambry Genetics, Laboratory for Molecular Medicine, Myriad Women’s Health, Orphanet, G2P, PanelApp Australia, Labcorp Genetics (formerly Invitae), Genomics England PanelApp

ACMG classification

Our verdict: Pathogenic. The variant received 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 1-99900826-AC-A is Pathogenic according to our data. Variant chr1-99900826-AC-A is described in ClinVar as [Pathogenic]. Clinvar id is 370894.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
AGL	NM_000642.3	c.3554delC	p.Thr1185LysfsTer42	frameshift_variant	Exon 26 of 34	ENST00000361915.8	NP_000633.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
AGL	ENST00000361915.8	c.3554delC	p.Thr1185LysfsTer42	frameshift_variant	Exon 26 of 34	1	NM_000642.3	ENSP00000355106.3

Frequencies

GnomAD3 genomes AF: 0.00000658 AC: 1 AN: 152052 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

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: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000547 AC: 8 AN: 1461622 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727160

African (AFR) AF: 0.00 AC: 0 AN: 33474

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26134

East Asian (EAS) AF: 0.00 AC: 0 AN: 39690

South Asian (SAS) AF: 0.00 AC: 0 AN: 86248

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53418

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 0.00000720 AC: 8 AN: 1111778

Other (OTH) AF: 0.00 AC: 0 AN: 60392

GnomAD4 genome AF: 0.00000658 AC: 1 AN: 152052 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74274

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.0000241 AC: 1 AN: 41414

American (AMR) AF: 0.00 AC: 0 AN: 15266

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3470

East Asian (EAS) AF: 0.00 AC: 0 AN: 5184

South Asian (SAS) AF: 0.00 AC: 0 AN: 4822

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10576

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68006

Other (OTH) AF: 0.00 AC: 0 AN: 2086

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Glycogen storage disease type III Pathogenic:4

Apr 06, 2022

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: AGL c.3554delC (p.Thr1185LysfsX42) 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. Truncations downstream of this position have been classified as pathogenic by our laboratory. The variant was absent in 251464 control chromosomes (gnomAD). c.3554delC has been reported in the literature in individuals affected with Glycogen Storage Disease Type III (Goldstein_2010, Sentner_2016, Decostre_2016), including one verified occurrence in trans with a pathogenic nonsense variant (Decostre_2016). These data indicate that the variant is likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Three ClinVar submitters have assessed the variant since 2014: one classified the variant as likely pathogenic and two as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

May 11, 2016

Counsyl

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com. -

Jul 15, 2021

Genome-Nilou Lab

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Aug 21, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Thr1185Lysfs*42) 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 not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with AGL-related conditions (PMID: 20648714). ClinVar contains an entry for this variant (Variation ID: 370894). 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		1.2
Mutation Taster		=0/200	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.14		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: rs764318570; hg19: chr1-100366382;