rs1553193463

Positions:

• chr1-99916498-G-A
• chr1-99916498-G-C
• chr1-99916498-G-T

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PVS1_Moderate PM2 PP5_Moderate

The NM_000642.3(AGL):​c.4347+1G>A variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,457,242 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. 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 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: 9.41

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 (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.018917156 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.9, offset of 48, new splice context is: caaGTaatt. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 1-99916498-G-A is Pathogenic according to our data. Variant chr1-99916498-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 456505.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
AGL	NM_000642.3	c.4347+1G>A		splice_donor_variant, intron_variant		ENST00000361915.8	NP_000633.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
AGL	ENST00000361915.8	c.4347+1G>A		splice_donor_variant, intron_variant		1	NM_000642.3	ENSP00000355106.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1457242 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 725146

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000253

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.02e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

Submissions by phenotype

Glycogen storage disease type III Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Feb 22, 2023	Disruption of this splice site has been observed in individual(s) with glycogen storage disease (PMID: 26984562; Invitae). ClinVar contains an entry for this variant (Variation ID: 456505). Studies have shown that disruption of this splice site results in skipping of exon 33 and introduces a new termination codon (PMID: 26984562). However the mRNA is not expected to undergo nonsense-mediated decay. For these reasons, this variant has been classified as Pathogenic. This sequence change affects a donor splice site in intron 32 of the AGL gene. RNA analysis indicates that disruption of this splice site induces altered splicing and likely disrupts the C-terminus of the protein. This variant is not present in population databases (gnomAD no frequency). -
Likely pathogenic, no assertion criteria provided	clinical testing	Counsyl	Jul 12, 2019	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.41
CADD	Pathogenic	33
DANN	Uncertain	1.0
Eigen	Pathogenic	1.3
Eigen_PC	Pathogenic	1.2
FATHMM_MKL	Pathogenic	0.99	D
GERP RS		5.9

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.98		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.98		Position offset: -1

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

Publications

LitVar

Other links and lift over

dbSNP: rs1553193463; hg19: chr1-100382054;