1-99884704-G-T

Variant names:

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PVS1_ModeratePM2PP5_Very_Strong

The NM_000642.3(AGL):c.2681+1G>T variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000248 in 1,613,588 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 Likely pathogenic (★★).

Frequency

Genomes: 𝑓 0.000013 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000014 ( 0 hom. )

Consequence

AGL
NM_000642.3 splice_donor, intron

Scores

Splicing: ADA: 1.000

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:7

Conservation

PhyloP100: 8.56

Publications

5 publications found

Variant links:

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

AGL links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 12 ACMG points.

PVS1

Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.029354207 fraction of the gene. Cryptic splice site detected, with MaxEntScore 8.1, offset of 41, new splice context is: taaGTaagt. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.

PM2

Very rare variant in population databases, with high coverage;

PP5

Variant 1-99884704-G-T is Pathogenic according to our data. Variant chr1-99884704-G-T is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 371344.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 link	c.2681+1G>T		splice_donor_variant, intron_variant	Intron 20 of 33	ENST00000361915.8	NP_000633.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
AGL	ENST00000361915.8 link	c.2681+1G>T		splice_donor_variant, intron_variant	Intron 20 of 33	1	NM_000642.3	ENSP00000355106.3

Frequencies

GnomAD3 genomes

AF:

0.0000131

AC:

AN:

152112

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.000131

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

GnomAD2 exomes

AF:

0.00000797

AC:

AN:

250950

AF XY:

0.0000147

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.0000579

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000137

AC:

AN:

1461476

Hom.:

Cov.:

AF XY:

0.00000275

AC XY:

AN XY:

727036

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33460

American (AMR)

AF:

0.0000448

AC:

AN:

44684

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26122

East Asian (EAS)

AF:

0.00

AC:

AN:

39668

South Asian (SAS)

AF:

0.00

AC:

AN:

86252

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53328

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5766

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

1111816

Other (OTH)

AF:

0.00

AC:

AN:

60380

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.475

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

AF:

0.0000131

AC:

AN:

152112

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74282

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

41412

American (AMR)

AF:

0.000131

AC:

AN:

15268

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3468

East Asian (EAS)

AF:

0.00

AC:

AN:

5198

South Asian (SAS)

AF:

0.00

AC:

AN:

4830

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10586

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

68028

Other (OTH)

AF:

0.00

AC:

AN:

2094

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.500

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.0000340

ExAC

AF:

0.00000824

AC:

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:7

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Glycogen storage disease type III

Pathogenic:6

Jul 15, 2021

Genome-Nilou Lab

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Feb 08, 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.2681+1G>T is located in a canonical splice-site and is predicted to affect mRNA splicing resulting in a significantly altered protein due to either exon skipping, shortening, or inclusion of intronic material. Several computational tools predict a significant impact on normal splicing: Four predict the variant abolishes a 5' splicing donor site. However, these predictions have yet to be confirmed by functional studies. The variant allele was found at a frequency of 8e-06 in 250950 control chromosomes. c.2681+1G>T has been reported in the literature in the homozygous state in siblings affected with Glycogen Storage Disease Type III (Goldstein_2010, Hijazi_2021, Paschall_2021). 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. Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. All laboratories classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic.

Jun 15, 2020

Centre for Human Genetics

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

disease causing

Aug 31, 2016

Counsyl

Significance: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.

Sep 07, 2023

Baylor Genetics

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Oct 10, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change affects a donor splice site in intron 20 of the AGL gene. RNA analysis indicates that disruption of this splice site induces altered splicing and likely results in a shortened protein product. This variant is present in population databases (rs201201443, gnomAD 0.006%). Disruption of this splice site has been observed in individual(s) with glycogen storage disease type III (PMID: 10472540, 31028654). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 371344). Studies have shown that disruption of this splice site results in skipping of exon 21, but is expected to preserve the integrity of the reading-frame (PMID: 10472540, 31028654). For these reasons, this variant has been classified as Pathogenic.

Inborn genetic diseases

Pathogenic:1

Jan 24, 2024

Ambry Genetics

Significance:Likely pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The c.2681+1G>T intronic variant results from a G to T substitution one nucleotide after exon 20 (coding exon 19) of the AGL gene. Alterations that disrupt the canonical splice site are expected to result in aberrant splicing. The resulting transcript is predicted to be in-frame and is not expected to trigger nonsense-mediated mRNAdecay; however, direct evidence is unavailable. The exact functional effect of the altered amino acid sequence is unknown. Based on data from gnomAD, the T allele has an overall frequency of 0.001% (2/250950) total alleles studied. The highest observed frequency was 0.006% (2/34522) of Latino alleles. This mutation was identified in the homozygous state in several individuals with diagnosis of glycogen storage disease III (Hijazi, 2021; Kumar, 2022). In silico splice site analysis predicts that this alteration will weaken the native splice donor site and may result in the creation or strengthening of a novel splice donor site. Based on the available evidence, this alteration is classified as likely pathogenic.

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.50

BayesDel_noAF

Pathogenic

0.20

CADD

Pathogenic

(source)

DANN

Uncertain

0.99

DEOGEN2

Benign

0.0

.;.;.;.;.

Eigen

Pathogenic

1.1

Eigen_PC

Pathogenic

0.93

FATHMM_MKL

Pathogenic

1.0

LIST_S2

Benign

0.0

.;.;.;.;.

MetaRNN

Benign

0.0

.;.;.;.;.

MutationAssessor

Benign

0.0

.;.;.;.;.

PhyloP100

8.6

PROVEAN

Benign

0.0

.;.;.;.;.

REVEL

Benign

0.0

Sift

Pathogenic

0.0

.;.;.;.;.

Sift4G

Pathogenic

0.0

.;.;.;.;.

Vest4

0.0

GERP RS

4.7

Mutation Taster

=0/100

disease causing (ClinVar)

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

1.0

dbscSNV1_RF

Pathogenic

0.93

SpliceAI score (max)

0.98

Details are displayed if max score is > 0.2

DS_DG_spliceai

0.34

Position offset: 40

DS_DL_spliceai

0.98

Position offset: -1

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over