chr17-80110841-G-T

Position:

• chr17-80110841-G-T

Variant summary

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

The NM_000152.5(GAA):​c.1551+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 0.0000103 in 1,461,748 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: not found (cov: 33)
  • Exomes 𝑓: 0.000010 (0 hom.)
• Consequence: GAA NM_000152.5 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:7
• Conservation: PhyloP100: 9.39

Genes affected

GAA (HGNC:4065): (alpha glucosidase) This gene encodes lysosomal alpha-glucosidase, which is essential for the degradation of glycogen to glucose in lysosomes. The encoded preproprotein is proteolytically processed to generate multiple intermediate forms and the mature form of the enzyme. Defects in this gene are the cause of glycogen storage disease II, also known as Pompe's disease, which is an autosomal recessive disorder with a broad clinical spectrum. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2016]

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.03952431 fraction of the gene. Cryptic splice site detected, with MaxEntScore 5.8, offset of -24, new splice context is: cagGTgccc. Cryptic site results in inframe 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 17-80110841-G-T is Pathogenic according to our data. Variant chr17-80110841-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 555986.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr17-80110841-G-T is described in Lovd as [Pathogenic]. Variant chr17-80110841-G-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GAA	NM_000152.5	c.1551+1G>T		splice_donor_variant, intron_variant		ENST00000302262.8	NP_000143.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GAA	ENST00000302262.8	c.1551+1G>T		splice_donor_variant, intron_variant		1	NM_000152.5	ENSP00000305692.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000796 AC: 2 AN: 251156 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135858

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

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: 0.00000881

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000103 AC: 15 AN: 1461748 Hom.: 0 Cov.: 37 AF XY: 0.00000963 AC XY: 7 AN XY: 727180

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000252

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000117

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:7

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Glycogen storage disease, type II Pathogenic:7

Pathogenic, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Nov 03, 2022	The c.1551+1G>T variant in GAA has been reported in at least five individuals with glycogen storage disease II (3 in the compound heterozygous state) and segregated with disease in 1 family member (Gesquière-Dando 2015 PMID: 25703594, Bali 2012 PMID: 22252923, Bergsma 2015 PMID: 25243733, Kishnani 2019 PMID: 31086307). It has been reported in ClinVar (Variation ID 555986) and was absent from large population databases. This variant occurs in the invariant region (+/- 1/2) of the splice consensus sequence, and in vitro functional studies suggest it causes in-frame exon 10 skipping and a leaky wild-type splice site leading to an abnormal or absent protein (Gesquière-Dando 2015 PMID: 25703594, Bergsma 2015 PMID: 25243733). Loss of function of the GAA gene is an established disease mechanism in autosomal recessive glycogen storage disease II. In summary, this variant meets criteria to be classified as pathogenic for autosomal recessive glycogen storage disease II. ACMG/AMP Criteria applied: PM3_Strong, PM2_Supporting, PS3_Moderate, PM4. -
Pathogenic, criteria provided, single submitter	clinical testing	Institute of Medical Genetics and Genomics, Sir Ganga Ram Hospital	Jun 22, 2023	The homozygous splice site variant c.1551+1G>T has been identified in the proband with phenotypes: respiratory distress, muscle weakness, proximal and distal muscles weakness in lower and upper extremities. This variant has been identified in a proband in a compound heterozygous state with c.1861T>C (p.Trp621Arg) presented with symptoms at 7 months with cardiomegaly, respiratory distress, muscle weakness. -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Apr 01, 2022	This sequence change affects a donor splice site in intron 10 of the GAA 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 (rs770780848, gnomAD 0.003%). Disruption of this splice site has been observed in individual(s) with Pompe disease (PMID: 25243733, 31086307). ClinVar contains an entry for this variant (Variation ID: 555986). Studies have shown that disruption of this splice site results in skipping of exon 10, but is expected to preserve the integrity of the reading-frame (PMID: 25243733). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Jan 05, 2018	- -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Apr 08, 2021	Variant summary: GAA c.1551+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. Bergsma et al, 2014 report that the variant causes in-frame exon 10 skipping and a leaky wild-type splicing (Bergsma_2014). The variant allele was found at a frequency of 8e-06 in 251156 control chromosomes (gnomAD). c.1551+1G>T has been reported in the literature in multiple individuals (both homozygous and compound heterozygous patients) affected with Glycogen Storage Disease, Type 2 (Pompe Disease) (Bergsma_2014, Gupta_2020, Kishnani_2019, Semplicini_2018, Thomas_2021). Several of these patients had juvenile and infantile onset of the disease. These data indicate that the variant is very likely to be associated with disease. Patient homozygous for the variant show reduced alpha-glucosidase activity (Thomas_2021). Two ClinVar submitters (evaluation after 2014) cite the variant as pathogenic/likely pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -
Likely pathogenic, criteria provided, single submitter	curation	Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard	Jan 22, 2020	The c.1551+1G>T variant in GAA has been reported in five individuals with glycogen storage disease II, segregated with disease in two affected relatives from one family (PMID: 25703594) and has been identified in 0.003% (1/34580) of Latino chromosomes and 0.001% (1/113512) of European (non-Finnish) chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP rs770780848). Although this variant has been seen in the general population, its frequency is low enough to be consistent with a recessive carrier frequency. This variant has also been reported in ClinVar as pathogenic by Counsyl (VariationID: 555986). This variant occurs in the invariant region (+/- 1/2) of the splice consensus sequence and is predicted to cause in-frame exon skipping and a leaky splice site leading to an abnormal or absent protein. There is an in-frame cryptic splice site 6 bases from the intron-exon boundary, providing evidence that this variant may add 2 amino acids instead of causing loss of function. However, this information is not predictive enough to determine pathogenicity. Loss of function of the GAA gene is an established disease mechanism in autosomal recessive glycogen storage disease II. The phenotype of individuals that are compound heterozygous for this variant is highly specific for glycogen storage disease II based on GAA enzyme activity in fibroblasts being <10% of wild type, consistent with disease (PMID: 25703594, 25243733). Additionally, the presence of this variation in combination with reported pathogenic variant c.-32-13T>G (VariationID: 4027, PMID: 30155607, 25703594) and likely pathogenic variant p.Asp419Val (PMID: 25243733) and in individuals with glycogen storage disease II increases the likelihood that the c.1551+1G>T variant is pathogenic. In summary, although additional studies are required to fully establish its clinical significance, this variant is likely pathogenic. ACMG/AMP Criteria applied: PVS1_moderate, PM3, PM2, PP4 (Richards 2015). -
Pathogenic, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	Jul 23, 2021	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.27
CADD	Pathogenic	33
DANN	Uncertain	1.0
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.98
FATHMM_MKL	Pathogenic	0.99	D
GERP RS		5.4

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.22		Position offset: -25
DS_DL_spliceai		0.99		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: rs770780848; hg19: chr17-78084640;