17-80110725-A-G

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PVS1_Moderate PM2 PP3_Strong PP5_Very_Strong

The NM_000152.5(GAA):c.1438-2A>G variant causes a splice acceptor change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,322 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: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: GAA NM_000152.5 splice_acceptor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic reviewed by expert panel P:4
• Conservation: PhyloP100: 8.76

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 16 ACMG points.

• PVS1: Splicing variant, NOT destroyed by nmd, known LOF gene, truncates exone, which is 0.019762155 fraction of the gene. Cryptic splice site detected, with MaxEntScore 6.9, offset of -15, new splice context is: gccgggtctccccactgcAGcct. 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
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 17-80110725-A-G is Pathogenic according to our data. Variant chr17-80110725-A-G is described in ClinVar as [Pathogenic]. Clinvar id is 526521.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr17-80110725-A-G is described in Lovd as [Pathogenic]. Variant chr17-80110725-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAA	NM_000152.5	c.1438-2A>G		splice_acceptor_variant		ENST00000302262.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAA	ENST00000302262.8	c.1438-2A>G		splice_acceptor_variant		1	NM_000152.5	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461322 Hom.: 0 Cov.: 37 AF XY: 0.00000138 AC XY: 1 AN XY: 726988

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: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

Bravo AF: 0.00000378

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: reviewed by expert panel

Submissions by phenotype

Glycogen storage disease, type II Pathogenic:4

Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Aug 03, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Jun 01, 2023	For these reasons, this variant has been classified as Pathogenic. 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: 24158270). ClinVar contains an entry for this variant (Variation ID: 526521). Disruption of this splice site has been observed in individual(s) with late onset glycogen storage disease type II (PMID: 24158270). This variant is not present in population databases (gnomAD no frequency). This sequence change affects an acceptor splice site in intron 9 of the GAA gene. RNA analysis indicates that disruption of this splice site induces altered splicing and likely results in a shortened protein product. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Apr 21, 2017	- -
Pathogenic, reviewed by expert panel	curation	ClinGen Lysosomal Storage Disorder Variant Curation Expert Panel	Mar 30, 2020	The c.1438-2A>G variant alters the canonical acceptor splice site of intron 9 and has been shown by RT-PCR to causing skipping of exon 10, resulting in an in frame deletion that removes about 4% of the gene product (PMID 24158270). Exon 10 forms part of the GAA catalytic barrel, including two residues, Trp481 and Trp516, which are part of the GAA active site (PMIDs 1856189; 22253258; DOI 10.1101/212837). Therefore, loss of this exon is expected to abolish GAA activity, and PVS1 can be applied. The variant is absent in gnomAD v2.1.1, meeting PM2. This variant has been reported in two individuals with Pompe disease who meet the ClinGen LSD VCEP's specifications for PP4, and who are compound heterozygotes for this variant and a second pathogenic variant, c.-32-13T>G in one case (PMIDs 24158270), and c.955+1G>A in the other (PMID 29422078), meeting PM3. Other variants altering the same canonical splice site, c.1438-1G>T (PMID 18425781) and c.1438-1G>C (PMIDs 22538254, 24495340), have been reported in patients with Pompe disease. There is a ClinVar entry for this variant (Variation ID: 526521) with one submitters classifying the variant as pathogenic and one as likely pathogenic. In summary, this variant meets the criteria to be classified as Pathogenic for Pompe disease. GAA-specific ACMG/AMP criteria applied: PVS1, PM2, PM3, and PP4. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.15
Cadd	Pathogenic	32
Dann	Uncertain	0.99
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.88
FATHMM_MKL	Pathogenic	1.0	D
MutationTaster	Benign	1.0	D;D
GERP RS		5.3

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.92
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.47		Position offset: 48
DS_AL_spliceai		0.99		Position offset: 2

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

Publications

LitVar

Other links and lift over

dbSNP: rs1555600730; hg19: chr17-78084524;