rs1055945806

chr17-80104552-C-Achr17-80104552-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 10P and 1B. PM2 PP5_Very_Strong BP4

The NM_000152.5(GAA):c.-32-3C>A variant causes a splice region, splice polypyrimidine tract, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000559 in 1,430,012 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Pathogenic (★★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000056 (0 hom.)
• Consequence: GAA NM_000152.5 splice_region, splice_polypyrimidine_tract, intron
• Scores: Splicing: ADA: 0.4710
• Clinical Significance: Pathogenic reviewed by expert panel P:4
• Conservation: PhyloP100: 0.341

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 Likely_pathogenic. Variant got 9 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 17-80104552-C-A is Pathogenic according to our data. Variant chr17-80104552-C-A is described in ClinVar as [Pathogenic]. Clinvar id is 371622.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr17-80104552-C-A is described in Lovd as [Pathogenic]. Variant chr17-80104552-C-A is described in Lovd as [Pathogenic].
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.73).. Strength limited to SUPPORTING due to the PP5.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAA	NM_000152.5	c.-32-3C>A		splice_region_variant, splice_polypyrimidine_tract_variant, intron_variant		ENST00000302262.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAA	ENST00000302262.8	c.-32-3C>A		splice_region_variant, splice_polypyrimidine_tract_variant, intron_variant		1	NM_000152.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000559 AC: 8 AN: 1430012 Hom.: 0 Cov.: 30 AF XY: 0.00000424 AC XY: 3 AN XY: 707696

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000731

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000756

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: reviewed by expert panel

Submissions by phenotype

Glycogen storage disease, type II Pathogenic:4

Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Nov 02, 2016	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Mar 09, 2023	For these reasons, this variant has been classified as Pathogenic. Studies have shown that this variant results in skipping of exon 2, and is expected to result in the loss of the initiator methionine (PMID: 18429042). ClinVar contains an entry for this variant (Variation ID: 371622). This variant has been observed in individuals with glycogen storage disease type II (PMID: 18429042, 19588081, 20464284). It has also been observed to segregate with disease in related individuals. This variant is not present in population databases (gnomAD no frequency). This sequence change falls in intron 1 of the GAA gene. It does not directly change the encoded amino acid sequence of the GAA protein. RNA analysis indicates that this variant induces altered splicing and is likely to result in the loss of the initiator methionine. -
Pathogenic, reviewed by expert panel	curation	ClinGen Lysosomal Storage Disorder Variant Curation Expert Panel	Nov 21, 2023	The NM_000152.5:c.-32-3C>A variant is located in the splice acceptor region of intron 1 and has been shown to impact splicing. In fibroblasts from an individual with Pompe disease who was compound heterozygous for the variant and a missense variant in GAA, RT-PCR revealed loss of exon 2 (p.M1_T182del, which includes the 27 residues of signal sequence, the 42 residues of the propeptide and the first 113 amino acids of the mature protein (from 70 to 182) (PMID: 18429042). A later study, in which the variant was expressed in a minigene, showed that the variant results in about 20% of transcripts with normal splicing of exon 2 (of note, this is a slightly lower level of normal splicing than observed for a well known pathogenic variant in the same splice region, c.-32-13T>G). Abnormal splicing events included complete loss of exon 2 (r.-32_546del) and activation of a cryptic splice site (r.‐32_486del) (PMID: 31301153). Due to loss of a critical region (the signal sequence) in aberrantly spliced transcripts, but with presence of some normal transcript (albeit at a lower level than a known pathogenic variant in the same splice region), PVS1 was applied at the strong level (PMID: 37352859) (PVS1_Strong, PS1_Supporting applied based on recommendations in PMID: 37352859). This variant has been reported in at least 6 probands with late onset Pompe disease including two individuals with documented GAA activity <30% normal in fibroblasts (PMID: 19046416, 21550241) (PP4_Moderate). Two of these probands have been reported to have this variant in compound heterozygosity, phase unknown, with another variant in GAA that has been classified as pathogenic by the ClinGen LD VCEP including c.1655T>C (p.Leu552Pro) (PMID: 18429042) and c.482_483del (PMID: 21550241). In addition, three affected siblings have been reported to be homozygous for the variant (PMID: 19588081, 20464284, 25681614) (PM3). Another three patients are compound heterozygous for the variant and a missense variant (either c.1905C>A (p.Asn635Lys), c.1447G>A (p.Gly483Arg), or c.2173C>T (p.Arg725Trp)) (PMID: 19588081). The allelic data from these patients will be used in the classification of the second variant and is not included here to avoid circular logic. The highest population minor allele frequency in gnomAD v4.0. is 0.000007314 (8/1093866 alleles) in the European non-Finnish populationn, which is lower than the ClinGen Lysosomal Diseases VCEP’s threshold for PM2_Supporting (<0.001), meeting this criterion (PM2_Supporting). There is a ClinVar entry for this variant (Variation ID: 371662). In summary, this variant meets the criteria to be classified as pathogenic for Pompe disease. GAA-specific ACMG/AMP criteria applied, as specified by the ClinGen LSD VCEP (Specifications Version 2.0): PVS1_Strong, PM3, PS1_Supporting, PP4_Moderate, PM2_Supporting. (Classification approved by the ClinGen Lysosomal Diseases Variant Curation Expert Panel on November 21, 2023). -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Mar 09, 2022	Variant summary: Several computational tools predict a significant impact on normal splicing: Four predict the variant weakens a canonical 3' acceptor site. Goina_2019 have shown c.-32-3C>A and -32-3C>G results in exon 2 skipping. The variant was absent in 233126 control chromosomes (gnomAD). c.-32-3C>A has been reported in multiple individuals homozygous and compound heterozygous affected with Glycogen Storage Disease, Type 2 (Pompe Disease) and this variant was segregated with disease in at least one family (examples: Oba-Shinjo_2009 and Grzesiuk_2010). The variant also segregated with the disease. These data indicate that the variant is very likely to be associated with disease. Two clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 and classified the variant as pathogenic (n=1) and likely pathogenic (n=1). Based on the evidence outlined above, the variant was classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.73
Cadd	Benign	15
Dann	Benign	0.77

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.47
dbscSNV1_RF	Benign	0.50
SpliceAI score (max)		0.19		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs1055945806; hg19: chr17-78078351;