17-80108467-T-G

Position:

• chr17-80108467-T-G

Variant summary

Our verdict is Pathogenic. Variant got 9 ACMG points: 9P and 0B. PP4_Moderate PM2_Supporting PM3 PVS1_Strong

This summary comes from the ClinGen Evidence Repository: The NM_000152.5:c.1076-22T>G variant in GAA occurs within intron 6. Experimental studies show that the variant causes skipping of biologically-relevant-exon 6 resulting in an in-frame deletion of amino acids 319-358 (PMIDs 9259196, 10737124). This includes part of the GAA catalytic barrel (amino acids 347-727) (Kroos et al, 2012, PMID 22253258; Deming et al, 2017; DOI 10.1101/212837) (PVS1_Strong). At least 7 probands have been reported with this variant, at least 5 of them with reported GAA activity <10% normal in lymphocytes, leukocytes or muscle samples, or <30% normal in cultured fibroblasts, or in the affected range in a clinically validated dried blood spot assay (PP4_Moderate). Of these individuals, 6 are compound heterozygous for the variant and another variant in GAA that has been classified as pathogenic or likely pathogenic by the ClinGen Lysosomal Diseases VCEP, including 2 confirmed in trans - c.2560C>T (p.Arg854Ter) (ClinVar Variation ID: 4034, SCV001371731.1) (PMID:9259196), c.1437+1G>A (ClinVar Variation ID: 555864, SCV004227900.1), and 4 with phase unknown - c.1942G>A (p.Gly648Ser) (ClinVar Variation ID: 188902, SCV001371752.2) (PMID:25455803), c.-32-13T>G (ClinVar Variation ID: 4027) (PMID:22613277), c.1841C>A (p.Thr614Lys) (ClinVar Variation ID: 167113, SCV001371751.1) (PMID:21484825), and c.525delT (ClinVar Variation ID: 4033, SCV001443331.1) (PMID:29181627). In addition, two siblings are homozygous for the variant (PMID:10737124) (PM3_VeryStrong). The highest population minor allele frequency in gnomAD v2.1.1 is 0.00002658 (3/112848 alleles) in the European non-Finnish population, 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: 370278). In summary, this variant meets the criteria to be classified as Pathogenic for Pompe disease based on the GAA-specific ACMG/AMP criteria applied, as specified by the ClinGen Lysosomal Diseases Variant Curation Expert Panel (Specifications Version 2.0): PVS1_Strong, PM3_Strong, PP4_Moderate, PM2_Supporting.(Classification approved by the ClinGen Lysosomal Diseases Variant Curation Expert Panel on February 6, 2024). LINK:https://erepo.genome.network/evrepo/ui/classification/CA8815157/MONDO:0009290/010

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000068 (0 hom.)
• Consequence: GAA NM_000152.5 intron
• Clinical Significance: Pathogenic reviewed by expert panel P:8
• Conservation: PhyloP100: -0.0590

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 9 ACMG points.

• PVS1: For more information check the summary or visit ClinGen Evidence Repository.
• PM2: For more information check the summary or visit ClinGen Evidence Repository.
• PM3: For more information check the summary or visit ClinGen Evidence Repository.
• PP4: For more information check the summary or visit ClinGen Evidence Repository.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GAA	NM_000152.5	c.1076-22T>G		intron_variant		ENST00000302262.8	NP_000143.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GAA	ENST00000302262.8	c.1076-22T>G		intron_variant		1	NM_000152.5	ENSP00000305692	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.0000160 AC: 4 AN: 250216 Hom.: 0 AF XY: 0.0000147 AC XY: 2 AN XY: 135680

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

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: 0.0000266

Gnomad OTH exome AF: 0.000164

GnomAD4 exome AF: 0.00000685 AC: 10 AN: 1460852 Hom.: 0 Cov.: 39 AF XY: 0.00000688 AC XY: 5 AN XY: 726756

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: 0.0000191

Gnomad4 NFE exome AF: 0.00000809

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:8

Revision: reviewed by expert panel

Submissions by phenotype

Glycogen storage disease, type II Pathogenic:6

Pathogenic, criteria provided, single submitter	curation	Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard	Jan 22, 2020	The c.1076-22T>G variant in GAA has been reported in 8 individuals (including 3 Germans, 2 Dutch, and 1 African American/Caucasian individuals) with Glycogen Storage Disorder II (PMID: 10737124, 9259196, 25455803, 22613277, 21484825, 22676651, 23013746), and has also been reported likely pathogenic by Counsyl in ClinVar (Variation ID: 370278). This variant has been identified in 0.003% (3/112848) of European (non-Finnish) chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP rs762260678). Although this variant has been seen in the general population, its frequency is low enough to be consistent with a recessive carrier frequency. In vitro functional studies with RNA extracted from individuals homozygous for this variant provide some evidence that the c.1076-22T>G variant may cause abnormal splicing (PMID: 10737124). However, these types of assays may not accurately represent biological function. Computational prediction tools and conservation analyses suggest that this variant may impact splicing, though this information is not predictive enough to determine pathogenicity. The presence of this variant in the homozygous state and in combination with pathogenic variants, and in individuals with Glycogen Storage Disorder II increases the likelihood that the c.1076-22T>G variant is pathogenic (PMID: 10737124, 22676651, 22613277, 9259196, 21484825). The phenotype of homozygous and heterozygous individuals with this variant is highly specific for Glycogen Storage Disease II based on reduced GAA activity detected in relevant tissues (PMID: 10737124, 22676651, 22613277, 9259196, 21484825). In summary, this variant meets criteria to be classified as pathogenic for Glycogen Storage Disorder II in an autosomal recessive manner based on in vitro functional studies and multiple occurrences with pathogenic variants. ACMG/AMP Criteria applied: PM3_Strong, PS3, PM2, PP3, PP4 (Richards 2015). -
Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Feb 17, 2024	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Jan 05, 2016	- -
Pathogenic, reviewed by expert panel	curation	ClinGen Lysosomal Storage Disorder Variant Curation Expert Panel	Feb 06, 2024	The NM_000152.5:c.1076-22T>G variant in GAA occurs within intron 6. Experimental studies show that the variant causes skipping of biologically-relevant-exon 6 resulting in an in-frame deletion of amino acids 319-358 (PMIDs 9259196, 10737124). This includes part of the GAA catalytic barrel (amino acids 347-727) (Kroos et al, 2012, PMID 22253258; Deming et al, 2017; DOI 10.1101/212837) (PVS1_Strong). At least 7 probands have been reported with this variant, at least 5 of them with reported GAA activity <10% normal in lymphocytes, leukocytes or muscle samples, or <30% normal in cultured fibroblasts, or in the affected range in a clinically validated dried blood spot assay (PP4_Moderate). Of these individuals, 6 are compound heterozygous for the variant and another variant in GAA that has been classified as pathogenic or likely pathogenic by the ClinGen Lysosomal Diseases VCEP, including 2 confirmed in trans - c.2560C>T (p.Arg854Ter) (ClinVar Variation ID: 4034, SCV001371731.1) (PMID: 9259196), c.1437+1G>A (ClinVar Variation ID: 555864, SCV004227900.1), and 4 with phase unknown - c.1942G>A (p.Gly648Ser) (ClinVar Variation ID: 188902, SCV001371752.2) (PMID: 25455803), c.-32-13T>G (ClinVar Variation ID: 4027) (PMID: 22613277), c.1841C>A (p.Thr614Lys) (ClinVar Variation ID: 167113, SCV001371751.1) (PMID: 21484825), and c.525delT (ClinVar Variation ID: 4033, SCV001443331.1) (PMID: 29181627). In addition, two siblings are homozygous for the variant (PMID: 10737124) (PM3_VeryStrong). The highest population minor allele frequency in gnomAD v2.1.1 is 0.00002658 (3/112848 alleles) in the European non-Finnish population, 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: 370278). In summary, this variant meets the criteria to be classified as Pathogenic for Pompe disease based on the GAA-specific ACMG/AMP criteria applied, as specified by the ClinGen Lysosomal Diseases Variant Curation Expert Panel (Specifications Version 2.0): PVS1_Strong, PM3_Strong, PP4_Moderate, PM2_Supporting. (Classification approved by the ClinGen Lysosomal Diseases Variant Curation Expert Panel on February 6, 2024). -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jul 07, 2023	Studies have shown that this variant results in skipping of exon 6, but is expected to preserve the integrity of the reading-frame (PMID: 9259196). ClinVar contains an entry for this variant (Variation ID: 370278). This variant is also known as IVS6-22T>G. This variant has been observed in individual(s) with glycogen storage disease type II (GSD II) (PMID: 9259196, 10737124, 22613277). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. It has also been observed to segregate with disease in related individuals. This variant is present in population databases (rs762260678, gnomAD 0.003%). This sequence change falls in intron 6 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 likely results in a shortened protein product. For these reasons, this variant has been classified as Pathogenic. -

not provided Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Sep 20, 2021	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Oct 29, 2019	Predicted to create a strong cryptic splice acceptor site upstream of the natural splice acceptor site of intron 6 and analysis of patient cDNA demonstrates an in-frame insertion of 21 nucleotides and skipping of exon 6 causing insertion of 7 incorrect amino acids and loss of 40 amino acids encoded by exon 6 (Adams et al., 1997; Vorgerd et al., 1998); Not observed at a significant frequency in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 31342611, 29181627, 9259196, 22613277, 10737124, 17643989, 21179066, 21484825, 27408821, 22676651, 25455803, 23013746, 9529346) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.83
CADD	Benign	20
DANN	Benign	0.56

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.97		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.97		Position offset: 1
DS_AL_spliceai		0.56		Position offset: 22

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

Publications

LitVar

Other links and lift over

dbSNP: rs762260678; hg19: chr17-78082266;