rs552929702

Positions:

• chr17-80107809-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 1P and 1B. PM2_Supporting BS3_Supporting

This summary comes from the ClinGen Evidence Repository: The NM_000152.5:c.868A>G variant in GAA is predicted to result in the substitution of asparagine by aspartate at amino acid 290 (p.Asn290Asp). It has been identified in six individuals by newborn screening, none with clinical features consistent with Pompe disease (PMID:32064362, 37414610; Essawi et al. 2021, Egypt J Med Hum Genet 22:87). Four of these individuals are homozygous for the variant and have African ancestry (PMID:37414610), and two patients are compound heterozygous for the variant and a variant that has been classified as pathogenic by the ClinGen Lysosomal Diseases VCEP, either c.2105G>A (p.Arg702His), phase unconfirmed, (ClinVar Variation ID: 426278, SCV004809068.1) (PMID:32064362) or c.2238G>C (p.Trp746Cys) (ClinVar Variation ID: 265160, SCV002032122.1). In the latter, patient, the variants were confirmed to be in trans, and the father, who was described as "completely normal" but with reduced GAA activity, is homozygous for c.868A>G (p.Asn290Asp). Additional cases have been reported (PMID:22644586, 33073007) but the second variant and clinical details were not provided. Due to the lack of evidence for clinical symptoms in the patients with this variant, PP4 and PM3 were not applied. The highest population minor allele frequency in gnomAD v2.1.1. is 0.00004 (1/24356, no homozygotes) in the African population, which is lower than the ClinGen Lysosomal Diseases VCEP's threshold (<0.001) for PM2_Supporting, meeting this criterion (PM2_Supporting). When expressed in COS cells, this variant was classified as Class E ("presumably nonpathogenic") by Kroos et al, 2012 (PMID:22644586). This includes 71% GAA activity in cells and 38% in medium, with synthesis and processing on Western blot (BS3_Supporting). The computational predictor REVEL gives a score of 0.561 which is neither above nor below the thresholds predicting a damaging (>0.7) or benign (<0.5) impact on GAA function. There is a ClinVar entry for this variant (Variation ID: 498117). In summary, this variant meets the criteria to be classified as a variant of uncertain significance for Pompe disease. The classification was first approved by the ClinGen Lysosomal Diseases Variant Curation Expert Panel on October 21, 2022. Since then, the data for this variant have been re-evaluated and new data have been included but the classification remains the same. The classification of variant of uncertain significance was reapproved on April 16, 2024. GAA-specific ACMG/AMP criteria met, as specified by the ClinGen Lysosomal Diseases Variant Curation Expert Panel (Specifications Version 2.0): PM2_Supporting, BS3_Supporting. LINK:https://erepo.genome.network/evrepo/ui/classification/CA8815078/MONDO:0009290/010

• Frequency:
  • Genomes: 𝑓 0.000033 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000022 (2 hom.)
• Consequence: GAA NM_000152.5 missense
• Clinical Significance: Uncertain significance reviewed by expert panel P:1 U:8
• Conservation: PhyloP100: 6.09

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 Uncertain_significance. Variant got 0 ACMG points.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAA	NM_000152.5	c.868A>G	p.Asn290Asp	missense_variant	5/20	ENST00000302262.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAA	ENST00000302262.8	c.868A>G	p.Asn290Asp	missense_variant	5/20	1	NM_000152.5	P1

Frequencies

GnomAD3 genomes AF: 0.0000263 AC: 4 AN: 152122 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000966

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

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

GnomAD3 exomes AF: 0.00000408 AC: 1 AN: 245126 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 133458

Gnomad AFR exome AF: 0.0000638

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000219 AC: 32 AN: 1459490 Hom.: 2 Cov.: 56 AF XY: 0.0000275 AC XY: 20 AN XY: 726058

Gnomad4 AFR exome AF: 0.000658

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: 0.00000270

Gnomad4 OTH exome AF: 0.0000830

GnomAD4 genome AF: 0.0000328 AC: 5 AN: 152240 Hom.: 0 Cov.: 33 AF XY: 0.0000269 AC XY: 2 AN XY: 74442

Gnomad4 AFR AF: 0.000120

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Bravo AF: 0.0000113

ExAC AF: 0.00000825 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1 Uncertain:8

Revision: reviewed by expert panel

Submissions by phenotype

Glycogen storage disease, type II Pathogenic:1 Uncertain:3

Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Feb 13, 2020	- -
Uncertain significance, reviewed by expert panel	curation	ClinGen Lysosomal Storage Disorder Variant Curation Expert Panel	Apr 16, 2024	The NM_000152.5:c.868A>G variant in GAA is predicted to result in the substitution of asparagine by aspartate at amino acid 290 (p.Asn290Asp). It has been identified in six individuals by newborn screening, none with clinical features consistent with Pompe disease (PMID: 32064362, 37414610; Essawi et al. 2021, Egypt J Med Hum Genet 22:87). Four of these individuals are homozygous for the variant and have African ancestry (PMID: 37414610), and two patients are compound heterozygous for the variant and a variant that has been classified as pathogenic by the ClinGen Lysosomal Diseases VCEP, either c.2105G>A (p.Arg702His), phase unconfirmed, (ClinVar Variation ID: 426278, SCV004809068.1) (PMID: 32064362) or c.2238G>C (p.Trp746Cys) (ClinVar Variation ID: 265160, SCV002032122.1). In the latter, patient, the variants were confirmed to be in trans, and the father, who was described as "completely normal" but with reduced GAA activity, is homozygous for c.868A>G (p.Asn290Asp). Additional cases have been reported (PMID: 22644586, 33073007) but the second variant and clinical details were not provided. Due to the lack of evidence for clinical symptoms in the patients with this variant, PP4 and PM3 were not applied. The highest population minor allele frequency in gnomAD v2.1.1. is 0.00004 (1/24356, no homozygotes) in the African population, which is lower than the ClinGen Lysosomal Diseases VCEP's threshold (<0.001) for PM2_Supporting, meeting this criterion (PM2_Supporting). When expressed in COS cells, this variant was classified as Class E ("presumably nonpathogenic") by Kroos et al, 2012 (PMID:22644586). This includes 71% GAA activity in cells and 38% in medium, with synthesis and processing on Western blot (BS3_Supporting). The computational predictor REVEL gives a score of 0.561 which is neither above nor below the thresholds predicting a damaging (>0.7) or benign (<0.5) impact on GAA function. There is a ClinVar entry for this variant (Variation ID: 498117). In summary, this variant meets the criteria to be classified as a variant of uncertain significance for Pompe disease. The classification was first approved by the ClinGen Lysosomal Diseases Variant Curation Expert Panel on October 21, 2022. Since then, the data for this variant have been re-evaluated and new data have been included but the classification remains the same. The classification of variant of uncertain significance was reapproved on April 16, 2024. GAA-specific ACMG/AMP criteria met, as specified by the ClinGen Lysosomal Diseases Variant Curation Expert Panel (Specifications Version 2.0): PM2_Supporting, BS3_Supporting. -
Uncertain significance, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Sep 05, 2021	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Jan 29, 2024	This sequence change replaces asparagine, which is neutral and polar, with aspartic acid, which is acidic and polar, at codon 290 of the GAA protein (p.Asn290Asp). This variant is present in population databases (rs552929702, gnomAD 0.004%), including at least one homozygous and/or hemizygous individual. To date, this missense change has only been observed in individual(s) with abnormal newborn screening for Pompe disease (PMID: 32064362; Invitae). 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: 498117). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt GAA protein function with a positive predictive value of 95%. This variant disrupts the p.Asn290 amino acid residue in GAA. Other variant(s) that disrupt this residue have been observed in individuals with GAA-related conditions (PMID: 22081099; Invitae), which suggests that this may be a clinically significant amino acid residue. For these reasons, this variant has been classified as Pathogenic. -

not provided Uncertain:4

Uncertain significance, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jan 30, 2018	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Aug 30, 2023	- -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Oct 17, 2023	Identified with a second variant in the GAA gene in an asymptomatic infant with reduced alpha-glucosidase activity on newborn screening; the variant was apparently homozygous in the father who was clinically asymptomatic, but had significantly reduced alpha-glucosidase activity (Mona Essawi et al., 2021); Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 22253258, 19343043, 22644586, 32064362, 37414610, Essawi2021) -
Uncertain significance, criteria provided, single submitter	clinical testing	Mayo Clinic Laboratories, Mayo Clinic	Oct 11, 2022	PM2 -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Jun 05, 2021

Variant summary: GAA c.868A>G (p.Asn290Asp) results in a conservative amino acid change located in the Glycoside hydrosylase family 31, N-terminal domain (IPR025887) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 4.1e-06 in 245126 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. Although this variant is listed as "non-pathogenic" in the Pompe disease database without any supporting clinical evidence, to our knowledge, no occurrence of c.868A>G in individuals affected with Glycogen Storage Disease, Type 2 (Pompe Disease) and no experimental evidence demonstrating its impact on protein function have been reported. Two 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 uncertain significance. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.83
BayesDel_addAF	Uncertain	0.13	D
BayesDel_noAF	Uncertain	-0.050
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.92	D;D
Eigen	Pathogenic	0.77
Eigen_PC	Pathogenic	0.69
FATHMM_MKL	Pathogenic	0.99	D
M_CAP	Pathogenic	0.36	D
MetaRNN	Pathogenic	0.91	D;D
MetaSVM	Uncertain	0.78	D
MutationAssessor	Pathogenic	2.9	M;M
MutationTaster	Benign	0.96	D;D
PrimateAI	Uncertain	0.63	T
PROVEAN	Pathogenic	-4.5	D;D
REVEL	Uncertain	0.56
Sift	Uncertain	0.0090	D;D
Sift4G	Pathogenic	0.0	D;D
Polyphen		1.0	D;D
Vest4		0.94
MutPred		0.39		Gain of phosphorylation at Y292 (P = 0.0793);Gain of phosphorylation at Y292 (P = 0.0793);
MVP		1.0
MPC		0.58
ClinPred		0.99	D
GERP RS		5.3
Varity_R		0.90
gMVP		0.95

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		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: rs552929702; hg19: chr17-78081608;