17-39687971-G-GC

Position:

• chr17-39687971-G-GC

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1 PM2 PP5_Moderate

The NM_033419.5(PGAP3):​c.43_44insG​(p.Ala15GlyfsTer12) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: PGAP3 NM_033419.5 frameshift
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 2.94

Genes affected

PGAP3 (HGNC:23719): (post-GPI attachment to proteins phospholipase 3) This gene encodes a glycosylphosphatidylinositol (GPI)-specific phospholipase that primarily localizes to the Golgi apparatus. This ubiquitously expressed gene is predicted to encode a seven-transmembrane protein that removes unsaturated fatty acids from the sn-2 position of GPI. The remodeling of the constituent fatty acids on GPI is thought to be important for the proper association between GPI-anchored proteins and lipid rafts. The tethering of proteins to plasma membranes via posttranslational GPI-anchoring is thought to play a role in protein sorting and trafficking. Mutations in this gene cause an autosomal recessive form of neurologic hyperphosphatasia with cognitive disability (HPMRS4). Alternative splicing results in multiple transcript variants encoding distinct isoforms. [provided by RefSeq, Jul 2017]

ERBB2 (HGNC:3430): (erb-b2 receptor tyrosine kinase 2) This gene encodes a member of the epidermal growth factor (EGF) receptor family of receptor tyrosine kinases. This protein has no ligand binding domain of its own and therefore cannot bind growth factors. However, it does bind tightly to other ligand-bound EGF receptor family members to form a heterodimer, stabilizing ligand binding and enhancing kinase-mediated activation of downstream signalling pathways, such as those involving mitogen-activated protein kinase and phosphatidylinositol-3 kinase. Allelic variations at amino acid positions 654 and 655 of isoform a (positions 624 and 625 of isoform b) have been reported, with the most common allele, Ile654/Ile655, shown here. Amplification and/or overexpression of this gene has been reported in numerous cancers, including breast and ovarian tumors. Alternative splicing results in several additional transcript variants, some encoding different isoforms and others that have not been fully characterized. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant located near the start codon (<100nt), not predicted to undergo nonsense mediated mRNA decay. There are 49 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 17-39687971-G-GC is Pathogenic according to our data. Variant chr17-39687971-G-GC is described in ClinVar as [Likely_pathogenic]. Clinvar id is 3068561.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
PGAP3	NM_033419.5	c.43_44insG	p.Ala15GlyfsTer12	frameshift_variant	1/8	ENST00000300658.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
PGAP3	ENST00000300658.9	c.43_44insG	p.Ala15GlyfsTer12	frameshift_variant	1/8	1	NM_033419.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1312764 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 641086

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hyperphosphatasia-intellectual disability syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Molecular Genetics, Royal Melbourne Hospital

Aug 01, 2023

This sequence change in PGAP3 is a frameshift variant that may cause a premature stop codon, p.(Ala15Glyfs*12), that is located in a nonsense-mediated decay insensitive region (first 100 bp) predicted to reduce nonsense-mediated decay efficiency (PMID: 27618451). However, it is a truncation of a functionally important region (signal peptide) in a gene where loss of function is an established disease mechanism. This variant is absent from the population database gnomAD v2.1 and v3.1. To our knowledge, this variant is novel and has not been previously reported in the relevant scientific literature or databases. At least one patient with this variant displayed increased Alkaline phosphatase levels (Royal Melbourne Hospital), which is highly specific for hyperphosphatasia-intellectual disability syndrome (PMID: 30217754, 30345601). Based on the classification scheme RMH Modified ACMG/AMP Guidelines v1.6.1, this variant is classified as LIKELY PATHOGENIC. Following criteria are met: PVS1_Strong, PM2_Supporting, PP4. -

Computational scores

Source: dbNSFP v4.3

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: rs765928877; hg19: chr17-37844224;