rs1555685797

Variant names:

• chr18-62113309-AG-A
• rs1555685797
• NM_176787.5:c.1258delC

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_176787.5(PIGN):​c.1258delC​(p.Leu420PhefsTer5) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000689 in 1,450,978 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: PIGN NM_176787.5 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 3.55
• Publications: 0 publications found

Genes affected

PIGN (HGNC:8967): (phosphatidylinositol glycan anchor biosynthesis class N) This gene encodes a protein that is involved in glycosylphosphatidylinositol (GPI)-anchor biosynthesis. The GPI-anchor is a glycolipid found on many blood cells and serves to anchor proteins to the cell surface. This protein is expressed in the endoplasmic reticulum and transfers phosphoethanolamine (EtNP) to the first mannose of the GPI anchor. Two alternatively spliced variants, which encode an identical isoform, have been reported. [provided by RefSeq, Jul 2008]

PIGN Gene-Disease associations (from GenCC):

• multiple congenital anomalies-hypotonia-seizures syndrome 1

  Inheritance: AR Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics, G2P, Orphanet, ClinGen, PanelApp Australia
• Fryns syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 18-62113309-AG-A is Pathogenic according to our data. Variant chr18-62113309-AG-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 472207.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
PIGN	NM_176787.5	c.1258delC	p.Leu420PhefsTer5	frameshift_variant	Exon 16 of 31	ENST00000640252.2	NP_789744.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
PIGN	ENST00000640252.2	c.1258delC	p.Leu420PhefsTer5	frameshift_variant	Exon 16 of 31	1	NM_176787.5	ENSP00000492233.1
PIGN	ENST00000400334.7	c.1258delC	p.Leu420PhefsTer5	frameshift_variant	Exon 15 of 30	1		ENSP00000383188.2
PIGN	ENST00000638424.1	n.1258delC		non_coding_transcript_exon_variant	Exon 14 of 29	5		ENSP00000491963.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.89e-7 AC: 1 AN: 1450978 Hom.: 0 Cov.: 30 AF XY: 0.00000139 AC XY: 1 AN XY: 721514

African (AFR) AF: 0.00 AC: 0 AN: 32878

American (AMR) AF: 0.00 AC: 0 AN: 42966

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25948

East Asian (EAS) AF: 0.00 AC: 0 AN: 39422

South Asian (SAS) AF: 0.00 AC: 0 AN: 83478

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53088

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5736

European-Non Finnish (NFE) AF: 9.03e-7 AC: 1 AN: 1107566

Other (OTH) AF: 0.00 AC: 0 AN: 59896

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Multiple congenital anomalies-hypotonia-seizures syndrome 1 Pathogenic:3

Mar 25, 2024

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

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: PIGN c.1258delC (p.Leu420PhefsX5) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. The variant was absent in 224224 control chromosomes. To our knowledge, no occurrence of c.1258delC in individuals affected with Multiple Congenital Anomalies-Hypotonia Syndrome 1 and no experimental evidence demonstrating its impact on protein function have been reported. ClinVar contains an entry for this variant (Variation ID: 472207). Based on the evidence outlined above, the variant was classified as pathogenic. -

Jul 09, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Leu420Phefs*5) in the PIGN gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in PIGN are known to be pathogenic (PMID: 24253414, 27038415). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with PIGN-related conditions. ClinVar contains an entry for this variant (Variation ID: 472207). For these reasons, this variant has been classified as Pathogenic. -

Mar 30, 2023

Molecular Genetics, Royal Melbourne Hospital

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change is a deletion of 1 bp in exon 16 (of 31) of PIGN that is predicted to create a premature termination codon at position 424 (p.(Leu420Phefs*5)). It is expected to result in nonsense mediated decay, in a gene where loss of function is an established mechanism of disease (ClinGen). The variant is absent in a large population cohort (gnomAD v2.1 and v3.1), and has been reported as pathogenic (ClinVar). It has not been reported in the relevant medical literature. Based on the classification scheme RMH Modified ACMG Guidelines v1.3.2, this variant is classified as LIKELY PATHOGENIC. Following criteria are met: PVS1, PM2_Supporting. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		3.5
Mutation Taster		=0/200	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs1555685797; hg19: chr18-59780542;