rs1555694770

Positions:

• chr18-62148213-C-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_176787.5(PIGN):​c.674+1G>A variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: PIGN NM_176787.5 splice_donor, intron
• Clinical Significance: Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 7.21

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 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 18-62148213-C-T is Pathogenic according to our data. Variant chr18-62148213-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 505688.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr18-62148213-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
PIGN	NM_176787.5	c.674+1G>A		splice_donor_variant, intron_variant		ENST00000640252.2	NP_789744.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
PIGN	ENST00000640252.2	c.674+1G>A		splice_donor_variant, intron_variant		1	NM_176787.5	ENSP00000492233.1
PIGN	ENST00000400334.7	c.674+1G>A		splice_donor_variant, intron_variant		1		ENSP00000383188.2
PIGN	ENST00000638424.1	n.674+1G>A		splice_donor_variant, intron_variant		5		ENSP00000491963.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1386396 Hom.: 0 Cov.: 28 AF XY: 0.00 AC XY: 0 AN XY: 683344

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.: 33

Bravo AF: 0.00000378

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Multiple congenital anomalies-hypotonia-seizures syndrome 1 Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Nov 20, 2023	This sequence change affects a donor splice site in intron 8 of the PIGN gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and 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: 505688). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Dec 27, 2021	- -

Multiple congenital anomalies-hypotonia-seizures syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Mar 21, 2017

The c.674+1G>A (NM_176787.4) variant in PIGN has not been previously reported in individuals with Multiple congenital anomalies-hypotonia-seizures syndrome and was absent from large population studies. This variant occurs in the invariant r egion (+/- 1,2) of the splice consensus sequence and is predicted to cause alter ed splicing leading to an abnormal or absent protein. Biallelic loss of function of the PIGN gene has been associated with Multiple congenital anomalies-hypoton ia-seizures syndrome. In summary, although additional studies are required to fu lly establish a null effect, the c.674+1G>A variant is likely pathogenic for Mul tiple congenital anomalies-hypotonia-seizures syndrome in an autosomal recessive manner based upon its predicted impact on protein function. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.47	D
BayesDel_noAF	Pathogenic	0.43
CADD	Pathogenic	27
DANN	Uncertain	1.0
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	0.99	D
GERP RS		5.9

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.99		Position offset: 1

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

Publications

LitVar

Other links and lift over

dbSNP: rs1555694770; hg19: chr18-59815446;