rs1555945484

Positions:

• chrX-15331583-T-C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_002641.4(PIGA):​c.348A>G​(p.Ile116Met) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 24)
• Consequence: PIGA NM_002641.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.502

Genes affected

PIGA (HGNC:8957): (phosphatidylinositol glycan anchor biosynthesis class A) This gene encodes a protein required for synthesis of N-acetylglucosaminyl phosphatidylinositol (GlcNAc-PI), the first intermediate in the biosynthetic pathway of GPI anchor. The GPI anchor is a glycolipid found on many blood cells and which serves to anchor proteins to the cell surface. Paroxysmal nocturnal hemoglobinuria, an acquired hematologic disorder, has been shown to result from mutations in this gene. Alternate splice variants have been characterized. A related pseudogene is located on chromosome 12. [provided by RefSeq, Jun 2010]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 5 uncertain in NM_002641.4
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.874

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
PIGA	NM_002641.4	c.348A>G	p.Ile116Met	missense_variant	2/6	ENST00000333590.6
PIGA	NM_020473.3	c.13+3918A>G		intron_variant
PIGA	NR_033835.1	n.457+7A>G		splice_region_variant, intron_variant, non_coding_transcript_variant
PIGA	NR_033836.1	n.173+291A>G		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
PIGA	ENST00000333590.6	c.348A>G	p.Ile116Met	missense_variant	2/6	1	NM_002641.4	P1

Frequencies

GnomAD3 genomes Cov.: 24

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 24

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Sep 15, 2018

In summary, this variant is a novel missense change with uncertain impact on protein function. It has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a PIGA-related disease. This sequence change replaces isoleucine with methionine at codon 116 of the PIGA protein (p.Ile116Met). The isoleucine residue is moderately conserved and there is a small physicochemical difference between isoleucine and methionine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.46
BayesDel_addAF	Uncertain	0.046	T
BayesDel_noAF	Benign	-0.17
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.81	D;D;.
FATHMM_MKL	Uncertain	0.77	D
M_CAP	Uncertain	0.28	D
MetaRNN	Pathogenic	0.87	D;D;D
MetaSVM	Uncertain	0.20	D
MutationAssessor	Pathogenic	3.4	M;M;.
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Uncertain	0.63	T
PROVEAN	Uncertain	-2.7	D;.;.
REVEL	Uncertain	0.64
Sift	Pathogenic	0.0	D;.;.
Sift4G	Pathogenic	0.0010	D;D;.
Polyphen		1.0	D;D;.
Vest4		0.49
MutPred		0.79		Gain of methylation at R114 (P = 0.0725);Gain of methylation at R114 (P = 0.0725);Gain of methylation at R114 (P = 0.0725);
MVP		0.87
MPC		1.5
ClinPred		0.99	D
GERP RS		4.7
Varity_R		0.97
gMVP		0.93

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: rs1555945484; hg19: chrX-15349705;