rs746930990

Positions:

chr20-3223409-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM2PP3_StrongPP5

The NM_033453.4(ITPA):c.532C>T(p.Arg178Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000124 in 1,613,824 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 33)

Exomes 𝑓: 6.8e-7 ( 0 hom. )

Consequence

ITPA
NM_033453.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3U:1

Conservation

PhyloP100: 1.73

Variant links:

Genes affected

ITPA (HGNC:6176): (inosine triphosphatase) This gene encodes an inosine triphosphate pyrophosphohydrolase. The encoded protein hydrolyzes inosine triphosphate and deoxyinosine triphosphate to the monophosphate nucleotide and diphosphate. This protein, which is a member of the HAM1 NTPase protein family, is found in the cytoplasm and acts as a homodimer. Defects in the encoded protein can result in inosine triphosphate pyrophosphorylase deficiency which causes an accumulation of ITP in red blood cells. Alternate splicing results in multiple transcript variants. [provided by RefSeq, Jun 2012]

ITPA links:

ITPA (HGNC:):

ITPA links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Likely_pathogenic. Variant got 7 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

PP3

MetaRNN computational evidence supports a deleterious effect, 0.992

PP5

Variant 20-3223409-C-T is Pathogenic according to our data. Variant chr20-3223409-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 218090.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Pathogenic=2}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
ITPA	NM_033453.4 linkuse as main transcript	c.532C>T	p.Arg178Cys	missense_variant	8/8	ENST00000380113.8	NP_258412.1	Q9BY32-1A0A0S2Z3W7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
ITPA	ENST00000380113.8 linkuse as main transcript	c.532C>T	p.Arg178Cys	missense_variant	8/8	1	NM_033453.4	ENSP00000369456.3		Q9BY32-1

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152220

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

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:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.00000399

AC:

AN:

250780

Hom.:

AF XY:

0.00

AC XY:

AN XY:

135612

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.0000289

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:

6.84e-7

AC:

AN:

1461604

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

727086

show subpopulations

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:

8.99e-7

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152220

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74370

show subpopulations

Gnomad4 AFR

AF:

0.00

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:

0.0000147

Gnomad4 OTH

AF:

0.00

ExAC

AF:

0.00000824

AC:

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3Uncertain:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not provided

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Feb 17, 2022

Published functional studies demonstrate a damaging effect as R178C significantly reduces ITPA activity (Houndonougbo 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: 34645488, 27770805, 26224535, Zamzami2022[Review], 23770441, 34989426, 32129147) -

ITPA-related disorder

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

PreventionGenetics, part of Exact Sciences

Jul 20, 2023

The ITPA c.532C>T variant is predicted to result in the amino acid substitution p.Arg178Cys. This variant has been reported to be pathogenic for early infantile encephalopathy due to severely reduced inosine triphosphate pyrophosphatase (ITPase) activity (Kevelam et al. 2015. PubMed ID: 26224535; Shamseldin et al. 2021. PubMed ID: 34645488, Supplementary table S1). This variant is reported in 0.0029% of alleles in individuals of Latino descent in gnomAD (http://gnomad.broadinstitute.org/variant/20-3204055-C-T). This variant is interpreted as pathogenic. -

Developmental and epileptic encephalopathy, 35

Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Oct 01, 2015

- -

Inosine triphosphatase deficiency

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 23, 2022

This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 178 of the ITPA protein (p.Arg178Cys). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This missense change has been observed in individual(s) with early infantile encephalopathy (PMID: 26224535). ClinVar contains an entry for this variant (Variation ID: 218090). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. Experimental studies have shown that this missense change affects ITPA function (PMID: 32129147). In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.88

BayesDel_addAF

Pathogenic

0.46

BayesDel_noAF

Pathogenic

0.42

CADD

Pathogenic

DANN

Pathogenic

1.0

DEOGEN2

Pathogenic

0.96

D;.;.

Eigen

Pathogenic

0.97

Eigen_PC

Pathogenic

0.83

FATHMM_MKL

Uncertain

0.80

LIST_S2

Uncertain

0.97

D;D;D

M_CAP

Benign

0.057

MetaRNN

Pathogenic

0.99

D;D;D

MetaSVM

Pathogenic

0.86

MutationAssessor

Pathogenic

4.9

H;.;.

PrimateAI

Uncertain

0.64

PROVEAN

Pathogenic

-7.5

D;D;D

REVEL

Pathogenic

0.72

Sift

Pathogenic

0.0

D;D;D

Sift4G

Pathogenic

0.0

D;D;D

Polyphen

1.0

D;.;.

Vest4

0.97

MutPred

0.97

Loss of disorder (P = 0.0429);.;.;

MVP

0.78

MPC

1.2

ClinPred

1.0

GERP RS

5.8

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.97

gMVP

0.97

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.010

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over