rs148875609

chr20-3223398-C-T

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_033453.4(ITPA):c.521C>T(p.Ala174Val) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000266 in 1,613,812 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A174T) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.000046 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000025 (0 hom.)
• Consequence: ITPA NM_033453.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.915

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]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.05412501).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ITPA	NM_033453.4	c.521C>T	p.Ala174Val	missense_variant	8/8	ENST00000380113.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ITPA	ENST00000380113.8	c.521C>T	p.Ala174Val	missense_variant	8/8	1	NM_033453.4	P1

Frequencies

GnomAD3 genomes AF: 0.0000460 AC: 7 AN: 152226 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.000121

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: 0.0000294

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000518 AC: 13 AN: 250792 Hom.: 0 AF XY: 0.0000369 AC XY: 5 AN XY: 135606

Gnomad AFR exome AF: 0.000247

Gnomad AMR exome AF: 0.0000868

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.0000463

Gnomad NFE exome AF: 0.0000441

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000246 AC: 36 AN: 1461586 Hom.: 0 Cov.: 31 AF XY: 0.0000261 AC XY: 19 AN XY: 727080

Gnomad4 AFR exome AF: 0.000149

Gnomad4 AMR exome AF: 0.0000894

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.0000188

Gnomad4 NFE exome AF: 0.0000207

Gnomad4 OTH exome AF: 0.0000331

GnomAD4 genome AF: 0.0000460 AC: 7 AN: 152226 Hom.: 0 Cov.: 32 AF XY: 0.0000403 AC XY: 3 AN XY: 74364

Gnomad4 AFR AF: 0.000121

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: 0.0000294

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000152 Hom.: 0

Bravo AF: 0.0000378

ESP6500AA AF: 0.000227 AC: 1

ESP6500EA AF: 0.000116 AC: 1

ExAC AF: 0.0000659 AC: 8

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Inosine triphosphatase deficiency Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Dec 11, 2023

This sequence change replaces alanine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 174 of the ITPA protein (p.Ala174Val). This variant is present in population databases (rs148875609, gnomAD 0.03%). This variant has not been reported in the literature in individuals affected with ITPA-related conditions. ClinVar contains an entry for this variant (Variation ID: 464835). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Not Available"; PolyPhen-2: "Benign"; Align-GVGD: "Not Available". The valine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. 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	Benign	0.11
BayesDel_addAF	Benign	-0.47	T
BayesDel_noAF	Benign	-0.61
Cadd	Benign	16
Dann	Benign	0.97
DEOGEN2	Uncertain	0.66	D;.;.
Eigen	Benign	-0.91
Eigen_PC	Benign	-0.92
FATHMM_MKL	Benign	0.11	N
LIST_S2	Uncertain	0.91	D;D;D
M_CAP	Benign	0.0048	T
MetaRNN	Benign	0.054	T;T;T
MetaSVM	Benign	-0.99	T
MutationAssessor	Uncertain	2.2	M;.;.
MutationTaster	Benign	1.0	N;N;N
PrimateAI	Benign	0.26	T
PROVEAN	Benign	-1.2	N;N;N
REVEL	Benign	0.041
Sift	Benign	0.13	T;T;T
Sift4G	Benign	0.14	T;T;T
Polyphen		0.0010	B;.;.
Vest4		0.051
MVP		0.15
MPC		0.29
ClinPred		0.025	T
GERP RS		0.38
Varity_R		0.25
gMVP		0.45

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: rs148875609; hg19: chr20-3204044;