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Inosine Triphosphate Pyrophosphohydrolase (ITPA) polymorphic sequence variants in adult hematological malignancy patients and possible association with mitochondrial DNA defects

Lookup NU author(s): Dr John Yarham, Professor Robert Taylor

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Abstract

Background: Inosine triphosphate pyrophosphohydrolase (ITPase) is a 'house-cleaning' enzyme that degrades non-canonical ('rogue') nucleotides. Complete deficiency is fatal in knockout mice, but a mutant polymorphism resulting in low enzyme activity with an accumulation of ITP and other non-canonical nucleotides, appears benign in humans. We hypothesised that reduced ITPase activity may cause acquired mitochondrial DNA (mtDNA) defects. Furthermore, we investigated whether accumulating mtDNA defects may then be a risk factor for cell transformation, in adult haematological malignancy (AHM). Methods: DNA was extracted from peripheral blood and bone marrow samples. Microarray-based sequencing of mtDNA was performed on 13 AHM patients confirmed as carrying the ITPA 94C>A mutation causing low ITPase activity, and 4 AHM patients with wildtype ITPA. The frequencies of ITPA 94C>A and IVS2+21A>C polymorphisms were studied from 85 available AHM patients. Results: ITPA 94C>A was associated with a significant increase in total heteroplasmic/homoplasmic mtDNA mutations (p<0.009) compared with wildtype ITPA, following exclusion of haplogroup variants. This suggested that low ITPase activity may induce mitochondrial abnormalities. Compared to the normal population, frequencies for the 94C>A and IVS2+21A>C mutant alleles among the AHM patients were higher for myelodyplastic syndrome (MDS)-but below significance; were approximately equivalent for chronic lymphoblastic leukemia; and were lower for acute myeloid leukemia. Conclusions: This study invokes a new paradigm for the evolution of MDS, where nucleotide imbalances produced by defects in 'house-cleaning' genes may induce mitochondrial dysfunction, compromising cell integrity. It supports recent studies which point towards an important role for ITPase in cellular surveillance of rogue nucleotides.

Publication metadata

Author(s): Zamzami MA, Duley JA, Price GR, Venter DJ, Yarham JW, Taylor RW, Catley LP, Florin THJ, Marinaki AM, Bowling F

Publication type: Article

Publication status: Published

Journal: Journal of Hematology & Oncology

Year: 2013

Volume: 6

Print publication date: 29/03/2013

Date deposited: 25/02/2014

ISSN (electronic): 1756-8722

Publisher: BioMed Central Ltd

URL: http://dx.doi.org/10.1186/1756-8722-6-24

DOI: 10.1186/1756-8722-6-24

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