Mutation Research 556 (2004) 127–134 Increased mutation in mice genetically predisposed to oxidative damage in the brain James R. Stringer, Jon S. Larson, Jared M. Fischer, Saundra L. Stringer ∗ Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, OH 45267, USA Received 11 May 2004; received in revised form 15 July 2004; accepted 16 July 2004 Abstract Harlequin (Hq) mice develop ataxia due to an X-linked recessive mutation in the gene encoding apoptosis-inducing factor (Aif). Brain cells in Hq mice contain the modified base 8-hydroxydeoxyguanosine (8-OHdG), suggesting that the defect in Aif causes increased DNA oxidation in these cells. Because oxidative damage is mutagenic, Hq mice might suffer increased mutation in the brain. To examine this possibility, mutation in the brain was assessed using the Tg(βA-G11PLAP) mouse model, which allows mutant cells to be visualized in tissue sections in situ. Hq mice exhibited more and larger patches of PLAP positive tissue in the brain. PLAP+ cells were observed in all areas of the brain. No increase in the number of PLAP+ cells was seen in three other tissues, suggesting that the effect of Aif deficiency on mutation was specific to brain. © 2004 Published by Elsevier B.V. Keywords: Apoptosis-inducing factor; Brain; In situ; Mononucleotide repeat; Mutation; Oxidative damage 1. Introduction Harlequin (Hq) mice carry an X-linked recessive mutation in the Pdcd8 (programmed cell death 8) gene, which encodes a protein known as apoptosis-inducing factor (Aif) [1–3]. While obviously named for its role in activating apoptosis in the brain [1], Aif protein ap- ∗ Corresponding author. Tel.: +1 513 558 0069; fax: +1 513 558 8474. E-mail address: S.Stringer@excite.com (S.L. Stringer). pears to act to prevent apoptosis by protecting against oxidative damage. Such a role is presumably mediated by the NADH oxidase activity of Aif. Aif contributes a major fraction of the NADH oxidase activity released from the mitochondrial intermembrane space [4]. The Hq allele of the Pdcd8 gene contains an intronic insertion of retrovirus proviral DNA, which reduces production of Aif to a level less than 20% of normal [3]. As Hq mice age, the amount of the modified base 8-hydroxydeoxyguanosine (8-OHdG) increases in a variety of cell types in the brain, including cerebellar 0027-5107/$ – see front matter © 2004 Published by Elsevier B.V. doi:10.1016/j.mrfmmm.2004.07.010