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Open Access Short report

Evidence of reactive oxygen species-mediated damage to mitochondrial DNA in children with typical autism

Eleonora Napoli1, Sarah Wong1 and Cecilia Giulivi12*

Author Affiliations

1 Department of Molecular Biosciences, University of California, One Shields Ave, 1120 Haring Hall, Davis, CA, 95616, USA

2 Medical Investigations of Neurodevelopmental Disorders (M.I.N.D.) Institute, University of California, Davis, CA, 95616, USA

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Molecular Autism 2013, 4:2  doi:10.1186/2040-2392-4-2

Published: 25 January 2013

Abstract

Background

The mitochondrial genome (mtDNA) is particularly susceptible to damage mediated by reactive oxygen species (ROS). Although elevated ROS production and elevated biomarkers of oxidative stress have been found in tissues from children with autism spectrum disorders, evidence for damage to mtDNA is lacking.

Findings

mtDNA deletions were evaluated in peripheral blood monocytic cells (PBMC) isolated from 2–5 year old children with full autism (AU; n = 67), and typically developing children (TD; n = 46) and their parents enrolled in the CHildhood Autism Risk from Genes and Environment study (CHARGE) at University of California Davis. Sequence variants were evaluated in mtDNA segments from AU and TD children (n = 10; each) and their mothers representing 31.2% coverage of the entire human mitochondrial genome. Increased mtDNA damage in AU children was evidenced by (i) higher frequency of mtDNA deletions (2-fold), (ii) higher number of GC→AT transitions (2.4-fold), being GC preferred sites for oxidative damage, and (iii) higher frequency of G,C,T→A transitions (1.6-fold) suggesting a higher incidence of polymerase gamma incorporating mainly A at bypassed apurinic/apyrimidinic sites, probably originated from oxidative stress. The last two outcomes were identical to their mothers suggesting the inheritance of a template consistent with increased oxidative damage, whereas the frequency of mtDNA deletions in AU children was similar to that of their fathers.

Conclusions

These results suggest that a combination of genetic and epigenetic factors, taking place during perinatal periods, results in a mtDNA template in children with autism similar to that expected for older individuals.

Keywords:
Autism; Mitochondria; Mitochondrial DNA; Oxidative damage; Bioenergetics