Environmental and Molecular Mutagenesis (EMM) Editor's Choice - October 2012
The Editor's Choice for October is "Levels of Select PCB and PBDE Congeners in Human Postmortem Brain Reveal Possible Environmental Involvement in15q11-q13 Duplication Autism Spectrum Disorder" by M.M. Mitchell, R. Woods, L.-H. Chi, R.J. Schmidt, I.N. Pessah, P.J. Kostyniak, and J.M. LaSalle.
Human population-based studies, along with some studies in rodents, suggest environmental organic pollutants can bioaccumulate in lipid-rich brain tissue and result in abnormal brain development. In order to determine whether such pollutants could be responsible for the increasing prevalence of autism spectrum disorder, Mitchell et al. measured levels of persistent organic pollutants in 107 human post-mortem brain samples. Tissue samples from three groups of individuals were tested: namely, tissue samples from normal individuals, tissue samples from individuals with autism due to an unknown cause, and tissue samples from individuals with a neurodevelomental disorder associated with a known genetic defect. The levels of fifteen different chemicals (seven polybrominated diphenyl ethers and eight polychlorinated biphenyls) were measured in each sample. Mitchell et al. found that 2,2’,3,5’,6-pentachlorobiphenyl (PCB 95) was present at higher levels in individuals with a 15q11-q13 duplication as compared to that in tissue samples from normal individuals. Also, based on the idea that chemically-induced changes in DNA methylation profile might predispose individuals to genetic instability, Mitchell et al. examined the methylation levels in a repetitive DNA sequence element (called LINE-1) in brain DNA from the same individuals. The investigators found a decrease in LINE-1 methylation in individuals with the 15q11-q13 duplication. Using this approach, therefore, Mitchell et al. were able to effectively integrate information on environmental chemical exposure, epigenetic alteration, and copy number variation, which represents significant progress toward understanding the causes of autism. Environ. Mol. Mutagen. 53:589-598 Published 2012 Wiley Periodicals, Inc.