On the other hand, a hypomethylation of non-coding region has been linked to chromosome instability (Watanabe and Maekawa, 2010). Genomic imprinting, a genetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner,

involves the methylation of the unexpressed allele (Eggermann et al., 2011). Post-translational modifications of histone tails, have been shown to be important in altering chromatin structure and therefore DNA accessibility (Kouzarides, 2007). The functional effects of such modifications depend on the specific amino acid that is modified and on the specific covalently attached group: e.g. acetylation results in the loosening of chromatin and lends itself to replication and transcription, whereas methylated histones tight DNA and

restrict access to various enzymes. Histones modifications can regulate gene GDC-0941 clinical trial expression, chromatin remodeling, cell survival and cell death (Kouzarides, 2007). microRNAs (miRNA) are single-stranded RNAs of about 21–23 nucleotides in length that are transcribed from DNA but not translated into proteins (non-coding RNAs). Their functional role 3-Methyladenine clinical trial is gene expression regulation mediated by a control of messenger RNA (mRNA) stability or translation. Mature miRNAs can be totally complementary to the mRNA: the paring between the miRNA and the mRNA leads to the mRNA degradation, therefore impairing gene expression. Otherwise miRNA can be only partially complementary to mRNA molecules: their regulatory function is thus mediated by a block in mRNA translation (Jackson and Standart, 2007 and Pillai et al., 2007). One single miRNA regulates the expression

of hundreds of different target genes, vice versa one gene can be regulated by hundreds of miRNA. MicroRNAs play a key role in diverse biological processes, including development, cell proliferation, differentiation, and apoptosis. Emerging evidence indicates that epigenetic changes are important cellular and ioxilan molecular correlates of neurodegenerative diseases resulting from chronic neurotoxic chemical exposure. Kwok et al. recognized the role of DNA methylation following environmental chemical exposure in the pathogenesis of neurodegenerative diseases. DNA methylation causes an allelic skewing in a significant proportion of genes, that is, one allele can be transcribed or expressed at a higher level than the other allele, differentiating between the maternal and paternal origin allele. This phenomenon may determine how an individual’s genotype can alter the effect an environmental factor has on their risk of developing neurodegeneration (Kanthasamy et al., 2012). Exposure to dichlorodiphenyltrichloroethane (DDT) alters the methylation pattern in the hypothalamus of young male rats: the experiment conducted by Shutoh et al. (2009) showed that 6 CpG islands (in Sst, Gal, Arf1, Ttr, Msx1 amd Grifin genes) were significantly hypomethylated compared with controls.