Imprinted genes as potential genetic and epigenetic toxicologic targets

Genomic imprinting is an epigenetic phenomenon in eutherian mammals that re sults in the differential expression of the paternally and maternally inher ited alleles of a gene. Imprinted genes are necessary for normal mammalian development. This requirement has been proposed to have evolved because of an interparental genetic battle for the utilization of maternal resources d uring gestation and postnatally. The nonrandom requisite for monoallelic ex pression of a subset of genes has also resulted in the formation of suscept ibility loci for neurobehavioral disorders, developmental disorders, and ca ncer. Since imprinting involves both cytosine methylation within CpG island s and changes in chromatin structure, imprinted genes are potential targets for dysregulation by epigenetic toxicants that modify DNA methylation and histone acetylation.