Several studies have shown that cocaine (COC) treatment of male rodents results in offspring with attention and working memory deficits. These findings, combined with the report of reduced biparietal diameter of the head in the newborn mice fathered by COC-exposed males, make a compelling case that COC is capable of producing neuroteratological effects via paternal gametes. An intriguing possibility is that these paternal effects of COC involve epigenetic mutations in male germ cells leading to modified parental gene imprinting - a phenomenon of monoallelic parent-of-origin-dependent expression of a group of genes, which play important roles in neurodevelopment and behavior. There is good evidence that methylation of cytosine on CpG dinucleotides is a key epigenetic DNA modification involved in imposing differential parental imprinting. In particular, chromosomes of paternal and maternal origin contain differentially methylated regions (DMRs), which constitute an important mechanism for enforcing monoallelic expression of multiple imprinted genes. While the abilities of DMRs to enforce monoallelic gene expression (and even the levels of their differential methylation) are often developmental stage- and tissue-dependent, a group of primary DMRs are believed to be set up during gametogenesis, with the final imprinting outcomes resulting from interaction of these markers with the DNA transcription silencing/activation machinery specific for a given tissue and timing in the life of the organism. The formation and maintenance of these primary DMRs depends on several factors including the presence of DNA methyltransferases 1 and 3a, whose expression levels we found to be altered in germ cells of chronically COC-exposed mice. This finding is consistent with the proposition that COC may cause paternally-transmitted effects by interfering with the establishment/maintenance of gene imprinting methylation patterns in male gametes. The present application is the first step toward addressing the hypothesis that paternal COC-exposure leads to epigenetic mutations, such as altered DMR methylation in the chromatin of paternally-derived chromosomes, taking place in male gametes and inherited by the cells of the offspring, including neurons and glia comprising the central nervous system, which results in modified expression of imprinted genes in the brain. I) We will investigate the idea that paternal COC exposure leads to abnormal expression of imprinted genes in the neuronal and glial cells in the brain of the offspring, specifically in the regions involved in working memory and attention. II) We will examine the notion that the offspring of COC-exposed fathers may have changes in the methylation state of DMRs guiding gene imprinting in the aforementioned neural cells. Ill) We will evaluate the suggestion that COC-induced paternally-transmitted alterations in gene imprinting start with the interference of COC with imprinting markers (specifically with methylation of primary DMRs) in male gametes. ? ? ?
