A Mouse Model for Dietary Effects on Epigenetic Silencing

DESCRIPTION (provided by applicant): Epigenetic silencing plays a major role in cancer formation because it leads to aberrant inactivation of tumor suppressor genes. Therefore, a fundamental goal for cancer prevention is to inhibit aberrant silencing in somatic cells. Diet provides a potential tool to help reduce cancer incidence because some food components affect epigenetic processes. However, whether diet can prevent aberrant silencing is not known, in part because animal models to study silencing are not available. Thus, approaches to determine if specific foods, or mixtures of foods, can prevent aberrant silencing in vivo are not possible at this time. The goal of this R21 application is to create a mouse model of inducible silencing and then use the model to demonstrate dietary inhibition of silencing. Two specific aims are proposed. The first is to create a transgenic mouse strain in which silencing of a target gene promoter is induced when transcription is repressed to low levels. This mouse model will contain a doxycycline (Dox) repressible promoter linked to the selectable mouse Aprt coding region. Promoter repression will be achieved by placing Dox in the mouse drinking water, which will lead to gene silencing in cells in a variety of mouse tissues. Silencing will be detected with an assay that identifies cells that are Aprt deficient and correlated with promoter repression. Prevention of histone deacetylation at the target promoter inhibits the Dox-mediated reduction in mRNA levels and resultant silencing. Therefore, the second aim will demonstrate that a mouse diet containing broccoli sprouts, which are enriched for a histone deacetylase inhibitor, will prevent both the reduction of mRNA levels and the induction of silencing in mouse tissues. Successful completion of these aims will establish that diet can prevent epigenetic silencing in vivo and provide an animal model to explore this relationship in a variety of experimental contexts. PUBLIC HEALTH RELEVANCE: Diet can play a major role in increasing or decreasing cancer incidence, but the mechanisms by which it does so remain to be determined. One pathway for cancer formation is epigenetic silencing of tumor suppressor genes. The goal of this application is to create a mouse model for inducible gene silencing and then demonstrate that a diet enriched with a compound that can inhibit an epigenetic process can also inhibit epigenetic silencing.