Determining the lasting impact on the developing epigenome by gestational toxic exposures

Geno-toxicity, whereby a toxic compound causes changes to the genetic code through mutation, has received widespread attention from the research community. Effects of toxic insults on the epigenome, where the genetic code is not directly affected, instead the ability to correctly read this code, remain poorly understood. The programme focusses on developing our understanding of the action and mechanism of chronic sub-toxic insults on the epigenome. These occur when a substances dose is insufficient to cause acute toxicity, but instead alters the environment of the DNA. The programme will have a particular emphasis on the lasting impact of these exposures during pregnancy. These toxic events can be environmental or pharmaceutical, and we aim to identify similarities and differences in such diverse challenges. We employ standard genomics and molecular biology techniques, in addition to using a new approach to studying epigenetics. We have generated a series of transgenic mouse lines, which can “see” the epigenetic status of a gene, through imaging of a mouse in vivo. Using these approaches, we can track epigenetic change through life-course and across generations, thereby “seeing” the toxic insult in its entirety.

The overall aim of this research programme is to understand the mechanisms by which toxic insults induce changes to epigenetic pathways. In particular, work will be directed towards understanding how exposures during mammalian gestation result in lifelong changes to regions of the epigenome. These exposures can be separated into two groups, environmental exposures, and pharmacological interventions.
Murine pregnancies will be subjected to chronic toxic insults and analysis will be performed on the exposed offspring. A series of mouse reporter lines will be utilised that enable the longitudinal in vivo tracking of epigenetic change. This is achieved through the knocking in of a bioluminescent reporter into the 3’ UTR of a series of imprinted genes, whose expression is regulated in a well-defined epigenetic, parent-of-origin specific manner. A series of studies have demonstrated that these genes can be sensitive to gestational environmental exposures, resulting in mis-expression of the reporter in exposed offspring. These methods will be employed in addition to more traditional genomics techniques to identify regions of the genome that are exquisitely sensitive to toxic insult. Particular focus will be played to the persistence of any changes that occur as the exposed offspring age, and whether these changes are transmitted to subsequent generations. Mechanistic information will be garnered through comparison of diverse toxic insults and their impact on sensitive regions of the genome.
These studies will provide novel information on the extent and lasting impact of toxic exposures during pregnancy. With the mechanistic information. In the longer term this research will help in the development of clear and well-informed Pregnancy Prevention Plans for tested drugs, particularly for those where there are no or only limited alternatives which remains a priority.