The genomic sequence does not change over time or in between tissues. However, epigenetic marks such as DNA methylation, histone modifications are variable between tissues, underlying the gene expression control that differentiates cell types. These epigenetic patterns are established early in development. Many of these epigenetic marks are heritable across cell division, ensuring the stability of tissue type cell composition. Over time the epigenetic patterns begin to degrade or shift.
I am interested in whether the shifts in DNA methylation and other epigenetic marks are shifted during their developmental establishment by toxic exposure. Secondly, it is possible that early exposures can accelerate or moderate the age-related degradation of epigenetic mark maintenance. My research currently uses imprinted genes and transposons in the mouse to measure longitudinal shifts in young and adult mice.