In the Rao lab, I will probe how chromatin regulatory proteins called TETs influence the formation of specialized cell types and how dysregulation of their activity is involved in cancer. In the body, stem cells and other types of precursor cells can give rise to a variety of specialized cell types such as neurons or red blood cells, a process that requires widespread reprogramming of gene expression. One way to achieve these transcriptional programs involves the addition of chemical “marks” to the DNA itself, which control the activity of nearby genes and enhancers. These chemical marks are laid down by specific groups of DNA-modifying enzymes, like TETs, that together can “write” and “erase” these DNA modifications. Using different molecular and biochemical approaches coupled to genome-wide sequencing analyses, I will explore how TETs’ activities can govern the transcriptional state of mouse embryonic stem cells, their ability to produce specialized cell types, and their contribution in cancer. These findings could lead to a better understanding of cancer and other diseases in which dysregulation of DNA modification frequently occurs.