Bryan studies how cells remember who they are, and how it is that they sometimes decide to turn into something else. If cells all contain the same genetic information, why, for example, are skin cells different from nerve cells in the brain? This all depends on which subset of genes is switched on in these cells. Bryan studies how chemical modifications to histone proteins, which help to package DNA in the cell nucleus, affect whether genes are active or silent. He also studies the effects of drugs that alter these chemical modifications, and how they can be used to treat leukaemia.