Early development of multi-cellular organisms is a highly dynamic process requiring an exquisite and tight control over establishment and maintenance of cellular identity. Deregulation of these processes can lead to malformations or disease, and hence proper understanding of both cellular differentiation and maintenance of cell fate will be relevant in many different clinical settings. The underlying defects are often not understood and need to be addressed to get more insight in the fundamental processes that are involved in normal and abnormal development.

For tissues to be properly specified, expression profiles have to become more restricted during development. Because every cell has the same DNA content this has to be determined at a higher order level of regulation. This is in part achieved by chromatin: the complex of DNA wrapped around an octamer of histones plus associated proteins. The histone-octamer contains histones H2A, H2B, H3, and H4, which have tails that can be modified. In addition, the DNA itself can be modified. The combination of modifications, sometimes also referred to as the epigenome, is believed to determine the accessibility and/or the transcriptional activity of DNA.

Polycomb group (PcG) proteins can change the chromatin structure, resulting in a repressive effect on gene transcription. Using zebrafish as a model system, we aim to elucidate how PcG proteins are involved in controlling tissue specification and maintenance. These studies contribute to our understanding of mechanisms that are essential for normal and abnormal development.