Why detailed model gene studies in higher eukaryotes are still necessary.

Alterations in gene expression programmes are controlled by sequence-specific DNA-binding proteins that interact with the epigenetic regulatory machinery. The sum of such processes comprises a gene regulatory network and differentiation processes involve transitions between such networks. However, while great progress has been made to identify network components, this list is not complete, and we still do not fully understand how they work together. In this article, I argue that one reason for this lack of knowledge is the fact that we still do not understand what controls the cell stage and cell state-specific regulation of individual genes and review examples highlighting this notion.