The palate (the roof of the mouth) develops from two halves that fuse together during embryonic development. Currently, we do not completely understand what controls these events, but we do know that the common and distressing birth defect cleft palate results when fusion of the two halves of the palate fails to occur. Patients with cleft palate experience difficulties with eating and speaking, which can be improved to some degree by long-term surgery, dental treatment, and speech therapy; it is therefore essential that we have more information on how genes work together during normal development and how these are affected in cleft palate. The Sonic Hedgehog protein is a key molecule in ensuring that the palate develops normally; however, only a small fraction of proteins acting in response to Sonic Hedgehog has been identified. Recently, methods have been developed that will allow us to identify the complete set of proteins controlled by Sonic Hedgehog. We will use these techniques to dissect the role of Sonic Hedgehog signalling in ensuring that the palate develops correctly thereby preventing cleft palate. To ensure that this research is completed ethically, we will perform these experiments in mice, in which the palate develops in exactly the same way as in humans. In the short-term, this research will help us to understand the processes that underlie normal development of the palate and how these are disrupted in cleft palate. In the longer term, this information will help us to provide improved diagnosis, genetic counselling and treatment to patients and their families who are affected by this distressing condition.