Cilia are small 'antennae-like' structures which protrude from the surface of most animal cells. Like antennae, they receive and transduce signals from other cells and their surroundings in order to coordinate appropriate cell behaviours. This is especially important in development, and defects in cilia lead to a range of human developmental diseases called "ciliopathies". These conditions range from severe, lethal conditions that involve complex defects in multiple organs including the brain, to relatively mild and organ-specific conditions such as retinitis pigmentosa, which is a form of hereditary, progressive sight loss. Scientists still do not fully understand how cilia help to control brain and retina development. Although these conditions are individually rare, collectively they are a common cause of morbidity and mortality in babies and young children but remain difficult to diagnose and treat.

This research proposes to identify genes that contribute individually, or within groups (pathways), to the formation of a sub-structure of the cilium called the transition zone. The transition zone at the base of the cilium is thought to function as a type of 'gate', controlling which signal transduction molecules are allowed to enter and exit the cilium. Many of the genes that cause ciliopathies are thought to function in the transition zone and regulate its 'gating' function. To achieve our aims, we will take advantage of recent exciting advances in genetic technology that allow us to evaluate the contribution of every gene to cilia and transition zone formation ("reverse genetics screen"). We are uniquely placed to do this work and the team of investigators have a proven track record of success in this field: we have formed excellent research partnerships with other workers in the field to participate in gene identification studies; we have the appropriate state-of-the-art technology, image analysis tools and experience; and we have already produced and validated large data-sets from existing work that we now wish to exploit more extensively in the present research proposal. We will study key genes ("screen hits") and their contributions to cilia and transition zone formation, and, in particular we will use specialised cell model systems in combination with a versatile animal model (a nematode roundworm).

The identification and characterisation of new genes required for the structure and function of the cilium and the transition zone 'gate' provides a number of major benefits. Firstly, important and often unexpected scientific insights are made into disease processes and into the normal function of the disease gene that can lead to new treatments. Secondly, new ciliary genes often enable accurate genetic testing for patients and families with ciliopathies, which improve diagnosis and genetic counselling. Thirdly, our proposed work has a wider biological relevance because cilia have recently been shown to control metabolism, which may link to neurodegenerative diseases and metabolic disorders such as insulin resistance. Thus, a better understanding of cilium biology may provide opportunities for developing drugs or new treatments to prevent the progression of more common ailments (e.g., diabetes. obesity) that present in some ciliopathy patients. Finally, we expect that our work will provide new insights into how cilia disease proteins are arranged relative to one another within the transition zone, and how this molecular organisation facilitates the gating function of this discrete region of the cilium. This new knowledge will have important implications for molecular 'gates' that exist elsewhere in the cell, and serve to expand the impact of our work to scientists working on related questions.