Molecular genetics and functional characterization of ciliopathies
Primary cilia are microtubule-based organelles projecting from most epithelial cells in vertebrates, with numerous essential roles in chemo- and mechanosensation. A suite of inherited human conditions are caused by defects in the structure or function of primary cilia, and the study of these so-called ‘ciliopathies’ offers an insight into the roles of cilia in normal development and disease.\ud Meckel-Gruber syndrome (MKS) is the most severe ciliopathy, an embryonic lethal condition affecting multiple organ systems. At the opposite end of the ciliopathy phenotypic spectrum, Leber’s Congenital Amaurosis (LCA) type 5 is a ciliopathy with a phenotype restricted to the retina. These conditions provide excellent models to study the importance of cilia. The work in this project aims to elucidate the function of the primary cilium, by studying the molecular genetics of these ciliopathies, using a candidate gene approach, and by studying the proteins mutated in these diseases.\ud Genetic screening identifies C2CD3 as a possible modifier of multi-organ ciliopathies, and suggests that LCA5 is only involved in retinal ciliopathies. Functional work focuses on three poorly-understood ciliopathy proteins: lebercilin, mutated in LCA; and meckelin and MKS1, mutated in MKS. Live-cell imaging and interaction assays suggest a role for lebercilin in bidirectional intraflagellar transport (IFT). Meckelin is shown to interact with nesprin-2, a nuclear scaffold protein, with potential impacts on basal body positioning and non-canonical Wnt signalling. Studies of MKS1 clearly suggest that defects in the interaction between cilia proteins and the proteasome are associated with deregulation of Wnt signalling, which is causative of the ciliopathy disease state.\ud This work will give insights into gene function and molecular mechanism of disease in complex genetic conditions. The understanding of ciliopathies at the molecular level may result in new therapeutic interventions for such conditions to modify disease progression.