The role of talin splice variants in health and disease

Talin is a protein crucial to the function of cell-matrix focal adhesions, which allows a cell to interact with its environment. In this thesis, I show that alternate splicing of talin, whether by mutation or by cassette exon splicing contributes to the pathogenicity of multiple diseases, by affecting the form and function of focal adhesion complexes. Two variations in alternate talin splicing were examined, the loss of exon 54 and the insertion of novel exon 17b. My work, along with the work of my collaborators on both splice variants, has revealed that the novel talin exon 17b, is highly expressed in many cancers, and alters the structure of the R1 and R2 rod domains of talin, resulting in focal adhesions that display altered force loading and mechano-sensing properties. The data presented here suggests that exon 17b is expressed by cancers to gain drug resistance and evade the immune system. I also propose a function for exon 17b in non-cancerous human cells, that the exon is spliced into talin 1 to reduce the formation of excess scar tissue by deactivating myofibroblasts. I have also worked with collaborators who have discovered a family who suffer from systemic capillary leak syndrome, due to an autosomal dominant mutation, causing an alternate splicing event of talin 1. My work in analysing the impact of exon 54 removal on the R13 rod domain of talin, has shown the resulting deletion creates an over-active talin that ‘leeches’ vinculin from surrounding cell-cell adherens junctions. Preventing vascular tissue reorganisation, resulting in rapid loss of fluid from the vascular system into surrounding tissue. The thesis also discusses my work with a research group from Bordeaux who have developed an artificial, bacterially expressed antibody alternative. Using nuclear magnetic resonance, I show that these ‘intrabodies’ bind their targets with high specificity and affinity, showing potential as a replacement for monoclonal antibodies.