| Summary: | The glomerular ultrafiltration barrier contains highly terminally differentiated podocytes with major processes and foot processes interlinked by ultrathin slit diaphragms. A number of molecules that are associated with nephrosis and podocyte damage have been described and these discoveries have given insight into the mechanisms that lead to podocyte injury. One of these molecules is CD2-associated protein (CD2AP), which is a crucial protein for slit- diaphragm assembly and function. In spite of the fact that CD2AP knockout causes nephrotic syndrome in mice and the heterozygous +/- mouse is prone to proteinuria, little is known about the relevance of this molecule in human renal pathology. In this thesis I studied the effect of a disease causing CD2AP mutation on the human podocyte phenotype. I identified the dramatic effects of the CD2AP mutation on the morphology of the cells and on the expression of mesenchymal, epithelial and other markers. I found that in contrast to wild type podocytes, CD2AP mutant podocytes acquired the characteristics of dedifferentiated cells. I compared the phenotypic characteristics of the CD2AP mutant podocytes with podocytes carrying mutations in the transcription factor WTI which is essential for normal nephrogenesis. Surprisingly, this study detected a similar de-differentiated phenotype in the CD2AP mutant podocytes to that seen in podocytes carrying a mutation in the WTl gene. In view of these phenotypic similarities I studied whether there is a functional link between CD2AP and WTI which confer these similarities in cellular phenotype. CD2AP is also known to bind to WTIP (WTl interacting protein), a molecule that binds WTI and can shuttle to the nucleus during podocyte injury. In this study, I found that WTIP might provide the functional link between CD2AP and WTl. In addition, in this study I have established the first conditionally immortalized human glomerular mesangial cell line with unique migratory properties, which will be an important adjunct in studies of representative glomerular cells, as well as in eo-culture studies. Overall this thesis demonstrates that there are clear implications for a novel role for CD2AP in the development and progression of glomerular disease. This thesis also discusses a novel conditionally immortalized human mesangial cell line that represents a new tool for the study of human mesangial cell biology in vitro.
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