Discovery and analysis of genes important in kidney development and disease
Milo Rasouly, Hila
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Abnormal kidney development is a relatively prevalent health issue; however, the genetic basis is mostly unknown. The aim of this thesis is to identify genes important in kidney development and disease and to study their molecular functions. We hypothesized that human diseases associated with kidney anomalies can uncover novel genes important in kidney development and disease. The thesis is divided into three independent projects that examined three genes (i.e. Zeb2, Ilk, Robo2) at three stages of mouse kidney development: nephrogenesis, glomerular podocyte, and early ureteric bud outgrowth. In the first project, we identified Zeb2, a gene encoding the zinc finger E-box binding homeobox 2 transcription factor that is mutated in the Mowat Wilson syndrome, as a novel gene important in nephrogenesis. Zeb2 conditional knockout mice (Zeb2 cKO) develop glomerulocystic kidney disease with many atubular glomeruli and decreased expression of proximal tubular markers before cyst formation. These data suggest that abnormal nephrogenesis leads to the congenital atubular glomeruli and primary glomerular cysts in the Zeb2 cKO mice. This study implies that ZEB2 is a novel candidate gene for glomerular cystic disease in patients. Additionally we found that Pkd1, the gene mutated in autosomal dominant polycystic kidney disease, is upregulated in non-cystic glomeruli and knockout of one copy of the Pkd1 gene exacerbates the cystic phenotype of the Zeb2 cKO mice. These findings suggest a genetic interaction between Zeb2 and Pkd1 and that Zeb2 might be a novel PKD1 modifier. In the second project, we studied the roles of integrin-linked kinase (ILK) and roundabout 2 (ROBO2) in glomerular podocytes. We found that ILK and ROBO2 form a protein complex, and that loss of Robo2 improves survival and alleviates the podocyte and basement membrane abnormalities seen in Ilk knockout mice. In the third project, using microarray gene expression analysis, we found lower gene expression levels of extracellular matrix proteins during early ureteric bud outgrowth in the Robo2 homozygous knockout embryos as compared to wild type controls. These findings suggest that ROBO2 may regulate extracellular matrix components in the kidney. In conclusion, we found a new role for Zeb2 in nephrogenesis, and identified a novel function of Robo2 in regulating extracellular matrix gene expression in podocytes and during early kidney development.