The Role of Planar Cell Polarity Signals in Shaping Kidney Tubules

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DESCRIPTION (provided by applicant): Formation of renal tubules in both mammals and amphibians requires Wnt pathways. In kidney, aberrant Wnt signaling has been linked to developmental pathologies such as Wilms tumor and cystic diseases, as well as with renal cell carcinoma. Recent studies from our group and others indicate that canonical (?-catenin- mediated) Wnt signaling is essential for induction of nephron development. Additionally, studies suggest that primary cilia are required for a switch from canonical to non-canonical Wnt signaling, and that defects in primary cilia formation or signaling lead to cystogenesis. Varied tissues undergoing morphogenesis employ non-canonical Wnt (PCP: "planar cell polarity") pathways to promote processes including cell polarization and cytoskeletal modulation. Deficiencies in non-canonical Wnt signaling, which contributes to PCP, underlie a number of developmental or later defects, such as polycystic kidney disease and nephronophthisis. Using Xenopus laevis (frog) embryos, supplemented in some contexts with embryos of Danio rerio (zebrafish), this proposal first assesses the roles of non-canonical Wnt PCP components in kidney tubule morphogenesis. Our hypothesis is that the PCP components Daam1, WGEF, Prickle and Strabismus are required for primary cilia formation, which is in turn required for nephric morphogenesis. Xenopus offers experimental advantages including the facile introduction of exogenous constructs to block or activate signaling pathways, rapid development and easy visualization of the forming kidney under the surface ectoderm. Second, using transgenic approaches, we will address in living animals the role of PCP/ non-canonical Wnt signals in shaping and moving cells that are undergoing/ contributing to kidney tubule morphogenesis. Finally, an over-expression screen will be performed to discover new regulators of tubule formation. Overall, this work is novel in assessing the roles of the PCP components in kidney development; in utilizing transgenic approaches in Xenopus laevis to visualize and/ or target kidney development in living embryos; and in performing an unbiased over- expression screen to reveal additional and likely novel components involved in kidney tubulogenesis. In sum, we will enhance our understanding of kidney morphogenesis, which is likely to be relevant to obtaining insights on later pathologies that arise in humans.