Wilms tumor 1 (Wt1) mutation reveals mechanisms of cell lineage crosstalk in the developing kidney

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PROJECT SUMMARY/ABSTRACT This NIH Mentored Career Development Award describes a three-year proposal providing the training and mentorship necessary for the candidate to develop into an independent investigator studying the genetic and molecular regulation of kidney development, with a specific focus on how mutations in Wilms tumor 1 (Wt1) affect cell lineage crosstalk in the developing kidney. To accomplish this, the candidate has developed a detailed career development plan integrating the outstanding mentorship and scientific environment at UT Southwestern with focused training in bioinformatics and in-vitro techniques to successfully transition to independence. Wt1, the first gene identified in Wilms tumor, regulates multiple aspects of normal renal development and has been previously shown to play a critical role in nephron progenitor cell (NPC) differentiation. Further examination of mutant kidneys with Wt1 loss-of-function specifically targeting the NPC lineage (Six2cre;Wt1c/c) shows additional effects on the nephrogenic stroma, with an expansion of stromal progenitor cells, disruptions in stromal patterning, and an increase in expression of several stromal markers previously shown to be upregulated in Wilms tumors, leading to the hypothesis that signals from the NPCs and/or early nephron structures non-autonomously regulate stromal development. The testing of this hypothesis will interrogate how NPC-to-stromal crosstalk directs stromal progenitor maintenance and/or differentiation in normal kidney development, which will be accomplished through two proposed aims. In aim 1, experiments utilizing genetically engineered mouse models are directed at determining how signals from nephron lineage derived cells regulate the nephrogenic stroma. To do this, stromal proliferation, apoptosis, and patterning will be examined in mutant mouse models targeting different populations of the nephron lineage (ie: self-renewing NPCs vs. early nephron structures) in comparison to the effects on the stroma identified in Six2cre;Wt1c/c mutant kidneys. Aim 2 will investigate the mechanism(s) of NPC-to-stromal crosstalk, using bioinformatics to identify candidate receptor/ligand interactions and in-vitro assays to functionally validate these pathways by determining if disrupting specific signaling pathways results in stromal defects in control kidneys, and likewise, if restored signaling pathways can rescue normal stromal differentiation in mutant kidney explants. Given that advances in renal development research have significantly contributed to the understanding of Wilms tumor, and vice versa, with the study of Wilms tumor biology leading to advances in developmental nephrology, the aims outlined in this proposal have the potential to further uncover how intricate reciprocal signaling interactions regulate progenitor cell proliferation and/or differentiation in normal kidney development and provide the foundation for future work examining how disruptions in progenitor cell crosstalk between the nephron and stromal lineages may alter the embryonic microenvironment and predispose to the development of Wilms tumor.