The requested budget will be used to generate data to finalize our manuscripts, to propose a mechanistic aim 1 and to address additional comments from the reviewers. Specifically, the following preliminary experiments will be covered by this R56: 1) Generation and characterization of high-recombination MADM models using Hprt-cre and UBC-cre mice, 2) Characterization of the Six2-cre and Ksp-cre MADM model, including staining with antibodies for proximal, Loop of Henle, distal and collecting tubule markers to characterize the tubular identify of the cysts, quantification of cyst number and size, and proliferation/senescence of cells in the cysts over time; and 3) We will perform live-imaging of mutant and control cells on developing kidneys induced with TAT-cre and characterize proliferation and cell migration of mutant cells at the inception of cyst development.