for R-56 related to 1R01DK139111-0 The goal of this project, “Early podocyte injury in collagen IV nephropathy”, is to understand the earliest events in podocyte injury in Collagen IV nephropathies. The basic hypothesis is that processing of mutant collagen IV proteins injures podocytes at early stages of development, ultimately leading to Chronic Kidney Disease and renal failure (ESRD). The podocyte cell-specific mechanisms of early injury process are not fully understood, but if identified and mitigated early, could defer renal injury and progression to ESRD. Our approach is to use transcriptomic data from extensively phenotyped mouse models mapped to a human database of proteinuric kidney disease (NEPTUNE FSGS and COL4 mutations) to identify similarities and differences and use the model systems to identify the earliest possible points for intervention in Col IV nephropathies. Understanding of how Collagen IV mutations initiate and drive podocyte injury will also be critical in understanding other human glomerular diseases including in human FSGS patients, many of whom have Collagen IV mutations. Our published and preliminary data from WT and Col4a3-/- mice, and accompanying conditionally immortalized podocytes demonstrate: 1. Suppression of the Alport renal phenotype including early podocyte injury and loss by mitigation of the Unfolded Protein Response (UPR) with Tauro-Urso-DeoxyCholic Acid (TUDCA), 2. Reduced expression of WNK1 occurs early in Alport nephropathy, 3. Inhibition of WNK1 disrupts podocyte and glomerular architecture, 4. Activation of WNK1 suppresses the Alport phenotype in 4 month Col4a3-/- glomeruli and cultured podocytes, 5. Podocyte injury begins before proteinuria, and renal parenchymal injury begins with its onset and loss of approximately 40% of podocytes, 6. Bulk RNAseq shows that increased expression of cytokines and chemokines coincides with the onset of proteinuria, 7. A list of podocyte enriched genes from NEPTUNE human FSGS single cell data was mapped to mouse orthologs in our mouse bulk-RNA seq data to identify 60 podocyte enriched genes whose magnitude of change was reduced or direction of change was reversed by TUDCA. 8. This group of genes was similar in nature and behavior to gene changes reported in studies of anti-miR21/ACEI treatment of Svj129 Col4a3-/- mice where the Alport phenotype was also suppressed. This group of podocyte enriched genes represents a focused target for reversing or mitigating podocyte injury in these diseases. We emphasize two distinct areas of the application: 1) The importance of WNK1 signaling in podocyte cytoskeletal structure and glomerular biology in Alport syndrome 2) The validity of mapping mouse to human transcriptomic data. Our current goal is to generate additional data to resolve these questions. We will expand our preliminary and published data demonstrating that WNK1 has essential and specific roles in glomerular and podocyte structure, and that its level of expression d...