Summary After birth, the kidney continues to develop for weeks in mice, and for months to years in humans. During this period, the post-natal kidney is undergoing growth and maturation, which requires dynamic changes in gene expression, metabolism, and physiological functions, and is susceptible to insults causing permanent morphological changes and functional adaptation. Post-natal growth and maturation of the kidney play an important role in developmentally programmed diseases. For e.g., children born with a moderate reduction in nephron number may be more sensitive to metabolic stresses, such as high fat or high salt diet, obesity, and renal injury from hypoxia or nephrotoxins. Many studies have generated single cell datasets for fetal and adult mouse kidney. However, in spite of the important role of post-natal insults in development and progression of CKD, post-natal maturation of the kidney has not been comprehensively investigated at the molecular level using state-of-the-art technologies. The lack of a reference atlas for this critical developmental period limits our ability to investigate alterations in cell states and diversity in models of pediatric kidney disease. Glomerular diseases, including nephrotic syndrome, represent an important cause of childhood kidney disease. Focal and segmental glomerulosclerosis (FSGS) is a diagnosis that is increasing in frequency, is often recurrent and treatment resistant, and leads to end stage kidney disease. Secondary glomerulosclerosis and albuminuria develop in common non-glomerular diseases affecting children, such as CAKUT, and portend a higher risk of progression to end stage kidney failure. Currently, there are limited therapeutic options to treat these disorders and a pressing need to better understand disease mechanisms. One of the major mechanisms by which cells respond to stress or injury is by utilizing the chromatin modifying machinery to reprogram gene regulatory networks. We developed a novel mouse model of FSGS due to loss of function of metastases associated protein 2 (Mta2), a core component of the NuRD chromatin remodeling complex. These mutant mice represent an excellent model to investigate how clinically silent defects in nephron endowment and altered cell differentiation can manifest as FSGS in late adolescence/early adulthood. In this proposal we will generate an integrated single cell and spatial transcriptomics mouse atlas (pKidCAP) at post-natal timepoints that coincide with major physiological and developmental changes in the kidney. We will determine the evolution of cell diversity, spatial localization, single cell gene expression signatures and chromatin accessibility states in the developing post-natal kidney in healthy and FSGS tissue. We will apply ChIP-seq and epigenomic editing to test the hypothesis that de-repression of Jun/AP-1 targets in Mta2 mutants promotes inflammation, cell senescence and lipotoxicity. Integration of these datasets with the human pKidCA...