Disease Pathways in Podocyte Injury - Approaching FSGS by single-nucleus RNA-sequencing

• Applicants: Dr. Martin Kann; Professor Dr. Roman-Ulrich Müller
• Subject Area: Nephrology
• Term: from 2020 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 433158430

Podocytes are the epithelial cell-type of the renal filtration unit – the glomerulus – and podocyte disease leads to proteinuric and progressive kidney disease. The common and unifying glomerular phenotype of progressive podocyte damage and loss is focal and segmental glomerulosclerosis (FSGS). FSGS is a histologic pattern resulting from various heterogeneous and progressive disease processes that involve podocyte pathology. A hallmark of FSGS is its heterogeneity, in particular the simultaneous occurrence of various cell populations reflecting different degrees of cell damage and disease-specific molecular signatures within the same tissue. This situation is comparable to the heterogeneity of malignant tumor tissues, which may simultaneously contain tumor stem cells, differentiated and de-differentiating tumor cells, healthy cells of the host tissue, various immune cells, as well as tumor cells responding to the attacking immune system. The underlying cause of FSGS has remained elusive and the different disease entities leading to this histopathological pattern of injury are not clear. In tumor biology, single-cell and single-nucleus RNA-sequencing (scRNAseq, snRNAseq) have recently proven as powerful techniques to delineate cell populations within tumors, characterize the immune response, and understand mechanisms of resistance to tumor therapy. We have recently employed this technique to elucidate the cellular composition of the renal glomerulus (Karaiskos et al. 2018) and will now use snRNAseq to elucidate cell-specific transcriptional patterns during early pathogenesis of FSGS. Due to cellular heterogenity in the response to disease-causing stimuli in FSGS snRNAseq holds the promise to add much to the current knowledge on this disease. To reach this goal, we will employ 3 different mouse models of FSGS (one genetic model (Wt1hetdel), one toxic model (adriamycin) and one transgenic mouse model employing the podocyte-specific expression of the diphtheria toxin receptor. The data obtained will be combined with available multilayered omics-data (bulkRNAseq, proteomics, phospho-proteomics and metabolomics) to take the next towards identifying the cell biological changes underlying the pathogenesis of FSGS and to decipher cell-type specific responses in the glomerulus.

• DFG Programme: Research Grants
• Co-Investigators: Dr. Janine Altmüller; Professor Dr. Andreas Beyer