Loss of genome maintenance is linked to mTOR complex 1 signaling and accelerates podocyte damage
Fabian Braun, Amrei M. Mandel, Linda Blomberg, Milagros N. Wong, Georgia Chatzinikolaou, David H. Meyer, Anna Reinelt, Viji Nair, Roman Akbar-Haase, Phillip J. McCown, Fabian Haas, He Chen, Mahdieh Rahmatollahi, Damian Fermin, Robin Ebbestad, Gisela G. Slaats, Tillmann Bork, Christoph Schell, Sybille Koehler, Paul T. Brinkkoetter, Maja T. Lindenmeyer, Clemens D. Cohen, Martin Kann, David Unnersjö-Jess, Wilhelm Bloch, Matthew G. Sampson, Martijn E.T. Dollé, Victor G. Puelles, Matthias Kretzler, George A. Garinis, Tobias B. Huber, Bernhard Schermer, Thomas Benzing, Björn Schumacher, Christine E. Kurschat
Fabian Braun, Amrei M. Mandel, Linda Blomberg, Milagros N. Wong, Georgia Chatzinikolaou, David H. Meyer, Anna Reinelt, Viji Nair, Roman Akbar-Haase, Phillip J. McCown, Fabian Haas, He Chen, Mahdieh Rahmatollahi, Damian Fermin, Robin Ebbestad, Gisela G. Slaats, Tillmann Bork, Christoph Schell, Sybille Koehler, Paul T. Brinkkoetter, Maja T. Lindenmeyer, Clemens D. Cohen, Martin Kann, David Unnersjö-Jess, Wilhelm Bloch, Matthew G. Sampson, Martijn E.T. Dollé, Victor G. Puelles, Matthias Kretzler, George A. Garinis, Tobias B. Huber, Bernhard Schermer, Thomas Benzing, Björn Schumacher, Christine E. Kurschat
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Research Article Aging Cell biology Nephrology

Loss of genome maintenance is linked to mTOR complex 1 signaling and accelerates podocyte damage

Abstract

DNA repair is essential for preserving genome integrity. Podocytes, postmitotic epithelial cells of the kidney filtration unit, bear limited regenerative capacity, yet their survival is indispensable for kidney health. Podocyte loss is a hallmark of the aging process and of many diseases, but the underlying factors remain unclear. We investigated the consequences of DNA damage in a podocyte-specific knockout mouse model for DNA excision repair protein Ercc1 and in cultured podocytes under genomic stress. Furthermore, we characterized DNA damage-related alterations in mouse and human renal tissue of different ages and patients with minimal change disease and focal segmental glomerulosclerosis. Ercc1 knockout resulted in accumulation of DNA damage and ensuing albuminuria and kidney disease. Podocytes reacted to genomic stress by activating mTOR complex 1 (mTORC1) signaling in vitro and in vivo. This was abrogated by inhibiting DNA damage signaling through DNA-dependent protein kinase (DNA-PK) and ataxia teleangiectasia mutated (ATM) kinases, and inhibition of mTORC1 modulated the development of glomerulosclerosis. Perturbed DNA repair gene expression and genomic stress in podocytes were also detected in focal segmental glomerulosclerosis. Beyond that, DNA damage signaling occurred in podocytes of healthy aging mice and humans. We provide evidence that genome maintenance in podocytes is linked to the mTORC1 pathway and is involved in the aging process as well as the development of glomerulosclerosis.

Authors

Fabian Braun, Amrei M. Mandel, Linda Blomberg, Milagros N. Wong, Georgia Chatzinikolaou, David H. Meyer, Anna Reinelt, Viji Nair, Roman Akbar-Haase, Phillip J. McCown, Fabian Haas, He Chen, Mahdieh Rahmatollahi, Damian Fermin, Robin Ebbestad, Gisela G. Slaats, Tillmann Bork, Christoph Schell, Sybille Koehler, Paul T. Brinkkoetter, Maja T. Lindenmeyer, Clemens D. Cohen, Martin Kann, David Unnersjö-Jess, Wilhelm Bloch, Matthew G. Sampson, Martijn E.T. Dollé, Victor G. Puelles, Matthias Kretzler, George A. Garinis, Tobias B. Huber, Bernhard Schermer, Thomas Benzing, Björn Schumacher, Christine E. Kurschat

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Figure 3

DNA damage accumulation in podocytes leads to a shift toward smaller transcripts and activates the mTORC1 pathway.

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DNA damage accumulation in podocytes leads to a shift toward smaller tra...
(A) Volcano plot depicting differentially expressed genes of Ercc1 pko versus control glomeruli. Significantly differentially expressed genes depicted in black, pseudogenes depicted in red. FDR, false discovery rate. (B) Gene length analysis of genes differentially expressed in Ercc1 pko versus control glomeruli. Downregulated genes (blue) are significantly larger than upregulated genes (red). P value: 1.52 × 10–7 (Mann-Whitney U test). (C) Correlation analysis plotting the NES of Kyoto Encyclopedia of Genes and Genomes pathway genes in Tsc2ko versus ctrl kidneys and Ercc1 pko versus ctrl glomeruli. (D) GSEA of differentially expressed genes (upregulation, fold-change ≥ 2) in Ercc1-pko glomeruli classified by the gene rank in the mTORC1 hyperactivation (Tsc2ko) data set. The running enrichment score is shown as a green line. The upregulated genes in Ercc1-pko glomeruli are significantly (adjusted P value: 1.67 × 10–5) more enriched (NES: 1.74) in the genes upregulated upon mTORC1 hyperactivation. (E) Representative immunofluorescence staining of SNP, p-S6RP, and DAPI in sections of 9-week-old Ercc1 ctrl and pko kidneys with quantification of SNP and p-S6RP double-positive cells per glomerulus and per total SNP-positive cells, scale bar indicating 20 μm & 10 μm in zoom (unpaired t test, n = 5, 10 glomeruli per sample). ****P ≤ 0.0001.