Abstract: FR-PO0791
Spontaneous Podocyte Injury and Progressive Proteinuria in LifeAct Mice
Session Information
- Glomerular Diseases: Cell Homeostasis and Novel Injury Mechanisms
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Langner, Ewa, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Qu, Chengqing, Washington University in St Louis, St. Louis, Missouri, United States
- Jiang, Shumeng, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Genin, Guy M., Washington University in St Louis, St. Louis, Missouri, United States
- Miner, Jeffrey H., Washington University in St Louis, St. Louis, Missouri, United States
- Suleiman, Hani, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
Background
Proteinuric kidney disease and podocyte injury are usually accompanied by foot process effacement, a major reorganization of podocyte actin cytoskeleton. Understanding podocytes’ cytoskeletal network and the mechanobiological principles that preserve podocyte unique morphology are necessary to develop effective treatments for glomerular diseases. LifeAct is a 17-amino acid peptide used to specifically label filamentous actin (F-actin). Transgenic LifeAct mice serve as a useful tool to study actin dynamics in vivo.
Methods
To assess the podocyte actin dynamics, we used LifeAct-mRFP transgenic mice that express LifeAct fused to monomeric red fluorescence protein (mRFP) under the ubiquitous CAG promotor. We crossed LifeAct-mRFP mice with Col4a3-/-, a murine model of Alport Syndrome. Proteinuria levels were estimated as urinary albumin to creatinine ratio. Kidney morphology was assessed by H&E and PAS staining. Foot-process effacement (FPE) was analyzed with transmission electron microscopy. Changes in the cytoskeleton composition were assessed by immunofluorescence staining and super-resolution microscopy. Sarcomere-like structures (SLSs) were detected by synaptopodin and myosin IIA staining.
Results
While LifeAct-mRFP mice are born with no overt phenotype, these mice develop progressive proteinuria and glomerular sclerosis in adulthood. These mice show spontaneous podocyte injury marked by FPE, SLSs formation, and gradual podocyte loss as the mice age. Interestingly, the SLS appear less organized, yet myosin IIA levels did not change. Crossing the Col4a3-/- animals with LifeAct-mRFP mice exacerbated the Alport phenotype, presenting increased proteinuria and decreased lifespan of Alport mice. Importantly, genome sequencing analyses showed that the LifeAct transgene is integrated into an intron and does not disrupt any gene coding sequence.
Conclusion
Our findings demonstrate that the expression of LifeAct-mRFP under the ubiquitous CAG promoter in mice presents with proteinuria and podocyte injury, suggesting that it affects podocytes' actin dynamics. LifeAct was recently shown to compete with the binding of myosin and cofilin to actin filaments. We anticipate that the observed dysfunctional SLSs formation in LifeAct-mRFP mice might be caused by disrupted myosin and cofilin binding to F-actin and lead to reported podocyte loss.
Funding
- NIDDK Support