Abstract: FR-PO0769
Identification of a Novel Tropomyosin Isoform Linked to Sarcomere-Like Structure in Injured Podocytes
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
- Parra, Karla, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Jiang, Shumeng, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Langner, Ewa, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Qu, Chengqing, Washington University in St Louis School of Medicine, St. Louis, Missouri, United States
- Genin, Guy M., Washington University in St Louis School of Medicine, St. Louis, Missouri, United States
- Miner, Jeffrey H., Washington University in St Louis School of Medicine, St. Louis, Missouri, United States
- Suleiman, Hani, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
Background
Kidney diseases like focal segmental glomerulosclerosis and Alport syndrome primarily target podocytes—epithelial cells critical for maintaining the kidney's filtration barrier. When podocytes are injured, their intricate foot processes undergo morphological changes, including flattening and retraction, resulting in foot process effacement (FPE). Our previous work demonstrated that podocytes respond to injury by remodeling their actin cytoskeleton into sarcomere-like structures (SLSs), marked by the periodic arrangement of synaptopodin and myosin IIA. This architectural shift suggests a deeper cytoskeletal regulatory mechanism activated under stress. Similar to the skeletal muscle fibers sarcomere counterparts, we hereby propose that Tropomyosins (Tpms)—coiled-coil proteins that bind along actin filaments—play a key role in shaping these responses.
Methods
To identify Tpm isoforms involved in podocyte injury, we performed llumina and PacBio RNA sequencing on isolated glomeruli from four established mouse models of podocyte damage: Cd2ap-/-, Lamb2-/-, Col4a3-/-, and Adriamycin nephropathy. We compared these profiles to healthy glomeruli controls to detect injury-specific Tpm changes. To confirm that a candidate Tpm isoform contributes to SLS formation, we applied ultrastructure expansion microscopy to deparaffinized mouse kidney tissues. Temporary knockdown of Tpm1 and 4 was done using siRNA.
Results
Wild-type glomeruli displayed a Tpm expression pattern markedly different from their injured counterparts. Among the most significantly altered isoforms were Tpm1.7 and Tpm4.2. PacBio sequencing revealed a previously unannotated Tpm-related transcript expressed exclusively in injured glomeruli, pointing to an injury-induced shift in Tpm regulation. Immunostaining of the Tpms in both in vitro and in vivo showed that Tpms are part of the SLSs that appear in the injured glomeruli. Short-term knockdown of Tpm1 or 4 using siRNA did not affect the SLSs in vitro.
Conclusion
Our findings suggest that injury-induced changes in Tpm isoform expression may act as regulators of actin cytoskeletal reorganization in podocytes. These shifts likely contribute to the formation of SLSs and drive the morphological changes underlying FPE.