Abstract: TH-PO0310
Characterization of Synaptopodin "Ultra Long" (Synpo-UL): A Novel Isoform in Podocytes
Session Information
- Glomerular Diseases: Cell Biology
October 22, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- 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 School of Medicine, St. Louis, Missouri, United States
- Suleiman, Hani, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
Background
Synaptopodin (Synpo) is a critical actin-binding protein in podocytes, essential for forming sarcomere-like structures (SLS) with myosin IIA to maintain foot process architecture after injury. While the classic long (Synpo-L) and short (Synpo-S) isoforms are recognized, the full spectrum of Synpo alternative transcripts remains incompletely understood. This study characterizes a previously unidentified isoform, Synaptopodin Ultra Long (Synpo-UL), utilizing a newly developed domain-specific antibody and new mouse models.
Methods
Transcript architecture was determined via nested RT-PCR and Sanger sequencing. To interrogate the specific function and localization of this variant, we generated a novel, highly specific anti-Synpo-UL N-terminus antibody and produced Synpo-UL knockout (UL -/-) CRISPR mice. Tissue specificity and protein expression were evaluated by Western blotting across glomeruli, brain tissue, and transfected cell lines. Spatial distribution and protein domain validation were assessed via immunostaining of WT, Synpo-S/L -/-, and UL-/- kidney cryosections, as well as in cultured primary podocytes.
Results
Sequencing revealed that the Synpo-UL transcript is generated through a unique promoter for “exon 0” and alternative splicing, skipping exon 1, directly linking exon 0 to exon 2. Structurally, this translates to an extended N-terminal domain upstream of the Synpo-S/L N-terminus. Utilizing our novel UL-specific antibody, Western blotting demonstrated robust expression in WT glomeruli, whereas RT-PCR shows UL’s absence in brain. IF staining in WT vs. UL-/- and global Synpo-L/S-/- cryosections validated both the successful targeted ablation of the isoform in our novel mouse model and the high fidelity of the new antibody. Furthermore, Synpo-UL failed to react with C-terminal antibodies, confirming it lacks the C-terminus encoded by exon 3.
Conclusion
We have identified Synpo-UL as a novel, glomerular isoform of Synpo. The successful generation of a novel UL-specific antibody and a targeted UL -/- mouse model provides definitive evidence of its unique structural architecture (an extended N-terminus and truncated C-terminus) and spatial segregation. These newly developed tools establish a critical foundation for uncovering the highly specialized role Synpo-UL plays in maintaining podocyte SLS and overall glomerular filtration barrier integrity.
Acknowledgment
We thank Jennifer Richardson for mouse genotyping This work was funded in part by the NSF through the NSF Science and Technology Center for Engineering Mechanobiology (CMMI 1548571), and by the NIH through grants R01DK131177 and R01DK141178.
Funding
- NIDDK Support