Abstract: FR-PO251
Unbiased RNA-Sequencing Analysis of PKD2-/- Proximal Tubular Epithelial Cells Reveals Stabilization of Primary Cilia by Polycystin-2
Session Information
- Genetic Diseases of the Kidneys: Cystic - II
November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Genetic Diseases of the Kidneys
- 1101 Genetic Diseases of the Kidneys: Cystic
Authors
- Vishy, Courtney E., University of Washington, Seattle, Washington, United States
- Freedman, Benjamin S., University of Washington, Seattle, Washington, United States
Background
Polycystic kidney disease (PKD) is commonly caused by loss of function mutations in PKD2, encoding the transmembrane protein polycystin-2 (PC2). PC2 is primarily an ER-resident protein, with a smaller pool localizing to the primary cilium. However, whether and how PC2 affects primary cilium structure and function remains unclear. To complement animal and organoid models of PKD, cell biology models and unbiased approaches are needed to clarify the mechanistic role of PC2 at the primary cilium and develop targeted therapeutics.
Methods
CRISPR-Cas9 was applied to generate 5 isogenic pairs of PKD2-/- and control porcine proximal tubular epithelial cells. 8 biological replicates per genotype were subjected to bulk RNA-sequencing. Gene-ontology (GO) enrichment and differential expression analyses were performed. Transcript abundance of select genes was measured by qPCR and protein abundance by immunoblot. Primary cilia morphology and cellular attachment were visualized by time-course immunofluorescence microscopy. PKD2-/- hPSC-derived kidney organoids were treated with a the HDAC6 inhibitor tubacin across a range of doses and monitored for cyst formation, live/dead staining, and LDH release toxicity assay.
Results
GO term analysis yielded cilium organization as the most downregulated and mitotic cell cycle as the most upregulated. In PKD2-/- cells, IFT88 had decreased abundance, while the cell cycle associated α-tubulin deacetylase HDAC6 had increased abundance. Upon dissociation and replating, PKD2-/- cells showed accelerated ciliary disassembly followed by delayed ciliary assembly. Enhanced cell cycle progression occurred only upon cellular dissociation after an initial delay in cellular attachment. Pharmacological inhibition of HDAC6 reduced the number of cysts formed and cyst area in PKD2-/- organoids even at low doses and without detectable toxicity.
Conclusion
PC2 stabilizes cilia after cell dissociation, which promotes cell attachment and inhibits cell cycle progression. These phenotypes are transient and not observed at steady state, possibly explaining why they have not been noticed previously. The isogenic cell biology model presented here thus provides new insight into the dynamics of the polycystin proteins and molecular phenotypes associated with PKD suggesting a new treatment approach to inhibit PKD cystogenesis.
Funding
- NIDDK Support