Biology subjects

Watnick, T. J.

Publications and source records attributed to Watnick, T. J..

3 recordsLinked to original sources

bioRxiv2025

Extra-ciliary role for polycystins in regulation of Ezrin and renal tubular morphology

Full understanding of the functions of the polycystin proteins, PC1 and PC2, in renal epithelial cells is obscured by signaling complexity and renal injury that occurs in Autosomal Dominant Polycystic Kidney Disease (ADPKD). The polycystins likely function as a complex in the primary cilium, yet previous work hinted at a critical role for PC1 function outside of the primary cilium (extra-ciliary) during tubule development. Here, we investigate an extra-ciliary role for the polycystins in regulating renal cell and tubular morphology. First, we found acute loss of polycystins significantly increased the circularity of renal epithelial cells and tubuloids grown in 3D culture. Next, we demonstrated that both PC1 and PC2 can immunoprecipitate Ezrin, an ERM protein important for apical compartment shape. In human ADPKD renal cystic tissue, and after acute inducible knockout of Pkd1 or Pkd2, we found that Ezrin protein abundance is significantly reduced, with the remaining Ezrin protein mis-localized. Immunofluorescence in 2D cells and 3D tubuloids suggested acute polycystin loss specifically reduced the active form of Ezrin at the apical surface, leaving inactive Ezrin colocalized with ZO1 in the cell junctions. A specific ERM phosphorylation inhibitor, NSC668394, phenocopied the increased circularity observed in the Pkd1 knockout spheroids, as did inhibition of PKC activity, implicating the polycystin complex in regulating Ezrin phosphorylation. Our data strongly support a role for the polycystin complex in regulating renal cell and tubular shape via interactions with the ERM protein Ezrin, interactions that do not require trafficking to the primary cilium.

cell biology↗

bioRxiv2024

Multi-omics profiling of mouse polycystic kidney disease progression at a single cell resolution

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease and causes significant morbidity, ultimately leading to end-stage kidney disease. PKD pathogenesis is characterized by complex and dynamic alterations in multiple cell types during disease progression, hampering a deeper understanding of disease mechanism and the development of therapeutic approaches. Here, we generate a single nucleus multimodal atlas of an orthologous mouse PKD model at early, mid and late timepoints, consisting of 125,434 single-nucleus transcriptomic and epigenetic multiomes. We catalogue differentially expressed genes and activated epigenetic regions in each cell type during PKD progression, characterizing cell-type-specific responses to Pkd1 deletion. We describe heterogeneous, atypical collecting duct cells as well as proximal tubular cells that constitute cyst epithelia in PKD. The transcriptional regulation of the cyst lining cell marker GPRC5A is conserved between mouse and human PKD cystic epithelia, suggesting shared gene regulatory pathways. Our single nucleus multiomic analysis of mouse PKD provides a foundation to understand the earliest changes molecular deregulation in a mouse model of PKD at a single-cell resolution.

genomics↗

bioRxiv2021

Defining cellular complexity in human autosomal dominant polycystic kidney disease by multimodal single cell analysis

Autosomal dominant polycystic kidney disease (ADPKD) is the leading genetic cause of end stage renal disease and is characterized by the formation and progressive expansion of kidney cysts. Most ADPKD cases arise from mutations in either the PKD1 or PKD2 gene but the precise downstream signaling pathways driving cyst growth are not well understood, and relatively few studies investigate human cystic kidney due to sample scarcity. In order to better understand the cell types and states driving human ADPKD progression, we analyzed eight ADPKD and five healthy human kidney samples, generating a single cell multiomic atlas consisting of ~100,000 single nucleus transcriptomes and ~50,000 single nucleus epigenomes. The integrated datasets identified 11 primary cell clusters including most epithelial cell types as well as large endothelial and fibroblast cell clusters. Proximal tubular cells from ADPKD kidneys expressed a failed repair transcriptomic signature characterized by profibrotic and proinflammatory transcripts. We identified the G protein-coupled receptor GPRC5A as specifically upregulated in cyst lining cells derived from collecting duct. The principal cell subpopulation enriched for GPRC5A expression also exhibited increased transcription factor binding motif availability for NF-{kappa}B, TEAD, CREB and retinoic acid receptor families and we identified and validated a distal enhancer regulating GPRC5A expression containing these transcription factor binding motifs. This study establishes the single cell transcriptomic and epigenomic landscape of ADPKD, revealing previously unrecognized cellular heterogeneity.

genomics↗