β‐catenin in the kidney stroma modulates pathways and genes that regulate kidney development
Authors: Deacon Erin , Li Anna , Boivin Felix , Dvorkin-Gheva Anna , Cunanan Joanna , Bridgewater Darren 
Published: April 2020

Kidney development is dependent on proper cell communication between the epithelial, mesenchymal and stromal cell lineages. Recent studies by our laboratory, and others, demonstrate that the renal stroma, a population of fibroblast‐like cells, is required for proper collecting duct and nephron formation. However, how the renal stroma communicates with other cell lineages and contributes to proper kidney development is not well known. β‐catenin is a multifunctional protein involved in cell adhesion and transcriptional regulation. Our previous work demonstrated that stromal β‐catenin alters gene expression and the development of the neighbouring epithelial and mesenchymal cells. However, how stromal β‐catenin regulates stromal communication with the other cell lineages is not well established. We hypothesize that stromal β‐catenin modulates genes and signaling pathways that mediate this cellular communication. To address this hypothesis, we generated mouse models with β‐catenin deficiency (β‐catstroma(def)) or overexpression (β‐catstroma(over)) exclusively in the renal stroma. Wild‐type, β‐catstroma(def) and β‐catstroma(over) stromal cells were isolated at E12.5 and E13.5 via fluorescence activated cell sorting (FACS) and were verified by quantitative RT‐PCR to be a pure population of stroma cells. The isolated stromal cells then underwent RNA sequencing (RNA‐seq). The RNA‐seq analysis identified 93 biological processes that were down‐regulated in β‐catstroma(def) cells at E12.5 and E.13.5, and 491 biological processes that were up‐regulated in β‐catstroma(over) cells at E12.5 and E13.5. Interestingly, 76% of the biological pathways that were down‐regulated in the β‐catstroma(def) model at both E12.5 and E13.5 were also up‐regulated in the β‐catstroma(over) at both time points, strongly suggesting that they are regulated by β‐catenin. Of particular interest to our research were the biological processes that were significantly modulated by stromal β‐catenin and are associated with key kidney developmental processes. Specifically, 8 processes linked to Wnt signaling, 16 processes linked to branching morphogenesis, 5 processes linked to nephrogenesis, and 15 processes linked to angiogenesis. Select differentially expressed candidate genes from these biological pathways were validated by immunohistochemistry, immunofluorescence, or in situ hybridization at E12.5 and E13.5. The RNA‐seq also identified numerous novel candidate β‐catenin target genes with undefined roles in kidney development. Novel genes that were most significantly down‐regulated in the β‐catstroma(def) cells and/or up‐regulated in the β‐catstroma(over) at both E12.5 and E13.5 included Emilin2, Atrnl1, Car3, Apcdd1, LHFP, Pitx1, Npy1r, Sttb3, Mctp2, Nkd2, Man1a and Car13. In conclusion, our results support that stromal β‐catenin plays a significant role in regulating multiple major kidney developmental processes, including branching morphogenesis, nephrogenesis and angiogenesis.Support or Funding InformationNSERC, CIHR, KFOC