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Stromal beta-catenin activation impacts nephron progenitor differentiation in the developing kidney and may contribute to Wilms tumor

ABSTRACT: Wilms tumor (WT) morphologically resembles the embryonic kidney, consisting of blastema, epithelial, and stromal components, suggesting tumors arise from the dysregulation of normal development. Activation of beta-catenin is observed in a significant proportion of human WTs; however, much remains to be understood about how it contributes to tumorigenesis. While activating beta-catenin mutations are observed in both blastema and stromal components of human WT, current models assume that activation in the blastemal lineage is causal. Paradoxically, studies performed in mice suggest that activation of b-catenin in this lineage results in loss of nephron progenitor cell (NPC) renewal, a phenotype opposite to WT. Here, we show that activation of beta-catenin in the stromal lineage acts non-autonomously, resulting in expansion of NPCs and an inhibition of differentiation. Comparisons of the transcriptomes of kidneys expressing an activated allele of beta-catenin in the stromal or nephron progenitor cells reveals that human WT more closely resembles the stromal-lineage mutants. These findings suggest that stromal beta-catenin activation results in histological and molecular features of human WT, providing insights into how stroma signaling may play an active role in tumorigenesis.

ORGANISM(S): Mus musculus

PROVIDER: GSE150074 | GEO | 2020/05/08

REPOSITORIES: GEO

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Project description:Wnt/β-catenin signaling is a highly conserved molecular pathway that plays a crucial role in stem/progenitor systems and cancer. β-catenin, the main Wnt pathway effector, has two pools within a cell: one for cell-cell adhesion at the membrane and the other for transcriptional functions in the nucleus. However, the mechanism by which β-catenin mediates both roles remain unclear. The tightly controlled, well characterized system of nephrogenesis is an ideal model to decouple the roles of β-catenin at the membrane and in the nucleus. In kidney development, a delicate balance of nephron progenitor cell self-renewal and differentiation is required for the mesenchymal to epithelial transition (MET) in nephrogenesis and is driven by Wnt/β-catenin signaling. Given an ability to isolate and manipulate large numbers of NPCs in tissue culture, we can dissect the dual nature of β-catenin as a transcriptional activator and component of a cell membrane complex in adhesion. We pioneered a method using CRISPR/Cas9 gene editing to rapidly remove β-catenin, Tcf/Lef factors and simultaneous cadherin genes in primary NPCs. We have characterized the effects of modulating β-catenin and integrated RNA-seq results from β-catenin’s removal with mouse ChIP-seq and mouse single cell RNA -seq data. Functional analysis of β-catenin removal provides strong evidence for β-catenin regulation of NPC proliferation, independent of a direct Lef/Tcf associated transcriptional program. Together these data suggest β-catenin mediates aggregation, the first step in MET, through β-catenin mediated cell adhesion complexes while simultaneous transcriptional activation within these structures initiates the nephrogenic program. The studies provide new insight into the direct transcriptional role of Lef/Tcf/β-catenin complexes associated with the initiation of a nephron forming program. Overall, this study enhances an understanding of the molecular mechanisms underlying kidney development and the dual nature of β-catenin stem/progenitor systems at large.

Project description:Purpose: WNT signaling activation in colorectal cancers (CRCs) occurs mainly through APC inactivation or, more uncommonly, β-catenin activation. Both processes promote β-catenin nuclear accumulation, which transcriptionally up-regulates epithelial-to-mesenchymal transition (EMT)-related genes. Experimental Design: We investigated β-catenin localization, downstream gene expression, and phenotypic alterations in HCT116 cells containing a wild-type (HCT116-WT) or mutant β-catenin allele (HCT116-MT), or parental cells with both WT and mutant alleles (HCT116-P). We then analyzed β-catenin localization and associated phenotypes in CRC tissues. Results: Wild-type β-catenin mainly localized at the cell membrane, whereas mutant showed predominantly nuclear localization; membranous, cytoplasmic, and nuclear localization was observed in HCT116-P cells. Microarray analysis revealed significant down-regulation of Claudin-7 and E-cadherin in HCT116-MT vs. HCT116-WT cells. Claudin-7 was also down-regulated in HCT116-P vs. HCT116-WT cells, although E-cadherin expression was unaffected. Altered expression of cell-cell junction-related molecules led to tight junction (TJ) impairment in HCT116-P, and dual loss of TJs and adherens junctions (AJs) in HCT116-MT. TJ loss increased migration and invasion activities of HCT116-WT, whereas AJ loss was required to further up-regulate these activities in HCT116-P. Immunohistochemistry analysis of 101 stage III CRC tissues revealed high nuclear β-catenin expression (≥30% of tumor cells) in 15 (14.9%) samples, low nuclear expression (1-29%) in 53 (52.5%) samples, and undetectable nuclear expression in 33 (32.6%) samples, with a trend toward more frequent down-regulation of Claudin-7 and E-cadherin, and increased metastasis in CRCs with high vs. low nuclear β-catenin. Conclusions: β-catenin activation and nuclear translocation induce EMT progression by modifying cell-cell junctions, and are associated with aggressive behaviors of CRCs.

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Stromal beta-catenin activation impacts nephron progenitor differentiation in the developing kidney and may contribute to Wilms tumor

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