Canonical Wnt transcriptional complexes are essential for induction of nephrogenesis but not maintenance or proliferation of nephron progenitors

Abstract

Wnt regulated transcriptional programs are associated with both the maintenance of mammalian nephron progenitor cells (NPC) and their induction, initiating the process of nephrogenesis. How opposing transcriptional roles are regulated remain unclear. Using anin vitromodel replicatingin vivoevents, we examined the requirement for canonical Wnt transcriptional complexes in NPC regulation. In canonical transcription, Lef/Tcf DNA binding proteins associate the transcriptional co-activator β-catenin. Wnt signaling is readily substituted by CHIR99021, a small molecule antagonist of glycogen synthase kinase-3β (GSK3β). GSK3β inhibition blocks Gskβ-dependent turnover of β-catenin, enabling formation of Lef/Tcf/β-catenin transcriptional complexes, and enhancer-mediated transcriptional activation. Removal of β-catenin activity from NPCs under cell expansion conditions (low CHIR) demonstrated a non-transcriptional role for β-catenin in the CHIR-dependent proliferation of NPCs. In contrast, CHIR-mediated induction of nephrogenesis, on switching from low to high CHIR, was dependent on Lef/Tcf and β-catenin transcriptional activity. These studies point to a non-transcriptional mechanism for β-catenin in regulation of NPCs, and potentially other stem progenitor cell types. Further, analysis of the β-catenin-directed transcriptional response provides new insight into induction of nephrogenesis.Summary StatementThe study provides a mechanistic understanding of Wnt/ β-catenin activity in self-renewal and differentiation of mammalian nephron progenitors.

Nephron progenitors rhythmically alternate between renewal and differentiation phases that synchronize with kidney branching morphogenesis

“…These data indicate that the basal YAP state in nephron progenitor organoids permits Wnt-induced differentiation, while YAP activation converts the same Wnt signal into a renewal signal when the two temporally overlap. This interaction may relate to the paradoxical requirement of Wnt/β-catenin for both nephron progenitor renewal and differentiation 88 , namely that a rhythmic YAP signaling context could enable the niche to alternately favor each state given a consistent Wnt/β-catenin input in vivo .…”

Generation of human-pig chimeric renal organoids using iPSC technology

“…2d). KR5_Mat provides a strong Wnt signal in the early stages of maturation culture, and it has been reported that excessive Wnt signal not only accelerates nephron development but also biases differentiation towards the distal tubules [35][36][37]. Furthermore, Chen et al demonstrated through experiments involving the injection of embryonic mouse NPCs into cap mesenchyme of mouse fetal kidneys at different developmental stages, the developmental timing difference significantly influences the survival and differentiation of injected NPCs [38].…”