Molecular determinants of WNT9b responsiveness in nephron progenitor cells.

Kyle K Dickinson,Paul Goodyer,Nicholas D Hastie,Leah C Hammond,Courtney M Karner,Thomas J Carroll,Rajeev Samant

doi:10.1371/journal.pone.0215139

Abstract

Primed nephron progenitor cells (NPCs) appear in metanephric mesenchyme by E11.5 and differentiate in response to the inductive WNT9b signal from the ureteric bud. However, the NPC WNT-receptor complex is unknown. We obtained M15 cells from E10.5 mesonephric mesenchyme and systematically analyzed components required for canonical WNT9b-responsiveness. When M15 cells were transfected with a β-catenin luciferase reporter plasmid, exposure to recombinant WNT9b resulted in minimal luciferase activity. We then analyzed mRNA-expression of WNT-pathway components and identified Fzd1-6 and Lrp6 transcripts but not Rspo1. When M15 cells were treated with recombinant RSPO1 the response to transfected WNT9b was augmented 4.8-fold. Co-transfection of M15 cells with Fzd5 (but no other Fzd family member) further increased the WNT9b signal to 16.8-fold and siRNA knockdown of Fzd5 reduced the signal by 52%. Knockdown of Lrp6 resulted in 60% WNT9b signal reduction. We confirmed Fzd5, Lrp6 and Rspo1 mRNA expression in CITED1(+) NPCs from E15.5 embryonic mouse kidney. Thus, while many WNT signaling-pathway components are present by E10.5, optimum responsiveness of E11.5 cap mesenchyme requires that NPCs acquire RSPO1, FZD5 and LRP6.

Highlights

The mammalian kidneys are derived from progenitor cells in the embryonic intermediate mesoderm, expressing the transcription factor, OSR1
A committed lineage of nephron progenitor cells (NPCs) emerge from the OSR1(+)/Wilms’ tumor 1 (WT1)(+) intermediate mesoderm as early as embryonic day E7.5 [1]
Around embryonic day E9.0 of mouse development, a lineage of WT1-expressing progenitor cells emerge within the OSR1(+) intermediate mesoderm

Summary

Introduction

The mammalian kidneys are derived from progenitor cells in the embryonic intermediate mesoderm, expressing the transcription factor, OSR1. Fate mapping studies of the embryonic kidney reveal that cells labeled by the Osr promoter at embryonic day E7.5 give rise to all elements of the maturing kidney [1] and Osr knockout mice are anephric [2, 3]. Around E8.5-E9, a subset of OSR1-positive kidney progenitor cells are transformed into polarized epithelia, forming the paired nephric duct structures that elongate down the embryo [4]. Another subset of cells upregulate Wilms’ tumor 1 (WT1) while retaining a mesenchymal phenotype.

Methods

Results

Conclusion