Sayoko Fujimura, Qing Jiang, Chiyoko Kobayashi, Ryuichi Nishinakamura. (2010) Notch2 activation in the embryonic kidney depletes nephron progenitors. J. Am. Soc. Nephrol. 21: 803-810.
Successive activation of Wnt4 and Notch2 generated nephrons from the metanephric mesenchyme. Mesenchymal-to-epithelial transition requires Wnt4, and normal development of the proximal nephron requires Notch2. It is unknown, however, whether Notch2 dictates the fate of the proximal nephron directly. Here, we generated a mutant strain of mice with activated Notch2 in Six2-containing nephron progenitor cells of the metanephric mesenchyme. Notch2 activation did not skew the cell fate toward the cell fate toward the proximal nephron but resulted in severe kidney dysgenesis and depletion of Six2-positive progenitors (Fig. 1). We observed ectopic expression of Wnt4 and premature tubule formation, similar to the phenotype of Six2-deficient mice. Activation of Notch2 in the progenitor cells suppressed Pax2, an upstream regulator of Six2, possibly through Hesr genes. These data suggest that a positive feedback loop exists between Notch2 and Wnt4, and that Notch2 stabilizes, rather than dictates, nephron fate by shutting down the maintenance of undifferentiated progenitor cells, thereby depleting this population (Fig. 2). This paper is featured in the cover and highlights of the May issue of the Journal of American Society of Nephrology (Fig. 3).
Figure 1. Overexpression of Notch2 in embryonic nephron progenitors leads to severe kidney dysgenesis. Kidneys in newborn mice. k: kidney; t: testis; b: bladder; a: adrenal gland.
Figure 2. A Notch2-Wnt4 positive feedback loop stabilizes the differentiated state.
Figure 3. The cover of the Journal of American Society of Nephrology. The kidney at the embryonic day 14.5.
