p53 Regulates Metanephric Development

Abstract

p53 is best known as a tumor suppressor that regulates cell-cycle, differentiation, and apoptosis pathways, but its potential role in embryonic development and organogenesis remains controversial. Here, p53Ϫ/Ϫ embryos bred on C57Bl6 background exhibited a spectrum of congenital abnormalities of the kidney and urinary tract, including ureteric bud (UB) ectopia, double ureters/collecting systems, delayed primary branching of the UB, and hypoplastic metanephroi. We observed ectopic UB outgrowth from the Wolffian duct (WD) in one third of p53 Ϫ/Ϫ embryos. The prevalence of duplex was higher in embryos than in neonates, and ex vivo organ culture suggested that ectopic ureters can regress over time, leaving behind a dysplastic pole ("segmental dysgenesis"). Transgenic expression of dominant negative p53 or conditional inactivation of p53 in the UB but not in the metanephric mesenchyme lineage recapitulated the duplex phenotype. Mechanistically, p53 inactivation in the WD associated with enhanced sensitivity to glial cell line-derived neurotrophic factor (GDNF)-induced ectopic budding and potentiated phosphatidylinositol-3 kinase activation by GDNF in UB cells. Unlike several other models of UB ectopia, hypersensitivity of p53 Ϫ/Ϫ WD to GDNF is not accompanied by reduced Sprouty-1 or anterior expansion of the GDNF domain. In summary, our data lend support for a restrictive role for p53 activity in UB outgrowth from the WD. Organogenesis is dependent on a multitude of growth factors, signaling molecules, and transcription factors that temporally and spatially define a developmental program. Metanephric development is dependent on formation of the Wolffian duct (WD) and the adjacent metanephric mesenchyme (MM) from the intermediate mesoderm. In mice, the ureteric bud (UB) develops at embryonic day 10.5 (E10.5) from the caudal end of the WD. Inductive interactions between the UB and the MM ensure cell survival and subsequent onset of metanephrogenesis. Emergence of the UB from a specific site in the WD adjacent to the MM is controlled by the glial cell line-derived neurotrophic factor (GDNF)-cRet signaling pathway. 1-6 GDNF is a growth factor that is secreted by the MM and binds to its receptor c-Ret and co-receptor GFR␣1 that are expressed along the WD and UB tips. Stimulation of the GDNF-cRet pathway results in cell proliferation and chemotaxis. 7,8 After the initial broad distribution of the GDNF field along the posterior half of the WD, the GDNF expression domain is progressively restricted to the caudal end of the WD in the immediate vicinity of the site of UB outgrowth 9 -11 ; however, the potential for bud emergence remains along the length of the WD, which continues to express the c-Ret/GFR␣1 receptor/co-receptor. Evidence from mutant mouse models and metanephric organ culture implicates impaired restriction of the GDNF field and the GDNF/c-Ret signaling pathway in ureter duplica-

Histone Deacetylase (HDAC) Activity Is Critical for Embryonic Kidney Gene Expression, Growth, and Differentiation

“…This dose of Gdnf is capable of inducing robust ectopic UB outgrowth and branching (67). However, E13.5 metanephric explants treated with Scriptaid ϩ high dose Gdnf (200 ng/ml) for 24 h failed to show any rescue of growth defect (supplemental Fig.…”

p53 enables metabolic fitness and self-renewal of nephron progenitor cells

“…Immunostaining was performed on 5 µm sections as previously described (Saifudeen et al, 2009). See supplementary material Methods for antibody information and image capture details.…”

“…See supplementary material Methods for antibody information and image capture details. Whole-mount staining was performed on E12.5-13.5 kidneys, as previously described (Saifudeen et al, 2009). Staining for SA-βgal was performed on frozen tissue sections as per the manufacturer's protocol (BioVision).…”

“…Hematoxylin and Eosin staining was performed on 5 µm paraffin-embedded tissue sections, as described previously (Cardiff et al, 2014). Periodic acid-Schiff (PAS) staining was performed as described previously (Saifudeen et al, 2009). …”

“…Reduced nephron number from birth is strongly associated with the development of adult-onset diseases, such as hypertension (Brenner et al, 1988). Because both germline and conditional p53 −/− mice exhibit impaired kidney development, renal hypoplasia and nephron deficit (Saifudeen et al, 2009(Saifudeen et al, , 2012; this study), we sought to determine the physiological impact of p53 loss on blood pressure. Continuous ambulatory blood pressure was monitored for 6 or 7 days in 2-month-old wild-type or mutant mice.…”