title: LDL Receptor-Related Protein 6 Modulates Ret Proto-Oncogene Signaling in Renal Development and Cystic Dysplasia.
abstract: Hypoplastic and/or cystic kidneys have been found in both LDL receptor-related protein 6 (Lrp6)- and β-catenin-mutant mouse embryos, and these proteins are key molecules for Wnt signaling. However, the underlying mechanisms of Lrp6/β-catenin signaling in renal development and cystic formation remain poorly understood. In this study, we found evidence that diminished cell proliferation and increased apoptosis occur before cystic dysplasia in the renal primordia of Lrp6-deficient mouse embryos. The expression of Ret proto-oncogene (Ret), a critical receptor for the growth factor glial cell line-derived neurotrophic factor (GDNF), which is required for early nephrogenesis, was dramatically diminished in the mutant renal primordia. The activities of other representative nephrogenic genes, including Lim1, Pax2, Pax8, GDNF, and Wnt11, were subsequently diminished in the mutant renal primordia. Molecular biology experiments demonstrated that Ret is a novel transcriptional target of Wnt/β-catenin signaling. Wnt agonist lithium promoted Ret expression in vitro and in vivo. Furthermore, Lrp6-knockdown or lithium treatment in vitro led to downregulation or upregulation, respectively, of the phosphorylated mitogen-activated protein kinases 1 and 3, which act downstream of GDNF/Ret signaling. Mice with single and double mutations of Lrp6 and Ret were perinatal lethal and demonstrated gene dosage-dependent effects on the severity of renal hypoplasia during embryogenesis. Taken together, these results suggest that Lrp6-mediated Wnt/β-catenin signaling modulates or interacts with a signaling network consisting of Ret cascades and related nephrogenic factors for renal development, and the disruption of these genes or signaling activities may cause a spectrum of hypoplastic and cystic kidney disorders.
authors.affiliation: Department of Biochemistry and Molecular Medicine and Comprehensive Cancer Center, University of California Davis, School of Medicine, Sacramento, California; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children-Northern California and University of California Davis School of Medicine, Sacramento, California;
authors.forename: Yongping
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Biochemistry and Molecular Medicine and Comprehensive Cancer Center, University of California Davis, School of Medicine, Sacramento, California; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children-Northern California and University of California Davis School of Medicine, Sacramento, California;
authors.forename: Arjun
authors.initials: A
authors.lastname: Stokes
authors.affiliation: Department of Biochemistry and Molecular Medicine and Comprehensive Cancer Center, University of California Davis, School of Medicine, Sacramento, California;
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Duan
authors.affiliation: Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children-Northern California and University of California Davis School of Medicine, Sacramento, California;
authors.forename: Jordan
authors.initials: J
authors.lastname: Hui
authors.affiliation: Cambridge-Suda Genome Resource Center, Soochow University, Suzhou, China;
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana.
authors.forename: YiPing
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Biochemistry and Molecular Medicine and Comprehensive Cancer Center, University of California Davis, School of Medicine, Sacramento, California;
authors.forename: Hong-Wu
authors.initials: HW
authors.lastname: Chen
authors.affiliation: Department of Biochemistry and Molecular Medicine and Comprehensive Cancer Center, University of California Davis, School of Medicine, Sacramento, California;
authors.forename: Kit
authors.initials: K
authors.lastname: Lam
authors.affiliation: Department of Biochemistry and Molecular Medicine and Comprehensive Cancer Center, University of California Davis, School of Medicine, Sacramento, California; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children-Northern California and University of California Davis School of Medicine, Sacramento, California; cjzhou@ucdavis.edu.
authors.forename: Chengji J
authors.initials: CJ
authors.lastname: Zhou
mesh_terms: D000818:Animals; D007668:Kidney / Q000254:growth & development*; D060488:Low Density Lipoprotein Receptor-Related Protein-6 / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D021782:Multicystic Dysplastic Kidney / Q000209:etiology* / Q000235:genetics; D051096:Proto-Oncogene Proteins c-ret / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D060488:Low Density Lipoprotein Receptor-Related Protein-6; D051096:Proto-Oncogene Proteins c-ret
keywords: cell signaling; cystic kidney; renal agenesis