ABSTRACT
The Wilms' tumor suppressor gene 1 (WT1) encodes a zinc finger transcription factor. Mutation of WT1 in humans leads to Wilms' tumor, a pediatric kidney tumor, or other kidney diseases, such as Denys-Drash and Frasier syndromes. We showed previously that inactivation of WT1 in podocytes of adult mice results in proteinuria, foot process effacement, and glomerulosclerosis. However, the WT1-dependent transcriptional network regulating podocyte development and maintenance in vivo remains unknown. Here, we performed chromatin immunoprecipitation followed by high-throughput sequencing with glomeruli from wild-type mice. Additionally, we performed a cDNA microarray screen on an inducible podocyte-specific WT1 knockout mouse model. By integration of cistromic and transcriptomic analyses, we identified the WT1 targetome in mature podocytes. To further analyze the function and targets of WT1 in podocyte maturation, we used an Nphs2-Cre model, in which WT1 is deleted during podocyte differentiation. These mice display anuria and kidney hemorrhage and die within 24 hours after birth. To address the evolutionary conservation of WT1 targets, we performed functional assays using zebrafish as a model and identified Nphs2, Mafb, and Magi2 as novel WT1 target genes required for podocyte development. Our data also show that both Mafb and Magi2 are required for normal development of the embryonic zebrafish kidney. Collectively, our work provides insights into the transcriptional networks controlled by WT1 and identifies novel WT1 target genes that mediate the function of WT1 in podocyte differentiation and maintenance.
Subject(s)
Cell Differentiation/genetics , Gene Expression Regulation , Genes, Wilms Tumor/physiology , Podocytes/physiology , Repressor Proteins/genetics , WT1 Proteins/genetics , Zebrafish Proteins/genetics , Adaptor Proteins, Signal Transducing/genetics , Animals , Gene Expression Profiling , Guanylate Kinases/genetics , Intracellular Signaling Peptides and Proteins/genetics , MafB Transcription Factor/genetics , Membrane Proteins/genetics , Mice , Mice, Knockout , Nerve Tissue Proteins/genetics , Oligonucleotide Array Sequence Analysis , ZebrafishABSTRACT
Focal segmental glomerulosclerosis (FSGS) is a frequent and severe glomerular disease characterized by destabilization of podocyte foot processes. We report that transgenic expression of the microRNA miR-193a in mice rapidly induces FSGS with extensive podocyte foot process effacement. Mechanistically, miR-193a inhibits the expression of the Wilms' tumor protein (WT1), a transcription factor and master regulator of podocyte differentiation and homeostasis. Decreased expression levels of WT1 lead to downregulation of its target genes PODXL (podocalyxin) and NPHS1 (nephrin), as well as several other genes crucial for the architecture of podocytes, initiating a catastrophic collapse of the entire podocyte-stabilizing system. We found upregulation of miR-193a in isolated glomeruli from individuals with FSGS compared to normal kidneys or individuals with other glomerular diseases. Thus, upregulation of miR-193a provides a new pathogenic mechanism for FSGS and is a potential therapeutic target.
Subject(s)
Glomerulosclerosis, Focal Segmental/etiology , MicroRNAs/physiology , WT1 Proteins/physiology , Animals , Down-Regulation/physiology , Doxycycline/pharmacology , Glomerulosclerosis, Focal Segmental/genetics , Glomerulosclerosis, Focal Segmental/pathology , Humans , Kidney/pathology , Male , Mice , Mice, Knockout , Mice, Transgenic , Podocytes/metabolismABSTRACT
The Wilms' tumor protein Wt1 plays an essential role in mammalian urogenital development. WT1 mutations in humans lead to a variety of disorders, including Wilms' tumor, a pediatric kidney cancer, as well as Frasier and Denys-Drash syndromes. Phenotypic anomalies in Denys-Drash syndrome include pseudohermaphroditism and sex reversal in extreme cases. We have used cDNA microarray analyses on Wt1 knockout mice to identify Wt1-dependent genes involved in sexual development. The gene most dramatically affected by Wt1 inactivation was Amhr2, encoding the anti-Müllerian hormone (Amh) receptor 2. Amhr2 is an essential factor for the regression of the Müllerian duct in males, and mutations in AMHR2 lead to the persistent Müllerian duct syndrome, a rare form of male pseudohermaphroditism. Here we show that Wt1 and Amhr2 are coexpressed during urogenital development and that the Wt1 protein binds to the promoter region of the Amhr2 gene. Inactivation and overexpression of Wt1 in cell lines was followed by immediate changes of Amhr2 expression. The identification of Amhr2 as a Wt1 target provides new insights into the role of Wt1 in sexual differentiation and indicates, in addition to its function in early gonad development and sex determination, a novel function for Wt1, namely, in Müllerian duct regression.
