The Wilms' tumor suppressor Wt1 encodes a transcriptional activator of the class IV POU-domain factor Pou4f2 (Brn-3b).
The Wilms' tumor gene Wt1 encodes a zinc finger protein, which is required for normal formation of the genitourinary system and mesothelial tissues. Our recent findings indicate that Wt1 also plays a critical role in the development of ganglion cells in the vertebrate retina. Here we show that the POU-domain factor Pou4f2 (formerly Brn-3b), which is necessary for retinal ganglion cell survival, is up-regulated in human embryonic kidney (HEK)293 cells with stable Wt1 expression. Consistent with our previous observations of increased Pou4f2 mRNA in stably Wt1-transfeced HEK293 cells [EMBO J. 21 (2002) 1398], endogenous Pou4f2 was also elevated at the protein level in the HEK293 transfectants as well as in U2OS osteosarcoma cells that expressed an inducible Wt1 isoform. Transient co-transfection of a Wt1 expression construct activated a Pou4f2 promoter-reporter construct approximately 4-fold. Stimulation of the Pou4f2 promoter required a Wt1 binding element that was similar to a degenerative consensus site previously identified in other Wt1 responsive genes. Double-immunofluorescent labeling revealed co-expression of Pou4f2 and Wt1 in glomerular podocytes of adult kidney and in developing retinal ganglion cells of mouse embryos. Pou4f2 immunoreactivity was absent from the retinas of Wt1(-/-) embryos. In conclusion, we identified Pou4f2 as a novel downstream target gene of Wt1. Co-localization of both proteins in glomerular podocytes of the kidney and in developing retinal ganglion cells suggests a role for Wt1-Pou4f2 interaction in these tissues.
Wagner
Kay-Dietrich
KD
Johannes-Müller-Institut für Physiologie, Humboldt-Universität, Charité, Tucholskystrasse 2, 10117 Berlin, Germany.
Wagner
Nicole
N
Schley
Gunnar
G
Theres
Heinz
H
Scholz
Holger
H
D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007668:Kidney / Q000378:metabolism; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012160:Retina / Q000196:embryology / Q000378:metabolism; D050818:Transcription Factor Brn-3; D050820:Transcription Factor Brn-3B; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D025721:WT1 Proteins / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; C494190:POU4F2 protein, human; D011993:Recombinant Fusion Proteins; D050818:Transcription Factor Brn-3; D050820:Transcription Factor Brn-3B; D014157:Transcription Factors; D025721:WT1 Proteins; D008156:Luciferases