The Wilms tumor suppressor Wt1 promotes cell adhesion through transcriptional activation of the alpha4integrin gene.
Cell-matrix interaction through specific adhesion molecules is a critical step during organ development. In addition, down-regulation of cell adhesion receptors may promote tumor invasion and metastasis. We show here that the Wilms tumor suppressor Wt1, which is necessary for normal development of the epicardium, coronary vessels, genitourinary system, and other tissues, activates transcription of the alpha4integrin gene. Binding of the Wt1(-KTS) form, which is transcriptionally active, to the proximal alpha4integrin promoter was demonstrated by electrophoretic mobility shift assay and chromatin immunoprecipitation. A reporter construct harboring approximately 1.9 kb of the human alpha4integrin gene promoter was activated significantly by transient co-transfection of a Wt1(-KTS) expression plasmid. Introducing mutations in two identified Wt1(-KTS) binding motifs in the proximal promoter of the alpha4integrin gene abrogated this stimulatory effect. Endogenous alpha4integrin transcripts were increased more than 3-fold in human embryonic kidney 293 cells with stable expression of the Wt1(-KTS) protein. Wt1-overexpressing cells showed augmented adhesion to the alpha4integrin ligand vascular cell adhesion molecule-1 that was abolished upon incubation with an inhibitory alpha4integrin antibody. Double immunofluorescent staining revealed co-localization of Wt1 and alpha4integrin in the developing epicardium of mouse embryos. Cardiac expression of alpha4integrin was reduced significantly in embryos with a homozygous Wt1 defect (Wt1-/-). These findings demonstrate that Wt1 can support cell adhesion through enhanced expression of alpha4integrin. This transcriptional activation of the alpha4integrin gene by Wt1(-KTS) might contribute to normal formation of the epicardium and other tissues in the developing embryo.
Kirschner
Karin M
KM
Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, Tucholskystrasse 2, 10117 Berlin, Germany.
Wagner
Nicole
N
Wagner
Kay-Dietrich
KD
Wellmann
Sven
S
Scholz
Holger
H
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D006801:Humans; D039441:Integrin alpha4 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D015533:Transcriptional Activation; D025721:WT1 Proteins / Q000378:metabolism / Q000502:physiology*
D025721:WT1 Proteins; D039441:Integrin alpha4