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A transcriptional response to Wnt protein in human embryonic carcinoma cells
Jennifer Willert1, Mirjam Epping, Jonathan R Pollack
1Department of Developmental Biology, Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305 USA. jennifer.willert@cox.net
Background:
Wnt signaling is implicated in many developmental decisions, including stem cell control, as well as in cancer. There are relatively few target genes known of the Wnt pathway.
Results:
We have identified target genes of Wnt signaling using microarray technology and human embryonic carcinoma cells stimulated with active Wnt protein. The ~50 genes upregulated early after Wnt addition include the previously known Wnt targets Cyclin D1, MYC, ID2 and betaTRCP. The newly identified targets, which include MSX1, MSX2, Nucleophosmin, Follistatin, TLE/Groucho, Ubc4/5E2, CBP/P300, Frizzled and REST/NRSF, have important implications for understanding the roles of Wnts in development and cancer. The protein synthesis inhibitor cycloheximide blocks induction by Wnt, consistent with a requirement for newly synthesized beta-catenin protein prior to target gene activation. The promoters of nearly all the target genes we identified have putative TCF binding sites, and we show that the TCF binding site is required for induction of Follistatin. Several of the target genes have a cooperative response to a combination of Wnt and BMP.
Conclusions:
Wnt signaling activates genes that promote stem cell fate and inhibit cellular differentiation and regulates a remarkable number of genes involved in its own signaling system.
Insights
Wnt signaling controls stem cell fate and cancer by activating numerous genes. This study identified novel Wnt target genes, including those crucial for development and disease, revealing new insights into Wnt pathway regulation.
Area of Science:
- Developmental Biology
- Molecular Biology
- Cancer Biology
Background:
- Wnt signaling plays a critical role in developmental processes and stem cell regulation.
- Dysregulation of Wnt signaling is frequently observed in various cancers.
- A limited number of Wnt target genes have been previously identified.
Purpose of the Study:
- To identify novel target genes regulated by Wnt signaling.
- To understand the role of Wnt signaling in stem cell fate and cancer.
- To elucidate the regulatory mechanisms of Wnt target gene activation.
Main Methods:
- Microarray analysis of human embryonic carcinoma cells stimulated with Wnt protein.
- Treatment with cycloheximide to assess the requirement for protein synthesis.
- Analysis of TCF binding sites in target gene promoters.
Main Results:
- Approximately 50 genes were found to be upregulated early after Wnt stimulation.
- Newly identified Wnt targets include MSX1, MSX2, Follistatin, and Frizzled.
- TCF binding sites are essential for the induction of target genes like Follistatin.
- Several target genes exhibit a cooperative response to Wnt and BMP signaling.
Conclusions:
- Wnt signaling activates genes that promote stem cell pluripotency and inhibit differentiation.
- The Wnt pathway regulates a significant number of genes involved in its own signaling cascade.
- These findings have implications for understanding Wnt's role in development and cancer.