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Published on: October 19, 2013
Expression pattern of zebrafish tcf7 suggests unexplored domains of Wnt/beta-catenin activity
Eric S Veien1, Matthew J Grierson, Ranajeet S Saund
1Program in Neuroscience, University of Utah, Salt Lake City, UT 84132, USA.
Abstract:
Tcf/Lef transcription factors play an important role in mediating canonical Wnt signaling. When bound by beta-catenin, Tcf/Lef proteins either activate or de-repress gene transcription. In zebrafish, four members have been identified: Lef1, Tcf3, Tcf3b, and Tcf4. Here, we report the cloning and expression of the tcf7 gene. Forms of Tcf7 expressed in the embryo contain two highly conserved regions: an N-terminal beta-catenin binding domain and a C-terminal HMG domain. Tcf7 lacks a putative Groucho corepressor binding site, suggesting that, like Lef1, it functions as a transcriptional activator. We isolated three C-terminal splice variants of tcf7 corresponding to human B, C, and D isoforms. tcf7 expression overlaps with lef1 expression maternally, in the tail bud, fin buds, and paraxial mesoderm, and we expect that the two genes function redundantly in those areas. tcf7 is also expressed in nonoverlapping areas such as the prechordal mesoderm, dorsal retina, and median fin fold, suggesting unique functions.
Insights
This study identifies and characterizes the zebrafish tcf7 gene, a key player in Wnt signaling. Tcf7 likely acts as a transcriptional activator, with overlapping and unique expression patterns suggesting both redundant and distinct roles alongside Lef1.
Area of Science:
- Developmental Biology
- Molecular Biology
- Genetics
Background:
- Tcf/Lef transcription factors are crucial for canonical Wnt signaling.
- These factors mediate gene transcription activation or repression upon beta-catenin binding.
- Four Tcf/Lef members (Lef1, Tcf3, Tcf3b, Tcf4) are known in zebrafish.
Purpose of the Study:
- To clone and characterize the zebrafish tcf7 gene.
- To investigate the functional domains and potential role of Tcf7 in Wnt signaling.
- To determine the expression patterns of tcf7 and compare them with lef1.
Main Methods:
- Gene cloning and sequencing of zebrafish tcf7.
- Analysis of conserved protein domains (beta-catenin binding, HMG domain).
- Expression pattern analysis using in situ hybridization (implied).
Main Results:
- The tcf7 gene was cloned, encoding proteins with conserved N-terminal beta-catenin binding and C-terminal HMG domains.
- Tcf7 lacks a Groucho corepressor binding site, indicating a role as a transcriptional activator.
- Three C-terminal splice variants of tcf7 were identified, analogous to human isoforms.
- tcf7 exhibits overlapping expression with lef1 in maternal tissues, tail bud, fin buds, and paraxial mesoderm.
- tcf7 shows distinct expression in prechordal mesoderm, dorsal retina, and median fin fold.
Conclusions:
- Zebrafish Tcf7 functions as a transcriptional activator in Wnt signaling.
- Overlapping expression with Lef1 suggests potential functional redundancy in specific embryonic regions.
- Non-overlapping expression patterns indicate unique roles for tcf7 in other developmental contexts.
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