Expression pattern of zebrafishtcf7 suggests unexplored domains of Wnt/?-catenin activity

Abstract

Tcf/Lef transcription factors play an important role in mediating canonical Wnt signaling. When bound by ␤-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 ␤-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. Developmental Dynamics 233: 233-239, 2005.

Wnt Signaling in Vertebrate Axis Specification

“…Subsequent experiments showed that Vent2 gene activation is accompanied by the removal of TCF3 from the promoter and its replacement by TCF1, an activator form of TCF that is resistant to HIPK2-mediated phosphorylation (Hikasa and Sokol 2011). This finding strongly supports the view that the four vertebrate homologs of TCF, expressed in a tissue-specific manner Dorsky et al 1999Dorsky et al , 2003Konig et al 2000;Roel et al 2003;Veien et al 2005), play diverse roles in Wnt signaling and axis specification (Hamilton et al 2001;Houston et al 2002;Roel et al 2002;Liu et al 2005;Standley et al 2006). Although both TCF3 and TCF1 can bind b-catenin and Groucho corepressors Brantjes et al 2001), the two proteins appear to function very differently.…”

Lef1 is required for progenitor cell identity in the zebrafish lateral line primordium

“…Digoxygenin-or fluorescein-labeled antisense RNA probes were generated for the following genes: eya1 (Sahly et al, 1999), fgf10a (Grandel et al, 2000), pea3 (Raible and Brand, 2001;Roehl and Nusslein-Volhard, 2001), lef1 (Dorsky et al, 1999), tcf7 (Veien et al, 2005), tcf7l1a (Dorsky et al, 2003), tcf71b (Dorsky et al, 2003) dkk1 (Aman and Piotrowski, 2008), cxcr4b and cxcr7b . Whole-mount immunolabeling was performed following established protocols (Ungos et al, 2003).…”

Insertional mutagenesis by theTol2transposon-mediated enhancer trap approach generated mutations in two developmental genes:tcf7andsynembryn-like

“…Roles of Tcf7 and Lef1 in outgrowth of the pectoral fin tcf7 and lef1, both members of the Lef/Tcf family of transcription factors that mediate Wnt signaling, are expressed in the fin bud and are thought to be functionally redundant (Veien et al, 2005). However, this notion has not yet been tested.…”

“…Tcf7 is a transcription factor mediating Wnt signaling. Although the zebrafish tcf7 gene was cloned previously (Veien et al, 2005), no mutation has been reported. synbl is a zebrafish homolog of the C. elegans synembryn gene, the product of which has been shown to activate both the G␣ q and G␣ S pathway, leading to production of diacylglycerol and cyclic AMP, respectively (Miller et al, 2000;Schade et al, 2005).…”