Integration of Lef/Tcf isoforms in regulatory networks involved in brain pattering

• Applicant: Dr. Dietmar Gradl
• Subject Area: Developmental Biology
• Term: from 2003 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5398464

As nuclear mediators of the oncogenic Wnt/b-catenin signaling pathway, the sequence specific HMG-box transcription factors of LEF/TCF family graduate important decisions in embryogenesis and in the development of malignat carcinoma. In the previous funding period we characterized the different properties of the individual LEF/TCF family members in Xenopus by identifying several repressive and activating domains within these molecules. The different expression patterns and properties of XTCF3, XTCF-4 A, B, C and XLEF-1 implicate a function of these transcription factors as modifiers of the cellular response in canonical Wnt-signaling. To test this hypothesis we will focus on the role of individual LEF/TCF transcription factors in patterning the brain where they exhibit distinct non-overlapping expression profiles. To identify the function of single transcription factors we will apply antisense morpholino injections in combination with ectopic expression of the other LEF/TCF family members. Altered patterning of the brain will be followed by marker gene expression. These experiments will be performed with whole embryos as well as with neuralized animal cap explants. In a second part we will further clear up how the different properties of the transcription factors are layed down in their structure. In search for specific interaction partners we will perform Tandem-Affinity Purification (TAP) using double tagged fusion proteins of important LEF/TCF domains followed by MALDI-TOF analyses of the coprecipitates. Interesting interaction partners will be isolated and further caracterized. Their regulative function in canonical Wnt-signaling will be studied by double axis formation and reporter gene assays, and predominantly in brain patterning if they are co-expressed with LEF/TCF transcription factors in certain brain compartiments.

• DFG Programme: Research Grants
• Participating Person: Professorin Dr. Doris Wedlich (†)