The mouse limb bud is an excellent model to study how groups of cells organize themselves into structures. A key player is the transcriptional regulator GLI3, which functions first upstream of SHH in the polarisation of the limb field. Later, SHH regulate s GLI3 processing such that low levels of the transcriptional repressor (GLI3R) correlate with high levels of SHH signalling in the posterior limb bud. The resulting GLI3R gradient is essential for distal progression of limb development and specification of digit identities. My research will focus on the following main unsolved questions: the mechanism controlling Gli3 activation and thereby polarization of the limb field remains unknown together with the majority of direct GLI3 targets. Furthermore, in spite of proposals that GLI3 functions differ significantly during early -SHH independent- and subsequent -SHH dependent- limb bud development, the temporal modulation of GLI3 functions has not been studied.
The specific objectives are:
1) Identify the mechanism controlling Gli3 activation using a BAC transgenic approach with an in-frame fusion of a GFP tag (BAC-Gli3/gfp) combined with manipulation of candidate pathways/genes in cultured embryos and genetics.
2) Identify direct transcriptional targets of Gli3 in the limb bud by FACS cell isolation and micro-arrays using the transgenic (1) and knock-in mouse strains (3).
3) GLI3 roles will be dissected by tamoxifen-induced conditional inactivation of Gli3 at specific stages: before, during and after SHH signalling . These mice are a general model to analyse GLI3 roles during development and adult life (including stem cell renewal and carcinogenesis).My goal is to establish an independent research group that analyses bio-medically relevant aspects of developmental signals (e.g. Shh/Wnt) using mouse and fish models. Through the EIF I will gain competences in advanced mouse genetics, an expertise mastered in the host group, and complement my previous training.
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