Neural crest cells organize the eye via TGF-β and canonical Wnt signalling.
Bottom Line: In vertebrates, the lens and retina arise from different embryonic tissues raising the question of how they are aligned to form a functional eye.Here we show, using the chick as a model system, that neural crest-derived transforming growth factor-βs activate both Smad3 and canonical Wnt signalling in the adjacent ectoderm to position the lens next to the retina.They do so by controlling Pax6 activity: although Smad3 may inhibit Pax6 protein function, its sustained downregulation requires transcriptional repression by Wnt-initiated β-catenin.
Affiliation: Department of Craniofacial Development, King's College London, Guy's Campus, London SE1 9RT, UK.Show MeSH
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Mentions: To assess whether activated Smad3 suppresses lens fate in vivo, we electroporated constitutively active Smad3 (ref. 16) into the presumptive lens ectoderm (PLE). Although control green fluorescent protein-expressing cells were incorporated into the lens and express the lens marker δ-crystallin (Fig. 1a–c; 3/3 lenses), constitutively active Smad3-expressing cells were excluded from the lens and did not express δ-crystallin (Fig. 1d–f; 0/5 lenses). Together, the above results suggest that TGF-βs prevent lens formation at inappropriate positions.
Affiliation: Department of Craniofacial Development, King's College London, Guy's Campus, London SE1 9RT, UK.