Nanobodies as novel tools to study morphogen gradient formation in vivo. Stefan Harmansa, Markus Affolter, Emmanuel Caussinus. Biozentrum, Universität Basel, Basel, Switzerland.

   Monomeric antibody domains, so called nanobodies, have emerged as powerful tools to interfere with proteins of interest in vivo (Caussinus et al., NSMB 19, 117-121(2012)). We have generated membrane-bound versions of an anti-GFP nanobody in order to interfere with gradient formation of a GFP-tagged version of the Decapentaplegic morphogen (Dpp::GFP) in the Drosophila wing imaginal disc. We find that a nanobody fused to CD8, a protein which localizes all around polarized epithelial cells, is able to sequester extracellular Dpp::GFP and thereby prevents gradient formation. We are currently localizing nanobodies specifically to either the apical or the basolateral cell surface, aiming at dissecting the function of Dpp along the apical and basal compartments and identifying the respective contributions of apical and basolateral Dpp on wing growth and patterning.