Deltex modulates Dpp morphogen gradient formation and affects Dpp signaling in Drosophila

Deltex (Dx) is a context-dependent regulator of Notch signaling that can act in a non-canonical fashion by facilitating the endocytosis of the Notch receptor. In an RNAi-based modifier screen of kinases and phosphatases, we identified Thickveins (Tkv), the receptor of Decapentaplegic (Dpp), as one of the interactors of Dx. Dpp, a Drosophila homolog of TGF-β and bone morphogenetic proteins, acts as a morphogen to specify cell fate along the anterior-posterior axis of the wing. Tight regulation of Dpp signaling is thus indispensable for its proper functioning. Here, we present Dx as a novel modulator of Dpp signaling. We show evidence for the very first time that dx genetically interacts with dpp and its pathway components. Immunocytochemical analysis revealed that Dx colocalizes with Dpp and its receptor Tkv in Drosophila third-instar larval tissues. Furthermore, Dx was also seen to modulate the expression of dpp and its target genes, and we attribute this modulation to the involvement of Dx in the endocytosis and trafficking of Dpp. This study thus presents a whole new avenue of Dpp signaling regulation via the cytoplasmic protein Dx. This article has an associated First Person interview with the first author of the paper.