Fig. 4.

Hh hitches a ride on exosomes that travel along cytonemes in the Drosophila wing disc. Left panel Hh producing cells (pink) of the wing disc epithelium produce cytonemes that extend over the domain of Hh signaling. Right Hh and its co-receptor Ihog are initially secreted apically before being endocytosed in a Disp and Rab5-dependent manner. Re-internalised Hh, Ihog, and Disp undergo transcytosis and are secreted basally; some are found within MVBs on intraluminal vesicles (grey). MVBs fuse with the basal membrane and release exosome-bound Hh, Ihog, and Disp that travel along cytonemes