Fig. 4.

Morphogen Reception by Target Cells. Cytonemes can deliver signal through contact with receiving-cell bodies (A,B) or other cytonemes (C). A Signal-containing cytonemes directly contact the cell body. B Cytonemes extend into plasma membrane invaginations on the cell body. C Cytoneme tips contact to form a morphogenetic synapse where signals are presented through: (I) Incorporation into the plasma membrane at the cytoneme tip. (II) Transport along cytonemes for release from the tip. (III) Vesicular transport along the cytoneme for exovesicle-based release at a morphogenetic synapse for signaling