Spatial and temporal distribution of Patched-related protein in the Drosophila embryo

• Ptr is closely related in predicted topology and domain organization to Ptc.
• At early stages of embryogenesis Ptr co-localizes with Ptc.
• At later stages, expression of Ptr is restricted to migrating hemocytes.
• Ptr could be acting as receptor of embryonic macrophage.

Patched-related (Ptr) encodes a protein with 12 potential transmembrane domains and a sterol-sensing domain that is closely related in predicted topology and domain organization to Patched, the canonical receptor of the Hedgehog pathway. Here we describe the production of an antibody specific for Drosophila Ptr and analyse its spatial and temporal distribution in the embryo. We find that at early developmental stages Ptr is predominantly localized at cell periphery but later on it becomes strongly and almost exclusively expressed in hemocytes. Interestingly Ptr null mutant embryos died without hatching. Our findings suggest that Ptr plays an essential function in Drosophila development, perhaps as a new receptor of embryonic hemocytes.