Drosophila melanogaster Hedgehog cooperates with Frazzled to guide axons through a non-canonical signalling pathway

• We analysed the effects of Hh in midline axon guidance in Drosophila melanogaster.
• We show that Hh is expressed in the ventral nerve cord of Drosophila melanogaster embryos.
• Overexpression of hh in the midline causes ectopic midline crossing of FasII-positive axonal tracts.
• A non-canonical Hh signalling pathway affects axonal guidance by cooperating with Netrin/Frazzled chemoattraction.

We report that the morphogen Hedgehog (Hh) is an axonal chemoattractant in the midline of Drosophila melanogaster embryos. Hh is present in the ventral nerve cord during axonal guidance and overexpression of hh in the midline causes ectopic midline crossing of FasII-positive axonal tracts. In addition, we show that Hh influences axonal guidance via a non-canonical signalling pathway dependent on Ptc. Our results reveal that the Hh pathway cooperates with the Netrin/Frazzled pathway to guide axons through the midline in invertebrates.