THE PRODUCT OF HEDGEHOG AUTOPROTEOLYTIC CLEAVAGE ACTIVE IN LOCAL AND LONG-RANGE SIGNALING

THE secreted protein products of the hedgehog (hh) gene family are ass ociated with local and long-range signalling activities that are respo nsible far developmental patterning in multiple systems, including Dro sophila embryonic and larval tissues(1-8) and vertebrate neural tube, limbs and somites(9-15). In a process that is critical for full biolog ical activity, the hedgehog protein (Hh) undergoes autoproteolysis to generate two biochemically distinct products, an 18K amino-terminal fr agment, N, and a 25K carboxy-terminal fragment, C (ref. 16); mutations that block autoproteolysis impair Hh function. We have identified the site of autoproteolytic cleavage and find that it is broadly conserve d throughout the hedgehog family. Knowing the site of cleavage, we wer e able to test the function of the N and C cleavage products in Drosop hila assays. We show here that the N product is the active species in both local and long-range signalling. Consistent with this, all twelve mapped hedgehog mutations either affected the structure of the N prod uct directly or otherwise blocked the release of N from the Hh precurs or as a result of deletion or alteration of sequences in the C domain.