The segment polarity gene porcupine encodes a putative multitransmembrane protein involved in Wingless processing

The Wnt protein Wingless (Wg) functions as a signal in patterning of both the Drosophila embryo and imaginal discs. Lack of porcupine (porc) activity is associated with mutant phenotypes similar to those of wg mutations. In pore mutant embryos, Wg protein is confined to the cells that produce it, suggesting that Porc plays a role in professing or secretion of Wg. porc encodes a novel transmembrane protein that appears to be concentrated at the endoplasmic reticulum. We present both genetic and in vitro evidence demonstrating that pore is involved specifically in the processing of Wg. We identified a human sequence related to Porc suggesting the existence of a family of proteins involved in processing of Wnts.