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 b oth 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 s ecretion of Wg. porc encodes a novel transmembrane protein that appear s to be concentrated at the endoplasmic reticulum. We present both gen etic and in vitro evidence demonstrating that pore is involved specifi cally in the processing of Wg. We identified a human sequence related to Porc suggesting the existence of a family of proteins involved in p rocessing of Wnts.