Mouse WNT3a has been shown to be acylated at conserved S209 with the monounsaturated fatty acid palmitoleic acid (C16:1). Acylation is required for WNT3a secretion from the cell, as WNT3a (S209A) protein is retained in the ER. Acylation depends on the putative O-acyl-transferase PORCN, which was first identified as a Drosophila segment polarity gene that is required for the normal distribution of Wg in embryos (Kadowaka et al, 1996). In porcn-deficient cells, WNT3a accumulates in an unacylated form in the ER (Takada et al, 2006). PORCN-dependent acylation is required for the processing of other mouse WNT ligands (Tanaka, 2002).