Negative regulator of the Wnt signaling pathway. Inhibits Wnt signaling in a cell-autonomous manner and functions upstream of beta-catenin. May act via its interaction with Wnt and LRP proteins (By similarity). Homodimer. Interacts with LRP5 and WNT3A (By similarity). Expressed during early development of the extraembryonic structures, nervous system, vascular system and inner ear. Also expressed in mesenchyme of various parts of the embryo and in adult hair follicles. APCDD1 is transcriptionally regulated by the CTNNB1/TF7L2 complex. N-Glycosylated. Belongs to the APCDD1 family. Truncated C-terminus.