The LRP6 gene encodes a member of the low density lipoprotein receptor (LDLR) gene family, which consists of cell surface proteins involved in receptor-mediated endocytosis of specific ligands. LDLR proteins are comprised of the same basic structural motifs: an extracellular domain that contains LDLR binding repeats and EGF repeats with associated spacer domains containing the YWTD motif; a single transmembrane-spanning domain; and a C-terminal cytoplasmic domain that generally contains at least 1 copy of the NPXY motif (Brown et al., 1998 [PubMed 9704021]). LRP6 and LRP5 (MIM 603506) function as coreceptors for WNT (MIM 164820) ligands and thus play a role in WNT signaling, which is important in a wide variety of biologic processes during pre- and postnatal life in invertebrates and vertebrates (Kokubu et al., 2004 [PubMed 15469977]).[supplied by OMIM]