Frizzled-1 (FZD1) is a G-protein coupled receptor with seven transmembrane domains. It is one of ten Frizzled family of Wnt receptors whose extracellular cysteine rich domain (CRD) binds Wnt proteins. Frizzled receptors are ubiquitously expressed in most cell types in adults, and show dynamic expression pattern changes during embryonic development. Frizzled receptors associate with low density lipoprotein receptor-related proteins (LRP5/LRP6) to transduce Wnt signals through the activation of disheveled proteins, inhibition of GSK-3 kinase, and stabilization of beta-catenin, which accumulates in the nucleus to promote Wnt-mediated gene transcriptions. Another signaling pathway involving PKC and calcium fluxes has been described, but it is not yet established as a distinct pathway independent of the canonical pathway. Frizzled-1 is activated by Wnt3a, Wnt3, Wnt1 and Wnt2. It is involved in transduction and intercellular transmission of polarity information during tissue morphogenesis and differentiation. Frizzled-1 is involved in a feedback mechanism to modulate the effects of bone morphogenic proteins (BMP) on mesenchymal cells.