CD349 is a member of the Frizzled family, known as Frizzled-9 (Fz9, FZD9, hFz9, or FzE6) which was originally described as FZD3. Ten frizzled member have been identified in humans. FZD9 is a seven transmembrane G-protein-coupled receptor (GPCR), a receptor for Wnt proteins. It is involved in the activation of Wnt/beta-catenin pathway (canonic Wnt signaling). FZD9 is predominately expressed in fetal and adult brain, testis, eye, skeletal muscle and kidney and is also expressed on Mesenchymal stem cells, and neural precursor cells. Frizzled proteins play important roles in controlling cell fate, proliferation, migration, tissue architecture and organogenesis during embryonic development and in adult organisms. FZD9 isan important factor fornervous system development and is critical for hippocampal development.