Human Frizzled Homolog 9 (FZD9) Protein

Background

FZD9 is a member of the Frizzled family of G protein-coupled receptors involved in Wnt signaling, primarily through the canonical β-catenin-dependent pathway. It is highly expressed in the brain, spleen, and bone, where it plays critical roles in neuronal development, immune regulation, and bone homeostasis. In bone biology, FZD9 promotes osteoblast differentiation and mineralization, contributing to skeletal development and bone repair. Deletion or reduced expression of FZD9 is associated with bone fragility and osteoporosis, highlighting its importance in bone formation. In the central nervous system, FZD9 regulates neural connectivity, synaptic plasticity, and cognitive function, with its dysregulation linked to neurodevelopmental disorders and neurodegenerative diseases like Alzheimer’s. FZD9 also contributes to immune system function, particularly in lymphocyte development and maturation. In cancer, FZD9 expression is altered in B-cell malignancies, such as multiple myeloma, where it influences cell proliferation and survival through Wnt signaling activation. FZD9’s role in maintaining tissue homeostasis and its dysregulation in bone disease and cancer make it a potential therapeutic target for osteoporosis and hematological malignancies.