Frizzled 4, officially known as frizzled class receptor 4 and designated FZD4, is a protein encoded by the FZD4 gene in humans. It is a member of the frizzled (Fz) gene family, which encodes seven-transmembrane domain proteins that primarily function as receptors for Wnt signaling proteins. Frizzled 4 is embedded in the outer membrane of many cell types, where it plays a critical role in transmitting chemical signals from outside the cell to the nucleus. Frizzled 4 has an almost ubiquitous expression pattern and is found in a wide range of human tissues. Mutations in the FZD4 gene are linked to familial exudative vitreoretinopathy (EVR1), an eye disorder that affects the retina and can lead to progressive vision loss.