Dickkopf-1 (DKK-1) is a secreted protein that belongs to the Dickkopf family of Wnt signaling inhibitors. In mice, DKK-1 is expressed in various tissues, including bone, brain, and reproductive organs, and plays a critical role in regulating the Wnt signaling pathway. DKK-1 functions by binding to the Wnt co-receptor LRP5/6, thereby inhibiting the canonical Wnt signaling cascade. By antagonizing Wnt signaling, DKK-1 suppresses the differentiation and proliferation of osteoblasts, leading to the inhibition of bone formation. DKK-1 is also involved in other biological processes, such as embryonic development, tissue homeostasis, and cancer progression. Dysregulation of DKK-1 has been implicated in skeletal disorders, such as osteoporosis and osteoarthritis, as well as in various cancers, highlighting the importance of DKK-1 in development and disease.