Dickkopf related protein 1 (Dkk-1) is a secreted protein with two cysteine rich regions and is involved in embryonic development through its inhibition of the Wnt signaling pathway. All mice that were homozygous for the Dkk-1 knockout were dead at birth due to defects in the cranium and structures formed by the neural crest, such as failed development of eyes, olfactory placodes, frontonasal mass and mandibular processes, as well as incomplete development of the forebrain and midbrain and fusion of the digits of the forelimb.
Elevated levels of Dkk-1 in bone marrow, plasma and peripheral blood is associated with the presence of osteolytic bone lesions in patients with multiple myeloma.