This gene encodes a protein that is a member of the dickkopf family. It is a secreted protein with two cysteine rich regions and is involved in embryonic development through its inhibition of the Wnt signaling pathway. Dickkopf WNT signaling pathway inhibitor 1 (Dkk1) is a protein-coding gene that acts from the anterior visceral endoderm. The dickkopf protein encoded by DKK1 is an antagonist of the Wnt/β-catenin signalling pathway that acts by isolating the LRP6 co-receptor so that it cannot aid in activating the WNT signaling pathway. DKK1 was also demonstrated to antagonize the Wnt/β-catenin pathway via a reduction in β-catenin and an increase in OCT4 expression.
This inhibition plays a key role in heart, head and forelimb development during anterior morphogenesis of the embryo.
Elevated levels of DKK1 in bone marrow, plasma and peripheral blood is associated with the presence of osteolytic bone lesions in patients with multiple myeloma. Due to the role of DKK1 in inflammation induced bone loss DKK1 is under investigation as target for therapeutic strategies in medicine and dentistry.
Scientists have created a DKK1 knockout model in mice that revealed the effects of this gene. All mice that were homozygous for the DKK1 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. This evidence supports the idea that inhibition of the Wnt signaling pathway by DKK1 is crucial to proper cranial development.
DKK1 is one of the most upregulated genes in androgen-potentiated balding, with DKK-1 messenger RNA upregulated a few hours after DHT treatment of hair follicles at the dermal papillain vitro. Neutralizing antibody against DKK-1 reversed DHT effects on outer root sheath keratinocytes. DKK-1 expression is attenuated by L-threonatein vitro, with the latter a metabolite of ascorbate.
Alzheimer's disease occurs due to the overproduction of β-amyloid peptide (βAP) that will cluster together to form plaques between neurons in the brain and disrupt cell function. In addition, there is an accumulation of neurofibrillary tangles of hyperphosphorylated tau inside the neuron. The Wnt signaling pathway is crucial for brain development processes, which include neuron proliferation and differentiation as well as neuroblast migration and axon guidance.
Downregulation of this signaling has been shown in Alzheimer’s patients as a result of high levels of DKK1. Because of the hyperphosphorylation induced by DKK1, tau cannot interact with neuronal microtubules consequently compromising axonal transport resulting in synaptic loss and neuronal apoptosis. Because of its antagonistic effects on the Wnt signaling pathway, it is believed that DKK1 is a common marker for neuronal death in neurodegenerative diseases like Alzheimer’s.
^ abMukhopadhyay M, Shtrom S, Rodriguez-Esteban C, Chen L, Tsukui T, Gomer L, et al. (September 2001). "Dickkopf1 is required for embryonic head induction and limb morphogenesis in the mouse". Developmental Cell. 1 (3): 423–34. doi:10.1016/s1534-5807(01)00041-7. PMID11702953.
^Kwack MH, Sung YK, Chung EJ, Im SU, Ahn JS, Kim MK, Kim JC (February 2008). "Dihydrotestosterone-inducible dickkopf 1 from balding dermal papilla cells causes apoptosis in follicular keratinocytes". The Journal of Investigative Dermatology. 128 (2): 262–9. doi:10.1038/sj.jid.5700999. PMID17657240.
Tian E, Zhan F, Walker R, Rasmussen E, Ma Y, Barlogie B, Shaughnessy JD (December 2003). "The role of the Wnt-signaling antagonist DKK1 in the development of osteolytic lesions in multiple myeloma". The New England Journal of Medicine. 349 (26): 2483–94. doi:10.1056/NEJMoa030847. PMID14695408.
Lee AY, He B, You L, Xu Z, Mazieres J, Reguart N, et al. (October 2004). "Dickkopf-1 antagonizes Wnt signaling independent of beta-catenin in human mesothelioma". Biochemical and Biophysical Research Communications. 323 (4): 1246–50. doi:10.1016/j.bbrc.2004.09.001. PMID15451431.