NDP (Norrie disease (pseudoglioma)) gene encodes a secreted protein called norrin. It is involved in the activation of canonical Wnt signaling pathway through binding with Frizzled 4 (FZD4) and low-density lipoprotein-related protein 5 (LRP5) coreceptor. It contains a cystein-knot motif th at is involved in the activation of the pathway. It plays a crucial role in angiogenesis for the development of eye, ear, brain, and female reproductive system. It is essential for the maintenance of blood–brain barrier and blood–retina barrier integrity. Mutations in this gene cause Norrie disease th at is characterized by very early childhood blindness, progressive mental disorder, growth failure and seizure. Defects in the gene also cause the milder disorder familial exudative vitreoretinopathy (FEVR).
