Signaling induced by the protein Norrin regulates vascular development of vertebrate retina and controls important blood vessels in the ear.

[5] Norrin binds with high affinity to Frizzled 4, and Frizzled 4 knockout mice exhibit abnormal vascular development of the retina.

NDP is the genetic locus identified as harboring mutations that result in Norrie disease.

Norrie disease is a rare genetic disorder characterized by bilateral congenital blindness that is caused by a vascularized mass behind each lens due to a maldeveloped retina (pseudoglioma).

[5] This article on a gene on the human X chromosome and/or its associated protein is a stub.