For the normal development of the eye and other body systems, norrin is believed to be crucial.[6] Norrin also appears to be crucial in the specialization of the cells of the retina and the establishment of a blood supply to the inner ear and the tissues of the retina. The role of norrin in the specialization of retinal cells for their unique sensory is interfered by the mutation of NDP.[6] This results in an accumulation of immature retinal cells in the back of the eye. When norrin's role in the establishment of blood vessels supplying the eye is disrupted, eventually the tissues will break down.[6]