Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to Norrie disease ?
    ### Response:
    Mutations in the NDP gene cause Norrie disease.  The NDP gene provides instructions for making a protein called norrin. Norrin participates in the Wnt cascade, a sequence of steps that affect the way cells and tissues develop. In particular, norrin seems to play a critical role in the specialization of retinal cells for their unique sensory capabilities.
    