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Transcript of Norrie Disease
Pupils appear white when light is shown on them (leukocoria)
Irises or entire eyeballs may shrink and deteriorate during first months of life.
≈1/3 develop progressive hearing loss
More than 1/2 develop delays in motor skills
Mid-Moderate intellectual disabilities w/ psychosis
Abnormalities that effect circulation, breathing, digestion, excretion, or reproduction How do you get Norrin Disease? Norrin Disease is most often the result of a mutated gene that the child receives from one of their parents, though it can develop without the parents being carriers. Affected males transmit the mutation to all their daughters, who will be carriers, and non of their sons. Carrier females have a 50% chance of transmitting the mutation to their son who if receives the mutation will be effected, females will not be effected. This is called an x-linked recessive gene. What Causes the Disease Indirectly? Mutations in the NDP (Norrie Disease Pseudoglioma) gene is the cause for Norrie Disease. The NDP gene instructs the making of the norrin protein. Norrin participates in the Wnt cascade, a sequence that effects the way cells develop. Norrin plays a critical role in the specialization of retinal cells. Mutations in the NDP causes the norrin to be misshapen not allowing it to bind with another protein called Frizzled-4 like it should in order to initiate the Wnt cascade. These mutations interfere with the cells transcriptive and cell differentiation signals and abilities. Transcription? When the norrie protein is unable to bond with the frizzled-4 protein it is unable to start the Wnt cascade which sends the cells the message to stop replicating. When the Wnt is not activated the cell continues to replicate causing a build up of unneeded cells. Cell Differentiation? Cell Differentiation is the method in which the cell is told how to develop. When the Wnt is unable to happen due to the mutation of the norrie protein the cell doesn't receive the information to grow and develop. Over all Effect: When both the cell's transcriptive and differentiation signals are effected it created a mass of undeveloped cells. With Norrie Disease all of these undeveloped retinal cells mass in the back of the eye, not allowing the individual to see. What does the signaling process look like? The signaling process looks differently depending upon wither or not the gene is mutated. Normal Signaling Normally the norrie protein is able to bind with the frizzled-4 protein. This in turn activates the Wnt cascade. (As seen at right) Abnormal signaling When the protein is mutated if doesn't allow the frizzled protein to bind with the norrie protein and in turn bind with the Wnt protein What is Being Done to Help People with this Disease? Laser therapy and surgery can be used to help infants who have not completely lost their vision. With hearing loss the use of hearing aids and cochlear implants is available. The behavioral abnormalities and retardation symptoms can be lessened through counseling, special education, and medications. Research is attempting to understand how the genetic mutations are causing Norrie disease, as well as the biologic issues that lead to all of the symptoms of Norrie Disease.