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Transcript of Norrie Disease
*other assorted physical abnormalities The Norrin Ligand Norrin is a protein that attches to a protein receptor (amusingly) called frizzled-4 in the outer membrane of cells. When this happens, a pathway known as the Wnt/ Beta-catenin signaling pathway is activated. Norrin in the Human Body Norrie disease and NDP Inheritance Patterns of Norrie Disease Citations Research into Norrie Disease and Possible Treatments ("Norrie Disease-Genetics home reference", 2009) (Miller, 2008) ("Norrie Disease-Genetics home reference", 2009) Growths made of immature retinal cells form behind the eyes, causing blindness at or shortly after birth. The gene that norrin helps activte makes sure that blood vessels are formed correctly in the fetus. This is especially crucial to the growth of the eyes because they are highly dependent on the oxygen supplied by blood. (Ohlmann & Tamm, 2009, p. 243-257) Even after birth, the body continues to be dependent on norrin. It has been shown to aid in the maintenance of the blood-brain barrier, which keeps any infections or pathogens in your blood stream away from your brain. ("Study reveals dual role for Norrin/Frizzled-4 protein pair", 2012) However sometimes things do not go as planned. If there is a flaw in what is known as the NDP gene in a fetus, they will be subject to norrie disease. This is the location of the NDP gene in a human chromosome.
It is located on the short arm of the X chromosome, at potion 11.4 ("NDP-Genetics home reference", 2009) As we all know, nature strives for the best possible genetic makeup for any offspring of any species. To do this, if there is a flaw in the DNA of a gamete, the body usually either tries to fix it or destroy the defective cell. This gene is important because it is responsible for the creation of the norrin we were talking about earlier.
When the gene is defective, the norrin that the body creates is defective as well. In this way, it cannot bind to the frizzled-4 receptors in the cell. Watch what happens:
Miller, J. (2008). Norrie Disease Information | Norrie Disease Association. Home | Norrie Disease Association. Retrieved December 19, 2012, from http://www.norriedisease.org/norrie-disease-information
NDP - Norrie disease (pseudoglioma) - Genetics Home Reference. (2009, February). Genetics Home Reference - Your guide to understanding genetic conditions. Retrieved December 19, 2012, from http://ghr.nlm.nih.gov/gene/NDP
Norrie disease - Genetics Home Reference. (2007, March). Genetics Home Reference - Your guide to understanding genetic conditions. Retrieved December 19, 2012, from http://ghr.nlm.nih.gov/condition/norrie-disease
Ohlmann, A., & Tamm, E. R. (2009). Norrin: Molecular and functional properties of an angiogenic and neuroprotective growth factor. Progress in Retinal and Eye Research, 31(3), 243-257. Retrieved from http://www.sciencedirect.com/science/article/pii/S1350946212000134.
Study reveals dual role for Norrin/Frizzled-4 protein pair. (2012, December 7). THE MEDICAL NEWS | from News-Medical.Net - Latest Medical News and Research from Around the World. Retrieved December 19, 2012, from http://www.news-medical.net/news/20121207/Study-reveals-dual-role-for-NorrinFrizzled-4-protein-pair.aspx?page=2
Wnt signal transduction pathways. (2008, June). National Center for Biotechnology Information. Retrieved December 19, 2012, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2634250/ (Ohlmann & Tamm, 2009, p. 243-257) First of all, the norrin attaches to the Frizzled-4 receptor and activates the pathway The dishevelled protein inhibits the GSK-3 Beta GSK-3 Beta usually phosphorylates and destroys the Beta-Catenin in the cell. However in this pathway the GSK is being inhibited, so more Beta-Catenin is allowed to reach the nucleus of the cell. The Beta-Catenin then binds to the Tcf and Lef in the nucleus. This complex helps promote target genes. ("Wnt signal transduction pathways", 2008) ("Norrie Disease-Genetics home reference", 2009) As I said earlier, norrie disease is caused by flaws on the NDP gene which is contained on the X chromosome. Because of this, only males are subject to norrie disease. Females can however still be carriers. ("Norrie Disease-Genetics home reference", 2009) Norrie disease can be caused by spontanious mutation of the NDP gene, but in most cases it was inherited from a parent. In this case there is a fifty percent chance that her offspring will be affected. This diagram shows the patterns of how the children of a mother carrier could be affected. (Miller, 2008) Things are slightly different when it is the father with the flawed gene.
In this case, no sons of this father will have norrie disease. On the other hand, all daughters will be carriers. (Miller, 2008) This pathway activates the dishevelled protein. The norrin created is defective and cannot bind to the frizzled-4 receptor. The pathway is not activated. The dishevelled protein is not activated and so it does not inhibit the GSK-3 beta. The Beta-Cantenine is then destroyed by the GSK-3 Beta. Because of this it does not reach the nucleus and does not help activate the NDP gene. Because the NDP gene is not activated, cellular processes guiding the creation of capillaries will be affected. The result is ineffective, misplaced and 'leaky' blood vessels. This is norrie disease. ("Norrie Disease-Genetics home reference", 2009 ("Wnt signal transduction pathways", 2008 To date there is no known cure for norrie disease, but research is being done to better understand the norrin ligand. Current treatments for norrie disease include eye sugary as well as laser therapy in infancy to treat blindness, as well as hearing aids and implants to treat deafness. Behavioral disorders can be treated by counseling and medication.
Work is also being done to develop lenses that would provide the eye with a constant supply of something (possibly norrin) to activate the Wnt/ Beta-catenin signaling pathway and hopefully minimize the extent of the damage. (Miller, 2008) Fig 1: retinal cells Pictures:
Fig 1: Norrie Disease. EyeRounds.org - Ophthalmology - The University of Iowa. (n.d.). Department of Ophthalmology & Visual Sciences. Retrieved December 19, 2012, from http://webeye.ophth.uiowa.edu/eyeforum/cases/100-Coats-Disease.htm
Fig 2: Scholastic's The Magic School Bus: COLOR IT IN! (n.d.). Scholastic Canada | Home. Retrieved December 19, 2012, from http://www.scholastic.ca/magicschoolbus/games/teacher/index.htm
Fig 3 A and B: own creation based on
ScienceDirect.com - Pharmacology & Therapeutics - The Wnt signaling pathway: Aging gracefully as a protectionist? (2008, April). ScienceDirect.com | Search through over 11 million science, health, medical journal full text articles and books. Retrieved December 19, 2012, from http://www.sciencedirect.com/science/article/pii/S016372580800017X
Fig 4:PBR Opthomology flashcards | Quizlet. (n.d.). Simple free learning tools for students and teachers | Quizlet. Retrieved December 19, 2012, from http://quizlet.com/2475290/pbr-opthomology-flash-cards/
Fig 5:NDP - Norrie disease (pseudoglioma) - Genetics Home Reference. (n.d.). Genetics Home Reference - Your guide to understanding genetic conditions. Retrieved December 19, 2012, from http://ghr.nlm.nih.gov/gene/NDP
Fig 6: Norrie disease. (n.d.). In Wikipedia, the free encyclopedia. Retrieved December 19, 2012, from http://en.wikipedia.org/wiki/Norrie_disease Fig 2 Fig 3A: signal pathway Fig 3B: pathway without norrin Fig 4: child with Leukocoria Fig 5: chromosome Fig 6: Inheritance Patterns