page_title: Retinal degeneration (rhodopsin mutation)
section_title: Photoreceptor cell death
hierarchical_section_title: Retinal degeneration (rhodopsin mutation) / Photoreceptor cell death
context_page_description: Retinal degeneration is a retinopathy which consists in the deterioration of the retina caused by the progressive death of its cells. There are several reasons for retinal degeneration, including artery or vein occlusion, diabetic retinopathy, R.L.F./R.O.P., or disease. These may present in many different ways such as impaired vision, night blindness, retinal detachment, light sensitivity, tunnel vision, and loss of peripheral vision to total loss of vision. Of the retinal degenerative diseases retinitis pigmentosa is a very important example.
  Inherited retinal degenerative disorders in humans exhibit genetic and phenotypic heterogeneity in their underlying causes and clinical outcomes. These retinopathies affect approximately one in 2000 individuals worldwide. A wide variety of causes have been attributed to retinal degeneration, such as disruption of genes that are involved in phototransduction, biosynthesis and folding of the rhodopsin molecule, and the structural support of the retina. Mutations in the rhodopsin gene account for 25% to 30% of all cases of autosomal dominant retinitis pigmentosa in North America.
context_section_description: Photoreceptor cell death is the eventual outcome of retinal degeneration. Without proper function of the photoreceptor cells, vision is not possible. Irreversible loss of these cells has been attributed as a cause of blindness in many retinal degenerative disorders, including RP. The exact mechanism of photoreceptor cell death is not clearly understood. Among potential causes is the endocytosis of stable complexes formed between rhodopsin and its regulatory protein arrestin in certain mutants. Various studies have also documented that over-expression of rhodopsin itself (mutations in genes involved in the termination of rhodopsin signaling activity have been shown to cause degeneration by persistent activation of the phototransduction cascade ) causes photoreceptor cell death and may induce photoreceptor cell loss in transgenic animals expressing truncated rhodopsin. Yet another mechanism may be prolonged photoreceptor responses and also abnormal rhodopsin deactivation may induce outer segment shortening and eventual photoreceptor death.
  In RP photoreceptor cell death is believed to occur by programmed cell death or apoptosis.
caption: Illustration of the structure of the mammalian retina, including photoreceptor cells; rod cells and cone cells
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