What is prion disease?

Prion diseases are a type of neurodegenerative disorder that is produced by the accumulation of abnormal proteins in the brain. Prion disease predominantly affects the brain, but it can also attack the eyes, especially the light-sensitive photoreceptors called cones and rods which are present in the retina, and other organs. These are steadily deteriorating and typically deadly diseases of the brain and can occur in people as well as some other mammals. Examples: mad cow disease in cattle, Creutzfeldt-Jakob disease in people, chronic wasting disease in deer, elk, and moose, and bovine spongiform encephalopathy in cattle.

Prion Infected Retina. Image Courtesy of NIH

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A recent study done by scientists at the National Institutes of Health states that the initial eye injury from prion disease occurs in the cone photoreceptor cells, especially in the cilia and the ribbon junctions. The researchers say, their discovery may provide understanding on human retinitis pigmentosa, an inherited disorder with closely related photoreceptor degradation advancing into blindness. The understanding of how prion diseases develop in the eyes can aid scientists to look for strategies to steady the growth of prion diseases.

In their study, the researchers, from NIHs National Institute of Allergy and Infectious Diseases at Rocky Mountain Laboratories in Hamilton, Montana, used research mice diseased with scrapie, a prion disease routine to sheep and goats. Scrapie is nearly associated with human prion diseases, Creutzfeldt-Jakob disease (CJD).

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The scientists discovered the accumulation of a lump of prion protein was seen first in cone photoreceptors next to the cilia, pipe-like formation needed for transferring molecules between cellular sections with help of the confocal microscope. The study suggests that by obstructing the movement through cilia, these clumps may layout a key early process by which prion infection particularly smashes photoreceptors. Relatable findings were seen in rods as well.Exactly before the destruction of ribbon synapses (specialized neutron links present in the eye and ear neural pathways) and end of photoreceptors, there was an accumulation of prion protein in these structures.

The findings from this study were unique and were never observed before. The association between prion protein and retinal injury is probably present in all prion-vulnerable species, as well as humans.

There are other kinds of declining disorders that are also distinguished by abnormal folding of self-proteins, such as Alzheimers and Parkinsons diseases. The scientists are looking to investigate if related findings take place in the retinas of these people.

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Prion-induced photoreceptor degeneration begins with misfolded prion protein accumulation in cones at two distinct sites: cilia and ribbon synapses

Prion Seeds Distribute throughout the Eyes of Sporadic Creutzfeldt-Jakob Disease Patients

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Scientists Pinpoint the Spots of Early Prion Protein Deposition in the Retina - Gilmore Health News