Prion diseases Creutzfeldt-Jakob disease
Prion diseases, also known as transmissible spongiform encephalopathies (TSEs), are a group of rare and fatal neurodegenerative disorders that affect humans and certain animals. They are characterized by the accumulation of abnormal, misfolded proteins in the brain, which can lead to progressive damage and dysfunction of the central nervous system. Prion diseases are unique among neurodegenerative disorders because they can be transmitted through exposure to infected tissues, and they are caused by misfolded proteins, rather than viruses or bacteria.
Here's an explanation of the key features and aspects of prion diseases:
Prions: The term "prion" stands for "proteinaceous infectious particle." Prions are abnormal forms of a normally occurring protein called prion protein (PrP). In their normal state, PrP proteins are found in the brain and other tissues, but they have a different, properly folded structure. In prion diseases, PrP proteins adopt an abnormal, misfolded conformation, which is resistant to normal cellular protein degradation processes.
Accumulation of Misfolded Prions: The hallmark of prion diseases is the accumulation of these misfolded prion proteins in the brain. These abnormal proteins have the ability to induce other normal PrP proteins to misfold and accumulate as well, leading to a chain reaction of protein misfolding and aggregation.
Neurodegeneration: The buildup of misfolded prion proteins disrupts normal brain function and leads to the death of nerve cells (neurons). This results in a variety of neurological symptoms, including cognitive impairment, muscle stiffness, coordination problems, and behavioral changes. Over time, these symptoms progress, and individuals affected by prion diseases often become severely disabled.
Transmissibility: One of the most striking features of prion diseases is their transmissibility. They can be transmitted between individuals through the consumption of infected tissue (such as contaminated meat), through medical procedures involving contaminated surgical instruments, or even through genetic inheritance in some cases.
Types of Prion Diseases: There are several types of prion diseases that affect humans, including:
a. Creutzfeldt-Jakob Disease (CJD): This is the most common form of prion disease and has several subtypes, including sporadic, familial, and acquired forms. Sporadic CJD occurs spontaneously without any known cause, while familial CJD is linked to inherited genetic mutations. Acquired forms can result from exposure to infected tissues or medical procedures.
b. Variant Creutzfeldt-Jakob Disease (vCJD): This form is associated with the consumption of beef contaminated with bovine spongiform encephalopathy (BSE or "mad cow disease"). It has a distinct clinical presentation and is thought to be caused by the consumption of contaminated beef products.
c. Gerstmann-Sträussler-Scheinker syndrome (GSS) and Fatal Familial Insomnia (FFI): These are rare familial forms of prion disease, each with its own unique clinical features.
Diagnosis and Treatment: Diagnosing prion diseases can be challenging, and there is currently no cure for these disorders. Diagnosis often involves clinical evaluation, brain imaging, and sometimes a brain biopsy. Management primarily focuses on relieving symptoms and providing supportive care to affected individuals.
In summary, prion diseases are a group of rare and devastating neurodegenerative disorders characterized by the accumulation of misfolded prion proteins in the brain, leading to progressive neurological dysfunction. Their transmissibility and the lack of effective treatments make prion diseases a particularly unique and challenging class of diseases to study and manage.
rs1799990, also known as Met129Val or M129V, is a SNP in the prion protein PRNP gene. The more common rs1799990(A) allele encodes the Met (methionine).
The 23andMe blog has a good article about the infectious Creutzfeldt-Jakob disease (vCJD), both people with one or two V are not susceptible to vCJD, the infectious form of CJD.
Historically, since 1991 this SNP has been associated with risk for sporadic Creutzfeldt-Jakob disease, with homozygotes of both types apparently at increased risk compared to heterozygotes.[PMID 1677164]
More recently, this SNP has been related to long-term memory with (A;A) and (A;G) individuals recalling 17% more words than (G;G) individuals at 24h following learning.[PMID 15987701]
[PMID 18423780] A further study of 12 individuals of each of the 3 possible genotypes showed that at both 30 minutes and 24 hour time lags, correlations between retrieval-related brain activity and retrieval success were negative for (G;) homozygotes (the more activity, the worse retrieval success), while correlations showed no significance or were positive for (A) homozygotes and heterozygotes. These findings suggest that the rs1799990 SNP affects neural plasticity following learning at a time-scale of minutes to hours.
[PMID 16315279] rs1799990(A;G) heterozygotes were significantly overrepresented (age-adjusted odds ratio, 8.47) in 39 individuals with primary progressive aphasia (PPA), a rare condition of unknown cause, compared to 400+ controls.
Comments
Post a Comment