Scary diseases Part 2: Fatal Familial Insomnia (FFI)

When I was still in primary school, my parents would shove me in bed at 9 p.m sharp every night. I hated the fact that as a kid, I was supposed to go to sleep early, while they, the grown-ups, were able to stay up till late. Now, in university, I don't know what I wouldn't give to be able to sink in bed at 9 p.m. Instead, the present scenario seems to be to drink a mugful of black coffee at 9 p.m and work on that lab report due in twelve hours' time throughout the night. Yes everybody, my name is Khalil and I am an insomniac.

I hear you: university student addicted to caffeine and complaining about insomnia... the usual recipe for moaning. But believe me when I say that I'm happy with my "caffeine-induced insomnia" - especially when I inadvertently read about Fatal Familial Insomnia (FFI).

FFI is caused by prions. It is actually one of the number of diseases caused by prions, with Bovine Spongiform Encephalophathy (Mad Cow disease) being one of them. Think of prions as the perfect infectious agent out there. It is composed entirely of protein, is extremely small (less than 100 nm), resistant to disinfectants and irradiation and to cap it all, does not elicit an immune response in the body.

Prions are made of prion proteins (PrP) which exist in two isoforms: common PrP (the good isoform, shown below in purple) and Scrapie PrP (the misfolded isoform). Common PrP is expressed in the brain of healthy individuals and although its precise functions is unknown, it is thought to play a role in cell signaling. However, a mutation in Common PrP whereby the amino acid aspartic acid-178 is replaced by asparagine coupled to the presence of methionine at codon 129 results in a misfolded form of the protein: Scrapie PrP. In people suffering from FFI, this mutated form of the prion protein accumulates in the thalamus part of the brain, eventually destroys nerve cells there.

The thalamus is responsible for regulation of sleep and the consequent effects of prions in this area of the brain results in a severe inability to sleep: intractable insomnia. Other symptoms including dysautonomia, dementia and motor paralysis follow. Ultimately, the person dies within six months to three years after exhibiting the symptoms. There is no cure for prion diseases.

So now, if you'll excuse me, it's 9 p.m already and my "caffeine-induced insomnia" awaits. Better stick to this insomnia, don't you think?

References:

1. Ramachandran, Ramachandran. "Prion-Related
Diseases" emedicine, Medscape. September 21, 2009.

2. "Fatal familial insomnia, a prion disease with a mutation at codon 178 of
the prion protein gene" The New England Journal of Medicine. February 13,
1992.

3. "Spontaneous Generation of Prion Infectivity in Fatal Familial Insomnia
Knockin Mice" Neuron. August 27, 2009.

Image Credits: freeimageslive.com & wikimedia.org

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