Cannibalism used to be very popular amongst the Fore tribes of Papua New Guinea. During the funeral proceedings the dead body would be dismembered and organs, specifically the brain, would be fed to the people in the tribe. Yum! As the brain eating continued, an epidemic arose killing off 2% of the tribe each year. The epidemic was driven by kuru, a neurodegenerative condition, which affects the brain and nervous system. Similar to Creutzfeldt-jakob disease, this condition comes about when there are malformations in the prion protein.
There are three stages to kuru, each of which involve specific symptoms. The ambulant stage demonstrates symptoms such as slurred speech, decreased muscle control and involuntary quivering movements. The sedentary stage, as the name suggests, shows extreme loss of muscle coordination (ataxia, which we know all about), as well as sporadic laughing outbursts (this is why the disease was known as the laughing sickness amongst the Fore people). In the terminal stage of kuru, the affected person has severe ataxia, is unable to speak or swallow, and they die shortly after. The cerebellum is one of the primary targets of kuru, and as we have already learned in our classes, it is responsible for interpreting a large amount of neural information producing smooth ongoing movements.
Something interesting that I found while reading about kuru, however, is that after generations of these cannibalistic rituals and eating brains, a gene allowed people of the Fore tribe to be resistant to prion diseases. Heterozygosity on codon 129 of the prion protein is associated with this protection. Essentially, while the epidemic was at its peak, a gene, already present in the population was chosen for due to its genetic advantages and more people began to display the mutation that would protect them against kuru and other related neurodegenerative diseases. So...although I titled this article "eating brains can protect you", it is important to note that eating brains was not what caused the mutation, but made the mutation more prominent amongst Fore people!
article: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4043168/
Chrystal,
ReplyDeleteI loved this read; super fascinating! The one thing I find exceptionally interesting is that the article you reference discusses cannibalism as a means of acquiring a mutation that protected people from the kuru disease. I found an article that offers a counterargument: stating, in effect, that cannibalism is cause of the kuru outbreak. It even mentions that due to the 1959 ban of cannibalism, no kuru diagnoses have been made. Your referenced article is written 6 years after mine; I wonder if our understanding of kuru and its cuase have changed?
Reference:
http://www.pnas.org/content/105/10/3885.long
That is super interesting! I did read a few articles on the subject since it was so interesting and it was clear that various researchers thought the epidemic was caused due to these rituals but the mutation itself was not. I did also find that with a decrease in this ritualistic proceedings there have been hardly any kuru cases, although, a blog I read said that because this disease can remain in a family for generations, that very few cases are still seen. There have been so many articles written on this, and I, like you am wondering what the differences are now in regards to this disease.
DeleteVery interesting, team! I had to investigate for myself this “which came first” predicament and found research (from 2003) comparing the codon 129 differences of the human prion protein gene (PRNP). They explored four world populations: European, African, Japanese, and Fore. Interestingly, each population, except for the Japanese population, had a significantly high frequency of the codon heterozygosity, with frequency within the New Guinea population being the highest. This led researchers to conclude that heterozygosity was in fact selected for over generations for its protective attributes; they suggest that a randomly infected brain was first consumed within the New Guinea population, causing the prion disease to propagate via their funeral practices.
ReplyDeleteBoth arguments are simultaneously correct.
Here is a link to the reference:
ReplyDeletehttp://www.cell.com/cell-reports/abstract/S2211-1247(15)00521-5?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2211124715005215%3Fshowall%3Dtrue