Still a rare disease

prion by Todd Huffman

‘Wider impact’ of brain disease
[Via BBC News]

A new form of brain disease, similar to Creutzfeld-Jakob Disease, could affect more people than previously thought, researchers in the US say.

It had been thought that only people with one genetic profile were vulnerable to the prion disease VPSPr. But in an Annals of Neurology study, Case Western Reserve University experts found people with all three possible gene patterns are affected by VPSPr.  


It is a wider impact of a very rare disease. The headline made me think that we should really worry.

This particular form of the disease, VPSPr, is not caused by eating contaminated meat. The prion protein can come in two different forms, one with a valine (V) and one with a methionine (M) amino acid at a specific position. Since each of us has two copies, there are three combinations: VV, MM and MV.

Originally, only the VV variants seemed to result in disease. But recent work found other variants involved suggesting that this particular disease may be more complex than other Creutzfeld-Jakob Disease diseases.

We still do not know what the prion protein really does. The fact that a single protein can misfold, causing other similar molecules to misfold, in a cascade that can essentially destroy the brain is disconcerting. Such a devastating stochastic event would seem to be selected against unless its incidence is simply to small to have much selective pressure. In Britain, there have been about 1500 cases of all types in 20 years, while the worldwide incidence is about 1 in a million people.

Such a low probability that the protein will misfold suggests that there would be very low selective pressures on the gene.

In addition, CJD usually affects people well past the age of producing offspring, removing them even ore from selective pressures. Now, the variant affects much younger people and might be under much greater selection except it is even less likely to appear than CJD. In addition, changing our eating habits can essentially remove the disease.

I actually interviewed with Stanley Pruisner when I was looking for a post-doc in the early 80s. He was really interested in someone who had a lot of cloning skills to find the gene for the protein – they had recently isolated it. I was not interested in doing the same thing as a post-doc that I had done as a graduate student but it would have been really interesting to work in a lab doing work that resulted in a Nobel Prize.