National Prion Clinic


Human genetics

This work is directed to understanding how our genetic makeup influences our susceptibility to prion disease. Unit scientists demonstrated in 1991 a very powerful genetic susceptibility factor for sporadic and iatrogenic CJD. There are two common forms of the human protein gene that in turn instruct the body to make two different normal forms of the protein. All proteins are made up of chains of building blocks known as amino acids, and the normal human prion protein gene is formed from a chain containing 253 of these. However, the amino acid at position 129 is not always the same. In fact it can commonly be one of two types, either methionine (or M for short) or valine (V for short). As we all have two copies of this gene (one inherited from our mother and the other from our father) there are three possible combinations in the population: you can either be MM (if you inherited an M gene from both parents), VV (a V gene from both parents) or MV (an M from one parent and a V from the other). It turns out that being MV provides a high degree of (but not complete) protection from developing CJD. This effect is even more striking in variant CJD where, so far, all definite cases have been MM. One suspected case, in 2008, who did not have a post mortem, was MV. Examination of the brain tissue after death is the only way to get a definite diagnosis.

We have also been conducting studies across the whole genome (our entire genetic make-up) to identify other genes that might explain why some people and not others get CJD.

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