So let’s talk a little bit about the gene
itself encoding this PrPc protein.
Remember I said it is a normal cell protein in you,
it is encoded by a gene, like all proteins are.
The gene is called prnp, so PrPc is encoded
by the prnp gene, it has a normal cellular
function. In animals we can give animals,
experimentally in the laboratory, these TSEs,
by inoculating them with homogenates of brains
from people who have died of the disease.
We don’t usually do this with people, we
will take a sheep with scrapie, or a cow with
BSE. We will grind up their brains, we inoculate
it into an animal like a mouse or hamster,
sometimes we can transmit the disease to another
species. So this is the basis for what I’m
going to tell you for the next few slides.
If you take a mouse, and let’s say you have
a mouse that developed the TSE for whatever
reason. You grind up its brain, you inject
it into another mouse, that mouse will develop
a TSE. However, if you delete the prnp gene
from that recipient mouse, and we can do this
genetically relatively easily, you can make
a knockout mouse recall for both copies of
the gene, remember we have two copies of most
of our genes, that mouse now will not develop
a TSE when you inject PrPsc right into its
brain. So the prnp gene is essential to develop
a TSE. Think about it, it makes sense, if
you don't have any PrPc protein in you, there's
no way that a little bit of PrPsc that you
acquire can cause disease, because it doesn’t
have any PrPc to convert to the pathogenic
protein. Now we can’t delete genes in people,
otherwise that would be one way of preventing
TSEs. But it could be that in us, we need
this prnp genes. So it is probably not a good
strategy. Alright, so now you need to remember
prnp is essential for a TSE.