PNA Research Status
On Tuesday, January 11, 2005, at 05:52 AM, OBrien, Dennis wrote:
Regarding the research, here is where we stand. We have mapped the
gene responsible for PNA to the tip of the dog Chromosome 1. In
scientific terms, we have a locus: that is we know where the gene responsible
is located. Our intital mapping data told us that the PNA gene was
in an area that covered about 35 million DNA molecules and over a hundred
different genes. One of those genes was a prime candidate for the
PNA gene because it is a gene which is associated with a form of hereditary
Parkinson's disease in people. PNA and Parkinson's disease share a
number of similarities including the age of onset for the juvenile forms
of Parkinson's. We initially looked at that gene and found a difference
between the gene in the affected Kerry Blue Terriers and the normal Kerry
Blues. So we thought we had found the PNA mutation until we did the
final experiment to look at the same area of the gene in a couple hundred
normal dogs of other breeds and be sure that the mutation only occurred
in the PNA dogs. What we found was that this particular difference
in the gene also occurred in normal dogs. That doesn't mean that there
isn't a mutation elsewhere in that gene that is causing PNA.
We still think it is the most likely candidate, but we can't prove it yet
and science is all about proof.
So our next step was to try to refine our map to be sure we were barking
up the right tree before we continued to look at our candidate gene.
Our refined map narrowed the area where the PNA gene could be down to an
area 10 million DNA molcules long which contains 41 genes. So one
of those 41 genes is responsible and our Parkinson's gene is still one of
them. The difficulty is that the parkinson's gene is one of the largest
genes known (over a million DNA molecules long) which makes it very
difficult to work with. We continue to plug away at it, but need to
have some way of determining carriers now. So what we are currently
doing is developing a panel of the markers which told us that the PNA gene
was in this limited area for use as a test. Such a test (called a
haplotype test) is not as accurate as a test based on the specific gene
would be, but it will be pretty good. Certainly better than what's
been available until now!
Dennis O'Brien DVM PhD
University of Missouri
College of Veterinary Medicine
(573)882-7821
OBrienD@missouri.edu
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