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n September, I had the opportunity to attend the 7th Tufts
Canine and Feline Breeding and Genetics Conference. This
biennial conference is organized by Jerold Bell, DVM, clini-

cal associate professor at the Tufts Cummings School of Vet-
erinary Medicine. In Dr. Bell’s words, the “purpose of the
conference is to foster communication between researchers,
practicing veterinarians, parent clubs, breeders, owners and
genetic testing centers.” This conference is more informative
than others because the speakers have to reach an eclectic
audience. These four presentations are relevant to PBGVs.

Primary Glaucoma in Dogs:Relieving the Pressure

through Genetic Investigation and the Development of
DNA Tests. The highlight of the conference for me was a
talk by Cathryn Mellersh, PhD, head of Canine Genetics at
the UK’s Animal Health Trust (AHT). If you read Saber Tails
and PBGVCA emails, the name Cathryn Mellersh should be
familiar to you — she is the researcher who identified the
gene defect that leads to primary open angle glaucoma
(POAG) in PBGVs. Thanks to her research, the AHT has a
DNA test that can determine whether your PBGV is clear of
POAG (will not develop POAG, will not pass the disease to
offspring), a carrier (will not develop POAG but can pass the
defective gene to offspring), or affected (will develop POAG
at some point, will pass the defective gene to all offspring).
As of October 2015, 900 PBGVs worldwide have been tested.
Of the 266 United States dogs tested, 147 were clear, 109 
carriers and 10 affected. The high number of carriers in the
United States is an issue Dr. Bell will discuss at the 2016
PBGVCA National Specialty health seminar.

Dr. Mellersh first gave some background information on

glaucoma. Glaucoma is a painful and blinding condition
that occurs when the normal outflow of fluid in the eye is
impaired. The resulting high pressure damages the retina
and optic nerve. Unfortunately, glaucoma is a disease that
responds poorly to treatment and often requires removal of
the affected eye. Glaucoma can occur secondarily to other
eye conditions, such as inflammation, dislocated lens, a
tumor or an injury. As PBGV lovers, we are more concerned
about primary glaucoma, an inherited condition that affects
more than 40 breeds. The most common form of primary
glaucoma is called primary closed angle glaucoma (PCAG).
The gene defect (or defects) that leads to PCAG has not been
identified. PCAG typically occurs in dogs with a structural
defect in their eye that leads to abnormal fluid drainage. It is
good practice to have a veterinary ophthalmologist evaluate
your dog’s eyes using a gonioscope to determine whether it
might be predisposed to developing PCAG. If the drainage
angle closes, there will be rapid onset of pain with the 
potential for irreversible blindness. Any sudden visible
change in your dog’s eye is a medical emergency requiring
an immediate trip to the vet! Until recently, PCAG was
thought to be a non-progressive disease. That is, it was 

believed if a young dog was cleared by gonioscopy, the test
did not need to be repeated. However, new studies indicate
PCAG is progressive and gonioscopy should be repeated;
testing every three years is recommended in the UK.

The less common form of primary glaucoma is the slowly

progressing POAG. POAG is known to affect Norwegian
Elkhounds, Beagles and our beloved PBGVs. POAG in Beagles
and Elkhounds is the result of different mutations in the
same gene, called ADAMTS10. PBGVs are unique, as we well
know, and don’t have any mutations in ADAMTS10. Dr.
Mellersh said the genetic mutation that leads to POAG in
PBGVs was a type that was very difficult to find. PBGVs with
POAG have a large rearrangement (an inversion) in the DNA
encoding a protein called ADAMTS17. This rearrangement
causes the protein to become completely dysfunctional. 

What is ADAMTS17? It is the 17th member of the very

large ADAMTS protein family. In the biomedical research
community, the ADAMTS family is a very hot topic. Members
of the family have been shown to play roles in arthritis, 
angiogenesis, blood clotting, embryonic development and
connective tissue disorders. ADAMTS stands for ‘A Disintegrin
And Metalloproteinase with Thrombospondin motifs.’ Aren’t
you glad you asked? Disintegrin is a protein that inhibitsblood
clotting. Metalloproteinase means a zinc-containing enzyme
that chews up other proteins. Thrombospondin is an 
inhibitor of angiogenesis (blood vessel development). 
Remember the Chimera from Greek mythology that had 
the body of a lion, the heads of both a lion and a goat, and 
a tail of a snake’s head? The ADAMTS proteins are like the

Chimera. We can name their separate parts, but we don’t
know what the protein as a whole does.

Interestingly, mutation of the ADAMSTS17 gene in 

humans is responsible for Weill Marchesani syndrome, a rare
disease that affects eyes and also leads to short stature
among other problems. Dr. Mellersh hypothesizes that the
ADAMTS17 mutation might lead to slightly smaller stature
in PBGVs with the mutation. It is possible that, as Petits
were selected, some of the smaller stature in the breed was
due to mutation in this gene. If a breeder wanted this
smaller stature in their line, this mutation would spread in
the PBGV population. That might explain why carriers of
the POAG mutation are so prevalent in the population.

There was also new information that will be of interest 

to our Basset Hound friends. As part of a study examining
Bassets for closed angle glaucoma, Dr. Mellersh found three
young Bassets with POAG. The affected Bassets also have a
mutation in the ADAMTS17 gene, although the mutation is
not the same as in PBGVs. Screening has shown that 16 
percent of Bassets in the UK are carriers of this mutation.
They have developed a DNA test for the Basset mutation,
but breeders are not taking advantage of the test. This is
likely because the test identifies a mutation for a disease that

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www.pbgv.org

Winter 2015   

I Saber Tails

I  

PBGV Health Watch  

by Laura Liscum on behalf of the PBGVCA Health Committee

The 2015 Tufts Canine/Feline Breeding and Genetics Conference

Remember the Chimera from Greek mythology that had the body of a lion, 

the heads of both a lion and a goat, and a tail of a snake’s head?