Persistant Hyperplastic Primary Vitreous
The Canine Genetics Team is currently investigating Persistent Hyperplastic Primary Vitreous (PHPV) in the Staffordshire Bull Terrier. PHPV is a congenital eye condition caused by the retention of elements of the foetal vascular supply to the lens. The condition results in variable amounts of fibrovascular plaque on the posterior lens capsule and possible posterior cortical cataract. This is sometimes accompanied by bleeding into the back of the eye or into the lens. PHPV is inherited in Staffordshire Bull Terriers although the precise mode of inheritance is unknown.
We have recently conducted a whole genome scan using DNA samples from 24 dogs affected with PHPV (cases) and 23 unaffected dogs with clinically confirmed clear eyes (controls). We used a high-density scanning array to genotype around 174,000 markers spanning the whole genome and analysed the data for regions of the genome that were consistently shared between the cases but different in controls. This would indicate a region that harboured a mutation with a role in the development of PHPV.
Unfortunately, we did not identify any regions of the genome that were strongly associated with PHPV, indicating that the disorder is unlikely to be simple and caused by a single mutation with a recessive mode of inheritance. The most likely explanation therefore is that PHPV is either caused by a single mutation with a dominant or co-dominant mode of inheritance, or is a more complex condition with perhaps several genes involved.
We will preserve the current dataset and seek to collect an additional set of 24 cases and 24 controls which we can then examine using the same methods as above. We will then formally combine the two datasets to increase our power to identify mutation(s) associated with PHPV.
Q. Which dogs can contribute to the AHT’s PHPV research?
A. There are two types of dog that are useful to our research:
i) Staffordshire Bull Terriers that have been diagnosed as AFFECTED with PHPV.
ii) Staffordshire Bull Terriers that have had a current eye examination by a veterinary ophthalmologist and are CLEAR of PHPV.
For more information about PHPV in Staffordshire Bull Terriers, you can download our Frequently Asked Questions.
If you would like additional information regarding our PHPV research in the Staffordshire Bull Terrier please contact Sally Ricketts at firstname.lastname@example.org.