Primary Lens Luxation(PLL)

PLL TESTRESULT

During 2009 a research team from University of Missouri, College of Veterinary Medicine in the USA discovered the gene mutation of PLL.  Shortly after an announcement was made from the Animal Health Trust in England saying that they had discovered the identical gene. A co-operation was established between the research teams and a decision was made to be jointly responsible for the publishing of this discovery. In September 2009 a PLL DNA test was made available for the public.

 

WHAT IS PLL?
Primary Lens Luxation is a well known problem among several breeds and Chinese Crested Dog is one of them. The lens is held in place by fibers called zonular fibres, similar with tiny threads. If the zonular fibres rupture or are damaged the lens could relocate within the eye and luxate. If this happens immediate care is needed from a veterinary eye specialist. A surgical operation removing the lens can save the dog from developing the very painful condition secondary glaucoma and blindness.

Normal eye (left picture) 1. Cornea 2. Normal lens 3. Glass body

Luxated lins (right picture) 4. Cornea 5. Luxated lens 6. Glass body

 

DNA test
The DNA test now offered by OFA and AHT will reveal your dogs DNA status concerning this precise gene mutation. The results of your dogs PLL gene status could be either CLEAR, CARRIER or AFFECTED.

CLEAR: The dog does not have this precise PLL gene mutation.

CARRIER: The dog has a single copy of this precise PLL gene mutation, the other copy of the gene is normal/clear.

AFFECTED: The dog has two copies of this precise PLL gene mutation.

This test is a so called “swabtest” and by that it means that saliva is collected from the inside of the cheek. It is important that the dog is isolated as instructed before testing. This is because no DNA from another dog should be present in the saliva and contaminate the sample. If you are interested in how the sample is obtained from our listed dogs we refer to each dog owner for that information. The test can be executed in the home by the dog owner or by a veterinarian if you wish to have the identity of the dog confirmed.

HERITAGE

The heritage is known as single recessive. BUT research has shown that there is a very small risk for carriers to develop PLL even though they only have the PLL gene mutation in a single copy. Research has also demonstrated that carriers that develop the condition are doing that considerably later then the affected dogs. Therefore carriers are seen as individuals with LOW RISK to develop PLL and the affected dogs are seen as individuals with HIGH RISK to develop PLL. Currently scientists have no explanation why and how this is possible considering the known heritage, but we hope for answers within the near future.

 

HERITAGE CLEAR / CLEAR BY DEFAULT – what does it mean?

This expression means that the dog is an offspring from a mating with both mother and father tested CLEAR. When the PLL gene is not present in the parents DNA it can’t be given to the offspring either and all offspring in such litter will be CLEAR. Therefore it is not necessary to test these offspring in order to know their PLL gene status.

Inheridation schedule

Colour code	Genetic	Symptom/ Inheridation
	Healthy Chinese Crested Dog Don't have the disease gene at all.	NORMAL/CLEAR Healty Chinese Crested Dog don't get PLL and cannot pass it further to offsprings.
	Hidden carrrier Has the disease predisposition in single set.	CARRIER Hidden carrier can in a few cases develop  PLL and can pass it further to the offsprings.
	Affected Chinese Crested Dog Has two copy's of the disease PLL gene.	AFFECTED Affected CCD will develop the disease PLL and always pass disease predisposition further to the offsprings.

 

 

Normal/Clear dog (green) mated with Normal/Clear dog (green)

 +

 

father/motherr

 

Offsprings 100 %

 

 

Normal/Clear dog (green) mated with Carrier (yellow)

 +

 

father/mother

 

Offsprings 50 % 50%

 

Normal/Clear dog (green) mated with Affected dog (red)

 +

 

father/mother

 

Offsprings 100%  

 

 

 

Carrier (yellow) mated with Carrier (yellow)

 +

 

father/mother

 

Offsprings 25 % 50%  25%

 

 

Carrier (yellow) mated with Affected dog (red)

 +

 

father/mother

 

Offsprings 50 % 50%  

 

 

Affected dog (red) mated with Affected dog (red)

 +

 

father/mother

 

Offsprings 100 %

 

 

Research has demonstrated that in some breeds affected with PLL as many as 45-50% of the population has tested positive as carriers for this precise PLL gene mutation. This means that it is not possible to eliminate carriers by selected breeding. If we do that we soon will have trouble with other gene defects caused by a too narrow breeding population. By breeding carriers against clear we will in a slow but safe way create a future population with less carriers and more clear dogs. This will of course take time and demand that we all test our dogs to obtain the DNA status for this precise PLL gene mutation.

TO OBSERVE:
In Sweden it is FORBIDDEN according to the animal protection laws and also according to the rules of the Swedish Kennel Club to breed a dog tested affected.

THE LIST
The PLL test has now been available for some time. crestednetwork.se decided in the beginning of 2010, to publish a voluntary list for the test results on Chinese Crested Dog, after recieving several requests from dog owners and breeders.

 

©  Copyright!

THIS LIST IS NOT ALLOWED TO COPY
crestednetwork.se has been given permission from the owner of the following dogs to publish their test results. They also have verified their results by sending us a copy of the laboratory report on each dogs test result and for that reason it is forbidden to copy and publish this information, however you are most welcome to link to our website.

ARE YOU INTERESTED IN REGISTERING YOUR DOG ON OUR LIST?
We only publish results at the dog owners request. The email result from the laboratory has to be sent with the request as verification. All results are interesting whether clear, carrier or affected.

Send your dog’s registration number, name and parents name and the email result from the laboratory to: pll_list@crestednetwork.se

We have no intention to point out or in some other negative way harm anyone with this list. We only want to objectively inform about the test results for the best interest of the breed. The list is not to be seen as complete but it still gives a good overview on the PLL occurrence in the tested dogs. We will have a wider knowledge of the situation by having more dogs on the list.

In addition to our list below there is also an official result list from OFA. Results are also listed at Chinese Crested Health Database. It is possible that more lists will be available or created in the near future. Swedish Kennel Club does not accept cheek swabs as a test method. Only blood samples are accepted and therefore these results will not be published by the Swedish Kennel Club.

LINK to OFAs result list:  Test result

LINK to Chinese Crested Health Database: http://www.crestedhealth.com/

crestednetwork.se

Testkits can be ordered from: AHT, Animal Health Trust,  England  http://www.aht.org.uk/genetics_pll.html OFA, Orthopedic Foundation for Animals, USA  http://www.offa.org/dnatesting/index.html

Source:

University of Missouri, College of Veterinary Medicine http://www.caninegeneticdiseases.net/GLX/mainGLX.htm

Animal Health Trust http://www.aht.org.uk/genetics_pllfaq.html