DNA screening - Irish Setters GPRA (rcd-4)
These registers have been put on the Kennel Club website.
They are updated on the 1st of each month.
The following Irish Setters have been DNA tested for GPRA (rcd-4)
The test distinguishes between clear, carrier and affected dogs. Clear dogs have no copies of the mutant gene responsible for the condition and will neither develop the condition nor pass the gene on to their offspring. Carrier dogs have one copy of the normal gene and one copy of the mutant gene; they will not develop the condition, but will pass a mutant gene on to approximately half of their offspring. Affected dogs have two copies of the mutant gene that causes the condition and will develop the disease.
Tables listing clears and carriers (in PDF format) are available from the following links:
The Irish Setter Club of Belgium www.irishsetterclub.be.
The Irish Setter Club of the Netherlands - www.iersesetterclub.nl.
The Irish Setter Club of Finland - www.kkk-hhs.fi/Irkut/IndexIrkut.htm
PRA rcd4 RESULTS
Below is a list of Irish Setters which have been tested for the inherited disease PRArcd4. These names have been kindly provided by owners who wish to have their results published. Please note this list is NOT exhaustive and simply reflects the results we have been given.
New DNA testing scheme for Irish Setters
Following consultation with the Irish Setter Breed Health Committee, the Kennel Club has recently approved a new official DNA testing scheme for PRA (rcd-4) in the breed.
This test is offered by the Animal Health Trust and further details can be obtained by emailing firstname.lastname@example.org.
Copies of all future test certificate results issued by the AHT will be sent directly to the Kennel Club, where the test result will be added to the dog’s details on the registration database. This will trigger the publication of the test result in the next available Breed Records Supplement, and the result will also appear on any new registration certificate issued for the dog and on the registration certificates of any future progeny of the dog.
Owners who have already had their dog(s) DNA tested for this condition can send copies of the test certificate into the Kennel Club and the data will be added to the dog’s registration details. In addition, if the owner includes the original registration certificate for the dog (not a copy) then a new registration certificate will be issued, with the DNA result on it, free of charge. Please send the DNA test certificates to:
The Health & Breeder Services Department
The Kennel Club
1 – 5 Clarges Street
Alternatively, copies of DNA test results can be emailed to email@example.com.
For further information on this new scheme, please contact Professor Jeff Sampson at firstname.lastname@example.org.
For all recent articles and updates please visit our PRA rcd4 page.
*** UPDATE ***
Following a meeting between Professor Ed Hall, Chairman of the Breed Health Committee, Dr Cathryn Mellersh. Canine Genetics Research Group Leader from AHT and Dr Jeff Sampson, Genetics consultant to the Kennel Club we have been advised by Ed Hall that in addition to the 7 dogs which have been identified with PRA rcd4 there are 3 more having "mid-onset" PRA and which do not have rcd1 or rcd4.
Any Irish Setter with suspected sight problems can have DNA testing free-of-charge if the sample sent to the AHT is accompanied by a certificate from a veterinary ophthalmologist confirming PRA ( Progressive Retinal Atrophy).
To get your dog tested for PRA by an ophthalmologist you will need to see your vet first and ask for a referral to an eye specialist.
Statement from The Animal Health Trust
Progressive Retinal Atrophy in the Irish Setter
Progressive Retinal Atrophy (PRA) is a well-recognised inherited condition that many breeds of dog are predisposed to. The condition is characterised by bilateral degeneration of the retina which causes progressive vision loss that culminates in total blindness. There is no treatment for PRA, of which several genetically distinct forms are recognised, each caused by a different mutation in a specific gene. The various forms of PRA aretypically breed-specific, with clinically affected dogs of the same breed usually sharing an identical mutation. Clinically affected dogs of different breeds, however, usually have different mutations, although PRA-mutations can be shared by several breeds.
A mutation for an early-onset form of PRA, known as rcd1, was identified in Irish Setters as long ago as 1993, and is well-documented to affect dogs from a few weeks of age. More recently dogs have been identified with a seemingly different form of PRA that affects dogs later in their lives and is known to be different from rcd1. This alternative form became known as“LOPRA” – for Late-OnsetPRA. Unlike rcd1, where all dogs became affected at almost exactly the same age the age of onset of dogs with LOPRA varied, from a few years of age (2-3 y) up to old age (10-11 y). It was unclear whether these dogs all shared the same form of PRA or whether there were genetically distinct forms of PRA segregating in this breed.
In 2011 geneticists working in the Kennel Club Genetics Centre at the Animal HealthTrust identified a recessive mutation that is associated with the development of LOPRA in theGordon Setter. Owners of Gordon Setters with LOPRA report that their affected dogs develop night blindness in the first instance, which is indicative of a rod-cone degeneration, so we have termed this mutation rcd4(for rod-cone degeneration 4)to distinguish it from other, previously described, forms of rod-cone degeneration.
Following our work with rcd4 in the Gordon Setter we have found some Irish Setters that have been diagnosed with PRA also carry two copies of the rcd4 mutation. As a result the AHT will make the rcd4 DNA test available to Irish Setters,from August1st2011. The DNA test we are offering examines the DNA from each dog being tested for the presence or absence of this precise mutation and is thus a ‘mutation-based test’ and not a ‘linkage-based test’.
Other Forms of PRA
The research we have carried out to identify the rcd4 mutation has revealed that there are at least three forms of PRA segregating in the Irish Setter; rcd1,rcd4 and an additional, third form, that has yet to be identified. We know there is a third form of PRA because of the ten dogs with LOPRA, whose DNA we have been sent to analyse, only 7 have two copies of the rcd4 mutation. The remaining 3 dogs do not carry either the rcd1 or rcd4 mutations,meaning their PRA must be due to another, as yet unidentified, mutation. There is some evidence that this third form of PRA has, on average, an earlier age of onset than rcd4, but we need to examine more dogs before we can be confirm this.
The age at which dogs with the rcd4 mutation develop PRA seems to vary and we know about dogs as young as 4 and as old as 10, that have been diagnosed with LOPRA, and that carry two copies of rcd4 mutation. But it is important to remember that the age at which a dog is diagnosed with PRA can vary according to circumstances,and is not necessarily the same age at which it started to develop PRA. For example, a dog whose PRA is detected at a routine eye examination will have an earlier age of diagnosis than a dog whose PRA was only detected once it started to lose its sight. It is also possible that the dogs that have developed PRA very early also carry the mutation for the third,unidentified, form of PRA (as well as rcd4) and it is this ‘mid onset’ mutation that has caused them to develop PRA at a relatively young age. More research will be required to understand the variability in age of onset more fully.
Our research indicate srcd4 is a common form of PRA among Irish Setters and the development of this test therefore enables breeders to slowly decrease the frequency of an important formof PRA in their lines. However,because we know that at least one other form of LOPRA exists within the breed,we cannot guarantee that any dog will not develop PRA, even if they are clear of the rcd4 mutation.
Rcd4 DNA Test
Breeders using the rcd4 DNA test will be sent results identifying their dog as belongingto one of three categories. In all cases the terms ‘normal’ and ‘mutation’ refer to the position in theDNA where the rcd4 mutation is located; it is not possible to learn anything about any other region of DNA from the rcd4 DNA test.
CLEAR:these dogs havetwonormal copies of DNA. Clear dogswill not develop PRA as a result of the rcd4 mutation, although we cannot exclude the possibility they might develop PRA due to other mutations they might carry that are not detected by this test.
CARRIER:these dogs have one copy of the mutation and one normal copy of DNA. These dogs will not develop PRA themselves as a result of the rcd4 but they will pass the mutation on to approximately 50% of their offspring .We cannot exclude the possibility that carriers might develop PRA due to other mutations they might carry that are not detected by this test.
GENETICALLY AFFECTED:these dogs have two copies of the rcd4 mutation and will almost certainly develop PRA during their lifetime. The average age of diagnosis for dogs with rcd4 is 10 y, although there is considerable variation within the breed.
Ou rresearch has demonstrated that the frequency of the rcd4 mutation in IrishSetters is high and approximately 30-40% of dogs might be carriers. The mutation is recessive which means that all dogs can be bred from safely but carriers and genetically affected dogs should only be bred to DNA tested, clear dogs. About half the puppies from any litter that has a carrier parent will themselves be carriers and any dogs from such litters that will be used for breeding should themselves be DNA tested prior to breeding so appropriate mates can be selected. All puppies that have a genetically affected parent will be carriers.
It is advisable for all breeding dogs to have their eyes clinically examined by a veterinary ophthalmologist prior to breeding and throughout their lives so that any cases of PRA caused by additional mutations can be detected and that newly emerging conditions can be identified.
Irish Setter Breed Clubs Health Coordinators Committee
Late Onset Progressive Retinal Atrophy (LOPRA)
Following the discovery of Irish setters clinically affected with LOPRA in association with two copies of the rcd-4 gene (i.e. homozygous), so far the following six dogs (in alphabetical order) have been identified as affected.
· Joben Midnight Memories
· Joben Midnight Moments
· Konakakela Red Admiral at Ixia
· Millcroft the Moon's Shadow
· Starchelle Buddy Holly
· Wickenberry Capsicum
These names are being published with the permission of their owners/breeders in a spirit of openness in order to alert responsible owners and breeders and to prevent the propagation of unfounded rumours.
We await an announcement from the Animal Health Trust on when the rcd-4 test will be made available.
Professor Ed Hall
Chairman, Irish Setter Breed Clubs Health Coordinators Committee
A statement from the Irish Setter Breed Clubs Health Coordinators Committee concerning
Late Onset Progressive Retinal Atrophy (LOPRA)
Recently, DNA samples from Irish setters diagnosed with Late Onset Progressive Retinal Atrophy (LOPRA) have been submitted to the Animal Health Trust for genetic analysis. So far several dogs have been diagnosed with two copies of the rcd-4 mutation (i.e. homozygous). This means these dogs are clinically affected with a condition that has previously been described in Gordon setters.
The Animal Health Trust is hoping to release a DNA test for rcd-4 in Irish setters in the near future and when it is available the scale of the problem in the breed can be assessed and an appropriate strategy to eradicate the condition can begin. Until that time the Committee advises against panic and ill‑informed rumour.
Whilst the recognition of LOPRA in the breed is a serious and unwanted development, we should take heart that previous genetic problems (e.g. PRA rcd-1, CLAD) in the breed have been conquered by dedicated breeders implementing controlled breeding schemes, and there is no reason to doubt an eradication programme, when launched, will be successful.
Professor Ed Hall
Chairman, Irish Setter Breed Clubs Health Coordinators Committee
AUTOSOMAL RECESSIVE GENES
Certain inherited conditions are caused by autosomal recessive genes that are faulty and this means that puppies need to inherit one copy of the faulty gene from each parent to develop the condition; both dog and bitch puppies can be affected.
If it has no copies of the faulty gene it is clear and can never develop the disease nor pass on a defective gene. If it only receives one copy it will be a carrier and will never develop the disease, but will pass on the gene to about 50% its offspring. The difficulties arise firstly in identifying those dogs that are carriers, because if you mate carrier to carrier, bearing in mind they show no signs of the disease or of being a carrier, then about 25% of the offspring will be affected, about 50% will be carriers and about 25% will be clear. Without a DNA test carriers can only be identified if they produce affected puppies and only then if mated to another carrier and by then, particularly if the disease is one that has a late onset, many puppies could be carriers waiting to be mated to other carriers. The second difficulty is identifying affected stock if the condition does not occur until the dog is relatively old.
With a DNA test breeders know for certain whether a dog is affected, carrier or clear and that will help them make informed decisions. Breed Clubs, in conjunction with KC, are able to formulate a control scheme that is individually tailored to their breed.
Each DNA test is specific to a particular mutation and will not establish whether or not a puppy will develop another condition.
CLEAR: has two normal genes so will never develop the specific condition for which the test is designed. It can only pass on a normal gene to its offspring.
CARRIER: has one faulty gene and one normal gene and will never develop the condition for which the test is designed but will pass on either a normal or faulty gene to its offspring: approximately half of its progeny will inherit the mutant gene.
AFFECTED: has two copies of the faulty gene and will develop the condition for which the test is designed. It can only pass on the faulty gene to its offspring.
By establishing the genetic status of a dog and bitch before mating it is possible to predict the probability of the clear, carrier or affected pups in that mating.
Any mating that produces an affected pup should be avoided so there should be no matings of carrier to carrier, carrier to affected or affected to affected. By avoiding these combinations then no more puppies affected with the condition for which the test is designed need be born.
Clear to clear is the ideal mating as it will not produce affecteds or carriers but this may not be possible immediately after a test becomes available as it will depend on the number of carriers within the breed.
However, always providing one parent is clear, other combinations can be used that do not produce affecteds. Clear to carrier will produce a combination of clears and carriers and the puppies will need to be tested if they are going to be used for breeding. Clear to affected will produce all carriers and this combination is best avoided. By careful selection of parents and only using a carrier with other desirable characteristics and of particular merit to the breed it is possible to retain breed characteristics and, over the generations, breed out carriers. If there are many carriers in a breed then it would be inadvisable to discount them as the subsequent breeding pool could be greatly diminished.
It is important to realise, with the exception of affected to affected and clear to clear, the percentages are only statistical and will vary from litter to litter.
In Irish Setters we have 2 established DNA tests and one very recently available.
Both the PRA rcd1 and CLAD tests have been used effectively and it appears that both conditions have been eradicated from the breed in Kennel Club registered stock in the UK. The latest test for PRA rcd4 has very recently been made available to breeders and there is no reason why the same success should not be had with this latest test.
Sunday, 31 July 2011 21:41
PRA rcd4 (LOPRA) Some questions answered
(please read this alongside the AHT announcement)
I have been asked a number of questions on this subject, and the following answers try to throw light on the current situation.
1.What does it mean to be genetically affected but not yet clinically affected by PRA rcd4?
Unlike PRA rcd1 and CLAD, which can be seen in very young puppies, PRA rcd4 may not be visible to the owner or even to the vet or ophthalmologist until later in life. The dog is genetically affected from birth and a DNA test for PRA rcd4 will show this; however the clinical signs of deteriorating eyesight will not be present until sometime later in life and, in fact in a few cases, may never occur. The dog has the defective genes from birth although the clinical signs are not present and this must be understood when considering a breeding programme.
2.Explain the meaning of “homozygous for PRA rcd4”.
This is frequently referred to as having “two copies of the mutant gene” and thus being genetically affected.
In layman’s terms this means that the defective gene is inherited from both parents.
If the defective gene is inherited from only one parent the dog will be a “carrier” of the condition which means the defective gene can be passed to the offspring but this dog will never have this condition. This is typical of a recessive mutant gene and most of us are familiar with it in PRA rcd1 and CLAD.
3.Remind me what happens if an affected dog is mated to a clear.
AFFECTED to CLEAR >>>>>>>>>> 100% CARRIERS
AFFECTED to CARRIER >>>>>>>>> 50% AFFECTED; 50% CARRIERS
CARRIER to CLEAR >>>>>>>>>>>> 50% CARRIERS; 50% CLEAR
CARRIER to CARRIER >>>>>>>>>> 25% AFFECTED; 50% CARRIERS; 25% CLEAR
4.How do we know there might be 30-40% of dogs in our breed that are carriers?
A random check was performed on a large number of DNA samples stored at the AHT and this provided the information. The large number of samples used by the AHT means that the proportion of carriers for that sample is likely to reflect the proportion throughout our breed.
5.Will we be told the individual results from this test run?
No. The AHT have permission to use the samples stored for research purposes i.e. in the development of a new test, and to provide a statistical analysis of the results but not to provide individual dog’s names or results.
The way forward is to test the dogs you own now, particularly your breeding stock, and to move forward from this.
The advice so far is to avoid producing genetically affected puppies – if you find you have an affected dog or a carrier with which you wish to breed only breed to a clear dog.
6.What do we know about another form of LOPRA that exists in the breed?
We know there is a third form of PRA in the breed as 3 dogs have been clinically identified as having PRA but their DNA shows that they do not have PRA rcd1 or PRA rcd4. It probably occurs at a younger age then PRA rcd4. It may be the cause of blindness in the younger dogs that also have the PRA rcd4 mutation. Further research will be needed to find the mutation if more cases are found.
7.How many dogs so far (July 2011) are homozygous for PRA rcd4?
We only know of 7, 6 of which have been named by their owners. I understand that there were very few in the research run but we have not been given further information on this. I do, however, have a personal story to tell as a result of this research run.
My experience has been with my old dog, Willow (Kirkavagh Karamita of Follidown), until now referred to in newsletters but not named because of the uncertainty involved in her condition at the time. During the research she was found to have two copies of (i.e. homozygous for) the PRA rcd-4 mutation and she was blind and she was 13 years old. This seemed to confirm the research programme but on examination by two highly respected ophthalmologists she was found not to have LOPRA. Her blindness was caused by typical problems of old age – some cataract and sclerosis of the lens. If she had lived longer she may have developed LOPRA but, very sadly, she died in April. ( Incidentally, she coped very well in her familiar environment with her blindness but did need extra help and consideration because of her condition.)
Most of you will have read about her already but it provides an important case study and a good reason not to panic if the DNA test shows your dog to be homozygous for PRA rcd-4. Your dog may never go blind despite having the genetic mutation.
ISAE Health Representative.