Archive for the ‘Backcross Project in France’ Category
The Backcross Project in France by D. Vincent
October 23rd, 2009
Veterinarian and vice-president of the French Dalmatian Club I acquired my first Dalmatian by chance when beginning my studies in Toulouse and I have remained faithful to the breed ever since.
It is by personal interest that, convinced of the value of the Backcross project, I have recently acquired Stocklore Forrest Windsong (“ WENDY”)- bred in the USA by Dr Robert Schaible.
The backcross project is supported by Dr Danika Bannasch, who discovered the gene SLC2A9, and Dr Carl Osborne the world renowned urologist..
To defend a breed is an ethical challenge!
To defend a breed implies to correct defects within the breed with priority given to any invalidating genetic problems.
During the founding of a breed, over selection for certain criteria can lead to acquiring unwanted defects..
In the Dalmatian deafness, associated with extreme white piebald (A.G.Searle 1968 Comparative genetics of Coat Colour in Mammal) , and uric acid stone formation (gene SLC2A9) are there as reminders of this fact.
Surely it is our duty is to correct these “ errors”?
According to Dr Bartges (2006)and other researchers it would appear that approximately 25% of male Dalmatians are affected. Surgical intervention is not rare and in some cases euthanasia is necessary- usually by owners who cannot afford the on-going expense of management. .
Urolithiasis is accentuated by an inappropriate diet or life style. The prevention of stones can impose a way of life which many owners cannot or do not want to follow and as a result the dog suffers.
The genotype of the one Pointer used in 1973 is now less than 0.05% at the 13th generation.
This prompted Dr Osborne to remark “This is a small price to pay for the battle against stone disease”.
Pursuing the project by out-breeding will result in an ever increasing diminution in the amount of residual Pointer DNA.
According to the president of the Pointer Club of France, the Pointer has been successfully used for backcross in other breeds.
Recent genetic studies based on molecular markers (Parker 2007 & Leroy 2008) have been able to group breeds according to their common origins. These studies show that the Dalmatian and the Pointer belong to the same group.
We now know that gene therapy, which is a way of introducing a gene by molecular
manipulation, is not a successful route and so it is logical to use a proven & trusted method- i.e .that of re-introducing a gene by cross-breeding followed by backcrossing to the breed needing improvement
Arguments against the Backcross Project can be negated.
A….The formation of stones is dependant on absence or diminution of inhibiting factors as well as presence of promoting factors.
The support of Dr Carl Osborne is, of course, indispensable. His many books and articles on this subject are of enormous value.
The basis of the problem is the oversaturation of the urine by urate crystals.
Factors which favour the formation of stones.
An inappropriate diet.
Inadequate water intake.
Lack of opportunity to empty the bladder. Urinary stasis
How stones are formed- 3 theories.
- Spontaneous precipitation due to oversaturation.
- Nucleation of crystals around a protein matrix. Certain proteins, such as uromucoides, Tamm Horsfall protein) can be the first link in stone forming, but this is not always found and it could be cell debris which performs the same role.
- A failure of the inhibiting factors. Certain substances (such as nephrocalcines, pyrophosophates, citrates etc., which inhibit the nucleation, can be absent, but they are numerous and it is difficult to discern which is the real culprit. In addition some glycosaminoglycanes prevent the adhesion of crystals to the mucosa and these are present in insufficient quantities in some stone-forming Dalmatians.(Carvalho, Urology 2003)
In conclusion – the primary factor is the oversatuaration of the urine with urates and THIS is what we have to combat. First things first!
B…It is impossible to eradicate the problem using the single lua line.
There is no question of eradicating the ailment immediately. We should introduce the lua gene with moderation and rest vigilant.
It is time now, in my opinion, to mate the lua’s with European Dalmatians and re-establish a good genetic variability.
To continue the project with line –breeding, especially with the lua UU has limits.
We now need to work at an international level to give substance to the courageous initiative of Robert Schaible.
C… The risk of introducing new hereditary diseases.
The consanguinity of the lua line is so high that it seems probable that any recessive genes would have been expressed during the 13 generations bred since 1973. In the USA, as in France, the Pointer has an excellent status with regard to genetic diseases.
Pointers do not suffer from hip dysplasia-90% are free. Hypothyroidism and retinal atrophy are very rare. There is no deafness or cardiomyopathy.
D….One opponent has said “Do we abandon the characteristic spotting of the Dalmatian to resolve a problem which affects only a minority of the breed?
Are not construction, the character and the movement the main qualities of the breed?
The spots of lua’s are sometimes smaller than the hua’s but they remain within the Dalmatian standard. The current fashion in the ring seems to favour heavily spotted dogs, but this can change!
Some have “frosty” spotting that is there is a halo effect caused by an undefined edge to the spots, but this diminishes with age. We have seen this type of spotting in the past and we know it can be improved by selection. A few lua’s have white hairs in the spots on the head- again selection will reduce this in time..
According to Dr Bannasch there could be a relationship between the gene SLC2A9 and the search for more distinct spotting. The control of the speed with which the pigment cells migrate is likely due to one or more genes which are in a different locus but close to the SLC2A9 gene. .
E…Lua Dalmatians will have upright shoulders.
The Pointer standard states “the shoulder is long and oblique”
CONCLUSION
A large proportion of the members of the American Kennel Club recognize the importance of the Backcross project and with wise people behind it this could be a sign post to the future.
The production of lua dalmatians out of or by “ foreign” Dalmatians will allow diffusion of the gene without the risks associated with consanguinity.
It could be of value to test a sample of Dalmatians in each country from lines which have no history of urolithiasis to see if the “wild” gene U exists in Dalmatians outside the lua line. Indeed Dr Bannasch has only tested 300 Dalmatians. The French Club plans to test a certain number in the near future.
Dominique VINCENT
August 11th 2009.
PARIS.
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