British Bulldog AdamTs3 Gene
Gene Variant AdamTS3 [Airways Oedema Gene]
Respiratory problems are common in several dog breeds, and it is especially common for short-nosed breeds to have trouble breathing. Swelling of the airways makes this problem worse.
One of the MDBA’s strategies to deal with breathing problems for brachycephalic breeds is testing for the AdamTS3 gene variant, more commonly called the Airways Oedema gene. The Gene Variant AdamTS3 contributes to breathing difficulties by causing swelling (oedema) in the airways. It is most commonly found in British bulldogs, French bulldogs, and Norwich terriers, but it has also been found more rarely in other breeds.
The airways of dogs with two copies of this gene can be more significantly impacted than those of dogs with one copy or no copies of this gene.
Discovering the frequency of one or two copies of the adamts3 gene variant in MDBA-registered British Bulldogs.
Mandatory testing for this gene was introduced by the MDBA in 2020 for all British Bulldog breeding dogs to determine the number of dogs affected by the adamts3 gene variant in the MDBA gene pool for this breed. Based on studies at that time, there was little expectation that we would find any that did not have one or two copies of this gene. As a result, we located several dogs from different bloodlines that were not closely related to one copy of the gene variant. Each dog with one copy of the variant is identified, and pedigrees are tracked and analysed to look for common relatives.
Due to the high number of dogs with two copies in the MDBA British Bulldog gene pool, breeder members have been advised to use the status of their breeding dogs to direct their choices in their breeding programs. Whilst no dogs have been removed or prohibited from breeding in the gene pool, breeders were advised and encouraged to seek mates for their dogs with one or zero copies of this gene variant. This is a recessive disorder, and with no amount of testing of the parents, selecting a wider trachea and only using dogs with a better respiratory function grading will aid in reducing the incidence of the conditions associated with this gene variant in future generations. In fact, this may damage the breed more as dogs that fail these gradings are removed from the gene pool, thus impacting genetic diversity more when, if an affected or carrier dog is mated to a zero-copy dog, no puppies will be affected.
Litters cannot be registered unless the status of each parent is known, except for semen that was stored before the start of the program. In that case, any puppies must be entered into the registry as not for breeding and not upgraded to breeding dogs until their DNA results are known and their status for this gene is verified. This also tells us the status of the gene variant in the semen for future breeding decisions and pedigree tracking. This is to ensure we locate any dogs with one or zero copies of the gene variant and that breeders know the status of their dogs so they can make breeding choices with knowledge.
This ensures we maintain as much of the breed’s genetic diversity as possible and move toward breeding more dogs of this breed that will not be susceptible to these health conditions.
Where Are We Up To?
We have seen remarkable progress in identifying dogs with one copy of the adamts3 that are not closely related to each other. We now have numerous males and females with zero copies of this gene variant. Results indicate that other health problems in the breed have been positively impacted, which aligns with studies regarding this gene. Dogs with zero copies of this gene variant have normal tracheas; to date, none have suffered health ailments commonly associated with oedema in this breed.
Whilst the frequency of dogs with two copies of the adamts3 gene variant is very high in this breed, finding dogs that are not closely related to each other and, therefore, the speed at which the breeders who are involved in this program have been able to produce zero copied males and females ensures that over time we will see a greater incidence of dogs in this breed who are not affected by this disease. Dogs with zero copies of this gene variant can mate with any two copied dogs and not produce any puppies affected by this condition.
Testing for the adamts3 gene variant is still required for all British Bulldogs used for breeding in the MDBA gene pool and any new dog being entered from other registries.
Any dog being collected must be tested for this gene variant before collection.
The Way Forward
While this will not happen overnight, it is now realistically probable that the objective will be achieved. This is to have as many dogs as possible in the MDBA gene pool with zero copies of this gene variant who do not share a common ancestor in at least four generations. The MDBA breeder members who have taken up the challenge to be involved in this program can proudly take credit for their willingness to work as a team and adhere to what is required to breed for the true betterment of the breed.
DNA testing requirements remain in place. The MDBA stud book is open and will continue to accept British Bulldogs from other registries, including those with two copies of this gene, which breeders are encouraged to breed with zero copy dogs to ensure we protect against a lowered genetic diversity.
We will continue to monitor compliance and genetic diversity and collect and analyse data.
References.
- Airways Oedema AdamTS3 https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1008102
- Dog Breeding Science (Australia). https://breeding.dog/index.php?test=aoe
- Oechtering G, Schlüter C, Lippert J. Brachycephaly in dog and cat: a “human induced” obstruction of the upper airways. Pneumologie. 2010;64:450–452. doi: 10.1055/s-0030-1255513. – DOI – PubMed
- Packer RM, Tivers MS. Strategies for the management and prevention of conformation-related respiratory disorders in brachycephalic dogs. Veterinary Med (Auckland) 2015;6:219–232. doi: 10.2147/VMRR.S60475. – DOI – PMC – PubMed