Chondrodysplasia

group-of-malamute-puppies-in-a-pool

The status of obtaining a genetic test for CHD

July 8, 2012: The researchers have identified approximately 30 variants of interest in our samples, and are running these through further analysis. Additionally, they will be doing a SNP-chip genotyping study which will hopefully increase our chances to find the causative mutation. Additional new samples from carriers and an affected dog are being sent to the lab, which will help Dr. Lohi’s group confirm any findings they may uncover. We should know more in the coming few months. We have informed them that if any funds are needed to accelerate the research, we will do what is needed to provide these through the Canine Health Foundation grant process using our Donor Advised Fund. January, 2012:   At the beginning of 2011, we were told that the researcher at MSU who has been working on this project for years, Dr. Pat Venta, was willing to collaborate with another researcher who had more advanced technology in an effort to find this gene.

Unfortunately, several months later we were informed that he had decided against this collaboration and wanted to pursue a grant on his own to do the research.  At this time no grant has been pursued. Because finding the gene for dwarfism is a priority, we are exploring all other options for this research. Dr. Hannes Lohi at the University of Helsinki discovered the gene for dwarfism in Norwegian Elkhounds, but samples from our dwarfs have found that this is not the same gene. However, his research team has taken on finding this gene in our breed-at no cost. We have gathered samples from all currently living dwarfs and dwarf carriers and have shipped the majority of these to their facility in Helsinki. These samples have been run through a whole exome scan platform, which is the most advanced genetic analysis available. They hope to have the results from this in a few months, at which time they will look for abnormalities which may represent the gene for the disease. How long this will take depends completely upon what the genetic results look like, but we feel confident that this team is doing everything that can be done on this project as quickly as is possible. They have been extremely responsive to any questions we have, and have been very proactive in asking us questions as well as getting any samples into their lab. If any new dwarfs are identified, we desperately need DNA from these dogs for our research study.  If you have any samples to contribute or questions, please feel free to contact: Sandi Shrager AMCA Health Committee Chair sandis@u.washington.edu 206-919-8103206-919-8103 Kaisa Kyostila kaisa.kyostila@helsinki.fi Ranja Eklund/Lohi Laboratory Biomedicum Helsinki, room B320 Haartmaninkatu 8 00290 Helsinki Finland   Below is a table with descriptions of the type abbreviations used in the database:

Type
Description
G genetically uninvolved
P Perceived
PN perceived negligible(less than.50% )
T tested
TN tested negligible (less than.50%)
TB Blood tested
1 .5 to 1..49%
2 1.5 to 2..49

 

Chondrodysplasia

Chondrodysplasia is a genetic disorder in the Alaskan Malamute which manifests itself in puppies born with deformities, eventually evident in the abnormal shape and length of their limbs. Chondrodysplasia is present in adult carriers as an auto-somal or simple recessive gene.  Therefore, both sire and dam must carry this gene in order to produce an affected (chondrodysplastic) puppy. As Malamute owners and prospective owners, we have an opportunity to control the proliferation of Chondrodysplasia in the Alaskan Malamute, and with such control, there is hope of its total elimination in our breed.

History and Explanation

For a number of years, Alaskan Malamute breeders in both the United States and Canada were aware of occasional litters that contained deformed or “dwarf puppies”, produced by parents who showed no physical evidence of the condition. It was not until the early 1970’s that these puppies were conclusively proven to be the manifestation of a genetic disorder. At first, these affected dogs were known as “dwarves” because of their diminutive size. This term gave rise to considerable confusion.  Veterinarians associated it with the dwarfism found in Hereford cattle, while owners associated it with any small Malamute. Since neither is correct, another name, Chondrodysplasia(meaning “faulty cartilage”), was coined and brought into usage. Chondrodysplasia in the Malamute was originally diagnosed as a form of rickets. Upon closer examination at various veterinary schools, it was determined that this diagnosis was incorrect. While it isn’t known exactly what this crippling problem is, it has definitely been proven to be genetic, or inherited. A more technical description of this gene is “auto-somal,” or “simple recessive.” This simply means that the sire and dam must both carry this gene in order to produce an affected chondrodysplastic puppy. In very young puppies, under six weeks of age, the deformity is often very difficult, if not impossible, to detect without x-rays, even to the practiced eye. But as the puppies grow older, the deformity becomes more evident in the shape and length of the front legs. However, not all chondrodysplastics are severely affected. In some adults, the front legs may appear “almost” normal. It is not the chondrodysplastics themselves that are the major problem. The greatest concern is the use in breeding of the completely normal appearing dogs that possess or “carry” this gene. (A good parallel of this among humans is two brown-eyes parents producing a blue-eyed baby. In spite of their brown eyes, the parents both “carry” the gene for the blue eye.) While the breeding of two carriers can produce a chondrodysplastic, a litter from a breeding between a carrier and a “non carrier” (or clear) will contain only normal appearing dogs. Nevertheless, an undetermined number of puppies will themselves be carriers, having inherited the gene from their carrier parent. The continued whelping of such litters increase the number of carriers “at large” in the total Malamute population.

Chondrodysplasia Certification Registry

CHD Certification is available to dogs with one certified ancestor between the applicant dog and each uncertified ancestor. If proof can be offered that an uncertified ancestor is a full sibling to a certified dog, the applicant’s pedigree will be evaluated. It should be noted that certification can be revoked when information is verified that a dog was mis-classified through subsequent breedings and/or test breedings. Sometimes the pedigree reveals the dog to be non-certifiable with regards to Chondrodysplasia. In such cases, the AMCA recommends these dogs not be bred. The owner may feel the dog to be a great asset to a breeding program, or the dog may already have offspring who are themselves now affected by the un-certifiable status of the parent. In such circumstances, the owner may choose to apply for a further screening process known as “Test Breeding”. The certificate is not proof that a dog is clear
(i.e. not a carrier), but only that the probability that it is is calculated to be below 6.25%. AMCA is supporting genetic research programs with the intent of finding a DNA marker allowing the proof that a dog is either clear of this genetic disorder or is not. Whenever this test is available, then there will no longer be a need for test breeding to track this condition.

Test Breeding

The committee will assist the owner in this choice. At present, test breeding a suspect Malamute to a Chondrodysplastic, or to a known carrier, is the only means to be reasonably certain the dog is not a carrier of the gene. Should the owner decide to enter the suspect dog into a test breeding program, a contract specifying certain criteria is entered into with the AMCA Chondrodysplasia Certification Committee. The Committee Chairman and Area Representatives are available for consultation regarding the procedures for test breeding. Once thought to occur only in Malamute, Chondrodysplasia has now been detected in other breeds and the AMCA program has become a model for other breed clubs. Your efforts are needed if it is to continue to fulfill its vital leadership role. We hope you will join us in the fight to control this genetic disorder. It is essential for the prospective malamute purchaser of potential breeding stock to realize the importance of these certificates. By purchasing from AMCA Certified stock, the buyer not only is helping the breed cull out Chondrodysplasia, but is also relieving himself of the responsibility of test breeding.