Chondrodysplasia (CDPA)
Inheritance
Autosomal Dominant
Affected Genes
CFA18 FGF4
Mutations
Chondrodysplasia (CDPA) = c.~5 kb insertion; g.chr18:20443725-20443726, Chondrodysplasia (CDPA) = c.G>A; g.chr18:48415661
Breeds
American Bully, American Pit Bull Terrier, Aussiedoodle, Australian Cobberdog, Australian Labradoodle, Australian Shepherd, Basset Hound, Beagle, Bernedoodle, Bichon Frise, Bordoodle, Boykin Spaniel, Brittany, Cardigan Welsh Corgi, Catahoula Leopard Dog, Cavachon, Cavalier King Charles Spaniel, Cavapoo, Cavapoochon, Chesapeake Bay Retriever, Chihuahua, Chinese Crested, Clumber Spaniel, Cockapoo, Coton de Tulear, Dachshund, English Cocker Spaniel, English Springer Spaniel, English Toy Spaniel, French Bulldog, German Shepherd Dog, Goldendoodle, Havanese, Irishdoodle, Jack Russell Terrier, Labradoodle, Labrador Retriever, Lowchen, Maltese, Maltipoo, Miniature American Shepherd, Miniature Australian Shepherd, Miniature Longhaired Dachshund, Miniature Pinscher, Miniature Poodle, Miniature Schnauzer, Miniature Smooth Dachshund, Miniature Wirehaired Dachshund, Newfypoo, Nova Scotia Duck Tolling Retriever, Papillon, Pekingese, Pembroke Welsh Corgi, Poodle, Portuguese Water Dog, Pyrenean Shepherd, Rat Terrier, Russian Tsvetnaya Bolonka, Schnoodle, Scottish Terrier, Sealyham Terrier, Sheepadoodle, Shih Tzu, Skye Terrier, Spanish Water Dog, Standard Poodle, Standard Smooth Dachshund, Standard Wirehaired Dachshund, Sussex Spaniel, Teddy Roosevelt Terrier, Toy Australian Shepherd, Toy Poodle, Weimaraner, Yorkiepoo, Yorkshire Terrier
Testing Summary
The chondrodysplasia trait test reliably determines if a dog has one of the following genotypes:
| cd/cd | This dog carries two copies of the cd allele which is found in dogs with normal, typical leg length. However, the actual leg length of the dog is a result of a combination of factors including variants in other genes. This dog will pass one copy of cd to 100% of its offspring. Interpretation: Likely typical leg length |
| CD/cd or CD/CD | This dog carries at least one copy of the CD allele, the variant associated with chondrodysplasia (short legs) in some breeds. This test cannot distinguish between dogs that have one (CD/cd) or two copies (CD/CD) of this variant. However, because this mutation is dominant, only one copy of the CD allele is necessary to produce short legs. The actual leg length of the dog is a result of a combination of factors including variants in other genes. This dog will pass the CD allele to 50% of its offspring if it carries a single copy of CD or to 100% of its offspring if it carries two copies of CD. Interpretation: Likely short-legged (may be typical leg length carrier) |
Detailed Summary
Leg length is one of the traits that varies significantly among dog breeds. The characteristic short-legged trait of some breeds is referred to as chondrodysplasia but is also known as short-limbed or disproportional dwarfism. The trait is found in many breeds including the Dachshund, Pekingese, Corgi, and Basset Hound. Chondrodysplasia is inherited in an autosomal dominant manner and is associated with an insertion of a duplicate copy of the FGF4 gene (known as a retrogene insertion) on chromosome 18. It is thought that this mutation causes premature activation of other growth factor receptors leading to early calcification of the long bones resulting in limbs with a short and curved appearance. Although many breeds of dog with short legs carry two copies of the mutation, some carry only one or none, suggesting that there are other genetic factors responsible for short legs in other breeds.
Testing Tips
The chondrodysplasia trait test evaluates a dog's DNA FGF4 gene for the presence of the "CD" variant that is associated with short legs in some breeds of dog. Dogs that inherit one or two copies of the FGF4 mutation (CD/CD or CD/cd) are likely to have short legs whereas dogs that inherit two copies of the cd variant (cd/cd) are likely to have legs of typical/normal length. This specific test, as performed on the Canine HealthCheck, accurately detects the presence of the "CD" variant, however, it cannot distinguish between dogs that carry one or two copies of this mutation. NOTE: This mutation is different from the mutation associated with intervertebral disc disease (IVDD) and chondrodystrophy on canine chromosome 12. In some breeds that carry both the chromosome 12 and chromosome 18 mutations associated with short legs, breeders that desire to maintain the short-legged trait while avoiding IVDD may be able to utilize genetic testing to maintain the chromosome 18-associated short leg trait while breeding away from the short leg trait associated with IVDD on chromosome 12.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
References
- Brown EA, Dickinson PJ, Mansour T, Sturges BK, Aguilar M, Young AE, Korff C, Lind J, Ettinger CL, Varon S, Pollard R, Brown CT, Raudsepp T, Bannasch DL. FGF4 retrogene on CFA12 is responsible for chondrodystrophy and intervertebral disc disease in dogs. Proc Natl Acad Sci U S A. 2017 Oct 24;114(43):11476-11481. doi: 10.1073/pnas.1709082114. [PubMed: 29073074]
- Parker HG, VonHoldt BM, Quignon P, Margulies EH, Shao S, Mosher DS, Spady TC, Elkahloun A, Cargill M, Jones PG, Maslen CL, Acland GM, Sutter NB, Kuroki K, Bustamante CD, Wayne RK, Ostrander EA. An expressed fgf4 retrogene is associated with breed-defining chondrodysplasia in domestic dogs. Science. 2009 Aug 21;325(5943):995-8. [PubMed: 19608863]
