Skeletal Dysplasia 2, SD2 (Disproportionate dwarfism) 

 

Gene: COL11A2 (Collagen 11A2)

Transmission: Autosomal recessive, incomplete penetration

For an autosomal recessive genetic disease an animal must have two copies of the mutation in question to be at risk of developing the disease.  Both parents of an affected animal must be carriers of at least one copy of the mutation.  Animals that have only one copy of the mutation are not at risk of developing the disease but are carrier animals that can pass the mutation on to future generations.

Mutation: Substitution, COL11A2 gene; c.143 G>C, p.(R48P), exon 2

Medical system: Skeletal

Breeds: American Cocker Spaniel, American Staffordshire Terrier/Amstaff, Beagle, Cavalier King Charles Spaniel, Labrador Retriever, Miniature Pinscher, Pomeranian, Poodle - Miniature (Dwarf), Poodle - Standard, Siberian Husky

Age of onset of symptoms: At birth

Skeletal Dysplasia 2 is a genetic disease seen in Labrador Retrievers that affects the function of collagen11 which is required for normal bone formation. Individuals that have two copies of the mutation can display disproportionate dwarfism: they have short limbs due to the shorter and thicker long bones but a normal body width and length. The forelegs are more often affected than the hind limbs. This disease has not been associated with other secondary problems such as joint disease.  The disease has a transmission that is described as autosomal recessive with incomplete penetrance, meaning that an animal can have two copies of the mutated gene without showing the disproportionate dwarfism phenotype.  This indicates that additional modifying genes, not as yet identified, are contributing to the phenotype.

 

References:
OMIA link: [1772-9615]

Donner J, Freyer J, Davison S, et al. (2023) Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs.  PLoS Genet. 19(2):e1010651. [pubmed/36848397]

Frischknecht M, Niehof-Oellers H, Jagannathan V, et al. (2013) A COL11A2 mutation in Labrador Retrievers with mild disproportionate dwarfism. PLOS ONE 8(3)e60149. [pubmed/23527306]