Osteochondrodysplasia Miniature Poodle Type (OCD)
Osteochondrodysplasia Miniature Poodle type (OCD) is a form of skeletal dysplasia in the Poodle breed. Osteochondrodysplasia is a disorder (”dysplasia”) of bones (”osteo”) and cartilage (”chondro”). It can be characterized into group of musculoskeletal disordes, a broad category of diseases that affects the muscles or bones. OCD in Miniature Poodle was first time described as crippling dwarfism in 1956 in Great Britain. Since then, additional cases have been documented in research articles in United States, Great Britain and Germany. Miniature Poodle osteochondrodysplasia shares many clinical signs with genetically diverse human skeletal dysplasias.
Sulphate is a hydrophilic anion important for many physiological processes in the body and for structure and function of macromolecules. Its importance of bodily input also lies in importance of sulphur. After calcium and phosphorus, sulphur is the third most importand mineral in the body and it can be found in muscles and bones as well as many other systems of the body. It also helps create connective tissues which support the joints.
Sulfate requires active transport through the membrane in all cells via two specialized transporters: the sodium-dependent sulfate symporters and the sodium independent transporters. A sodium-dependent sulfate symporter, needed for regulation of serum levels of sulfate is SLC13A1. It is expressed in the luminal epithelium of small intestine and also in the renal epithelium. In the small intestive SLC13A1 mediates absorption of dietary sulfate, while in renal epithelium it mediates reabsorption from the proximal renal tubule of the kidney. Researches have shown that loss of SLC13A1 in mice causes hyposulfatemia and hypersulfaturia. Such mice also exhibited lowered fertility, gastrointestinal abnormalities, altered neurochemistry, impaired memory, decreased object-induced anxiety, decreased acitivity levels and a possible increase in longevity.
Main characteristics of Osteochondrodysplasia Miniature Poodle type (OCD) are growth retardation and defects in mobility, which can be first noticed at three weeks of age. After the first symptoms occur, other symptoms are following, such as abducted hind limbs, enlarged joints, dorsoventral flattening of the rib cage, shortened and bent long bones, undershot jaws, and elongated and misshapen paws that resemble clubfoot, a congenital deformity of one or both feet. Examination shows rapid conversion of cartilage to bone. Affected dogs show extremly low values for serum sulfate level. In healthy, non-affected dogs average serum sulfate is approximately 1.4 mM, while in affected dogs level is below the limit of detection for the assay, which means below 0.2 mM.
Osteochondrodysplasia in the Miniature Poodle (OCD) is caused by a mutation in the SLC13A1 gene. Althought genetic background, OCD in Miniature Poodle resembles more phenotypically to Osteochondrodysplasia in humans, caused by a mutation in the SLC13A6 gene, that to mice OCD caused by same mutation.
The disorder is inherited in an autosomal recessive manner. Healthy parents of an affected dog are obligate heterozygotes, and therefore carry one mutant allele. Heterozygotes have no symptoms. At conception, each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
Neff MW, Beck JS, Koeman JM, Boguslawski E, Kefene L, Borgman A, Ruhe AL. Partial deletion of the sulfate transporter SLC13A1 is associated with an osteochondrodysplasia in the Miniature Poodle breed. PLoS One. 2012;7(12):e51917.
Riser WH, Haskins ME, Jezyk PF, Patterson DF. Pseudoachondroplastic dysplasia in miniature poodles: clinical, radiologic, and pathologic features. J Am Vet Med Assoc. 1980 Feb 15;176(4):335-41. Review.