Achondroplastic dog breeds have no mutations in the transmembrane domain of the FGFR-3 gene.

One of the most common skeletal affections in humans is achondroplasia, a short-limbed dwarfism that is, in most cases, caused by mutations in the transmembrane domain of the fibroblast growth factor receptor-3 (FGFR-3) gene. Due to the lack of sufficient radiological, genetic, and molecular studies, most types of skeletal anomalies in dogs are classified as achondroplasia. To initiate the molecular characterization of some osteochondrodysplastic dog breeds, we obtained the DNA sequence of the transmembrane domain of the FGFR-3 gene from the dachshund, basset hound, bulldog, and German shepherd dogs. All 4 breeds showed no mutation in the evaluated region. This indicates that the mutation responsible for the osteochondrodysplastic phenotype in the tested dog breeds lies either elsewhere in the FGFR-3 gene or in other ones involved in the formation and development of endochondral bone.

Hypochondroplastic dwarfism in the Irish setter.

Two test matings in the irish setter were performed, and genetic, clinical, morphometric, radiographic, bone histological and plasma and urine biochemical features of dwarfism were studied. All offspring were phenotypically normal at birth and weaning, but at the age of 2.5 to 4 months the longitudinal growth of the spine and leg bones was retarded in the dwarfs compared with the normal littermates. Most dwarfs performed well, even in the field. Radiographic and histological evaluations revealed a hypochondroplasia. A morphometric diagnostic method for Irish setter dwarfism was developed. A single autosomal recessive mode of inheritance was verified.

Osteochondrodysplasia in a litter of Bulldog puppies.

A 1-month-old male Bulldog pup was presented with severe dyspnoea and was also unable to stand. Radiographs revealed a considerable dorsoventral flattening of the thoracic cavity, resulting in a reduced intrathoracic volume. The scapula of each foreleg was malpositioned on the thorax, resulting in the inability to adduct the legs and carry the body weight. The clinical signs are typical of an animal suffering from osteochondrodysplasia.

Canine intervertebral disc disease: a review of etiologic and predisposing factors.

In this report the literature on etiologic and predisposing factors of disc disease in the dog is reviewed and discussed. Hypochondroplasia is considered to be important in the etiology of disc disease. After some consideration on nomenclature and morphology, the genetic background of hypochondroplasia is described. The histochemical morphological and developmental similarities and differences between and within various dog breeds are discussed. Macroscopically visible features that predispose to disc disease are outlined. The biomechanical bow-string model of the vertebral column is reviewed. In the discussion the various literature data are interrelated to show how disc disease might be reduced by breeding measures without implicating the breed characteristics. Literature recommendations to help the individual dog are included.

Pseudoachondroplastic dysplasia in miniature poodles: clinical, radiologic, and pathologic features.

The clinical, radiologic, and pathologic features of pseudoachondroplastic dysplasia were studied in 13 affected Miniature Poodles. The disease became evident when pups were about 3 weeks old. Normal-appearing and affected pups were in the same litter, and both sexes were affected. Abnormal locomotion with abducted hindlimbs and flattened rib cages were accompanied by short, bent limbs and enlarged joints. Radiographically, areas of stippling and patchy densities were evident in the epiphyses. Histologically, these densities were identified as areas of bone associated with retarded ossification. After growth is completed, the epiphyses, ossify, but the bones are shortened and deformed. General health appears normal, except for restricted locomotion due to secondary arthritis and difficult breathing in dogs with a deformed thorax.

Chondrodystrophy: an inherited lethal condition in turkey embryos.

Chondrodystrophy was found to occur as an embryonic lethal in a special line of turkeys. Inheritance of the condition was studied in embryos produced parthenogenetically from virgin dams and also in embryos from the same dams in bisexual matings. Expression was similar to other forms of the disorder encountered in various avian species. Micromelia and brachycephaly were recognized in affected embryos after 9 days while lethality occurred mainly after 16 days of incubation. A few affected embryos expressed modified phenotypes and these were also nonviable. Modified phenotypes were not observed in parthenogenetic production, and it was thus inferred that such embryos may have been heterozygotes. No changes were evident when the genetic background was altered. The condition was inherited as a single, autosomal, recessive lethal, in both parthenogenetic progeny and in progeny from bisexual matings. The symbol ch is designated for the mutant allele.

Morphological studies of the canine intervertebral disc. The assignment of the beagle to the achondroplastic classification.

The morphological development of the epiphyseal growth plate and intervertebral discs of newborn and nine-month-old beagles, greyhounds and dachshunds have been studied. On the basis of the cellular and matrix development of these canine tissues together with the known characteristics associated with achondroplasia it is concluded that the beagle should be assigned to the chondrodystroid breed classification.