Canine Dental Hypomineralization (Raine Syndrome)
Canine dental hypomineralization or Raine Syndrom is a genetic disorder affecting the Border Collies. The disorder causes severe tooth wear resulting in pulpitis and requiring extraction of those teeth. Dental hypomineralization is a canine model for human Raine Syndrom, with which it shares the causative mutation and similar symptoms. In human patients, Raine syndrome is also known as osteosclerotic bone dysplasia and is characterized by craniofacial anomalies including microcephaly, noticeably low set ears, osteosclerosis, a cleft palate, gum hyperplasia, a hypoplastic nose, and eye proptosis.
Characteristics and Symptoms
Dental examination of the affected dogs reveals a significant wear. Lower incisor teeth can be worn close to the gingival margin. The enamel shows a light brown discoloration and appears dull. Some worn teeth can have a pulp exposure and pulpits as a result of the wear. In examined dogs, the wear was not caused by an abnormal tooth-to-tooth contact, since the occlusion was normal. Blood tests showed normal calcitriol, phosphate and alkaline phosphatase levels. The enamel, depending on the position, can be largely worn and cracked. Overall, clinical and histopathological analyses indicate severe hypomineralization of teeth in the affected dogs.
Canine dental hypomineralization is caused by a mutation in the FAM20C gene. Genotypization revealed carrier rate of 11% among 200 tested Border Collies. The mutation was not found in other breeds, suggesting it is specific for the Border Collie breed.
Raine syndrome in Border Collies is inherited in an autosomal recessive pattern. Healthy parents of affected puppy are obligate heterozygotes and therefore carry one mutant allele. Heterozygotes have no symptoms. Dogs homozygous for the mutation will display the symptoms of the dental hypomineralization. At conception, when mating two carrier dogs, 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.
Hytönen MK, Arumilli M, Lappalainen AK, Owczarek-Lipska M, Jagannathan V, Hundi S, et al. (2016) Molecular Characterization of Three Canine Models of Human Rare Bone Diseases: Caffey, van den Ende-Gupta, and Raine Syndromes. PloS Genet 12(5): e1006037. doi:10.1371/journal. pgen.1006037