Genethic basis of Amelogenesis Imperfecta in Jack Russell Terriers - is caused by an autosomal recessive mutation in the ENAM gene. Specifically, this variant involves a point mutation (c.716C>T) in exon 8 of the ENAM gene resulting in a missense mutation p.(Pro239Leu). The ENAM gene encodes enamelin, a protein essential for normal enamel formation and mineralization of teeth. Dogs with two copies of this mutation (homozygous) develop AI, whereas carriers with one copy are asymptomatic but can pass the mutation to offspring. This mutation leads to defective enamel development affecting both deciduous and permanent teeth.
Pathophysiology - The ENAM mutation causes defective enamel protein function, resulting in hypomineralization and hypoplasia of the tooth enamel. Affected dogs have teeth with rough, thin, dull, and mottled enamel which can appear brownish or discolored. Teeth may be smaller, pointed, brittle, and show increased spacing due to enamel wear and loss. Despite enamel defects, the basic tooth structure is typically intact, and systemic health is not affected.
Complications - Dental abnormalities like enamel hypoplasia lead to increased tooth wear and possible dental discomfort. Teeth appearance and function can be altered but severe dental disease is uncommon. Early detection helps avoid misdiagnosis and allows management focused on dental care.
Why This Matters to Breeders and Vets - For breeders, identifying carriers is crucial to avoid producing affected puppies via carrier-to-carrier matings. Genetic testing guides informed breeding decisions to reduce the frequency of this condition. Veterinarians benefit from understanding the disorder for accurate diagnosis and advising owners on dental health management.
Summary - Amelogenesis Imperfecta (Jack Russell Terrier Type), Variant 1, is an autosomal recessive enamel defect caused by a missense mutation in the ENAM gene. It results in defective, rough, thin, and discolored tooth enamel, affecting dental appearance and function but not systemic health. Genetic testing enables breeders to make informed mating decisions to reduce affected dogs in the population. Veterinarians can diagnose the condition and assist owners with dental care guidance.