Mesioversion of the upper canines in Shelties

Mesioversion of the upper canine teeth (MCM=maxillary canine-tooth mesioversion), also known as lance canines, is a dental anomaly in which the upper canine teeth are displaced forward towards the nose. One or both upper canine teeth may be affected. Typical clinical manifestations are traumatic occlusion, where the incorrect position of the tooth damages soft tissues or other teeth, ulceration (sores) on the upper lip and an increased risk of periodontal disease. In more severe cases, extraction of the affected tooth or orthodontic correction of its position is necessary.

Two genetic variants in two nearby genes are strongly associated with this defect in Shelties: a substitution in the FTSJ3 gene, encoding an RNA methyltransferase, and an insertion in the GH1 gene, encoding growth hormone. Whether these genetic variants act together as a haplotype or each separately is not yet precisely known, nor is the mode of inheritance of these mutations.

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References:

Abrams, S.R., Hawks, A.L., Evans, J.M., Famula, T.R., Mahaffey, M., Johnson, G.S., Mason, J.M., Clark, L.A. : Variants in FtsJ RNA 2'-O-Methyltransferase 3 and Growth Hormone 1 are associated with small body size and a dental anomaly in dogs. Proc Natl Acad Sci U S A 117:24929-24935, 2020. Pubmed reference: 32958658.