In this issue

Maxillary canine tooth mesioversion, or lance canine, is a dental anomaly in dogs in which a displaced upper canine tooth can cause painful occlusion, upper lip ulceration, and periodontal disease. The genetic basis of lance canine, which rarely afflicts breeds other than Shetland Sheepdogs, remains unclear. Sydney Abrams et al. (pp. 24929–24935) used a genome-wide association study and whole genome sequencing to uncover risk factors of lance canine in Shetland Sheepdogs, a small breed that stands 13–16 inches tall. The analysis yielded risk variants in two genes on chromosome 9: A single base insertion in GH1, which encodes a growth hormone implicated in human pituitary dwarfism, causes incomplete processing of GH1 RNA, and a single amino acid change in FTSJ3, which encodes an enzyme involved in RNA processing and cell proliferation, likely affects the enzyme’s activity. The variants were associated not only with lance canine but also body height and weight, and the authors found that dogs with lance canine were shorter and weighed less than control dogs. Notably, each copy of the FTSJ3 variant reduces size by around 1 inch and 5 pounds. Additional analysis in 1,049 dogs of 224 breeds revealed the variants’ presence in an array of toy breeds, including Chihuahuas, Miniature Pinschers, Pomeranians, Toy Poodles, and Yorkshire Terriers, but not in larger breeds. According to the authors, the study uncovers a genetic locus in dogs that influences body size and is tied to a dental anomaly. — P.N.