Straightened Small Pinnae in TRPV4 c.1024G>T Heterozygous Cats

The folded-ear phenotype of Scottish Fold cats results from a dominant variant of the TRPV4 gene (c.1024G>T). Producing homozygous individuals is discouraged due to severe osteochondrodysplasia and identifying heterozygous carriers is critical for breeding. Although carriers are generally expected to have folded ears, straight-eared individuals have also been suspected among them. Here, we investigated the relationship between ear phenotype and TRPV4 genotype using longitudinal photographic data and TRPV4 genotyping in 114 cats. We identified seven individuals that transitioned from folded to straight ear phenotype during maturation. Genotyping confirmed all were heterozygous carriers, with 12.7% found among heterozygous cats. Morphometric analysis of 14 cats with high-quality photographs demonstrated these "straightened" cats had smaller pinnae than genetically wild-type straight-eared cats (p < 0.05), suggesting cartilage anomalies. These findings confirm "cryptic folds"-phenotypically straight but genetically heterozygous cats. Consequently, visual inspection for breeding selection is insufficient, highlighting the necessity of TRPV4 genotyping to prevent unintentional production of homozygous offspring with severe osteochondrodysplasia.