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

Area of Science:

• Genetics
• Veterinary Medicine
• Animal Science

Background:

• The folded-ear trait in Scottish Fold cats is linked to a dominant TRPV4 gene variant.
• Homozygous individuals exhibit severe osteochondrodysplasia, making heterozygous carrier identification crucial for responsible breeding.
• Phenotypic variability exists, with some heterozygous carriers potentially displaying straight ears.

Purpose of the Study:

• To investigate the correlation between ear phenotype and TRPV4 genotype in Scottish Fold cats.
• To identify the prevalence of 'cryptic folds' – phenotypically straight but genetically heterozygous cats.
• To emphasize the importance of genetic testing for breeding programs.

Main Methods:

• Longitudinal photographic data and TRPV4 genotyping were utilized for 114 cats.
• Seven cats showed a phenotype transition from folded to straight ears during maturation.
• Morphometric analysis compared pinnae size in 'straightened' heterozygotes and wild-type cats.

Main Results:

• All seven cats that transitioned to a straight-ear phenotype were confirmed heterozygous carriers.
• Approximately 12.7% of heterozygous cats were identified as having a straight-ear phenotype ('cryptic folds').
• Cats with 'cryptic folds' had significantly smaller pinnae than genetically wild-type straight-eared cats, indicating cartilage anomalies.

Conclusions:

• Phenotypically straight-eared cats can be heterozygous carriers of the TRPV4 folded-ear gene variant.
• Visual assessment alone is insufficient for identifying carriers in breeding programs.
• TRPV4 genotyping is indispensable to avoid unintentional breeding of homozygous cats with severe osteochondrodysplasia.