Gene expression and mechanical properties regulating two phenotypes of horse’s skin appendages: hoof strength and hair structure

Sammanfattning: Background: The hair follicle and hoof are two parts of the horse’s skin appendages that emerge from the dermis and epidermis. Different phenotypes characterize these two integument structures and determine their quality. In this project, we were interested in studying two phenotypes, the strength of the hoof and two types of horse hairs. In the first study, an RNA-seq experiment was performed to investigate the gene expression characterizing the quality of the hoof of harness racing Standardbred horses. The aim of this study was to explain the ability of horses to race barefoot for successive races. The second study aimed to understand the mechanical properties of horses' phenotype#1 and phenotype#2 hair by measuring the hair diameter and tensile parameters. Results: The hoof study implicated the involvement of four differentially expressed genes encoding proteins with functions in keratinization, vascularization, and development of the horses’ hooves. These results may explain the underlying mechanisms for the ability of horses to race barefoot frequently. In the hair study, the diameter and tensile measurements done on the phenotype#1 and phenotype#2 hairs showed thicker diameter measurements in the phenotype#2 hair and higher strain and toughness modulus in the phenotype#1 hair. Conclusions: In the hoof study, we detected four differentially expressed genes involved in different biological processes controlling the hoof quality, which could explain the ability of horses to race barefoot for successive races. The immune system-related gene that was significantly differentially expressed may be involved in the quality and integrity of the hoof through an unrevealed new mechanism. In the hair study, the analysis of hair diameter and tensile measurements showed significant differences in the diameter, the strain, and the toughness modulus between phenotype#1 and phenotype#2 hair, which could reveal differences affecting the quality of the two types of hairs.