Curly Coat in Bashkir Curly Horse and Curly Horse Breeds (KRT25 gene)

The KRT25 gene encodes type I keratin, which is a component of hair and coat fibers. The c.266G>A variant in the KRT25 gene affects coat structure and is the main known genetic cause of curly coat in horses. The degree of curl can vary considerably – from a few slightly wavy hairs to a dense, permanently curly coat covering the entire body. In some horses, the mane, tail, or fetlocks may also be curly. The degree of curl can change throughout the year and is usually most pronounced in the winter coat.

The variant is inherited in an autosomal dominant manner. Individuals that inherit at least one copy of the mutated gene generally exhibit a curly coat, whereas horses without the variant have a normal straight coat. However, the degree of curl is highly variable and cannot be reliably predicted based on genotype alone.

Knowledge of the KRT25 genotype can help confirm the genetic cause of curly coat, support breeding decisions, and predict the likelihood of this trait occurring in offspring. However, when interpreting the results, it should be taken into account that curly coat may also be caused by other genetic variants that have not yet been fully characterized.

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Reference:

Morgenthaler, C., Diribarne, M., Capitan, A., Legendre, R., Saintilan, R., Gilles, M., Esquerré, D., Juras, R., Khanshour, A., Schibler, L., Cothran, G. : A missense variant in the coil1A domain of the keratin 25 gene is associated with the dominant curly hair coat trait (Crd) in horse. Genet Sel Evol 49:85, 2017. Pubmed reference: 29141579

Thomer, A., Gottschalk, M., Christmann, A., Naccache, F., Jung, K., Hewicker-Trautwein, M., Distl, O., Metzger, J. : An epistatic effect of KRT25 on SP6 is involved in curly coat in horses. Sci Rep 8:6374, 2018. Pubmed reference: 29686323