OMIA:000245-9796 : Curly coat in Equus caballus (horse)

In other species: dog , domestic cat

Categories: Integument (skin) phene

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 608245 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal dominant

Considered a defect: no

Key variant known: yes

Year key variant first reported: 2017

Species-specific symbol: Crd

Species-specific description: Morgenthaler et al. (2017): "First described by Crow and Sioux Native American tribes as early as 1801 during winter horse counting [Thomas et al., 1989], Curly horses present a variety of coat curl phenotypes associated with diverse degrees of curliness which can range from “minimal” scattered curled hair up to extremely dense “micro curled” permanent coat as observed in certain Missouri Fox Trotter lines".

Inheritance: Morgenthaler et al (2017): "in North American horses, the most frequent Curly coat phenotype is described as autosomal dominant (Crd) [Sponenberg, 1990], whereas recessive forms have been reported to segregate in the Quarter Horse, Arabian, Appaloosa, Missouri Fox Trotter, Tennessee Walking Horse, Paint, Morgan and Paso Fino breeds [Sponenberg, 1990] as well as in French Percheron horses [Blakeslee et al., 1943]."

Mapping: Morgenthaler et al. (2017): "A GWAS was performed using a Bayesian sparse linear mixed model, based on 51 curly and 19 straight-haired French and North American horses from 13 paternal families genotyped on the Illumina EquineSNP50 BeadChip. A single strong signal was observed on equine chromosome 11, in a region that encompasses the type I keratin gene cluster."

Molecular basis: Morgenthaler et al. (2017): "whole-genome sequences were obtained for one heterozygous curly stallion and its straight-haired son. Among the four non-synonymous candidate variants identified and validated in the curly region, only variant g.21891160G>A in the KRT25 gene (KRT25:p.R89H) was in perfect agreement with haplotype status in the whole pedigree. Genetic association was then confirmed by genotyping a larger population consisting of 353 horses. However, five discordant curly horses were observed, which carried neither the variant nor the main haplotype associated with curliness. Sequencing of KRT25 for two discordant horses did not identify any other deleterious variant, which suggests locus rather than allelic heterogeneity for the curly phenotype." Thomer et al. (2018) independently discovered the same likely causal variant, but also showed how this variant interacts with a variant at SP6 in relation to curly coat with/without hypotrichosis (see 002175-9796)

Breed: Curly Horse (Horse) (VBO_0000943).
Breeds in which the phene has been documented. (If a likely causal variant has been documented for the phene, see the variant table breeds in which the variant has been reported).

Associated gene:

Symbol Description Species Chr Location OMIA gene details page Other Links
KRT25 keratin 25, type I Equus caballus 11 NC_009154.3 (21962667..21968887) KRT25 Homologene, Ensembl , NCBI gene


By default, variants are sorted chronologically by year of publication, to provide a historical perspective. Readers can re-sort on any column by clicking on the column header. Click it again to sort in a descending order. To create a multiple-field sort, hold down Shift while clicking on the second, third etc relevant column headers.

WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.

Since October 2021, OMIA includes a semiautomated lift-over pipeline to facilitate updates of genomic positions to a recent reference genome position. These changes to genomic positions are not always reflected in the ‘acknowledgements’ or ‘verbal description’ fields in this table.

OMIA Variant ID Breed(s) Variant Phenotype Gene Allele Type of Variant Source of Genetic Variant Reference Sequence Chr. g. or m. c. or n. p. Verbal Description EVA ID Year Published PubMed ID(s) Acknowledgements
856 Bashkir Curly (Horse) Curly Horse (Horse) Curly coat KRT25 Crd missense Naturally occurring variant EquCab3.0 11 NC_009154.3:g.21962991G>A NM_001346190.1:c.266G>A NP_001333119.1:p.(R89H) rs1095048844 2018 29686323 29141579 Variant coordinates obtained from and/or confirmed by EBI's Some Effect Predictor (VEP) tool

Cite this entry

Nicholas, F. W., Tammen, I., & Sydney Informatics Hub. (2019). OMIA:000245-9796: Online Mendelian Inheritance in Animals (OMIA) [dataset].


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.

2024 Durward-Akhurst, S.A., Marlowe, J.L., Schaefer, R.J., Springer, K., Grantham, B., Carey, W.K., Bellone, R.R., Mickelson, J.R., McCue, M.E. :
Predicted genetic burden and frequency of phenotype-associated variants in the horse. Sci Rep 14:8396, 2024. Pubmed reference: 38600096. DOI: 10.1038/s41598-024-57872-8.
2023 Mitlehner, A., Mitlehner, C., Reißmann, M., Stoll, P., Swoboda, I., Mitlehner, W. :
Horse allergy: Curly Horses can mediate immune tolerance. Pneumologie , 2023. Pubmed reference: 37827498. DOI: 10.1055/a-2101-9533.
2018 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. DOI: 10.1038/s41598-018-24865-3.
2017 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. DOI: 10.1186/s12711-017-0359-5.
2016 Leroy, G., Besbes, B., Boettcher, P., Hoffmann, I., Capitan, A., Baumung, R. :
Rare phenotypes in domestic animals: unique resources for multiple applications. Anim Genet 47:141-53, 2016. Pubmed reference: 26662214. DOI: 10.1111/age.12393.
1990 Sponenberg, D.P. :
Dominant Curly Coat in Horses Genetics Selection Evolution 22:257-260, 1990.
1989 Thomas, S., Gaier, D., Bowling, A. :
Myth and mystery: the curly horse in America. New York: C.S. Fund Inc. , 1989.
1943 Blakeslee, L.H., Hudson, R.S., Hunt, H.R. :
Curly coat of horses. Journal of Heredity 34:115-118, 1943.
1940 Shcheckin V.A., Kalaev, V.V. :
Inheritance of curliness in the horse C.R. (Doklady) Academy of Science U.R.S.S., N.S. 26:262-263, 1940.

Edit History

  • Created by Frank Nicholas on 06 Sep 2005
  • Changed by Frank Nicholas on 17 Nov 2017
  • Changed by Frank Nicholas on 21 Nov 2017
  • Changed by Frank Nicholas on 14 Mar 2019