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

Disease-related: 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: