@article{2899,
  keywords = {keratin, hair fiber, gene, mutation, hypotrichosis},
  author = {A Thomer and O Distl and J Metzger},
  title = {Review: Genetics of curly coat in domestic animals},
  abstract = {Curly hair may occur in humans, mammalian and avian species. Often, curly phenotypes are characteristics of breeds or strains in cats, horses, dogs, pigs, goats, sheep, cattle, guinea pigs and rabbits. In addition, curly feathers can be expressed by specific chicken, geese, quail and pigeon breeds or strains. The shape of hair follicles and the structures of inner and outer root sheaths within it, they all affect the axial curvature and form of hair shaft leading to different degrees of curliness. Longitudinal and cross sections of hair shafts show a restricted medulla with asymmetric swellings leading to bends and an elliptical diameter in curly hair fibers compared to straight hair with pronounced medulla and circular diameter. Scanning electron microscopy imaging reveals a rougher surface and depressions as characteristics for curly hair lacking in straight hair fibers. Keratin genes play an important role in the development of curls. In particular, variants of the keratin genes KRT25, KRT71 and KRT74 as well as variants of CX43, LIPH and LPAR6 are associated with the formation of curly hair in human. In domestic animals, mutations were identified in KRT25, KRT27, KRT71, LPAR6, LIPH, Sgk3 and SP6. Mutations destroying the α-helical 2B rod domain of KRT25 or KRT27 cause fragile “woolly” hair with a reduced stability of the hair shaft. This KRT25 mutant phenotype is seen in human and Rex-mice with fragile vibrissae as well as in horses with hypotrichosis. In curly-coated cattle, a mutation changes the coil 1A domain of KRT27 and thus, may inhibit the coiled-coil binding to other keratins. The loss of the α-helical rod domain of KRT71 cannot be compensated by other type II keratins and causes alopecia in mice. Lysophosphatidic acid receptor 6 (LPAR6) maintains the structural integrity of the hair shaft and mutated LPAR6 variants are involved in dry and curly “woolly” hair of humans, often associated with hair loss, and in Cornish Rex cats. The curly phenotype in human and domestic animals is a monogenic trait. In horses, two different curly hair mutations in the genes KRT25 and SP6 are segregating due to intermixing of different source populations where these mutations have been arisen. The KRT25 variant is epistatic to the SP6 variant and thus individuals with mutations in both genes express the curly phenotype associated with hypotrichosis like KRT25 mutated horses. },
  year = {2019},
  journal = {Berliner und Münchener Tierärztliche Wochenschrift},
  volume = {132},
  month = {07/2019},
  publisher = {Schlütersche Verlagsgesellschaft mbH & Co. KG},
  address = {Hannover},
  issn = {0005-9366},
  doi = {10.2376/0005-9366-18043},
  language = {English},
}