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Nat Genet. 2016 Feb;48(2):152-8. doi: 10.1038/ng.3475. Epub 2015 Dec 21.

Regulatory mutations in TBX3 disrupt asymmetric hair pigmentation that underlies Dun camouflage color in horses.

Author information

1
Science for Life Laboratory Uppsala, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
2
HudsonAlpha Institute for Biotechnology, Huntsville, Alabama, USA.
3
Department of Genetics, Stanford University School of Medicine, Stanford, California, USA.
4
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
5
Institut National de la Recherche Agronomique (INRA), AgroParisTech, Génetique Animale et Biologie Intégrative, Jouy-en-Josas, France.
6
Menntaskólinn við Hamrahlíð, Reykjavík, Iceland.
7
Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA.
8
Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis, Davis, California, USA.
9
Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
10
Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA.

Abstract

Dun is a wild-type coat color in horses characterized by pigment dilution with a striking pattern of dark areas termed primitive markings. Here we show that pigment dilution in Dun horses is due to radially asymmetric deposition of pigment in the growing hair caused by localized expression of the T-box 3 (TBX3) transcription factor in hair follicles, which in turn determines the distribution of hair follicle melanocytes. Most domestic horses are non-dun, a more intensely pigmented phenotype caused by regulatory mutations impairing TBX3 expression in the hair follicle, resulting in a more circumferential distribution of melanocytes and pigment granules in individual hairs. We identified two different alleles (non-dun1 and non-dun2) causing non-dun color. non-dun2 is a recently derived allele, whereas the Dun and non-dun1 alleles are found in ancient horse DNA, demonstrating that this polymorphism predates horse domestication. These findings uncover a new developmental role for T-box genes and new aspects of hair follicle biology and pigmentation.

PMID:
26691985
PMCID:
PMC4731265
DOI:
10.1038/ng.3475
[Indexed for MEDLINE]
Free PMC Article

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