The Chicken Frizzle Feather Is Due to an a-Keratin (KRT75) Mutation That Causes a Defective Rachis

Feathers have complex forms and are an excellent model to study the development and evolution of morphologies. Existing chicken feather mutants are especially useful for identifying genetic determinants of feather formation. This study focused on the gene F, underlying the frizzle feather trait that has a characteristic curled feather rachis and barbs in domestic chickens. Our developmental biology studies identified defects in feather medulla formation, and physical studies revealed that the frizzle feather curls in a stepwise manner. The frizzle gene is transmitted in an autosomal incomplete dominant mode. A whole-genome linkage scan of five pedigrees with 2678 SNPs revealed association of the frizzle locus with a keratin gene-enriched region within the linkage group E22C19W28_E50C23. Sequence analyses of the keratin gene cluster identified a 69 bp in-frame deletion in a conserved region of KRT75, an a-keratin gene. Retroviral-mediated expression of the mutated F cDNA in the wild-type rectrix qualitatively changed the bending of the rachis with some features of frizzle feathers including irregular kinks, severe bending near their distal ends, and substantially higher variations among samples in comparison to normal feathers. These results confirmed KRT75 as the F gene. This study demonstrates the potential of our approach for identifying genetic determinants of feather forms. Citation: Ng CS, Wu P, Foley J, Foley A, McDonald M-L, et al. (2012) The Chicken Frizzle Feather Is Due to an a-Keratin (KRT75) Mutation That Causes a Defective Rachis. PLoS Genet 8(7): e1002748. doi:10.1371/journal.pgen.1002748 Editor: Dennis Roop, University of Colorado Health Sciences Center, United States of America Received November 18, 2011; Accepted April 19, 2012; Published July 19, 2012 Copyright: 2012 Ng et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: W-HL acknowledges the National Science Council of Taiwan grant number 99-2321-B-001-041-MY2. C-MC acknowledges the National Institutes of Health of USA grant number AR 47364. W-TJ acknowledges the funding support from Academia Sinica Research Program on Nanoscience and Nanotechnology. CSN acknowledges the postdoctoral fellowship from Academia Sinica of Taiwan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected] (W-HL); [email protected] (C-MC) . These authors contributed equally to this work.