Origin of feathers: Feather beta (β) keratins are expressed in discrete epidermal cell populations of embryonic scutate scales
Article first published online: 22 JAN 2003
Copyright © 2003 Wiley-Liss, Inc.
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
Volume 295B, Issue 1, pages 12–24, 15 February 2003
How to Cite
Sawyer, R. H., Salvatore, B. A., Potylicki, T.-T. F., French, J. O., Glenn, T. C. and Knapp, L. W. (2003), Origin of feathers: Feather beta (β) keratins are expressed in discrete epidermal cell populations of embryonic scutate scales. J. Exp. Zool., 295B: 12–24. doi: 10.1002/jez.b.5
- Issue published online: 22 JAN 2003
- Article first published online: 22 JAN 2003
- Manuscript Accepted: 12 JUL 2002
- Manuscript Received: 8 MAR 2002
- U.S. Department of Energy Office of Environmental Management. Grant Number: DE-FG02-97EW09999
- Department of Defense, Office of Naval Research. Grant Number: N000149710806
The feathers of birds develop from embryonic epidermal lineages that differentiate during outgrowth of the feather germ. Independent cell populations also form an embryonic epidermis on scutate scales, which consists of peridermal layers, a subperiderm, and an alpha stratum. Using an antiserum (anti-FβK) developed to react specifically with the beta (β) keratins of feathers, we find that the feather-type β keratins are expressed in the subperiderm cells of embryonic scutate scales, as well as the barb ridge lineages of the feather. However, unlike the subperiderm of scales, which is lost at hatching, the cells of barb ridges, in conjunction with adjacent cell populations, give rise to the structural elements of the feather. The observation that an embryonic epidermis, consisting of peridermal and subperidermal layers, also characterizes alligator scales (Thompson, 2001. J Anat 198:265–282) suggests that the epidermal populations of the scales and feathers of avian embryos are homologous with those forming the embryonic epidermis of alligators. While the embryonic epidermal populations of archosaurian scales are discarded at hatching, those of the feather germ differentiate into the periderm, sheath, barb ridges, axial plates, barbules, and marginal plates of the embryonic feather filament. We propose that the development of the embryonic feather filament provides a model for the evolution of the first protofeather. Furthermore, we hypothesize that invagination of the epidermal lineages of the feather filament, namely the barb ridges, initiated the formation of the follicle, which then allowed continuous renewal of the feather epidermal lineages, and the evolution of diverse feather forms. J. Exp. Zool. (Mol. Dev. Evol.) 295B:12–24, 2003 © 2003 Wiley-Liss, Inc.