Feather Arrays Are Patterned by Interacting Signaling and Cell Density Waves

February 2019 in “ PLoS Biology ”

William Ho, Lucy Freem, Debiao Zhao, Kevin J. Painter, Thomas E. Woolley, Eamonn A. Gaffney, Michael J. McGrew, Athanasia C. Tzika, Michel C. Milinkovitch, Pascal Schneider, Armin Drusko, Franziska Matthäus, James D. Glover, Kirsty L. Wells, Jeanette A. Johansson, Megan G. Davey, Helen Sang, Michael Clinton, Denis J. Headon

fibroblast growth factor FGF bone morphogenetic protein BMP mesenchymal cell reaction-diffusion-taxis system FGF20 Ectodysplasin A EDA EDA/EDAR pathway

TLDR Feather patterns in birds are shaped by signaling interactions and cell movements, with EDA/EDAR crucial for pattern formation.

The study demonstrated that feather patterning in avian skin was governed by a coordinated system involving fibroblast growth factor (FGF) and bone morphogenetic protein (BMP) signaling, along with mesenchymal cell movement, forming a reaction-diffusion-taxis system. This system was mechanochemical, with FGF20 playing a central role in cell aggregation and epidermal compression, enhancing FGF20 expression. Feather formation was driven by a wave of Ectodysplasin A (EDA) expression, which spread across a mesenchymal cell density gradient, facilitating pattern formation. In flightless birds like emus and ostriches, this patterning was disrupted, with ostriches forming feather primordia without a wave, similar to mammalian hair follicle formation, and emus lacking sufficient cells for initial tract formation. The research highlighted the importance of the EDA/EDAR pathway in ordered pattern formation in flighted birds.