DEVELOPMENT Creating Birds of a Feather

Although feather development is known to depend upon reciprocal signaling between dermis and epidermis, the mechanisms that allow the feather patterns of a pigeon to differ from those of a peacock or a parakeet have been unclear. Eames and Schneider exploited the difference in embryonic origin of the dermis and epidermis of the head and neck by exchanging premigratory neural crest cells (destined to form dermis) between quail and duck embryos. The spatiotemporal patterning of feather bud appearance in the two species was distinct--for instance, quail feather placodes started as a medial and two lateral rows along the cranial epidermis, whereas duck feather placodes first appeared in rows over each eye--as were the size and spacing of the feather buds. Quail neural crest cells transplanted into duck accelerated feather development (consistent with the more rapid maturation of quail) and elicited feather buds with a quail-like pattern. The authors used in situ hybridization to investigate the timing of the expression of components and targets of the bone morphogenetic protein, sonic hedgehog, and delta-notch signaling pathways (bmp4, bmp2, follistatin, bmpr1a, shh, ptc, delta1, notch1) in these quail-duck chimeras and observed quail-like timing of gene expression in both quail-derived dermis and duck-derived epidermis. In contrast, duck neural crest delayed feather morphogenesis and the expression of signaling genes when transplanted into quail. The authors conclude that the plasticity with which host epidermis can respond to dermal instructions may promote the evolution of new patterns of feather development.

B. F. Eames, R. A. Schneider, Quail-duck chimeras reveal spatiotemporal plasticity in molecular and histogenic programs of cranial feather development. Development 132, 1499-1509 (2005). [Abstract] [Full Text]