USC scientists uncover secrets of feather...( ff of which the feather's barbs branch;...)

ff of which the feather's barbs branch; each individual barb then branches again into the feather's smallest unit, the barbule, which is made of a single row of epithelial cells. Downy feathers, like those on a chick, lack a rachis altogether and are made up of just barbs studded with barbules. The standing hypothesis among many paleontologists has long been that the scales on dinosaurs must have lengthened into rachides that then became notched to form barbs and barbules. But there has been no real molecular evidence to either back up or refute that argument. Until now.

In their Nature paper, Chuong and his colleagues have demonstrated just how barbs and rachides are formed in a modern chicken, and have at the same time demonstrated that the evolution from scale to feather most likely followed a path in which the barbs form first and fuse to form a rachis-rather than a rachis forming first, and then being sculpted into barbs and barbules. This interaction between evolutionary biology and developmental biology (dubbed Evo-Devo) is a relatively new marriage of two previously disparate fields.

To come to their conclusions, Mingke Yu, the postdoctoral fellow and first author on the paper, along with colleagues Ping Wu and Randall B. Widelitz in Chuong's laboratory, developed a novel way to genetically manipulate different genes during feather formation. They plucked feathers from chickens, then prompted the chicken to regenerate those feathers under controlled conditions, raising and lowering the expression levels of the genes in question on an individual basis and observing the effects they had on the organization of epithelial cells into different feather forms.

Among others, three genes in particular-noggin, bone morphogenetic protein 4 (BMP4), and the whimsically named sonic hedgehog (Shh)-were found to result in new feathers that were rife with abnormal organization in their rachides and barbs. When Chuong's team increased the expression o
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Contact: Jon Weiner
jonweine@usc.edu
323-442-2830
University of Southern California
30-Oct-2002

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