Morphological accounts of feather germ morphogenesis that described areas where cells were being "resorbed" or where layers "disintegrated" did not have the benefit of current immunocytochemical techniques to clarify processes associated with what could be seen. Ephemeral periderm is continuous with feather sheaths and is similarly incompletely described. It is reasonable to suspect that apoptosis (programmed cell death, PCD) removes cells as keratinization shapes barbs and barbules and as sheath and periderm are shed, so we used the TUNEL method (ApopTag®, Serologicals, Inc.) with DAB to mark PCD in White Leghorn chick embryo integument between 9 and 18 days of incubation. PCD marks frequently in pulp on days 12 and 13. Marginal and axial plates are removed by day 14, and by day 13, apoptotic nuclei are abundant in the distal tips in axial, marginal and barbule plates. PCD appears in a distal to proximal sequence along feather axes. Our results suggest that apoptosis is part of the formation of natal down barbs and barbules, is responsible for cavitation in pulp, and that PCD precedes shedding of periderm.
CR's Senior Thesis provided preliminary data for this study. A Sigma Xi Grant-in-Aid of Research to CR and a Hansmann Summer Research Fellowship (CC) supported this effort.
This study was presented as a poster at FASEB EB04.
FASEB Journal 18(4): A27 Abstract 67.6 2004
Christine Campbell, '04,
Christopher Reamer, '00, late feather germ and periderm