DOMAINS OF DIFFERENTIAL CELL-PROLIFERATION AND FORMATION OF AMNION FOLDS IN CHICK-EMBRYO ECTODERM

Patterns of cell proliferation in ectoderm epithelium that will form a vian amnion correlate with morphogenesis, but not in an obvious patter n with respect to large-scale folding. At sites where the pre-axial am nion folds will first appear in 4- to 8-somite embryos, patterns of pr oliferation do not separate into domains that presage location of the single pre-axial fold that is commonly described in embryology texts. Instead, increased cell proliferation occurs in a significant, bilater al pattern. In stages with 13 to 27 somites, when lateral amnionic fol ds are prominent, five paraxial domains of cell proliferation correlat e with morphology and show decreasing levels of cell proliferation wit h distance from the neural axis. Slowly growing areas surround rapidly growing areas and could assist buckling of epithelium by providing co nstraint on expansion of faster growing areas. Proliferation domains i n ectoderm correlate with morphology and morphological events when loc alized changes in cell shape are lacking and suggest a role for differ ential cell proliferation in formation of large-scale epithelial folds in early chick embryos. (C) 1994 Wiley-Liss, Inc.