PATTERN REGULATION AND PATTERN SPECIFICATION IN THE EMBRYONIC CHICK WING
Abstract
In an effort to determine the key factors involved in the processes of pattern regulation and pattern specification in the embryonic chick limb, the response of chick limb bud cells to experimental perturbations was studied. The results obtained are discussed in light of two contrasting models which have been formulated to describe pattern regulation and pattern specification: the ZPA/progress zone model which is based on long-range signalling via a diffusible morphogen and an autonomous cell counting mechanism, and the polar coordinate model which is based on local cell-cell interactions and cell proliferation. Experimental results discussed here indicate that there are three key factors involved in determining whether and what supernumerary limb structures will form following the juxtaposition of normally non-adjacent limb bud tissue. These factors are the position of origin of the donor tissue, the position grafted in the host, and the orientation of the graft in the host. All of these factors suggest that the response of chick limb bud cells to normally non-adjacent neighbors in a result of local cell interactions and cell proliferation. It is concluded that a model like the polar coordinate model best describes the experimental results obtained. A diagrammatic polar coordinate model description of many grafting operations performed with the embryonic chick wing is presented, as well as a polar coordinate model description of normal chick limb development.
Degree
Ph.D.
Subject Area
Biology
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