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Stability and nuclear dynamics of the bicoid morphogen gradient.

Authors
  • Gregor, Thomas
  • Wieschaus, Eric F
  • McGregor, Alistair P
  • Bialek, William
  • Tank, David W
Type
Published Article
Journal
Cell
Publisher
Elsevier
Publication Date
Jul 13, 2007
Volume
130
Issue
1
Pages
141–152
Identifiers
PMID: 17632061
Source
Medline
License
Unknown

Abstract

Patterning in multicellular organisms results from spatial gradients in morphogen concentration, but the dynamics of these gradients remain largely unexplored. We characterize, through in vivo optical imaging, the development and stability of the Bicoid morphogen gradient in Drosophila embryos that express a Bicoid-eGFP fusion protein. The gradient is established rapidly (approximately 1 hr after fertilization), with nuclear Bicoid concentration rising and falling during mitosis. Interphase levels result from a rapid equilibrium between Bicoid uptake and removal. Initial interphase concentration in nuclei in successive cycles is constant (+/-10%), demonstrating a form of gradient stability, but it subsequently decays by approximately 30%. Both direct photobleaching measurements and indirect estimates of Bicoid-eGFP diffusion constants (D < or = 1 microm(2)/s) provide a consistent picture of Bicoid transport on short ( approximately min) time scales but challenge traditional models of long-range gradient formation. A new model is presented emphasizing the possible role of nuclear dynamics in shaping and scaling the gradient.

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