Modeling the bicoid gradient: diffusion and reversible nuclear trapping of a stable protein. Author Mathieu Coppey, Alexander Berezhkovskii, Yoosik Kim, Alistair Boettiger, Stanislav Shvartsman Publication Year 2007 Type Journal Article Abstract The Bicoid gradient in the Drosophila embryo provided the first example of a morphogen gradient studied at the molecular level. The exponential shape of the Bicoid gradient had always been interpreted within the framework of the localized production, diffusion, and degradation model. We propose an alternative mechanism, which assumes no Bicoid degradation. The medium where the Bicoid gradient is formed and interpreted is very dynamic. Most notably, the number of nuclei changes over three orders of magnitude from fertilization, when Bicoid synthesis is initiated, to nuclear cycle 14 when most of the measurements were taken. We demonstrate that a model based on Bicoid diffusion and nucleocytoplasmic shuttling in the presence of the growing number of nuclei can account for most of the properties of the Bicoid concentration profile. Consistent with experimental observations, the Bicoid gradient in our model is established before nuclei migrate to the periphery of the embryo and remains stable during subsequent nuclear divisions. Keywords Animals, Drosophila, Models, Biological, Trans-Activators, Algorithms, Body Patterning, Cell Nucleus, Homeodomain Proteins, Cell Division Journal Dev Biol Volume 312 Issue 2 Pages 623-30 Date Published 12/2007 Alternate Journal Dev. Biol. Google ScholarBibTeXEndNote X3 XML