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Chapter 18
Gene Regulation During
Development
7 and 9 November, 2004
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Overview
Differences in cell type are fundamentally differences in gene expression.
These expression differences are often monitored using microarray hybridization.
Differential gene expression is initiated by asymmetrical mRNA distribution, cellcell contact, or by diffusible signals.
Gradients of signaling molecules can give location information to cells.
Asymmetrically distributed mRNAs use the cytoskeleton for localization.
Drosophila embryogenesis is a well-understood system of animal development.
A morphogen gradient controls dorsal-ventral orientation in Drosophila.
Asymmetrically distributed mRNAs control anterior-posterior orientation and
ultimately segmentation.
Segmentation also depends on the interplay of regulators at the control regions of
genes.
Bioinformatics tools are useful in identifying genes that are developmentally
regulated.
Signaling Differentiation
Transducing
the Signal
Regualtion
in a
Morphogen
Gradient
Regulation by Asymmetrically Distributed mRNA
Regulation by Asymmetrically Distributed mRNA
Polar Cytoskeletal Elements
Regulation by Cell-cell contact in B. subtilis
Regulation by
Cell-cell
contact in
Animal
Development
Regulation by
Cell-cell
contact in
Animal
Development
Morphogen Gradient
Drosophila Development
Spätzle-Toll create a gradient of Dorsal in nuclei.
Transcriptional response to the Dorsal Gradient
Snail keeps rhomboid off in cells of the mesoderm.
Polar
Distribution of
bicoid and
oksar in
Drosophila
Embryos
Bicoid regulates orthodenticle and zygotic
hunchback.
Maternal hunchback mRNA is evenly distributed, but
translationally repressed by the posteriorly
concentrated nanos.
The hunchback gradient regulates gap genes as a
transcriptional repressor.
Gap genes
direct the
expression of
pair-rule genes.
Gap genes
direct the
expression
of pair-rule
genes.
Bioinformatics and the identification of
enhancers.
Competition and Quecnching in the eve
enhancer
Repression of eve-3 and eve-4 enhancers by
hunchback and knirps.
Enhancer autonomy requires short-range repression.
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