Regulation of Transcription Factors during Development
The development of a fertilized egg into a complex organism depends upon spatially regulated transcription. This process is
best understood in the fruit fly (Drosophila melanogaster) where dozens of genes controlling embryogenesis are known.
Many of these genes encode sequence specific transcription factors that bind to the promoters of other genes switching them
on or off. Our goal is to understand how these transcription factors are regulated during
embryogenesis.
In the Drosophila embryo, cell fate is determined by a system of positional information that allows each cell to sense its
coordinates within the organism. This information is provided by simple concentration gradients of substances called
morphogens. A cell determines its position with reference to any given coordinate axis by measuring the local concentration of a
morphogen that is graded with respect to that axis. Cells then use this positional information to initiate programs of gene
expression. We have found that one particular morphogen, called the dorsal protein, is a sequence specific transcription factor
that activates some genes and represses others. We hope to determine how this protein is able to carry out these opposing
functions.
The events that lead to the formation of morphogen gradients occur during oogenesis and result from interactions between the
oocyte and support cells in the ovary. In some cases, these interactions initiate protein phosphorylation cascades that result in
the localized activation of transcription factors. We are attempting to identify the transcription factor targeted by one such
system, the torso phosphorylation cascade. This factor is predicted to play a critical role in head and tail development.
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