In an article published in the August 24, 2001, issue of the journal Cell, Howard Hughes Medical Institute investigator Chris Q. Doe and colleagues at the University of Oregon reported that Drosophila neural precursor cells, called neuroblasts, sequentially activate four different transcription factors. Transcription factors are proteins that activate or repress the expression of genes.
This sequence of transcription factor activation allows the neuroblasts to give rise to a series of different daughter cells, which ultimately become neurons and glial cells in the fruit fly brain. The scientists found that the daughter cells continue to produce the particular transcription factor that was active in the neuroblast at the time of their birth a memory that allows neurons to maintain differences based on their time of birth. For example, first-born neurons always make the longest axon projections to distant targets, compared to later-born neurons from the same stem cell.
Before we started this work, it was known that each neuroblast makes many different types of neurons and glia, and that occurs in a particular order, said Doe. But the genes that control the fate of the cells in that sequence were not known. Also, it was not known whether there is one set of genes that works for all stem cells, or whether each of the many different types of stem cells in the fly has its own set of genes that work in some combination.
According to Doe, Drosophila is an ideal model for studying the order in which specific neural cells arise from stem cells b
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
23-Aug-2001