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First published online October 12, 2006
doi: 10.1242/10.1242/dev.02605
Institute of Genetics, University of Mainz, D-55099 Mainz, Germany.
* Authors for correspondence (e-mail: urbach{at}uni-mainz.de; technau{at}unimainz.de)
Accepted 31 August 2006
An initial step in the development of the Drosophila central nervous system is the delamination of a stereotype population of neural stem cells (neuroblasts, NBs) from the neuroectoderm. Expression of the columnar genes ventral nervous system defective (vnd), intermediate neuroblasts defective (ind) and muscle segment homeobox (msh) subdivides the truncal neuroectoderm (primordium of the ventral nerve cord) into a ventral, intermediate and dorsal longitudinal domain, and has been shown to play a key role in the formation and/or specification of corresponding NBs. In the procephalic neuroectoderm (pNE, primordium of the brain), expression of columnar genes is highly complex and dynamic, and their functions during brain development are still unknown. We have investigated the role of these genes (with special emphasis on the Nkx2-type homeobox gene vnd) in early embryonic development of the brain. We show at the level of individually identified cells that vnd controls the formation of ventral brain NBs and is required, and to some extent sufficient, for the specification of ventral and intermediate pNE and deriving NBs. However, we uncovered significant differences in the expression of and regulatory interactions between vnd, ind and msh among brain segments, and in comparison to the ventral nerve cord. Whereas in the trunk Vnd negatively regulates ind, Vnd does not repress ind (but does repress msh) in the ventral pNE and NBs. Instead, in the deutocerebral region, Vnd is required for the expression of ind. We also show that, in the anterior brain (protocerebrum), normal production of early glial cells is independent from msh and vnd, in contrast to the posterior brain (deuto- and tritocerebrum) and to the ventral nerve cord.
Key words: CNS, Brain, Neuroectoderm, Neuroblasts, Dorsoventral patterning, Cell fate, vnd, msh, ind, Glia, Drosophila
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S. G. Sprecher, R. Urbach, G. M. Technau, F. M. Rijli, H. Reichert, and F. Hirth The columnar gene vnd is required for tritocerebral neuromere formation during embryonic brain development of Drosophila Development, November 1, 2006; 133(21): 4331 - 4339. [Abstract] [Full Text] [PDF] |
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