The Journal of Neuroscience, April 15, 2003, 23(8):3325
Role of DE-Cadherin in Neuroblast Proliferation, Neural
Morphogenesis, and Axon Tract Formation in Drosophila
Larval Brain Development
Karin
Dumstrei,
Fay
Wang, and
Volker
Hartenstein
Department of Molecular Cell and Developmental Biology, University
of California Los Angeles, Los Angeles, California 90095
In the wild-type brain, the Drosophila classic
cadherin DE-cadherin is expressed globally by postembryonic neuroblasts
and their lineages ("secondary lineages"), as well as glial cells. To address the role of DE-cadherin in the larval brain, we took advantage of the dominant-negative DE-cadex
construct, the expression of which was directed to neurons, glial cells, or both. Global expression of DE-cadex driven
by a heat pulse during the early second instar resulted in a severe
phenotype that included deficits in neural proliferation. Neuroblasts
appeared in approximately normal numbers but had highly reduced mitotic
activity. When the DE-cadex construct was driven by
the glial-specific driver gcm-Gal4, the effect of
DE-cadex on neuroblast proliferation could be
replicated, which indicates that DE-cadherin acts in glial cells to
promote proliferation of neuroblasts. Expression of
DE-cadex in neurons, cortex glia, or both results in
abnormalities in cortex layering and in trajectories of secondary
axons. In the wild-type brain, neuroblasts and neurons generated at
different time points are arranged concentrically around the neuropile, with the DE-cadherin-positive neuroblasts and young secondary neurons
at the surface, followed by older secondary neurons and primary
neurons. Axons of secondary lineages follow a straight radial course
toward the neuropile. Processes of glial cells located in the cortex
form a scaffold, called trophospongium, that enwraps neuroblasts and
neurons. Expression of DE-cadex in neurons, cortex
glia, or both disrupted the regular placement of neuroblasts and
secondary neurons and resulted in abnormal trajectories of cell body
fiber tracts. We conclude that DE-cadherin plays a pivotal role in
larval brain proliferation, brain cortex morphogenesis, and axon growth.
Key words:
DE-cadherin; larva; brain; neuroblast; morphogenesis; axon
Copyright © 2003 Society for Neuroscience 0270-6474/03/2383325-11$05.00/0
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