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Glia comprise a conspicuous population of non-neuronal cells in vertebrate and invertebrate nervous systems. Drosophila serves as a favorable model to elucidate basic principles of glial biology in vivo. The Drosophila neuropil glia (NPG), subdivided into astrocyte-like (ALG) and ensheathing glia (EG), extend reticular processes which associate with synapses and sheath-like processes which surround neuropil compartments, respectively. In this paper we characterize the development of NPG throughout fly brain development. We find that differentiated neuropil glia of the larval brain originate as a cluster of precursors derived from embryonic progenitors located in the basal brain. These precursors undergo a characteristic migration to spread over the neuropil surface while specifying/differentiating into primary ALG and EG. Embryonically-derived primary NPG are large cells which are few in number, and occupy relatively stereotyped positions around the larval neuropil surface. During metamorphosis, primary NPG undergo cell death. Neuropil glia of the adult (secondary NPG) are derived from type II lineages during the postembryonic phase of neurogliogenesis. These secondary NPG are much smaller in size but greater in number than primary NPG. Lineage tracing reveals that both NPG subtypes derive from intermediate neural progenitors of multipotent type II lineages. Taken together, this study reveals previously uncharacterized dynamics of NPG development and provides a framework for future studies utilizing Drosophila glia as a model.

Abstract: The tumor suppressor, vitamin D3 up-regulated protein 1 (VDUP1), regulates cell cycle progression by suppressing AP-1-dependent transcription. Loss of VDUP1 activity is associated with tumorigenesis but little is known about VDUP1 regulatory controls or developmental roles. Here we show that the Drosophila homolog of human VDUP1 (dVDUP1) is expressed throughout the nervous system at all stages of development, the first in vivo analysis of VDUP1 expression patterns in the brain. During neurogenesis dVDUP1 expression is transiently down-regulated coincident with neuroblast delamination. Subsequent to expression of the neuronal marker elav, dVDUP1 is up-regulated to varying degrees in developing neurons. In contrast, dVDUP1 expression is both robust and sustained during gliogenesis, and the cis-regulatory region of the dvdup1 gene contains consensus binding sites for the glial fate gene reversed polarity (repo). Expression of dVDUP1 in presumptive glia is lost in embryos deficient for the glial fate genes glial cells missing (gcm) and repo. Conversely, ectopic expression of gcm or repo was sufficient to induce dVDUP1 expression in the nervous system. Taken together, these data suggest a novel role for the dVDUP1 tumor suppressor during nervous system development as a regulatory target for REPO during gliogenesis. [Copyright &y& Elsevier]