The Embryonic Central Nervous System Lineages ofDrosophila melanogaster

Abstract

In Drosophila, central nervous system (CNS) formation starts with the delamination from the neuroectoderm of about 30 neuroblasts (NBs) per hemisegment. They give rise to approximately 350 neurons and 30 glial cells during embryonic development. Understanding the mechanisms leading to cell fate specification and differentiation in the CNS requires the identification of the NB lineages. The embryonic lineages derived from 17 NBs of the ventral part of the neuroectoderm have previously been described (Bossing et al., 1996). Here we present 13 lineages derived from the dorsal part of the neuroectoderm and we assign 12 of them to identified NBs. Together, the 13 lineages comprise approximately 120 neurons and 22 to 27 glial cells which we include in a systematic terminology. Therefore, NBs from the dorsal neuroectoderm produce about 90% of the glial cells in the embryonic ventral ganglion. Two of the NBs give rise to glial progeny exclusively (NB 6-4A, GP) and five to glia as well as neurons (NBs 1-3, 2-5, 5-6, 6-4T, 7-4). These seven NBs are arranged as a group in the most lateral region of the NB layer. The other lineages (NBs 2-4, 3-3, 3-5, 4-3, 4-4, 5-4, clone y) are composed exclusively of neurons (interneurons, motoneurons, or both). Additionally, it has been possible to link the lateral cluster of even-skipped expressing cells (EL) to the lineage of NB 3-3. Along with the previously described clones, the vast majority (more than 90%) of cell lineages in the embryonic ventral nerve cord (thorax, abdomen) are now known. Moreover, previously identified neurons and most glial cells are now linked to certain lineages and, thus, to particular NBs. This complete set of data provides a foundation for the interpretation of mutant phenotypes and for future investigations on cell fate specification and differentiation.

DrosophilaGlial Glutamate Transporter Eaat1 Is Regulated by Fringe-Mediated Notch Signaling and Is Essential for Larval Locomotion

“…Fng sensitizes the Notch receptor on the anterior LG to stimulation from developing axons bearing the Delta ligand and thereby promotes neuron-to-glial signaling during embryogenesis . Anterior and posterior LG are derived from a common glioblast (Schmidt et al, 1997;Beckervordersandforth et al, 2008), and so, as a consequence of this interplay between neurons and glia, Fng provides a mechanism for the selective expression of Eaat1 in the anterior LG subtype. Thus, Fng promotes the emergence of a functionally distinct glial cell subtype that can take up glutamate and has the potential to modulate neurotransmission at central synapses.…”

Insights into neural stem cell biology from flies

“…Glioblasts, on the other hand, produce pure glial lineages (Bossing et al 1996;Schmid et al 1997;Schmid et al 1999). In some neuroglioblast lineages, the bifurcation between the neuronal and the glial lineages occurs in the primary division to produce a neuronal and a glial precursor (figure 4a; Akiyama-Oda et al 1999; Bernardoni et al 1999).…”

“…In Drosophila, DiI lineage tracing studies have shown that embryonic neuroblasts produce near invariant lineages, usually containing distinct cell types (Bossing et al 1996;Schmid et al 1997Schmid et al , 1999. Furthermore, progeny are generated in an invariant birth order (Akiyama-Oda et al 1999;Novotny et al 2002;Pearson & Doe 2003).…”

Engrailed-like immunoreactivity in the embryonic ventral nerve cord of the Marbled Crayfish (Marmorkrebs)

“…In several representatives of this group of organisms all neuroblasts in the thoracic ganglia are individually identified concerning their position and the lineage which they generate and are well characterized on the molecular level (e.g. Doe 1992; Doe and Technau 1993;Broadus et al 1995;Bossing et al 1996;Schmidt et al 1997; see also the hyper neuroblast map at http://www.neuro.uoregon. edu/doelab/nbintro.html).…”