Neuroblast lineage identification and lineage-specific Hox gene action during postembryonic development of the subesophageal ganglion in the Drosophila central brain.

The central brain of Drosophila consists of the supraesophageal ganglion (SPG) and the subesophageal ganglion (SEG), both of which are generated by neural stem cell-like neuroblasts during embryonic and postembryonic development. Considerable information has been obtained on postembryonic development of the neuroblasts and their lineages in the SPG. In contrast, very little is known about neuroblasts, neural lineages, or any other aspect of the postembryonic development in the SEG.

The labial gene is required to terminate proliferation of identified neuroblasts in postembryonic development of the Drosophila brain.

The developing brain of Drosophila has become a useful model for studying the molecular genetic mechanisms that give rise to the complex neuronal arrays that characterize higher brains in other animals including mammals. Brain development in Drosophila begins during embryogenesis and continues during a subsequent postembryonic phase. During embryogenesis, the Hox gene labial is expressed in the developing tritocerebrum, and labial loss-of-function has been shown to be associated with a loss of regional neuronal identity and severe patterning defects in this part of the brain.

Hox genes and brain development in Drosophila.

Hox genes are prominently expressed in the developing brain and ventral ganglia of Drosophila. In the embryonic brain, the Hox genes labial and Deformed are essential for the establishment of regionalized neuronal identity; in their absence cells are generated in the brain but fail to acquire appropriate neuronal features. Genetic analyses reveal that Hox proteins are largely equivalent in their action in embryonic brain development and that their expression is under the control of cross-regulatory interactions among Hox genes that are similar to those found in embryogenesis of trunk segments.

Postembryonic development of transit amplifying neuroblast lineages in the Drosophila brain.

Background: Specific dorsomedial (DM) neuroblast lineages of the Drosophila brain amplify their proliferation through generation of transit amplifying intermediate progenitor cells. Together, these DM neuroblast lineages comprise over 5,000 adult-specific neural cells and thus represent a substantial part of the brain. However, no information is currently available about the structure or function of any of the neural cells in these DM lineages.

Lineage-specific cell death in postembryonic brain development of Drosophila.

The Drosophila central brain is composed of thousands of neurons that derive from approximately 100 neuroblasts per hemisphere. Functional circuits in the brain require precise neuronal wiring and tight control of neuronal numbers. How this accurate control of neuronal numbers is achieved during neural development is largely unclear.

Amplification of neural stem cell proliferation by intermediate progenitor cells in Drosophila brain development.

Background: In the mammalian brain, neural stem cells divide asymmetrically and often amplify the number of progeny they generate via symmetrically dividing intermediate progenitors. Here we investigate whether specific neural stem cell-like neuroblasts in the brain of Drosophila might also amplify neuronal proliferation by generating symmetrically dividing intermediate progenitors.

Results: Cell lineage-tracing and genetic marker analysis show that remarkably large neuroblast lineages exist in the dorsomedial larval brain of Drosophila.

Cell lineage-specific expression and function of the empty spiracles gene in adult brain development of Drosophila melanogaster.

The empty spiracles (ems) gene, encoding a homeodomain transcription factor, is a member of the cephalic gap gene family that acts in early specification of the anterior neuroectoderm in the embryonic brain of Drosophila. Here we show that ems is also expressed in the mature adult brain in the lineage-restricted clonal progeny of a single neuroblast in each brain hemisphere. These ems-expressing neuronal cells are located ventral to the antennal lobes and project a fascicle to the superior medial protocerebrum.

Polycomb group genes are required for neural stem cell survival in postembryonic neurogenesis of Drosophila.

Genes of the Polycomb group (PcG) are part of a cellular memory system that maintains appropriate inactive states of Hox gene expression in Drosophila. Here, we investigate the role of PcG genes in postembryonic development of the Drosophila CNS. We use mosaic-based MARCM techniques to analyze the role of these genes in the persistent larval neuroblasts and progeny of the central brain and thoracic ganglia.

The brain tumor gene negatively regulates neural progenitor cell proliferation in the larval central brain of Drosophila.

Brain development in Drosophila is characterized by two neurogenic periods, one during embryogenesis and a second during larval life. Although much is known about embryonic neurogenesis, little is known about the genetic control of postembryonic brain development. Here we use mosaic analysis with a repressible cell marker (MARCM) to study the role of the brain tumor (brat) gene in neural proliferation control and tumour suppression in postembryonic brain development of Drosophila.

The egghead gene is required for compartmentalization in Drosophila optic lobe development.

The correct targeting of photoreceptor neurons (R-cells) in the developing Drosophila visual system requires multiple guidance systems in the eye-brain complex as well as the precise organization of the target area. Here, we report that the egghead (egh) gene, encoding a glycosyltransferase, is required for a compartment boundary between lamina glia and lobula cortex, which is necessary for appropriate R1-R6 innervation of the lamina. In the absence of egh, R1-R6 axons form a disorganized lamina plexus and some R1-R6 axons project abnormally to the medulla instead of the lamina.

A pulse of the Drosophila Hox protein Abdominal-A schedules the end of neural proliferation via neuroblast apoptosis.

Postembryonic neuroblasts are stem cell-like precursors that generate most neurons of the adult Drosophila central nervous system (CNS). Their capacity to divide is modulated along the anterior-posterior body axis, but the mechanism underlying this is unclear. We use clonal analysis of identified precursors in the abdomen to show that neuron production stops because the cell death program is activated in the neuroblast while it is still engaged in the cell cycle.