Early neurogenesis of theDrosophila brain

Abstract

We have studied the formation of the neuroblasts of the Drosophila brain which segregate from the procephalic neurectoderm. The expression domains of the segment polarity gene engrailed (en) allow one to subdivide the procephalic neuroectoderm into tritocerebral, deuterocerebral, and protocerebral neuromeres. Based upon the expression pattern of the proneural gene lethal of scute (l'sc), as well as the pattern of brain neuroblast segregation, the protocerebral and deuterocerebral neuromeres can be further subdivided into a central, anterior, and posterior domain. A total of 75-80 neuroblasts segregate in a stereotyped pattern from the procephalic neurectoderm of each side during stages 9-11. With respect to their position and the expression of the markers asense (ase) and seven-up (svp), 23 small groups of one to five neuroblasts each were identified. The first eight groups (Pc1-4, Dc1-3, Dp1), collectively called SI/II neuroblasts in analogy to the subpopulation of ventral neuroblasts which appear at the same stage), arise from the central domain of the protocerebral and deuterocerebral neurectoderm, respectively. Later groups form anteriorly and posteriorly from the earlier ones, leading to a centrifugal growth of the procephalic neuroblast population. SIII neuroblasts (Pa1-4, Pp1-2, Dp2) arise during stage 10, SIV neuroblasts (Pa5-6, Pp3-4, Da1, T1-2) during early stage 11, and SV neuroblasts (Pp5, Pdm) during late stage 11 and early stage 12. The dorsomedial domain of the procephalic neurectoderm represents a special case. Unlike other procephalic neuroblasts which delaminate from the surface ectoderm as individual cells, cells of the dorsomedial protocerebral domain are internalized during stage 12 as large, coherent clusters by a movement which can be best characterized as a combination of mass-delamination and invagination.

The neuroendocrine system of invertebrates: a developmental and evolutionary perspective

“…The PI/PL originate as placodes from the dorso-medial neuroectoderm of the head (Younossi- Hartenstein et al 1996, B De Velasco, T Erclik, D Shy, J Sclafani, HD Lipshitz, RR McInnes & V Hartenstein (unpublished observations) in a way that is similar to the formation of a few other structures of the nervous system of the head, including the optic lobe (Green et al 1993) and the stomatogastric nervous system . In all of these cases, shortly after gastrulation, small domains of the neuroectoderm adopt the shape of placodes ( Fig.…”

Cloning and characterization of the Drosophila homologue of the AP-2 transcription factor

“…The parts of the brain assigned to these head segments are called tritocerebrum (intercalary segment), deuterocerebrum (antennal segment), and protocerebrum (labral segment/acron or ocular segment; Figure 8). According to these assignments (Younossi-Hartenstein et al, 1996), DAP-2 is expressed in the region of the central/posterior protocerebral domain (compare with Figure 8a), which might include part of the region of the optic lobe placode because DAP-2 is expressed in the brain/optic lobe zone during later embryonic stages.…”

Differential Effects of Tau on the Integrity and Function of Neurons Essential for Learning in Drosophila

“…Clearly, presence of 0N4R ( Fig. 3D.1 Hartenstein et al, 1996;Noveen et al, 2000). Although Dac is not expressed only in the MB lineage, it is an excellent marker for this purpose because its stereotypical expression pattern is well mapped (Noveen et al, 2000), and it is clearly expressed in the neuroblasts that delaminate from the procephalic ectoderm (MBne).…”