Postembryonic neurogenesis in the optic lobe and central brain of Drosophila melanogaster
- Author(s): Ngo, Kathy T.
- Advisor(s): Hartenstein, Volker
- et al.
Neurogenesis or the proper formation of the nervous system requires three distinct phases: (1) early neurulation involving progenitor proliferation and specification; (2) progenitor migration and extension of fibers; and (3) neural differentiation and connectivity establishment. How connectivity is established remains to be poor understood. We investigated neurogenesis of the central brain and visual processing center in Drosophila. In Drosophila central nervous system (or central brain), there are 100 lineages, each derived from a single neuroblast; where neurons of one lineage remain in close proximity to their mother neuroblast. As described in the Appendix, we used cell type specific markers combined with global neuronal markers to serve as local landmark and mapped out how individual neuroblast lineages progress during development where gross anatomical changes are described. The fly optic lobe, the visual system processing center, is also highly modular. We show that early neurogenesis in the optic lobe is remarkably similar to vertebrates, following a “conveyor belt neurogenesis” (Ch. 4) and show that Jak/Stat and Notch negatively regulates epithelium-to-neuroblast conversion, a non-canonical mode of neurogenesis (Ch. 2). To further gain insights on how connectivity is established in the optic lobe, we reconstructed the global architecture and connectivity of the optic lobe at sequential stages of development. Our analysis reveals three major structural/developmental hallmarks by which the optic lobe, compared to other regions of the fly brain, stands out: large scale neuronal movements, correlated temporal gradients in neuron production and differentiation, highly ordered retinotopic projections in between visual neuropils, and the formation of multiple layers within these neuropils (Ch. 3). The works described in Ch. 2-5 and Appendix 1-3 serve an important platform for understanding how the nervous system is formed in Drosophila.