Exploring the Role of Nuclear Insulin Signalling in Drosophila Neural Stem Cell Reactivation

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This PhD project is focused on investigating whether a novel nuclear insulin signalling pathway is present in Drosophila neural stem cells (NSCs), and exploring whether it has a role in NSC reactivation. Drosophila NSCs generate the neurons and glia of the central nervous system during two waves of neurogenesis during development. Initially, embryonic NSCs divide to generate the larval nervous system. They then enter a reversible phase of mitotic dormancy, or quiescence, at the end of embryogenesis. In response to dietary amino acids when the larva feeds, the NSCs reactivate, resuming proliferation to generate the adult nervous system. Insulin signalling is both necessary and sufficient for NCS reactivation (Chell & Brand, 2010). The insulin signalling pathway has a central role in orchestrating growth, metabolism, and proliferation and, unsurprisingly, it is highly conserved across species. In human HepG2 hepatocellular carcinoma cells, and mouse primary hepatocytes, the insulin receptor (InR) was shown to enter the nucleus and associate with promoters, mediating gene expression (Hancock et al., 2019). This reveals a paradigm-shifting model in which, in parallel with canonical membrane-localised signal transduction, the InR directly effects gene expression by associating with chromatin. Given the role of insulin signalling in NSC reactivation, we are exploring this model in Drosophila. The core techniques I use in my research are Drosophila genetics; immunohistochemistry and confocal microscopy; Targeted DamID (Southall et al., 2013) chromatin profiling; bioinformatic analysis of sequencing data; and using the CRISPR/Cas9 system to generate genomic edits.