| Summary: | <p>The subventricular zone (SVZ) of the mammalian brain serves as one of only two sources of adult born neurons. Adult born neural progenitors – known as neuroblasts – acquire the ability to migrate and travel large distances to their destination in the olfactory bulb. Disruption of neuroblast migration is associated with learning and memory deficiencies and, following injury, neuroblasts are re-routed to promote neurodegeneration. While a lot of research has attended to augmenting the production and survival of neuroblasts, the body of evidence for pharmacological targets or compounds that promote migration is comparatively sparse.</p> <p>This thesis set out to identify novel strategies to modulate neuroblast migration for brain repair by studying proteins known to modulate migration and identifying new ones through compound screening.</p> <p>Firstly, an explant migration assay from the mouse SVZ was used to investigate the potential to use growth factors to stimulate neuroblast migration. This confirmed that that insulin-like growth factor 1 (IGF1) and IGF2 regulate neuroblast migration, as previously reported by other research groups. The role of IGF2 is investigated further using a mouse model in which the binding of IGF2 to IGF2R is disrupted, resulting in increased proliferation in the embryonic cortical SVZ, brain overgrowth and perinatal lethality.</p> <p>In the second half of this thesis I try to tackle one of the major bottlenecks limiting the search in for pharmaceutical interventions targeting neuroblast recruitment: the lack of high-fidelity in vitro migration assays. Drawing concepts from existing in vitro migration assays and cerebral organoid models, I developed a novel neuroblast spheroid migration assays that permits the investigation of large numbers of interventions, concurrently, in 3 dimensions.</p> <p>Using the spheroid assay I successfully screened 1012 small molecule kinase inhibitors for their effects on neuroblast migration. Several compounds were identified that significantly increased or decreased neuroblast migration. Two genes: MUSK and PIK3CB were selected from the screen as putative biological targets and genetic knockdown of these genes validated that interruption of their activity increased neuroblast migration. In the future these compounds could be studied further to explore their potential for augmenting the recruitments of new neurons to sites of injury so support neuroregeneration, or for decreasing invasion of brain malignancies.</p>
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