Time-lapse 2-photon imaging of the developing cerebral cortex

The theme of this dissertation project has been to look at the basic mechanisms of cerebral cortical development using the latest technological advances in time-lapse multiphoton imaging. In addition, I have looked at a genetic perturbation (reeler mouse) and its possible deleterious effects on the migration of interneurons during this developmental process.; The mode of neural stem cell division in the forebrain proliferative zones profoundly influences neocortical growth by regulating the number and diversity of neurons and glia. Long-term time-lapse multi-photon microscopy reveals new details of the complex three-dimensional rotation and oscillation of the mitotic spindle prior to stem cell division. Importantly, the duration and amplitude of spindle movement predicts and specifies the eventual mode of mitotic division.; The discovery that GABAergic interneurons from the ganglionic eminence migrate tangentially into the cerebral cortex has left open the question how these cells integrate into their areal and laminar position within the cortical plate. Here I use multi-photon videomicroscopy to map the migration of interneurons through the marginal zone. Imaging of both explant cultures and brains of living mouse embryos in utero revealed neuronal migration along a multi-directional "grid" on the surface of the brain which is reflected by the orientation of Cajal-Retzius cell processes. Three separate streams of GABAergic cells that emerge from different ventral positions populate this grid. After reaching an appropriate position, the migrating interneurons dive into the cortical plate to assume their laminar position. In reeler mutant mouse, these interneurons migrate properly across the surface of the cortex but their eventual laminar position is disrupted. These results indicate that GABAergic cells follow highly ordered routes of migration and that their areal specification and laminar integration are governed by dorsal neurons.