Understanding neuronal migration disorders using human tissue models

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The cerebral cortex is the seat of many of the higher cognitive functions that make us human, such as our advanced learning and speech. We know that the correct organisation of the cortex is vital for these functions, but how this is achieved during development remains elusive. Evidence from studies on neurodevelopmental disorders has indicated that neuronal migration is crucial to ensure that the right number of neurons end up in the right place at the right time. A key example of such a disorder is lissencephaly, where the folding of the cortex (the wrinkles on the outer surface) is greatly reduced. This lack of folding is associated with cognitive defects and has been suggested to be due to an over-migration of neurons.This project will use cutting-edge human cell and tissue culture systems to investigate how neuronal migration is dysregulated in neurodevelopmental disorders. It will take advantage of both laboratories' expertise, combining the Long lab's experience in human fetal neocortex development and explant models with the Berninger lab's experience in human induced pluripotent stem cells (iPSC) and organoid models. We will use a multidisciplinary approach, including live-imaging, transcriptome analysis, confocal-imaging and cell biology. Year 1 - Neuronal migration in human fetal neocortex explant models; establishment of human cerebral organoids from iPSCs In this first year, the student will learn the fetal tissue explant, iPSC and organoid culture systems. Endogenous (control) neuronal migration patterns will be established using lentiviral transfection and GFP labelled iPSCs. Towards the end of this year, they will also graft the iPSC derived neural progenitors/early neurons/glial cells into the fetal tissue explants. They will learn key cell/tissue culture techniques, microscopy (confocal and time-lapse), immunofluorescence and histology, as well as image analysis. Year 2 - Neuronal migration in iPSC/organoid and iPSC/explant models of neuronal migration disorders The student will use the techniques established in the first year, but with iPSCs from patients with neuronal migration disorders. We currently have several lines in use, including periventricular heterotopia, polymicrogyria and microcephaly. The migration defects of these cells will be compared to isogenic controls wherever available, or the next suitable control, as well as the endogenous cell behaviour observed in the first year. The migration will also be compared across the models used, 2D, organoids and fetal tissue explants. Year 3 - Identification of mechanisms underlying defects in neuronal migration; rescue of these defects in iPSC/organoid and human fetal neocortex models Using the data collected in year 2, the student will now study the mechanisms behind the neuronal migration defects observed and how these may be rescued in the different model systems. This rescue can be genetic (i.e. CRISPR, plasmid electroporation, viral transfection) or via pharmacological manipulation (i.e. small molecules, functional antibodies).