Light-Switchable proteins and adhesion micropatterns to illuminate the navigation machinery of neurons
Proper wiring and connectivity of the central and peripheral nervous system requires that during embryonic development neurons migrate and extend in the correct directions to connect to their targets. Defects in the neuronal navigation machinery lead to a variety of neurodevelopmental disorders such as Hirschsprung’s disease, Kallmann syndrome, ACC and has been associated with autism spectrum disorders and epilepsy. Neuronal navigation relies on a structure at the tips of neuronal extensions, termed the growth cone which is able to detect gradients of guidance molecules (chemotactants) secreted by cells at a distance. The chemotactant netrin, which binds multiple netrin receptors, can switch between attracting and repelling growth cones, a property which helps neurons change directionality upon reaching an intermediate target.	While it has been demonstrated that this is related to the complement of netrin receptors expressed by the neuron, it is unclear how different receptor combinations trigger opposing directional responses within the growth cone. It was recently shown that aberrant expression of netrin receptors in cells that don’t normally express it cause aberrant migration of neurons, which might explain some of the symptoms associated with neurodevelopmental disorders such as Mowat-Wilson syndrome. This proposal aims to understand at the molecular level how netrin can both attract and repel neuronal growth cones. This will be accomplished by mapping the interactome of both attractive and repulsive netrin-receptor complexes, and by mapping the spatial distribution and activity of proteins within actively steering growth cones, via high resolution microscopy, micropatterning and optogenetics to spatially modulate protein activities. This combinatorial approach will improve our understanding of neuronal guidance, associated disorders, and new technologies developed in this proposal might aid in the development of novel organ-on-chip technology.