Dresden 2009 – scientific programme
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BP: Fachverband Biologische Physik
BP 13: Cell Migration
BP 13.8: Talk
Wednesday, March 25, 2009, 12:45–13:00, ZEU 260
Microtubule-based neuronal growth cone motility — •Thomas Fuhs1, Allen Ehrlicher1,2, and Josef Käs1 — 1Universität Leipzig, Soft matter physics, Leipzig, Germany — 2Harvard University, School of Engineering and Applied Sciences, Cambridge, USA
When creating a functional steering aparatus the individual nerve cells in the brain have to form synapses to pass on informations. Prior to the formation of a synapse the nerve cell has to find some other nerve cell to link to, therefore it sends out an exploratory growth cone. The growth cone is connected to the cell body with the microtubule rich axonal stump while on the front it consists mainly of actin, both as a dense network forming lamellipodia or thick actin bundles (filopodia).
This setup suggests an actin polymerization driven type of motility, as is it observed in fibroblasts. But in contrast to fibroblasts we obeserved inverse durotaxis, contradicting the models used for fibroblasts.
So we developed a theoretical model of how actin bundles steer a growth cone by mechanically stabilizing extending microtubules. Simple physics of anisotropic cytoskeleton elasticity and tube-model based ordering show how microtubules must align with stiff actin bundles, while unaligned one get buckled. Hence the side of the growth cone with fewer actin bundles dissipates more elastic energy in bent microtubules, resulting in a pressure pushing the growth cone in the opposite direction. This model also explains the inverse durotaxis, if more acto-myosin energy is dissipated into substrate deformation, less energy is available to deform the exploratory microtubules, resulting in an preferential extension towards softer materials.