Change of laminin density stimulates axon branching via growth cone myosin II-mediated adhesion.

Axon branching enables neurons to contact with multiple targets and respond to their microenvironment. Owing to its importance in neuronal network formation, axon branching has been studied extensively during the past decades. The chemical properties of extracellular matrices have been proposed to regulate axonal development, but the effects of their density changes on axon branching are not well understood. Here, we demonstrate that both the sharp broadening of substrate geometry and the sharp change of laminin density stimulate axon branching by using microcontact printing (μCP) and microfluidic printing (μFP) techniques. We also found that the change of axon branching stimulated by laminin density depends on myosin II activity. The change of laminin density induces asymmetric extensions of filopodia on the growth cone, which is the precondition for axon branching. These previously unknown mechanisms of change of laminin density-stimulated axon branching may explain how the extracellular matrices regulate axon branching in vivo and facilitate the establishment of neuronal networks in vitro.