Axon specification is believed to involve asymmetric microtubule stabilization in one of the neurites of unpolarized neuron.However, how this polarized microtubule assembly is achieved during axon development is unclear.Here, we showthat extracellular matrix (ECM) component laminin promotes neuronal polarization via regulating directional microtubule assembly through betal integrin (Itgb1).Active Itgbl was found to be concentrated in distal axons of cultured hippocampal neurons on the laminin substrate.Down-regulating Itgb1 expression abolished axon formation, whereas enhancing Itgb1 signaling promoted axon development.