Axon Dynamics during Neocortical Laminar Innervation

The cerebral cortex is a densely interconnected structure with neural circuits that form between cortical laminae and also between distinct cortical areas. However, the precise cell biological and developmental mechanisms that underlie the formation of these neural circuits remain unknown. Here, we visualize laminar innervation of the developing mouse cerebral cortex by layer II/III pyramidal neurons in real time, describing cytoskeletal dynamics during this process. We find that layer II/III pyramidal neurons achieve local laminar-specific innervation through the stabilization of collateral axon branches in target laminae. We also find that loss of neural activity does not abolish local laminar-specific innervation and that cells within the local environment are the likely source of cues that direct layer-specific cortical innervation. [Display omitted] •Axons are highly dynamic during laminar innervation•Axon collateral branches are selectively stabilized in target laminae•F-actin pools are predictive of axonal protrusions•Neuronal activity is dispensable for local somatosensory cortex innervation The cerebral cortex is a laminated, highly interconnected structure. Hand et al. use live imaging to examine cell dynamics underlying initial laminar-specific innervation of the cerebral cortex by layer II/III pyramidal neurons. They find that axon collateral branches are selectively stabilized in target laminae.