Molecular mechanism that regulates medially oriented axonal growth of upper layer neurons in cortical development

uring development layer 2/3 cells extend axons medially toward the ontralateral cortex. Here, we studied themechanism for axon outgrowth f layer 2/3 cells in cortical slice culture. To label these axons, a yellow uorescent protein-encoding plasmidwas introduced into the ventricular one cells by in utero electroporation when layer 2/3 cells are born. Within day after transfection, a cortical strip containing the labeled region was issected and cultured. After 3 days in vitro, most labeled cells were found o extend axons medially. This medially oriented growth was disrupted hen the lateral portion of the cortical slice was removed or when the lice was cut shorter along the mediolateral axis. These results indicate hat medially oriented growth of layer 2/3 cell axons was controlled by a epulsive molecule, which is localized laterally or distributed in a lateral igh-medial low gradient fashion in the cortex.