The vertebrate cortex is responsible for the high cognitive functions of the brain. It is organized into distinct layers of neurons and within each layer neurons share similar functions, morphology and birthdates1. This organization optimizes the processing of information and it requires the tightly regulated migration of neurons during development2. Most cortical pyramidal projecting neurons originate from asymmetric division of radial glia progenitors in the ventricular zone. They then migrate radially towards the marginal zone and through the subventricular zone (SVZ) and lower intermediate zone. This migration requires an intriguing intermediate step in the lower intermediate zone (IZ) where neurons transiently become multipolar and where they dynamically extend and retract multiple long projections and move in apparently random directions2–4. Subsequent to this stage polarity is necessary to define neuronal projections as dendrites or axons and axogenesis starts as cells approach the middle of the intermediate zone. After the axon emerges, the cells reorient their centrosomes and Golgi toward the pial surface, as they move to the upper part of the intermediate zone5. Their morphology then changes from multipolar to bipolar and they resume radial migration6. Bipolar cells have a thick, radially oriented leading process (the future principal dendrite) and a thin trailing axon, and move by locomotion plus somal or nuclear translocation along the radial glia processes2, 7, 8. Neuronal orientation and polarity are thought to be regulated by extracellular signals, providing instructive cues to migrating neurons9.