Next, we studied if IGF-1R is necessary for the early transition from multipolar to bipolar morphology. Animals were electroporated at E15 and observed at E17. At this time, previous studies have shown that most cells in the lower intermediate zone and SVZ are multipolar, whereas most cells in the upper intermediate zone and cortical plate are bipolar2–4, 19, 20. Consequently, these regions were named the multipolar migration zone (MMZ) and the radial migrating zone (RMZ), respectively21. Results showed that nearly80% of control cells located in the RMZ exhibited a bipolar morphology, as defined by the absence of more than two projections (Fig. 6a,b,c). In contrast, around 60% of the shRNA-IGF-1R electroporated cells found in the RMZ were arrested as multipolar cells. Co-electroporation of IGF-1R OPT and shRNA-IGF-1R rescued normal polarization of the electroporated cells (Fig. 6a,b,c).Figure 6IGF-1R stimulates polarity switch of migrating neurons. (a) shRNA-IGF-1R (center) decreases the proportion of bipolar cells in the radial migration zone (RMZ) at E17 compared to a control vector (left). Co-electroporation of shRNA-IGF-1R and IGF-1 OPT rescued normal polarization (right). (b) Cell morphologies of shRNA-IGF-1R and control cells are shown at higher magnification at the RMZ and multipolar marginal zone MMZ Calibration bar = 50 μm. (c) Quantification of in the morphologies of cells located in the RMZ from a. Student’s t test; ***p-value = 0.002. n = 3 independent experiments. An average of 100 cells was scored for each condition.