In vivo imaging of cortical interneurons migrating in the intermediate/subventricular zones

• We visualized migrating neurons at a depth of the cortex in vivo.
• Stable and long-term observation of migrating cortical interneurons was performed.
• Interneurons headed straight toward midline extending poorly branched processes.

We developed an imaging system that enables migrating cortical interneurons (CIs) through the lower intermediate zone/subventricular zone (IZ/SVZ) in mouse embryos. CIs were labeled by in utero electroporation performed at embryonic day (E) 11.5 and were observed, through the skull of living embryos, detached from the dam with the umbilical cord remain attached. To identify imaged cell locations, we used GAD67-GFP mice and GFP fluorescence was photo-bleached after the recording. We found that CIs in the IZ/SVZ migrated medially straight toward the midline on the tangential plane, while those in the marginal zone migrated in all directions.