In ovo electroporation and ex vivo imaging was performed as previously described by Spillane et al (2011) (link). Briefly, lumbosacral chicken embryo DRGs were electroporated in ovo at E3 using a CUY-21SC electroporator (Nepa Gene) equipped with 3 mm L-shaped gold tip electrodes (Harvard Apparatus). YFP-Drebrin E1 or GFP-control expression vectors were injected (0.1–0.15 μg/μl) into the lumen of the neural tube and electrodes were placed at the level of the lumbosacral enlargement. Five 50 ms 50 V pulses were applied at a rate of 1 pulse per second. Embryos were later removed from the eggs at E7 and the entire spinal cord, caudal to the first thoracic segment was dissected out. The cord was then divided into two halves and immediately placed on a video-imaging dish with 20 μl of culturing medium for imaging. Imaging was performed using a 100x objective on a Zeiss 200 m inverted microscope equipped with an Orca-ER camera (Hamamatsu).