In utero electroporation were performed as described previously13 (link),40 (link) using Swiss mice (Janvier). Animal experimentations were performed at the IGBMC animal facilities. The study has the Animal Experimentation Research Ethics Committee approval (N° 2014-059). Briefly, timed pregnant mice (E14.5) were anaesthetized with isoflurane (2 l per min of oxygen, 4% isoflurane during sleep and 2% isoflurane during surgery operation; Minerve). The uterine horns were exposed and a lateral ventricle of each embryo was injected using pulled glass capillaries with Fast Green (2 μg/ml; Sigma) combined with a final concentration of 1µg/µl of DNA constructs prepared by EndoFree plasmid purification kit (Macherey Nagel). The expression vector pCAGGS-Tomato was systematically co-electroporated and the fluorescent Tomato protein was used to visualize electroporated cells. Plasmids were further electroporated into the neuronal progenitors adjacent to the ventricle by delivering five electric pulses at 50V for 50ms at 950ms intervals using a CUY21EDIT electroporator (Sonidel Ltd). After electroporation, embryos were placed back in the abdominal cavity and development was allowed to continue until E16, E18 or P2. Embryos or pups brains were dissected and fixed in 4% PFA in PBS overnight.