Figure 1(A) Scheme of plasmid in utero electroporation. (B) Overview of electroporated neocortices showing Cas9 expression as revealed by PaprikaRFP fluorescence (magenta) and the effects of Cas9 expression, together with control gRNA (top) or gGFP (bottom), on GFP expression (green, fluorescence). Dotted lines indicate the electroporated area of the VZ. Single optical sections; scale bars, 200 μm. (C) Higher magnification of the VZ and SVZ of the electroporated area shown in (B), with DAPI staining (blue) depicted in addition to PaprikaRFP (Cas9) and GFP fluorescence. Boxes indicate areas shown at higher magnification in the insets (35 x 35 μm). Dotted lines indicate nuclei of progeny of electroporated aRGCs; note the presence of GFP fluorescence in the control (top) and its absence upon Cas9/gGFP electroporation (bottom). Images are single optical sections. Scale bars, 20 μm. (D) Quantification of the proportion of Cas9-positive cells in the VZ plus SVZ that are GFP-positive 48 h after control (Con, white) or gGFP (black) Cas9 plasmid electroporation. Data are the mean of 4 independent experiments (7 embryos per condition in total, from 4 litters). (E-H, J, K) Neocortex of mouse E13.5 Tis21::GFP embryos was in utero electroporated with recombinant Cas9 protein together with gRNAs targeting either LacZ (Control, Con) or GFP (gGFP) and with a pCAGGS-mCherry plasmid, followed by analysis at E15.5 (E-H) or E14.5 (J, K).(E) Scheme of Cas9/gRNA complex in utero electroporation. (F) Overview of electroporated areas of neocortices as revealed by mCherry fluorescence (magenta) showing the effects of Cas9 protein together with either control gRNA (top) or gGFP (bottom) on GFP expression (green, fluorescence). Dotted lines indicate the electroporated area of the VZ. Single optical sections; scale bars, 200 μm. (G) Higher magnification of the VZ and SVZ of the electroporated area shown in (F), with DAPI staining (blue) depicted in addition to mCherry and GFP fluorescence. Boxes indicate areas shown at higher magnification in the insets (35 x 35 μm). Dotted lines indicate nuclei of progeny of electroporated aRGCs; note the presence of GFP fluorescence in the control (top) and its absence upon Cas9/gGFP electroporation (bottom). Images are single optical sections. Scale bars, 20 μm. H) Quantification of the proportion of mCherry-positive cells in the VZ plus SVZ that are GFP-positive 48 h after control (Con, white) or gGFP (black) Cas9 protein electroporation. Data are the mean of 4 independent experiments (5 embryos per condition in total, from 4 litters). (I) VZ and SVZ of the electroporated areas showing Cas9 expression as revealed by PaprikaRFP fluorescence (magenta) and the effects of Cas9 expression, together with control gRNA (top) or gGFP (bottom), on GFP expression (green, fluorescence); blue, DAPI staining. Boxes indicate areas shown at higher magnification in the insets (35 x 35 μm). Dotted lines indicate nuclei of progeny of electroporated aRGCs; note the presence of GFP fluorescence in the control (top) and its absence upon Cas9/gGFP electroporation (bottom). Images are single optical sections. Scale bars, 20 μm. (J) VZ and SVZ of the electroporated areas showing targeted cells as revealed by mCherry fluorescence (magenta) and the effects of Cas9 protein together with either control gRNA (top) or gGFP (bottom) on GFP expression (green); blue, DAPI staining. Boxes indicate areas shown at higher magnification in the insets (35 x 35 μm). Dotted lines indicate nuclei of progeny of electroporated aRGCs; note the presence of GFP fluorescence in the control (top) and its absence upon Cas9/gGFP electroporation (bottom). Images are single optical sections. Scale bars, 20 μm. K) Quantification of the proportion of Cas9-positive cells (left) and mCherry-positive cells (right) in the VZ plus SVZ that are GFP-positive 24 h after control (Con, white) or gGFP (black) Cas9 plasmid (left) or protein (right) electroporation. Data are the mean of 3 independent experiments each (3 embryos per condition in total, from 3 litters).(D, H, K) Controls were set to 100% and the gGFP conditions expressed relative to control (D, 11%; H, 24%; K left, 40% K right, 28%). Error bars indicate SD; *, P<0.05; **, P<0.01; ***, P<0.001.