Figure 3

Electroporation of stage 21–35/36 embryos leads to rapid expression of transgenes. a: Electroporation efficiency decreased with increasing embryonic stage. Percentages of nls-GFP positive cells 12 h after transfection at stage 26, 28 or 32 (n represents the number of sections analyzed from 3 embryos). Similar results were obtained at 48 h post electroporation (data not shown). b-d: Distribution of transfected cells depended on the stage of embryos electroporated. Distribution of nls-GFP transfected cells 48 h afterwards in embryos electroporated at stage 28 (b) and 32 (c). Note that the density of cells (DAPI) is lower laterally. d: Histograms showing decreases in the fraction of cells transfected in the superficial third of the brain when embryos were electroporated at stage 32 as compared to stage 28. e: A cluster of superficially located cells can be selectively transfected by injecting the DNA solution under the skin (the pia and epidermis are outlined in white). f-h: Time course of GFP expression in embryos electroporated at stage 29/30 (20 V/25 ms/1 s/8 x). The fractions as well as mean intensities of GFP positive cells were quantified (h) from sections (examples: f and g) (15 sections from 3 embryos were analyzed for the 6 h and 48 h time points and 39 sections from 3 embryos for the 24 h time-point). Differences between the time points were statistically significant using a Mann-Whitney test; probabilities are indicated together with the standard error (S.E.M). Outlines of the brains are presented (ventricle on the left). Scale bars: 100 μm in e; 50 μm in b, c, f and g.