FIGURE 1.

Dilution of electroporated plasmid reduces expression level. (A) Bulk electroporation of the Xenopus optic tectum involves the injection of a plasmid solution into the tectal ventricle followed by passing current pulses across plate electrodes that span the targeted brain region. Transduction occurs on the side toward the positive electrode due to the negative charge of plasmid DNA. (B–E) Reducing the concentration of EGFP plasmid mainly lowers the levels of expression per cell. (C–E) Two-photon z-series projections through the optic tectum of an intact Xenopus tadpole collected using the same laser excitation intensity. (C) At 2 μg/μL a large number of bright cells, especially radial glial progenitors, are labeled. (D) 0.5 μg/μL or (E) 0.1 μg/μL labels fewer cells, which are also much fainter. Scale bar, 50 μm.