Fig. 4. In ovo electroporation targets gene expression to the forelimb mesoderm. (A) The microinjection of plasmid DNA into the coelom (co) and electrode placement, dorsal (+) and ventral (–) to the embryo. (B) Confocal z-series stack (16 µm) from a vibratome section through a stage 23 embryo that was electroporated at forelimb levels with plasmid DNA encoding EGFP. Red, Pax7-positive muscle precursor cells; green, EGFP expression in limb mesodermal cells. ao, aorta; dm, dermomyotome; ec, ectoderm; no, notochord; nt, neural tube; som, somite; sop, somatopleure; spl, splanchnic mesoderm.