Fig. 4.

DNA electroporation demonstrates that splanchnic mesoderm harbors mesothelial progenitors. Sections through gut tubes of embryos electroporated at HH15-HH17 and incubated for 8 days. (A-D) GFP-positive cells (arrows) were identified within the squamous mesothelial layer of the intestine associated closely with the basement membrane (laminin, red). (E) GFP-positive cells were also identified within the forming α-smooth muscle actin (SMA)-positive muscularis externa (boxed region) and into the submucosa (arrowhead). (F-H) Higher magnification of the boxed region. GFP-positive cells within the muscularis externus were not SMA positive (arrows). ME, muscularis externa; Mu, mucosa; SM, submucosa.