Fig. 10. Increased abundance of neuroepithelium-derived cells in the E11.5 Cx43-PCKO embryo. (A) Wild-type E11.5 expression pattern of P3pro-Cre⁺:Cx43^+/+, EYFP-labeled cells (green signal) are limited to the neural tube, dorsal root ganglia (drg), peripheral nerves (pn), sympathetic ganglia (sg) and small circumscribed collections of labeled cells flanking the trachea (t) and esophagus. Sections in A-F are counterstained with propidium iodide to highlight the nuclei; overlap with EYFP appears as yellow signal. (B) Labeled cells flanking the trachea are shown migrating into the OFT of a control E11.5 embryo. (C) Section from an E11.5 Cx43-PCKO EYFP embryo at the level of the heart, showing an increased abundance of labeled cells outside of the neural tube in comparison with the control littermate. (D) Labeled cells are abundant in and around the tracheal region adjacent to the OFT in the Cx43-PCKO embryo at E11.5. (E,F) Labeled cells in sections from E11.5 Wnt1-Cre⁺ control (E) and Cx43-WCKO embryos (F) at the level of the heart share a similar distribution to that of P3pro-Cre⁺ controls, except in the neural tube where the Wnt1-Cre⁺ cells have a more limited distribution. (G) Radioactive in situ hybridization of E11.5 control embryos shows plexin A2 mRNA (pink) distributed in the neural tube (arrowhead) and in the OFT (arrow), as well as in paratracheal tissue adjacent to the OFT. (H) In contrast to the control embryos, Cx43-PCKO embryos express higher levels of plexin A2 (pink) in the neural tube (arrowhead), OFT (arrow) and paratracheal tissue, as well as elsewhere in the embryo. (I,J) Immunostaining for the presence of Pax3 (red) in control (I) and Cx43-PCKO (J) sections (indicated by arrows) at E11.5 reveals an unchanged expression pattern in the mutant embryos. (K) Cre recombinase expression (green) is absent in control embryos. (L) Cre expression is seen primarily at the dorsal aspect of the neural tube in Cx43-PCKO embryos at this stage (arrows). Arrowheads indicate the ventral boundary of the neural tube. Scale bar: 200 µm for A-F; 100 µm for G,H; 400 µm for I-L.