Fig. 5. Ectopic Foxd3 suppresses interneuron differentiation in the spinal cord. (A-L) Cross-sections of neural tubes 48 hours after electroporation of Foxd3^Myc or Myc alone (I,L). Ectopic expression of Foxd3 (green) leads to the loss of Isl1/2-positive D2 interneurons (A,B), Lhx2/9-positive D1 interneurons (C) and Lhx1/5-positive D3 interneurons (D,E) in the neural tube. The arrowhead marks the Isl1/2-positive cells (B) and the Lhx2/9-positive cells (C) on the unelectroporated side of the neural tube and the arrow shows the loss of dorsal interneurons on the electroporated side. (F) Foxd3 expression also suppresses expression of Brn3.0 (red) in dorsal interneurons. A domain of Brn3.0-expressing cells is present in the dorsal spinal cord (arrow), but these cells do not co-express Foxd3. Foxd3-positive cells migrating from the dorsal spinal cord (arrowhead). (G,H) Ectopic Foxd3 suppresses Pax2-positive interneuron differentiation in the dorsal and intermediate spinal cord. Fewer Pax2-positive (H) cells are present on the electroporated side of the neural tube (arrow) and these cells are Foxd3-negative (G). (I) Control electroporation with a Myc expression vector, showing no reduction in Pax2-positive interneurons (red), many of which co-express Myc (yellow, arrow). (J,K) Ectopic Foxd3 suppresses Pax6 expression in interneuron precursors. (K) Fewer Pax6-positive precursors are present on the electroporated side of neural tube (arrow). (J) Foxd3-positive cells (green) do not express Pax6. (L) Electroporation of Myc does not reduce the Pax6 expression domain (arrow). fp; floor plate.

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