Fig. 1.

Dorsal midline neural progenitor cells are Wnt responsive throughout spinal cord development. (A) Histologic X-gal stained sections of spinal cord from E10.5 Axin2-LacZ mice counterstained with Nuclear Fast Red. Arrow indicates Axin2-LacZ⁺ cells. (B) Histologic X-gal stained sections of spinal cord from E17.5 Axin2-LacZ mice counterstained with Nuclear Fast Red. Axin2-LacZ⁺ cells concentrate along the dorsal midline. Arrow indicates Axin2-LacZ⁺ cells. (C) The central canal of the spinal cord from E17.5 TCF/Lef:H2B-GFP. GFP⁺ cells concentrate along the dorsal midline. Dotted line outlines the central canal. Asterisk indicates the gap at the dorsalmost portion. (D) Cross-sectional image of Axin2^CreERT2/+; Rosa26^mTmG/+ spinal cord labeled at E8.5 and analyzed at E10.5. Axin2^CreERT2 marks dorsal midline neuroepithelial cells. Arrow indicates GFP⁺ neuroepithelial cells. Arrowheads indicate GFP⁺ neural crest cells. (E and F) Cross-sectional images of Axin2^CreERT2/+; Rosa26^mTmG/+ spinal cord labeled at E12.5 and analyzed at E14.5 (E), or labeled at E14.5 and analyzed at E16.5 (F). GFP⁺ radial glial cells span the entire dorsal midline. (G) Dorsal midline radial glial cells retain radial processes that span the entire length from the central canal to the dorsal pial surface and are labeled with GFP upon tamoxifen administration at E17.5. (H) GFP⁺ radial glial cells labeled at E17.5 and analyzed at P0 express Vimentin. (Scale bar, 50 µm.)