Fig. 2. Formation of Cajal-Retzius cells and choroid plexus epithelial cells in the dorsal telencephalic midline. pEF-EGFP was introduced into the dorsal telencephalic midline at E9.5 by in utero microelectroporation, and the fate of EGFP⁺ cells was examined at the indicated time points. For the orientation of the planes, see Fig. 1A,A'. (A-F) At E10.5, all EGFP⁺ cells resided in the Msx1⁺ region (A-C). At E11.5, many EGFP⁺ cells migrated tangentially into the cortical neuroepitheium (D,E), and some of them had already reached the marginal zone of the piriform cortex (D,F). (G-Q) At E12.5, all cells that migrated laterally seemed to have reached the piriform cortex (G, arrow). Only two regions, the choroid plexus epithelium (the origin, asterisk) and the piriform cortex (the destination, arrow) were labeled with EGFP (G). The cells that remained at the origin expressed transthyretin (Ttr) (H,I,O,P) but not reelin (Q). The cells that migrated into the piriform cortex expressed Lhx5 (J,K, adjacent sections), Tuj1 (L,L') and reelin (M,M', arrowheads) but not calretinin (N,N'). di, diencephalon; tel, telencephalon. Scale bars: 150 µm in A,D; 500 µm in G; 50 µm in L-Q.